Protos exploding tail update??

[CatchmyCorsair]

Wow, that looks exactly like Woody's failure. Right near the pulley mount.

But I'm still not seeing how the belt slips off the pulley?? Case misalignment doesn't seem like it would be off enough to cause slipping.

[HighFreq]

That can happen if the belt is way loose, i don't think that is the reason of the failures some people are seeing, otherwise a cut like that could be seen even on broken parts. I still think 99% of tail case failures are due to mainshaft moving and letting the belt slip off.

As for the perfectly flat theory, remember the belt twists 90° degrees inside the boom and i doubt 89° or 91° would make any difference.

Corrado

[vicrc]

Wespen, I don't like the look of the metal tail pulley you have, it looks like the walls of it is not flat to keep the belt in between the sides. Instead it has an angle and its possible a loose belt can ride up the angle and resulting belt jamming in the tail. The belt will change tension depending on the motor pulling or the main rotors free spinning, this could be the case why were hearing tail exploding during power down or landing. For peeps having tail issues I would look at the belt tension before each flight.

No tail exploding, 100+ flights, 2 crashes and replaced half of my tail assembly from one of the crash. (v2 tail). I even flew a week with slightly bent spindle and I can hear a slight vibs(humm) but did not have any problems with heli or tail.

I bet tail exploding is usually the cause of the belt jamming inside the tail. Is it often to find a broken belt with tail exploding?

[Blades345]

I feel a little better now with all this info out there about why it might be happening. I will make sure when I get mine, I check over the belt tension, the main shaft to make sure it doesn't move and all the screws for any loose ones. I know I will love this heli and can't wait to see what it can do. This is the biggest electric heli I have had yet so i'm a little nervous.

[Woody2312]

Now it is sure!

I just looked at some pictures which were taken short prior my "exploding" tail. And......
On one picture the collar has already had about 2mm spacing to the mainframe. That means in my case: I totally agree with Corrados opinion.

That means for you: You think your collar is tight enough? You should rather check it!

Mario

[HighFreq]

Sometimes when people tighten the collar they pull on the main shaft and for some reason the main shaft gets jammed and it feels like it is all the way up but it isn't. Than during flight the frames moves a little and the mainshaft is free to move up and the belts comes off.

It might sound that the belt tensioning and assembly is difficult on the Protos but it really isn't, there are just a couple of spots to look carefully at and make sure everything is ok.

Could you please post the pic where you spotted the collar high or send it to me in email if you don't want to post it.


regards,

Corrado

[Woody2312]

here is a bad qualitiy picture (resized). But i think you can see the small gap. If you would have the full sized picture, you´ve got a pm.

Mario

[jgoodwin]

Originally Posted by HighFreq

That can happen if the belt is way loose, i don't think that is the reason of the failures some people are seeing, otherwise a cut like that could be seen even on broken parts. I still think 99% of tail case failures are due to mainshaft moving and letting the belt slip off.
...

Corrado

I have over 400 flights on my Protos now and I have had three tails explode. Two of them I remember vividly. Both of them were on or near the ground and all three of them were 100% because one blade grip broke. I wish I had a picture. Imagine one of the grips cracking off between the bearings and the two grip halves where the blade slides into. In this situation no wonder the V1 and V2 tail cases gave up for me. There is no way the case would handle that sort of mis-balancing. I also know that these tail grip failures were partly to do with me hitting the tail blades on the ground during some autos. I am looking forward to picking up my well priced Spring 2009 Update pack tomorrow that has the strengthened tail blade grips. Well done again MSH/Corrado.

I know some people have had their helis tail explode in the air and I can not say that all 99% are not from loose belts or main shaft shifting, but I have run my belts VERY loose a majority of the time (zzzzitttt! during hard moves kind of loose) and 100% of my tail failures have been from cracked tail blade grips.

Oh, one of my booms was dented on the tail end as shown in a previous post. With mine the blades were spinning even after the tail case exploded, but the belt was still in great shape. The belt pulled the remaining pulley and tail shaft into the rear of the exposed tail boom.

Our window cleaner found one blade and partial grip on the roof the the house that I lost when it failed once during a test hover.

Jay

[jetnc]

Thanks Corrado! Now I have some idea of what to check. That was all I was looking for. My damaged boom(s) also showed some signs of having the tail case pulled back into it. I flew it Sunday without problems using the V3 tailcase. And before I flew I checked that the belt was very tight, main collar was tight and I had no axial play on the shaft.

So basically on my harder than normal landings I feel that the belt probably jumped. I am pretty sure I have the correct washer on and that the main shaft it tight. I'm going to check my guides to make sure they don't have any play when I get home.

[rcmarty]

Ok .. seems like were getting somewhere.

Correction on my up/down mainshaft play. 1mm would be on the high side, i'm thinking .5 to .8mm of play.
On a side note , the maingear has a bit of up down (casting) and a slight bit out of round.

Corrado ... Could you elaborate on how the up/down play is causing (starting) the chain of events ?

Belt tension .. i can see how this would play into the situation. Too loose and i can see the belt coming off. My belt tension was set right i believe. I had some flights where i could hear it dinging. Now i'm alot tighter , still spools down nice , and i made sure to tension the motor side also , making a note to make them even on both sides.

I want to get this going again. I still have v2 parts in my parts stash of parts.

Martin

[HighFreq]

Basicly what happens is that if the belt comes off the main gear it get winded up on the main shftgtear and pulls hard on the case using the inertia of the main rotor.
This is not likely to happen if the mainshft is correctly assempled and the belt is not way way too loose.


All in all i think there has been 3 causes for the tail problems.

Cause 1 Hard landings on V1 and V2 tail case may fracture the box and break on next flight<-- Fixed with V3 tail case


Cause 2 Hard landings on V1 tail blade grips may fracture the blade grips and break on next flight<-- Fixed with V2 tail grips

Cause 3 Main shaft has play and belts comes off<-- Pay attention during assembly and check once in a while


Corrado

[rcboosted]

Although I really appreciate the improvements being made to the heli, I can no longer keep up with what's change and what hasn't. I've had a couple of harder landings and I grazed the grass on my tail blades once. My Protos flys fine(spun to 3000rpm once by accident too), but I'd still like to know what I have and what to expect.

Would it be beneficial to have pictures of each version of the tail grip, tail case etc (main blade grip) all together and changes highlighted?

example for main grips would be:
left side old 9mm grip, middle new 9mm grip, right side new 10mm grip
9mm root, 9mm root, new bearing lay out, 10mm root new ridges for rigidity.

[Caleb White]

Bottom line... these high performance little helis can deliver and handle abuse when designed and built properly, but if the builder/flier pushes the envelope or is neglectfull in setup bad things are bound to happen. Yes, some brands are more stout than others and cover neglect or require less maintainance... but there is a price for over-engineering as well!

Yesterday I decided to tear down for some maintainance myself. My belt (tail side) keeps loostening up every few flights after I got new 30C batteries (2800+ rpm). It pings a lot in the boom when doing piro/pitch pump moves. I think there might be deformed spots on the plastic boom block clamp around where the screws were tightened for so long, that when pulling the boom back to tighten, it wants to creep back to those spots from the massive amounts of torque and belt tension. I have to look at it more.

No tail failure for me yet. running V2 box and also KBDD blades. I was slightly nervous about these blades. Even though I trimmed 1/8" off them, they still have slightly more area than the stocks, are more rigid, and weigh 0.1g more. I noticed a tail vibe when the sun reflecting on my CF vert stab made it look blurry. My tail shaft pully does have a slight side to side wobble. I will go back to stock blades a while after tune up.

Other things I'm down for is to upgrade to my free steel shaft I never did yet, lol! Also, when turning my blades by hand I hear click-clacks from maybe pully bearings or one-way. I am going to look at that.

I can see the tail grips as being a weak spot, especially if there is bad vibes back there and/or hard landings, and/or after market blades, or too many bubbles in the wrong spot in the plastic, or improper bearing/screw seating when installing, etc.

I am happy to see the updates that give added safety factors and peace of mind. Corrodo is doing great hard work!

[vicrc]

I saw a Compass Atom tail holder let go today at 3000+ rpm. I have ran my Protos averaging 2850 rpm and peaking at 3120 rpm by accident for an entire flight. I wont do it again but it shows it can handle the load but for how long?

I had my Protos since mid Feb and guessing I have 250+ flights (not including the weekends). No part ever came lose in flight. Crashed ones with a lock out, and an esc thermal is all. I know some of you may have problems, but this heli has been nearly perfect with me. The motor got weak but changed it and have nearly 200 flight with the Z20.