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HelicopterMain Discussion › belt vs torque tube efficiency
09-14-2007 12:10 AM  10 years agoPost 1
skydude

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Gainesville, Florida, USA

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This months RC Heli article about slope soaring says that "Shaft-driven tails consume less power than belt-driven tails."

I was always under the impression that fast motorcycles used belt drive because it transmitted more power/was more efficient, and that shaft drive was used for smoothness on the cruisers.

Does anyone know what the real deal is?

PS That brunette babe in the High Voltage article sure looks like she knows her bberies, I mean batteries.

---

Watch out all you moles!!! (Vae, puto deus fio)

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09-14-2007 12:30 AM  10 years agoPost 2
Boidman (RIP)

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I don't know how to calculate any of this, but there are variables that may make a difference in choice.

Speed, for chains and belts, in feet per second. Diameter of the sprockets or pulleys in the system. Amount of torque being transmitted. Environment the system is being run in.

In the operating range of a motorcycle, I believe it is chain - belt - shaft.

My belief is that on these models, the shaft is also the most efficient.

Ima gonna wait for some number crunchers to flesh this out, it could be fun.

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09-14-2007 01:00 AM  10 years agoPost 3
wlfk

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uk

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There's a new company makes belt drives for bicycles. By using carbon-fiber in the belts, they claim 98% efficiency - rather than older values of 80% or suchlike.

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09-14-2007 01:45 AM  10 years agoPost 4
oldboldpilot

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Southern California

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I fly 50 sized helis that have belt-driven tails, and there is friction in the arrangement on my helis that definitely drags head speed down in autos.

On the other hand, I have a F3C heli (Hirobo EX-II) which is also belt-driven, and the design is so good that the rotors will spin literally for several minutes once the engine is shut down!

By the way, the belt speed is quite low. It will last a long, long time!

So belts done correctly are great - light weight, efficient, relatively inexpensive, and long-lived.

Helis are Man's Defiance of the Laws of Nature - OCHC

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09-14-2007 03:22 AM  10 years agoPost 5
4 stroke flyer

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Dowagiac,MI

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When you are talking about motorcycles. The belt or chain on highperformance bike is used one because when you put power to the back wheel the bike actually pulls down on the tire and suspension. When you use shaft the bike actually raises up taking presure off the tire.

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09-14-2007 12:28 PM  10 years agoPost 6
ChristianM

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Oslo, Norway

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The power loss in a belt drive depends on a number of factors. The following factors will increase the power loss from a belt drive:
  • Stiffer belt
  • Higher belt tension
  • Higher belt velocity
  • Smaller tail rotor pulleys
  • Mismatch between the pitch of the belt and pulley teeth (due to a stretched belt)
A properly designed and setup belt drive system is more efficient than a torque tube system. The problem in our heli application is that our tail rotor are geared to spin faster than the main rotor. This is typically done by using a large gear at the main shaft and a small at the tail rotor shaft. The results is that the belt has relatively high velocity and bends around a small gear which increases the drag. This is exactly the opposite from a motorcycle application. I have seen one micro heli design (I don't remember which) where they use a speed up gear in the tail rotor housing to reduce the velocity of the belt in order to reduce the drag.

Another example is the tail rotor system on Trex450 where the drag is highly dependent on the belt tension. The less tension you have the better until the belts starts to slip. So the bottom line is that the torque tube drive for tail rotor application is usually a bit more efficient than a belt drive system. However a well designed and setup belt system will be about the same in efficiency.

Christian

Burn fuel, be happy

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09-14-2007 02:42 PM  10 years agoPost 7
skydude

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Gainesville, Florida, USA

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Excellent input. Thanks guys.

Watch out all you moles!!! (Vae, puto deus fio)

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09-14-2007 03:22 PM  10 years agoPost 8
jschenck

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La Vista, NE.

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To go a bit further on the shaft driven motorcycle tangent - the shaft driven motorcycle has a nasty tendency to squat down a bit when you throttle down the engine, VERY bad when you are at the limits in a tight turn. Also interesting to have the bike kick you in the butt when you hit 2nd gear at WOT. Early '80's Yamaha XS1100 and XS750's are bikes where I've experienced this effect the strongest.
This is why some of the high performance drag bike Vmax's were (are?) converted to chain drive even though it's difficult because the transmission output spins the wrong way (counter-clockwise).

I understand that belts are more efficient than chain but to make a belt strong enough to put up with very high performance motorcycles makes them too wide to be practical on repli-racers and knee draggers.

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09-14-2007 07:30 PM  10 years agoPost 9
Topher

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Rochester, Michigan

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There are a lot of variables, but a gear driven system has a higher obtainable efficiency than a belt driven system. I believe a gear and shaft driven system is more effecient then a belt in our application however it is not used because of cost and durability. The Shogun V1 comes to mind.

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09-14-2007 08:43 PM  10 years agoPost 10
wlfk

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uk

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I don't know whether it's relevant to helis - bicycles use different scaled parts. But on bikes:

Chain = 90-98% efficiency
Belt = 70-80% efficiency (?98% for CF belts)
Dynamo driving a motor - 70% efficiency
Torque tube - 70-80% efficiency.

All figures very approximate and from memory.

I thought the advantage of a torque tube was as much about constant speed of the tail rotor as it was about efficiency.

K

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09-14-2007 09:10 PM  10 years agoPost 11
floop

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Southern, NJ

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belt drive and electric

has anyone recorded the power drain over time on an electric (many flight)? Over a period of time differences in flying could be eliminated. Maybe the tube would give better run time.

I might test. I have over 100 recorded charges now. I could start the next ones with a tube installed on my t-rex 600.

IT's what I do.

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09-15-2007 04:27 AM  10 years agoPost 12
bellecrank

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Canada

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I have found a BIG difference between belt drive tails and shaft drives.

My shaft driven Raven 50 with the constant tail drive autos as easily as my X-Cell 60's did.

On the other hand, non of my 50's that had belt drives could even come close., even with careful adjustment of the belt tensions for minimum drag.

The auto is a good test as any energy to drive the tail has to come from the kinetic energy in the rotating mainrotor.

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09-15-2007 04:39 AM  10 years agoPost 13
MrMel

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Gotland

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Measured by many on T-rex 600 E when TT came for it, including me with EagleTree loggers.

NO noticable difference in power usage.

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09-15-2007 04:54 AM  10 years agoPost 14
GimbalFan (RIP)

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Big Coppitt Key, FL

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NO noticable difference in power usage.
The differences may be slight, but saying NO noticable difference is going a bit to far, IMHO. Several top-shelf pros fly here in Vegas including the Szabo Bros, and their comments after flying identical birds (other than the tail drive) would tend to indicate that the differences in power loss are in fact noticeable, although admittedly possibly only by those who fly at that level.

While only the pros may be able to feel the difference in flight characteristics, flight durations of both nitro & electric should also tell a tale (pun intended).

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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09-15-2007 05:01 AM  10 years agoPost 15
Boidman (RIP)

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I'd take objective measurements over subjective evaluations, in situations such as being discussed.

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09-15-2007 05:05 AM  10 years agoPost 16
GimbalFan (RIP)

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Have you had an opportunity to compare belt vs t-tube with that logger, Boid?

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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09-15-2007 05:11 AM  10 years agoPost 17
Boidman (RIP)

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Nope, but MrMel has a track record that for my money surpasses any in-air eyeball and fingers evaluations done by anyone, regardless their flying skills.

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09-15-2007 05:13 AM  10 years agoPost 18
GimbalFan (RIP)

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Curious. Considering the lower cost of the design and repair of belt drives, this makes one wonder why anyone would use a torque tube at all if all other things really were equal.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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09-15-2007 05:24 AM  10 years agoPost 19
Boidman (RIP)

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I strongly suspect that even with the pros, there can be a moderate but significant difference between similar model preparations. I could imagine that if one prepared 5 each, belt and torque tubers, measured out the wazoo with laboratory instruments, for things like drag/friction, everywhere, to establish similaritude, that 10 pros flying one after the other would have strongly varying opinions about how one auto'd better than another, or that one felt much more 'crisp' during hard maneuvers, because it was more 'efficient."

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09-15-2007 05:35 AM  10 years agoPost 20
GimbalFan (RIP)

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Bear in mind that many RC pros worldwide have eye-hand-brain perceptions and sensitivities which rival that of brain surgeons and concert musicians, and when the things they notice are unaccompanied by any motive towards bias, one again wonders what they could be sensing that would make their remarks so unanimous.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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HelicopterMain Discussion › belt vs torque tube efficiency
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