Gearbox shaft end floats, S/A A10

[KeithJ]

I an just overhauling my gearbox and checking the end float of the shafts.  When I tighten the nut at the kickstart ratchet end, what end float should I get on the mainshaft?  Probably have a few thou.
Also, what should be the end float on the layshaft, I have been told about 0.030" which is what mine is.
Thanks
Keith

[chaterlea25]

Hi Keith,
All bolted up there should be zero endfloat on the mainshaft
it is dictated by the right hand ball bearing which should have no sideplay

I would consider 0.030 to be a maximum amont of endplay, it probably makesa little difference in practice
as the shaft is pulled to one side by the drag on the speedo worm gear

Usually when I am rebuilding the gearboxes I find that the layshaft is worn at both ends 
They can be machined  true and I make bushes to suit
Before dismantling I check the end float and then make thicker shoulders on the new bushes to compensate
aiming for about 0.010 end float
If you need to add shims I would advise fitting the shim between the bush shoulder and sandwich plate
(bush has to be removed to do this)

HTH
John

[KeithJ]

John, very informative, thanks.  I am just in the process of machining new bushes so can reduce the end float on the layshaft.  Is it better to split the end float over both bushes or should it be done on one, if so which one?
Have you managed to turn the layshaft or does it need to be ground?

On the main shaft, the ratchet bush is a few thou too short to enable no float.  Should I make a longer bush?  Just needs to be about 0.005" longer.
ATB

[chaterlea25]

HI Keith,
I split the float between both bushes
The shafts will turn using suitable ceramic turning tips
Is the washer fitted between the bearing and ratchet bush?
If yes make a longer bush

HTH
John

[orabanda]

I was interested to find out recently that Lyford Classic Services stock undersize layshaft bushes; worn shafts can be turned down to suit.

Richard

[duTch]

 
Also don't forget to consider the thickness of a gasket (if any)..

 I think I was led to believe 5 thou Max on the layshaft.....not to say that's optimal 
 
Other thing I considered was how much the adding of shims (or bush flange) thickness to one end or the other would affect the relativity of the selector forks, and subsequent gear meshing....? Mainly because mine sometimes slips out of third under load, but where the selector rides in the camplate in third seems to be on the pointy bit, so if worn- no great surprise....!!!

 A small kind of off topic question:- when I was playing with my spare box (As we do), because I grafted close ratio gears in I needed to research something, and came across a rebuild project with a photo that shows the drive side layshaft needle roller oil feed hole just above the point where the two constant mesh gears intersect (kinda like at two o'clockish). Is this so on your box, as in my plunger box the hole is directly above the shaft.....?

 Just curious- if it was changed for ALL later models, or just the RRT2 box- I had a picture and the link saved on the computer that crashed and burned , so can't access it now, maybe later I'll do some forensics...

 cheers and  good luck with the bushes

[Topdad]

Thats good to know Richard, when I was doing my mates last year noone had them I keep note of that ,cheers BobH

[KeithJ]

HI Keith,
I split the float between both bushes
The shafts will turn using suitable ceramic turning tips
Is the washer fitted between the bearing and ratchet bush?
If yes make a longer bush

HTH
John

Thanks for the heads up for the washer on the kickstart ratchet, I'd missed it.  I have it in the box of bits but just ignored it!  That will sort out the missing few thou on the main shaft float.  Just as well I was checking out the assembly.  That means the mains haft can't have any end float.

With the position of the main shaft set, is there any way to check the "correct" engagement of the gears to be sure they are all meshing correctly i.e. the engagement of the dogs?

I was chatting to one of the recognised BSA spares and repair guys and he said he would not go less than 0.030" end float on the layshaft.  Unfortunately, I did not ask him why.  Any suggestions?  I wondered if it was to do with his experiences of getting a reliable operation and coping with the tolerances?

Also need to make another layshaft thrust washer 67-3203.  The original looks to be hardened steel and I wondered if ally bronze of phosphor bronze would be OK as I have some.  Also have some silver steel and EN24 but they are likely to deform after hardening and I can't grind it.

Just looking at Plate 6 of the 1954/57 spares list, the blue book, and there is an item 53 which is supposed to be the grub screw for the selector shaft.  It is obviously not as the grub screw is 53A and not listed.  I wonder why the big screw was drawn?
Will try to machine an old shaft and see how I get on.

Appreciate all the comments.

Keith

[chaterlea25]

Hi Keith,
To my way of thinking the position of the sliding gears is governed by the position of the camplate pivot
non adjustable !!
the selectors are well made and I have not found any variations in dimensions
Excess end float on the layshaft will allow first gear to move about , if too much it could possibly cause problems??
The other end  has the constant mesh gear which drives the sleeve gear in 1,2 &3rd gears and cannot move out of engagement
It should'nt be too hard to find the corrrect washer, Autocycle engineering ?? or Lightning spares ?? C&D Autos??

HTH
John

[Metty66]

The endfloat on the layshaft bit is interesting would that cause problems engaging first from neutral? What would be the cause and how would you deal with it?

[KeithJ]

"It should'nt be too hard to find the corrrect washer, Autocycle engineering ?? or Lightning spares ?? C&D Autos??"

Two of the three companies mentioned can't get the thrust washer. Have one coming from George Prew.  Interestingly, one supplier said it should be 0.057" thick.  Mine mine measures 0.092".  (I've two gearboxes and lost one washer).  I believe the part number is 67-3203 but don't have the parts list for the later s/a models.  Can anyone verify the number or thickness?

I think end float would be more likely to effect the amount of engagement rather than actually selecting a gear.  Might be the case though if it results in the cam plate/selectors forks getting out of position.  Would be useful to cut open a gearbox to see how all the parts inter react.  Any other thoughts?

ATB

[duTch]

  Ive wasted a fair amount of time the last few months doing my best to suss this out- but I'm sure there's a lot of folk who can readily answer most questions....

To my way of thinking the position of the sliding gears is governed by the position of the camplate pivot
non adjustable !!

 I agree, and my earlier comment re;

.... " would affect the relativity of the selector forks, and subsequent gear meshing....?'

,
 was considering the float of the layshaft relative to the (fixed) selectors...
     
 Keith, Am fairly sure 1st gear thrust washer is as you say 0.092", but think some research at the time came up with different figures (a bit thicker).
 I put the whole cluster together hanging out of the intermediate case, complete with selectors, but the camplate was all guesswork...
 Took some piccies, but they on the old phone..have to do some digging.

 I picked up a couple of G/boxes the other week, one will be ok with a cleanup- good camplate  , and only a couple of minor gear wear, .......however......
        I only wanted the outer cover from the other one, which going by the broken mount castings, should've expected ugly inside, but this was UGLY three gears with broken teeth at least 13..
 
    No doubt caused by the layshaft thrust washer on the WRONG SIDE of the 1st gear ....sad thing is, all the gears looked very good condition otherwise   

 One thing I did notice today when I stripped the better one, with regard to Orabandas story the other week, the camplate/sel. forks has I feel a bit excessive gap, which seemed to allow the lug to not seat snugly in the camplate grooves (just a bit sloppy)- more on that later