The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Greybeard on 27.10. 2017 11:20

Title: Plain bearing vs roller conversion
Post by: Greybeard on 27.10. 2017 11:20
I've obtained permission from Barry Huron from Ontario to copy and post his comment on Facebook. He says he has more to say about this in Real Classic magazine, October 2017.
Barry was answering a chap who was trying to find a cheaper way to get a roller conversion than SRM.
 
...modern oil is far better than the old stuff and tolerances for bearings has not changed since the beginning of the industrial revolution. the plain bearing is much stronger and more durable than a roller and is universally used in all engines. the fly in the ointment is the sludge trap in the crankshaft-it is always the left big end that siezes due to it filling up if there is any oil in the tank. i have an A65 engine that ran just fine with .009" clearance and .035" end play so it is clearly a good design. the idea that a modification of dubious durability worth as much as the whole bike is more a matter of marketing hype than engineering excellence. clean out the sludge trap and add a filter and it is a bulletproof design. spending money on a modification will only win you garage races and ultimately devalue a bike in the eyes of the rivit counters that have the money to buy it at your estate sale.
Title: Re: Plain bearing vs roller conversion
Post by: JulianS on 27.10. 2017 12:21
Interesting point of view.

I went SRM conversion back in 1984. Got fed up with end float and poor quality pattern bushes. Replaced the combined needle roller/ball thrust bearing in 2009 after many many miles. So for me the durability is proven and not dubious. Would not want to go back to a bush.

First photo is one of the horrors which persuaded me to convert.

On the other hand see second photo the defence of the Vandervell bush from BSA back in 1964. Unfortuately Vandervell dont make them anymore.

So it is all a matter of personal choice.
Title: Re: Plain bearing vs roller conversion
Post by: Rex on 27.10. 2017 13:02
A similar argument often rages among unit Triumph enthusiasts, until someone always points out that Ted Simon (he of "Jupiter's Travels") rode around the World on a bush motor, and with no problems.
How much bigger test can there be?
Title: Re: Plain bearing vs roller conversion
Post by: Clive54bsa on 27.10. 2017 20:34
I've done 2 engines with the SRM conversion and 1 without. In hind sight I think I wasted my money on the conversions.
Firstly I'm in So Cal U.S. so obviously the freight charges add a lot to the total cost, and secondly I had one of the SRM bearings fail, I found little shiny flecks in the oil and after removing the timing cover, discovered the small ball bearings were breaking up after 13,000 miles. I sent the bearing back to SRM, as I thought it might be of interest to them and within a month I got a new one in the post...no note. I had already purchased a new bearing from a supplier in Canada, so now I have a spare.
My local bearing supplier told me that a 1% failure rate in bearings is quite common, so I suppose I was just unlucky...didn't play the lottery that week.
Title: Re: Plain bearing vs roller conversion
Post by: wortluck on 27.10. 2017 20:48
Back in the 50s and 60s, bikers used thick coffee and washing up liquid for oil, never changed it only topped it up, and never fitted fancy modern filters - just made do with the tea strainer to filter out the chunks of metal.  Nowadays, we use engineered oil and change it in half the recommended time or less.  Some of us have magnetic sump plugs and are meticulous at cleaning everything.  Do we really need to change the original bikes.  I'm not fitting a filter, just changing the oil more often - and no conversions!!

Rant over - with the winter lay-up coming, do I leave the old oil in the bike and change it when the rabbits start breeding, do I change it now and leave the new oil in the bike, or do I drain the whole lot off and leave it empty? *dunno2* :-\
Title: Re: Plain bearing vs roller conversion
Post by: Triton Thrasher on 27.10. 2017 20:52
Many A65s had disastrous problems shortly after new purchase. Sloppy factory build may have contributed to that.

The Devimead/SRM end feed conversion had a market because of all those disgraceful A65 breakdowns. The similar conversions for A10s and unit Triumph 500s were tacked on to the range and people bought and keep
on buying them.
Title: Re: Plain bearing vs roller conversion
Post by: t20racerman on 27.10. 2017 21:26
There is simply no comparison - the SRM conversion is far, far superior to the original bush. If you ride an A10 or A7 in a low level of tune and are not prone to thrashing it, then fine, the bush will usually suffice. Once BSA uprated the power though on the late A10s and the later unit twins, the bush was at the absolute limit of acceptability. BSA had loads of warranty claims, and many unimpressed customers. The bush can't cope with high revs & power.
My A10 is tuned up, and has been thrashed continuously for the past 34 years. The bush lasted two years, but the SRM conversion has managed 32 years so far - with one replacement a few years back as I'd stripped it anyway.
My bike does a lot of miles, cruises at 80mph on faster roads, and gets revved high through the gears all the time. No bush could cope with what I've put my engine through. You might consider me a philistine for treating my BSA like this, but it's built to take it. If you only potter round on yours (and there's nothing wrong with that) then don't waste your money on an SRM conversion. If you want a bullet proof engine like mine, get the SRM conversion, and nitride your crank at the same time.
Title: Re: Plain bearing vs roller conversion
Post by: wortluck on 28.10. 2017 10:43
Point taken t20racerman - can't argue with that!
Title: Re: Plain bearing vs roller conversion
Post by: coater87 on 28.10. 2017 14:55
Back in the 50s and 60s, bikers used thick coffee and washing up liquid for oil, never changed it only topped it up, and never fitted fancy modern filters - just made do with the tea strainer to filter out the chunks of metal.  Nowadays, we use engineered oil and change it in half the recommended time or less.  Some of us have magnetic sump plugs and are meticulous at cleaning everything.  Do we really need to change the original bikes.  I'm not fitting a filter, just changing the oil more often - and no conversions!!

Rant over - with the winter lay-up coming, do I leave the old oil in the bike and change it when the rabbits start breeding, do I change it now and leave the new oil in the bike, or do I drain the whole lot off and leave it empty? *dunno2* :-\

 Used oil has some acidic qualities, I believe this is a byproduct combustion.

 I dont think a three or four month lay-up would make any difference, but I would change it out than store it. Its one less thing to do when you bring it back out.

 Lee

Title: Re: Plain bearing vs roller conversion
Post by: muskrat on 28.10. 2017 15:20
I'm with t20. My A10 Cafe gets flogged (raced for 9 years) and no problems with the conversion. My A7 plunger is on it's third bush and needs replacing now.
Cheers
Title: Re: Plain bearing vs roller conversion
Post by: coater87 on 28.10. 2017 16:48
 The big advantage I can see from a distance is the fact the bearing can be changed by anyone.

 I can get my own bushes close by setting up in the mill, but I don't own a Sunnen hone much less the mandrels needed to do the job correctly.

 I think if I was to ever do another A10 motor, I may do this conversion and think deeply about converting the rest of the bushings over to bearings.

 Dont get me wrong, there is nothing at all wrong with bushings. Its just that if your not set up with the right tooling it gets pricey quickly and you have to rely on other peoples time line.

 Lee
Title: Re: Plain bearing vs roller conversion
Post by: BSA_54A10 on 29.10. 2017 13:58
To a large extent, the problem wit the bush is way way way over rated.
back when we were young and used the bikes as daily transport we were always looking for reasons not to pull down the engines and accepted that they missed a bit , dropped some oil, blew a bit of smoke, vibrated and did not throw the front wheel skyward the instant you looked at the twist grip.

Now days when they get used once every forest fortnight we are desperate to find reasons , any reason to tear the engine apart.

Now my first BSa was a horrid mix of long & short stroke parts, over carbed & filled with pistons that made a church steeple look flat.
I thrashed that bike without mercy for 3 years till eventually it locked a rod , chewed out the barrel spigot then proceeded to rip the barrels off the flange.

Now there is no such thing as an engine that can not be made to work better by spending a lot of money on it, the question is , do you need to spend the money & will it be good value.
While there were quite a few warranty claims attributed to the plain bush on A 65's. remember that engine is putting out near double what a std A 10 puts out and is a high reving over square engine and not a A7.10 that developes peak power way before an A 65 gets onto its cam.

 
Title: Re: Plain bearing vs roller conversion
Post by: gpo746 on 29.10. 2017 14:31
The big advantage I can see from a distance is the fact the bearing can be changed by anyone.


 Lee

The fact that you could do your own bearing and could be changed by anyone with basic tools is a BIG advantage. The pain of having to strip down and then find an engineering company to hone and prat about with a plain bush..
What about cost???... How much does it cost to get a bearing conversion done? What is the difference in price Plain vs Bearing?
Title: Re: Plain bearing vs roller conversion
Post by: Black Sheep on 29.10. 2017 15:19
My Star Twin has now clocked up 40 years of use and abuse and absolute thrashing on its plain bearing. Failures of plain bearings are not a design fault. So much is down to the bush and how it is fitted. My wife's A10 has had even more years of thrashing (she's not a delicate flower when it come to the throttle hand) and has never had a problem with the timing side bush.
A lot of this discussion is down to personal experience or belief. It does worry me slightly that new BSA owners feel they must go for the SRM conversion before anything else. It's a lot of money for something that they most likely don't need. 
If you are going to hammer an A10, I would look to the ageing con rods as the most likely components to fail.   
Title: Re: Plain bearing vs roller conversion
Post by: gpo746 on 29.10. 2017 19:25
My Star Twin has now clocked up 40 years of use and abuse and absolute thrashing on its plain bearing. Failures of plain bearings are not a design fault. So much is down to the bush and how it is fitted. My wife's A10 has had even more years of thrashing (she's not a delicate flower when it come to the throttle hand) and has never had a problem with the timing side bush.
A lot of this discussion is down to personal experience or belief. It does worry me slightly that new BSA owners feel they must go for the SRM conversion before anything else. It's a lot of money for something that they most likely don't need. 
If you are going to hammer an A10, I would look to the ageing con rods as the most likely components to fail.

I do not intend hammering my A7 . I just want it right and reliable (as can be!) . I will use it , not mollycoddle it , defo not thrash it. I may stick to a plain bush then......BUT..it is getting the RIGHT part (C&D Autos?) AND having someone who KNOWS how to machine it correctly .That is my concern.
Title: Re: Plain bearing vs roller conversion
Post by: Bsareg on 29.10. 2017 22:15
The original bushes work fine but a few years ago there were a lot of two piece bushes about with poor fixings between the inner and outer. This allowed the inner to turn and close off the oil ways.  I always fit solid bushes then  blue and hand scrape them into  line. Not the recommended way but has proved reliable on all the families a10s (some of which get a right hammering by the young-uns.
Title: Re: Plain bearing vs roller conversion
Post by: Greybeard on 29.10. 2017 22:55
I always fit solid bushes then  blue and hand scrape them into  line.
I had to learn how to do that when I fitted a new crankshaft to my Austin Seven. The big ends were white metalled and had to be hand scraped to fit the journals. I hadn't realised one could do that with the BSA shaft bushes.
Title: Re: Plain bearing vs roller conversion
Post by: Clive54bsa on 30.10. 2017 00:29
 I agree with gpo746, both my A10s cover barely 2000 miles a year, so the bushing is probably adequate, especially as I change the oil, which is still relatively cheap, approx every 500 miles. But if you intend to use your A10 as a daily rider, covering many thousands per year or racing then perhaps the conversion is for you, unless you have a bearing failure as I did.
Title: Re: Plain bearing vs roller conversion
Post by: BSA_54A10 on 30.10. 2017 07:02
My Star Twin has now clocked up 40 years of use and abuse and absolute thrashing on its plain bearing. Failures of plain bearings are not a design fault. So much is down to the bush and how it is fitted. My wife's A10 has had even more years of thrashing (she's not a delicate flower when it come to the throttle hand) and has never had a problem with the timing side bush.
A lot of this discussion is down to personal experience or belief. It does worry me slightly that new BSA owners feel they must go for the SRM conversion before anything else. It's a lot of money for something that they most likely don't need. 
If you are going to hammer an A10, I would look to the ageing con rods as the most likely components to fail.

Yes a sore point there.
More than 1 person I know was ardent that their bike would grenade without an SRM conversion but were more than happy to put the old rods back in without as much as a simple dye pen test for cracking.
Title: Re: Plain bearing vs roller conversion
Post by: Sluggo on 30.10. 2017 17:01
Horses for Courses,,,,,,,, But overall I agree with T20Racer,

Biggest REAL issue in my experience with many rebuilds of British engines, (Not many on A10s admittedly) is that the process of "Blueprinting" is the most important, followed by sensible time change parts replacements with basis of metallurgy and physics.

Blueprinting is the process of checking every surface and dimension and optimizing it to the best possible specs.  Not easy, but in my experience (And I am certified in Aerospace inspection and repair (FAA-A&P as well as multiple ratings in NDT-Non Destructive testing) is that many of these old bikes were built to rather loose and sloppy tolerances.  For their day they were pretty good and overall I think 1950s BSA stuff was some of the best on the market.  But lets be honest. Every manufacturer builds things to a cost, not an engineering/machining  ideal.     Secondly after 70 some years, dimensions change, especially aluminum castings.  In the BSA engines I have checked I have found significant dimensional changes that I am certain did not leave the factory with.  But I have also found some really sloppy work as well that was "Good enough to go out the door" and many that WERE NOT good enough to be installed on a bike.   
**Norton was probably the worst offender in that dept, and knowingly shipped junk that had to rectified at the dealer level, But all Brit manufacturers were guilty at times of this. 

Something that Edward Turner begrudgingly acknowledged after returning from a trip to Japan.

But I wholehearted agree on aged rods and other bits.  I bring it up often but in Stan Shentons book "Triumph Speed tuning", Triumphs engineers stated that the service life for a Triumph connecting rod was ONE,, thats 1,.... 500 mile  race.  Its simply physics that a alloy rod has a limited service life, Math is Brutal!

As to the specifics of a bush vs bearing, I have come to a middle of the road approach.  I agree that a low stressed engine will run fine on a bushing if tolerances are kept in line.  I also talked to a lot of racers who spent decades thrashing these old engines on their insights.  I believe that the bearing conversion done properly is a sound modification.
Triumph ran the early 500 unit twins on bush but they were not without failures (same with the gooseneck frames prior to 67).  As the 500 unit gained power it was necessary to upgrade all aspects of the engine.
(Gearbox too)  So the castings were improved as well as the bearing change. 

***CORRECTION: Ted Simons Triumph he rode around the world on was NOT a bushing model,, It was either a 72 or 73 Model which had many improvements over the early engines. So lets dispel that myth please ***

So, comparisons to cars always come up, and I have built a number of car engines and raced a few. But there is a BIG BIG difference and it comes down to design.   The more cylinders you have the smoother the power pulses, which is why for example Jaguar ran a V12,  A twin cylinder vertical twin without counterbalancers is a nasty enterprise, which is why Ducati and others ran a 270 deg crank. (Smooths out that nasty vibration)  Only Matchless/AJS really got the design right and then failed in execution with their  center main bearing. (Sloppy manuf tolerances).  This is why the modern Norton 952-961 engine has a center main bearing as that crankshaft whip is extreme.   I have the documentation on stress analysis equipment to prove this.

If you guys were to actually see how much these engines flex, whip and bend internally at speed you would never leave the driveway or garage.  Some feel that the vertical twin engines of BSA-Norton-Triumph are purposefully weak and flexible by design and some argue that by reinforcing them you invite breakage.  If there is any truth to that then you by extension have to acknowledge that  parts that flex can only do so for so long and how much. (IE: Time change)

But a bushing in a main bearing application CAN last a very long time in a 4-6-8-10-12 cyl configuration if properly supported.  Most of the small block chevy V8s I build are a high nickel cast iron block with 4 bolt main caps and substantial meat.  They get line bored and I use seasoned blocks.  They dont move or flex.

These old vertical twins dont have any of these benefits and the amount of flywheel flex and whip is extreme.   But dynamic balancing is critical.  Not the old static balance (Which is better than nothing) but true dynamic balancing is something I wont cut corners on.   I have found piston and pin weight discrepancies of several grams out of the box, rods mismatched,Cranks with different strokes between cyls, and then there is rocking couple. 

So a BSA A7-A10 puttering around under 4000rpm and intermittent usage will be fine on a bushing, but beyond that they need all  the help they can get.
Title: Re: Plain bearing vs roller conversion
Post by: Rex on 30.10. 2017 21:21
***CORRECTION: Ted Simons Triumph he rode around the world on was NOT a bushing model,, It was either a 72 or 73 Model which had many improvements over the early engines. So lets dispel that myth please ***
 

Turns out you are spot on, and it was a late police model with those nice big mains fitted.
Another old myth busted... *conf*
Title: Re: Plain bearing vs roller conversion
Post by: Sluggo on 30.10. 2017 21:29
Ted Simon was a guest many years ago at the Oregon vintage MC club annual banquet, seemed like a nice guy.
He gave a short talk and presentation.  I did not go that year but I heard it was good evening.

I rather like the later model Unit 500 Triumphs,  I would NOT want to travel the US interstate system for any length of time on one, but back roads they are a hoot. Torquey and just a lot of fun.  One of my long languishing projects is a Rickman Montessa missing  a motor.  I have a very nice 1972 Triumph Daytona motor for it and one of these days will see the road again as a enduro.  (I have a clear title and registration for the Rickman)  I wanted to run a BSA B50 motor in that chassis and BRG along the lines of a Jeff Smith bike but sadly the BSA engine is too tall for that frame.  The T100R is a tight squeeze but manageable.

To cut up the Rickman frame is unconscionable so Triumph it is.
Title: Re: Plain bearing vs roller conversion
Post by: Black Sheep on 03.11. 2017 14:40
That's where you and Odgie differ...
Title: Re: Plain bearing vs roller conversion
Post by: cyclobutch on 03.11. 2017 15:53
A similar argument often rages among unit Triumph enthusiasts, until someone always points out that Ted Simon (he of "Jupiter's Travels") rode around the World on a bush motor, and with no problems.
How much bigger test can there be?

I thought he had a lot of problems. Not sure how many were with the bottom end though.
Title: Re: Plain bearing vs roller conversion
Post by: Colsbeeza on 24.11. 2017 12:31
Lads,
I have attached an article of 20 years ago. Found it recently.
On topic up to a point. It restored my faith in the basic design of the Timing side bush.
Col
Title: Re: Plain bearing vs roller conversion
Post by: duTch on 24.11. 2017 19:32

 So now you have to come up with the follow up story... :!
Title: Re: Plain bearing vs roller conversion
Post by: harvey mushman on 24.11. 2017 20:19
Lads,
I have attached an article of 20 years ago. Found it recently.
On topic up to a point. It restored my faith in the basic design of the Timing side bush.
Col

couldn't agree more!

thanks for sharing article.
Title: Re: Plain bearing vs roller conversion
Post by: cyclobutch on 25.11. 2017 17:29
Lads,
I have attached an article of 20 years ago. Found it recently.
On topic up to a point. It restored my faith in the basic design of the Timing side bush.
Col

couldn't agree more!

thanks for sharing article.

I could only find this; there are a couple of pics if you scroll down, and it seems to be talking more of '85 than '86 I think.

http://zhumoristenouveau.eklablog.com/a-versailles-louis-xiv-recoit-le-paris-dakar-85-a117369820
Title: Re: Plain bearing vs roller conversion
Post by: harvey mushman on 25.11. 2017 18:27
Looks good in the husky frame, you could do a double take and almost think it belonged there! done up with its black paint job.

cheers  ;)

http://www.parisdakar.it/category/piloti/#/?playlistId=0&videoId=0

more pics
Title: Re: Plain bearing vs roller conversion
Post by: harvey mushman on 25.11. 2017 18:50
sorry a bit off topic  *conf*
Title: Re: Plain bearing vs roller conversion
Post by: Colsbeeza on 26.11. 2017 23:21
Hi Dutch, Harvey,
I did also wonder whether Mr Eicher competed in the 1986 Paris-Dakar.
Clearly the article was written just as the 1986 Rally was commencing.
I have been unable to find any reference to whether he competed in 1986, and suspect he didn't.
It appears from the article that he was planning to do so right up to the start of the 1986 event.
So I have just emailed him to ask. His website is at http://www.eicher-classic.ch/.
Awaiting his reply and will advise.
Colin
Title: Re: Plain bearing vs roller conversion
Post by: rocker21 on 29.11. 2017 10:22
many years ago back in the late 60's there was a firm that did a pure needle roller conversion that had a thrust washer made from phosphor bronze fitted to the timing side and all the bronze bushes were replaced by needle roller bearings, this was before devimead did it, i still have this engine in my loft, it was highly tuned with a polydine cam, 9:1 pistons, gardener carb and many other mods and it went like the clappers, no low down power and a very rough tick over, but it is still on that original needle roller timing side bearing, one major problem with fitting needle rollers to the idler shaft was oil getting in to the dynamo as there was no seal, nowdays you can get those bearings with a seal built in so that would cure the problem. building another engine on simalar lines but with a 357 cam instaed of the polydine as that would be dificult to ride in modern traffic.
Title: Re: Plain bearing vs roller conversion
Post by: Greybeard on 29.11. 2017 14:17
many years ago back in the late 60's there was a firm that did a pure needle roller conversion that had a thrust washer made from phosphor bronze fitted to the timing side and all the bronze bushes were replaced by needle roller bearings, this was before devimead did it, i still have this engine in my loft
They last forever if you keep em in your loft!  *smile*
Title: Re: Plain bearing vs roller conversion
Post by: rocker21 on 29.11. 2017 16:01
did a lot of miles on it, as it was my only set of wheels at the time so it went every where including a trip to the italian lakes 2 up , proved very reliable although a bit intractable at slow speeds , i think the filtrate 20/50 plus oil helped a lot. pity it is no longer available, then i changed to a castrol strait oil with a graphite aditive and that seemed to work ok, going to rebuild it and put it into a light frame to have a go at hill climbing, seems like a bit of fun that. got a couple of other projects i need to finish first.