Author Topic: Drawing > rigid frame + 4-speed light weight gearbox  (Read 823 times)

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Offline Paule

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Drawing > rigid frame + 4-speed light weight gearbox
« on: November 15, 2015, 08:41:00 PM »
Hi,
BelowCAD drawing of rigid frame with 4-speed light weight gearbox.
Front frame is 4-speed version, with longer rear down tube, angle to top tube 83°, lug for battery carrier.
Engine plates are part no. 29-4183, modified holes for fitting rear down tube.
The dotted lines show 3-speed front frame and cut away area of engine plates.

If the dimensions are correct, that i took directly from the different gearboxes, the chain alignment should be totally in line with engine and rear sprocket. The travel of gearbox sprocket, compared between 3-speed and C12 4-speed, will be about 1 mm in height, and 2 mm in length. I'm sure this won't give any problems with primary/rear chain adjustment.

Now waiting for final parts to arrive and get on with the job :)
Paul

Offline Paule

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #1 on: December 24, 2015, 12:44:46 PM »
Received NOS 4-speed frame by now, put it together with unmodified 3-speed gearbox plates, a spare crank case and rear frame. Frame down tube to gearbox plates perfectly matches the spot on the gearbox plates, which i had taken from the drawing.  8)

Merry christmas to you all and a happy and an enjoyable new year.
Paul

Offline chaterlea25

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #2 on: December 24, 2015, 01:53:04 PM »
Hi Paule,
Best Wishes for Christmas and 2016  ;D

The BSA is looking great,  8) 8)
WIll the rigid frame tank fit  the later front? ( I seem to remember it fitted the C11G frame I used?? but that was 40 odd years ago  :o)

Cheers
John

Offline Paule

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #3 on: December 24, 2015, 04:27:35 PM »
Hi John,
i hope so  :o
As the dimensions of top tube are the same, i'm very confident!!
Cheers, Paul

Online Owen

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #4 on: December 24, 2015, 04:36:56 PM »
Drawings say's spring frame, yet it's a ridged.
1945 C10 & C11
1953 C10 & C11
Still looking for an Original 350 side valve C12

Online MilitaryRon

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #5 on: December 24, 2015, 04:45:12 PM »
Keep up Owen! It says spring front frame with rigid rear frame!  Ron

Online Owen

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #6 on: December 24, 2015, 05:33:20 PM »
Doh
Did not read the pic just the file name?
1945 C10 & C11
1953 C10 & C11
Still looking for an Original 350 side valve C12

Offline Paule

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #7 on: January 03, 2016, 08:54:18 PM »
Hi to all, here's some new pics. Have to adapt RH gearbox plate a little more, gearbox not moving to most forward position (by 5 mm). Last pic shows the spot where the gearbox is being obstructed.    Paul

Offline Paule

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #8 on: February 23, 2016, 05:17:56 PM »
Hi to all,
update on my C11 project, finally have started reassembling the bike. Below you'll find the final drawing, with both gearbox plates showing their individual modifications.
 
The 3 pics show:
- LH side view
- Alignment of engine and clutch sprocket, all the alignments look really good! It's going to work  :D
- Rear brake lever is being obstructed by gearbox in most rear position  :o

Hope this will help other lads doing the same sort of things!
Cheers Paul

PS: WANTED: Used C12 sprockets, to modify them from 19T to 17T. In exchange i'm happy to send some excellent Swiss chocolates to you!!
« Last Edit: February 23, 2016, 05:22:47 PM by Paule »

Online camman3

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #9 on: February 24, 2016, 07:30:41 PM »
Hi Paule, I spilt the topic to keep this one alive.....as we wandered off about chocolate and penknives ::)
I'm afraid I dont have any sprockets to offer you
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Offline Paule

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #10 on: February 24, 2016, 07:40:39 PM »
Thanks Graham! 

Offline enfield49

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #11 on: February 25, 2016, 07:59:29 AM »
If the lightweight gearbox was used in a rigid frame would the saddle tube stop primary chain adjustment ? Graham

Offline Paule

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #12 on: February 25, 2016, 05:52:31 PM »
That was the first i did, just out of curiosity. Only managed to put the rear gearbox bolt in, gearbox touching three speed plates. Zero travel for primary chain adjustment. On the photo, in front, there's a 4-speed heavy gearbox plate for comparison, the ones in the rear are genuine 3-speed ones. The rigid frame saddle tube will block chain adjustment as well.    Cheers, Paul

Offline enfield49

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #13 on: February 25, 2016, 10:38:21 PM »
Do you think it wold be possible to rotate the gearbox to get clearance ? Graham

Offline Paule

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Re: Drawing > rigid frame + 4-speed light weight gearbox
« Reply #14 on: February 26, 2016, 10:44:51 AM »
Don't think that rotating the gearbox would give much more way for primary chain adjustment. And rear brake lever will become even more obstructed by rear end of gearbox (last photo of post Febr. 23rd). If gearbox is rotated, it should be rotated around clutch centre, otherwise primary case needs modification.  Paul