Drive side main bearings.

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Drive side main bearings.

Postby Pharisee » Wed Mar 15, 2017 11:00 am

I've been looking at what's needed to re-assemble the crankcase on my basket case '54 G3/LS. I'm definitely going to need drive side main bearings and their associated spacers as they are conspicuous by their absence.
The 1954 parts list says that I need two ball races, part number 017191 and two spacers (010628 & 017194). Looking on the AMOC Spares website, it seems that the ball race 017191 has been 'updated' to 026762, which is quoted an "Ball bearing : Drive side outer". There is a different bearing, 021872 which is quoted as "Ball bearing : Drive side inner.
Can anyone tell me what the difference is between the inner and outer bearings from AMOC Spares and should I be using one of each or as the parts list says, two of the bearings listed as 'outer'?
I apologise if that's a daft question but I've never put one of these bottom ends together before and I'd like to get it right the first time.
Many thanks
John

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Re: Drive side main bearings.

Postby Pharisee » Thu Mar 30, 2017 10:44 am

Ok... I've sorted out my query and the time is approaching when I assemble the bottom end.
The crankshaft has been fitted with a new drive side axle and a new crankpin assembly and I've got the two new drive side main bearing ball races.
I've only offered the ball races up to the axle by hand but I can tell that they're not a 'slide' fit and are going to need some persuasion to get them onto the axle.
The owners manual shows the two bearings and spacing washers being assembled to the crankcase first and the crankshaft going in afterwards. Is that the best (only?) way to do it. I was thinking more along the lines of heating the bearings in a pan of oil on a gas ring (outdoors, not on your beloved's cooker) and fitting them to the crankshaft first. That's the way I've done it in the past when restoring old stationary engines. When that's cooled down, heating the crankcase half and dropping that over the crankshaft / bearings.

How do those of you that have done this job before tackle it, please?

John

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Re: Drive side main bearings.

Postby Andy51 » Fri Mar 31, 2017 10:11 pm

Hi John, the reason the bearings are an interference fit in the crankcases and a push fit on the drive side mainshaft is to allow you to locate the crankshaft and control end float. The outer race is a tight interference fit in the crankcase, the inner is looser (the housing is double diameter, just detectable), to allow you to locate the bearings axially without end loading. Bearings MUST go in crankcse 1st; heating it up to about 200 deg C in the oven and they should drop in (not forgetting spacing washer!). The crankshaft can then be put in and located by the drive side nut and spacers. If the bearings are also an interference fit on the shaft, you will probably subject them to severe axial loading relative to each other, which the 2-diameter crankcase boring is meant to avoid. I don't know what bearings you are using, but a lot are Chinese cheapies with wider variance tolerances - I know, I have had that problem in the past with mains - as the crankcase cooled the bearings tightened up almost solid! I spoke to AMC Classic Spares (this is 10 years ago) and he had some European ones which fitted much better. If you can't get better fitting bearings, you could try easing the bearing area on the mainshaft with fine emery paper until you get the right fit - a possible long and tedious process and watch where any dust goes. Hope this helps, Andy

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Re: Drive side main bearings.

Postby Pharisee » Sat Apr 01, 2017 9:54 am

OK, Andy... thanks for the insight.
The drive side main bearings came from AMOC spares so I'm hoping that they're the correct ones. There's no maker's name on them, just RLS8 stamped onto the inner ring. The new drive side axle I got from Andrew Engineering as AMOC Spares didn't have one in stock. I measured the axle diameter with my 1" TESA micrometer and it is exactly 1.0000" to the nearest 1/10 of a thou. According to the specs at the back of the manual, the drive shaft should be 0.9997" to 1.0002" so that looks OK.
I've never put one of these bottom end together before and I'd rather not make a "pig's ear" of it the first time I do, so I'll follow the stated method and hope all goes well. I'm sure it will... probably.
Once the bearings are in the crankcase, I'll pop it back into the oven for a bit to expand the bearings a thou or so and hopefully the crankshaft will slide in. I don't like the idea of having to do any more than possibly giving it a light tap with a mallet.

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Re: Drive side main bearings.

Postby Pharisee » Wed Apr 12, 2017 8:32 am

Installed the drive side main bearings yesterday. I did is as per my original plan. The two ball races were heated up to around 200°C and at that temperature, they dropped straight over the new drive side axle (with the washer and spacer between them). While they were cooling down, the drive side crankcase half was in the oven warming up to around 200°C as well. That dropped easily over the crankshaft and bearings with no need for any persuasion. Assembled like that, I can't see why there would be any side load on the bearings.

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Re: Drive side main bearings.

Postby Expat » Wed Apr 12, 2017 11:35 am

Hi All,
Been following this with interest as I have the same bike but never stripped the bottom end out, not yet anyway. :)

Having read through it three or four times, I see Andy recommended fitting bearings to the crankcase first as a matter of importance it seems, though John's excellent description and pics have it the other way round.

Just curious, is this a personal preference method, or is there a deeper thinking/logic behind either method? :)

Thanks

Steve
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These are my principles, if you don’t like them, I have others. (Groucho Marx)

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Re: Drive side main bearings.

Postby Mick D » Wed Apr 12, 2017 2:41 pm

Hi

I would prefer to be sure that the outer bearing was fully located in the crank case and would fit with a press into the hot case - followed by the shim and inner bearing.

Regards Mick

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Re: Drive side main bearings.

Postby Pharisee » Wed Apr 12, 2017 6:24 pm

Mick D wrote:Hi

I would prefer to be sure that the outer bearing was fully located in the crank case and would fit with a press into the hot case - followed by the shim and inner bearing.

Regards Mick


The outer bearing was certainly fully located in the crankcase... that was what stopped the crankcase from going any further.

Installing the bearings onto the crankshaft axle first ensures that there was no side loading. The two bearings were located correctly with the spacer and washer between them with the inner bearing hard against the drive axle shoulder... nothing wrong there, ok?
The crankcase half was heated and dropped over the crankshaft / bearing assembly. The outer bearing register with the tighter fit, dropped over the outer bearing as far as it was possible to go with no need for any 'persuasion'. If that was ok, then the inner bearing with the slightly 'looser' register wasn't going to impart any side load.
When all was cool, the bearings were held tightly in the crankcase and the crankshaft was tight enough in the bearings that it wouldn't move with me pulling on it. I'm perfectly happy that the bearings are correctly located and that there is no axial load between the inner and outer rings of the bearings.

John

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Re: Drive side main bearings.

Postby Johnobirches » Wed Apr 12, 2017 8:14 pm

Hi John, please forgive the off topic question but the cases look superb - how did you get them so clean?
John

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Re: Drive side main bearings.

Postby Pharisee » Thu Apr 13, 2017 9:32 am

Johnobirches wrote:Hi John, please forgive the off topic question but the cases look superb - how did you get them so clean?
John


They were vapour blasted at T & L Engineering, in Elstow, Bedfordshire. I bought the bike (a G3/LS) as an abandoned 'project' and it had been dismantled and stored in a garage for the best part of three decades. They're were not a pretty sight but they have cleaned up quite well.

The on-going story is here, if you're interested.
http://www.whatfunnyhat.com/Frame_Stuff/Matchless.html

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