johnc
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Posts: 17
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Post by johnc on Feb 18, 2019 20:11:30 GMT
I wondered if anyone could kindly send or post some pictures of the Steel chaincases as use in 30's
I am slowly building up a early 30's with 250 rudge engine. I have never had a chaincase.
I am collecting woks and spun domes, and will enjoy fabricating one. It would be nice to have a selection of pictures to copy.
The pics attached is from the 1936 500cc Cotton Blackburne at Nat Motorcycle Museum. The RH one is a 250 cotton jap with chain mag drive that I will need.
I was going to guess the inner part and fixings. Any pictures of any of the parts could be very useful to me.
Many thanks John
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Post by cottonjo on Feb 19, 2019 8:44:22 GMT
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johnc
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Posts: 17
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Post by johnc on Feb 19, 2019 8:57:52 GMT
Many thanks for that. I had not seen that chain guard detail before. Looks like JAP doesnt have much of a engine shock absorber since there is not much of a dome there. I'm getting there. Thanks again
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Post by cottonjo on Feb 19, 2019 8:58:40 GMT
 A 1932 JAP Chaincase No engine shock absorber |
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Post by andreas on Feb 19, 2019 18:41:53 GMT
Works 250 Python  and 250 Jap  and my 250 Python  |
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Post by cottonjo on Feb 22, 2019 14:32:26 GMT
The 250 JAP looks remarkably similar to my 350 JAP. Your Python is looking good. I have many pictures of home made chain cases, many only partially cover the chain. An inspection/lubrication hole is probably worth having, I have noticed on more than one occasion that the primary chain somehow tightens for no apparent reason.
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Post by andreas on Feb 22, 2019 16:19:29 GMT
Primary Chain tightening is very common with these types of bikes, more torque makes it worser, it is a common Problem on Rudges. My solution for the Rudge gearbox are high tensile bolts, and I always run the chain a bit loose, to have some security if the gearbox moves.
The reason for the tightening is in the ratios of Primary and Secondary chains, i have a calculation somewhere
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johnc
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Posts: 17
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Post by johnc on Feb 22, 2019 17:23:25 GMT
yes, in first gear, the net 'pull' backwards is far more (lots of tension in rear chain). Mounting the gearbox top and bottom would be a lot better.
I guess, letting the clutch out too sharply from standstill it when max force/stress occurs.
Anyhow, back to chain cases, I am still interested in how Cotton did the detail of the more enclosed type. An easy method of checking the tension seeem a good idea.
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Post by andreas on Feb 22, 2019 19:42:08 GMT
  ere a Blackburne and a high cam Jap |
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alanf
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Post by alanf on Apr 4, 2019 17:59:29 GMT
Hello, I made a primary (and secondary) chaincase for my 250 Cotton Python, using an old primary chaincase I had (no idea what it's from). I checked it was ok by photographing the primary chain in psoition, then putting the chaincase on with sellotape and photographing again, then superimposing the two photos. to see there's plenty of room around the chain etc. I then fixed the dynamo/contact breaker in place, and cut away the chaincase to clear it. I then worked out what cover extension was needed to enclose the dynamo chain, and found a suitable tool box lid lying about, which was about right. A quick cut and weld - lots of filling, making an inspection hole to check chain tension, and some primer. That's as far as I've got, but the photos. will hopefully show how I did it. Good Luck!! Just found I can only attach 3 photos, so the other 3 will be a separate post!! AlanF |
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alanf
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Post by alanf on Apr 4, 2019 18:01:02 GMT
These are the other 3 photos. re my chaincase AlanF |
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johnc
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Posts: 17
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Post by johnc on Apr 4, 2019 19:06:01 GMT
That is fabulous Alan. good work! You were lucky to find a near-perfect case. You sure it wasnt off a Cotton!?. I have bee scouring charity shops for woks and bowls, and have a fair variety now. In fact, a butane camping gaz refill seems quite good for the front. It will be a while until i get around to this, so I should have plenty to choose from.
Thanks for the pics... very interseting
On another note, do you have advance/retard on that dynamo? mine doesnt, but I was wondering about doing a mod. I do like a manual advance lever.
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alanf
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Post by alanf on Apr 4, 2019 19:26:48 GMT
Hi John,
Pretty sure it wasn't off a Cotton, the fixing brackets were completely wrong, and had to be cut and re-welded. I've owned many marques over the years, it's probably from some other project that didn't get finished!
Yes, you're going to need advance retard - I had the bright idea of using a BTH auto-advance off of a Velo that I had with a wrecked fibre gear. But then just as I started working out how to replace the gear with a suitable sprocket, I realised that it would be running at engine speed, not half speed as on the Velo, so would advance too early, and only 1/2 the amount needed.
Miller dynamos with A/R are like rocking horse droppings - however, I might have a spare A/R part - I'll have a look tomorrow - but don't hold your breath.
AlanF
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johnc
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Posts: 17
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Post by johnc on Apr 4, 2019 19:43:58 GMT
My MAC velo had a dodgy looking fibre gear, and I fitted a steel gear and graften a manual mechanism to the mag with the help of Areldite. Looking at the miller dynamo, grafting doesnt look so easy.
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Post by Bob Smith on Apr 27, 2019 9:31:35 GMT
Here are a few pictures from my 1934 Jap engine - hope they might help! (Two more in the following post.) |
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