Torque Tube vs Belt drives

[jhamel]

When using a belt system, how does one decide if the tail needs to be grounded to avoid static buildup and discharge?

[Ah Clem]

"When using a belt system, how does one decide if the tail needs to be grounded to avoid static buildup and discharge?"

It is probably good practice to just do it on all sizes of machines, with the caveat that I have not experienced it on a 250, 300, or 450 myself.

I have had a friend who had static issues on a 360 sized machine, which grounding cured. Saturating the belt in silicon spray did not help in this case. I have the same helicopter (Warp 360), and fly at the same place as my friend-the belts on mine are sprayed with silicon and it does not have static issues.

People have different experiences with the same equipment.

I first experienced static on a first generation Trex 600E when I switched from the stock plastic pulleys to the metal (upgrade) ones. Grounding the boom to the motor mount cured this.

Grounding is very easy and inexpensive to do. It takes longer to describe how to do it than to actually do it.

[satsuma]

My TDR is Torque tube and my Diabolo is belt drive, can't tell any difference in how they fly and virtually no difference to how they sound, BOTH are well designed and built machines and i can't fault either systems when as well built as these two are.
I have ZERO preference to either belt or TT.

As for LARGE 1/4 scale HELI'S, torque tube every time, smaller 700 size and below scale stuff belt will do the job, but due to accessibility not ideal.
My opinions only, but i DO fly the big scale stuff also, and TT never given me issues if BUILT CORRECTLY, crucial when a TT can be 4 foot long.

[tbob1000]

In support of belts - I’m flying an e5 tt and 3 other helis with belts - two goblins (500 and 700 comp) and a logo 600. I didn’t buy the helis with tail system in mind but having flown both systems, I like the simplicity of the belt drive systems. TT setups have extra bearings to deal with and maintain and there can be gear mesh issues as well.

With belts, you have to find the sweet spot between too tight resulting in unacceptable drag and wear, and too loose leading to tail authority/crash issues. The good thing is that, generally, belt tension is easy to get a feel for and check and adjust at the field.

I haven’t looked but I’m sure it’s out there somewhere but it’s notable that matt’s new 516 is belt driven. I’d like to know the reason for that decision.

Another thing I’m not sure about that is important is which system creates more drag for the purpose of autos. I don’t know the answer to that but would like to know.

[ic-racer]

How about direct drive?

Seriously, I think there is room for manufacturers to improve both systems. For example, how about clutch systems on large TT helis. Or belt drive systems that can be assembled (ie belts looped around both pulleys) before inserting the assembly into the frame. Etc...

[Raptorapture]

Strange that the poll is closed. I think the mention of belt for beginners and TT for the experienced makes sense. However, I would change that slightly to crash rate. If infrequent crashes TT and if you crash like me belt!

The belt tensioner is a good way of reducing the amount of slap. I must say though I've enjoyed rebuilding the TT on the XXTREME.

Edit: I see this thread did go through two reincarnations

[timewerx]

Originally Posted by ic-racer

How about direct drive?

Do you mean having a separate, small direct drive motor for the tail rotor?


Not a bad idea actually. There are engineers experimenting on the concept with full-size helicopters! They claim it reduces the risk of LTE (loss of tail rotor effectiveness) because the tail rotor with its separate DD motor operates independently from the main rotor RPM. So even in low RPM conditions, the tail rotor remains effective.


The advantage is quite obvious with low RPM setups and less # of parts vulnerable to tail strike. Direct drive means no gear to strip. It had occurred to me to experiment with direct drive tail rotors in the past but I never got time for it.... The setup requires 2 ESC's obviously.... The DD tail motor would require a smaller ESC since the motor would also be smaller.


High torque DD motors with wide armature are hopefully becoming more common. Eventually, they can be used on the main rotors as well. Less parts, less weight, less noise, less friction. All good!

how about clutch systems on large TT helis. Or belt drive systems that can be assembled (ie belts looped around both pulleys) before inserting the assembly into the frame. Etc...

My experience with TT clutch is that they are tensioned just enough to avoid slipping in normal flight and prevent gear strip in tail strike. However, it doesn't always prevent a crash or allow normal flight after recovery from tail strike. Once the clutch slips, it doesn't always stop unless you are quick to react to set tail pitch to 0 degrees (more or less) using rudder control. And if you regain control, you need to land immediately to check or reset the clutch.

[Andreas correll]

Fast piro stop, will test the strengths of the teeth on the torque tube

[tony#1]

Originally Posted by curmudgeon

All of my bigger helicopters (550 to 700 size) are TT driven. I have no issues with them. My only experience with belt driven tail helicopters is with the economically priced Blade 450 3D and Blade 450X. Although the belt never gave me any obvious trouble, I disliked "guessing" the appropriate belt tension during rebuilds.

I cannot make a fair comparison between TT vs belt driven tails mainly because I have never tried or converted one type to the other on the same helicopter.

When I searched this subject of "TT vs belt drives", it seems that people stopped discussing this subject back in 2011, a time before the Goblin and other nice quality helicopters made a debut. These were the main points discussed:

1) TT more expensive to fix after crash, so belt wins.
2) TT strip easier if tail blades contact tall grass, so belt wins.
3) TT more precise for hard core 3D, so TT wins.
4) TT has less drag and is more efficient, so TT wins.
5) Belt releases static, so TT wins.

It almost seemed from those discussions that the TT was going to be used mostly for hard core 3D pilots, and the belt was going to be reserved for beginner pilots or the more economical helicopter kits.

However, the very popular and upscale Goblin's and Logo's are belt driven with no sign of switching to TT. Also, there are various threads of pilots trying to convert their TT helicopters into belt driven.

Now in 2013, what is the current thinking of TT vs belt drives?

I appreciate that the #1 posting was six years ago addressing 550 to 700 size helis but the original two bladed then the three bladed variants of the Blade 180CFX came with a torque tube but the latest Fusion 180 CFX has a belt driven tail. Is there any engineering reason for choosing one over the other or is it all sales driven?

[fastflyer20]

I would say design engineers preference. Both can be designed to work well. In small helis TT seem a bit more problematic after a crash.

[JimJW]

Originally Posted by tony#1

I appreciate that the #1 posting was six years ago addressing 550 to 700 size helis but the original two bladed then the three bladed variants of the Blade 180CFX came with a torque tube but the latest Fusion 180 CFX has a belt driven tail. Is there any engineering reason for choosing one over the other or is it all sales driven? [IMG class=inlineimg]https://www.helifreak.com/images/smilies/dontknow.gif[/IMG]

I haven’t been around long enough to own a torque tube bird, but I’d guess that the main reason TT have been disappearing is part count/complexity.

A belt drive has 3 parts and no added bearings. A TT drive has 2 extra bearings and the bevel gears, shaft, etc. & the bevel gears are relatively expensive compared to belt pulleys.

[MikelG]

The other aspect of it is that, designers have figured out how to make the belt work.

The biggest issue with old belts was the tension needed to prevent the belt from skipping. The problem was easily solved with bigger pulleys. More contact with the belt around the pulley allows you to run lower tensions and reduce the drag.

Compared to complexity, weight, parts count, price, etc. Belt wins out at this point.

[extrapilot]

Engineers didn’t just figure this out. I think you will find the concept of wheel diameter vs torque required was understood about 2000BC.

The problem was and is much more complicated. With helis, the primary driver is mass. Secondary is reliability. If you could save 10% of you machine mass by running a tail drive with a belt, but you had to swap belts every 10 flights- you would do it if you cared about performance; a 10% penalty means you could not be competitive in 3D contests, flight time decreases more than 10%, etc.

But mass comes as a complex problem of direct costs- the transmission, but also as things like the tail boom (not just its physical mass, but also the download/drag is sees in the rotor wake or in lateral flight etc). If you want a 1” diameter pulley on your 450’s tailcase- you are looking as problems with the case itself, but also the boom ID, unless you want to run idlers which force the belt to run closer. But you have higher windage losses- because the belt speed must be higher if the tensile load is lower for the same output power- so you have more drag there, and that costs power.

You will not find any full scale machines running belt drive tail rotors. Likewise, you will be hard pressed to find very small machines running torque tubes- mostly it is belts, or direct drive vs separate motor. So it is pretty simple to see that there is a range of upsides/downsides that sort of groups solutions by mass/power/cost, where micro is best suited to direct drive, small-ish (< 700) to belt drive, and then transitioning into torque tube all the way up to full scale.

There are manufacturers who select TT for 450s- and it is a stupid choice. But, they had their reasons. Maybe it is because they wanted to lower the mass and download in the boom tube. Maybe they actually generated more income by selling new gear sets for tail systems where you rip a tooth off hitting a blade of grass- until people simply stopped buying TT machines in factor of manufacturers who did belt systems in the same size format. Maybe they were just bad engineers- its not like DFC was an intelligent effort- they broke every common sense rule I was taught 1st semester engineering (who puts linkage in place that much not be permitted to teeter (to permit swash drive on a head that is allowed to teeter??)

There is a very simple rule which I think many people just ignore. If you don’t see something full scale- there is a reason. There are NO full scale machines running a DFC-type setup- even on machines with rigid heads. And it isn’t because the designers are stupid. Doesn’t mean the tradeoffs scale down- as stated, torque tubes arent as rugged for TR strikes. Full scale- you have a TR strike, you have a VERY expensive problem to address- and a new TT gear set is the least of that.

[MikelG]

To be clear, when I say figured out, I'm referring to the fact that now they're "properly" designed.

Prior to recent helicopters, many helicopters with tail belts had pulleys far too small for the performance we needed.

The principles behind pulleys is definitely not new.

[acrow]

Belts are much more fun.

Watching people bringing back their repaired belt-driven heli and wondering why the tail rotates in a different direction.

[extrapilot]

Or the ones who have 1.5 twists along the length- those make nice noises, and some smoke! lol

[K2Freak]

Been there, done that.

[MariaFan]

Originally Posted by extrapilot

Or the ones who have 1.5 twists along the length- those make nice noises, and some smoke! lol

Originally Posted by K2Freak

Been there, done that.

No... Never!!!

[K2Freak]

The backwards tail is easy to spot at least!

[MariaFan]

I did actually have smoke when I twisted the belt 1 1/2 times.