Welding a sprocket onto the side of an existing one.

[tensor47]

Hi,

I'm using a motor cycle engine in the back of a space frame for a single seater hill climb car.

To get 4WD I need to have a stub shaft from the normal gearbox output sprocket and from it use a CF toothed belt to the front axle ass'y.

I want to use a duplex chain coupling and this means welding a sprocket onto the side of the existing output sprocket.

It appears that some sprocket manufacturers use 16Mn Cr5 which is equivalent to SAE 5115 according to the texts.

Nowhere can I find if this material in it's final hardened state is tig weldable and how to do it so maybe someone here knows about this.

Also it may need to be normalized and re hardened after the welding.

Can anyone shed any light on this please.

Cheers

John

 

[TVP]

The sprocket will have been case hardened (carburized) to a depth ~ 0.3 mm to 1.0 mm. I would not suggest TIG welding onto the existing sprocket.

 

[MikeHalloran]

A welded sprocket _will_ break, so it at least complicates your logistics.

Instead of a stub shaft coaxial with the output sprocket, consider a jackshaft parallel to the output sprocket but offset back or up. Then the stock output sprocket drives the jackshaft by a short length of chain to a similar sized sprocket, and the jackshaft drives front and rear by other chains or belts.

Mike Halloran
Pembroke Pines, FL, USA

 

[tensor47]

Thanks very much for your definite positions on this issue of welding.

I'm now thinking of grinding off the hard layer from the relieved face anulus and making a precision relieved anulus of it. Then I can drill and ream about 8 or 10 holes 1/4" dia in it to attach it to a 4140 machined, drilled and tapped sprocket, which will be hardened and tempered.
I could also have the add on sprocket and it's drive shaft pair nitrided for extra life.

They are 17 tooth 5/8" pitch sprockets so the drill hole pcd won't be large and the tight side chain or belt tension calc value as I drop the clutch is 1100 lb.f.
What do you think ?

The second shaft idea is a valid one and has been looked into previously, but the complexity, weight and space rule it out.

Cheers
John

 

[btrueblood]

Why not machine, harden & temper a brand new, dual sprocket?

 

[tensor47]

Thank you for your suggestion, and yes, that is a looming possibility.
The main reason for not going that way is the spline is a nice slight interferance fit on the shaft. Getting the all new compound sprocket internally splined with just the right fit to prevent fretting is an unknown, and pretty expensive.
Cheers
John

 

[TVP]

Your bolted concept is much better than the welded one, in my opinion. Since the 4140 part will be quenched and tempered for optimal fatigue strength and not wear resistance, nitriding it after Q&T is a good idea too.

 

[dvd]

I don't really understand what the thing is supposed to look like. It seems like the overhung load on the engine shaft is going to increase resulting in bearing/shaft failure. Is there a sketch of this arrangement available to illustrate the concept?


MikeHalloran's suggestion of a jack shaft sounds like a good idea.