ET: Engine (Twin) Main bearing race splitting?

[greg brillus]

I always felt the factory stake marks were simply done to stop the outer races falling out once they flipped the case over to install spindles and so on........heavy marks done by folk are a butchers method of securing the bearing races if they have come loose.......You can tell when they've done a top job.......when you spin the inner race to enter the outer, it acts like a ratchet.......the heavy punch marks have distorted the bearing in all the big hit spots........just lovely.......Vic your work and choices of bearings are obviously, or most likely better than standard, but most Vincent owners are not skilled machinists......that kind of work is beyond most of us........if the bearing housings are reclaimed, new bearings installed, and the crank set up nice and true.........this will see out most all owners till the next one takes over........Your work efforts are similar but different to the work we have done on our race engines.......So far with impressive results........All good fun.

 

[Pushrod Twin]

Is the respected Professor's mains bearing sleeve repair out of favour? I carried this out on my chopped die cast cases successfully. Yes, it was a bit fiddly, but I feel it's a good solution to maintain strength in the cases and durability to reduce bearing fretting.

https://www.vincentownersclub.co.uk/resources/reclamation-of-damaged-crankcase-main-bearing-housings.209/

 

[oexing]

The argument about these horrible staking procedures as a means to prevent the outer race from falling out when installing timing spindles would be quite silly for a company in production business. Good logic would first shrink in components with highest temperature requirements like the timing side spindles at min. 180 degrees and only then shrink in mains outer races at around 100-120 degrees. So no, staking was a last step for somewhat securing the races from walking into the crank pin nut. Noway can you rely on shrink fits in serious engineering for components to stay put. You´d have to think about other ways to have them solidly positioned.
My guess is they had the "brilliant" idea of slimming down the outer races for no chamfer to move them as close as possible to the very wide twin crankshaft. So only choice was the roller bearing type with plain outer race as only with these you can put the races on a table grinder for the job. But then they were out of ideas how to stop them from walking, no lips on these. That is when the staking was entered - with troubles coming up onto later generations.
So I think you guys have to come over the religion of absolutely wanting plain outer races and rollers kept on the inner race. At the same time get over the imperial sizes of mains when repairing clapped out bearing seats, look at metric types with all sorts of lipped versions as you want them. You´ll be safe with them ever after and they are a LOT stronger than the originals. I think the Horner bros got 30 mm mainshafts today, was my choice certainly 30 years ago, by the way.
Sure, you cannot feed the oil pump scroll through the metric lipped roller bearing NJ 206 when it is dropped into the case already. So you either thread the mainshaft carefully through the already dropped in scroll plus key when lowering the crank into the case - or putting the case onto the crank below it. This is no miracle to do, easy compared to the string trick with rollers unwilling to enter the plain outer race without chamfer.
Alternatively, think about any other crank with mains ballbearings on, you just put on all components on mainshafts that have to be on place at that stage. Then get your electric heat gun and have the case up to min. 100 degrees and sink the crank down to stops - simple and very common elsewhere.
This works on the timing side and drive side as well. I got no ball bearings on the drive side, instead lipped rollers with oil seal between bearings. The outer roller bearing got a plain inner race so it slips through both roller bearings on assembly . So then the positioning of crank is done at two places:
Both inner roller races of d.s and t.s. are lipped certainly and set to near zero side play in cold case. That will expand a lot in operating condition.
So second place for sideplay setting is between lips at drive side, no ball bearing there, one direction already set by inner d.s. roller bearing type NJ 2206, with lips, plus the other direction is set by a special steel bush that carries the triplex sprocket. I did a fat hardened lip/top hat bush for providing the outer roller bearing lip and this sets side play better at hot engine. The NUP 2206 got a separate "lip" to go with its inner race shortened by the thickness of that extra lip. So then you can do the hardened top hat bush for the sprocket and ample faces to bear the ESA side loads. It seems I turned that single lip on the inner race of the NUP down for slipping the lot through all bearings of d.s. .
Next use of that top hat bush is a solid face taking the substantial side loads from the ESA springs: Standard was the sprocket loads the inner race side face of the ball bearing. But sadly there are two radii on that inner race and the minimal remaining face wears into the sprocket plus the inner race, throwing chain alignment out in time.
Did I say the 30-62-20/-16 mm NU or NJ 206 roller bearings are a LOT stronger than the old originals ? But after many decades with these old engines another factor is more important: Aluminium got a "memory" about earlier high load operatioins, meaning with a lot of hours of high stress it goes weak and soft and in places may do cracks and not reversible any more. Ask any mechanic about common aero engines, turbo types mainly, they hardly go more than 800-1000 hours before cracking cylinder heads in that dreaded large thread that holds the head on the steel cylinder, no studs on these. Or talk to dragster guys, some run alu conrods - but change them each year or even earlier, else they destroy the engine.
So that is why I will NEVER remove material around the mains bearing seats in old engines , places of high loads I´d think. And no screws in any adapters certainly, Greg will know very well. Does not matter when you have steel adapters for resizing correct fits in worn cases, this will not make the case stronger at all as you take out a few millimeters again - a no, no.
So another bonus with the smaller but even stronger metric roller bearings, you ADD alu adapters for them, from 63.5mm down to 62mm. When the old bearing seat is not too mangled you just turn an alu adapter 2 thou oversize, loctite all faces and press that in quickly. Line boring for correct shrink fit is exactly same job as with restoring the imperial sizes, same amount of efforts in either option.
There is the only extra part you got to do, the sleeve on the mainshafts from 1" up to 30 mm - no big deal I say and you can even care for some loose bearing fit on the old mainshaft, just get some Loctite 638 for the sleeve with push fit.
Between both roller bearings on d.s. I put a hard spacer for the shaft seal to act on for separating oils of engine and primary and have reliable venting of crankcase.
So what´s not to like about that metric mod, no weakening of bearing seats as no oversize boring for a sleeve is to be had. All sorts of lipped roller bearings avaliable from SKF or FAG top quality. I see no extra high demands on the skills of the mechanic with the metric mod but lots of snags with the standard stake-prone plain outer races. Same goes for Prof Neville´s steel threaded fiddly adapter, requires oversize boring the case - not my idea in old engines.

Vic

top hat bush on d.s. mainshaft against the outer bearing forming the outer "lip" and sprocket bush :

 

[greg brillus]

Also worth noting, is often, the bearing bores are not round, once the bearing shifts and rotates, it starts to wear the housing out of round.......same happens to loose spindles.......the bores don't stay round.......conrods that have had a hard life.......the bores go out of round.......cases get more heat in them than you might think.......here in Aussie, hot climate, after a good run on a summers day I've seen the cases at 140 degrees after they heat soak for 10 mins or so. The big factor here to is the crank has 4 main bearings, so alignment of the crank assembly is much more critical than most other engines with only one bearing on either side......The original flywheels are not a high grade of steel, so a big over rev or something similar and the wheels shift ........this can then put both main shafts out of alignment........I wish I had your machining skills Vic.......Good stuff you've done there.....Cheers.

 

[oexing]

Luckily they specified four main bearings for the Vincent, with that wide twin crank I would not think it stayed aligned at all for long. Only two bearings for a crankshaft is seen as substandard here, maybe acceptable on prewar bikes. My bible is Apfelbeck, the engine man at BMW, Horex and other companies. He designed a 4 valve Rudge based single with opposing valves, means two carbs two ex pipes,diagonally placed, tremendous power from this - but the Rudge block exploded at 50 hp or so. So myself not much use of Irving´s Tuning for speed here. Anyway, Ludwig Apfelbeck´s religion was minimum 3 main bearings on a single for preventing twisted bits . But then, the Yam SR 500 or Honda radial 4 Clubman only got two bearings, big certainly and a heavy parallel press fit pin, 36mm the SR crank. They hold up quite well even so. As to tired engine cases, I am told SR 500 cases for high power racers are seen cracking at the cylinder base, no through studs but a few base studs and either the cylinder cracks at lower part or the case cracks at the weakest place. That will happen more often with aging engines in coming years, tired alu again. So that is my angst about having sleeved main bearings for standard sizes, not a problem instead sleeving down to 62mm metrics.

Vic

Apfelbeck with his diametral 4 V head:

Apfelbeck inspired radial 4 V , two carbs above head:

 

[milohiscox]

Vic - thanks for all your advice, I will certainly investigate the metric lipped options. I also admire your pressed in crank pin.

Old Harley Davidson's of the same era had a nice solution to prevent this problem. They cast a substantial steel insert into the aluminium case. Being cast in, not pressed in, it could have all sorts of retaining features, and I've never heard of one loose in the aluminium. The steel bearing race then pressed into the steel housing insert. Being steel the housings are less prone to enlarging, ovalising, cracking etc. If they do get damaged, then oversize races are available.

Picture here taken from a 1950 Harley WR 750cc factory race motor. These race motors had the cast in inserts bored out to take ball bearings, one on each side. Racers would often use spherical self-aligning ball bearings, particularly on the timing side, to allow for any flex or mis-alignment in the crank. I guess it was easier to change a bearing every race than to bother truing your beat up crank.

 

[greg brillus]

Yes once you start pushing 50 plus HP from these engines, you start to see weaknesses in them that otherwise you would not see........Big issue is heat.......not many engines share the same finning area of a Manx........most all Brit type singles will show signs of overheating.......another one is piston design........Most of the so called "Good" designs that we've seen from CP and the like (which are mostly blanks from some other simple design) will destroy themselves.....they all share common features that are not good on a high HP engine. These are single cylinder engines I'm talking about not twins.......I would think that once you push a twin over 100 HP you will see similar failings. Also seen quite a few classic race engines that have cracked the top of the crankcase away........Gold Star's, triumph twins and so on.

 

[bmetcalf]

I remember a magazine story about a fuel drag Sportster breaking one flanged cast iron barrel off as it crossed the finish line. Apparently when the rider looked down, the cylinder and head was dangling by the throttle cable!

 

[oexing]

Milo reminded me about a detail I did not include above: There must be a number of engine cases with wrecked outer circlip grooves, I got at least one of these, see photo below. Now when you got the standard plain outer roller race you are stuck with the ball bearing locating the crank in the case. That gets awkward now with a wrecked circlip groove. As told, I would NEVER want to drill or take out material around mains bearing area for angst of getting cracks some time later.
So another bonus when accepting lipped metric roller bearings: Look at photos below, I had the circlip in its original groove for pressing in two loctited alu adapters 63.5 to 62mm i.d. at either side of the circlip , no boring done at that stage then but some allowance in i.d. for finally line boring all sizes with correct shrink fit in the end. For line boring in one go the circlip had to get out, which was a bit of struggle as Loctite filled all space between the two adapter bushes. So when copying that job better wax the circlip for easier removal and not having some Loctite on it.
So you just got one circlip left in its old position still, not as proud of the i.d. of bearing seat but allright , there is not much sideload on the crank anyway. Next is the question about any oil seal between both drive side bearings, ball or roller, scroll or shaft seal. Now say, then inner lipped roller bearing sits on the circlip, so you work out where the outer bearing has to go, like flush with the old wrecked circlip groove close to it. This will give you the length of a spacer up to the inner circlip, minus width of outer bearing. Exactly same size you want for a spacer for inner races, so all races , inner and outer stay in line by having their spacers. I opted for a shaft seal sitting in the large alu spacer and acting on a hardened spacer about same diameter like the inner race of the roller bearings. So when you got that worked out you finally have some hardened spacer remaining at mainshaft end with a large lip, that doubles as load bearing face for the triplex sprocket, much better than the ball bearing inner race that wears a lot.
The total play within the two drive side bearings will be set by the width of the spacer between them , I´d go for zero - 10 thou max., not critical. It will get more by heat growth anyway. So then no need for some action of fabricating a substitute of outer circlip groove - and no drillings around there.
Basically you could keep a ball bearing there for outer bearing if you like. That would be same sizes, type 6206, 16mm wide, or 62206 20 wide. I prefer roller types, twice the load factor with them and a joy to assemble. All gearbox bearings are roller type, except the ball bearing on input shaft at clutch end.
So all in all I see a few bonuses - ah, boni - with lipped bearings, not so much with the traditional stake-and-run plain races bearings .
In one photo you will find the camplate hanging on a shouldered bolt, did not want it sitting on selector forks . . .

Vic