Tail Belt Problems

[growler]

Hi guys,

I know this has been covered many times before but I just can't seem to come right!

I've now had two crashes due to my tail belt snapping in flight. Now my heli is back together and I'm nervous as hell to take her up.

I have a 450SE. I noticed that with both broken belts, the teeth have not been missing, but have been broken on one side...almost flapping on the belt. Almost every one!

Now, on my fixed heli, when I spin the rotor by hand it is definately catching somewhere and locks up. This only happens when I spin by hand cause at a higher headspeed, it obviously just powers through the catching point which is causing the eventual breaking.

I've tried everything...looser belt...tighter belt...somewhere in between and still have the problem. I've also checked the gears on both ends and they seem fine.

Any advice would be great and much appreciated.


Regards


Neil

[busted blade]

assuming you have done the regular checks for burrs, vibration, too many twists in the belt , mis alignment,bent boom,proper tension, etc.. change both front and rear belt pulleys. there is no guarantee they where made correctly even if they look fine. also replace the tail shaft bearings. i have had them go bad and get pretty hot. this could be causing enough resistance to cause a problem. or just replace every thing from the tail drive Assembly back. 2 crashes + time to fix costs more than a whole tail Assembly. are the tail blades hitting the vertical stabilizer or the ground (grass)?

[ckoelliker]

I have received bad belt pulleys. Either out of round or they did not mesh correctly with the belt. But I have never broken a belt. I have removed some teeth, but never had one break.

[growler]

Thanks for the advice and if I don't come right will have to start replacing.

Do you think it's possible that the belt is catching on itself as it crosses over in the boom?

The boom is straight and the belt isn't twisted too many times.

[cflight]

I take it you test the tension, so it crosses half the space between, so I don't think it's catching itself.
I would assume that it's riding off to the side on the tail pulley, on the same side the teeth are half missing. Can you rotate by hand again and watch the alignment, to see if it goes off track?

[growler]

It seems to track fine. Definately not riding up the pully cause it would be visible when it locks up.

The teeth are not broken on one side, but rather in one direction. So that when you run your finger along it, they all bend back like a hinge.

[growler]

Can anybody confirm that it is normal to hear the tail belt tinging against the inside of the tail boom when you spin the head by hand?

[HPSOV2]

Cant hear mine, doesn't sound right to me.

[cflight]

I too thought my belt was clicking in the boom, found it was the tail drive gears making the noise. This lock up has to be something significant, let us now how you make out. I would inspect the tail drive gears to look for an inconsistancy in mesh.

[Pinecone]

Do you lube the belt? That can help with the teeth coming out of the pulley with a click.

But it sounds like you need to change the pulleys.

Also are you running the stock idler pulley in teh tail case? That can cause problems. ome people remove them entirely, others run the MX400 pulley which has flanges. Seems the stock Align pulley allows the belt to ride off the side and catch.

[growler]

Haven't tried lubing the belt yet...still looking for the right lube.

I do have spare gears so will swap them both out tonight and see if it sorts the problem out.

Maybe I should remove the idler pully as everyone suggests.

Thanks guys. Will keep you all posted with my progress.

Neil

[growler]

I've now swapped out both gears and the problem still persists.

I'm convinced the teeth are catching on themselves in the boom...just sounds and feels like it. I tried tightening and loosening the belt but makes no difference.

Any suggestions?

[Pinecone]

Lube.

I use RC car shock oil. Pure silicone oil. A couple of bucks for like 4 ounces, probably a lifetime supply.

[ckoelliker]

Are you sure that your belt is not twisted? I had mine twisted one time on a rebuild and it acted the exact same way. Beyond that try to put a mark on your belt and spin the rotors. See if you can determine if it is happening at the same spot, or is just random. This might help isolate the problem. Also double check your pulley gears. One time I had a tooth from the belt break off in the tooth of the pulley. It lodged itself in there and made the grab on each revolution.

[growler]

Well I haven't found the problem.....but lubing the belt sure has sorted it out! I can't believe how free the whole system is now running.

I know the lube is only masking the problem but for now it feels good.


Neil

[Bastian1337]

Have you tried a different belt? Like the Neoprene one?

[growler]

No. I haven't managed to get hold of one yet. But definately trying.

[Funky]

I lost a bunch of teeth on previous belts. After removing the belt tension pulley I started lubing the belt and using the neoprene Gates belt from Tech-MP.com. Since then I haven't lost any more teeth. I've been running the same belt for a few months now through mutliple wrecks.

http://www.tech-mp.com/trex_450_parts.php

[digger60]

I just went though my 2nd belt on my trex 450 se new v2. The tension seems right, I lubed the belt and still end up losing teeth about about a couple dozen flights or so. Tail holds good, cannot see it binding anywhere and somehow I still keep losing teeth. I noticed this last belt because I started hearing a clicking noise while spinning up. After inspection I noiticed that I was missing teeth and also the belt is starting to fray.

I would not complain except they are a pain in the ars to replace. Is this a normal replacement part after a few dozen flights ? How long do the align belts usually last ?

Tom

[avexplorer]

Sounds like you have a bad twist in your belt i also had this happen and broke 2 belts in 20 flights, fixed the problem with 3rd belt and have close to 300 flights on it.