Variomatic gearbox for aircraft?

[planedriver]

Just thought i'd throw this one in for a bit of open discussion.

 

With the various types of reduction drives available today, I was wondering whether something like the Variomatic drive produced by the Dutch company DAF in the early sixties would have any place in the light sport aircraft arena?

 

Oweing to their simplicity, they proved extremely reliable, even under such duress as The East African Safari Rally's. In many instances they would cover hundreds of thousand miles with no problems or maintenance at all. They had the ability to smoothly change from forward drive, to going in reverse.

 

I think this was once called a Kopp gearbox, or something similar, and was infinately variable with drive belts running between tapered cones.

 

I believe in the old saying that "simplicity is the best basis for reliablity"

 

Could this idea be useful to apply a bit of reverse-thrust, to slow an aircraft down on short strips.

 

Looking forward to your comments.

 

"Breaker, Breaker", where are you Nev?

 

 

[facthunter]

The effect is usually achieved with variable pitch. Piston engines can operate over a small rpm range to adjust the speed of the plane but this is not the way to do it in cruise in all but the simpler types.. With variable pitch you can use a different set of RPM's and if you have a supercharger you use Manifold Pressure to get the Horsepower up so you end up with quite a bit of torque going into a coarse pitch prop . Bit like putting it into TOP gear and putting your foot down. This gives you high BMEP's and good efficiency and gives the engine a relatively easy time. Turbo props like the Allison in the Herc's and Electra's run the engine at the same speed from taxi through the entire horsepower range. The prop does all the work. Nev

 

 

[planedriver]

Where would we be without you Nev? Always love your responses.

 

It was just a thought.

 

I hope you have a wonderful Christmas mate, and don't forget to log on next next year, or there'll big big trouble.

 

Kindest Regards

 

Alan

 

 

[turboplanner]

Just thought i'd throw this one in for a bit of open discussion.With the various types of reduction drives available today, I was wondering whether something like the Variomatic drive produced by the Dutch company DAF in the early sixties would have any place in the light sport aircraft arena?

Oweing to their simplicity, they proved extremely reliable, even under such duress as The East African Safari Rally's. In many instances they would cover hundreds of thousand miles with no problems or maintenance at all. They had the ability to smoothly change from forward drive, to going in reverse.

 

I think this was once called a Kopp gearbox, or something similar, and was infinitely variable with drive belts running between tapered cones.

 

I believe in the old saying that "simplicity is the best basis for reliability"

 

Could this idea be useful to apply a bit of reverse-thrust, to slow an aircraft down on short strips.

 

Looking forward to your comments.

 

"Breaker, Breaker", where are you Nev?

I had the DAF belt system in a six wheel drive amphibian with a two cylinder Hirth engine.

 

It had two stick steering with a hand throttle.

 

If you pushed the steer levers forward the vehicle would start to roll at the high end of the gearing ratio.

 

If you partially opened the throttle the belt tension would pull the pulley sheaves apart and the belt would track a smaller diameter, so lower gearing

 

On wide open throttle the belt tension pulled the puley sheaves to maximum width and you had the lowest gearing ratio.

 

As the machine gathered speed and the engine had less demand a spring forced the pulley sheaves back together and the gearing got higher and higher, moving the vehicle faster and faster.

 

After a little learning, you could hold the engine at constant revs and the vehicle would start and accelerate with a seamless supply of constant torque.

 

I think it would work driving a coarse blade prop, and cost less than a CS.

 

However, the killer in an aircaft would be it's weight - about the same as a 500 cc engine.

 

 

[Guernsey]

My brother had a Daf 44 back in Guernsey years ago, a very interesting car to drive especially in reverse.

 

Alan.