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Old 04-03-2012, 04:00 PM   #1
icourier19
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Default Shaft or belt driven Tail?

Hi, I am fairly new to CP Helicopters. I have learnt the basic flying skills with a Honey bee CP3. The tail Motor has now stopped responding as it should,after a small accident, new boom and fin, nothing drastic, and the bird is fairly uncontrollable. I have to apply a large amount of right control? Is it the motor or the controller. I have tried all kinds of adjustments but still not very responsive. Thanks in advance for any advice. Ian.
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Old 04-03-2012, 05:14 PM   #2
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Ok, the low down on shafts and belts.

Both work just fine.

The belts are a bit more forgiving when your tail strikes the ground or grass gets tangled up in the blades. They also will work if there is a slight bend in the tail. (You really should replace the tail if it is bent, but I am just saying.) They can cause problems with static. But this does not happen to everyone and it is easily fixed by grounding the tail boom.

Shafts are supposed to have less friction and no static. They are easier damaged by striking the tail to the ground or getting grass tangled in the blade. But it is not as bad as some make it out to be, or at least it has not been for me.

Each is a hundred times better than a tail motor heli. Tail motors only work well or really tiny helis where the tail rotor is so small that it can speed up and slow down almost instantly because it has a low mass moment of inertia. This means the MSR and MCPX and the like work pretty good with them, but most just don't work well.

For your current heli, it sounds like the motor is wearing out. Tail motors can do that. It is just a brushed motor after all. (I am assuming, most like that are) I would try a new motor and start saving up for a Trex or the like.
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Old 04-03-2012, 05:47 PM   #3
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I just swapped the TT for a belt drive on my Rex-500. I changed umbrella gears three times in 10 flights. And it's always the front set for me which is much more aggravation because I had to undo all my servo and gyro wiring to get it out. Them days are gone. The slightest ground or grass contact with the tail will shear teeth off the umbrella gears. I've wiped out my Blade 400 twenty times and still run the original belt. Maybe when my skill level increases I'll think about going with the TT again, but really don't see a reason to.
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Old 04-03-2012, 05:56 PM   #4
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My preference is for belt driven tails (cog-belt).

I have been through flat belts, wire drives, torque tubes, tail motors, etc. in the last 36 years or so. A properly set up belt (again, cog-belt) is more forgiving and reliable than a shaft drive (either torque tube or wire drive) and just as efficient, if not more so.
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Old 04-03-2012, 06:12 PM   #5
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I think it really depends on how well the belt drive or torque tube are done.

Mikado has a very strong kevlar reinforced belt drive system that is pretty much a set it and forget it system, but you still will need a grounding strap.

But I've been told even a Mikado belt can snap and I've known a number of people who had a crash and one guy completely lost his heli over water because of a belt snapping.

Torque Tubes don't have the static issue or the snapping issue and "CAN" be a lot more reliable IF they are built right.

The TT in a TREX is just plastic on plastic gears and I've heard of people actually breaking TT teeth in flight. These people are doing smack 3D, but still this shouldn't happen.

The TT on my TDR is Stainless steel to delrin at every junction and it has no issues like this. There are other manufactures that are using helical stainless steel umbrellas etc..

So I would say that a TT can be a better system IF it is a high quality system, and it is more efficient if it is done correctly than a belt drive.

I converted my T550 from a TT to a belt drive and it has more drag now. Same heli same everyhing just different tail.
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Old 04-03-2012, 06:42 PM   #6
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Mathmatically it would be hard to have less friction in a belt because you have to bend the belt around and that bending and bending back generates heat and causes friction.

Gear friction will be impacted by the materials and the mesh.
Belt friction will vary by the tension on the belt being used. I think that there is typically a lot of deviation in belt tensions.

I think the best empirical test that I could come up with would be to take my 550E with belt drive and take a fully charged battery and run it up to a governed speed 5 times and see how long it takes to spin down, with the TX set with a straight pitch 0 degrees and ailerons and elevator zeroed out.

It might make sense to do a large number of runs with different belt tensions to see the deviation on drag that your belt tension causes.

Then do the same with a TT.
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Old 04-03-2012, 07:29 PM   #7
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TT all the way. Stop whacking your tail on the ground, it's not that hard.
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Old 04-03-2012, 07:56 PM   #8
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Quote:
Originally Posted by Ah Clem View Post
My preference is for belt driven tails (cog-belt).

I have been through flat belts, wire drives, torque tubes, tail motors, etc. in the last 36 years or so. A properly set up belt (again, cog-belt) is more forgiving and reliable than a shaft drive (either torque tube or wire drive) and just as efficient, if not more so.
Agreed.

When I was learning, I broke several Trex 600 tail gears with minor strikes.
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Old 04-03-2012, 08:07 PM   #9
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Quote:
Originally Posted by mkovalcson View Post
Mathmatically it would be hard to have less friction in a belt because you have to bend the belt around and that bending and bending back generates heat and causes friction.
Not at all true, a belt drive is more efficient in theory, gears are quite lossy, especially bevel gears (you can hear the losses) and the fact that for a TT drive you have at least 2 sets of bevel gears (Trex have another straight gear as well for no reason i can comprehend) where a belt has just 2 pulleys also helps.

The fact most belts (due to poor design usually) need to be run very tight offsets this to some extent, the overall picture is that there is no significant difference in efficiency.

Basically with belt vs TT you get to pick your problems, Poorly designed/manufactured TTs have vibrations, poorly designed belts have static issues (both can cause tail issues if crappy enough). But a well designed TT (see TDR) and a well designed belt drive (see Mikado or Compass, 7HV in particular) are just as good, though the belt is still likely to be a little quieter.

Personally I prefer belts, because in the 450 size (largest heli i have currently) the TT drives are not that great and can cause vibration issues, not to mention much more fiddle when you bend a boom.
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Old 04-04-2012, 02:04 AM   #10
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Ive had a few belt issues. But the way I tend to land- fast, hard autos, I dont give a f#$% if it bounces 3 feet, as long as it ends on the skids. Im sure im better off with belts.
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Old 04-04-2012, 02:49 AM   #11
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I prefer belts... but you can't always choose belts with your preferred heli brand. Both are just fine.. especially if you are experienced enough never to touch the tail in flight or are over the newbie crashing phase.
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Old 04-04-2012, 04:35 AM   #12
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Quote:
Originally Posted by desertstalker View Post
Not at all true, a belt drive is more efficient in theory, gears are quite lossy, especially bevel gears (you can hear the losses) and the fact that for a TT drive you have at least 2 sets of bevel gears (Trex have another straight gear as well for no reason i can comprehend) where a belt has just 2 pulleys also helps.

The fact most belts (due to poor design usually) need to be run very tight offsets this to some extent, the overall picture is that there is no significant difference in efficiency.

Basically with belt vs TT you get to pick your problems, Poorly designed/manufactured TTs have vibrations, poorly designed belts have static issues (both can cause tail issues if crappy enough). But a well designed TT (see TDR) and a well designed belt drive (see Mikado or Compass, 7HV in particular) are just as good, though the belt is still likely to be a little quieter.

Personally I prefer belts, because in the 450 size (largest heli i have currently) the TT drives are not that great and can cause vibration issues, not to mention much more fiddle when you bend a boom.
I the case of the T550, there is still an intermediate gear with a belt as well, so you still have auto-rotation gear to small gear and then belt. What you lose are two pairs of umbrellas.

More efficient TT's have a castle gear on the main shaft, and more efficient belt drives have the belt drive on the main shaft.

Most good belt drive systems have guide pulleys at least at the tail. My T550 doesn't have one of those. The guide pulley at the tail helps prevent skipping a tooth on the belt by keeping the belt sandwitched between the pulley and tail drive. During hard 3D manuevers this tooth skipping can happen.

The automatic belt tensioning systems that are used by the 7HV and Diabolo help make sure your belt isn't over tightened which will increase your drag, but they add an additional friction. Both have tail guide pulleys.

My Protos is a complete belt drive system and it has a HUGE amount of inefficiency because of it. It has 6 guide pulleys. One each side of the motor and one by the pinion, two by the tail box and one tail guide pulley by the tail drive.

The Protos spins down FAST because of this friction. I love this heli, but it's single belt drive is not remotely efficient compared to gears.

Gear friction is dictated by materials used. SS against delrin is relatively slippery expecially when using grease. Typical unlubricated plastic and nylon gears have more friction.

friction unlubricated, lubricated
SS / Delrin .17 .12
SS / Nylon .25 .15
Nylon/Nylon .35 .18

Delrin is also more self lubricating than nylon. Henseleit recommends using a good plastic grease on the gears. I'm using MolyKote EM-50L.

Back to your earlier comment, about efficiency. I will agree that in a well designed TT or belt drive system the efficiency difference is not significant and in some cases negligible.

That leaves you with static issues and belt breakage for the belt, vs higher crash costs for the TT.

I love the complete belt from motor to tail approach on my Protos because it significantly eliminates parts that fail in a crash. This heli is simplicity at its best! If the belt were to snap this heli is small enough and cheap enough that it is just not a big deal.

I also love the TT drive system on my TDR because it is very well executed. In a bird this size I don't want to deal with static or a potential belt break. Also with the SS and delrin, there is no question which side will give if need be, rather than just having both fail like I've had in my T550.

My T550 is right in the middle for size, but the implementation for both is medicre. I'm not really impressed with its TT or belt drive system, but I have a belt on it now because the Align TT system has really high vibrations and it's extremely noisy. I have been told that I should replace this belt on a regular basis to avoid having a belt failure. The lack of a tail guide pulley makes me keep the belt tension higher so I don't have a belt tooth skip, but that will stretch the belt and wear it out quicker.

Belts are also a maintenance issue. The new Goblin uses a belt drive off the motor to avoid stripping gears with powerful motors, this belt also helps cool the motor. However I understand it is recommended that it be replaced every 60 flights. Most people I've talked to recommend changing your tail belt with normal maintenance every year. Belts are pretty cheap, so there is not a lot of cost involved.
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Old 04-04-2012, 08:37 AM   #13
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Quote:
Originally Posted by mkovalcson View Post
Most people I've talked to recommend changing your tail belt with normal maintenance every year. Belts are pretty cheap, so there is not a lot of cost involved.
I would suggest changing the belt every 300-400 flights. Some people fly 100 flights per year.. some fly 100 flights per week! Belts should be lubricated with silicone every 50-100 flights. I spray into a cup first and then brush on using a small paint brush as I slowly rotate the main blades. It soaks in and will not attract dirt or dust.
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Old 04-04-2012, 08:45 AM   #14
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Quote:
Originally Posted by Slyster View Post
I would suggest changing the belt every 300-400 flights. Some people fly 100 flights per year.. some fly 100 flights per week! Belts should be lubricated with silicone every 50-100 flights. I spray into a cup first and then brush on using a small paint brush as I slowly rotate the main blades. It soaks in and will not attract dirt or dust.
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Old 04-04-2012, 09:16 AM   #15
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Every 300-400 flights is about right.

I cannot speak to the Goblin, but for Hirobo, TT, Align, Compass, Kyosho, EXI, etc., this is about right.

Belts, IMHO, are not a maintenance issue at all.


Good discussion!
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Old 04-04-2012, 09:18 AM   #16
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Seing that some larger helis are now comeing out with belts (GOBLIN 700 and others) I would say belts are the better way to go. I cant say anything for TT though. But i am sure TT is just as good. And striping the gears out is not really an issue if you dont hit your tail on the ground or grass. I allways land on a flat smooth surface and never hit my tail on the ground.
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Old 04-04-2012, 09:49 AM   #17
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Originally Posted by UHx1xHuey View Post
Seing that some larger helis are now comeing out with belts (GOBLIN 700 and others) I would say belts are the better way to go. I cant say anything for TT though. But i am sure TT is just as good. And striping the gears out is not really an issue if you dont hit your tail on the ground or grass. I allways land on a flat smooth surface and never hit my tail on the ground.
Synergy is coming out with a TT for their E6/E7. Hopefully it will be a high quality implementation.

The Rave 90 has a torque tube with optional Stainless Steel helical umbrellas.
The Raptor e720 which is also an expensive high quality heli has a TT done well with helical beveled tail gears

Once again, done right a TT is excellent. Done poorly, you are better off with a belt.

In the Trex 550 forum there were a few people who say that they stripped TT gears in flight and that with some manuevers it even happened frequently enough to really upset them. TT done cheaply.

It is harder and more expensive to build a TT heli that can handle really high speeds without generating lots of vibration.

The Goblin is a smack 3D heli that REQUIRES a very high head speed to fly well. They made a good move going with a belt driven tail. People are running some pretty high head/tail speeds on that heli.
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Old 04-04-2012, 10:10 AM   #18
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One works no better than the other and both auto the same....

TT gears will strip in a few flights if mesh is too tight or loose....
Belts will break if too tight or skip on the pully if too loose...
Chances of replacing a TT gear after a crash is 90%...
Chances of replacing a belt after a crash is 30%...

Ive never had issues with either but have replaced WAY more TT gears than belts..
For the belt I replaced maybe 3-4 belts and 2 tail shafts in 4+ years,don't even wanna think about the torque tubes,torque tube bearings and gears I replaced ...If Align made a belt setup for my Trex 700N,I would put it on in a heart beat but im OK with the TT setup on my 600E..
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Old 04-04-2012, 10:24 AM   #19
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I don't get how people strike their tail blades on the ground. On the Blade 450, the vertical fin is solid and tall enough that I don't see how this could happen. Are some vertical fins more flexible or shorter? I thought the point of the fin was to keep the tail blades from striking the ground...
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Old 04-04-2012, 10:33 AM   #20
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Quote:
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I don't get how people strike their tail blades on the ground.
On a stock Trex 600, it's easy...for a beginner, especially in grass.
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