What gearbox? Turboshaft engine

[racket]

Maybe find a "dead" engine so that theres no need to make the other cover , just saw off whats not required .

[noshell]

Unfortunately i know very little about mopeds.
I would imagine some must have bearings on the pinion.
Im currently pondering how on earth i would connect that to my turbine wheel shaft. Maybe machine a collet that can connect the two... Im not sure

[richardm]

I would rather go for something flexible Shaft alignment is critical So if you dont have the equipment and experience ....

[noshell]

www.ebay.co.uk/itm/254773607647?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=mxcbe2s1Sba&sssrc=4429486&ssuid=0qSIhi1FTAO&var=554579726310&widget_ver=artemis&media=COPY
Perhaps this kind of coupling?
Im also pondering if plain bearings actually might work well for the pinion shaft if i have a high pressure oil feed tapped into them

[richardm]

Yes these could do the job" Be aware that they have a maximum allowance for misalignment and it might be more stringent that you think But its a good way to go.
But again I think you should first try to figure out the max rpm your turbine will be running at. It will help you in your quest for a gearbox as you will then know the required reduction ratio then looking at a suitable gear box.

[racket]

Plain bearings will work for the freepower , I used one in my bikes imgbb.com/c3g6PJD

Take Richards advice and determine your freepowers RPM potential first , its torque second , then think about gearboxes

[noshell]

Ill run a tacho next time i fire it up

[turbinenjoe]

Hello

I was thinking about using one of these planetary gear drives that are typically used for stepper motors.





The plan is to change the bearing on the input side to a ceramic bearing and to cool the gearbox with oil out of the lubrication circuit of the gas producer.

Best regards

Matthias

[richardm]

Could work.. Are the planetary gears mounted on bearings? What size is it ? ie what is the intended use of this gear box at what speed and torque. Ca you refer to manufacturer data about max speed and torque?

[noshell]

Ive had a quick look at a similar one. It says rated input speed is 3000rpm
But do these gearboxes typically step speed up?
I assume stepper motors are slow but high torque

[wannabebuilderuk]

These stepper motor planetary drives are step down and would probably work for a small generator turbine but would probably self destruct if used for high loads and high rpm

Unless you got one designed for a large motor like cdn11.bigcommerce.com/s-dvpzmvtuyz/images/stencil/1280x1280/products/727/531/133561159563-0__02445.1619667240.jpg?c=1

[richardm]

wannabebuilderuk is right. They're used to step down and therefore increase the stepper motor torque. Also a good unit would be built to tight tolerances to maintain movement accuracy . That could make em kind of "fragile" if operated out of specs.

[noshell]

Shame. 3000rpm is nowhere near enough. It will definitely need to tolerate tens of thousands of rpms.
So far the front runner in my mind is a scooter final drive, specifically a "GY6" gearbox. It would still be operating outside of its designed rpm window. It says the max power of the standard engine is 8000rpm. There are aftermarket gears available in a wide range of ratios.

Have a butchers at the gears. They look nice.
www.pedparts.co.uk/product/3956/primary-gear-kit--chinese-kymco-gy6-50cc-4t

Please note the nice large bearings. Im sure they could be upgraded.
youtu.be/56_aZ2j9ono?si=J3kmq1mMNLJrq-q2

I cant see why you couldnt run these much much faster than 8000rpm.

[turbinenjoe]

Hello 

the planetary gears run on needle bearings.



The rated torque on the „slow side“ of the gear box is 30 Nm (~ 22 lbf). I planned to use the gear box in reverse to its original application. With the gear ratio of 8 i get 3.75 Nm on the „fast side“. At 30.000 rpm this is already 16 hp which is plenty for my application. But it might not be the right one for higher loads.

Greetings

Matthias

[racket]

That looks good , I'd use them :-)

Scooter gearboxes are designed for plenty of shock loads