Gearbox shell failure

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mdt-son

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Hello all,
I saw this image in an ad on Fleebay, and am wondering what may have caused the damage. Obviously the layshaft rotated in the xz-plane including the bearing, and considerably so.
Could bearing lock-up alone have caused this? Any ideas or past experience?

Thanks,
Knut

Gearbox shell failure
 
Most likely someone over did the insertion of a bearing, seen that damage a few times caused by Gorilla's with big hammers who do not know when to stop.
 
Onder said:
Looked up AN to see what a new shell goes for:
andover-norton.co.uk

Andover Norton - GEARBOX SHELL (NOT MK3) (06.0808) - 06.4126

GEARBOX SHELL (NOT MK3) (06.0808)
andover-norton.co.uk

In truth that isnt a bad price all things considered. Have to wonder if they crack between the two bearing recesses as per factory.
I guess Im amazed you can actually buy one and it looks nicely made too.
Click to expand...
I took find it amazing that you can buy stuff like this
It's also absolutely brilliant IMO
 
When my Portuguese bearing failed on the end of the layshaft bearing it cracked the case in the exact spot as pictured. I took it to a welder who specialized in cast aluminium. He fixed the hole without protruding out too far and it has not leaked a drop in 30 years. I only had to file a very small amount off when I fitted a 520 "o" ring chain. FWIW.
Ride On
Dave
 
I am toying with the idea of milling off the damaged end of such a housing, replacing it with a high-strength aluminum or steel cover. Yes, it will entail some welding and machining work.
This would be an opportunity to specify other bearings and increase wall thickness between bearing outer rings to get rid of the web cracking.
Does anyone know which alloy the main shell is made of?

- Knut
 
mdt-son said:
I am toying with the idea of milling off the damaged end of such a housing, replacing it with a high-strength aluminum or steel cover. Yes, it will entail some welding and machining work.
This would be an opportunity to specify other bearings and increase wall thickness between bearing outer rings to get rid of the web cracking.
Does anyone know which alloy the main shell is made of?

- Knut
Click to expand...
I bet someone at Andover Norton knows. Call/email
 
The alloy today is very different, a massive amount stronger and hot isostatic pressed as well to get the strength to the top end of the range for the material used.
 
mdt-son said:
I am toying with the idea of milling off the damaged end of such a housing, replacing it with a high-strength aluminum or steel cover. Yes, it will entail some welding and machining work.
This would be an opportunity to specify other bearings and increase wall thickness between bearing outer rings to get rid of the web cracking.
Does anyone know which alloy the main shell is made of?

- Knut
Click to expand...
Save time, go buy a new, better one from AN. Use the saved time to get your Nortons on the road
 
dobba99 said:
Save time, go buy a new, better one from AN. Use the saved time to get your Nortons on the road
Click to expand...
You are right. A new shell is on the bench. The idea proposed here is a project for the future.
nortonmargie said:
I bet someone at Andover Norton knows. Call/email
Click to expand...
Andover is reluctant to share such details. If nobody knows, reverse engineering by having a specimen analyzed is the only solution.

- Knut
 
mdt-son said:
You are right. A new shell is on the bench. The idea proposed here is a project for the future.

Andover is reluctant to share such details. If nobody knows, reverse engineering by having a specimen analyzed is the only solution.

- Knut
Click to expand...
Andover won't tell you what they are using now, but will probably cheerfully explain what was used in the past, with a thorough explanation of why that alloy was much inferior to present technology
 
It is most likely from being bashed in.
A good deal of the drama with these bikes is previous owners or thoughtless procedures.

I remember a post where someone asked about holding the sprocket to tighten the nut (70 ft/lbs) One peanut who seems to fancy himself posted a photo with a socket against one tooth and up against the frame (a short arm fulcrum) which is probably the worst thing you could do.

The irony or perhaps idiocy of it was the genius had drilled lightning holes in the sprocket which a simple homemade two pin bar could have engaged to avoid any stress to the gearbox and casing.
What a maroon.
 
The old material was DTD 424 or LM4, nothing special, and not even the best they could have used back in the day. If you weld repair and return bearing recesses to standard, then best of luck to avoid cracking.
 
Time Warp said:
I remember a post where someone asked about holding the sprocket to tighten the nut (70 ft/lbs) One peanut who seems to fancy himself posted a photo with a socket against one tooth and up against the frame (a short arm fulcrum) which is probably the worst thing you could do.

The irony or perhaps idiocy of it was the genius had drilled lightning holes in the sprocket which a simple homemade two pin bar could have engaged to avoid any stress to the gearbox and casing.
What a maroon.
Click to expand...
Well, that peanut/genius/maroon.. would be me then :

Gearbox shell failure

I have around 500 000 km on 2 Nortons (and a few more..), and over the years I have made them into very reliable traveling partners.
That doesn't mean that I can't learn something more .
Please explain where you see a problem.
70ft/lbs ?.. a fraction of what that sprocket will see under acceleration or bump starts.
The gearbox in the pic. is doing great, after 200 000+ km and many sprocket changes.
(In fact, I am going to change one tomorrow..)
 
Last edited:
Knut,
Alongside Madnorton - a "strengthened" shell from RGM is made from LM25 TF material. Still has the same failure point/thickness area of a stock case....guess I'll find out one day........

Sean
 
Time Warp said:
It is most likely from being bashed in.
A good deal of the drama with these bikes is previous owners or thoughtless procedures.

I remember a post where someone asked about holding the sprocket to tighten the nut (70 ft/lbs) One peanut who seems to fancy himself posted a photo with a socket against one tooth and up against the frame (a short arm fulcrum) which is probably the worst thing you could do.

The irony or perhaps idiocy of it was the genius had drilled lightning holes in the sprocket which a simple homemade two pin bar could have engaged to avoid any stress to the gearbox and casing.
What a maroon.
Click to expand...
WTF ?

Out of order sir.
 


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