automatic 2 gear jackshaft

[curtisfox]

May have to put a clutch on a jack shaft to get the rpms changed with sprockets. Think that is what msrfan did.....Curt

 

[MotorBicycleRacing]

You want gears on a 50cc four stroke?
NuVinci hub.
Brian has been racing this Honda 50cc for years and has not blown up the NuVinci hub.
Socal Motor Bicycle Racing's next race is on sat Oct 27th.

 

[dmopedMA]

You want gears on a 50cc four stroke?
NuVinci hub.
Brian has been racing this Honda 50cc for years and has not blown up the NuVinci hub.
Socal Motor Bicycle Racing's next race is on sat Oct 27th.

Nice solution but not applicable, it's an OCC build so the only internal hub will be manual and manual shifting will make it ilegal un MA

 

[dmopedMA]

1200rpm is less than idle speed . . . . ... . . so how is that going to work?

It will be after the first reduction 4:1 on the shaft, that's why it must be low rpm

 

[Frankenstein]

You want gears on a 50cc four stroke?
NuVinci hub.
Brian has been racing this Honda 50cc for years and has not blown up the NuVinci hub.
Socal Motor Bicycle Racing's next race is on sat Oct 27th.

Happy to know this hub is a beast, I could tell full well from the moment I opened the box it was quite a special gem. Hardy engineering, they are making better ones directed towards the European electric bike revolution, I have a bad suspicion I'm going to go with an electric build that I could actually be very happy with and allows me to forgo any legal obligations associated with gasoline bikes in PA.. I really want to steer towards a really good bike but I'm having a hard time picturing a gasoline engine as the centerpiece of that. To be perfectly fair it doesn't matter where the power is coming from when you're riding a bicycle when it's 50 mph when you find the time to do it. It's also a bit less scarey without the extra vibration riddling through you and your bike.

Let's face it, bigger engines ride better in bigger frames, that extra mass takes a good part of the energy being dispensed in the form of Newtonian laws, the bike let's the suspension take some of the beating before letting the rest change the orientation of the bike as well, but I don't think I need suspension too much for normal road conditions.. The lighter bike frame is just more vibration prone, no real need to use a gas motor that is kind of hot and uncomfortablely large in a bike frame.

Electric is probably better suited for bicycle type frames all round so that's the delema for me right now.. Good news is work keeps me busy so I can afford to dump the gas for something a bit nicer...

 

[Frankenstein]

Nice solution but not applicable, it's an OCC build so the only internal hub will be manual and manual shifting will make it ilegal un MA

Use weaker springs, go-karters have multiple spring choices to fine tune their engagement speeds, so do many 'appliance motors' that are used to power snow blowers and minibikes, it's pretty normal to have those things available. What is the clutch you are planning to use?

 

[Deleted member 26224]

It will be after the first reduction 4:1 on the shaft, that's why it must be low rpm

Not gonna work. You need start with what motor rpm and speed you want to shift at, not what your primary reduction is going to be.

RPM is what causes the forces that such clutches work on. Higher rpm = stronger shifts and adjustability.

If you plan your ratios around the lowest possible clutch lockup, you'll end up with a bike that never shifts into high gear.

You need to get good at ms-xl or other software and make your own gear/shift calculator. I've uploaded a screenshot of the spreadsheet calculator I made for my builds.

Max torque lockup chart works for other people too. Lockup happens approx 1.3rpm later than engagement (output rpm).

If you notice all my primary reductions are no bigger than 10:16 or 1.6. This is because you need to keep rpms up to have the shift happen at a reasonable speed and rpm.

I didn't play with the numbers for you, but to keep a similar overall gear ratio whilst keeping rpms high in the primary and secondary, you'll end up needing approx a 10:1 final drive. Where are you going to find a 100t sprocket for the wheel?


This 2-speed setup has been done before... at least four times. Do something new!! if automatic is the only way to go then figure out how to shift an IGH with a computer. It'll be something you could sell in the future. Far as legality goes, your bike is already an automatic. If you do an IGH whatever gear it is in, it will start moving with the throttle.

 

[Frankenstein]

So what I'm seeing is the engine rpm doesn't drop when it shifts right? Or am I just confused.

Speaking of this automatic shifter, well nuvinci developed a shifter that can automatically shift up to match your best cadence, if you could somehow find out how to link a gas motor to that then the computer could do the shifting for you.

Not to mention you can shift it by hand as well. Not sure if your legislation says it cannot be shifted by the rider or if it just states it needs an automatic transmission, I've seen both, including both together in the same leg somewhere as loophole insurance. Either way if it only states it must have an automatic transmission then by total technical default you'd be clear. Best part is any officer can Google a nuvinci 360 automatic shifter kit and see that it is indeed an automatic transmission by definition.

 

[dmopedMA]

Use weaker springs, go-karters have multiple spring choices to fine tune their engagement speeds, so do many 'appliance motors' that are used to power snow blowers and minibikes, it's pretty normal to have those things available. What is the clutch you are planning to use?

Weaker springs is the solution, yes, maybe a Hilliard Extreme Duty Centrifugal Clutch with Red 1200 rpm engagement springs work.
https://www.mfgsupply.com/h5841.html
https://www.mfgsupply.com/hired.html

 

[dmopedMA]

Not gonna work. You need start with what motor rpm and speed you want to shift at, not what your primary reduction is going to be.

RPM is what causes the forces that such clutches work on. Higher rpm = stronger shifts and adjustability.

If you plan your ratios around the lowest possible clutch lockup, you'll end up with a bike that never shifts into high gear.

You need to get good at ms-xl or other software and make your own gear/shift calculator. I've uploaded a screenshot of the spreadsheet calculator I made for my builds.

Max torque lockup chart works for other people too. Lockup happens approx 1.3rpm later than engagement (output rpm).

If you notice all my primary reductions are no bigger than 10:16 or 1.6. This is because you need to keep rpms up to have the shift happen at a reasonable speed and rpm.

I didn't play with the numbers for you, but to keep a similar overall gear ratio whilst keeping rpms high in the primary and secondary, you'll end up needing approx a 10:1 final drive. Where are you going to find a 100t sprocket for the wheel?


This 2-speed setup has been done before... at least four times. Do something new!! if automatic is the only way to go then figure out how to shift an IGH with a computer. It'll be something you could sell in the future. Far as legality goes, your bike is already an automatic. If you do an IGH whatever gear it is in, it will start moving with the throttle.

Thank you for all the tips here.

I want to start after my first reduction because I don't want to build a full transmission box with two shafts, I love my 4G transmission and I would like to keep it and just adding 1 more shaft (the jackshaft), will add less power loss (bearing, chains, etc).

Let me give you some of the calculations I've being doing, having you telling me what can fail based on your experience is priceless:
HS motor has an engagement RPM of 3k and a max RPM of ~6.8k, so the output shaft of the 4G transmission will spin at ~750 RPM when main clutch engages and at ~1700 RPM at full throttle.
My idea is getting a clutch that engages at ~1200 RPM and install it on the output shaft of the 4G, based on your affirmation that lockup happens aprox 1.3 RPM later than engagement, it will lockup at ~1560 RPM. First speed will run from 750 to 1200 RPM, transition between 1200 and 1560 RPM and second speed from 1560 to 1700 RPM. Max torque is at 4500 RPM on the motor, 1125 RPM on the shaft.
Now talking about the two gears, the first one will be around 3:1 reduction and the second 2:1 reduction, still doing numbers bout this.
Talking about speeds, right now I do 29mph with a total reduction of 8:1 (40T sprocket), second speed has exactly that reduction ratio, so I expect the max speed to be a little bit lower, due to more chains and bearing, but will be a good test to see how much power is being lost on the jackshaft. First speed will be like having a 50T sprocket (9:1 reduction), I didn't try that sprocket, but I tried a 44T and it was quite quick.