In flight belt failure...

[Al Austria]

Well, it was my second flight of the day and I saw my belt SHOOT out of the back of my boom about 20 feet up during some pirouetting tic-tocs.

Here's a pic of the belt:

And here's a pic of the aftermath...



Can't say much about the save other than the fact that after touching down, I literally yelled "YEEAAA!" while shaking my fist and my transmitter above my head. The heli sustained absolutely NO damage whatsoever. The heli-gods were extremely generous today.

This was the machine's 31st flight. I'd like to believe that the belt was tensioned perfectly, not to tight but also not too loose. I've heard of a couple other cases of the belt breaking in flight. Not sure what to think of it yet.

Comments are appreciated.

[flag8r77]

Great job on the landing...yeah, this is the 2nd I've seen on the belt snapping. I'm no expert on this subject, but main concern would be did it break from 1) rubbing on the main pulley somehow or 2) belt is just poor construction. Either way it's certainly something that needs to be addressed.

[bmlasater]

fwiw...

Man... Can you fly!

Nice save!
Curiious...Have you/did you lube the belt with anything?...We've got a runnning debate as to lube/notlube the belt....Reason I ask is that I've got a couple 450 belts that have gone through a few helis...Still work fine...Always lubed every 2-3 months with silicone spray....Buddy has a belt 600N, been using the same stuff for about 8 Mo...Lotso flights...550 belt looks to be same construction as the Align....


John.

[ckoelliker]

Mine shot out of the back the exact same way. Unfortunately I do not have Al's skills, mine hit a bit harder. It was on flight 45. I thought I had my belt tension set ok as well. I have about twenty flights after my rebuild and all is well, I do not know if I had it too loose, and the belt skipped, hung up where they cross in the middle of the boom, or if it somehow jumped the pulley. The way it shot out of the back makes me think that it had to have broke somewhere at or after the rear pulley but before the front gear. If it broke at the front gear I do not think it would have shot 30 ft. straight up. Either way, I am glad you saved it.

[Charley Stephens]

Good Save Al

We have the new Pulley made I await a test sample then they go into full swing also we are looking into another belt someone sent me this link Ifigured I would pass it on as we are not alone when it come to belts breaking.

http://helifreak.com/showthread.php?t=121021&page=2

I really think its the power and the aggressive fights we put them through but one never knows......

I will do what I can to Get the best thing I can for you all.

[Al Austria]

Hey Justin, I assembled the idler pulleys so that the the drive pulley did not rub on the belt, but that may not be the case in flight.

John, I did not lube the belt as I wanted to see if it was up to the job as it comes. On the other hand, I do lube my Align 450 belt's with silicone(R/C car shock oil) and it does increase their life dramatically. After this, I'm considering doing the same with the 550's belt.

I for one would like to see a kevlar reinforced belt.

[Al Austria]

ckoelliker, thanks man. After all that, I still cannot believe the only thing I need to replace is the belt.

That's good to hear Charley, a new pulley can only help.

Posts like those remind me why I prefer torque tubes over belts. Albeit, TT's are more complicated and require 2 more gear boxes, but if you build them properly they seem less likely to just fail outright.

[bmlasater]

fwiw..

Al, I'm curious to see what you think after the belt lube...We've been messing with the belt lube thing for quite a while, and all our evidence points to the lube extending the life of all the belts we've tried, and minimizing eliminating the mechanical issues common to belt t/r systems...I'm going back to the belt on my 600 N as soon as I lose my last tt setup...I've got the tt setup solely because I'm an auto nut, but trading helis with my buddy who has a belt 600N, I certanly cannot see that I have any noticeable advantage with the TT...Both helis are identical save the t/r drives...

John.

[Jason_Adamo]

I had 1mm washers under the guides but took them out because it was causing the belt to ride up on the front pulley.

[damyxz]

Hey, how about a chain drive?(just kidding) I soaked the tail belt in silicone oil with PTFE ( stuff we use to lube our tournament paintball guns)overnight before the build and so far no problems. The rubber compound on the stock belt seems to be soft. and the reinforcement fiber seems to anly be one layer(some of my other helis have 2 or more layers) A better quality belt will help a lot. Also There are some sharp flashing on the edge of the front pulley, I placed mine on a mandrel and spun it on a cordless drill while running the edge of an X-acto knife on the rim.(rimjob) Then I pass a 400 grit sand papar along the inner border of the upper and lower rim of the front pulley. The flashing will nip at the belt edge continuously as it spins, if this happen at around 2100 RPM, it is like taking a fine toothhed saw at the edge of the belt coupled with the tension on the blt during flight, this leads to belt failure.

[damyxz]

Mr Charley...just a thought is it possible for you guys to come out with a slightly longer boom? I think this mod will help alleviate stress on the tail belt by making easier for the tail to counteract mainblade torque by giving it a bigger mechanical advantage(leverage). A slightly longer boom(about 2 inches) also can improve tracking during FFF. Just a thought.