A10, A7 std gear ratios

[Truckedup]

  Just started  building the A10 project. The non unit  gearbox I have is said to be from an A7. It's stamped STD,  is this the same standard ratio  gearbox used in the A10?

[chaterlea25]

Hi,
Yes the same

John

[Rocket Racer]

depending on the state of them, worth considering fitting 520 sprockets & chain rather than 530. Allows for stronger chain imho. If sprockets still good stick with 530 until they're not.
The old pre unit boxes are pretty tough old things but well worth freshening up the layshaft and fitting new bushes to suit.
all the A & B preunit boxes interchangeable and the STD box went in most of them.   

[Truckedup]

 Are 520 sprockets available? I can modify  530 sprockets on my ancient lathe using a grinder attachment.  Any room for an O ring 520?  That would be nice...

[Rocket Racer]

Are 520 sprockets available? I can modify  530 sprockets on my ancient lathe using a grinder attachment.  Any room for an O ring 520?  That would be nice...

Yes the swing arm B31 ran 520 as standard so readily available for the gearbox and should be available for most rear hub types (I use an ariel (56/57 type rear hub with an adapter as I alter my gearing at the rear wheel for each track as have belt drive primary with 1:2 ratio) the narrower chain does allow for heavier chain. possibly not full o ring but certainly X ring. I run plain heavy duty 520 on my a10rr race sidecar. It gives you more chain options.
 

[Jules]

Hi Truckedup, would you mind posting a pic of "on my ancient lathe using a grinder attachment", I'd like a grinder attachment for my little Myford if its possible/easy... cheers

[groily]

http://www.myford-lathes.com/grinding4.html
Myford do purpose-built ones Jules. Possible, and easy, but seldom cheap!
There may be others that will go on if the height and mounting can be got right.
I don't have one myself - but am told it is important to take steps to keep debris off the bed and slides as far as possible, as it's very abrasive and there isn't much protection built in.

[RDfella]

At a pinch for very occasonal work I've clamped an angle grinder to the toolpost in order to attack something too hard to turn. Hardly the accuracy of a cylindrical grinder and, as groily says, keep the ways clear of the grit otherwise the lathe will be ruined in no time. Best to run the lathe in reverse too, so it's opposite rotation to the grindstone.

[Truckedup]

 No photos of the grinder...What I did was jam the hand held angle grinder gainst the tool holder then work it into the sprocket spinning on the chuck.
 Here's of photo of me cutting the splines from a hardened Harley primary sprocked on my 1951 Southbend Model B lathe...Disclaimer, I am not a machinist..I use improper and dull tooling just like BSA did...LOL

       

   The machined sprockets were then used on the dual engine Triumph land speed racer I built...Somewhat off topic but an example of my hillbilly engineering...

       
   

[RDfella]

QC toolpost I see. Been considering buying one for 30 yrs, but being a cheapskate I continue struggling with shims. Better things to spend £500 plus on.  As for 'hillbilly' engineering, perfection is for museums - quite often the fastest vehicle is bodged to some degree. Nice work.

[Truckedup]

 The tool rest on my lathe is a Shars, decent quality relatively inexpensive  Chinese made tools...Hillbilly engineering is working with what you have at hand and it does the job....We used to call a really buggered up repair a Rube after the  cartoon contraptions drawn  by  Rube Goldberg.

[Jules]

Hmm, nice job with Trumpies, did it work, how fast?
Thanks for the feedback RD and Groily, I'm no machinist, I just use Dads old tools as best I can, but I was thinking that if I could mount the Dremel somehow I could trim some gears/sprockets when needed - the Myford is pretty small for anything bigger than that and the accessory you showed Groiley is huge (and far too professional for me!!), cheers