Tail belt drive gear keeps stripping!!

[surfanarchist]

Hey all,
I've had two tail belt transmission gears strip on my Swift 16. The drive belt is stripping the teeth off the gear where the belt interfaces. I've not had any tail strikes nor can I find any binding in the tail or on the belt. I keep the belt pretty loose. Could that be my problem? Anyone else see this on their Swift 16s?

Thanks,

Wayne

[Rodney]

May sound stupid but make sure you only have one 90 turn in the belt.

[RAV50]

And be sure you are not running the belt too tight. It is amazing how loose one can run a toothed belt.

[surfanarchist]

Thanks, I'll check the belt for turns when I tear into it tonight. I have gotten about 4 flights since I replaced it last so I'm doubting extra turns in the belt but I agree that one should always look for the simple self induced faults first. I was thinking about running the belt tighter since I know it's plenty loose.

[philiusm]

Hi Wayne,

Now please bear in mind I'm new to helis so I'm no expert but I have a Swift 16 that was having belt problems.

I noticed that it was generating a lot of rubber dust from the belt and it finally stripped the drive teeth from the main gear end of the transmission system.

I replaced the belt and drive cog and when I reassembled the boom I put an extra tail rudder servo mount on the boom where it enters the main frame. This was to stop the tail boom gradually creeping in and slackening the belt.

What I found was that the extra servo mount is hard up against the first original servo mount and the belt tension is quite high.

But there is no more rubber dust being generated and the teeth on the main drive cog look fine. I have ony flown the heli for about 1.5 hours total but it's looking good so far. I'm not sure but I think it's quieter in flight.

Regards Phil M

[philiusm]

Hi Wayne,

Now please bear in mind I'm new to helis so I'm no expert but I have a Swift 16 that was having belt problems.

I noticed that it was generating a lot of rubber dust from the belt and it finally stripped the drive teeth from the main gear end of the transmission system.

I replaced the belt and drive cog and when I reassembled the boom I put an extra tail rudder servo mount on the boom where it enters the main frame. This was to stop the tail boom gradually creeping in and slackening the belt.

What I found was that the extra servo mount is hard up against the first original servo mount and the belt tension is quite high.

But there is no more rubber dust being generated and the teeth on the main drive cog look fine. I have ony flown the heli for about 1.5 hours total but it's looking good so far. I'm not sure but I think it's quieter in flight.

Regards Phil M

[Dennisu]

philiusm

You must have your linkages for the tail off centre or the servo mounted with the servo shaft and arm toward the rear of the chopper as I use the same setup as you and have room to adjust for belt tension without the clamp touching the actual servo mount.

[Dennisu]

philiusm

You must have your linkages for the tail off centre or the servo mounted with the servo shaft and arm toward the rear of the chopper as I use the same setup as you and have room to adjust for belt tension without the clamp touching the actual servo mount.

[philiusm]

Hi Dennis,

I've just gone and checked, the servo shaft and arm are towards the front of the heli and everything is dead centre. I'm using a 401 gyro and I've adjusted the limit so that the tail pitch stops just short of full throw in both directions. The servo arm is virtually dead centre.

Without the additional servo mount there is about 10mm of room between the servo mount and the main gearbox.

I have found that the boom gradually creeps inwards reducing the tension on the belt. It may be because I'm a pretty crappy pilot at the moment and I've had a few heavy landings.

Anyway I took someone's advice, who is an absolutely stunning pilot, and added another servo mount that sits up against the original mounts on one side and the gearbox on the other. It's stopped the creep problem dead although the belt is tighter than I had it before.

The heli flies pretty well and I can take my fingers of the sticks for a few seconds and it will just sit there in the hover.

However it's not as stable as my Trex 450SE V2. I was absolutely gobsmacked the first time I flew it. I was expecting it to be a little skittish like my Twister CP V2 wich is a real handful. It wasn't, it's just unbelievably smooth.

I think I need to drop the pitch and increase the headspeed on the Swift. It's currently running at about 1470rpm in the hover. The Trex sits at about 2270 and I think that's the main difference. I may also look at changing some of the linkages for the CNC versions on the Swift as the ones on the Trex are far smoother.

Regards

Phil M

[Dennisu]

philiusm

As I said I use exactly the same setup and there is enough room between the mount and the main gearbox for the clamp and still have space between the servo clamp and the mount. I am using a Hitec 425BB servo and maybe your servo shaft is closer to the middle of the servo than mine. Also your rotor RPM is way to low. With a head speed in the upper teens you will find it is rock solid and I can let go of the sticks for quite a few seconds without it starting to drift off.

[philiusm]

Thanks for that Dennis.

Have you any idea what head speed is safe for the stock wooden blades please?

Regards

Phil

[Coolice]

Hey,

1750 max I'd say for the stock woodies. At 200rpm the Swift is rock solid and nimble to do everything.

I did not see any mention of what power setup you are running, eg. motor & ESC combo? If I know this then I can comment on a good pinion to bring the head speed up a little.

I have not had any problems with the tail belt pulley, nor has Pete Roper or Adam Turner and so it is a mystery to me. Did you check the bearings in the plastic gear to make sure they are still servicable?
/

[philiusm]

Hi,

Setup is Flightpower 6s1p 4900mAh

Castle Ccreations Phoenix HV85

NeuMotor 1907/1.5Y

I think it's got a 11t tooth pinion.

The motor has oodles of power in reserve as I have set the maimum throttle to 80% and it hovers at 60%. It's good for a beginner like me. I'm getting durations of nearly 20 minutes, 4 five minute flights.

If you think the maximum speed for the stock woodies should be no more than 1750rpm, all I was going to do was back off the pitch and increase the throttle so at the hover I got a head speed of around 1600

Regards Phil M

[Dennisu]

philiusm

Try this setup and see what you think. I have mine set like my full scale ship that has a governor on the turbine so the rotor RPM is held steady throughout the pitch range. All I do on the Swift is set the throttle to the amount of head speed I want from 1/2 stick to full stick. i.e. I use 78% for all points on the throttle curve from curve point 3 to curve point 5. The pitch is 0 at half stick and whatever you want for max pitch at full stick. This way the RPM is constant like a governored powerplant and the only thing you are changing is the pitch. Operates exactly like the full scale ship.

[Coolice]

Hey Phil,

On my 6s Swift running a CC60 I run it in govenor mode and it runs very well, I would suggest try this out on your own model as it makes things so much easier.
Then tacho the head and if the head speed is still a little slow go up on the pinion tooth count, this will bring the head speed up a little.
The disadvantage to this is that you will sacrifice a little duration I think but the model will fly a lot better.
.

[philiusm]

Thanks to all,

I will try gov. mode.

Sorry for hijacking the thread.

Regards,

Phil M

[Coolice]

Hey,

Cool, keep us informed of how you get on.
.

[surfanarchist]

Thanks all,

I did check the bearings in the plastic gear, I also replaced the belt (though I don't see any problems with the one I removed so it's been moved to ready service spares), re-checked tension and flew the bird about 4 times. So far no problems. I don't have a spare servo mount but I'll keep an eye on tension and if the boom starts to creep in I'll try the method mentioned to cinch it up. Right now with the new belt tension is good with the boom all the way in but that will change.