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fitting an open belt primary to a Sport Scout motor

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steve_blackbob

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Location: highlands of scotland

Post Thu Dec 21, 2006 2:49 pm

fitting an open belt primary to a Sport Scout motor

same bike another topic!

I am planning to use a Triumph 4 speed gearbox with my stroker SS motor, as I have a spare hayward belt drive kit to suit the gearbox, I thought I would try the kit for size, everything looks like it will line up nicely, but I will need to get the front pulley machined to suit the Indian crank pin's taper

any idea what the angle of the taper is?
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ironwigwam

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Post Thu Dec 21, 2006 5:43 pm

primary belt

Steve,
Its actually real simple trig, Just measure big end OD, small end OD and the length. Subtract the small end from large end, divide by two and use the length for a right angle triangle and use your calculator or the chart in your machinery handbook.
Otherwise I would have to dig thru my parts drawings and find my scout adapter drawing. I use a steel insert on the shaft and have the aluminum belt pulley bolted and pinned to it with the electric starter drive lug bolted to that.
Rocky
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steve_blackbob

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Post Fri Dec 22, 2006 1:22 am

cheers Rocky, i should have worked that one out for myself - just lazy :oops:
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ironwigwam

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Post Sat Dec 23, 2006 9:19 am

Steve,
keep in mind after the you machine the taper on lathe , you will need to slot the keyway at the same taper on your slotter/shaper, then if you have to change pulley size tomake belt fit, you do it all over again. Might be easier to use a steel insert for pulley driver and machine pulley's to fit
Here is my take on a 5/6 speed in scout.
Rocky
1957S/VG
Image[url]
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steve_blackbob

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Post Thu Dec 28, 2006 2:10 am

ironwigwam wrote:Steve,
keep in mind after the you machine the taper on lathe , you will need to slot the keyway at the same taper on your slotter/shaper, then if you have to change pulley size tomake belt fit, you do it all over again. Might be easier to use a steel insert for pulley driver and machine pulley's to fit
Here is my take on a 5/6 speed in scout.
Rocky


that looks like the smart way of doing it, the I spoke to Tony Hayward the belt drivekit supplier, he can supply me front pulley blanks, just drilled with a pilot hole, if I can make up an Indian adapter centre then i can change pulleys easily
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ironwigwam

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Post Thu Dec 28, 2006 5:02 am

Steve,
Where you get into trouble with belt drives is that the belts are not supplied in half inch increments for the different pitch and width belts that are used. So you are forced into finding a belt length that is close to your engine and trans center with the number of teeth you need that fits your clutch hub, then either increasing the engine pulley in tooth count too fit or moving the trans, front, back or sideways to make the belt fit. In my case the belts came in three lengths that were one inch longer 4 inches less and another that was 3 inches longer, so I turned the 5 speed on its side and I had a belt drive.
Have you looked at belt lengths yet?
Rocky
1957S/VG
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steve_blackbob

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Post Thu Dec 28, 2006 2:00 pm

i am working towards keeping the clutch centre to crank centre the same as a pre unit triumph, that way I can use off the shelf Triumph belts - just hoping the gearing works out ok - suck it and see 8)
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steve_blackbob

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Post Thu Feb 15, 2007 1:45 pm

I have been working on the gearbox mounting today.

I changed out the Sport Scout rear frame section for a rear section from a 741 frame that I have, there is much more room for the Triumph gearbox to sit down in the frame using it. By moving the box back slightly from the Indian position, the Triumph box will sit neatly in the frame with room for mounts and give room at the top to use the Triumph primary adjuster brackets and adjuster which will mount to a threaded round bar running between the rear Indian engine/trans plates - neatly providing primary belt adjustment.

Mounting the box slightly to the rear has two advantages, firstly, the front and rear pulleys will be 11.5" centre to centre - the same as a p u triumph and secondly there will be more room to mount footpegs between the trans and engine.

Image
Last edited by steve_blackbob on Sat Feb 17, 2007 11:13 am, edited 1 time in total.
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ironwigwam

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Post Sat Feb 17, 2007 5:36 am

Steve,
Shaping up nicely. How does the center of transmission work out to center of engine?
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steve_blackbob

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Post Sat Feb 17, 2007 11:12 am

I've got it set at 11.5" at the moment, whicjh is the same as a rigid framed (long case) Triumph primary, centre to centre. I am just off the phone to Tony Hayward and he will supply me alloy frnt pulleys with just pilot holes, ranging from 24 tooth to 30 tooth, and can do belts up to 105 tooth 101 tooth being standard long case Triumph.

So I'm off down to the workshop to count teeth :lol:

as for centreing the other way (side to side) the pulleys seem to line up, by eye, ok, once I have the mounts welded in to the frame I will be able to space the gearbox to suit the final drive chain correctly, then set up the front pulley to suit the gearbox one. It looks as though it will simply be a case of turning the triplex teeth off a standard Scout front pulley on the lathe and turning the Hayward front pulley down to give a good fit at the right spacing.
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ironwigwam

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Post Sat Feb 17, 2007 7:00 pm

Steve, I meant the center from top to bottom? Is the center of clutch hub,up and down centered with engine up amd down? It appears the trans sits lower. How does that affect rear chain line up?
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steve_blackbob

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Post Mon Feb 19, 2007 7:32 am

as it sits in the photo, the transmission centre is sitting 25mm higher than the crankshaft centre, this will be reduced/resolved when I fabricate the mounts. I will be able to lower the transmission once I lose the tubular cross brace, which will be replaced (maybe) slightly further back. I am debating (with myself :shock: must be an Indian induced problem) whether to make a set of rear engine plates with extended trans bottom mounts or to make a new lower frame cross shaft/brace with incorporated trans mounts, the second option would save trimming the lower boss on the Triumph box, and probably be a neater solution.

The next big tin of worms is working out the drive ratios, as I'm still undecided as to whether to use 18" rims or 16"
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Oldschool

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Location: Muncie, IN

Post Thu Apr 12, 2007 10:02 am

Steve, Do you know what year and model Triumph gearbox you have? Also, can you run the Hayward belt drive dry? Thanks.
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steve_blackbob

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Post Sat Apr 14, 2007 2:04 pm

Oldschool wrote:Steve, Do you know what year and model Triumph gearbox you have? Also, can you run the Hayward belt drive dry? Thanks.


box is from a '52 T100, and yes you can run them dry, Ive got one on my Triumph Bonnie bobber
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Oldschool

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Post Tue Apr 17, 2007 9:58 am

Thanks for the info, Steve! I apologize, but one more question... Does the Hayward belt drive have a sealed bearing? Or the loose rollers?

I've been trying to figure out a way to machine my clutch basket to put in a sealed bearing rather that the rollers, but does not look like there is enough meat.
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steve_blackbob

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Post Tue Apr 17, 2007 4:06 pm

I looked at ways to fit a sealed bearing too, but there isnt much space there!
looking at ways to fit a Scotoiler (drive chain oiler) to lube the plain rollers
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Oldschool

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Location: Muncie, IN

Post Mon Apr 23, 2007 1:52 pm

That is a good idea. Definetly shows that there is more than one way to skin a clutch!

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