BSA C10 C11 C12

BSA C10 C11 C12 Forum => Technical Section => Topic started by: chaterlea25 on January 08, 2019, 08:39:58 pm

Title: Footrest bar /engine plate hexagonal hole repair and modification
Post by: chaterlea25 on January 08, 2019, 08:39:58 pm
Hi All,
Wear on the engine / gearbox plates where the hexagonal bar goes through them is a PITA on C models
Its a poor design that goes back to the 20's model L (350) relying on just the support of the engine plate thickness to keep the footrests from flopping about  ::)
I am working on my model L and the plates holes were well shot, on this BSA the plates are only 3/16 thick originally
The ends  were also well corroded, so I chopped back to good metal and welded on new sections
I bought two 7/16in. AF single hex deep sockets, I drilled them through 13mm from the square drive end up to the hexagonal section to allow the hexagon bar slide through, this left approx 3/4in of hexagon section left
The sockets were then shortened to half the width of the fitted engine plates so they replace the spacer that previously sat between the plates
I sanded the chrome off the sockets and drilled the plates out to a snug fit for the sockets
I then brazed the sockets to the plates with a piece of hex bar slid through the assembly to keep them inline
Braze rather than weld did not shrink the hexagons

Pictures are better than words  ;D

John


Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: Owen on January 08, 2019, 08:47:17 pm
Looking good.
That's probably why they changed the footrest bar to the straight through version on the later C's
Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: Biggles on January 08, 2019, 10:14:05 pm
Very nice work
Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: Dstep on January 11, 2019, 01:25:09 am
Smarter than a tree full of owls. ;D

David
Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: chaterlea25 on January 11, 2019, 08:46:58 pm
Hi David,
Quote
Smarter than a tree full of owls.

I am all  :-[ :-[ :-[ :-[

John
Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: stev60 on January 11, 2019, 10:37:42 pm
well one thing is that brazing the keeps it original,  I wonder why BSA used brazing instead of arc welding it would have been slower, obviously strong enough , the frames have survived the test of time
Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: camman3 on January 11, 2019, 11:10:35 pm
Arc welding would cause more distortion as well as introducing stesses more likely to crack.
On most of the major frame joints, the tubes are "socketed" together, and the brazing can flow into the socket producing a strong joint.at a lower temperature, a bit like soldering copper plumbing.....thats the way I see it, anyway.
Graham
Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: chaterlea25 on January 12, 2019, 12:03:53 am
Hi All,
BSA gas welded the A and B swing arm frames for the first few years 53-56?
Then they fitted engine lugs that were brazed to the down tubes , to replace welded on tubular mountings
Arc welding then started to be used for various parts on the frame construction with gas welding on other parts ???

A friend of mine has a 1929 "Favor" (French made) where the frame, forks (90+%) and fittings are gas welded, even the carrier is integral to the frame
It looks strange to eyes used to looking a British built bikes of the era  :o
Look at the way the frame front down tubes are joined together !!!!

John
Title: Re: Footrest bar /engine plate hexagonal hole repair and modification
Post by: timsdad on January 12, 2019, 08:35:16 am
Brazing and gas welding is very time-consuming so, when electric arc welding came in, it was a great way to speed up production. Distortion from the 'instant' heat is always a problem with distortion as it all cools down so they had to be selective in what they gas-welded and brazed and what they arc welded.

Hinckley Triumphs are all arc welded by robots and they had problems with their first alloy frames distorting when they came out of the jigs twenty years ago. They solved the problem by assembling all the separate alloy parts  out of true in the jigs so, when cold, the frames, swinging arms, etc all settle down in the correct geometry.


Ray