A65 gearbox thrust washers

[Mike Farmer]

 

"The Book" gives three different thrust washers for Gearbox. 42-3079. 42-4312* and 42-4313*  Of these * there is only +005" difference

How do I measure which one is correct thickness.

Mike

[Bess]

Hi Mike,
            You need to build the gearbox and use the thrust washer that gives negligible end float.

Best wishes...

[Mike Farmer]

 

Hi Bess

Thanks for that. I have a gearbox that has been stripped and reassembled with no thrust washers at all. As I've never "done" a gearbpx before this is a game of blind mans buff.

But its all good experience. He says blithely tongue in cheek.

Mike

[Mike Farmer]

 

As stated I'm out of my comfort zone here. How do you suggest I check the end float.

I think I must strip the box and remove all the clusters from the main shaft then put in the spacers on the Lay?shaft and offer it up. With this all in place how do I tell what end float I have.

Mike

[Bess]

Hi Mike,

              There's about an inch of the shaft protruding, push it back and forth and rotate it. You can gauge too much float easily, if there's little or no float check it rotates, if so its okay.

You can be technical and set up a DTI looking for 1 thou.

Best wishes...

[Mike Farmer]

 

Hi Bess.

I guess this has to be with the gear cluster in place and bolted up. Also guess will be ok with just the lay shaft set up to make movement simpler and easier to Feel.

It could be a bit expensive, those spacers are about £10 per. We'll see. I'll talk to Drags and see if they'll let me return unused ones
Thanks agen

Mike

[Spaceman]

The BSA workshop manual simply says that there should just be perceptible end float in the L/S - I assume this equates to a few thou of end float. I was forced to measure the end float in all the shafts in one of the more modern engines I have rebuilt but it is not easy to do to the required accuracy (~ 1 thou). It can be done with a digital vernier calliper with a special foot attached allowing it to sit exactly perpendicular to a flat surface and it needs a precisely machined bar to be placed across each engine cover to allow the depth to each bearing source to be measured. In the case of the A65, if you can grab hold of the end of the shaft to test the end float, that should be perfectly adequate.

[DAVE BRADY]

Hi,

I have found that it is bit of a compromise as there are only a few thicknesses of shim available.  It is quite easy to feel the end float as the shaft can be pushed and pulled and it is possible to feel a few thou.  I would think that an amount that can just be felt will be right.  If accurately measured then there are shims available usually from bearing suppliers but all this effort could be in vein as the rest of the gear box is likely to be a bit sloppy.
There are several other shims in the gear box but I do not think they are mentioned in service sheets and unless the box is run dry are unlikely to wear and need replacing.

Dave.

[Bess]

Hi Mike,
            Draganfly is a good option, I wouldn't bother asking them, their return policy is no quibble 6 months.

If you build the gearbox with what you have it might be okay anyway. If not, I have some and happy to let you use mine to gauge the sizes, PM me if I can help further.

Best wishes...

[Mike Farmer]

 

Hi Bess, 

Thats a very kind offer and I shall come to you if necessary.

The situation is that someone has rebuilt the cluster with no spacers whatsoever. Which makes it easier in some ways cos its really a case of buying the basic ones then going from there. As Dave said It is probably worn in places that would make it very difficult to be totally accurate.

Now an aditional  point that someone may throw some light on. Pt No 68-3073 Sprocket 20 tooth. Yet I have a 21 Tooth sprocket with that no on it and looking very BSA forgeing.??  It actually says  BSA 68-3073-4001

Mike