Jackshaft gearing
09-10-18, 01:20 PM
#3
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YEEES! I can finally posts pictures! Cool I’m buying a sbp jackshaft for my four stroke with Alfine 8 inter hub in the back. I fb messaged sbp but not that helpful. I’m here to looking for input not advice. Advice to me would be someone insisting I don’t change the gearing. Sbp said when purchasing I can mention in the invoice that I want 24 and 30 tooth chainrings. The pictures I shared are of the gears that I’m now interested in. Their four stroke kit comes with a 9 and 17 tooth gears there. They have optimal gears of 10 11 and 21 tooth. What do think if I were to put two 10 tooth gears right there?
09-10-18, 01:51 PM
#5
Mechanic/Tourist
No advice from me. My input - I'd say jacked up, rather than jackshaft. A forum for motorized bikes and conversions would serve you better.
09-10-18, 07:28 PM
#7
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But you'd have a higher top speed, theoretically. Wind resistance and other factors might limit that. You might not like the trade-off. I'd price the gearsets over the counter and buy the unit stock with an eye to replacing gears if I did not like the stock setup.
Last edited by thumpism; 09-10-18 at 07:31 PM.
09-10-18, 09:17 PM
#8
Mechanic/Tourist
It's really no different with a mechanical engine than with a human one. If the power is not sufficient a higher gear will not result in higher top speed, merely lower rpm. The OP might also want to start up on a downhill, considering the torque will be very, very poor.
Last edited by cny-bikeman; 09-11-18 at 06:37 AM.
09-11-18, 07:54 AM
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Looking at those pics, it looks complicated, lol.
to the OP, what is it about the 10t/10t that interests you? That's essentially setting up a 1 to 1 ratio so any torque multiplication happens through your gears only. I would think if you were going through the trouble of something that looks this complicated you'd want more output from it.
to the OP, what is it about the 10t/10t that interests you? That's essentially setting up a 1 to 1 ratio so any torque multiplication happens through your gears only. I would think if you were going through the trouble of something that looks this complicated you'd want more output from it.
09-11-18, 08:29 AM
#11
Banned
>>> but really this is not a petrol bike forum.
there is a tiny sub section of the electric bike section for fuel powered bikes and conversions..
Gas, Gashol, Alcohol or Diesel, & Alternative Powered Bicycles
adult tricycles, the jack shaft is a 3 speed with a cog on the hubshell
turning at a different rate, than the chain from the crank, drives the internals, then the hubshell cog, via , a short chain, drives a free-wheel, fixed to 1 wheel's axle drive shaft.
....
there is a tiny sub section of the electric bike section for fuel powered bikes and conversions..
Gas, Gashol, Alcohol or Diesel, & Alternative Powered Bicycles
adult tricycles, the jack shaft is a 3 speed with a cog on the hubshell
turning at a different rate, than the chain from the crank, drives the internals, then the hubshell cog, via , a short chain, drives a free-wheel, fixed to 1 wheel's axle drive shaft.
....
Last edited by fietsbob; 09-11-18 at 08:40 AM.
09-11-18, 11:50 AM
#12
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By rough guesstimates looks like a 60:1 rpm reduction from motor shaft to bottom bracket axle. Since most of us have pedal cadences in the 30-110 rpm
range, that should give you some idea what the engine will do from idle to top rpm motor shaft. You can interpolate speeds by looking at the alfine internal
ratios multiplied by the ratio of the driving CW to the alfine hub cassette gear. If you take the final ratios and multiply them by the actual tire diameter in
inches you will end up with "gear inches". A long time ago I figured out that 100rpm cadence in a 100 gear inch would result in a speed of 30 mph.
How that will work out with your alteration, depends on the motor shaft torque.
range, that should give you some idea what the engine will do from idle to top rpm motor shaft. You can interpolate speeds by looking at the alfine internal
ratios multiplied by the ratio of the driving CW to the alfine hub cassette gear. If you take the final ratios and multiply them by the actual tire diameter in
inches you will end up with "gear inches". A long time ago I figured out that 100rpm cadence in a 100 gear inch would result in a speed of 30 mph.
How that will work out with your alteration, depends on the motor shaft torque.
09-11-18, 01:24 PM
#14
Banned.
Thread Starter
>>> but really this is not a petrol bike forum.
there is a tiny sub section of the electric bike section for fuel powered bikes and conversions..
Gas, Gashol, Alcohol or Diesel, & Alternative Powered Bicycles
....
there is a tiny sub section of the electric bike section for fuel powered bikes and conversions..
Gas, Gashol, Alcohol or Diesel, & Alternative Powered Bicycles
....
this is bicycle mechanics is it not? I’m asking about gears and gearing. What forum would you like me to ask about that in?! If I ever have any questions about the workings of the motor on my bike. I’ll be sure to post it where you want it.
09-11-18, 01:40 PM
#15
Banned.
Thread Starter
Looking at those pics, it looks complicated, lol.
to the OP, what is it about the 10t/10t that interests you? That's essentially setting up a 1 to 1 ratio so any torque multiplication happens through your gears only. I would think if you were going through the trouble of something that looks this complicated you'd want more output from it.
to the OP, what is it about the 10t/10t that interests you? That's essentially setting up a 1 to 1 ratio so any torque multiplication happens through your gears only. I would think if you were going through the trouble of something that looks this complicated you'd want more output from it.
09-11-18, 01:42 PM
#16
Banned.
Thread Starter
By rough guesstimates looks like a 60:1 rpm reduction from motor shaft to bottom bracket axle. Since most of us have pedal cadences in the 30-110 rpm
range, that should give you some idea what the engine will do from idle to top rpm motor shaft. You can interpolate speeds by looking at the alfine internal
ratios multiplied by the ratio of the driving CW to the alfine hub cassette gear. If you take the final ratios and multiply them by the actual tire diameter in
inches you will end up with "gear inches". A long time ago I figured out that 100rpm cadence in a 100 gear inch would result in a speed of 30 mph.
How that will work out with your alteration, depends on the motor shaft torque.
range, that should give you some idea what the engine will do from idle to top rpm motor shaft. You can interpolate speeds by looking at the alfine internal
ratios multiplied by the ratio of the driving CW to the alfine hub cassette gear. If you take the final ratios and multiply them by the actual tire diameter in
inches you will end up with "gear inches". A long time ago I figured out that 100rpm cadence in a 100 gear inch would result in a speed of 30 mph.
How that will work out with your alteration, depends on the motor shaft torque.
09-11-18, 03:42 PM
#17
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i understand that some people don’t like any yellow flowers in theyer perfect patch of whites ones lmao
this is bicycle mechanics is it not? I’m asking about gears and gearing. What forum would you like me to ask about that in?! If I ever have any questions about the workings of the motor on my bike. I’ll be sure to post it where you want it.
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Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)
Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)
09-11-18, 04:00 PM
#18
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09-11-18, 06:30 PM
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well with my theory of a 1x1 ratio there. Feel like the 9 tooth would be too small and the chain may come of maybe frequently. So I believe the 10 tooth sprockets will be slightly less likely to come off. I understand how the gearing works on a traditional two gear bicycle but this jackshaft system has four gears technically 5. The two that I showed in the pictures two more where the chain ring is and the rear cog. If you had a bike that was a simple ss and then you added 8 gears to the rear. Would prefer to uses a smaller or larger chainring? Just curious
The setup you have seems overly complicated. You have more than 5 "gears" in the whole system. 7 by my count, using your method and not including the crabkshaft. From the crankshaft to the first "gear" (large pulley). The large pulley drives the second "gear" which appears to be sized as the crankshaft. From the second to the third "gear", which appears double the size. The third drives the fourth "gear" which again appears similarly sized as the second "gear". From the fourth to the fifth "gear" (outer chainring on the crankarms). The fifth drives the sixth "gear" (inner chainring). Finally from the sixth to the seventh "gear" on the rear wheel.
Not sure why he's stepping it up and down, nor why there needs to be so many steps in the first place. Horribly inefficient system atop a horribly inefficent two-stroke gas engine.
As for the chainring question, if given the exact same gearing, you get the most efficiency with the larger tooth count in front. But with that setup, more losses seems to be a moot point.
I would've preferred the chopper with an electric kit.
09-11-18, 07:45 PM
#21
Banned.
Thread Starter
Yea it’s 7 I was not including the drive and clutch. Anyhow this ish is over complicated lol it is. I honestly feel bad for the young kid I got if from. I got the vibe of not much mechanical experience and went to gas bike dot com and made himself one hell of a gift 🎁 A couple years back. Idk if it came pre assembled for him but from what I’ve learned that this motor a pain to install. So so many bolts are different and there’s no instructions. The cool frame he chose is frame a different company. So very few holes align lol and the location of the petcock is against the air filter cover. They pretty much are in constant contact. So I cut a relief in the air filter cover. He opted of the cool rear billet sprocket adapter which meant the coaster brake arm has to be modified aka bent to work with the adapter. I rode it home like 20 plus miles with the choke on bc that’s the only way it ran lol I got homeband noticed the coaster brake arm was twisted. I fabbed a new coaster brake arm to replace the twisted one. It twisted the same way. One the first ride. Have a twisted coaster brake arm could affect the wheels alignment lol yea sooo
09-11-18, 08:37 PM
#22
Banned.
Thread Starter
Took a break, so rear billet sprocket adapter, avoid at all cost. Want to have gears on your gas bike, want to have only one chain going to your rear wheel? Sure you’ll need a jack shaft system. Multiple gears on a frame that was not designed for it. I needed
a inter geared hub. Center lock disc brakes over coaster brakes sure why not.
a inter geared hub. Center lock disc brakes over coaster brakes sure why not.
09-11-18, 09:41 PM
#23
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