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e-HeliDirect HDX 300 - 450 - 500 - 600 > Help...My heli wobbles
 
 
design engnr
Heliman
Location: Lavergne, TN

Hello,
I have a HDX500sah:

Motor: stock 850 KV
Battery: 3s2p 4200mAh
Pinion: 26 tooth
Main gear: stock 94 tooth
ESC: Pentium 60 amp with UBEC
Cyclic: 3 x HS-85mg
Gyro: Rc-Tek G730
Rudder: Futaba S9257

I seem to be getting a wobble (the heli seems to be oscilating not vibrating). What could be the cause of this other than Low Headspeed? I know of another flyer using the same set-up power wise, and he seems to be doing fine. I am not into 3d yet, just sport flying and wanted to use my Trex packs for this heli as well. Hence the 3s2p. Any help would be much appreciated.

Thanks,
Dave

It's true! Practice does make perfect. I crash better than anyone I know!
04-21-2008 03:05 AM
 
 
Spitfire1
Senior Heliman
Location: Perth Australia

Could be slightly bent.
Main shaft, tail rotor shaft, anything that turns e.t.c, but I imagine you have already covered all these, any more info about as far as what you have isolated so far that it could be?? that way may think of something you have missed.

Even us oldies can Heli. Chris. Perth Australia
04-21-2008 04:18 AM
 
 
design engnr
Heliman
Location: Lavergne, TN

I haven't checked the shafts yet. But it is brand new. I will tear it down tonight and see what I can find.

Thanks,
Dave

It's true! Practice does make perfect. I crash better than anyone I know!
04-21-2008 12:28 PM
 
 
juneebear
Heliman
Location: Skokie, Illinois

Try checking if your rotor blades are well balance.

RC Heli for LIFE.
04-22-2008 03:18 PM
 
 
gorn
Elite Veteran
Location: Western Australia

The wobble is from low headspeed. I have worked on lots of these, and they all wobble at low HS. Looks like an oscilation, not a vibration. Easy test, bump up the headspeed. If it goes away then your done. If not, try a higher headspeed again. Other than that, search the usual suspects as others have mentioned.
All the HDX500's have very stiff head dampening. they are designed to run a high headspeed. When they turn to slow they wobble. Its not just the HDX either. Lots of other helis regardless of brand can have the same issue.
Hope this helps.

If you bling it, they will come :D
04-22-2008 03:22 PM
 
 
speeddemon370
Senior Heliman
Location: Spruce Grove, Alberta, Canada

Easiest way to check if the vibe is coming from your head or something else is to take the head off. Spool it up to wot. (strap it down or at least remove the tail blades) If the vibes gone balance the head and/or blades. Check the mainshaft to see if there is any deflection. Low frequency (low rpm) vibes are head/mainshaft oriented 99% of the time.

with 2 ears and 1 mouth you should listen twice as much as you talk
04-22-2008 05:41 PM
HOMEPAGE  
 
 
smcbmw
Veteran
Location: Louisville, Kentucky

I have the exact same motor/pinion/battery setup and I believe our throttle curves are about the same.. I have no wobble.... I have gotten new shafts that have ended up bent...

10-8
04-22-2008 07:52 PM
 
 
design engnr
Heliman
Location: Lavergne, TN

Checked main, spindle, and tail shafts and all appear to be straight. I fear my first assumption of too low headspead is a reality. I have been talking to smcbmw through pm's as we have the same power set-up, but not the same oscilation issue. Does anyone know if the se version has softer dampner? I can't imagine it would. 26 tooth is the largest pinion I can find. I am running a 90, 95, 100 curve from the midpoint up. So I am pretty well maxed out on headspeed. Could a faulty ESC not allow me to get full potential out of my motor? Keep the advice coming, I really want to stick with a 3S set-up if possible.

Thanks Guys,
Daves

It's true! Practice does make perfect. I crash better than anyone I know!
04-23-2008 02:19 AM
 
 
Spitfire1
Senior Heliman
Location: Perth Australia

maybe try a new set of blades, or an old set if you have any.

Even us oldies can Heli. Chris. Perth Australia
04-23-2008 09:32 AM
 
 
design engnr
Heliman
Location: Lavergne, TN

Tried a set of Hirobo Fiberglass that a friend flies frequently on his lepton and had the same results. I did balance my Main blades before the first flight, if I forgot to mention that. I havn't balanced the tail blades yet. I know they can cause vibration, but oscilation?

Dave

It's true! Practice does make perfect. I crash better than anyone I know!
04-23-2008 12:23 PM
 
 
gorn
Elite Veteran
Location: Western Australia

As I said, it IS the headspeed. I know your friend has a similar setup, but all the symptoms are from low HS.
Do a throttle curve of 0 50 100 100 100 and see what happens.
Its so simple to try!!

If you bling it, they will come :D
04-23-2008 01:12 PM
 
 
design engnr
Heliman
Location: Lavergne, TN

Gorn,
My ESC is fried from a faulty E-flight harness, so my heli is down right now. If you will notice in my first post I was asking for reasons other than Low headspeed. I have a feeling you are right though, and may be looking toward a 1000KV Skorpion motor if I can't get the wobble to go away with curves or timing.

Dave

It's true! Practice does make perfect. I crash better than anyone I know!
04-24-2008 12:50 AM
 
 
gorn
Elite Veteran
Location: Western Australia

I saw what you initially asked. But after you had checked all shafts and tried different blades, well, its the headspeed lol.
I work for a hobby shop that distributes these kits Australia wide, so I know the symptoms you spoke of.
Could it be something else, not after you had checked other things, no.
3s is always going to spin the motor slower than 4s, and 4s under 75% throttle would always have a wobble.
So on 3s (which I have never seen done in person, we always recommend 4s as a start point) Im figuring that you would need to be running flat out for a no wobble flight.
Go here http://www.readyheli.com/Online_Hea...ulator_s/81.htm
Use the top calculator first, and you will see that your HS is only 2168rpm! Way way way too low.
That calculator is pretty accurate too, Ive used it a lot and cross checked it with a Tacho. Accurate enough as a guide anyway.
I really do hope you get your problem sorted out, and I hope that some of what Ive said will be helpful to you.
Good luck

If you bling it, they will come :D
04-24-2008 03:16 AM
 
 
gray
Senior Heliman
Location: Lowell , mass

main gear

Replace the main gear with a good quality one like cnc gears $17 dollar or so .The stock gears are out of round .Thats what fixed mine .Good luck
04-27-2008 03:38 AM
 
 
design engnr
Heliman
Location: Lavergne, TN

Thanks gray,
I will order one, and give it a shot I have a new ESC on the way. So hopefully I will be back in the air soon.

Dave

It's true! Practice does make perfect. I crash better than anyone I know!
04-27-2008 05:01 AM
 
 
gray
Senior Heliman
Location: Lowell , mass

I just remembered an other time i was helping a friend find a shake problem on his heli .After taking the head off the heli from the shaft up leaving the shaft on and running the motor ,we still had the shake .Then we loosened the tail boom and disengaged the tail belt , ran the motor and the shake was still there .We came to find out that the day before he had a stripped set screw on the pinion gear and could not remove it so he grounded the gear on a grinder .The gear came of but but we found in the proses he had bent the can of the motor .In this case it would be the heat sink part of it .If you spin the main gear by hand to make the motor turn , watch the can to see if it is out of round .Do not know if he fixed it latter or how but after we replaced the motor it was fine .
04-27-2008 07:32 AM
 
 
gray
Senior Heliman
Location: Lowell , mass

Usually If the head and tail are balanced correctly then the main cause of wobbles and shakes come from bent spindle and main shafts One time i ordered two main shafts ( sonix ) and had vibration problems with both .I took them to work and put them on a bridge port and both ware bent out of the bag .Did you have the problem from the beginning or there was a crash .If i crash and brake a blade i replace the spindle and main shaft with out even checking the old ones .
04-27-2008 03:08 PM
 
 
design engnr
Heliman
Location: Lavergne, TN

It had the wobble right form the start. I removed the shafts and rolled them on a glass plate, all appear to be true. I checked the motor, and it appears to be running true as well. I will check the main gear for wobble later today.

Thanks,
Dave

It's true! Practice does make perfect. I crash better than anyone I know!
04-27-2008 03:33 PM
 
 
Spitfire1
Senior Heliman
Location: Perth Australia

Attention Gorn!!

Hey if you dont get my pm, its Jason I fly with allan and the guys.
I bought Phils old hdx 500 a few weeks back, the yellow one thats been sitting there in takeoffandland a while now, Im just wondering if you can remember anything about the heli, I dont know what brand battery it has, its a 4s 3700 black coloured, also it would be handy to know if its the standard head set up on it as I like the way its flying and dont want to inadvertantly replace any of the parts with stuff that might make the cyclic get all slugish next time I crash it.

Even us oldies can Heli. Chris. Perth Australia
04-29-2008 07:52 AM
 
 
gorn
Elite Veteran
Location: Western Australia

PM'd you

If you bling it, they will come :D
04-29-2008 03:11 PM
 
 
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e-HeliDirect HDX 300 - 450 - 500 - 600 > Help...My heli wobbles
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