A7 conrod on A10 shaft

[Peter in Aus]

I have just scored a A10 crankcase (ZA10 129**) and shaft that had been sitting in a shed for many years, on pulling it apart the conrons where for a A7 (6in BC) the shaft is A10 (84mm stroke)
Has any one come across this before?
I didn't get the barrel or pistons with it so am at a bit of a loss as to what is going on?
It was pretty obvious that it had been working like this, the shaft is in good condition the conrods where a bit of a problem, the PO that did them up had used lock-tight and when I tried to undo them the bolt turned in the conrod and stuffed it.
 Peter

[BSA_54A10]

There was a "hot rod" set up, which I thought was a factory competition modification, but I am not quite so sure now.
It involves lopping one fin off the barrels and fitting a shorter ( 6" rod ).
The landlorg got a stack of A 10 spitfire engines and there was a short barrel amongst the pile.
Dug up a couple of articles about the short rod engines.

[muskrat]

I think Rocker Racer has done that to one of his rig (sidecar) motors.
I went the other way and used A10 rods (shortened by 2.5mm) in my A7SS racer to run T160 pistons.
Cheers

[duTch]

 When i was keeping my original Road Rocket alive in the '70's, I was told speedway guys used A10 cranks in Triumph engines in TQ race cars, so maybe they used short rods too.
  I wasted a lot of time chasing up stuff in that realm.

   That's what i was *told*...

[Peter in Aus]

Thanks all for the replies, looks like it is not that uncommon.
 
Peter

[JulianS]

There was a US bulletin for fitting 6 inch A65 rods into a large journal A10, using A7 cylinder.

Also an article in "Motorcyclist" magazine in 1958.

[RichardL]

That is very intrresting, and one of the interesting points to notice is that they are serious about having the oil hole in the left con rod.

Richard L.

[muskrat]

G'dayJulian.
Thanks for that. The barrels would have been like the ones in another topic with thick flange and 1 less fin.
At those prices I'll have 10 please.
Cheers

[Peter in Aus]

Thanks Julian, very interesting

At those prices I'll have 10 please.

And put me down for 2!

[Klaus]

Hi Guys,
this conversion is my current projekt.
But using A65 crank and shortend A10 thickflange barrel.
The driveside shaft can be easy cut   for the cushdrive.
Stroke is 74mm in compare with the 72,6 for the A7. With a std bore of 70mm give around 600 ccm.

cheers Klaus