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perfect.tommy
perfect.tommy
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You'll have to ask John Hill about the mainshaft spline but i think they just use the run out.
You can set the alignment at the engine sprocket with shims.
78 links should be ok with 48 i think (standard is 80)

Orange would be a suitably horrible colour eh? Don't make it blue or you may upset SRM........

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Last edited by NickL; 04/25/21 4:49 am.
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That calculator only gives approximate centre distance. The A65 has 6.6875" centre distance. Chains are only available in even pitches (half links are unacceptable). With the 28/58 teeth sprockets the calculated chain length is 80.0093 pitches. Calculating teeth down to 50 for the clutch does not result in a chain length close enough for the adjuster to an even link. Changing the engine sprocket teeth to 27 gives a 79.0093 link for a 57 teeth clutch and a 26 teeth engine sprocket gives a 78.0093 link for a 56 teeth clutch. The ratio is going up, not down.
Given how many primary cases have gouges from loose chains it would not be wise to go to a larger engine sprocket.
Here is a print of the longer 5spd high gear compared with the Triumph version. I have to lengthen the roller land width. The gear it was modelled on was an earlier version with narrower rollers. That is the RJ009 which has 0.394" wide rollers.
[Linked Image from live.staticflickr.com]

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Spline has a circlip from memory, I added a washer for alignment. It's so much easier to remove the clutch centre. No need for massive torque on nut. Apparently the ball ended plunger doesn't fit this but it would be good if one could. Maybe the cam plate pushes it too far in or something? It's virtually impossible to select neutral when stopped. But easy enough when still rolling. Gavin adjusted his to select better in that 1st N area. If and when it comes out sometime I'll have a look, maybe the N indent could be deeper because it goes across it into the next gear. Which is handy in a way. The back cut pulls the gears in when selected.

That bearing can be replaced with one half the width and have a proper seal on the outside. Mine uses the primary for breathing and dust covers do not cut it.

Ratios on this are perfection. Nothing like what Quaif built for A65s with strange ratios worse than stock with 4th and 5th far far apart, worse than the Triumph 5speed even. These help the engine and keep it right in the power. Never lacking for a good gear when following the Aprilia Michael owned for a while, the 4speed had less choices.

[Linked Image from i.postimg.cc]


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Dave, i ran a 33 tooth engine for years on my old crate with 82 link pre stretched duplex chains.
I had the alternator housing machined off. I ran a 32 before i used 33 but 33 made chains last longer.

This is the old type cases so no alternator but 28/47 comes out ok. at 6.75in 1.68-1 is good as a ratio.
I may run a t140 29t engine and try as well.

I like the proposed top gear setup, now i see what you mean.

https://imgur.com/K5LQV5W

Last edited by NickL; 04/26/21 2:54 am.
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That 'box looks bloody lovely!

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I think I use a 16005 bearing and narrow seal which is the same od and fits the 5speeds extension. You can use a spacer machined for the std shaft size and that bearing, and the tube can be pushed back a bit so it has space, and run in the std seal on a stepped section at the back. I also use that bearing outside the alternator. It's narrow but doesn't fail.

Though what a sidecar does who knows. That G/box is like jewelry. How strong it is with a chair I don't know, I thought the std ones were pretty good. I have a Triumph 5speed main shaft in the shed that's snapped in half.


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After talks with Allen, I changed from the stock range of ratios to a wider gearset with 1st at 2.786. I came up with two options for in between. One has a more straight line in the MPH/shift curve, the other drops off more. A disadvantage of the ratios that drop off more is it needs a different cutter for one gearset. The more linear gearset can be cut with one Module cutter set.
I found the Norton also uses a circlip to butt up the clutch hub against.
I think the needle bearing in the door would be the best option. The root of the output sprocket spline is 34.29mm. The high gear seal is 1.1875" (30.16mm) so nothing else fits without grinding the inner race.
BSA racing colours were red/white so red would be an option. When I had the rebuildable sliders hard anodized clear they came out sort of olive drab. That would be an interesting choice.

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This is the hub and drum (tapered shaft version) print
[Linked Image from live.staticflickr.com]
I will make a splined version when I have a shaft.
A 16005 bearing has a 25mm ID. Unlikely the high gear extension is that small. The Triumph 5spd high gear uses a 1-1/16" OD needle.
A 47 tooth clutch would be tough to fit. The plate tabs are 5.648" and the pitch circle of a 47 tooth is 5.614". The clutch plates and drum flange would have to be moved outside the chainwheel and there is no room for that.
If a 29 tooth engine sprocket will fit, a 54 tooth chainwheel gives a 78.0544 link chain (0.0204" longer than exact) and 1.862:1 ratio. If you are going to do that then might as well change over to Hyvo chain and cut off another 1/4" of width.

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Hmm, i hadn't even considered a hyvo type chain.
My concern is that they require very good alignment and with
all the bending and flexing that goes on here i wonder how
they would behave and how well they would wear. Also the
wear rate on the clutch drum would be high with 54t, would
53t go?

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If you remember, there used to be a Hyvo chain and sprockets for the original stock clutch back in the day. I do not know how well it worked and have only seen a picture of it.
With the sprocket door bearing there should not be much flexing at the clutch and if you use an outrigger bearing on the crank like what Mark has done everything should stay in alignment fairly well.
If going from 58 teeth to 54 is going to increase the wear rate a 53 is going to increase it more. And a 47, as you originally wanted, would be worse still.
With a 53 tooth you need a 30 tooth engine sprocket.
I got the chain length error backward, with a 29/54 sprocket pair the required length is 78.0544 pitch, a 78 pitch is too short. A 30/53 tooth pair requires 77.918 pitches (78 pitch is 0.03075" too long).
A 53 tooth reduces the radius by 0.298".The cutout for the side plates would be within 0.010" of the clutch plate tabs. Not much meat left.

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Looks like i'll be looking for a larger engine sprocket.
Odd numbers are always better i've been told as far as wear goes.
I may as well just see if i can find a triplex 32t and use an 82 link again
with standard 58t clutch.

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A 29/54 (1.862:1) ratio is not low enough? A 32/58 is 1.8125:1 that is less than a 3% change. At 7500 RPM the clutch speed is 4028 versus 4138 for the 32/58.
I think the odd number of teeth is analogous to a hunting tooth ratio in gears. A 78 pitch chain takes 9 revolutions to come back to the same tooth on a 54 tooth sprocket.
I will have to make 58 tooth chainwheels for people who want to keep the original ratio. Although, people with comical hubs are always complaining about not being able to put a smaller sprocket on the hub and 21 tooth gearbox sprockets need the door opening widened.
For a 20/47 rear sprockets and 26" wheel radius the 29/54 has a top speed of 132 MPH and the 32/58 is 136.

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Dave, if you produce a 58 and i can run a 33 on the engine it gives me 1.757-1
the standard a65 ratio is 28/58 so that's 2.07-1
At 6500 rpm that's 3700 vs 3140 a 500+rpm change = nearly 20% so it's worth while.
It made a difference when i did it before. Anything is better than nothing when it comes
to running these boxes faster. I will see if i can get a t140 sprocket and see if it fits first up.
I may have a triumph crank around somewhere with a sprocket on it, just need to try it.
I don't want to waste your time if you are just going to produce a standard one, i'll just
have to work round it. Just that renold don't do pre stretched chain anymore. We run a 17
on the gearbox output side, can't use a 16 as it fouls the cases. If you do end up making
a 54 then i'll go for that naturally, it'll speed the box up by 400+rpm so, great.

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Making different tooth chainwheels is not a problem. I already blanked out an engine sprocket for the A65XS, have to put it on the rotary to cut the teeth then have the spines cut. A local shop specializes in broaching. If you need one off engine sprockets I can do it. The major cost is heat treating which has a minimum charge but you might be able to get that done locally.

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That's very handy to know Dave, please advise via mail cost of doing a 32
engine straight away. OR a carrier that fits on the a65 spline so i can turn up
piloted sprockets and bolt them on. I can get the heat treatment done here.
The triumph sprocket doesn't fit, the spline is smaller.
No-one around here will do the spline for it, i was looking at turning the centre
out of a standard one and doing it that way.

As an aside 34-57 with 82L looks good...........

Last edited by NickL; 04/28/21 12:10 am.
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Basket, drum and hub
[Linked Image from live.staticflickr.com]
I will widen the base of the tab tangs and notch the outer edge. If this were made from steel like for the B50 then just notch the edge.
The roll pins, dampers and plates are KTM 450. Add on top the KTM pressure plate and diaphragm spring. Barnet sells a 20% stronger spring.

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Hy-vo chains are meant to be the thing, from what I've read. The triplex that stays in line seems ok, though when they pull out of line the teeth hit the side plates and it looks like they push them off, then it fails. The original chains seem better riveted, or hold better. The 1200 Laverda triples used the same chain but regina I think. Bens BSA has a new regina that looks good quality. The Laverda may have bigger or better supported shafts.

Last edited by Mark Parker; 05/01/21 2:06 pm.

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That's why when i raced i used a duplex chain, they actually lasted longer as they
stood the flexing better. I couldn't get a crank outrigger in there with a 33t sprocket.

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