Fitting new layshaft bushes

[chaterlea25]

Hi All,
Morris, Almost all parallel reamers have a slight taper at the end to facilitate starting them into the part to be reamed
A suitably sized "David Brown" reamer with the special blades designed to go ream into a blind end part
The bushes could also be sized using a boring head if the gearbox housing was set up on a milling machine

John

[duTch]

 

Ok, but how far can you actually lift the drive end of the layshaft, in the Bush?

 Determining that with a bolt-on box is difficult to determine as there's no access cover like on S/A boxes....


 When I say I used 'emery tape', I mean the stuff on a woven material roll, which appears more 'glassy' than carborundum-y....just used 'emery' as a generic term 

[berger]

mmmmm generically speaking NOLI- ILLEGITIMI- CARBORUNDUM

[muskrat]

I had to look it up, just in case it was naughty.
Illegitimi non carborundum is a mock-Latin aphorism interpreted as "Don't let the b@st@rds grind you down".
Cheers

[duTch]

 

....."Don't let the b@st@rds grind you down"....

 ^^ I knew that sounded familiar ^^-  https://www.youtube.com/watch?v=3yAW1daYXD4  (wuz actually thinking it was Merle Haggard)

   and I found the tape I think I used - https://www.nortonabrasives.com/en-us/metalite-k225k227-ao-fine-grit-cloth-roll ...that was after I hand scraped it some.. long story...

[RDfella]

I don't see what all the fuss is about. If the layshaft is undersize, a reamer will not be of any use anyway. An adjustable reamer has a long projection at the end and, as Chaterlea says, even parallel reamers have a 'start'.
One needs a lathe, or access to one. Turn the outside dia as appropriate and bore the inner dia to suit the shaft (shaft dia + clearance + 1/2 x interference fit of bush in case). Job done.

[Steverat]

Yes I'm just waiting for the new bush to arrive then I'll get back in touch with my story!

Steve

[Steverat]

The new blind bush is here and it is bigger than all three of my layshafts (yes I now have 3). There may be a 4th coming soon, if that is smaller too then I shall just take the best fit, polish it in the lathe with some emery tape, and fit it. If it is too big for the bush, I think I'll just polish it a bit harder until it is right, or perhaps grind it by fixing my dremel in the toolpost. In any event, the bore of the bush will stay untouched. I just don't like the idea of working phosphor bronze with an abrasive.

[Swarfcut]

Steve.. BSA Service Sheet 702 gives the layshaft shell bearing finished dimension (we assume the blind bush) to be 0.687/0.688" internal bore. Published June 1951.

    Roy Bacon's book says 0.698",( this may be a typo error) so there is either an error or a change.

   Worth comparing with what you have. This should be the layshaft diameter plus a running clearance. If your new bushes are to this size, the shafts are wrong or have already been ground down.  Shaft the right size? Then the bushes are wrong part or incorrectly made.

 Swarfy.

[chaterlea25]

Hi All,
Before fitting the bushes to the case check that the bore in the casing is round and not scored,
I have found ovality in the bore's and scoring leads to oil leaks
There were some genuine BSA bushes for sale on ebay the other day only £25 each 

John

[Steverat]

Thank you S and C,
I'll measure my fleet tomorrow and report.

Steve
He of many layshafts
Gearbox type only

[duTch]

 For what it's worth, you probably better off cutting off the stop-end of the bush, and use that as a 'stop-end' (as previously mentioned is done with needle roller shafts), after you've reamed it if necessary- I did it to replace the welsh plug with my original box that I grafted CR gears into, but haven't to use it again yet (long story )

 May not be rivet-counter 'original', but I won't tell  (just between you & me and the internet )

[kiwipom]

hi guys, if i had to do this job i would sort the ovality (charterLea,s word) then get the bushes made that way they would be correct size, cheers

[Steverat]

Drive side

Layshaft journal sizes:
Shaft #1   0.683"
Shaft #2  0.676"
Shaft #3   0.674"

Blind layshaft bush sizes:
used bush  0.690"
new bush  0.688"

Timing side


S1  0.748"
S2 0.745"
S3  0.743"

I had to ream the existing timing side bush a touch to give S1 just 1 or 2 thou clearance, then fitted the mid casing cover. Layshaft runs freely inside with just zero endfloat. No point in creating unneeded endfloat so I'll assemble the box like that, and see if it works. When GB's box arrives I'll go through one more time to ensure I have the best parts then assemble properly with Loctite sealant. I have gaskets too but they will just create endfloat

[Greybeard]

Steve,
I've just taken the gearbox parts to my local Hermes pickup shop, so should be with you in a couple of days. The cost was £6.49. If you donate a similar amount to the forum I will require nothing more. I just hope you can use some of the parts.

https://www.a7a10.net/forum/index.php?topic=4439.0