Need a planetary gearset for my auto 2-speed

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Tony01   10 W

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Need a planetary gearset for my auto 2-speed

Post by Tony01 » Nov 12 2015 3:07am

Hello, new member here and first post. Not an ebiker, but do have a 1980 Schwinn motorized bike powered by a 148cc Briggs & Stratton 3.5hp engine with a custom 2-speed automatic. Braking is Hayes Stroker 203mm hydraulic front and Sturmey Archer 70mm drum brake drilled to 72h to lace into a 48h pedicab rim.

Though I'm a gas biker, I do find that discussions here get very in-depth on many topics, and I find answers to many specific questions I have here.

I have developed a working 2-speed automatic transmission that shifts from freewheeling in 1st gear to non-freewheeling 2nd gear at around 25mph/4100rpm. It works on the same principle that RC cars shift; first gear is a freewheel and second gear is another centrifugal clutch that engages and overrides the freewheeling first gear. This setup works very well on my bike and it does take me up to almost 50mph, with a good cruise speed from 30-40mph (with engine braking). However, the transmission does have its problems: inefficiency of 3 chains (single speed with a similar ratio and only 2 chains took me to 55mph), wear due to reduced strength and new forces from having two jackshafts, and extra weight. The trans by itself weighs 20lbs, compared to 10lbs that my single speed setup weighed including jackshaft bearings and all. So I've resolved to make an automatic 2-speed using the same concept, but with planetary gears and only one jackshaft.. (maybe even go back to the belt primary which was just lovely!!) The problem is, I can't find any freaking planetary gears in the sizes I need.



I need planetary gears that are straight cut, with a Ring:Sun tooth ratio of 1.667:1 to 2:1.

SA s3x hub; 160%, can't find a place to buy the internals.
Xiongda 2-speed, 156% jump, but also cannot find parts.
Automotive gearsets, max jump 150% and all helical gears. Building around an auto gearset would mean designing with thrust bearings and such, and I don't wanna deal with that.

I've thought about going with a manual trans using a shiftable 3-speed hub, but unfortunately here in CA gas-powered MBs must be automatics.

Any suggestions?
Last edited by Tony01 on Jul 10 2018 3:47am, edited 1 time in total.
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Drunkskunk   100 GW

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Re: Need a planetary gearset for my auto 2-speed

Post by Drunkskunk » Nov 12 2015 10:37am

Nice bike! There are a few of us here who go over to the smokey side, and are members of Motoredbikes.com as well.

The 2 speed auto sounds cool. However, a variator would likely be lighter, easier to adapt, stronger, and more efficient. They are also belt based, so they should take the shock load of the Briggs' huge torque better than a chain and gears.
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Re: Need a planetary gearset for my auto 2-speed

Post by amberwolf » Nov 12 2015 2:52pm

Though you can make a "cush drive" mount for the initial gearing on there to take up the startup torque so it does essentially the same thing the belt would do in that regard, and take up the shock loads.

Tony01   10 W

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Re: Need a planetary gearset for my auto 2-speed

Post by Tony01 » Nov 12 2015 9:11pm

Drunkskunk wrote:Nice bike! There are a few of us here who go over to the smokey side, and are members of Motoredbikes.com as well.

The 2 speed auto sounds cool. However, a variator would likely be lighter, easier to adapt, stronger, and more efficient. They are also belt based, so they should take the shock load of the Briggs' huge torque better than a chain and gears.
Thank you. The torque shocks are not so much of a problem as with ebikes, I think. I've had a variator/cvt transmission on this bike, and while fun and smooth, it hogged enough power to where properly geared it would never exceed 35mph, and when geared tall would also not exceed 35 as it would never shift up. This engine is only a 3.5hp. The cvt is made for engines with power to spare. Unfortunately the friction forces from the driven spring force resisting the belt tension eat up at least 20% of power, if not more as the belt wears. If I had the 5hp briggs or a new 200cc OHV engine we probably would not be having this conversation! In ca 4hp is the max allowed and I'm probably there with my open exhaust. So efficiency and light weight are becoming a concern.

With a planetary geared 2-speed, my first gear would be geared and with its losses, but the top gear would mechanically be the same as a single speed with the jackshaft as most motorized bikes are built (even the 66/80 2-strokes are jackshafted; it's just part of the engine).

I need a source for planetary gears. The links miles posted above are a source, but not for the correct ratios (150% max). I've already sent a request for info/quote to one. Do you guys know of any place I can get SA hub internals, or xiongda hub internals? Or something similar?
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Re: Need a planetary gearset for my auto 2-speed

Post by Hillhater » Nov 13 2015 1:17am

Why not go back to the jack shaft reduction, but with a performance "slipper" clutch on the engine.
Race karts use that system for maximum low speed performance and high top speed.
Good slipper clutches are compact,dry disc based ,adjustable for slip, lock up rpm, and can handle the heat without failing.
Check out the race kart sites ( eg Comet) for suitable units.
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Tony01   10 W

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Re: Need a planetary gearset for my auto 2-speed

Post by Tony01 » Nov 13 2015 4:47am

Hillhater wrote:Why not go back to the jack shaft reduction, but with a performance "slipper" clutch on the engine.
Race karts use that system for maximum low speed performance and high top speed.
Good slipper clutches are compact,dry disc based ,adjustable for slip, lock up rpm, and can handle the heat without failing.
Check out the race kart sites ( eg Comet) for suitable units.
You're absolutely right; for tracks and flat land a slipper clutch is great. Not so much for hills. One road near me is 5.3mi long and climbs almost 2000ft; I did it in under 15min mostly in 1st. For riding the Santa Cruz mountains, having a low and a top gear is essential. It could all be done with one gear only, maybe, but then I'd be floating the valves on a regular basis every time I went downhill.
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Miles   100 GW

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Re: Need a planetary gearset for my auto 2-speed

Post by Miles » Nov 13 2015 5:34am

beginner01 wrote:I need a source for planetary gears. The links miles posted above are a source, but not for the correct ratios (150% max). I've already sent a request for info/quote to one.
Not sure I understand..... You realise the ratios in the Matex literature are for the standard planetary configuration (R/S + 1)? SA hubs etc. use solar configuration....

Ref: https://endless-sphere.com/forums/viewt ... 57#p951157

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Re: Need a planetary gearset for my auto 2-speed

Post by Tony01 » Nov 13 2015 8:00am

Miles wrote:
beginner01 wrote:I need a source for planetary gears. The links miles posted above are a source, but not for the correct ratios (150% max). I've already sent a request for info/quote to one.
Not sure I understand..... You realise the ratios in the Matex literature are for the standard planetary configuration (R/S + 1)? SA hubs etc. use solar configuration....

Ref: https://endless-sphere.com/forums/viewt ... 57#p951157
Yes. But sun input with planet output is not the only way to get a ratio out of a planetary gearbox. To get a ratio close to full lockup (direct drive) along with the same direction you must keep the sun gear stationary while using ring or carrier as input or output.

If you use ring as input, carrier as output with a gearbox listed as a 3:1, this translates to a r/s ratio of 2/1 which is a r/c ratio of 1.5 (reduction), or an equivalent .667 under drive. The SA s3x lists first gear as a .625 under drive, which is done by running the sprocket to the ring and hub shell to the planet carrier, with the sun gear the axle, and is equivalent to the 160% jump, or 2.667 reduction if it was labeled as a sun to planet gearbox.

So really, if you look at standard documentation, I'm looking for a 2.667 reduction but a 3 is ok too.
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Miles   100 GW

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Re: Need a planetary gearset for my auto 2-speed

Post by Miles » Nov 13 2015 8:18am

Ok. you understand.

3:1 (2:1 R/S) is the normal limit.

The Xiongda hub uses a differential ratio.

Maybe one of the bottom bracket hubs?

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Re: Need a planetary gearset for my auto 2-speed

Post by Tony01 » Nov 13 2015 6:18pm

Miles wrote:Ok. you understand.

3:1 (2:1 R/S) is the normal limit.

The Xiongda hub uses a differential ratio.

Maybe one of the bottom bracket hubs?
Good idea! I've just made an inquiry to a dealer of schlumpf bb drives. Maybe they can get the gears only for me. Would be nice as it is a very thin unit (though large diameter) and a good ratio.

So far I've come across this automotive gearbox, which would give me a 147% jump, but the thing that stops me is the helical gears which would introduce thrust loads... Meaning more bearings. I gotta draw this in solidworks getting too complicated :)
I don't always listen to Pantera.... but when I do, SO DO THE NEIGHBORS :D

Tony01   10 W

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Re: Need a planetary gearset for my auto 2-speed

Post by Tony01 » Nov 13 2015 8:34pm

Xiongda
https://www.electricbike.com/2-speed-e- ... /xiongda6/

From counting the teeth on that pic I get r-54, s-30, so my ratio would be (30+54)/54= 156%

Where can I get those parts? All I see is complete hubs.

SA got back to me with a list of distributors but no retail sellers. Weak. Seems nobody is interested in providing prototype parts... If this thing works I'd be willing to produce these units.. A complete 2-speed jackshaft for $150 or even $200 that looks clean and doesn't run two chains like the rupp minibike trans.. Nor cost $300...
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Miles   100 GW

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Re: Need a planetary gearset for my auto 2-speed

Post by Miles » Nov 14 2015 4:13am

I still think your best bet is to order the stock gears from HPC (my second link). I've built two epicyclic transmissions with gears from them. Good luck with building them for sale at $150 :)

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Re: Need a planetary gearset for my auto 2-speed

Post by silence » Nov 14 2015 6:06am

FSA Metropolis Patterson Transmission crankset as a (relatively) cheap source for gears and shifting mechanism?
https://endless-sphere.com/forums/viewt ... 4&p=824596
1.6 overdrive though.

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Re: Need a planetary gearset for my auto 2-speed

Post by Kulle » Nov 14 2015 5:10pm

Something like the SRAM-Automatics?

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Re: Need a planetary gearset for my auto 2-speed

Post by Hillhater » Nov 14 2015 7:17pm

beginner01 wrote:
You're absolutely right; for tracks and flat land a slipper clutch is great. Not so much for hills. One road near me is 5.3mi long and climbs almost 2000ft; I did it in under 15min mostly in 1st. For riding the Santa Cruz mountains, having a low and a top gear is essential. It could all be done with one gear only, maybe, but then I'd be floating the valves on a regular basis every time I went downhill.
? You power the motor down that hill ??...
Get stronger valve springs, and tune the motor to suit the speed range, set the gearing to match, then adjust the clutch lock up to suit the motor power band.
A 20 mph lock up speed sounds viable, but only you will know for certain what is possible.
PS. I often wished I could find a 2 speed sprocket hub for my karts !.....but the newer clutches solved most of those issues, even with 20+ hP available.
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