gearbox questions

S

seattle##gs

VIP MEMBER
Joined
Oct 28, 2014
Messages
2,104
Country flag
I've built many gear boxes and there are re-occurring problems. When installing the inner cover the bolt holes never line up perfectly with the studs. I've spent hours identifying the offending stud or studs and widening the hole so the cover will fit on smoothly.
2nd...the mainshaft is usually off center with the small ball bearing. I can usually make it fit by pushing the shaft and rapping on the case with a soft hammer. But there is usually a conflict between the mounting studs and the mainshaft small bearing...mild to wild. A few months ago I replaced a kickstart shaft and the mismatch was so far off I spent three hours enlarging the stud holes...cut and fit...cut and fit. This was bought as a rebuilt gearbox. The builder must have had to use a lot of force to get the cover on. It worked OK but the shaft and case must have been under a lot of strain.
2nd box was yesterday. The inner cover was a bear to remove but I assumed it was 30 year old gaskets and gasket goo. Upon reassembly it was impossible to fit the cover without really shoving the mainshaft to the left and pounding it over the studs. Remove the shaft and it went on over the studs reluctantly but workable. The shaft is straight. The bearings went into the holes easily after heating the cases. I can't see how they could be crooked in the holes. After seeing these problems over and over I'm guessing the drilling and boring process was very slipshod. The inner cover rarely fits on smoothly.
I discussed this with AN and they said the new gb cases are more accurately machined these days. If I had several hundred$$ to spare I would buy a new case and inner cover. What are your ideas?
 
Never had that problem and I been into my GB a few times in the 49+ years, once for the layshaft bearing, 4 times for the KS pawl, once to replace KS gear and once to replace a broken KS shaft where it had broke at the pawl mounting, each time the inner case came apart and went back together as it should, still using the original studs and nuts, in fact everything else in my GB is original, I have owned my Norton since new.

Ashley
 
I have only rebuilt four gearboxes can have never come across your problems.
One that I have come across more than once is the fine threads for the outer cover stripping.
What genius put 1/4 (UNF?) in alloy, when, just in front of it, the timing cover is reliably held on with the much coarser 1/4 Whit?
I now just helicoil the lot to 1/4 Whit.
Cheers

Ha! just thought of something (Danger Will Robinson, Danger!)
It's no longer "standard" but the washer counters will never know! ;);)
 
Last edited:
seattle##gs said:
I've built many gear boxes and there are re-occurring problems. When installing the inner cover the bolt holes never line up perfectly with the studs. I've spent hours identifying the offending stud or studs and widening the hole so the cover will fit on smoothly.
2nd...the mainshaft is usually off center with the small ball bearing. I can usually make it fit by pushing the shaft and rapping on the case with a soft hammer. But there is usually a conflict between the mounting studs and the mainshaft small bearing...mild to wild. A few months ago I replaced a kickstart shaft and the mismatch was so far off I spent three hours enlarging the stud holes...cut and fit...cut and fit. This was bought as a rebuilt gearbox. The builder must have had to use a lot of force to get the cover on. It worked OK but the shaft and case must have been under a lot of strain.
2nd box was yesterday. The inner cover was a bear to remove but I assumed it was 30 year old gaskets and gasket goo. Upon reassembly it was impossible to fit the cover without really shoving the mainshaft to the left and pounding it over the studs. Remove the shaft and it went on over the studs reluctantly but workable. The shaft is straight. The bearings went into the holes easily after heating the cases. I can't see how they could be crooked in the holes. After seeing these problems over and over I'm guessing the drilling and boring process was very slipshod. The inner cover rarely fits on smoothly.
I discussed this with AN and they said the new gb cases are more accurately machined these days. If I had several hundred$$ to spare I would buy a new case and inner cover. What are your ideas?
Click to expand...
Maybe the inner cover was not the original OEM cover, the dowels that align the cover should match nicely too. I've seen the MS small bearing cocked as the factory pressed it in, so swarf (scrapings of the bore) got into the seating area as the bearing was being forced in, so I know to clean the bore, and I made a tool to check that the bearing is seated squarely. I do heat the cases so the bearing slides in nicely.
 
You are probably right. I found multiple references to BSF at the AJS/M forum. The fact that socket head cap screws are not available for CEI screws also points at BSF.

Pull-out strength in aluminum is probably higher for 55 than 60 degree threads because the thread profile is wider for the same pitch. There is hardly a difference otherwise. I guess it boils down to engineering practice.

- Knut
 
Carl H said:
Maybe the inner cover was not the original OEM cover, the dowels that align the cover should match nicely too. I've seen the MS small bearing cocked as the factory pressed it in, so swarf (scrapings of the bore) got into the seating area as the bearing was being forced in, so I know to clean the bore, and I made a tool to check that the bearing is seated squarely. I do heat the cases so the bearing slides in nicely.
Click to expand...
Always possible that the covers are mix and match. I tried 2 other inner covers with the same result. I always use heat to drop in the bearings.
 
L.A.B. said:
Yes although I've a feeling John Hudson said they were BSF in his gearbox rebuild video which I can't play as I no longer have a VHS tape player.
Click to expand...
Aw LAB, get it converted to a DVD. I don't know about your locale, but video studios offer that service for a reasonable fee.
I still have a VHS player and software to convert to DVD plus an audio cassette player. I'm such a dinosaur!
 
I have found a couple of earlier Dommy innercovers to have mainshaft bearing housings that were very tight causing the bearings to be "notchy" when installed . i swapped the bearings for ones with more internal clearance , perhaps this is part of the problem .
 
There might be a difference between AMC and Norton gearboxes which look similar. I have a Norton gearbox which I presumed was Commando - the Manx gear cluster fitted straight into it without a problem, and I did not expect a problem. But if the cases have minor differences - that might be a problem.
 
acotrel said:
There might be a difference between AMC and Norton gearboxes which look similar. I have a Norton gearbox which I presumed was Commando - the Manx gear cluster fitted straight into it without a problem, and I did not expect a problem. But if the cases have minor differences - that might be a problem.
Click to expand...
Al - Norton boxes were AMC since the fifties! :rolleyes::rolleyes:

Are you really interested in Norton?
 
The AMC box was developed from the current Norton box when they bought Norton, but the Norton box was a redesign of the Sturmey Archer box which Norton had bought the rights for when Sturmey Archer announced it was stopping production.

Sturmey Archer
Dolls Head
Upright
Laydown
AMC
 
It's actually a fair point. AJS & Matchless boxes do look similar to the Commando box, but there are numerous differences - the mounts, the clutch cable entry position, kick-start shaft, spring, mainshaft, gear profiles, etc. Very few interchangeable parts - maybe the selector mechanism?
 
Deckard said:
Aw LAB, get it converted to a DVD. I don't know about your locale, but video studios offer that service for a reasonable fee.
I still have a VHS player and software to convert to DVD plus an audio cassette player. I'm such a dinosaur!
Click to expand...
Getting hard to find DVD players these days too! Perhaps get it captured to MOV format and saved to a USB drive/uploaded to GoogleDrive or YouTube. There is no great future proofing anymore.
 
B+Bogus said:
It's actually a fair point. AJS & Matchless boxes do look similar to the Commando box, but there are numerous differences - the mounts, the clutch cable entry position, kick-start shaft, spring, mainshaft, gear profiles, etc. Very few interchangeable parts - maybe the selector mechanism?
Click to expand...
I thought the complete clusters were interchangeable?
I know I've fitted a commando output shaft into a box that came from an atlas
Although you don't really have to do this anymore with the clutch centre adapter from rgm
I know my mates commando has a pre commando gearbox or she'll at least because it has a full width top mount and an earlier number
 
baz said:
I thought the complete clusters were interchangeable?
I know I've fitted a commando output shaft into a box that came from an atlas
Although you don't really have to do this anymore with the clutch centre adapter from rgm
I know my mates commando has a pre commando gearbox or she'll at least because it has a full width top mount and an earlier number
Click to expand...
I think the gears may be interchangeable as a set, but not as individual gears.
I recall seeing a list with all the different types and associated ID stamped on them, but it was a long time ago.
Note I said AJS & Matchless, not Norton ;)
 


Write your reply...

Similar threads

S
  • Locked
very nitpicky gearbox questions.
Replies
19
Views
1,586
Nortoniggy
Nortoniggy
S
Norton gearbox # 142754
Replies
15
Views
899
Torontonian
Torontonian
R
New project Introduction and questions
2
Replies
38
Views
2,248
htown16
htown16
J
Which gearbox do I have?
Replies
4
Views
300
Fast Eddie
Fast Eddie
jms
1967 Norton Atlas Gearbox
2
Replies
25
Views
1,080
jms
jms
Back
Top