Early A.C. Prerotator electric conversion?

[Gyro jeff]

have old heavy cable drive system worn out and heavy . gear reduction starter motor ?

 

[gyroplanes]

Sounds like a one off conversion. Air Commands used the Wunderlich prerotator exclusively for many years until The Texas Air Command bunch copied it and only bought some parts from Wunderlich Inc.
Starter motor prerotators usually have the starter mounted right to the rotorhead.

 

[Aerofoam]

It doesn't help now, but I am gong to make an E-rotator after a few other projects.
I have a lot of experience with brushless motors for RC and UAV's and there are some that are suitable.
I just need to do the new research to see who the current suppliers are, they change every few years....
I think a suitable solution can be made that has an all up weight around 5 to 8lbs.
Some of that depends on if a bendix is used, they aeem to all be heavy.
I have been playing with the concept of a cog belt drive and just leave it engaged, it can revert to an alternator
to recharge the starting battery during flight.
We have done this with brushless 3 phase motors coupled to a DA 100 engine with good results....

 

[Gyro jeff]

Sounds like a one off conversion. Air Commands used the Wunderlich prerotator exclusively for many years until The Texas Air Command bunch copied it and only bought some parts from Wunderlich Inc.
Starter motor prerotators usually have the starter mounted right to the rotorhead.

had 11 tooth drive of pmgr starter for chevy seem to mesh good . getting converted one way or another.

 

[Aerofoam]

had 11 tooth drive of pmgr starter for chevy seem to mesh good . getting converted one way or another.

The benefit of a brushless modern DC motor is that it will only weigh a couple pounds, can be controlled by a speed controller, so it can be gradually accelerated and the lithium battery will also only weigh a couple pounds.
The entire assembly will weigh less than an automotive starter and all the components together will probably be smaller than a starter...
They could also be lined up on the mast and fit behind the frontal area of the mast, so no additional drag...

 

[Doug Riley]

You prerotator innovators, please keep in mind: if your rig introduces significant friction to the rotor head (or God forbid, locks up tight), you will die.

A prerotator, therefore, should have multiple failsafe disengagement mechanisms. The classic Wunderlich blazed the way. It had three disengagement mechanisms in series:

Starting at the engine PTO and moving up, it had (1) the manual squeeze handle, spring-loaded to default to "disengage"; (2) an internal overrun ratchet, and (3) the Bendix, which also defaulted to "disengage."

I wouldn't leave any of the prerotator drive train connected in flight.

The electric starter-motor prerotators I've seen (and heard about) prespin the rotor to 125 RPM or so -- little more than half the speed of a Wunderlich. The really muscular ones -- RFD hydraulic and Monarch Metro-Launch -- approach 300 RPM.

 

[wolfy]

Let alone the horrid noise it would make all flight, straight cut gears are noisy with the bendix driving in the right direction but add the reliefs cut in a bendix gear and the noise from a bendix being driven is even worse.

wolfy

 

[Aerofoam]

I don't think anyone referenced leaving a gear drive engaged.....
A cog belt is silent and can be sized to fail if the motor locked up as well as have an emergency disengagement function.

 

[Vance]

I don't think anyone referenced leaving a gear drive engaged.....
A cog belt is silent and can be sized to fail if the motor locked up as well as have an emergency disengagement function.

If the belt is strong enough to accelerate the rotor it is probably strong enough to slow the rotor.

I have a friend who feels the cause of his gyroplane accident was the pre-rotator failing to disengage in flight.

I agree with Doug, multiple fail safes are the safest way to go.

That is why you split the needles in helicopters.

 

[Aerofoam]

A belt would be sized for slow acceleration, if the motor suddenly locked up, it would break.
These motors generally only fail electrically and that leaves them free wheeling.
A bearing failure could be slow, but I don't think it would have much effect on the rotor.
In addition, a cam, or lever mechanism could disengage it completely, this could be manual, or automatically activated by a tensioner, or both.

 

[Vance]

A belt would be sized for slow acceleration, if the motor suddenly locked up, it would break.
These motors generally only fail electrically and that leaves them free wheeling.
A bearing failure could be slow, but I don't think it would have much effect on the rotor.
In addition, a cam, or lever mechanism could disengage it completely, this could be manual, or automatically activated by a tensioner, or both.

If the belt is strong enough to accelerate the rotor it is probably strong enough to slow the rotor.

I have a friend who feels the cause of his gyroplane accident was the pre-rotator failing to disengage in flight and slowing the rotor.

In my opinion something that is carrying a man has different safety standards than a drone.

I have seen more than one electric motor fail in a way that it acted like a brake.

It appears to me that it doesn’t take much slowing of the rotor to cause a non recoverable event in any rotorcraft.

 

[Aerofoam]

You need to see one of these motors....