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Old Jan 28, 2015, 01:34 PM
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United States, GA, Loganville
Joined Jan 2015
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Belt drive or TT whats lower maint. ?

So is there a concensus on tail drives for reliability? I'm wanting to start a 550e clone build for a scale learner.
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Old Jan 28, 2015, 02:03 PM
WJH
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United States, FL, Spring Hill
Joined Aug 2005
593 Posts
I've only flown belt so far.. My blade 450 3d requires very little maintenance, checking to make sure the belt does not get a lot of slack. I've only heard of issues on the smaller heli's with TT. If that tail rotor knicks a blade of grass, it strips the gears. Some one else stated that if the tail blades are on loose, the blades will give a little instead of the gears stripping. My Chaos 600 is a TT heli, and I have yet to fly it, so can't comment on it.
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Old Jan 28, 2015, 02:14 PM
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USA, TX, Grapevine
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I prefer a torque tube. Low maintenance. You don't have to deal with belt tension or belt wear either. In some heli's large temperature swings can change the belt tension on you requiring some adjusting. Then there used to be static charge buildup with helis in the past that used belts. But I don't know if that is still the case today though.
With the 450 and up size heli's the drive gears on the torque tubes are not normally a problem in crashes etc. Now then the little Blade 130X had really fragile gears in their heli. A lot of people complained about them so it might be what people are referencing in some cases.
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Old Jan 28, 2015, 03:09 PM
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Aachen Germany
Joined Dec 2007
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Torque-tubes may seem more practical than a belt and they may be slightly more efficient than a belt - but if you just trying to learn and not ripping the sky - they are a really BAD choice. 3D flyers swear by them and think they are genius. Beginners swear at them and wish they never heard the name. There is good reason for all that swearing. The nylon gears on each end of the torque-tube will strip faster than you can say "throttle-hold". ANY kind of tail rotor strike - like learning how to hover and the tail rotor hits the ground - will cause the teeth on the gears to strip. And each time they strip you can kiss off $20 for a new set of gears AND at 1-2 hours of work to replace them. Make no mistake - they are a GIANT pain to replace. Trying to remove the bearings from the shafts of the umbrella gears is an exercise of frustration and without a wheel puller is like trying to remove frozen bolts with pliers - you wear out the pliers before those bearings will budge. Some say torque-tubes are genius. The only thing genius about torque-tubes is the marketing behind them. Replacement gears must be the top seller of all sellers combined. Align and the rest of the industry must of been dancing on the tables for that bit of marketing genius. The torque-tube gears for the Trex-550 are sold out faster than you can count to 550. No wonder buying a heli with a belt-driven tail is getting harder and harder to find.

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** Copied from CaptJac's Taking Off With RC Helicopters - FAQs 103 ** .. with the author's permission of course ..

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Old Jan 28, 2015, 03:31 PM
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The gears themselves are easy to replace but of course the ones that strip are the ones in the tail boom block, not the gears in the tail. That's what's the pain.
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Old Jan 28, 2015, 04:06 PM
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I have crashed one of my Gaui X3's several times and it hasn't hurt the torque tube or gears on it yet. Not to say it won't happen as I get more aggressive in flying it though.
So I don't see the problem with the gears, they aren't stripping out on me.
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Old Jan 28, 2015, 04:44 PM
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I think belt heli's need more looking at though, belt tension. My X5? Pin the boom and forget, ez mode. Thing is, it makes a godawful racket, in comparison to a protos, which has effectively no gear mesh at all.
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Old Jan 28, 2015, 04:57 PM
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Agree with what Captjack said. TT drives can be a bit fragile when you are learning because the gears strip very easily if you clip the tail rotor, especially so on smaller helis, bigger helis aren't so fragile.

Once i got past the stage of clipping the tail blades then I've not had any issues with either type. I thought belts would need adjusting regularly but so far the belt on my Compass 7HV hasn't needed touching since building it almost a year ago. The TT drive does spin with noticeably less resistance so it must be a bit more efficient.
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Old Jan 28, 2015, 07:04 PM
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Quote:
Originally Posted by CaptJac View Post
The nylon gears on each end of the torque-tube will strip faster than you can say "throttle-hold".
TT gears are made from acetyl or POM not nylon. It also depends on the design. Align's TT gears are undersized but some other manufacturer's aren't and are more resilient (albeit still not as durable as a belt).

Personally my favorite tail drive design is a direct drive belt with an auto tensioner. The belt is driven by a pulley on the mainshaft (there's no intermediate jackshaft between the auto rotation gear and the pully, the pully *is* the auto rotation gear) and there is tensioning arm with an idler pully so that the boom doesn't need to be adjusted.

Here's is an example of this type of tail drive:



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Old Jan 28, 2015, 09:48 PM
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I have both kinds (belts and torque tubes). Both work well, but I prefer the cog-belt (more durable and easier to repair).

As far as efficiency goes, the belt is just as good as the torque tube, with the exception that people tend to run belts far too tight. They try to keep the belt from slapping the inside of the boom and put a huge side-load on the bearings. In the old days, with flat belts (as in the Schluter HeliBaby or Amercian R/C Revolution) there were no teeth on the belt, which ran on knurled pulleys. Those had to run tight or they would slip.

Cog belts should be run as loose as possible without slipping.

The photographs shown above by Atomic Skull are of a Compass 6HV-U, which has a very efficient belt system. I actually trimmed the tensioner a bit to make it narrower (so that it would exert less force on the belt. It is not there to make the belt tight, but to keep the slack out of it when set properly. As he mentioned, it is very nice when dealing with temperature changes.
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Old Jan 28, 2015, 10:09 PM
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Denver, CO
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The Align 550 gears, often need the mesh adjusted. They strip out without crashing, if the gap between gears is too much. I like the torque tube drives, and would use them on any size helicopter. On the 550 size the belt works very well also. If you crash often get the belt.
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Old Jan 28, 2015, 10:19 PM
Need More PURPLE !!
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United States, NV, Las Vegas
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Soooo many debates on this subject. ha ......Belts are low maintenance And work just fine. . Also better for a heli if one should take a dirt nap . However, I still Prefer T.T. . I have always felt my Tails lock in better with T.T . . . True ? Probably not. . But I swear I have better tail authority on my Heli's with a t.t driven tail.
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Old Jan 28, 2015, 10:21 PM
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United States, GA, Loganville
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OK looks like the belt will do fine for a learner clone and when my kids are done draining me with college fees I will try a TT in a Align or higher level kit. I prefer to build so I know the design better for troubleshooting and repair.
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Old Jan 28, 2015, 11:30 PM
just gotta mess with it!
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North West Louisiana
Joined Nov 2009
5,366 Posts
Noise!

Many people make the mistake of believing the TT drive is more efficient than a belt, since when turning the main rotor by hand, there might be slightly less resistance. Under load, however, frictional losses increase for the TT gears, whereas the belt losses remain more constant, and the belt drive is probably more efficient when correctly adjusted. Direct-drive belt drives are unquestionably more efficient than any system that adds another tail drive shaft.

Personally, I detest the gear mesh noise from TT drives, especially on smaller helis. The Gaui X3 is quite possibly the worst offender in that respect, so it's no surprise to see they came up with a direct-drive belt tail conversion for it.

The one advantage I can see for TT drives is on larger helis, where it can make it much easier to remove the tail boom for travel.
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Old Jan 29, 2015, 02:12 AM
Grumpy old git.. Who me?
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Joined Mar 2006
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Quote:
Originally Posted by 2Doggs View Post
Many people make the mistake of believing the TT drive is more efficient than a belt, since when turning the main rotor by hand, there might be slightly less resistance. Under load, however, frictional losses increase for the TT gears, whereas the belt losses remain more constant, and the belt drive is probably more efficient when correctly adjusted. Direct-drive belt drives are unquestionably more efficient than any system that adds another tail drive shaft.
I've heard this before (that belts have less drag at higher speed) but as an mechanical engineer by profession it doesn't make any sense to me. I've also never heard a sensible explanation why it could be so or seen any test data to prove it... Basically i don't buy it.
Add to the fact that on my belt heli the rotors do indeed slow down from full speed noticeably faster than my TT helis (the belt is the Compass auto adjust as illustrated above) and no, the belt isn't too tight.
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