Black Ariel timing side crank bush

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cmfalco
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Black Ariel timing side crank bush

Post by cmfalco »

I have my 1928 Model C's crankshaft back together and trued so soon I'll be ready to start putting the engine back together. However, I have a question about the timing side bush.

The bush that came in the engine when I bought it has a long slot at the top of it (0.046"x0.046"x1.9"), which is ~2/3" below the "official" drain hole back into the crankcase of 0.086"-dia. Although the area of the slot is only 29% of that of the hole, and the slot is quite a bit longer, which also would slow the flow, it still represents a drainage path into the crankcase so it could cause the level to be too low in the timing chest. Of course, if the flow of oil into the timing chest is faster than that out through the slotted bush, the timing chest would fill to the proper level in steady state when the engine is running. However, even if this were the case, the oil still would drain through the slot and bring it down to that lower level when the engine is stopped overnight.

Having no slot would eliminate the draining problem, but it would mean the oil would have to travel a long way through the ~0.002" clearance to lubricate the entire 1.9" length of the bush. How have others dealt with this?
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cmfalco
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Re: Black Ariel timing side crank bush

Post by cmfalco »

I've electroplated the drive-side bearing for a press fit in the case and will be installing it later today (by heating the case and freezing the bearing). At that point I'll be ready to machine and line-bore the bush, so if anyone has any insight into the question I posed in my previous post, by all means please make make it now (or forever hold your peace...). Thanks.
MGriffin
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Re: Black Ariel timing side crank bush

Post by MGriffin »

Hi there,
I see you answered a simple question i was searching for by way of the timing side shaft running clearance.
The 0.002” noted in your thread is about half of what i currently have. I was wondering though if 0.004 to 0.0045 was ok for the splash fed set up?
Anyway happy to make myself a new bush…..
so…on that, my original bush doesnt have the slot you speak of but it did seem intentionally ‘swaged’ over on the timing end to apparently limit the loss of oil into the timing case?
I read about this swaging on a forum discussing a prewar AJS single timing side bush.
Michael.
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Regards
Michael.

28 Model A
28 Model C
48 Red Hunter
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cmfalco
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Re: Black Ariel timing side crank bush

Post by cmfalco »

For what it's worth, a photograph showing the slot I broached is shown in the following post:

https://www.britbike.com/forums/ubbthre ... Post724183

Also for what it's worth, the bush with 0.002" clearance did not cause oiling problems during the 3000 miles, and it wasn't worn by the ordeal, so I would be very reluctant to use a different clearance if I ever were to rebuild another engine. If you haven't come across it in my thread, I highly recommend the seal I added in the outer timing chain case.
MGriffin
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Re: Black Ariel timing side crank bush

Post by MGriffin »

thanks for the reply. Its an interesting thread.
Regards
Michael.

28 Model A
28 Model C
48 Red Hunter
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