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[tonyH]

I'm well out of my comfort zone here but I'm contemplating a sort of Z Drive using a short belt to transfer the power at 1:1 from the line of the motor shaft to the line of the prop shaft which should(?) be parallel to each other and no further than 5cm apart.
It's probable that the system would run at around 100 watts from a brushless motor.
Has anyone any experience of using a belt drive at higher revs?
With hope and thanks in anticipation
Tony

[derekwarner]

Tony...again nothing like looking at the belt manufacturers data sheet....they will probably have a few questions or variables in providing your answer


power to be transmitted
proposed rpm
diameter of pulleys
center distance between pulleys ...etc


Derek

[tonyH]

Thanks Derek and I totally agree that that's the starting point but when the book says max 40,000 revs or 80 metres per second for, theoretically, an 8mm wide steel reinforced timing belt on 10mm diameter pulleys, one starts to consider the b****r factor of what safety factor should be built in and what happens in the real world with start-up torque etc!
I don't want to go down the road of destruction testing this early in the design stage
Cheers
Tony

[derekwarner]

Tony....


Are you considering an IC engine?..if not....the maximum drive speed [surface belt speed per unit of time] can be electronically controlled on startup


What profile belt are you considering XXL, XXXL?
With the power to be transmitted [0.1kW], is a steel reinforced belt required?


Polyurethane elastomer toothed belts with Kevlar reinforcement have a far higher surface speed rating together with comparable power transmission capability


Derek

[tonyH]

Hi Derek,

I'm waiting for a new copy of the HPC Gears catalogue. I've used them in the past for getting the revs down and the torque up(!) and the quality is very good.
What I'm aiming for is a variation on a Z-Drive (2 off) with brushless so start up can be more gentle but...

I've looked at the commercially available stuff but I refuse to fork out £300.00+ for an experiment so I'm going back to first principles

[JimG]

If you want to make startup more gentle then look for a speed controller which can be programmed for soft start. Used in electric helicopters where the the rotor blades need to start up slowly.
Jim

[tonyH]

Thanks Jim,
Can you programme the rate of power gain?
Tony

[JimG]

I don't think so but have had little experience of using soft start. Any ESC I have using it has the soft start switched off as it has not been needed.
Jim

[TomHugill]

Some empirical evidence for you, I ran the 2:1 belt drives on my challenger. When I changed it to brushless the pinion was doing 40krpm roughly and the shaft end 20k rpm. The belts disintegrated in fairly short order and I went to direct drive with lower kv motors.

[tonyH]

What were the belts Tom?

[TomHugill]

What were the belts Tom?

Graupner ones

[tonyH]

Cheers Tom,
15-20,000 will suit initial trials anyway and the belt is wired so should hold together better than the Graupner. I can then turn up the volume.