Granny 1st gear choices & issues?

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Hi Steve,

Calculated by the number of teeth the 13/29 and 17/25 combo will give a first gear ratio of 0,305 or 3.28:1 (3.28 mainshaft revolutions for 1 sleeve gear revolution).
Standard Commando is 2.55:1.
Suppose you configure your sprockets in such a way that first gear will go up to 50 mph @ 7000 rpm then fourth gear (always 1:1) will go up to 164 mph @ 7000 rpm.

Cheers
Bert
 
I had been interested in custom gear ratios for some time for my P-11 dirt bike. I liked the ratios I had up to about 70mph which is a little faster than a newer 450 4stroke bike but I wanted to really leave them in the dust. So, after a few extra bucks came my way, I ordered a Tasman 6 speed to go with a new engine being built by Jim Schmidt. It took quite a while to arrive at the gear ratios I wanted for both MX riding and cross country. Bruce Verdon was very patient working with me on the ratios I wanted. I would have liked around a 3.20 1st gear but he convinced me the driver/sleeve ratio necessary for that would be too weak. He may still be shaking his head about my final ratio selection listed below:
Driver 18 / sleeve gear 29
- - - gears - Ratio
1st 16/30 - 3.02
2nd 20/28 - 2.26
3rd 22/24 - 1.76
4th 23/20 - 1.4
5th 25/18 - 1.16
6th -- / -- - 1.00
I am planning to run a Bob Newby Belt drive from classicycleworks and a 22 / 55 rear sprockets. This should be about 30mph at 6500rpm in 1st and 105mph top speed. I have to get the engine back and get it all together yet before I'll know how it works.
 
Steve,

the lowest first gear ratio you can get from RGM is their 13/29 first gear pair along with their 25/17 fourth gear pair. As johntickle pointed out, that will give you a 3.28 first gear ratio.

I think that's the lowest readily availble first gear ratio you can get for a Commando gearbox.

If you can find one of the wide ratio 23/14 high gear pairs to go with the 13/29 first gear pair, you will have a 3.66 first gear ratio. I think they came on one of the 500T trials models, but I don't know where you would get one. As far as I know, that's the lowest first gear ratio you could get.

Ken
 
Been told that , lower the ratio, stronger the gears/bearings have to be to handle the grunt. That's why some large single cylinder trail bikes have a tall 1 st so have to load the motor and not destroy the trans?
foxy
 
Bert. do ya mean there's two low gear T count options or am I confused by the 17/25, being top combo. 50 to 165 @ 7000 range is pretty close to what I was hoping for.

Kent, you perked me up to know others who like the wide scope of Nortons down and dirty to breezing hwy cruising. At some point Peel must have a ITT tranny to tolerate her pilot excess, so appreciate the exploring you've done with Bruce and enlightening me on what's available. A P11 is what 1st imprinted me n Norton in '71 and spoiled me for anything else, except for the high speed vibes. They are the Commando's daddy don't ya know.

Ken I'm numbed by numbers but your 23/14 teaser top set suggestion for granny 1st will send me on another world wide vendor quizzing again. Unity Cycle UK comes to mind as first to ping. Thanks goodness its the digital age as I could hardly understand half of what was said in the tone dial days.

Foxy, you bring up a definite issue I expect to have. Basics I understand is the faster the tranny turns for a speed the easier on the tranny and the engine. But low ratio multiple torque a bunch. I've not heard of thumpers needing tall low gears to protect the tranny supports. Your point leaves me confused now.

I want a granny 1st to creep along with and w/o feet down in less lug rpm, and also for no brake rolling burn out maneuvers and stunts. My thoughts for drag launch would be start in second then skip 3rd and hook on up in 4th to top out.
Peel re hub has on/off sprocket so can order up anything that fits.

Ok Peel will try the weakest lowest ratio 13/29 set first time out. My reasoning is I ain't gonna be dumping clutch on initial run in and me and Peel won't weigh over 500 lb total so might just leap forward of spin tire before it pops teeth. If it does then will have to have kinder gentler throttle hand til ITT box bought.

On that note I'm confused how many gears to pick. I live off pavement and like the off road play a lot, yet Peel's 'feather in cap' desire is surprising balloon tire bikes to over 160. I don't like shifting and I hate 3rd gear as its not low enough for much a passing gear yet 4th drops power band rpm for good pull unless Peel indicated 110, about as much as i could stand the 3rd gear delay. Maybe a 5 speed with more teeth meat than 6 spd, so if I needed passing gear pull could snick into them instead of skipping over 3rd. Past Peel 21T indicated 60 in 1st as tach swung into red zone and I swung my eyes back on bluff face dead ahead on 10 mph marked crooks. If I'd only known then that Peel could stand over 8000 I'd of held on longer. Thanks - made my dinner cold reading and writing but this is food for my soul.
 
Ive seen a wall of about 200 quitely rusting gears last centurie , A plethoria of ratios .

trials First was lowest . But the dommie / manx gears arnt the tough mk III tooth form .

Beach Raceing gearsets ? were any number of differant teeth ,for the lot .

To high on first ( tall ) and you loose the kickstart . No room inside it .
 
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