Using enfield gearbox with centrifugal clutch

Clutches, Chain & Belt Drives

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iron_monkey
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Using enfield gearbox with centrifugal clutch

Post by iron_monkey » Thu Aug 29, 2013 10:27 am

Hi, I am thinking of using a enfield gearbox without the clutch and putting a input sprocket on it instead. This sprocket will be driven by a centrifugal clutch mounted on the engine shaft. ie a semi-automatic.

The main issue is getting a 40/41# pitch sprocket that mounts on the enfield hex-spline layshaft, and somehow fixing it on the shaft. (only centrifugal clutches I see available are 40/41 pitch) The only way I can think of is to:

buy the stock enfield sprocket
buy a 40/41# sprocket with a bore larger than the spline shaft
drill two holes on the 40/41 sprocket
bolt the two sprockets together using two nuts.
Not sure how to fix this sprocket on the layshaft unless the layshaft has a threaded hole in the middle.

OR:

Use the threaded end at the tip of the shaft.
Fabricate a 40/41 sprocket with the appropriate threaded bore
screw it on

.........

Does the gearbox spline shaft also have a threaded hole in the middle (like a lawnmower keyway shaft) where I can bolt the sprocket at the end of it using a nut?

Is there anything I missed? I'm fairly new to all things motorcycle.


thanks

tappy
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Re: Using enfield gearbox with centrifugal clutch

Post by tappy » Thu Aug 29, 2013 6:02 pm

To mate to the gearbox I'd buy a standard enfield clutch centre from India (about £15) and mate a 41 tooth sprocket to that. You could do that in various ways. The centre is held onto the splines by a nut that threads onto a male thread on the gearbox shaft, protruding beyond the clutch centre.

I'm a bit unsure why you'd want to do this though - you won't be able to dissengage the clutch when changing gear. Ask Anorak_Ian on here, but my understanding is that the Enfield gear change is at best "unhurried" and at worst full of false neutrals - I'm not sure hurried, clutch-less gearchanges with an engine with a heavy flywheel will help that at all...

iron_monkey
I'm pretty new here..
Posts: 14
Joined: Thu Aug 29, 2013 2:15 am
Location: Sydney

Re: Using enfield gearbox with centrifugal clutch

Post by iron_monkey » Thu Aug 29, 2013 9:54 pm

Thanks, just the advice I need.

You're right, the enfield doesn't like clutchless gear changes. I suppose with a centrifugal clutch I have to back off the throttle every time I shift and wait until it reaches idle/near idle.

A harley/ultima gearbox is ideal but it doesn't look anywhere near as simple to implement.

alexanderfoti
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Re: Using enfield gearbox with centrifugal clutch

Post by alexanderfoti » Fri Aug 30, 2013 1:08 pm

iron_monkey wrote:Thanks, just the advice I need.

You're right, the enfield doesn't like clutchless gear changes. I suppose with a centrifugal clutch I have to back off the throttle every time I shift and wait until it reaches idle/near idle.

A harley/ultima gearbox is ideal but it doesn't look anywhere near as simple to implement.
Alot of centrifugal clutches dont disengage until the output shaft is below a certain rpm as well. So even that may not work.

Why not look at cutting up a 2 stroke engine/gearbox combo, this seems to be a popular way to get a gearbox and clutch. All you need to to is attach a pulley to the engine crank somehow.

tappy
I luv the smell of Diesel...
Posts: 227
Joined: Sun Jun 14, 2009 11:48 am
Location: Bristol, UK

Re: Using enfield gearbox with centrifugal clutch

Post by tappy » Sun Sep 01, 2013 6:14 pm

What's your objection to running a normal clutch with the Enfield gearbox?
What engine are you using?

iron_monkey
I'm pretty new here..
Posts: 14
Joined: Thu Aug 29, 2013 2:15 am
Location: Sydney

Re: Using enfield gearbox with centrifugal clutch

Post by iron_monkey » Mon Sep 02, 2013 3:14 am

The gearboxes are sold without the clutches. Purchasing the clutches separately are another dent on my wallet.

I also prefer semi-automatics, nice middle between the CVT and the manual.

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