Absolutely psycho idea I had.

[cloakedvillain]

Absolutely impractical but with a double reduction you could have a fixed 3 speed outputting into a fixed 3 speed and a tiny rear sprocket giving a wide range all to left side. (2.56 to 1) Can still bump start with pedals as it leaves the right side unchanged.
In operation one would have to manage two shifters though mountain bikers handle it fine.
Draw backs are cost, size, and increased complexity of operation and maintenance.

 

[Sidewinder Jerry]

Absolutely impractical but with a double reduction you could have a fixed 3 speed outputting into a fixed 3 speed and a tiny rear sprocket giving a wide range all to left side. (2.56 to 1) Can still bump start with pedals as it leaves the right side unchanged.
In operation one would have to manage two shifters though mountain bikers handle it fine.
Draw backs are cost, size, and increased complexity of operation and maintenance.

The SA S3X fixie gearing is 5/8, 3/4, 1/1. The regular 3 speed gearing is 3/4, 1/1, 4/3.

You'll end up with 2 redundant gearings. I've developed a sequential shifting system for you that'll give you 7 ratios.

 

[ImpulseRocket]

Draw backs are cost, size, and increased complexity of operation and maintenance.

Increased driveline power loss as well. The more sprockets, chains, and gears you have to drive, the less power output you have at the wheel.

 

[cloakedvillain]

The SA S3X fixie gearing is 5/8, 3/4, 1/1. The regular 3 speed gearing is 3/4, 1/1, 4/3.

You'll end up with 2 redundant gearings. I've developed a sequential shifting system for you that'll give you 7 ratios.View attachment 188810

I was thinking of keeping the gas and pedal drivetrains separate. Good point about the sequential shifting.

 

[Sidewinder Jerry]

I was thinking of keeping the gas and pedal drivetrains separate. Good point about the sequential shifting.

The gas and pedal drive trains are separate.

 

[cloakedvillain]

Increased driveline power loss as well. The more sprockets, chains, and gears you have to drive, the less power output you have at the wheel.

There's some experimentation to be done. I think ill stick with one fixed gear hub if I do go through with it.

 

[Sidewinder Jerry]

Been doing some gearing calculations. This system wouldn't be very feasible on a china girl 2-stroke. Even with the top gear (3)[3] being the equivalent of a 10\32, the lowest gears would be just way too low.

It could however work very well on a small 4-stroke, eliminating the need for a reduction box. A centrifugal clutch, sprockets, and chains would be all you'd need.

 

[Chainlube]

Gearbox eh?

 

[ImpulseRocket]

Been doing some gearing calculations. This system wouldn't be very feasible on a china girl 2-stroke. Even with the top gear (3)[3] being the equivalent of a 10\32, the lowest gears would be just way too low.

It could however work very well on a small 4-stroke, eliminating the need for a reduction box. A centrifugal clutch, sprockets, and chains would be all you'd need.

It would also depend a little bit on the initial sprocket combo between the engine and the first hub. The sprocket ratio could also be slightly over-driven between the first and second hub to correct some of it.

It would take a lot of math and a little experimentation to make ot work.

At the end of the day though, I came to my own conclusion when calculating sprocket combinations for a jackahaft setup that a 3 speed hub can cover the full range of appropriate sprockets for most scenarios.

I could have a setup that was geared close to a 56 tooth in first, 44 in second, and 36 in third if compared to a direct drive, and could be adjusted as needed to suit desires. For these little motors, that's just about perfect for most scenarios imho.

 

[Sidewinder Jerry]

It would also depend a little bit on the initial sprocket combo between the engine and the first hub. The sprocket ratio could also be slightly over-driven between the first and second hub to correct some of it.

It would take a lot of math and a little experimentation to make ot work.

At the end of the day though, I came to my own conclusion when calculating sprocket combinations for a jackahaft setup that a 3-speed hub can cover the full range of appropriate sprockets for most scenarios.

I could have a setup that was geared close to a 56 tooth in first, 44 in second, and 36 in third if compared to a direct drive, and could be adjusted as needed to suit desires. For these little motors, that's just about perfect for most scenarios imho.

Yes, much better to just use one 3-speed for a 2-stroke. For the 2 together I was able to come up with a reduction range in the mid-40s to around 17\1. Great for a 4-stroke without having to use a reduction box.