BritBike Forum logo
BritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorThe Bonneville ShopBritBike Sponsor
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments.
Buy BritBike staff a coffee
Buy BritBike's staff a coffeeStill here since 1996 serving BritBike enthusiasts..
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Member Spotlight
63SuperRocket
63SuperRocket
Portland, ME
Posts: 68
Joined: September 2006
Show All Member Profiles 
Newest Members
Lucas Barwick, NTB31, B. Hunt, JM Ahumada, Michael nelson
10825 Registered Users
Top Posters(30 Days)
franko 139
NickL 78
DavidP 66
reverb 59
Popular Topics(Views)
972,644 mail-order LSR
a word from..
Forum Statistics
Forums34
Topics67,371
Posts677,269
Members10,825
Most Online14,755
May 5th, 2019
Who's Online Now
83 registered members (748kr), 559 guests, and 785 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 18 of 83 1 2 16 17 18 19 20 82 83
Re: 1928 Ariel Model C [Re: Magnetoman] #718907 12/15/17 8:46 pm
Joined: Feb 2008
Posts: 4,427
Tridentman Online Content
BritBike Forum member
Online Content
BritBike Forum member
Joined: Feb 2008
Posts: 4,427
Pity that--it would have made a Crete bike!
Incidentally--why the secrecy on the part of the organizers ref the route?

Support Your #1 BritBike Forum!

Check out British motorcycles for sale:
British Motorcycles on e-Bay UK
British motorcycles on e-Bay North America
Re: 1928 Ariel Model C [Re: Magnetoman] #718915 12/15/17 9:17 pm
Joined: Dec 2013
Posts: 4,713
kevin roberts Offline
DOPE
Offline
DOPE
Joined: Dec 2013
Posts: 4,713
i actually started to look up icarus motorcycles, then said, wait a minute . . .


every day you do not take a chance is a day of your life that you will never get back.
Re: 1928 Ariel Model C [Re: kevin roberts] #718920 12/15/17 9:30 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Restoration of the Icarus would have made for a story of mythological proportions if hopes for it hadn't been drowned.

I can only guess that the organizers might not as yet have locked in all the resort hotels and spas for us to stay in along the way so they want to keep the route, i.e. the daily stops, secret until they do. But, that's just a guess based on no information whatever.

Re: 1928 Ariel Model C [Re: Magnetoman] #718946 12/16/17 12:28 am
Joined: Sep 2007
Posts: 1,127
gREgg-K Online Content
BritBike Forum member
Online Content
BritBike Forum member
Joined: Sep 2007
Posts: 1,127
Originally Posted by Magnetoman
Restoration of the Icarus would have made for a story of mythological proportions if hopes for it hadn't been drowned.<SNIP>
.

Ah, waxing poetic ... if it doesn't work, you can always wing it ...

.. Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
[email protected]
Re: 1928 Ariel Model C [Re: Magnetoman] #718952 12/16/17 1:09 am
Joined: Aug 2001
Posts: 4,613
gavin eisler Offline
BritBike Forum member
Offline
BritBike Forum member
Joined: Aug 2001
Posts: 4,613
Read through the link to the Indian rebuild and run, Wow!, great stuff thanks for posting , you have got a better start , what a weird cam follower system that Indian had?3.5:1 CR and valves only 1/2 open, nice clutch though. The Ariel looks a far more modern machine in comparison. hats off to kevin for bringing back that power plus, it was pretty wrecked.
Keep on . One job at a time ( several in parallel). Interesting that he used the alloy pistons and ended up with a high balance factor, ran with it , only vibration induced failures seemed to be the exhaust manifold split

Last edited by gavin eisler; 12/16/17 1:22 am.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: 1928 Ariel Model C [Re: gREgg-K] #718954 12/16/17 1:09 am
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Originally Posted by gREgg-K
, you can always wing it ...
Although some entrants in past events seem to have attempted it on a wing and a prayer, I'm hoping a more grounded approach will keep me from being burned.

I've already heard back from the guy in the UK who is handling sales of the gearbox internals to confirm whether I want the "early" (no speedometer drive) or "late" (speedometer drive) set. Mine is the early type. Since this is a new item I can only hope there are no, ahem, teething problems with the gears. I hope to have the bike finished in plenty of time for tests, but even if it seems to work great I'll have the current set with me on the Cannonball as backup.

Re: 1928 Ariel Model C [Re: Magnetoman] #719132 12/17/17 6:44 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
I posted the following to the Ariel Owners Club, where there are a few more Black Ariel owners than here. Not a lot, mind you, but more than here. For completeness I'm posting it here as well since some of you may find the general procedure I used, if not the actual results, of interest.

As a reminder I wanted to determine the original balance factor used by the factory on my 1928 Ariel Model C so that I could rebalance the engine for one of the two new, +60 aftermarket pistons I've already purchased. My Ariel came with a worn +30 piston and with the small end rebushed to accept the 13/16" gudgeon pin of this newer-style piston rather than the 1" originally used. So, in addition to determining weights I had to correct for the weights of different bushes as well as for the socket head cap screws now locking the big end nuts in place. However, other than socket head cap screws used to lock the crankpin nuts, and the possible exception of four 5/16" holes discussed below, there are no other signs that the flywheels have been altered by additional drilling or plugging since they left the factory.

Since a search of the AOMCC web site shows the subject of balance factors has come up more than once, along with speculation on what value Ariel might have used, below I describe in some detail the measurements, uncertainties, calculations and assumptions leading to my determination so that others can decide for themselves if they want to accept the value I found. For those who don't want to read all of this, the executive summary is that the original balance factor used in my engine was either 56% or 60% (both +/-1%) depending on an assumption about four holes described below.

A seldom discussed but fundamental issue with the static balance method as usually described is it relies on the center of mass of the flywheels being on the axis defined by the crankpin and crankshaft. If an inhomogeneity in the flywheels places the center of mass off that axis then adding weight to the hanging connecting rod (which in effect places that weight at the center of the crankpin) will draw the center of mass close to the crankshaft axis but can never precisely balance the flywheels. To achieve perfect static balance requires applying weight to the connecting rod to draw the center of mass to its point of closest approach to the axis of the crankshaft, then adding (or subtracting) additional weight from the flywheels at 90-deg. from the crank-crankpin axis.

In all there are five 1/2"-dia. balancing holes drilled on the inside rims of the two flywheels. Because of the inaccessible location of these holes I speculate that the flywheels were balanced individually prior to being assembled into a complete crankshaft. There also are four 5/16"-dia. balancing holes drilled on the outside faces of the rims. There is no way to know if these were done by the factory at the time to tweak the crankshaft into the final balance factor after assembly, or if they were done during a later rebuild to keep the same balance factor for a heavier piston, or to change it to a higher balance factor. I address the quantitative effect of these possibilities on the calculated balance factor below.

In what follows I keep the precision of individual measurements (e.g. the 10 mg of one scale) although the final quoted uncertainty largely depends on the least sensitive measurement used in the calculation. I used the following tools:

200 g balance calibrated with weights accurate to 0.3 mg. Balance reads to +/-10 mg.
6 kg balance calibrated with weights accurate to 0.1 g. Balance reads to +/-0.5 g.
6-piece set of 5-50 g balance weights each accurate to 0.01 g.
Crown-brand balancing wheels of sensitivity 1 g-cm, equivalent to 0.2 g imbalance at the radius of the crankpin.
Digital calipers.

The four "external" 5/16" holes are at the crankpin end of the crankpin/crankshaft axis and have a total depth of 3.86" resulting in a volume of steel removed of 0.296 in.3. Using 0.29 lbs./in.3 for the density of steel, the total weight removed from these four holes was 0.086 lbs. (38.9 grams)

A formula for calculating the Balance Factor can be written in the form:

Balance Factor = (balance weight + small end weight) / (piston weight + small end weight)

As can be seen, to solve this requires determining three weights as well as having a fixture for holding the crankshaft so it can rotate freely when the balance weights are added.

Small end weight:
With the bushing to reduce it for a smaller gudgeon pin it weighs 267.5 +/-1 g. However, from this subtract 7.4 g for the "excess" weight of the bronze (see 'sidebar' below for details) so it originally would have weighed 260.0 +/-2 g.
-- Current small end weight = 267.5 +/-1 g
-- Original small end weight = 260.0 +/-1 g

Piston weight:
The "piston weight" is that of the complete assembly of piston, gudgeon pin, circlips and rings. Although it doesn't enter into the calculations shown here I'll note that the weight of the additional Al used in a, say, +30 piston is not negligible. It can be calculated from the annular volume of a piston of stock diameter and one 0.03" larger than that.

-- weight of +30 piston assembly that was currently in my bike 467.5 +/-0.5g

I was lucky to find two people with original piston assemblies for the Ariel. The one in Australia is used and weighs 507.2 g and the one in Canada is new and weighs 503.5 g.

-- weight of original piston assembly weight (average of above) = 505 +/-2 g
-- weight of aftermarket +60 Gandini piston assembly 516.5 +/-0.5 g
-- weight of aftermarket +60 Omega piston assembly 435.0 +/-0.5 g


Balance weight:
I hung balance weights and washers from a wire attached to the small end until the crankshaft was in balance and weighed the final total mass. It took 196.59 g plus 10 g on the rim at 90o. Taking into account the off-axis imbalance I estimate the uncertainty in balancing the crank using only weights hanging from the connecting rod and none at 90o is +/-3 g.

The weight of the heads of the two 1/4" cap screws pinning the big end is 2 x 2.74 grams = 5.48 g. Without the cap screws it would have required that much additional weight to balance the crank originally, offset somewhat by the 7.4 g "excess" of the current bronze reducing bushing, i.e. 196.6 + 5.5 - 7.4 = 194.7 grams.

-- weight to originally balance crankshaft = 195 +/-3 g

If the 5/16" holes were added sometime later the original weight required to balance it would have been 38.9 grams less.

-- weight to balance crankshaft without the four 5/16" holes =165 +/-3 g
-- total weight to balance crankshaft in its current form = 196.6 +/-0.1 g

Original factory balance factor:

If the crankshaft in its current form (less the cap screws) is how it left the factory, the original balance factor was:

294.7 + 260.0 / 505.0 + 260.0 = 455 / 765 = 60.2 +/-1%

If the four 5/16" holes were added later it would have required 38.9 grams less to balance it originally. In this case the original balance factor would have been

165 + 260 / 505 + 260 = 425 / 765 = 55.6 +/-1%

For comparison, a 1960 BSA Service Bulletin shows 60% for the 250cc 'C' series, 58% for Gold Stars, 55% for the essentially identical 'B' series singles in the same frame as the Gold Star, and 55% for both the 500cc and 650cc 'A' series twins, also in the same frame as the Gold Star. A 1930s Vincent Comet used 66% (claimed weight 390 lbs. vs. 290 for the Ariel) but this had to be reduced to 61% in a lightweight speedway frame.

Current Balance Factor:

With current piston in it:
196.6 + 267.5 / 467.5 + 267.5 = 464.1 / 735 = 63.1% +/-0.3%

With Gandini piston in it:
196.6 + 267.5 / 516.5 + 267.5 = 464.1 / 784 = 59.2 +/-0.3%

With Omega piston in it:
196.6 + 267.5 / 435.0 + 267.5 = 464.1 / 702.5 = 66.1 +/-0.3%

To reduce the balance factor to 60% in order to use the Omega piston in it would require reducing the required balance weight by 43 g which in turn would mean removing roughly half that weight from the rim of the flywheel. This could be achieved by, for example, drilling two additional 5/16" holes approx. 1" deep each.

If the Omega offered a significant advantage over the Gandini I would modify the crankshaft accordingly. However, since the Gandini piston could be used with the crankshaft as-is, I'm particularly interested in any experiences people have with these aftermarket pistons.

--------------------
Sidebar: The difference in weight of the bronze in an original 1" ID bushing and the current 13/16" reducing bushing in the small end:

Density of steel = 7.75-8.05 gram/cm3
Density of bronze = 8.7 grams/cm3
Width of connecting rod = 0.87"
Width of current reducing bush = 1.065" (tapered)
OD of bush = 1.1875"
ID of original bush = 1.000"
ID of current bush = 0.8125"
From this, the excess weight of the small end over that with the stock bush = 7.4 g
---------------------

Re: 1928 Ariel Model C [Re: Magnetoman] #719169 12/17/17 10:46 pm
Joined: Oct 2017
Posts: 247
G
George Kaplan Offline
BritBike Forum member
Offline
BritBike Forum member
G
Joined: Oct 2017
Posts: 247
Hi MM, this is very interesting stuff indeed. I will be following how this develops because I am both interested in your progress on your Ariel both now in the preparation stage and also when you take it across country. I am a firm believer in meticulous preparation being the key to a successful outcome in the Cannonball and I am hoping that you willprove this to be true.

I am also interested because I am currently pondering the building a balancing rig of my own (and your input to my questions on my option is very much appreciated).

John

Re: 1928 Ariel Model C [Re: Magnetoman] #719224 12/18/17 1:06 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Offline someone asked about the source of the equation I used for the balance factor. It, and the percentages I quoted for various BSAs, comes from BSA Parts and Service Bulletin No. 51, dated 1 October 1960.

The balance factor is the fraction of the ratio of reciprocating weight to rotating weight that is to be balanced, e.g. 60%. If the crankshaft is apart the rod is suspended horizontally and the little and big ends weighed separately (the sum needs to be the total weight or you've made a mistake). The weight of the little end, along with the piston assembly, is assumed to be reciprocating weight and that of the big end is part of the rotating weight.

Phil Irving describes in words the same equation as in BSA's Service Bulletin in a section entitled "Balancing a Complete Assembly" in a chapter on "Truing and Balancing Flywheels" in 'Tuning for Speed'. He also describes how if the crankshaft is together, and if it has a roller bearing (so friction is small), the little end can be weighed by rotating the crankshaft until the rod is horizontal. This is how I weighed the little end of my engine. The weight of the big end is "automatically" included by the procedure for balancing the crankshaft.

Further on the subject of balance factors, in the same book Irving writes:

"There are in fact so many considerations involved that it is impossible to quote one figure as being ideal, since it varies with every type of engine, and even for the same engine in differently-equipped frames. The only source of reliable information is the parent factory who have certainly done a lot of experimentation. The M.O.V. Velocette factor is as high as 85 per cent, while some engines have been under 50 per cent, but failing any reliable information 66 per cent is a good starting-off point."

It takes a lot of time to accurately balance a crankshaft so if I were rebuilding a stock engine using OEM components I probably wouldn't have bothered (then again, I have the equipment and the inclination for making such measurements, so...). But, the previous rebuilder of my engine bodged enough things that I didn't feel I could trust what he had done. For example, I certainly wouldn't have purchased a new Alpha crankpin to have on hand and be taking the crank apart if I trusted the previous work. Further, the two aftermarket pistons are significantly different in weight so even without making any measurements on the crankshaft I knew they would result in significantly different balance factors (59% and 66%, as it turned out). Now knowing that the original balance factor was ~60%, and since the Ariel is in the same stock configuration as when sold, it means that if it vibrates itself apart at 60% I can curse Val Page for his design and testing, not myself for having simply slapped one of the aftermarket pistons in and hoped for the best.

Returning to my measurements, earlier I mentioned that metal had been drilled from one flywheel at 90o, indicating that there was an inhomogeneity in the casting causing an off-axis imbalance. Another hole is drilled at 135o, indicating that someone didn't quite know what he was doing (balancing holes should be orthogonal to each other). I had to add a 10 g weight at 90o to get the flywheel to balance. Since I've come this far I will be drilling a shallow hole to eliminate that slight off-axis imbalance. This probably will involve a couple of iterations of drilling, rebalancing, drilling again,...

Re: 1928 Ariel Model C [Re: Magnetoman] #719295 12/18/17 9:10 pm
Joined: Nov 2012
Posts: 1,112
K
koan58 Offline
BritBike Forum member
Offline
BritBike Forum member
K
Joined: Nov 2012
Posts: 1,112
Hi Mr M, I am following your journey with fascination, and what your accounts inspire me to investigate some subjects more deeply. I am well versed in science, but I haven't given full depth of thought to this matter till you presented it in such interesting terms. Thanks!

"A seldom discussed but fundamental issue with the static balance method as usually described is it relies on the center of mass of the flywheels being on the axis defined by the crankpin and crankshaft. If an inhomogeneity in the flywheels places the center of mass off that axis then adding weight to the hanging connecting rod (which in effect places that weight at the center of the crankpin) will draw the center of mass close to the crankshaft axis but can never precisely balance the flywheels. To achieve perfect static balance requires applying weight to the connecting rod to draw the center of mass to its point of closest approach to the axis of the crankshaft, then adding (or subtracting) additional weight from the flywheels at 90-deg. from the crank-crankpin axis."

I don't understand the above bit. Say you were aiming for 50% (or any factor), you would hang a weight off the big end journal of a mass of your rod big end mass plus 50% of the piston + small end mass.
A flywheel, or balance weight, is not meant to be balanced, not in a simple spinning sense anyway. How will you balance the flywheels? Dave

Re: 1928 Ariel Model C [Re: Magnetoman] #719304 12/18/17 10:17 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Originally Posted by koan58
I don't understand the above bit. Say you were aiming for 50% (or any factor), you would hang a weight off the big end journal of a mass of your rod big end mass plus 50% of the piston + small end mass.
I agree that if you separately weighed both ends of a rod and used those values in a slightly different version of the equation you could achieve whatever balance factor you wanted.

But, you also can do it the way I described. Even though I don't know the mass of the big end of the rod (because the crank is still assembled) its mass is attached to the crankpin so is automatically taken care of when I hang additional mass off the small end to balance the crankshaft. The only difference between the two ways of doing it, disassembled vs. assembled, is I probably could determine the small end weight a little more accurately if I had the rod separate from the crankshaft rather than still attached.

I'm not sure I understand what you wrote below:
Originally Posted by koan58
A flywheel, or balance weight, is not meant to be balanced, not in a simple spinning sense anyway. How will you balance the flywheels?
A flywheel definitely can be balanced in the simple spinning sense. That is, weights of the correct mass can be attached in the correct location on the crankshaft/crankpin axis (and, if necessary, 90o to that axis) such that when you spin that flywheel there will be no vibration. This is exactly what I did when I hung weights off the little end of the connecting rod. If instead of having those weights attached to the rod, which would flop around if I tried to spin the crankshaft, I removed the rod and welded to the crankpin its full weight plus the weight hanging from the small end, the crankshaft could be spun without vibration.

Did what I wrote above answer your question? If not, please rephrase it.

Re: 1928 Ariel Model C [Re: Magnetoman] #719400 12/19/17 6:05 pm
Joined: Nov 2012
Posts: 1,112
K
koan58 Offline
BritBike Forum member
Offline
BritBike Forum member
K
Joined: Nov 2012
Posts: 1,112
Thanks MM for your patience! I think some my my difficulty stems from terminology so leading to talking at cross-purposes.

I had trouble understanding "it relies on the center of mass of the flywheels being on the axis defined by the crankpin and crankshaft". Having mulled over it, I think you are referring to the plane thus defined. Yes? I can see how inhomogeneity (ie a difference in mass distribution of the flywheels either side of the above plane) would shift the flywheel's centre of mass off that plane.

If I may posit an imaginary, but possible scenario as illustration:

Left flywheel's inhomogeneity results in its center of mass being X" forward of the plane at TDC.


Right flywheel's inhomogeneity results in its center of mass being X" rearward of the plane at TDC.

Assuming the flywheels are of equal mass, in the static balancing process, the crankshaft overall centre of mass will be on the plane, but may result in a significant rocking couple in use.
Without individually balancing the flywheels with respect to the plane, there could be any combination of fore and aft imbalances with a net crankshaft imbalance which can be corrected by adding 10g to either flywheel. Depending on your luck, the 10g may reduce or increase any rocking couple already present.

This is what I meant by "how will you balance the flywheels?". I meant each one individually, not as a crank assembly, and is also what I meant by "A flywheel, or balance weight, is not meant to be balanced, not in a simple spinning sense anyway".

With the kit at your disposal, your fastidious approach, and that you will be parting the crank assembly, I imagined that you would be doing this somehow.
I don't know if you can use your kit to do this with individual flywheels, hence my question "How will you balance the flywheels?".

Another thought, knowing how accurately you like to do things (most admirable and why I find your posts interesting), when you are making allowances for holes in the flywheels, heads of bolts etc, doesn't the effect of these masses have to be adjusted according to their distance from the crank axis?
For example, the balancing weights act at the centre of the crankpin (half the stroke from the crank axis), holes on the periphery of the flywheels are further away and will have a greater impact.

Finally, a little curiosity. The holes in the flywheels drilled inside the rims, are they drilled from the crank axis outwards (ie radial) or in line with the axis?
Either way, I can't see why they would choose to do it there, and if it is the radial style it just occurs to me that in use they would be filled with oil, and over time act like sludge traps. Of little consequence, but odd? Dave

Re: 1928 Ariel Model C [Re: Magnetoman] #719420 12/19/17 9:31 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Originally Posted by koan58
Assuming the flywheels are of equal mass, in the static balancing process, the crankshaft overall centre of mass will be on the plane, but may result in a significant rocking couple in use.
Making a long story short, yes, there certainly could be a rocking couple in a single. However, in a practical sense it's a matter of how big it could be. In the case of a twin the crankpins and the reciprocating masses are 3-1/2" apart (pre-unit Triumph), while for my Ariel the crankpin and reciprocating mass are on the centerline and the flywheels are at only 1-3/4" from it.

One or both flywheels might not be perfectly homogeneous from side-to-side and only dynamic balancing would detect that if it were the case. However, the maximum amount of such inhomogeneity in the steel is so limited, and the flywheels are so narrow, that the rocking couple it could produce would be pretty small.

While I could have each flywheel dynamically balanced, the vibration from any rocking couple would be so much smaller than the vibration that is going to come from the 60% balance factor that it wouldn't worth the effort to eliminate it.

Originally Posted by koan58
I don't know if you can use your kit to do this with individual flywheels, hence my question "How will you balance the flywheels?"
Once I have the flywheels apart I'll make a shaft and a weight of exactly half that of the crankpin + rod + piston assembly + balancing weight. With this I will be able to individually balance each wheel. I'm not so concerned with getting to, say, 60% vs. 58% but rather in getting rid of the problematic imbalance at 90o. The latter only causes vibration without doing anything to balance the engine. Unlike the case of the possible small rocking couple, ~10 g spinning at 3000 rpm generates significant vibration.

Originally Posted by koan58
when you are making allowances for holes in the flywheels, heads of bolts etc, doesn't the effect of these masses have to be adjusted according to their distance from the crank axis?
Most certainly yes. For example, the cap screws locking the crankpin nuts are at the same distance from the crank as the crankpin and big end so every gram they weigh is one less gram I don't hang from the small end. If, instead, these screws were at the rim every gram would be equivalent to ~2 grams at the crankpin.

Originally Posted by koan58
The holes in the flywheels ... in line with the axis?
They're in line with the axis.

Re: 1928 Ariel Model C [Re: Magnetoman] #719523 12/20/17 8:57 pm
Joined: Nov 2012
Posts: 1,112
K
koan58 Offline
BritBike Forum member
Offline
BritBike Forum member
K
Joined: Nov 2012
Posts: 1,112
Thanks MM for that, do please tell me if you find my questions and thoughts an annoying distraction.

I fully agree that the relatively compact crank assembly will considerably reduce the significance of any rocking couple. However, I think you may be overlooking the opportunity you have to do your best about it, at the same time as you are doing what you intend anyway.

You are quite right to say that only dynamic balancing would allow correction of the rocking couple of a crankshaft assembly, complete. For instance, I could only get my 1-piece triumph twin crank done by using the services of a specialist with the sophisticated equipment that spins the crank and records the cycles of loadings at both ends. This is because the individual contributions of the counterweights either side could not be isolated any other way.

In your case, you will split the crank, and will be individually dealing with each flywheel, using half the total balance weight, such that you will achieve an equal balance contribution from each wheel, and correcting for any orthogonal imbalance at the same time.
To me, you are 3 parts of the way to dynamic balancing.

You will have moved their centres of masses to the plane defined by the crank and big end axes. You will also have moved their centres of masses to the same radial points on that plane. The only remaining factor that could cause a rocking couple is a difference between the masses of the flywheels. So if the centres of mass and the actual mass of the wheels are the same, that is dynamic balance.

I assume that the flywheels are pretty much similar, however we know that their mass distribution is not perfect, so it is also quite likely that their masses are different. It only remains to establish the masses of the wheels, then you can equalise them at the same time as putting their mass centres in the same place.

Of course, ascertaining the masses of the flywheels is not simple, as they have different shafts attached to them. I would start by weighing each flywheel unit. Then make an allowance for the shaft weight.
If those shafts are simple, an allowance could be calculated based on dimensions/density. Alternatively, Archimedes could be used. If the wheels come out fairly close, it's probably not worth fussing about.

A couple of separate thoughts:

"If the four 5/16" holes were added later it would have required 38.9 grams less", I couldn't see where and how this was applied in the calculations?

I think the calculation of the mass difference between small end bushes may need revisiting.

The difference in X-area between the bushes is 3.799 (current) - 2.077 (original) = 1.722 cm2

A length 2.21cm (width of conrod) of this difference produces 3.806 cm3, X 8.7 g/cm3 (density of bronze) = 33.109g

If the length of the current bush is longer (2.705 cm) than the original (2.210 cm?) this discrepancy is even larger (approaching 50g)

You only have to visualise how small 7.4g of bronze is (less than 1cm3) to see something is amiss.

Only playing devil's advocate! Dave

Re: 1928 Ariel Model C [Re: Magnetoman] #719530 12/20/17 9:47 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Originally Posted by koan58
To me, you are 3 parts of the way to dynamic balancing.
The weights of the webs and reciprocating weights of the crankpins, and the separation between them, of a twin make that situation significantly different than that of a single. Sometimes the pursuit of perfection gets in the way of achieving more-than-good-enough. I think dynamic balancing of the individual flywheels of a single is one of those times.

Originally Posted by koan58
If the four 5/16" holes were added later it would have required 38.9 grams less", I couldn't see where and how this was applied in the calculations?
I'll double-check my calculations later to see if I made a mistake in either the calculation or in retyping it for my post.

Originally Posted by koan58
I think the calculation of the mass difference between small end bushes may need revisiting.
I didn't give the details, but the present bush isn't simply a hollow cylinder. It has the dia. of the little end through the cross section of the connecting rod, then tapers to a smaller OD out to nearly the open space inside a piston. But, I'll double-check those calculations later as well.


The Ariel manual calls for the crankshaft spindles to run "dead true," and various sources say to aim for no more total indicated runout (TIR) than 0.001", so before disassembling it I wanted to know how close to dead my crankshaft currently is. It turns out to be much too alive for its own good, yet again justifying my complete rebuild of the bike.

With the crank between centers, the total TIR is 0.006" on the drive side spindle measured next to the flywheel, 2.9" from the closest center, and 0.003" at 0.5" from the center, consistent with the center at that end being, ahem, drilled off-center by ~0.001" (for a TIR of ~0.002"). The same measurements on the timing side are 0.008" at the flywheel, 2.4" from the closest center, and 0.0015" at 0.5" from the center, consistent with the center at that end being exactly on-center. This means a perfectly straight shaft with perfectly drilled center at one end and a center off by 0.001" at the other would measure 0 TIR at the timing end, 0.001" in the middle, and 0.002" at the drive end.

I'll recut the center at the drive end once I have the crankshaft apart and can hold that spindle in a 4-jaw chuck. But, for now, knowing how much TIR a perfectly straight shaft should have with one center off by 0.001" I can determine how well my crankshaft is currently trued. Unfortunately, as noted earlier in the previous paragraph, rather than 0.001" in the middle the TIR is ~0.006"-0.008".

I marked all the points of high and low readings for all of my measurements from which it appears both spindles are straight, not bent. However, the ~0.008" TIR near the center says something is wrong.

The TIR of the side of the drive-side flywheel near its outer rim is 0.0075" and of the timing-side flywheel is 0.006". These faces are 4" from the crankshaft axis. The spacing between flywheels varies by 0.012" with it a maximum at the same orientation where the spindles come closest to the indicator.

Within measurement uncertainties all of the above is quantitatively consistent with the two spindles being straight and mounted "perfectly" in their respective flywheels, but the flywheels held together by a crankpin that is ever so slightly angled in the flywheels. As a result, the previous rebuilder installed a crankshaft that has a TIR ~8x larger than is acceptable.

Attached Files IMG_6355.JPG
Last edited by Magnetoman; 02/14/18 7:35 pm. Reason: added photos
Re: 1928 Ariel Model C [Re: Magnetoman] #719604 12/21/17 2:31 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
I now have the crankshaft apart. It took ~130 ft.-lbs. to loosen one of the nuts and ~160 to loosen the other. I was surprised the torque was so small since my notes show 200 ft.lbs. is used on the same size nuts on the crankpin of a BSA B44. After slipping two 1/2" steel bars between the flywheels, 2" spacers to elevate them, and two additional bars to catch the falling flywheel, it then took 3000 lbs. from the press to pop the crankpin loose from one flywheel (not necessarily the same side as the 130 ft.lbs. because I didn't keep track of which was which) and 3800 lbs. for the other.

Although I could have hit it with as much as 30T, a 2T press would have been (barely) sufficient. I can't remember having seen these figures before, which is why I've listed them here in case someone else faces this job and needs to know if their press will be sufficient.

The crankpin was in good shape with no issues whatever with the race or rollers. The absence of up-down clearance of the rod and the tiny amount of polishing of the center of the race implies the crankpin has seen very limited use, i.e. it is essentially new. I'll pack it with the other spares for the Cannonball, but if it reaches the point where a replacement crankpin is needed in order to continue, I'll be booking a flight home...

There are two holes in one of the tapers of the crankpin whose reason for existence I don't understand because there are no holes in the corresponding taper in the flywheel. These are separate from the hole that's present to feed oil to the big end. The Alpha crankpin has the same two holes in one taper, but the crankpin that was in the bike isn't an Alpha. Stamped on its end is RH L171. Since Alpha supplies the same crankpin for some later Ariels perhaps those mystery holes are there to perform a function in them.

With the rod freed from its former duties I put it on the surface plate. It's twisted horizontally by 0.017" over the length of the crankpin, which is no big deal, but also bent in the up/down direction by 0.017" which is a problem. I'll set up a different measurement to see if that's due to a simple, slight bend in the rod or if the bush at the top was pressed into place and reamed slightly askew. It wouldn't surprise me if the rebuilder installed and reamed it without taking the crank apart, which easily would explain the problem. Either way it has to be fixed because otherwise it would force the piston to rub on the cylinder (unless I have it bored with 0.018" clearance...). No matter what I planned to make a new bush myself using the bronze Chaterlea25 sourced for me (again, thanks) so I'll try to take a bit more care than the previous rebuilder did. Conveniently, both sides of the big end are machined surfaces so I'll be able to clamp that end to the bed of the mill for drilling and reaming of the new bush after it's pressed into place.

With the separate crankshaft components now laid out on the workbench I'll fire up the Magnafluxer to inspect them. Also, I still need to plate the 0.001" of Cu on the C3 drive-side bearing that gunner located (again, thanks) for a proper interference fit.

Aside from the above, it's now going to be mostly machining work for a while to get a variety of crank and cam bushes fabricated, crankshaft axis line bored, cylinder base and crankcase mouth decked, and cylinder bored (plus, whatever else I've forgotten). Once all that is done I'll be ready to assemble the bottom end of the engine and then turn my attention to the head.

Meanwhile, the "high" (i.e. closer-ratio) gear set is winging its way to me from the UK with tracking showing an estimated delivery "no later than 4 January." Even an optimist wouldn't predict I could be ready to start on the gearbox by then, but everything should be in place once I get to that task.

Attached Files IMG_6357.JPGIMG_6358.JPG
Last edited by Magnetoman; 02/14/18 7:34 pm. Reason: added photos
Re: 1928 Ariel Model C [Re: Magnetoman] #719638 12/21/17 6:24 pm
Joined: Feb 2012
Posts: 189
L
L.A.kevin Offline
BritBike Forum member
Offline
BritBike Forum member
L
Joined: Feb 2012
Posts: 189
Originally Posted by Magnetoman


With the crank between centers, the total TIR is 0.006" on the drive side spindle measured next to the flywheel, 2.9" from the closest center, and 0.003" at 0.5" from the center, consistent with the center at that end being, ahem, drilled off-center by ~0.001" (for a TIR of ~0.002"). The same measurements on the timing side are 0.008" at the flywheel, 2.4" from the closest center, and 0.0015" at 0.5" from the center, consistent with the center at that end being exactly on-center. This means a perfectly straight shaft with perfectly drilled center at one end and a center off by 0.001" at the other would measure 0 TIR at the timing end, 0.001" in the middle, and 0.002" at the drive end.


Just from experience in my industry (electromechanical aircraft parts), centers are often a source of error. For really critical measurements, parts are clamped in v-blocks on the bearing journals using packing tape on the v-block and a Teflon end on the machinist clamp to protect the journals. Many times, I've found that there has been error by relying on the non-functional shaft end center to measure run-out. You've probably thought of this, M-M, but I just wanted to remind you. Centers can be used, but you really have to check to make sure they run true. I found the worst cases of this sort of error is when live centers were used and different bearing journals have been cut on different machines.

Re: 1928 Ariel Model C [Re: Magnetoman] #719641 12/21/17 6:44 pm
Joined: Feb 2014
Posts: 565
C
chaterlea25 Online Content
BritBike Forum member
Online Content
BritBike Forum member
C
Joined: Feb 2014
Posts: 565
Hi MM,
Re the big end nut torques ?
Does it take the same ft/lbs to undo a nut as to tighten it ?
I don't believe so? I think that the metal yields a little over time after tightening ??
The Ariel flywheels are cast where as the B44 wheels are steel so friction /grip and yield of the metal will be different
Recently I rebuilt a couple of Indian Chief engines, The torques for the big end and main shaft nuts is 100ft/lbs when the engine has
"Z" metal flywheels, non "Z" flywheels get 70/75 ft/lbs
These pins and shafts do not have shoulders though ( I could go and check thread size and pitch on the old parts if needed)
With shouldered pins the shoulders need to to seat against the flywheel when fully tightened,
a gap between pin shoulder and flywheel when fitted by hand is essential so the grip is taken up by the taper

Final torque value is not a fixed figure I believe
Whatever the nuts need to pull the pins against the shoulders, +
Of course the flywheel taper bores stretch every time the pins are replaced which does not help when fettling old engines
From The figures that you measured to release the tapers it looks like the flywheel bores are in good order though

I prefer to not rely on the mainshaft centres, but set up the assembly on bearings and v blocks instead

I believe it would be very difficult to evenly plate the main bearing ? the surface of the copper plating will not be smooth ?
I believe that you need to plate oversize and machine to the desired figure
I think I would have gone the route of a steel sleeve on the bearing as you had the case set up on the milling machine ??

Always more than one way to skin a cat!!!
John





Re: 1928 Ariel Model C [Re: Magnetoman] #719654 12/21/17 9:27 pm
Joined: Oct 2017
Posts: 247
G
George Kaplan Offline
BritBike Forum member
Offline
BritBike Forum member
G
Joined: Oct 2017
Posts: 247
Hi MM, I cant help with the balancing or truing of your crankshaft but I was just reading the last few posts and it occurred to me that this could be the first time that anyone has blueprinted a 1928 Ariel engine.

John

Re: 1928 Ariel Model C [Re: Magnetoman] #719659 12/21/17 10:09 pm
Joined: May 2013
Posts: 854
O
old mule Offline
BritBike Forum member
Offline
BritBike Forum member
O
Joined: May 2013
Posts: 854
George, now everyone will want it done!

Re: 1928 Ariel Model C [Re: Magnetoman] #719725 12/22/17 4:10 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Originally Posted by George Kaplan
this could be the first time that anyone has blueprinted a 1928 Ariel engine.
Including on the factory assembly line...

Originally Posted by chaterlea25
Does it take the same ft/lbs to undo a nut as to tighten it ?
Ah, of course your explanation must be correct.

Originally Posted by L.A.kevin
Just from experience in my industry (electromechanical aircraft parts), centers are often a source of error.
Originally Posted by chaterlea25
I prefer to not rely on the mainshaft centres, but set up the assembly on bearings and v blocks instead
I agree with both of you, and I won't be relying on the centers when I assemble the crankshaft. Both centers are (were) rusty and probably have been hammered on so it's surprising they're as close as they are. However, they served my purpose better than a V-block would have for characterizing the current condition of the crankshaft.

The limitation is that the ends of each shaft aren't useable for precision measurements because of threads and splines. Had I held the crank next to the flywheels, as I did for balancing, I only would have been able to measure the runout fairly close to where it was being supported which would have disguised the degree of misalignment. Holding it by the centers, after having determined how off-center the centers were, allowed me to make better measurements of the deviations from being straight. Again, this was just for the purpose of seeing what the crank was like as-received, not for the highest precision reassembly. That said, centers can be useful so I've already recut the off-center center after centering it to better than a half-thou., the best I could achieve given the less than perfect surface of the spindle. Whether or not I'll want to use that center in the future remains to be seen, but now it's in good condition in case I do.

Originally Posted by chaterlea25
I believe it would be very difficult to evenly plate the main bearing ? the surface of the copper plating will not be smooth ?
I haven't done it yet but I don't expect this to be a problem. I'll curve the Cu anode into a cylinder, and anyway the bearing will be an equipotential surface, so the plating will have no choice but be uniform. I expect it will be smooth as well, but that's not an issue. With the case heated to 100 oC and 0.001" of Cu on the bearing it should drop right into place. The Al will then close up on it when it cools to hold it in a death grip thanks to the 0.002" interference fit.

I'll plate for half the time I've calculated it should take and measure the progress at that point. Based on that measurement I'll adjust the remaining time, if necessary to give the 0.001" thickness (0.002" increase in diameter) I'm looking for.

Bearing steel is high strength and thus especially prone to hydrogen embrittlement. Based on the best information I could find, immediately after plating I'll toss the bearing in an oven at 375 oF for a full 24 hours to eliminate the hydrogen.

Originally Posted by chaterlea25
I think I would have gone the route of a steel sleeve on the bearing as you had the case set up on the milling machine ??
Always more than one way to skin a cat!!!
When possible I try to err on the side of removing the least amount of material I can since, generally speaking, material can't be put back once it's removed. Also, a sleeve is a more complicated solution. As long as there is a 0.002" interference fit, either of bearing in housing or of bearing in sleeve in housing, what could possibly go wrong?...

On the subject of plating, I originally convinced myself that pits in the shafts at either end of the camshaft only degraded a small enough fraction of the surface area that they wouldn't be a problem. Unfortunately, I couldn't keep myself convinced of that.

Figuring out how deep the pits are, and hence how thick a layer of hard chrome plating would need to be, took a bit of effort. I easily could have used the depth of focus on a standard microscope to determine the depth of the pits (the z movement of the stage is calibrated in microns). But to do that the cam would have fit in the space under the objectives, which it doesn't. My inverted microscope was no good either because the gear on the cam doesn't let the surface in question lie in the right plane.

I then decided to see if I could use an old surface roughness gage as a "secondary standard" to make an estimate, but I immediately discovered there are no units for the numbers on it, i.e. are they microinches or microns, and are they average roughness values Ra or peak-to-peak roughness values Rz which are ~4-10x larger depending on the degree of randomness of the roughness?

So, using a profilometer I determined the numbers engraved in the gage are a reasonable match to Ra in microinches. I then compared the visual "depth" of the various patches on the gage with the appearance of the pits on the cam and decided a certain patch engraved 500 microinches was a reasonable-ish match. However, converting from Ra to Rz for non-random surfaces is problematic so I then put the gage in the microscope and determined the depth of the grooves in this patch is around 30 microns (~0.0012"). As a check I then used my profilometer on the gage to display Ra (356 microinches, vs. the 500 engraved on the gage) and Rz (0.000992"). I count the latter as better than perfect agreement with my visual determination/estimate.

The above "only" took ~45 minutes away from doing anything tangible to determine I need to deposit ~0.001" of hard chrome to fill all but the deepest of pits. This is convenient because currently the diameter of the shaft at one end is 0.7462"-0.7470" and at the other is 0.7460"-0.7465". Using the rule of 1.5 thou./inch for the proper clearance between a shaft and bush each of these has to be built up by ~0.002" in diameter (i.e. ~0.001" Cr thickness) to properly fit in bushes that are reamed to 0.7500". This is well within the ~0.006" thickness the web tells me is reasonable for hard Cr so a hard Cr plating kit is already on its way to me.

I'll probably end up plating ~0.002" and then grinding back to size using my toolpost grinder. As with any plating hydrogen embrittlement is a problem, and it appears it's especially bad with Cr. Although the cam isn't made from high strength steel I'll still bake it for a full 24 hours at 375 oF immediately after plating. First, though, I'll need to find something to "paint" most of the cam with that's easy to remove afterwards, in order to leave only the spindles at both ends exposed for plating.

As an aside, the cam lobes show no sign of pitting so they've been ground at some time in recent history. I've yet to measure the base circle and lift to determine what changes might have been made to them (assuming I can find or infer the original values).

Re: 1928 Ariel Model C [Re: Magnetoman] #719728 12/22/17 5:09 pm
Joined: Oct 2017
Posts: 247
G
George Kaplan Offline
BritBike Forum member
Offline
BritBike Forum member
G
Joined: Oct 2017
Posts: 247
Hello MM, I am following your progress with interest and quite often have a few questions and sooner or later you inevitably answer them before I ask them. You mention in your last update that, for the hard chrome plating, "I'll need to find something to "paint" most of the cam with that's easy to remove afterwards". Before you mentioned that I was wondering how you intend to mask the bearing before copper plating it so that you only plate the outer surface that you want to increase the size of?

I was thinking of sandwiching the bearing between two custom made washers that would leave the outer surface exposed. This would also provide a way of holding the assembly in the plating tank. Or do you have some other arrangement in mind?

John

Re: 1928 Ariel Model C [Re: Magnetoman] #719750 12/22/17 9:26 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Originally Posted by George Kaplan
I was wondering how you intend to mask the bearing before copper plating it so that you only plate the outer surface that you want to increase the size of?
Keeping in mind that I haven't yet plated the bearing, so what follows needs to be taken with a grain of salt for now, I simply used Kapton tape to cover the sides. Although I had no doubt the tape would resist water, I tested it anyway by sticking a piece to a chunk of steel and letting it sit in a beaker of water for a few hours. For the electrical lead I wrapped one turn of brass wire around the outer surface (the one that will be plated) and tightened it with safety-wire pliers. That will leave a narrow line of unplated steel under the wire, but the area of that line will be negligible. While the tape and wire work for the simple geometry of a flat-sided bearing where an unplated line doesn't matter, the cam will require a different masking solution.

I was getting ready to plate yesterday but at that point discovered that whereas the ad for the Caswell "Flash Cu" kit I bought said it "can be used to plate copper over steel, zinc, pot metal, ..." the sheet of instructions that came in the box said it "should not be used on steel, zinc, iron..." I called the tech rep today and he confirmed the ad is correct (i.e. it can be used), and that the instruction sheet is for their "Acid Cu" kit. Anyway, meanwhile I had ordered their hard Cr kit which will come with a 180-page manual so I decided to wait until that shows up in case it contains helpful information. I should have no problem filling my time for the next week with other work that needs doing.

I've done electroplating three times I can think of over the past 40 years so this isn't my first venture into it. Although the principle is very simple, producing the best quality results requires a witch's' brew of additives, a current density for the given material that is neither too high nor too low, the right temperature range, the proper surface "activation," etc. Since I don't want to take the time to reinvent the process, I just want to plate the parts with a minimum of time and effort, the premium paid for the chemicals in proven kits is well worth it to me.

Re: 1928 Ariel Model C [Re: Magnetoman] #719768 12/23/17 1:30 am
Joined: Sep 2007
Posts: 1,127
gREgg-K Online Content
BritBike Forum member
Online Content
BritBike Forum member
Joined: Sep 2007
Posts: 1,127
I just had an idea about how to mask the bearing ID while leaving the entire OD of the bearing race open for plating. Protect the bearing with two disks attached to the bearing's open "faces" by a through bolt, with one disk on each face. If need be, the disks could also be sealed to the edge of the bearing race.

If the disks are metal, they could additionally serve as the electrical contact for the lead to the power supply.

Workable?
.. Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
[email protected]
Re: 1928 Ariel Model C [Re: Magnetoman] #719821 12/23/17 5:51 pm
Joined: Nov 2011
Posts: 5,353
Magnetoman Online Content OP
BritBike Forum member
OP Online Content
BritBike Forum member
Joined: Nov 2011
Posts: 5,353
Originally Posted by gREgg-K
If need be, the disks could also be sealed to the edge of the bearing race.
If you cut the disks to size and found a way to seal their edges as well as the bolt hole it certainly would work.

I already knew from measurements I made a few months ago that the cylinder bore was slightly tilted from being perfectly perpendicular to the base of the muff. The base of the mounting flange also was slightly warped and heavily pitted from rust that had been cleaned away and painted over.

To get the cylinder back into shape, yesterday I machined a 1"-thick steel plate to be flat to a half-thou. and bored holes in it so I could bolt to the top of the cylinder. Since the sleeve projects above the muff to form the mounting surface for the head this meant the top of the steel plate was parallel with that surface. I then mounted this assembly in the four-jaw chuck and adjusted the runout of the inner surface of the lower end of the cylinder to be ~0.001". Since I already knew the bore of the cylinder was tilted in the muff it would have been better to center it on the OD, but that surface is too rough to use for this to any degree of accuracy. Anyway, with the centering I did it was possible to skim the base of the mounting flange to within no worse than ~0.01" of the outside edge of the cylinder which is good enough for it to fit in the cases.

I had to remove from 0.015" from the base to get it flat, i.e. parallel with the top, mounting flange. This also was enough to remove all but a few of the deepest pits. When centered on the ID of the cylinder the runout of the OD was ~0.01" consistent with my measurements of a few months ago from which I inferred the cylinder had been (incorrectly) bored by placing it upside down on a boring bar rather than properly right side up. Now, after machining, when I placed the cylinder upside down on the surface plate and ran an indicator around the mounting flange I found the surfaces parallel with each other to within a half-thou. side-to-side. I'm calling that good enough...

Once the mouth of the crankcase is faced to be accurately parallel with the crankshaft axis the piston will go up and down as it should without being forced back and forth sideways toward the cylinder wall on each stroke.

The cylinder is now ready for boring, to be supported by parallels under the base flange and with a torque plate (that I made a few months ago) bolted to the top plate. However, before doing that I'll need to revisit my balance factor post to look for the error koan58 said he found, to see if it affects my choice of which piston to use.

Returning to the crankshaft, I mounted the two halves by their shafts in the lathe and measured the amount of wobble of the sides of the flywheels. The timing side wasn't perfect, but wasn't awful at 0.003". However, the drive side was 0.016". Even if the crankpin went into its tapers perfectly straight these shaft would make a pretzel of the assembled crankshaft. I don't have experience with this but I hope this large amount of wobble can be corrected by careful reassembly and doesn't mean the tapers have been permanently distorted.

In both cases the orientation of maximum wobble was opposite to the crankpin. What this means is with the mounting of the crankpin slightly crooked it would be possible to reduce the runout of the shafts on the assembled crankshaft to roughly the average of the 0.003" and 0.016", i.e. to ~0.010", when supported on the centers and measured next to the flywheels. Not coincidentally, in a post a few days ago I determined that to be ~0.006"-0.008". Showing, if nothing else, that two wrong actually can make a (almost) right...

Clearly, there isn't a nut or bolt on this bike that isn't going to be unmolested before this rebuild is finished...



Page 18 of 83 1 2 16 17 18 19 20 82 83

Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | DVD- Manuals & Parts books
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
BritBike Sponsor
Powered by UBB.threads™ PHP Forum Software 7.7.3