Racing crank for 1925 cases

[Ed Byrne]

Hello all,

I'm the current custodian of  one of the Bert Thorpe alloy motors.

A friend of mine who is an extremely competent Engineer has split the crank and has expressed his concern that it might be beyond use. It has been skimmed to accept oversize rollers previously in its life. The conrods are home made alloy rods 

It's engine is 68mm stroke and 68mm bore and from its engine number I've been told it's a 1925 TT jobbie.

I'm hoping to fit a new crank and a pair of new rods in this engine, is anyone making new cranks and rods?

Cheers,

Ed

[RA23]

Ed,
My good mate and mentor Jack Rudd   (Australia) unfortunatley no longer with us hill climbed pre war vintage rallyed 70"s historic racing in the 80"s then after a nasty accident of which he said it takes too long to heal he built a 500 speedway outfit and raced into his early eighties in vintage speedway until suffering a stroke which ended his Douggie Doings. Butafter exhausting his crankshaft supply he used BMW 68 mm stroke cranks which were " bullet proof " so no more issues after that. You mention you have a good engineer friend so there is your answer. I too am a machinest and have a BM crank in reserve.
Jack was our Aussie equivalent of Henry Body who I corresponded with and spent a full day with in July 2009  Another lovely very helpful man who suffered the  contagious" Dougs Disease "  We who are a little younger are fortunate to have learnt from them.
If you have not already done so read Doug Kepharts crank rebuilding article on the Forum. Doug in earlier times made long  rods for the long stroke DT"s. Another clever friend who eats drinks and breathes our beloved Douggies.
Bob Barlow>
 
 

[Ed Byrne]

Ed,
My good mate and mentor Jack Rudd  (Australia) unfortunatley no longer with us hill climbed pre war vintage rallyed 70"s historic racing in the 80"s then after a nasty accident of which he said it takes too long to heal he built a 500 speedway outfit and raced into his early eighties in vintage speedway until suffering a stroke which ended his Douggie Doings. Butafter exhausting his crankshaft supply he used BMW 68 mm stroke cranks which were " bullet proof " so no more issues after that. You mention you have a good engineer friend so there is your answer. I too am a machinest and have a BM crank in reserve.
Jack was our Aussie equivalent of Henry Body who I corresponded with and spent a full day with in July 2009  Another lovely very helpful man who suffered the  contagious" Dougs Disease "  We who are a little younger are fortunate to have learnt from them.
If you have not already done so read Doug Kepharts crank rebuilding article on the Forum. Doug in earlier times made long  rods for the long stroke DT"s. Another clever friend who eats drinks and breathes our beloved Douggies.
Bob Barlow>
 
 

Hello Bob,

Many thanks for the reply. I think a BMW crank would be a good idea. 

Do you know which BMW crank I should be looking for? 

All the best, 

Ed

[Doug]

The post RA23 refers to can be found here: Illustrated tour of the pre-war Douglas o.h.v. crankshaft

-Doug

[RA23]

Ed,
Post war 50's 60's
R50  68 stroke
R60 73 stroke
68mm 600 barrels with R50 is a good match
Somewhere amongst my paperwork i have configurations of the two cranks with piston sizes and capacitys.
The R69S also is 73 mm. 
I hope this helps. 
Bob Barlow.

[Ed Byrne]

The post RA23 refers to can be found here: Illustrated tour of the pre-war Douglas o.h.v. crankshaft

-Doug

Thank you Doug!

[Ed Byrne]

Ed,
Post war 50's 60's
R50  68 stroke
R60 73 stroke
68mm 600 barrels with R50 is a good match
Somewhere amongst my paperwork i have configurations of the two cranks with piston sizes and capacitys.
The R69S also is 73 mm.
I hope this helps.
Bob Barlow.

Thanks very much!

[Ed Byrne]

The post RA23 refers to can be found here: Illustrated tour of the pre-war Douglas o.h.v. crankshaft

-Doug

Thank you!