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Home✈️Aircraft🚁Helicoptere-AlignOther › Maiden flight - success - except broken tail belt. No spares :/ No broken rex though.
07-23-2006 05:21 AM  14 years ago
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ormandj

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Kaneohe, Oahu - Hawaii

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Maiden flight - success - except broken tail belt. No spares :/ No broken rex though.
Well,

I finally got the Rex all setup. Never flown anything but a blade cp and a sim. Followed finless's videos, and got some help from this forum (thanks again!!)

Put it out in the yard, did a range test, all seemed ok. Checked all connections one more time just to be sure. All good.

Turned on the radio, made sure everything looked good. Check!

Plugged in the battery on the rex, got the tones, saw a solid light on the gyro, tucked in the battery connectors.

Stood far back, tested all cyclic, looked good.

Slowly upped the throttle. Whoa. This thing is FAST (13t pinion). Kept going up with the throttle, and suddenly, it's light on it's skids. Kept advancing throttle, and poof - liftoff! Cyclic worked! I could slide left and right. Tail was LOCKED SOLID. What a difference from my blade!!!

Went ahead and slid around a bit (didn't do anything but tail in) and went up and down. Seemed good except a few niggles I'll get to in a bit.

Did this a few times, landed a few times, disconnected everything. Battery was a bit warm, not bad, motor was pretty hot, esc too. I could keep my finger on the esc heatsink, but it was def. fairly warm. Motor I could keep my finger on for about 3-4 seconds, then it got unbearable. Keep in mind I'm running in normal mode, didn't adjust my throttle curve yet (0 25 50 75 100) but my pitch curve is adjusted to give -3 0 9 degree pitch.

Now as to the "niggles" I mentioned. The heli seemed to want to very slowly drift left. One touch of right trim seemed to sort it out pretty well, maybe I needed two touches of right trim (I think that's 8 right trim since my futaba 9chps seems to do 4 at a time.) Is there any way/reason this is occuring? My swash is absolutely level, I'm positive (used a swash leveller). Other than the slight drift, everything seemed in order.

On my fourth flight (I did about 30s-1 minute each flight), after letting motor/esc/battery cool, I slowly lifted off, and about 2 feet off the ground it started piroing out of control, figured it was the belt or something (and saw a little bit of black sticking out the rear) so I slowly lowered throttle and set it down. No damage (this would have destroyed my blade's landing gear, and made it tilt and destroyed the rotors, amazing how much more durable this heli is.) Unfortunately (and I'm really ticked) there are no hobby stores locally that carry the belt that are open, and none will be open tomorrow. So much for my weekend of flying.

I got the rex used, it wasn't a new belt, so it must have just been my luck it broke. I did check tension before flight, it was fine. I saw a thread come off the side, which I suspect was the reason the belt snapped.

Any tips on replacing the belt would be super helpful, I really don't want to have to take off the boom.

Also, any ideas on the left drift would be much appreciated. It might be totally normal, and trimming is the normal way to get rid of it - I just don't know.

All in all, a very successful first flight/build/setup, I'm VERY impressed with how rock solid this thing seems to fly. Can't wait to have it up and running again!

PS - Anybody on Oahu, Hawaii with a spare belt willing to sell to me, let me know!

Cheers,
David
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07-23-2006 05:22 AM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Following up, looking at the broken belt, there is fuzzy stuff on both sides in 2-3 inch lengths. Then it goes back to normal, then fuzzy stuff. I suspect that's the strengthener that broke which let the belt break. It's on both sides, in different spots. Is this just a really worn belt? Or is this something mechanically wrong? The tail boom was already attached when I got it, I didn't do that setup. It moved freely though (head would spin like 5-8 times with a good twist) and the belt tension was correct. I didn't check the belt for wear prior to flight though, I did notice a little bit of stringy stuff come out of the tail assembly during my build, but I didn't think anything of it (not knowing the belts).
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07-23-2006 05:35 AM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Thanks, I'll do that.
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07-23-2006 05:48 AM  14 years ago
Skiddz

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Carlsbad, CA

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One touch of right trim seemed to sort it out pretty well, maybe I needed two touches of right trim (I think that's 8 right trim since my futaba 9chps seems to do 4 at a time.) Is there any way/reason this is occuring? My swash is absolutely level, I'm positive (used a swash leveller). Other than the slight drift, everything seemed in order.
That left drifting tendency is normal. It's caused by the tailrotor thrust and it's called Translating Tendency. IMO it's OK to trim it out as you're learning to hover, but eventually you'll need to remove that trim and just correct it with some left cyclic when you're hovering so your forward (backwards, upside down etc..) flight isn't affected by that cyclic input. You'll also notice the heli doesn't hover level and it's due to the cyclic correction opposite the TR's thrust.

Congrats on the maiden.
A helicopter is 10,000 parts spinning rapidly around an oil leak.
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07-23-2006 05:57 AM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Ahh. Well, I didn't use trim the first two flights, it's easy enough to hold it steady with cyclic, I just thought maybe I screwed something up mechanically. :P I couldn't correct it just by giving right cyclic and letting go, I had to hold a little tiny bit of right cyclic constantly to keep it in hover. This is normal?
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07-23-2006 06:45 AM  14 years ago
koko76

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Nashua, N.H. USA

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The trim is normal, generally will need a touch or two of trim from a completely level swash. The trim in steps of 4 is a changeable thing in the 9C software. Specifically how I can't remember, but there is a setting to raise or lower that.
As to the tail belt without knowing what it's been through, it's difficult to say. The "threads" are the tension carying members in a timing belt. They are what actually bear the load, and depending on belt type, will be either fiberglass or kevlar (dunno if Trex belts vary, but in the industry there are several different fibers) . When these come out of the belt (a bad thing) and tangle in things like the pulley, they can cause the belt to snap.
There are many takes on the "belt dillema". Personally I treat mine with machine tool belt dressing, I've had over 100 flights on this belt with no problems, still looks good as new. No other mods were needed to mine.
Not knowing what the previous owner did, it's hard to say why this happenend now. You will most likely have to take apart the boom, and the tailcase to change the belt.
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07-23-2006 06:50 AM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Could this be why the belt broke? Just looked at my tail:

Overview:

In more detail:
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07-23-2006 07:06 AM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Look at the gear, on the left side. It looks like there's little notches. Is that normal? Grip isn't bent, I just didn't correct for lense distortion, didn't think it was necessary since that's not what I wanted to draw attention to. :P Gotta love barrel distortion at wide angles!
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07-23-2006 07:11 AM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Turns out those "notches" are just some kind of gunk. I looked at the belt teeth and they are a bit worn where that gunk is on the gear. Maybe that's just from when the belt broke. (That side of the belt is the most frayed)
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07-23-2006 07:18 AM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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When I spin the tail rotor, the gear seems to bob a little up and down on the right side. What could cause this? That's probably what pushed the belt to the left, and why there is the belt-gunk on the left, why the belt wore out on the left, and why the teeth on the belt are a bit jacked up on the left. :/ Grr, sucks to fix somebody else's doing. :P
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07-23-2006 11:45 AM  14 years ago
Jon the Rooster

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Johns Island, Charleston, SC

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By looking at your pict( my camera would Never get thet Clear! )you have some belt teeth stuck in the cracks of your pulley? That could cause your belt to snap!If I'm seeing that corectly.and one more thing "DON'T BE AFRAID!"
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07-23-2006 06:41 PM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Yep, those black marks are parts of belt teeth. I'm going to scrape them all out and see what happens. I think the belt was just on it's last legs, and poof, all gone. I need to give this whole thing a big cleanup anyways, this just gives me a good excuse.

Cheers,
David
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07-23-2006 10:13 PM  14 years ago
roboto65

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Conroe,TX

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I would use a toothpick or something nonmarring do not use an exacto blade you will mar it up then you will really go thru belts lololo or maybe a toothbrush....
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07-24-2006 08:32 PM  14 years ago
ormandj

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Kaneohe, Oahu - Hawaii

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Yeah, I'm gonna whip out an electric toothbrush I think (lazy...)

Thanks for the tips everyone!
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Home✈️Aircraft🚁Helicoptere-AlignOther › Maiden flight - success - except broken tail belt. No spares :/ No broken rex though.
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