Author Topic: radial bearing clearance 2 3/4 hp CW 1924  (Read 277 times)

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Offline Müs

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radial bearing clearance 2 3/4 hp CW 1924
« on: 10 Dec 2019 at 17:59 »
radial bearing clearance
hello together I am looking for information about the radial clearance of the conrod bearing shells for my 2 3/4 hp CW 1924
I haven't found the right one in the forum yet, or I haven't asked the right question!
My machinist asks for it ...
it would be nice if someone could help me.
thank you Müs

Offline cardan

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Re: radial bearing clearance 2 3/4 hp CW 1924
« Reply #1 on: 10 Dec 2019 at 22:39 »
Hi Müs,

You are asking a slightly tricky question: I'm not sure there is a figure for the "official Douglas clearance" for the big ends, but perhaps someone here knows?

I assume the bearings are the usual split-bronze setup.

I ride my bikes pretty sedately, run in a fresh engine, and keep plenty of oil in the crankcase, and so I use rather small clearance on a bronze big end. I never measure it  - just ream it out until it is (just) free on the crank pin. I'd be surprised if the clearance was more than 0.001 or 0.002" (say 0.025 - 0.05mm). I have never seized a big end.

I have a friend who now uses 0.007" (0.18mm) on his veteran BSA to avoid seizing. A much bigger pin than the Douglas, but to me this seems like very large clearance.

If the CW is to be ridden hard maybe 0.003" or even 0.004" might be a good figure to aim for???

Good phosphor bronze for the bearing, and plenty of good (straight 50?) oil, should keep you out of trouble.

Any other opinions welcome.

Cheers

Leon

Offline Müs

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Re: radial bearing clearance 2 3/4 hp CW 1924
« Reply #2 on: 12 Dec 2019 at 16:42 »
Hi Kardan Thanks for the feedback I will pass this on to my mechanic and hope that he gets on with it info!

I have before your example zufolgen and it calmly to tackle with driving the Douglas, I am looking forward to ds the first time a round with her can drive. thank you very much

PS: I probably have a SW 24 but that shouldn't matter

Offline ian scott

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Re: radial bearing clearance 2 3/4 hp CW 1924
« Reply #3 on: 12 Dec 2019 at 23:07 »
I made mine at 0.001” it was too tight and I had some nasty squeaking initially. You need to have space enough for oil to get in there. Next time I will be giving it 0.002” to 0.003” clearance.