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Re: 1928 Ariel Model C [Re: Magnetoman] #720080
12/26/17 11:45 pm
12/26/17 11:45 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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I decided to make my own 2-post version of an $800 crankshaft assembly fixture like the K&L.

The premise of such 2-post and 3-post fixtures is that if both crankshaft spindles are held precisely in line with each other when the crankpin is pressed into place the assembled crankshaft will have no choice but to have 0 runout. However, the design is at the mercy of tolerance buildup so I expect final tweaking of the crank will be required. If the holes for the spindles are oversized by only, say, 0.001" that alone would allow the centerlines of the shafts to be displaced from each other by as much as 0.002". Still, the closer the alignment is to start the easier it should be to get to the final result.

Commercial units like the K&L appear to be made from 2"-thick steel but I'm making mine from 1" because i) I have the steel on hand, and ii) it won't have to survive being operated by an uncaring mechanic. While thinner steel will bend easier than thicker, as described in an earlier post I've determined that less than 4000 lbs. will be required to press the Ariel crankpin into place. It appears Harley cranks require 3-4x this, and commercial fixtures are intended to handle that additional force without excessive flexing.

Anyway, today I made the two alignment posts from 1"-dia. steel and, after rigidly clamping the 1" plates together, drilled and reamed one of the three holes before quitting for the day. I'll use bushings in the holes accurately sized to the worn spindles. Also, this will let me use this same fixture in the future should I ever need it for a Gold Star crankshaft.

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Re: 1928 Ariel Model C [Re: Magnetoman] #720093
12/27/17 1:52 am
12/27/17 1:52 am
Joined: Nov 2012
Posts: 658
Isle of Wight, UK
K
koan58 Offline
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Isle of Wight, UK
I can see how such a jig would give you a good start with the assembly.
I can imagine others less thoughtful than yourself assuming that they can assemble a crank with such a tool.
At the end of the day, I'd be surprised if you didn't resort to the traditional whacking with a soft hammer while tightening the nuts to achieve the best compromise.
I suspect you would almost be reliving something done in 1927!

Re: 1928 Ariel Model C [Re: Magnetoman] #720142
12/27/17 4:15 pm
12/27/17 4:15 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Tracking of my "High" (i.e. closer ratio) gearbox that was shipped to me via myHermes International shows it will be delivered "no later than 04/01/2018." It also shows it arrived at their Hub somewhere in the UK on 22 December and then 8 hours later was "Misrouted to Incorrect Depot," with no further tracking information after that. So, following their instructions for what to do if tracking hasn't been updated for a few days, I contacted them via their 'live chat.' I was told that since it isn't Jan. 4 yet they don't consider the package lost (yet) so, while they have no information on where it is at the moment, I shouldn't worry. Oh well, at least it's insured.

Re: 1928 Ariel Model C [Re: Magnetoman] #720145
12/27/17 4:37 pm
12/27/17 4:37 pm
Joined: Dec 2004
Posts: 9,501
Scotland
kommando Online content
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Hermes do not have the best reputation so on the 5th I would be straight onto them unless its been updated, luckily our local Hermes driver is good so once they get themselves sorted in the hub we do not have to worry. You can relax a bit once its exited the UK.

Re: 1928 Ariel Model C [Re: kommando] #720160
12/27/17 7:06 pm
12/27/17 7:06 pm
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Posts: 4,649
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Magnetoman Offline OP

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Originally Posted by kommando
You can relax a bit once its exited the UK.
A month ago I was expecting a delivery from Amazon.com ("by 8pm") when a car pulled up around 8:15pm when it was dark, circled the driveway, then stopped maybe 150 ft. back down the driveway. I went outside and could see the driver looking at his iPhone in a way that appeared he was trying to figure out what to do. I walked over to him and he asked me where the front door was. I said he could just hand me the package but he said the app wouldn't let him mark the package as delivered unless he was within 50 ft. of the front door. Also a month ago UPS tracking site showed that a package to me had been misdirected to the east coast, after which I followed it as it made its way back across the country to be delivered. The point is, with current technology there's no excuse for Hermes not to know where a package is at all times, even if it's not where it's supposed to be.

Speaking of packages, 15 min. ago a Caswell Hard Chrome plating kit was delivered, complete with their 181-page manual. So, bearing and camshaft plating should happen within the next few days.

Re: 1928 Ariel Model C [Re: Magnetoman] #720308
12/28/17 10:59 pm
12/28/17 10:59 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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My younger, motorcyclist, daughter is in town for the week and we had hoped to take our traditional father/daughter ride for lunch in a mining town 100 miles from here, this year on Gold Stars. But she has to return to New York tomorrow, and visiting with relatives and friends this week didn't leave any time slots open that were long enough. Life is full of disappointments...

I didn't have a lot of time to work on the Ariel today (or any time this week, for that matter) but I copied the appropriate Cu plating section of the Caswell manual and highlighted the important points. I then laid out all the necessary chemicals, beakers and heater to be ready to plate, possibly tomorrow afternoon.

While doing some more machining on the crankshaft alignment fixture I calibrated the full range of the oven in the garage so in the future I would know where to set the dial to get the required temperature. In this case, the oven is needed for heating the bearing (and later the camshaft) after plating to remove the hydrogen. The oven takes ~15 min. to reach equilibrium at each new setting so I'd turn the dial to a new setting, machine for a while, then read the temperature when the light was cycling on and off indicating it had reached the new set point.

Another bit of progress today is that Hermes updated their tracking of my gearbox to "Receipt at Hub" from the previous "Misrouted to Incorrect Depot." So, there's hope they haven't permanently lost it. Yet.

Re: 1928 Ariel Model C [Re: Magnetoman] #720457
12/30/17 3:53 am
12/30/17 3:53 am
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Hermes tracking shows the package went through several steps today, the last of which was "handed over to the Landmark depot." I found that Landmark is owned by the Belgian post office so I hope this doesn't mean the gears are taking an eastern route to me at the rate of a few hundred miles per week. At that rate it should be here in time to use in the 2020 Cannonball.

I finished the crankshaft alignment jig today and it came out great. However, whether or not it actually helps when it comes time to reassemble the crankshaft remains to be seen. I made it to very tight tolerances which I can see could be a problem unless I get the spindles accurately perpendicular to the flywheels prior to assembly, otherwise the shafts could bind in the jig.

Tracking Update: The gears have finally made it to Heathrow nine days after they were shipped from a village 125 miles away, for an average speed so far of 0.6 mph.

Last edited by Magnetoman; 12/30/17 3:59 pm. Reason: Tracking Update:
Re: 1928 Ariel Model C [Re: Magnetoman] #720597
12/31/17 2:31 pm
12/31/17 2:31 pm
Joined: Aug 2006
Posts: 476
Dallas Texas
RPM Offline
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Dallas Texas
Happy New Year MM. Glad you are making some progress. Always seams to take longer than expected. Hurry up and wait.
I have made progress on the Nortons. We have the rolling chassis built for the 23 and 24. The 1924 had a crack in the steering head just behind the neck, rear wheel was tilted to the left by 9 degrees, Front end spindles would not rotate freely and front end had bent plates on both sides. The 1924 had 1/4" balls installed on the steering head instead of 5/16" balls. That did not work well. We never rode or heard bike run when we got it. It was put together and sold. Never started or ridden. Reminded me of something that would have come out of the Meacum Vegas auction. Looked nice but scary bad on the inside. Sun rims ,new spokes and sealed bearings in wheels are working great.
The 1923 was nice riding bike when we started in on it. Frame was nice and straight. Motor was a little tired but overall pretty good.
Trying to get everything going by April for a shake down run in the Texas Hill Country. Sounds easy but it won't be.

Re: 1928 Ariel Model C [Re: Magnetoman] #720613
12/31/17 4:52 pm
12/31/17 4:52 pm
Joined: Nov 2011
Posts: 4,649
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Magnetoman Offline OP

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Originally Posted by RPM
Sounds easy but it won't be.
Now there's an understatement...

Originally Posted by RPM
The 1923 was nice riding bike when we started in on it.
I'm reminded of a conversation with my wife earlier this fall:

wife: What are you so busy doing in the garage?
me: I'm completely rebuilding the Ariel from the ground up.
wife: Why? It was running fine when you got it.

I trammed the mill to better than 0.0005" out of 13" to get ready to ream the small end bush, but then decided the lathe would be better. I used chaterlea25's favorite PB1 bronze to make a new bush, a boring bar to make the ID a bit smaller than the final size but perfectly parallel to the OD, and then reamed to the final 13/16" (0.8125"). After pressing it into place I reamed it again but found it a smidgen too tight with the old gudgeon pin. At that point I measured the ODs of the three pins and found: old one that was in Ariel 0.8112", Gardini 0.8115", and Omega 0.8122". I'll measure the actual ID of the bush today and, after making my final decision on the piston to use, I'll gently hit it with a hone to size it for the appropriate pin. I'll also measure the side-to-side tilt to confirm that it's well within the limits it needs to have.

As a check on the point koan58 asked about my earlier balance factor calculation I measured the weight of the bush I removed. It's 88.86 g. Rather than calculating the weight of an original 1" ID bush based on geometry and an assumed density of bronze, I took an experimental approach. I drilled it with a 1" bit and measured the weight again. It's 47.77 g, for a difference of 41.09 g in the weight of the small end of the gudgeon pin. This is different than my previous calculated weight so was well worth the time it took to determine this. Thanks, koan58, for your post that prompted me to do this.

Actually, the bush protruded from both sides of the rod so, assuming an original 1" bush would have been the width of the rod, it would have weighed slightly less. I trimmed the bush to the width and remeasured it at 40.65 g for a final-answer difference of 48.21 g. I'll use the 40.65 g value of the weight of an "original" 1" ID bush when I revisit the balance factor calculation.

Finally, KevinN must have received an email from the organizers I haven't seen yet because yesterday on his AMCA thread he was able to post a route map showing the locations (but not the still-secret names of the towns) of the evening stops. Participants were given the stops a few weeks ago but sworn to secrecy.

[Linked Image]

Re: 1928 Ariel Model C [Re: Magnetoman] #720643
12/31/17 8:11 pm
12/31/17 8:11 pm
Joined: Nov 2012
Posts: 658
Isle of Wight, UK
K
koan58 Offline
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Isle of Wight, UK
Hi MM,
Thanks for your thanks, I'm just glad that it was worthy of, rather than a waste of, your time.
Just by way of a footnote for purposes of comparison between real-world and calculation:-

Reducing bush actual = 88.86
calc = 89.40 (as a parallel tube, no tapers)

Original bush actual = 40.65
calc = 39.93

Considering the possible slight errors in density and dimensions, I think the correspondence is pleasing.

I look forward keenly to your electrolytic adventures!

Hoping the "laws of physics" continue to apply for you in 2018! Dave

Re: 1928 Ariel Model C [Re: Magnetoman] #720668
12/31/17 11:32 pm
12/31/17 11:32 pm
Joined: Mar 2013
Posts: 348
Irene, South Africa
robcurrie Offline
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Irene, South Africa
The Cannonball organisers posted the map on their Farce Book page, their website doesn't seem to be working properly except for their merchandise section.
Rob C

Re: 1928 Ariel Model C [Re: Magnetoman] #720758
01/01/18 5:15 pm
01/01/18 5:15 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Originally Posted by koan58
Hi MM,Thanks for your thanks,
Credit where credit is due.

Originally Posted by koan58
for purposes of comparison between real-world and calculation...
This is a good opportunity to make a general point. For the record, (absent arithmetic error...) the level of agreement between estimate and calculation is as to be expected. When someone (not koan58) writes something like "in theory is should have been..." and then quotes a 'real world' result that differs all that means is they used the wrong theory (or made an arithmetic error...).

Originally Posted by Magnetoman
I measured the ODs of the three pins and found: old one that was in Ariel 0.8112", Gardini 0.8115", and Omega 0.8122". I'll measure the actual ID of the bush today
Setting the bore gage on the diameter of the smallest pin (0.8112") the ID of the bush is 0.0002" larger. This very tiny clearance was enough to allow the smallest pin to be a tight press fit, but the other pins are larger so I'll have to hone the bush for whichever of the two aftermarket pistons I decide to use.

With the bush in place it was time to address the slight bend in the connecting rod. As far as I could determine it was a simple bend originating at the big end and resulting in the small end being displaced sideways by 0.025". Since the small end is ~6.5" away from the point of the bend, and the gudgeon pin is ~2.6" wide, this resulted in one end of the pin being 2.6/6.5x.025 = ~0.010" higher than the other. The top of the piston is ~1.25" above the gudgeon pin so this would result in one side being 1.25/2.6x.01 = ~0.0048" closer to the cylinder wall than the other (similarly for the opposite skirt since it's roughly the same distance below the pin and the top land is above it). Given the piston/bore clearance, clearly this is a problem that has to be addressed.

It took repeated use of the press, precision 2"x4"x6" blocks, and test indicators to reduce the side-to-side tilt of the pin to 0.0018". The problem with doing better than this isn't with the measuring instruments, but with the reproducibility of mounting the rod in the blocks for measuring using the machined surfaces of the sides of the big end. My first project of the New Year will be to machine a mandrel to fit in the big end and use it to see if I can do a bit better. But, the 0.0018" tilt translates to just under 0.001" reduction in clearance to the bore at the top and skirt of the piston, which would be fine.

Re: 1928 Ariel Model C [Re: Magnetoman] #720784
01/01/18 7:48 pm
01/01/18 7:48 pm
Joined: Aug 2001
Posts: 2,002
Greensboro, NC
Alan_nc Offline
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Is there a way to calculate the rate of ware to the cylinder? In other words: at the end of 3,000 miles how wallowed out will the cylinder be. I know you are trying to minimize this but with whatever you do are you going to have an engine that self destructs at x miles. And....if this can be calculated is there a way to predict that x miles will be y miles past the completion point? Yea I know.........if pigs could fly


Alan
Cleared m out....left only
59 BSA Bantam (Trials)
78 Triumph Bonny (UPS)
02 Suzuki GS500
Re: 1928 Ariel Model C [Re: Magnetoman] #720819
01/02/18 12:27 am
01/02/18 12:27 am
Joined: Mar 2013
Posts: 348
Irene, South Africa
robcurrie Offline
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Irene, South Africa
I think it will be very difficult to calculate wear due to there being so many variables, you would do better to use historic data rather - but that may vary vastly because of factors like weather, geology of the area the engine is used in and rider, to mention a few. Also, 3000 miles is not very much for an engine like this, it would just be bedded in nicely!

Rob C

Re: 1928 Ariel Model C [Re: Magnetoman] #720842
01/02/18 8:49 am
01/02/18 8:49 am
Joined: Dec 2004
Posts: 9,501
Scotland
kommando Online content
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Scotland
Take a sample of used oil and send it away for analysis, after the 3rd oil change you will have an idea of the typical analysis of a normal contents, any subsequent analysis showing different results tells you something is up.

Re: 1928 Ariel Model C [Re: Magnetoman] #720851
01/02/18 2:12 pm
01/02/18 2:12 pm
Joined: Feb 2008
Posts: 4,461
New Jersey USA
Tridentman Online content

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New Jersey USA
What Kommando describes is common practice on large (10000-15000 hp) diesel engines being used in ships or for land based power generation.
In the latter case the engines are run 24/7/365.
It is quite a sight to see the tappets being readjusted while the engine is running---the locknuts have a wrench about 3 feet long and it takes two guys to do it!
But--I digress---the oil analysis in these situations is used to schedule down time for bearing changes etc.
But to do so needs a lot of data gained over many years for it to be at all accurate.
Overall I would suggest that it is of dubious value in this case.
I tend to agree with Rob---this engine --due to the great attention to detail on the part of MMan, is going to be better than any Ariel engine that. ever left the factory.
And even factory or back street assembled engines in the day with poor or non existent maintenance, could swallow 3000 miles with little problem
Just my two centsworth of course.

Re: 1928 Ariel Model C [Re: Magnetoman] #720852
01/02/18 2:41 pm
01/02/18 2:41 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Originally Posted by Alan_nc
Is there a way to calculate the rate of ware to the cylinder?
I doubt cylinder bore wear will be an issue. The exposed valve guides, on the other hand...

Yesterday ended with me 0.0010"-0.0015" closer to assembling the crankshaft. I machined a mandrel for the ~1.5" ID of the big end of the rod with a tight push fit, and with the ends of the mandrel parallel with each other to within 0.0001". Clamping one end of the mandrel with the rod against the side of a precision "cylindrical square" would make the top surface of the gudgeon pin perfectly parallel to the surface plate if the bend in the rod had been completely eliminated. A number of trips back and forth between the press and the surface plate got the gudgeon pin parallel to within 0.0010"-0.0015" (~0.0005" was the reproducibility of the measurements when I would unclamp the assembly, rotate the rod somewhat in the mandrel, re-clamp, and re-measure).

Key to doing this was having a way to reproducibly bend the rod, and to reproducibly measure the result. I used large C-clamps to hold the platform of the hydraulic press rigidly against the frame and used a dial indicator with magnetic base to determine the deflection of the rod. The big end of the rod was clamped between two 2"x4"x6" machinist blocks which in turn were held to the thick steel plates on the press's platform by large C-clamps. All of this was to remove as much extraneous free play as possible.

I would zero the gauge and then apply force in ever increasing increments, each time dropping back to zero force to read the indicator. The initial applications of smaller forces ensured play had been removed from the system, but at some point after deflection measured an inch or so from the small end had exceeded ~0.1" the indicator showed a permanent deflection had been introduced. Already from my most recent measurement on the surface plate, corrected for geometry, I knew how much deflection I needed so I would stop when that point was reached. However, working to 0.0001" with 8" C-clamps and a 30T hydraulic press has its limits so even when I was very close it still took a few more trips back and forth to achieve the final result.

Despite all of the above I'm not finished with the rod just yet. I let it soak in the oven at 150 oC for two hours last night and will remeasure it later today to make sure remnants of the bend haven't returned. I pulled that temperature out of the air; it's higher than the big end will reach in operation, which is where the bend was located, but lower than the small end. I'll also Magnaflux it again. Finally, when I assemble the crank I'll reuse the crankpin and bearing assembly that was in it since they show no sign of wear, leaving me with a new Alpha crankpin surplus to needs.

The ~0.025" bend in the rod that I just reduced to ~0.001" was in it when I removed it from the engine. That bend was large enough that it should have caused the old piston to contact the cylinder wall so I examined that piston again. Sure enough, there is obvious scuffing of the lower portion of the skirt on one side and the portion above the gudgeon pin on the other. The piston clearly had been well-worn when the previous rebuilder installed it, and I knew I would have to replace it, so I hadn't paid much attention to the specific marks until now. I'll speculate that the bend was introduced by someone who pressed or pounded the gudgeon pin (or bush) in or out at some time without supporting the piston/rod.

Attached Files IMG_6398.JPGIMG_6400.JPG
Last edited by Magnetoman; 02/14/18 6:12 pm. Reason: added photos
Re: 1928 Ariel Model C [Re: Magnetoman] #720888
01/02/18 6:57 pm
01/02/18 6:57 pm
Joined: Aug 2001
Posts: 5,100
Stone Creek OH USA
R
Rich B Offline

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R

Joined: Aug 2001
Posts: 5,100
Stone Creek OH USA
Details on the stops for the Cannonball are being posted. My local AMCA chapter actually sent an email yesterday with the Ohio stops. Need to get my room reserved so MM & Kevin N have a pit monkey available. cool


Life is too short to drink cheap, bad beer.
Re: 1928 Ariel Model C [Re: Magnetoman] #720915
01/03/18 12:58 am
01/03/18 12:58 am
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Originally Posted by Rich B
Details on the stops for the Cannonball are being posted. My local AMCA chapter actually sent an email yesterday with the Ohio stops.
I smiled when I received the mail with the list of stops and read that all ~100 of us were supposed to treat the information as secret. Sure, with 100 people, like that's going to happen. However, I always keep information confidential until it is clear others have spilled the beans.

Originally Posted by Rich B
Need to get my room reserved so MM & Kevin N have a pit monkey available.
I hope to arrive each evening refreshed, full of energy, and able to socialize well into the evening because no maintenance will be needed on the Ariel for it to be ready for the next day. However, in the unlikely event it doesn't play out quite that way ...

By the time the trip starts in September it will have taken me over a year to prepare for it. And, even then, I won't know for sure when I'm on the starting line whether or not I'm actually fully prepared for what's in store. In contrast, more than once I've left on trips halfway around the world that I didn't even know about until the day before I bought the tickets and left. Traveling to Portland OR is way more complicated than traveling to Phnom Penh.

The heat treatment resulted in ~0.002" of the bend returning, i.e. ~10% of the original bend. So, today I overcorrected the bend by ~0.001" and subjected the rod to the same two hours at 150 oC. Following this I checked it and found the same value as before the heat treatment.

However, I then switched from using a 0.0001 dial test indicator (DTI) to a Mahr Millimess 50 millionths (half of a ten-thou.) dial indicator. I should have used it from the start. A DTI can be a bit more convenient for many measurements, but it's really only accurate for finding 0, and only roughly measures deviations from 0, while a dial indicator gives true readings. Further, Millimess gages have no detectable hysteresis so you can rely on their readings. Anyway, with the Millimess the gudgeon pin is 0.0014" higher at one end than at the other, consistent with the less accurate DTI measurement I made before baking the rod. Now, since I can rely on the measurements to better than 0.0001", this evening I put the rod back in the oven to cook for another two hours at 150 oC to be absolutely sure the rod doesn't have any inclination to rebend.

Interestingly, the heat treatment gave the PB1 bronze a slightly darker, slightly brownish hue that is close to the color of the bronze bush that had been in the rod when I got it.

Re: 1928 Ariel Model C [Re: Magnetoman] #720917
01/03/18 2:23 am
01/03/18 2:23 am
Joined: Nov 2012
Posts: 658
Isle of Wight, UK
K
koan58 Offline
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K

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Posts: 658
Isle of Wight, UK
Hi MM, cracking stuff!

We went to Millimess all of a sudden, is that CMM or similar? What makes it inherently more accurate(without recalibrating?).

In metrology, I often found the shadowgraph very helpful, ok the precision a bit vague, yet when you're dealing with an object, it works quite well.

It surely is important that the bore and stroke is roughly in the right direction, that the finely crafted engine has it's angelic balance, and hopefully tows a few despondents over the finishing line.

I don't know what is allowed, but can you put a drip to your rockers? Dave

Re: 1928 Ariel Model C [Re: koan58] #720963
01/03/18 5:41 pm
01/03/18 5:41 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Magnetoman  Offline OP

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Originally Posted by koan58
I don't know what is allowed, but can you put a drip to your rockers?
I addressed this in a previous post some time ago. The short answer is I don't intend to feed oil to the rockers or valve guides.

Originally Posted by Magnetoman
with the Millimess the gudgeon pin is 0.0014" higher at one end than at the other
It's now 0.0016", but I'm at the limit of measurement uncertainty so call the readings identical at 0.0015", i.e. last night's heating didn't change anything. However, the heating cycles have tightened up the ID of the bush by ~0.0001" (judged by the tighter feel of the pin) so it's good I went through this procedure prior to final honing to size.

The top lands of both aftermarket pistons are 1.25" above the center line of the gudgeon pin so the tilt will bring one side 0.0015" x 1.25"/2.5" = ~0.0008" closer to the cylinder wall than the other (unless combustion pressure equalizes the gap). If it's bored with a 0.005" clearance, i.e. 0.0025" per side, that's ~1/4 of the gap. Looked at differently, and again if combustion pressure didn't center the top of the piston in the bore, it would be as if one side had been bored with a 0.0066" clearance and the other with a 0.0034" clearance.

The skirt of the Gardini piston is 1.5" below the gudgeon pin so it would be a little closer, and a little further from the wall than the top. However, the Omega piston has a much shorter 0.7" skirt on the sides so there certainly wouldn't be clearance issues with it with the present slight bend.

I'll revisit my balance factor calculation to decide which piston to use which, in turn, will tell me by how much to hone the bush. The 0.0014"-0.0016" taper over the 2.5" length of the gudgeon pin corresponds to 0.0006" over the 0.997" width of the bush. I'll mount the rod horizontally on the mill using the mandrel I've been using for these measurements, which will make the small end precisely parallel to the big end. Honing for either piston's pin will remove at least three-quarters, if not more, of this material so there would be no point attempting to straighten the rod further before doing this (and, possibly no point in doing it after honing).


Gearbox update: Hermes tracking shows my gears arrived in the U.S. yesterday afternoon, in Buffalo, NY of all places.

Last edited by Magnetoman; 01/03/18 6:51 pm. Reason: Tracking update
Re: 1928 Ariel Model C [Re: Magnetoman] #720976
01/03/18 8:36 pm
01/03/18 8:36 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Magnetoman  Offline OP

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Absent someone like koan58 finding an error in the following revised balance factor calculations it looks like the original balance factor was 65% and that the Gandini piston will be going in the Ariel:

-- revised ------
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 13/16" bushing to reduce it for a smaller gudgeon pin than the original 1" pin it weighs 267.5 +/-1 g. However, from this subtract 48.2 g for the "excess" weight of the bronze in this smaller ID bushing so it originally would have weighed 219.3 +/-1 g.

-- Current small end weight = 267.5 +/-1 g
-- Original small end weight = 219.3 +/-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, plus the 48.2 g that the current bronze reducing bush weighs more than the original 1" bush. So, to originally balance the crank it would have required 196.6 + 5.5 + 48.2 = 250.3 g.

-- weight to balance crankshaft in its current form = 196.6 +/-0.1 g
-- weight to originally balance crankshaft = 250.3 +/-2 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 originally balance crankshaft without the four 5/16" holes =211.4 +/-3 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:

250.3 + 219.3 / 505.0 + 219.3 = 469.6 / 724.3 = 64.8 +/-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

211.4 + 219.3 / 505 + 219.3 = 430.7 / 724.3 = 59.5 +/-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%

If Gandini piston were used in it without any other changes:
196.6 + 267.5 / 516.5 + 267.5 = 464.1 / 784 = 59.2 +/-0.3%

If Omega piston were used in it without any other changes:
196.6 + 267.5 / 435.0 + 267.5 = 464.1 / 702.5 = 66.1 +/-0.3%

To reduce the balance factor to 65% if using the Omega piston would require reducing the required balance weight by 7.5 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. 3/16" deep each. If I did this I would carefully and incrementally make any such changes only after assembling the flywheel and checking the balance.

Last edited by Magnetoman; 01/21/18 8:18 pm. Reason: corrected math error that affected results
Re: 1928 Ariel Model C [Re: Magnetoman] #721051
01/04/18 3:17 pm
01/04/18 3:17 pm
Joined: Nov 2011
Posts: 4,649
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Magnetoman Offline OP

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Magnetoman  Offline OP

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Originally Posted by Magnetoman
... the ODs of the three pins ... old one that was in Ariel 0.8112", Gardini 0.8115", and Omega 0.8122".
Since it looks like I'll be using the Gardini I honed the bush for it. Should I change my mind the hole can be made larger for the Omega easier than it could be made smaller. Also, I fussed some more with the bend in the rod, finally getting it down to 0.0005" over the 2.5" of the gudgeon pin.

I couldn't find any specs on the allowable bend for connecting rods of any kind, let alone the one in a 1928 Ariel, but I did find that Sunnen sells a fixture(*) for measuring bends that certainly isn't any more precise than my setup. Their fixture includes a long steel bar for bending the rod into shape. I can't imagine a crowbar wielded by a mechanic being able to work to extraordinarily high precision, and in any case at the current level of tilt the results of each of my tweaks is more luck than it is skill.

The remaining 0.0005" of tilt I didn't remove (oh, the shame of it...) means the tops and bottoms of the piston will be 0.00025" nearer/farther from the bore than if there were no tilt at all. It's hard to imagine this will be a problem.

(*)TN-111 Rod Aligner. I found a pre-1960s Sunnen manual for this fixture on line that describes how to use light passing through a gap to determine if there is a bend and how to remove it, but it provides no specifications or indication of accuracy. However, my Brown & Sharpe cylindrical square is designed to measure tilt when it is in one orientation so it provides an answer to this. An object 2.5"-long falls between the 0.0006" and 0.0008" contours, i.e. this is the limit of the tilt you could hope to detect in a machine shop by looking at light in the gap between two straight edges. By this measure, if the Sunnen fixture was good enough for rebuilding engines back in the day, the tilt I achieved is at least 50% better than good enough.
[img]http://www.practicalmachinist.com/v...sharpe-master-cylindrical-square-299766/[/img]

Re: 1928 Ariel Model C [Re: Magnetoman] #721094
01/04/18 7:59 pm
01/04/18 7:59 pm
Joined: Oct 2017
Posts: 90
England
G
George Kaplan Offline
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George Kaplan  Offline
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G

Joined: Oct 2017
Posts: 90
England
Hi MM, interesting stuff and I am pretty sure that your rod is straighter than any out there.

Regarding the other jigs that you mention I agree with you that your method is more accurate.

Only a few days ago I read some articles posted by Cotten on Virtual Indian about crank rebuilding and balancing. On the page about "Inspection" I noted a couple of pictures, one showing a vintage Aamco rod alignment gauge and another showing a fixture being used in a press to straighten a rod. Obviously you have straightened yours but if you haven't seen them already then the pictures may be of interest. If you click on the thumbnails they get bigger.

link here: http://virtualindian.org/1techflywheel3.htm#straight

John

Re: 1928 Ariel Model C [Re: George Kaplan] #721098
01/04/18 8:59 pm
01/04/18 8:59 pm
Joined: Nov 2011
Posts: 4,649
U.S.
Magnetoman Offline OP

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Magnetoman  Offline OP

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Joined: Nov 2011
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Originally Posted by George Kaplan
I noted a couple of pictures, one showing a vintage Aamco rod alignment gauge and another showing a fixture being used in a press to straighten a rod.
Thanks very much for the link to that thread. That Aamco gauge is similar in principle to the Sunnen. The fixture for straightening rods is, ahem, a bit agricultural for my tastes.

My process for measuring, and removing, the bend was a case of me reinventing the wheel. Only last night, after having solved my own particular problem, did I think to use google. And then it was just to see if I could find a spec on the acceptable amount of bend. That's when I found the Sunnen fixture. Interestingly, I couldn't find very much at all about rod straightness on Britbike (which must mean everyone who rebuilds their engines simply knows their rods are straight...).

The late Pete R wrote about straightening rods that he liked to achieve 0.002" in 8" (equivalent to 0.00063" in 2.5"). Although he didn't mention how he decided on that figure, from the context it may be that this allows the rod to slip through both connecting rods in an assembled twin engine. His description relies on having an 8" rod that is known to be straight to within a few ten-thou. as well as a tight fit in the small end bush. Still, it's the identical procedure as the one I used, except I used a shorter rod (the gudgeon pin) in combination with a more sensitive gauge to make the same measurement.


Tracking Update: My gears were sighted in Buffalo NY on Tuesday, York PA on Wednesday, and Glendale Heights IL today, so they're coming across the U.S. on a Conestoga wagon rather than an airplane. However, the web site continues to maintain the fiction that "The delivery date of your parcel should be no later than 04/01/2018." Although, in the American way of writing dates, that's April Fools Day, so maybe it is correct.

Last edited by Magnetoman; 01/05/18 4:22 am. Reason: Tracking Update:
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