Redrive or Main drive question

[skyguynca]

Can someone tell me the main reason not to use a chain redrive system? I have seen some psru that are chain and some small helicopters using a chain drive system. Is there a reason why it is not used more? Or why people don't use it?

Thanks

 

[automan1223]

not sure.

not sure.

I think I remember hearing that a chain drive was tried on a rotary engine but it tore it to pieces. I could be wrong though.

There is no reason other than noise and lubrication why you could not use a chain drive. I believe they would be quite noisy. Most rotorway helicopter owners give up on the chain drive to the main rotor because it is messy and noisy. However in an oil bath with a sound metal case around one the right chain might do the trick.

Jonathan

 

[PW_Plack]

Could it be a chain is heavier than a belt redrive of comparable capacity?

 

[Ga6riel]

a chain as a mechanism requires maintenance
it requires being adjusted for slack, and lubrication
as safe operation requires a guard, inspection is made more difficult
the saying, 'a chain is only as strong as the weakest link' definately applies here
ask any motorcyclist how often he/she has to adjust the chain

on the other side, tooth belt drives are easy to inspect, and are just replaced whenever damage is apparent, or its life is deemed done
belt drives absorb shock loads, chains dont do that as well
tooth belt drives have come a long way in 20 yrs
made popular by drag racers for driving GM superchargers
....and yes they throw/break belts on occasion, but HP is way more than anyone uses here, add to that ... I have never seen a GM supercharger driven by a chain....

 

[Mike Schallmann]

Chain Drives are used in a lot of transfer cases of four wheel drive vechiles also in the old Oldsmobile Tornado a chain drive was used to transfer power from the engine to the tranny. Chain Redrives have been made in the past -but they are heavy and noisey also they require a good lubrication system --the Belt drive is cheaper and easier to make and service--

 

[MaD Dog]

Chain Drive Problems

Chain Drive Problems

One of the biggest problems, and why chain can't be used on redrives is that
the speed per foot of chains is a factor in the amount of heat produced, and respectively, the life of the chain. On a Rotorway the chain drive portion has a relatively slow feet per minute speed because the sprockets are relatively large, compared to a higher feet per minute speed that would be produced by a very small sprocket driving another sprocket that is not much bigger. A chain can run at a fairly slow speed around a couple of larger sprockets and will have a fair amount of life expectancy. Also, a chain is limited to a certain size radius in the smaller diameter sprockets dependent on the size chain used. For horsepower ranges used for helicopters, even small ones such as Rotorway, you need to use a fairly large pitch sprocket (distance between the teeth of a sprocket) and a large pitch chain simply will not turn the approx. 180 degrees on a small diameter sprocket. About a 2 inch diameter sprocket will only engage about 5 or 6 teeth on a number 30 chain, so you are limited by diameters that the chain has to go around. Small chain, small diameter sprockets. Large chain, large diameter sprockets. The chain does not absorb torsional pulses well either. Belts, tooth or vee, are capable of absorbing some of the torsional pulses produced by all piston engines. Chains have limited usage, which is the key factor in their small amount of applications for high speed rotation.
Mike Driggers

 

[GyroRon]

Motorcycles with nearly 200 horsepower stock use chains to spin the rear wheel and I rarely hear of chain problems these days.

 

[Harry_S.]

Chain drives on ground vehicles are okay.

I wouldn't have a chain drive on a machine that was haulin' my butt around up in the sky.


Cheers

 

[GyroRon]

Chain drives on ground vehicles are okay.

I wouldn't have a chain drive on a machine that was haulin' my butt around up in the sky.


Cheers

And some folks would say the same thing about a helicopter whose tail rotor is powered by automotive fan belts....

Or a prop turned by a cog belt....

Or flying anthing that has a car engine for power....

Or anything that doesn't have at least two engines....

I could go on.....

 

[Aussie_Paul]

I must have stuffed up...

I must have stuffed up...

...I thought I posted on this the other day but I must have stuffed up somehow!!!

IMHO gears seem to be the most reliable. I don't like the belts due to quite a lot of crankshafts breaking. A broken crank usually gives no warning were as the gears will usually start to become noisy.

Aussie Paul.

 

[Harry_S.]

Ron...I stated my preference.

But, you can still go on if you wish.


cheers

 

[pbool]

One thought, the Wright brothers flew with chains.

 

[StanFoster]

Just the thought of chain links spinning from a crankshaft thats turning 5200 rpm gives me the willies... That cant be good.


Stan

 

[Ga6riel]

...I thought I posted on this the other day but I must have stuffed up somehow!!!

IMHO gears seem to be the most reliable. I don't like the belts due to quite a lot of crankshafts breaking. A broken crank usually gives no warning were as the gears will usually start to become noisy.

Aussie Paul.

I had not heard about that Paul, can you expand on that ?

 

[GyroRon]

How do you think the cam shaft goes round and round on a small block V-8?

Or the Camshafts on any high performance motorcycle, with engines that turn up to 15,000 rpm or greater?

 

[StanFoster]

Ron: They have constant lube.....the chain spinning outside at that rpm would need constant oiling...and that would be a constant mess...

I was so glad when I got my Harley....no more black racing stripes up Barbs back...


Stan

 

[REDHORSE556CES]

The last timing chain I saw din't look anything like a motorcycle chain. ...and don't some auto engines use timing belts nowdays?

Harley-Davidson uses the Sturgis belt drive. Seems to be a very stout belt.

"Notes on Chains & Sprockets"
https://www.gizmology.net/sprockets.htm

 

[Vance]

We have run a Harley Davidson XR 750 at Bonneville to about 8,500 rpm with a three row primary chain. We have spun small block chevys to 8,000 in sprint cars with hy-vo timing chains. I would think that the chain housing would be a little heavy for aviation, but no worse than a gear case.

Thank you, Vance

 

[Aussie_Paul]

How do you think the cam shaft goes round and round on a small block V-8?

Or the Camshafts on any high performance motorcycle, with engines that turn up to 15,000 rpm or greater?

Ok Ron, your turn to put your money where your mouth is!! You do the chain thingie so that we can learn

Aussie Paul.

 

[scottessex]

I saw an ultralight in a magazine that a guy used a Honda cbr 900 engine with a chain drive to the prop shaft, and he flew it in second gear.

It would appear that the dry belt and all is much lighter than a chain and oil bath chain case.

I think it all comes down to weight.