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#545728 - 05/28/14 6:45 pm Re: 1957 BSA Spitfire Scrambler ***** [Re: Magnetoman]  
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Regarding your bearing journal repair, my company sends parts to be metal sprayed to this place:

http://www.surfacemodificationsystems.com/resources/gallery/

This place can supersonic cold spray or hot spray different alloys and grind to suit. Might be worth a try. They've done wonders for us. We've even sent radial compressor crankshafts to them.

Kevin

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#545841 - 05/29/14 4:00 pm Re: 1957 BSA Spitfire Scrambler [Re: L.A.kevin]  
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Originally Posted By: L.A.kevin
Regarding your bearing journal repair, my company sends parts to be metal sprayed to ...
Kevin,

Thanks very much for this suggestion. I've investigated all commercial variations of metal plating and metal spraying in considerable detail but, unfortunately, neither works for this application. Both types of techniques have lots of uses, but serving as the inner race of a needle bearing isn't one of them.

The only "additive" technique that I don't yet have enough information on to judge is welding using one of several alloys that have the required hardness. However, even though welding would work to provide the necessary surface it brings with it several problems.

The original shaft would have had at least two types of heat treatments after machining. One would have been to give the alloy the necessary strength so it wouldn't bend under the load, and the other would have been to provide surface hardening (e.g. "case hardening") to the area under the needle bearing. If I were to weld it I would then have to heat treat the shaft to restore the strength, and to do that I would have to identify the alloy used for the shaft in order to know how to heat treat it.

Although only a thin layer (~0.01") of hard facing would need to be applied by welding, the actual amount deposited would necessarily end up much thicker than that. Precision grinding would be needed to take it back down to the required diameter. Unfortunately, welding and heat treating would cause distortion, so the shaft would have to be straightened (to within a few thousandths) before it could be ground.

None of the above is impossible, but none of it is easy, either.

Again, thanks for the suggestion, but restoring the original shaft using a hardened sleeve still seems to be the only option for salvaging it.

#548068 - 06/11/14 6:13 pm Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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Recent progress has been slower than usual thanks to some travel. But, I did make an important step forward today.

Earlier this spring someone in the UK sent me some interesting information about Gold Star oil tanks. Unfortunately, this information created a problem for my Spitfire restoration. For some years I've had a NOS oil tank in perfect condition ready to install. What I learned from the new information is the oil tank I've had all these years is incorrect for a 1957 Spitfire.

Sometime around the time my Spitfire was made BSA changed the shape of the outside surface of the oil tank and of the toolbox (which wasn't used on Spitfires) to a more rounded form. The difference in shape is fairly subtle, although quite obvious when the two types of tanks are side-by-side. However, for me, at least, if I'm looking at one of the "flat" tanks all by itself I'm only ~80% certain it's actually a flat one, not rounded. This is why I never could be certain of the shape by looking at the photographs in BSA advertisements.

Anyway, all I've had to go on until now is that the change happened in either the 1957 or 1958 season. Obviously, which of these seasons matters for this restoration. Thanks to the person in the UK I learned that Service Sheet 44 dated October 1957 states "In order to improve the oil flow the internal feed pipe and filter have been modified. The new oil tank is interchangeable providing it is used with the new filter assembly also." Although the shape of the tank changed it kept the same part number of 42-8367 that had been used since 1954. However, the filter part number changed from 42-8334 to 42-8426.

Unfortunately for me, having learned three months ago that the change didn't happen until the 1958 season meant I had to look for a different oil tank. Earlier today I made the swap. The new-to-me older tank has two very tiny dents in it but the metal is otherwise perfect condition. The dents will be easy enough to fill with braze. But, there's more to the story than this.

BSA's use of the word "filter" is interesting. Anything large enough to actually be stopped by the screen (chunks of metal, valve keepers, …) probably would have destroyed the engine already. But, more to the point, I had forgotten that the Service Sheet said the two tanks used different filters and, since the chrome on mine was perfect, I tried to switch them. The later-type filter went into the older tank a few turns but then got progressively tighter. Comparing the filters side-by-side the dimensions appear to be identical, so I made some measurements.

The OD of the 20 tpi threads on the earlier-style filter is 1.051" while on the later-style it is 1.064". Nominally, both are consistent with 1-1/16", but the 0.013" difference in OD certainly would account for the binding. Surely BSA didn't deliberately make threads with a non-standard diameter, so is it possible the earlier-style tanks all had been accidentally made with slightly out of specification tooling, with BSA taking the opportunity of the redesign to make proper threads?

The hole at the end of the filter for the oil pipe is 0.325" for the old-style and 0.375" for the new-style, consistent with a larger diameter internal feed pipe (note: it's non-trivial to measure the OD of a pipe recessed inside a tank, so I haven't tried to do this). The only visible difference is the older-style filters are made with steel screen while the later are brass. This alone would make it possible to distinguish old and new stock, which would seem to be essential. Have any of you with a large horde of pre-unit BSA parts (Boomer, Gordo, …) noticed this before? Is the steel/brass difference an actual difference that can be used to distinguish old and new types of filters? Everyone, drop whatever you're doing, pull those oil filters, and report back with the results of the OD and steel vs. brass.

#548117 - 06/12/14 2:18 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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To confuse matters further, my father had a completely original 59' flash. It had a flat oil tank and did tool box from the factory. They just fitted what they had.


beerchug
#548130 - 06/12/14 4:00 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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To add to the confusion, in the literature for the B33 its stated that new rounded form of oil tank/toolbox was introduced in 1958 together with the alternator. The bigger toolbox was requiered to give space for the rectifier!


best regards

Per
Goldi Clubmans
Goldi Scrambler
Rob North R3
OIF A65
#548199 - 06/12/14 3:33 pm Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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When getting the BB Goldie ready for the rally I switched out the chrome oil tank for a stock original paint flat side tank. Both tanks were not correct for the model, should have a flip cap like the fuel tank for one, but fit the part. All the threaded oil filters I tried were exactly as you pointed out and the one that was in the chrome tank had a tear in it. I thought it was due to the dent that was right next to the fitting where the filter screwed in so I ended up using the filter with the tear that was in the chrome flat side oil tank.

So now, as you have pointed out, I would assume that all my spare oil filters were for the later tank.

BTW, I'm looking for one of the one year only BB swingarm oil tanks. Not only is the cap different but the shape is different. The tee fitting to secure it to the frame at the front edge of the tank
is different and the bracket it attaches to on the frame is welded on and not bolted on. I used the later set-up and had to use a spacer on the tee bolt and it pulls at an angle telling me the fitting on the tank is in a different place than the original tank also.


Sorry for digressing from the original point but I hope that helps.

Bill B...

Last edited by Boomer; 06/12/14 3:36 pm.

Boomer
#548236 - 06/12/14 9:25 pm Re: 1957 BSA Spitfire Scrambler [Re: Boomer]  
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Originally Posted By: Allan Gill
my father had a completely original 59' flash. It had a flat oil tank and did tool box from the factory.
While anything is possible, not everything is equally probable. I tend to discount such anecdotes since there are a number of more plausible explanations, e.g. whoever sold the bike to your father told him it was original, and might have even believed that, but had forgotten he or an earlier owner had installed a replacement.

Originally Posted By: Allan Gill
They just fitted what they had.
All the evidence I've seen over the years points to things not being quite as random or chaotic as that at the factory. In the same vein, the late John Gardner told me that although people commonly say that Gold Stars "were configured any way you wanted them" by the factory, nearly all machines where he could trace the actual history were supplied exactly as specified in the catalog.

Originally Posted By: Per B
To add to the confusion, in the literature for the B33 its stated that new rounded form of oil tank/toolbox was introduced in 1958
Rather than adding, it subtracts from the confusion. A 1958 date is what is given in that Service Sheet I referred to in an earlier post, so your comment on the B33 is consistent with that. Thanks for mentioning this.

Originally Posted By: Boomer
All the threaded oil filters I tried were exactly as you pointed out
Very interesting. Finding this out-of-spec difference in thread diameter for the earlier tanks is beginning to look like it might be a micro-discovery. I'll post more on this tomorrow, along with photographs and dimensions to easily allow distinguishing between the two versions of filters. Meanwhile, the next time you wander out to your workshop please look to see if the filters that you now think are the later ones have brass or steel screens.

#548331 - 06/13/14 4:44 pm Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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At the left of the next photograph is the earlier-type filter used in 1954-1957 flat-sided oil tanks and on the right the later-type for rounded-side tanks introduced for the 1958 season. Both filters are the same 2-1/2" length from the sealing surface to the end so it would be difficult to distinguish between them by eye alone (unless we obtain more information showing that a steel mesh was always used on the earlier ones and brass on the later). However, an unknown filter easily can be identified using a 3/8" (or 9.5 mm) drill bit because it will fit in the hole at the end of the later-type filter but won't in the smaller hole of the earlier-type.



The next photograph shows the end of the earlier-type filter in greater detail (the later-type is the same, but with a slightly larger hole).



As discussed below the slightly smaller diameter of the threads on an earlier-type filter would allow it to be installed in a later-type tank if the hole in the end were enlarged so I imagine such modified filters are to be found. However, as can be seen, the inner surface of the ID is smoothly rolled over. This wouldn't be the case if examining an earlier-type filter that someone had modified to make fit a later tank by drilling it for the larger pipe.

As mentioned in a previous post, the OD of the 20 tpi threads on the earlier-type filter is 1.051" while on the later-type it is 1.064". Both are consistent with 1-1/16" (i.e. 1.063"), but the 0.013" difference in OD certainly would account for the binding when trying to use the later type of filter with an earlier tank if the threads in the tank also were made the same amount out of spec.

I keep an old edition of 'Machinery's Handbook' (15th, 1955) for information on obsolete threads since much of the relevant content on these fasteners was dropped from more recent editions. The 1-1/16" of this oil filter isn't a standard BSW, BSF or CEI fastener size, but the allowed tolerance for 1" and 1-1/8" BSW and BSF is +0"/-0.008". The difference of -0.013" I found for the earlier filter is well outside this. Also, the fact the later-style filter has the correct diameter lets it be used as a "plug gage" to test the threads on the old-style tank. The fact this "plug gage" binds in the hole says the threads in the tank also are out of spec.

Surely BSA didn't deliberately make threads with a non-standard diameter, so this seems to indicate the earlier-style tanks all had been accidentally made with tooling that was slightly out of specification. The fact the later filter is of the proper diameter and pitch but doesn't fit the earlier tanks indicates that for the four years that the earlier parts were made it was with tooling that was out of spec. by ~0.005". It appears BSA took the opportunity to correct this mistake when they introduced the new rounded tank with 1/16" larger internal pipes for the 1958 season. Still, this discrepancy is a bit puzzling since the threads in the tank would have been made with a tap so this means the taps BSA used were out of spec. But, no matter what, somewhere some company's quality control department didn't do their job properly.

A few other measurements: the internal pipe in the oil tank is recessed by 1-3/4" which makes it difficult to accurately measure its OD. This is shown in the next photograph.



(note: the residual oil isn't defying gravity; the tank was at an angle on the table and I rotated the photograph to give it the proper orientation). Although I could bore a series of holes in the ends of Al rods to make female plug gauges to determine the OD fairly accurately, there is no need for such accuracy. Instead, using drill bits to judge the approximate OD of the pipe in the old-style tank shows it is ~5/16" (~0.313"). The ID of the end of the old-type filter is ~0.328" so the annular clearance is ~0.008". The OD of the pipe in the rounded tank is ~3/8", and the ID of the new-type filter for that tank is ~0.377", so again the annular clearance is a few thousandth of an inch.

#548615 - 06/15/14 12:05 pm Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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Thanks MM
After a lengthy discussion on the oil tank filter issue, I have now convinced my wife that I am indeed crazy.
A previous post mentioned "Service Sheet Number 44". I have a poor copy of a "BSA Parts Service Bulletin"(unable to read the date). It also mentions #44. I don't have a working scanner, or I would post it. It states the following:

When requesting replacement Oil Tank Filters, it is important that they are ordered as follows:-

For machines prior to the following Frame Numbers:-

A Group Frame Number EA7-12641
B Group Frame Number EB31-8252
Gold Star Frame number CB32-6667
Use Filter assembly Part Number 42-8334

After the above frame numbers use Filter assembly Part Number 42-8426

The latest type Oil Tank part number 42-8367, can be used as a replacement on all Models provided that the new Filter assembly Number 42-8426 is also used.

Service Sheet Number 44 also refers to this change.

C/R.A.B. BSA Motor Cycles Limited, Service Dept., Birmingham, 11.


Perhaps you could use your dispatch date and cross check the dispatch date on EA7-12641

#548717 - 06/16/14 1:28 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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l
Originally Posted By: Magnetoman
Originally Posted By: Allan Gill
my father had a completely original 59' flash. It had a flat oil tank and did tool box from the factory.
While anything is possible, not everything is equally probable. I tend to discount such anecdotes since there are a number of more plausible explanations, e.g. whoever sold the bike to your father told him it was original, and might have even believed that, but had forgotten he or an earlier owner had installed a replacement.
Originally Posted By: Allan Gill
They just fitted what they had.
All the evidence I've seen over the years points to things not being quite as random or chaotic as that at the factory. In the same vein, the late John Gardner told me that although people commonly say that Gold Stars "were configured any way you wanted them" by the factory, nearly all machines where he could trace the actual history were supplied exactly as specified in the catalog.
Further on this, an undated two-page Hap Alzina information sheet states in all CAPS that:

"EACH BSA MOTORCYCLE HAS CERTAIN STANDARD SPECIFICATIONS AS BROUGHT INTO THE UNITED STATES AND THESE AND NO OTHER ARE THE SPECIFICATIONS AT TIME OF SALE."

It goes on to give as an example that:

"What this means, in effect, is that a Catalina Scrambler is a Catalina Scrambler… The Clubman engine is not available in the Catalina frame … a Catalina is not available with the Clubman carburetor and Clubman cams, etc."

Another undated two-page Azina bulletin deals with "Subject: Special B.S.A. Motorcycle Orders." Again, in all CAPS it emphasizes that:

"GENERALLY SPEAKING - SPECIAL ORDERS ARE NOT POSSIBLE OF ACCEPTANCE OR FULFILLMENT"

It goes on to say that although orders for Gold Stars with any of the various specific allowable factory options "...can, in a technical sense, be accepted by the Works...", it immediately cautions in all CAPS that:

"SUCH ORDERS ARE APPROXIMATELY FIVE TO SIX MONTHS DELIVERY FROM THE DATE OF ORDER PLACEMENT AND ARE FIRM, NON-CANCELABLE ORDERS FOR THE DEALER'S ACCOUNT THAT MUST BE ACCEPTED BY THE DEALER ON ARRIVAL."

The bulletin advises the dealer to try to "...reshape the customer's desires to some form of readily available equipment." Failing that, the dealer should get a very large deposit because the dealer will be charged in full for the special-order bike once it does arrive. This Alzina bulletin confirms that while in principle Gold Stars could be ordered with a wide variety of optional equipment, at least in the U.S., bikes that deviated from the standard catalog specification would have been unusual.

The bulletin also advises the dealer to agree to make any changes the customer wants to any bike in his shop, at the customer's expense, since "This gives you a brand-new, saleable item on your shelf free of cost…" It doesn't take much imagination to realize how such parts swaps could result in bikes leaving dealers' shops with new, but incorrect items previously taken from other bikes, and for buyers to incorrectly think that is how their brand-new bike came from the factory.

Originally Posted By: BritTwit
After a lengthy discussion on the oil tank filter issue, I have now convinced my wife that I am indeed crazy.
All I can say is, my wife is several decades ahead of your wife. However, you're probably not giving your wife nearly enough credit for having realized this about you long ago.

Originally Posted By: BritTwit
I have a poor copy of a "BSA Parts Service Bulletin"(unable to read the date).
Perhaps you could use your dispatch date and cross check the dispatch date on EA7-12641
That would be Bulletin No. G.5 dated June 1958. Unfortunately, I only have A10 records for 1957 Spitfires and those frames are all in the CA7A-xxxx range. However, the high EA7 number indicates the switch on A10s came sometime into the 1957 model year. The same for the Gold Star and the B-group numbers.

I should say that, all by itself, Bulletin G.5 doesn't determine what oil tank should be on a 1957 Spitfire. The wording says a new filter had been introduced as of the June 1958 date, and it also says the latest type of tank uses that filter, but it doesn't actually address how many different tank(s)/filter(s) might have been used in previous years. However, the wording is consistent with what the other information says, i.e. that my Spitfire uses the flat oil tank.

#548723 - 06/16/14 2:25 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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Just been looking back through this thread at the photos you posted, some catalogue images are hard to tell, the the cutout of the super rocket next to the scrambler seems spar any that they are both flat sided tanks - the curve on the oil tank seems too sharp to be the rounded type.

Do you have anymore images?

Enjoying your progress bigt


beerchug
#548975 - 06/17/14 4:11 pm Re: 1957 BSA Spitfire Scrambler [Re: Allan Gill]  
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Originally Posted By: Allan Gill
Do you have anymore images?
Enjoying your progress
Thanks for your comment. I've posted every image of this machine that I've found in 20 years of searching. But, since I intend for this thread to be the most comprehensive collection of information possible, you can count on me to post anything new that might turn up in the future.

#549708 - 06/22/14 11:16 pm Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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As soon as I received the SCT2 gearbox three years ago I ordered all the bearings and bushings for an RRT2 so they would be on hand when I was ready to being work. However, when I started on the gearbox in earnest a few months ago I looked at the parts and wasn't happy with everything I found. For example, the bearing for the sleeve gear should have crowded rollers for heavy loads but the Japanese-made one that was supplied is for high speed operation, with only half the number of rollers and a plastic cage. These are shown in the next photograph, with the Japanese bearing at the left and a proper Torrington bearing on the right



The not-quite-right bearings came from a supplier in England (not Autocycle). But, thanks to eBay, I now have several lifetime's worth of the proper NOS gearbox needle and ball bearings. By the way, note the presence of the oil hole in the housing. As normally supplied by Torrington there is no oil hole and whether or not it is present the number stamped on a Torrington bearing itself does not have an "-OH" suffix. The catalog states that only on the box containing the bearing will "-OH" be printed to denote that the contents have the oil hole option.

As mentioned in an earlier post, the mainshaft supplied by Autocycle meets all of the specifications except for the roughness of the shaft immediately under the needle bearing which does not meet modern standards. I measured an average roughness (Ra) of 15-16 micro-inches whereas modern standards call for a maximum of 8 micro-inches. I should say that a c1970 Torrington catalog lists the maximum roughness as 16 micro-inches so the shaft actually does meet those older requirements.

Without going into too much detail, the way roughness values are defined the maximum peak-to-valley roughness Rz will be quite a bit greater than the average roughness Ra. In my case Rz = ~130 micro-inches (~3.5 microns) while Ra = 15 micro-inches (~0.5 microns). To knock down those peaks, which also will reduce Ra, requires polishing with an abrasive of size somewhat smaller than Rz. I decided to start with 1 micron grit and to go to 0.5 micron after that if necessary (note: most people consider Simichrome to be a fine polishing compound but it is 8-10 microns). I hope mixing the inch/metric units doesn't cause confusion for anyone.

I polished for 30 seconds with the 1 micron abrasive and measured the roughness to see what progress I had made. The principle being, I'd rather find out as early as possible if metal was being removed faster than expected. However, the change in roughness, if any, was small, so I polished for another 2-3 minutes, measured again, and found Ra = 8 micro-inches (Rz = ~50 micro-inches). The result is shown in the next photograph, with the polished region for the needle bearing quite apparent:



Since at this point polishing had reduced Rz from its original ~3.5 micron value to about that of the 1 micron grit size further progress would require changing to a finer grit abrasive. However, since Ra now met the 8 micro-inch specification given in modern catalogs, I was done.

Last edited by Magnetoman; 06/23/14 11:37 pm. Reason: fixed a typo
#549714 - 06/23/14 4:20 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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MM, this is intesting info for me, the bearings in the gearbox of my goldie are similar to the japanese bearings as shown on the left in your pic.

According to my bearing supplier, Torrington is no longer in business, and he was unable to supply the correct needle bearing with the large nuber of needles.

Should I be worried ? so far the 'íncorrect' type ofbearing gave no problems, athough i have not done many miles with it yet.


Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
#549717 - 06/23/14 5:17 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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Quote:
Torrington is no longer in business



Torrington is no longer independent as its owned by Timken but its still around. I would stay away from people spouting such rubbish.

#549742 - 06/23/14 9:55 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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http://www.timken.com/en-us/about/NewsRoom/Stories/Pages/TimkenSellNRBBusinesstoJTEKT.aspx

In 2009 Timken sold the needle bearing business to a holding company that sells needle bearings under the Koyo-Torrington brand name. We are still able to get made in USA Koyo-Torrington needle bearings.


#549845 - 06/23/14 11:35 pm Re: 1957 BSA Spitfire Scrambler [Re: Peter R]  
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Originally Posted By: Peter R
the bearings in the gearbox of my goldie are similar to the japanese bearings as shown on the left in your pic. ... Should I be worried ?
I won't tell you to be worried. But, I also can't tell you otherwise. The problem is I can't think of any way to model the side thrust the bearing will be subjected to. The type of bearing you have has half the rollers so the pressure on them, the race, and the shaft is twice that of a crowded roller bearing. We know that a crowded roller can withstand the side thrust without exceeding the yield strength of any of the components. But, perhaps it is overspecified by a factor of 4x, in which case the type of bearing you have is still 2x stronger than it needs to be. In which case, you're fine. But, a crowded bearing race might be overspecified by 50%, in which case you will have problems in the future.

Another issue is quality. Torrington bearings are a known quantity. Further, they are made to published specifications that require being pressed into housings of prescribed diameter to compress the race just the right amount to give the required clearance with the shaft. Think about all the discussions of C2 vs. C3 etc. ball bearings to be used on engines. Although all these have nominally the same OD and ID, one clearance will result in a noisy engine while another might cause it to seize. What about the unknown Japanese bearing? Even if made to strict metallurgical standards, without knowing what the dimensional tolerances are there's no way to meet them.

So, sorry, I can't tell you not to be worried.

#549857 - 06/24/14 3:24 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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Peter R Online content
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OK, thanks for the reply, I will replace the bearings in the not too distant future, for the sake of piece of mind if nothing else..
I will contact Autocycle to ask if they can supply the correct bearings.

Last edited by Peter R; 06/24/14 3:24 am.

Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
#549863 - 06/24/14 5:11 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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There are other considerations on needle bearing life other than crowded vs caged having different numbers of rollers. A caged needle roller will perform better at high speeds than a crowded bearing as the cage keeps the rollers from rubbing against each other. So low speed high load is best handled by crowded, low load high speed is handled best by a caged roller.

As for the c1, c2 equivalent ie the ISO/DIN std on ball and roller bearings there are a few for needle rollers too.


http://www.iso.org/iso/home/store/catalogue_tc/catalogue_tc_browse.htm?commid=45572

#549961 - 06/24/14 9:49 pm Re: 1957 BSA Spitfire Scrambler [Re: kommando]  
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I should have mentioned the Torrington part numbers in an earlier post. The reason I ordered the bearings from a motorcycle parts supplier in the first place is I hadn't taken the gearbox apart yet at that time so I didn't know what bearing was required for the SCT2/RRT2 sleeve gear. Now I do. Anyway, the required Torrington bearings (with dimensions, in case you need to locate an alternative manufacturer) are:

Sleeve gear (only used on the SCT2 and RRT2)
B-1314-OH
13/16" ID, 1-1/16" OD, 7/8" wide

Inner cover (used on both 'T' and 'T2' gearboxes)
B-1212-OH
3/4" ID, 1" OD, 3/4" wide

The bearing needed for the main gearbox housing depends on whether or not a separate, slightly convex, 'cap' is pressed in at the outer end of the hole in the housing to seal the oil in. If the housing has such a cap, then an open ended bearing is used. If not, than one with a closed end is required.

Main gearbox housing (used on both 'T' and 'T2' gearboxes)
B-1112-OH (open ended)
or
M-11121-OH (closed end; note, the extra '1' at the end of the no. isn't a typo)
both are 11/16" ID, 7/8" OD, 3/4" wide

#550065 - 06/25/14 4:12 pm Re: 1957 BSA Spitfire Scrambler [Re: Peter R]  
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Originally Posted By: Peter R
so far the 'íncorrect' type ofbearing gave no problems, athough i have not done many miles with it yet.
Looking at the photo in my post of 6/22 the Japanese bearing has ~16 rollers in it and the Torrington ~32. Using those numbers in a formula in my c1970 Torrington catalog, the Basic Dynamic Capacity (BDC) of the Japanese bearing will be 63% of that of the Torrington if it is of the same quality and used under identical operating conditions. So, cutting the number of rollers in half significantly reduces the load capacity of the bearing although doesn't quite cut it in half. This means that as long as the crowded roller bearing that BSA used was overspecified by a factor of ~2x you wouldn't have to worry your caged bearing would fail under the load. Of course, we don't know if that 2x safety factor was built in, so you do have to worry about this.

Since you already need to worry, to give you a second thing to worry about, another effect of a reduced number of rollers is a reduction in the lifetime of the bearing. Using another formula in the catalog, reducing the BDC to 63% reduces the lifetime to 21% for an identical load. To put this in practical terms, if the Torrington bearing that BSA used for this purpose would have lasted, say, 20,000 miles before needing replacing, a caged bearing of the same quality would have lasted only ~4,300 miles.

There are so many unknowns involved (e.g. was a gearbox run low on oil for some number of miles?; was incorrect weight oil used?; was the oil never changed?; did the previous owner repeatedly shock-load the layshaft by downshifting without using the clutch?; etc.) that I doubt if there is any data on the expected lifetime of the needle bearings on the layshaft of a BSA gearbox. But, I'll go out on a limb and speculate that in the ways our gearboxes are commonly (mis)used, 20,000 miles is a reasonable lifetime to hope for from an original bearing. If this is the case, (mis)used in the same way a caged bearing of the same quality is only going to last 4,300 miles. But, irrespective of whether or not 20,000 miles is a reasonable expectation from a high quality, crowded roller bearing in this application, you won't get any more than ~20% of the mileage from any caged roller bearing. And less -- perhaps far less -- from a caged roller bearing of unknown quality.


#550074 - 06/25/14 5:52 pm Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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MM, thanks very much for your reply, your input is greatly appreciated.
I understand that the integrity of the gearbox will be seriously impaired with the bearings that I am currently using, and will certainly exchange them for the correct "crowded" needle bearings before something goes seriously wrong.
Thanks also for providing the correct part nrs in your posting above.


Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
#550254 - 06/27/14 1:26 am Re: 1957 BSA Spitfire Scrambler [Re: Peter R]  
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Originally Posted By: Peter R
I understand that the integrity of the gearbox will be seriously impaired with the bearings that I am currently using, ...
I can't say I've done a comprehensive survey of all suppliers, but it appears the incorrect type of bearing is commonly sold. However, given the calculations outlined in my previous post, they still should last long enough that most owners won't realize it was the fault of the supplier, not of their treatment of the gearbox, that resulted in failure after relatively few miles.

#550295 - 06/27/14 2:41 pm Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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I concour with the incorrect parts being shipped. I used to build a few bantam engines at one time ( amongst others ) and very often the caged roller would be sent out for use at the little end - I refused to use them and since only bought little end bearings which I could see before I bought, and these weren't Britbike suppliers I was buying them from! ( well the incorrect bearings DID come from BB suppliers)


beerchug
#552138 - 07/10/14 2:14 am Re: 1957 BSA Spitfire Scrambler [Re: Magnetoman]  
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I only managed to make small progress since my last post due to a trip to Turkey. But, thanks to what felt like countless hours in transit I did get one thing done that I will need when it comes time to fabricate the exhaust pipes. The extra-long pipes are special to the Spitfire and none have turned up in 20 years of searching so I'll have to weld my own. To do that requires knowing their length and geometry which the following photograph shows.



As soon as I measure the length from the swinging arm pivot to the shock mount the length and amount of bend will be determined by the information on the photograph. I have three pairs of A10 pipes to work with (all with dents, scrapes and rust) so I should have more than enough raw material to work with. However, I'll complete work on the gearbox before doing anything else.

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