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Old Jun 24, 2012, 03:47 PM
Crash and learn
United States, PA
Joined Dec 2011
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Originally Posted by jspcrepair View Post
"Out of Control Left Spin" problem.

I have tried all of the tests for Gyro and such and nothing seems to work.

The heli will begin to spin to the left and Full right trim and right stick only causes it to stop spinning but it will not turn to the right.

I am thinking it could be a bad tail motor because when it is cool and I first fly it, it works fine... after a few minutes, it begins to spin -- Expecially at full throttle.

The DH9104 seems to be the only one I have ever read about with the issue.

As I said... the gyro seems to be working fine and the tail motor works with the main unplugged
Check the battery with a voltmeter. Should be 8.40v fully charged and maybe 7.00v immediately after flight.

Not clear if gyro works or not. And tail motor should spin faster with throttle increase.

Tail motor problems are common to all helicopters with tail motors.

But this looks more like a battery with low capacity or not charging fully. Expect about 6 minutes or less flying time. The battery will recover somewhat after a few minutes (while the motors cool) and that may be the reason things work after a cool down.

Would not hurt to have an extra tail and tail motor.
Chopper Tail Unit for DH 9104-14 $5.51 shipped - easy to replace and no soldering
http://www.aliexpress.com/product-fm...olesalers.html
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Old Jun 24, 2012, 04:24 PM
Brakes? Who Needs Brakes?
United States, WV
Joined Jun 2012
36 Posts
Quote:
Originally Posted by Ribble View Post
Check the battery with a voltmeter. Should be 8.40v fully charged and maybe 7.00v immediately after flight.

Not clear if gyro works or not. And tail motor should spin faster with throttle increase.

Tail motor problems are common to all helicopters with tail motors.

But this looks more like a battery with low capacity or not charging fully. Expect about 6 minutes or less flying time. The battery will recover somewhat after a few minutes (while the motors cool) and that may be the reason things work after a cool down.

Would not hurt to have an extra tail and tail motor.
Chopper Tail Unit for DH 9104-14 $5.51 shipped - easy to replace and no soldering
http://www.aliexpress.com/product-fm...olesalers.html

Thank you for your fast reply...

I just checked the batteries...

I have 2 (both are 7.4v Li-ions)

Both were fully charged this morning.

One, after flight (cooled down now) is showing 7.75v left
Other, not used yet is showing 8.39v

As for the tail motor spinning up - it does spin faster when throttled up -- but (and I don't know if it is built to do this or not) --
When the throttle gets to about 3/4 speed, the tail motor throttles up until that point and then just holds its speed at that point.

Example = Throttling up to 3/4speed = tail rotor @ max speed
Throttling up past 3/4speed = tail motor holds at its max speed and does not go higher.

As I said, when it cools down or for first flight of the day, the heli works perfectly so the gyro is working = Full forward/reverse and normal turns in both directions.

There is also a bit of another issue I noticed last night - when you put the Throttle Trim all the way up (throttle stick in off position) the Heli main motor starts up at lowest speed.
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Old Jun 24, 2012, 04:52 PM
Crash and learn
United States, PA
Joined Dec 2011
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Quote:
Originally Posted by jspcrepair View Post

When the throttle gets to about 3/4 speed, the tail motor throttles up until that point and then just holds its speed at that point.

There is also a bit of another issue I noticed last night - when you put the Throttle Trim all the way up (throttle stick in off position) the Heli main motor starts up at lowest speed.
Both of those seem normal, though I'd have charge my battery to check for sure.

Batteries look good.

My DH9104 never had a tail problem (or any problem for that matter) and I've really tortured it with maybe 100 flights and three times as many crashes. Still, never flew it on a hot summer day and I would not know about overheating problems.

Rotation nose left sounds like a tail problem. Inspect the tail gears for bad mesh or broken teeth, and tail rotor for animal hair or grass wrapped around it.

Strange that the tail works fine for a few minutes. Could be overheating if it is working hard from the gyro trying to prevent nose left rotation. See what happens with the "LEFT/RIGHT TURN" knob fully counter-clockwise and then again with the knob turned clockwise until the tail motor speeds up.

May have to buy a new tail or new tail motor to solve the problem.
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Old Jun 24, 2012, 05:45 PM
Brakes? Who Needs Brakes?
United States, WV
Joined Jun 2012
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Quote:
Originally Posted by Ribble View Post
Both of those seem normal, though I'd have charge my battery to check for sure.

Batteries look good.

My DH9104 never had a tail problem (or any problem for that matter) and I've really tortured it with maybe 100 flights and three times as many crashes. Still, never flew it on a hot summer day and I would not know about overheating problems.

Rotation nose left sounds like a tail problem. Inspect the tail gears for bad mesh or broken teeth, and tail rotor for animal hair or grass wrapped around it.

Strange that the tail works fine for a few minutes. Could be overheating if it is working hard from the gyro trying to prevent nose left rotation. See what happens with the "LEFT/RIGHT TURN" knob fully counter-clockwise and then again with the knob turned clockwise until the tail motor speeds up.

May have to buy a new tail or new tail motor to solve the problem.

I opened up the rotor housing and both gears look good, nothing around either motor pin or rotor shaft, rotor shaft moves slightly in and out freely - nothing seems caught in it and nothing is rubbing anywhere to slow it.

I will try the full counter-cw and full cw test shortly and let you know (and I am assuming you also mean to try it by turning off the controller then turning the knob then turning it back on before each direction test)...
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Old Jun 24, 2012, 06:01 PM
Brakes? Who Needs Brakes?
United States, WV
Joined Jun 2012
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Quote:
Originally Posted by Ribble View Post
Both of those seem normal, though I'd have charge my battery to check for sure.

Batteries look good.

My DH9104 never had a tail problem (or any problem for that matter) and I've really tortured it with maybe 100 flights and three times as many crashes. Still, never flew it on a hot summer day and I would not know about overheating problems.

Rotation nose left sounds like a tail problem. Inspect the tail gears for bad mesh or broken teeth, and tail rotor for animal hair or grass wrapped around it.

Strange that the tail works fine for a few minutes. Could be overheating if it is working hard from the gyro trying to prevent nose left rotation. See what happens with the "LEFT/RIGHT TURN" knob fully counter-clockwise and then again with the knob turned clockwise until the tail motor speeds up.

May have to buy a new tail or new tail motor to solve the problem.

Ok... ran the test as you said.

Since Heli hasn't been used for an hour or so, it is good and cooled --

Controller off > trim full left > controller on > heli flew fine with left turn because of trim full left and... using Right stick, heli flew fine...
Same thing for opposite direction.

Did not fly for any length of time because I knew it would start spinning out again in a few minutes...

You said it could be an overheating problem... that is what I am leaning towards because the housing does get pretty hot after about 5 minutes flight.

I am going to go fly it for a while with the new fully charged battery and see what it does and after/if it spins out, I will set it down and allow it to cool then try again to see if it flies correctly.

I am just hoping I don't have to order new parts for it already but if I do... can you suggest any "Brushless" motors as I know the brushed motors are not as good and will wear out faster than the Brushless types.

Thanks again
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Old Jun 24, 2012, 06:47 PM
Brakes? Who Needs Brakes?
United States, WV
Joined Jun 2012
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Ok... I took it out for some more flying and here is what happened...

Cool, fully charged battery, flew fine for about 5 minutes.
Went to take off and fly more and after 3/4 throttle, it began spinning again and ONLY lowering the throttle allowed it to stop and make a right turn.

Then it started spinning again and could not be turned right.

I have noticed that at full throttle, it loses all ability to stay trimmed or turn right so my guess is the tail motor is weak and starting to die.

If there might be another issue, I would be glad to hear it.

------------------------------

Additional Info:

I read in another forum where someone said it could also be that the small brass gear is stripped from the pin -- I checked that too because it has gotten stuck in grass a few times and stopped the tail blade from turning.
The gear seems to be tight on the pin and nothing is broken and the gears mesh correctly.

I now know the gyro is fine because to test it, I set everything at center on the controller, held the heli in my hand and turned everything on.
I throttled up just enough to start the blades turning.
While holding the heli, I turned it by hand "Nose Left" and the gyro compensated by making the tail rotor go faster.
When I turned it "Nose Right", the gyro compensated by slowing the tail rotor.


I am really Stumped and frustrated by this!
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Old Jun 24, 2012, 09:03 PM
Crash and learn
United States, PA
Joined Dec 2011
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Originally Posted by jspcrepair View Post
Cool, fully charged battery, flew fine for about 5 minutes.
Went to take off and fly more and after 3/4 throttle, it began spinning again and ONLY lowering the throttle allowed it to stop and make a right turn.
That tells me the tail motor is good, becomes weak during the flight, and recovers somewhat if you back off the power. Sure looks like a heat problem with the tail motor and there may not be anything wrong with it.

A new tail motor may be better or the same.

Hover (not moving forward) is hard on the tail motor. Flying fast forward means the airflow will help keep the tail steady and ease the tail workload as well as provide cooling.

If you are up for it, do a flight with only nose left turns. Nose left turns slows or stops the tail motor, giving it a chance to cool. And keep moving forward.

"LEFT/RIGHT TURN" knob fully counter-clockwise and then again with the knob turned clockwise until the tail motor speeds up. No need to turn anything off when you try this. I think this could be turning the gyro off, then setting the gyro to match the rudder & throttle. Interesting to try yet not likely to fix any problem.
---

Oh, brushless motors. Better to buy a 4 channel helicopter that already has it. For the DH9104, you would have to replace the receiver PCB with another receiver, two ESC's, BEC, gyro. And you would need a new transmitter and the brushless motors.
.
Cheaper and more fun just to buy a 4 channel V911 RTF ($40) and a V911 BNF ($20). To fly while the DH9104 is cooling.
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Old Jun 25, 2012, 01:58 AM
Brakes? Who Needs Brakes?
United States, WV
Joined Jun 2012
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I may just have to break down and buy a new tail motor - I am hoping to find someone who has just the motor because I really don't need the whole pipe unit and would rather spend less than what the whole unit would cost (even though it really isn't much).

Just in case anyone may have mistook what I said here: "Cool, fully charged battery, flew fine for about 5 minutes.
Went to take off and fly more and after 3/4 throttle, it began spinning again and ONLY lowering the throttle allowed it to stop and make a right turn."

Once the spinning happens with full right trim, full right fine tune trim, and full right stick, Lowering the throttle only slightly stops the spinning - it will not turn right and because the throttle is low, it begins to descend and when I try to fly it close so I can get it, I will throttle up a little and the spinning starts again so I have to eventually drop it where it is.

Quote:
That tells me the tail motor is good, becomes weak during the flight, and recovers somewhat if you back off the power. Sure looks like a heat problem with the tail motor and there may not be anything wrong with it.
lol... if the tail motor becomes weak from heat, that tells me that there is something wrong with it if it gets weak from the heat it is supposed to produce... lol

The strangest thing is... for about a week, it flew perfectly without any problems... it just started doing this a few days ago.
I even thought it could have been the wires I wrapped around the tail for an LED I put on the end of the tail - on the highest tip of the Tail Balance Stabilizer - so I unplugged that thinking it could have been creating electrical interference but that wasn't it either.

The Heli has had a couple crashes as I said... first one was nose first into an outdoor air-conditioner unit (only scratched the paint on the nose). Second one was a light wind took it nose first into a wall (again, only scratched the nose up). Third was sideways into a wooden banister railing (not a real hard hit but popped the canopy off the pins and slightly bent the flybar - which I straightened out). It popped off the pins easily because I reamed them out a little to make it easier to take off for battery changing. The last crash was a nose dive from about 20 ft into the ground (grass had just been mowed so it was fairly soft).

None of these crashes changed the way it flew at all - I was able to fly it again and again after each one with no trouble.

Even today, it skimmed along a vinal siding covered wall doing about 10/15mph so I quickly shut off the controller to avoid damage to the main rotor or blades (it fell powerless about 9ft).

Quote:
If you are up for it, do a flight with only nose left turns. Nose left turns slows or stops the tail motor, giving it a chance to cool. And keep moving forward.
I will try the left turning as you mention but It is really hard to make left turns with this thing because it wants to turn very fast to the left.

Right turns are quite smooth and often wide because of the torque from the Main rotor being Left and Left turns are "Whip Around" and even sometimes spins 360 before I can stop it... lol

Quote:
"LEFT/RIGHT TURN" knob fully counter-clockwise and then again with the knob turned clockwise until the tail motor speeds up. No need to turn anything off when you try this. I think this could be turning the gyro off, then setting the gyro to match the rudder & throttle. Interesting to try yet not likely to fix any problem.
I didn't turn off the Heli for this, only the controller but I will try it again without turning anything off.


I was of the impression that all I would need for a motor change would be to get a motor that has the same speed and battery use (voltage)... why would I have to change the PCB and all that other??

I really like this Heli... Looks, Flight, Ease of flying... I would hate for this experience to dampen the fun that this thing actually is when it works correctly and I don't want to end up with a $60 Shelf Ornament either.

Since the Motor (or tail unit) seems to be fairly cheap, at least it is worth a shot.
And if it fixes the problem, I will report back so everyone knows that was an issue.

-----

Oh, and earlier today when I was flying it and it started the spinning again, I brought it down and felt the tail motor housing and it was warm but no where near as hot as it had gotten a few days ago.

When I felt the heat on it that day, I thought "Why in the world didn't they just build a better Tail Motor Housing like out of Aluminum to disburse heat like a heatsink in a computer because plastic will hold the heat like an insulator... and why didn't they make a longer "Cage" for heat to escape... I read where someone had actually removed the tail motor and drilled small holes in the plastic tail motor housing to allow for better cooling.

I have been looking all over for something like a metal motor housing but can't find anything even close... although I did see one model that had the "Baby Blue" aluminum tail motor housing that matched the color of the Blade Grip plates and thought maybe I could make that work.

-----

Since you say it sounds like the tail motor may still have nothing wrong with it, is it possible that there could be another problem somewhere else in the Heli causing this spinning??


Thanks again for all the help and replies... maybe we can all figure this thing out together
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Old Jun 25, 2012, 02:26 AM
Brakes? Who Needs Brakes?
United States, WV
Joined Jun 2012
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Sorry I write so long of posts... I just want to make sure I get all of the information I can to you for analysis
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Old Jun 25, 2012, 02:57 AM
Crash and learn
United States, PA
Joined Dec 2011
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Originally Posted by jspcrepair View Post
"Cool, fully charged battery, flew fine for about 5 minutes.
It comes down to what happens after 5 minutes.

You increase throttle.
The main motor may be robbing remaining battery from the tail motor.
The tail motor may be over heating.

Replacing the tail motor may fix it.

Your descriptions are excellent.
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Old Jun 25, 2012, 03:13 AM
Micro Heli mods
Tumppi T's Avatar
Finland, Tuusula
Joined Mar 2012
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Originally Posted by jspcrepair View Post
I may have to try that... would like to find the motor only as I don't need the holder and pipe...

I wanted to ask -- Where did you find Metal Canopy Pins?
I would like to have metal ones for mine because the plastic ones are too flexible and the canopy pulls them forward a little.
Hi jspcrepair....and welcome to this forum.

I bought the aluminium canopy bolts from ebay.
Put words "Trex 450 Canopy Mounting Bolt" in eBay search and you will find many options

- Tumppi
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Old Jun 25, 2012, 03:24 AM
Micro Heli mods
Tumppi T's Avatar
Finland, Tuusula
Joined Mar 2012
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Yesterday i had excellent flying session

There was no wind at all so i was able to trim my heli well.

Now my DH is running perfect with the brushless main motor ....next step is to change the tail motor to brushless version as well.

I have 1800 mAh 25C 7.4 volt LiPo:s and i flyed about 15 mins with each battery

Tip: If your DH is swaying when hoovering .... tighten little bit the screws of the "double ball joint parts" between the main blades.


Some pics ...... new link rods for the second servo:






And the small but powerfull BL motor:

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Old Jun 25, 2012, 03:45 AM
Micro Heli mods
Tumppi T's Avatar
Finland, Tuusula
Joined Mar 2012
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Originally Posted by jspcrepair View Post
Sorry I write so long of posts... I just want to make sure I get all of the information I can to you for analysis
I read thru all your posts and my wild quess is that your main motor is broken
...it takes all the energy so the tail motor doesn't get enough.

The original motor has very poor brushes and i was have to replace quite many motors before i got the brushless version. The original ones doesn't last very long.

The best original style main motors i have tryed are MJX F45 motors.
You may buy them for example here: http://www.feala.com/mjx-F645-F45-RC...-F45-parts.htm

The table of my problems so far:
- 75% main motor (with original motors)
- 15% battery (with original batteries)
- 5% tail motor
- 5% mechanical (problems after crashes .... twisted flybar etc..)
- 0% PCB & transmitter
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Old Jun 25, 2012, 04:25 AM
Crash and learn
United States, PA
Joined Dec 2011
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Originally Posted by Tumppi T View Post
OUTSTANDING! Simply a work of art. Make one aileron servo do the work of two servos, and get rid of both fixed forward links that were fighting the swashplate pivot.

I hope Ken notices this. Nice work Tumppi.
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Old Jun 25, 2012, 01:40 PM
Brakes? Who Needs Brakes?
United States, WV
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Thank you everyone for your replies and help in trying to solve this...

Hopefully, it will get worked out by trial and error but I will consider all of the suggestions.

As far as the main motor, it seems to be ok in every respect but never know, it could very well be taking the power from the tail motor.

I did read in another forum that someone had to replace like 3 tail motors already and the heli was only a few months old... makes me wonder:
1) is it that the tail motors are just cheaply built and go bad fast?, or
2) is there actually something else (like you said about the main) causing it?

I have ordered a replacement Tail Unit and will try that first and if that doesn't solve it, I may look into a Main Motor before anything else major like a circuit board or controller.

Tumppi T: Thank you for that info... I found some on Amazon.com called "Align T-Rex 450 Canopy Mounting Bolt HS1212" for $4.80 a pair. These are flared out where the screw goes in so they look a little different than yours. I would guess the flare would act as a washer on the outside of the frame (which is a good thing) so the hole could be drilled the same size as the screw. There are many others too.

I would really like to "Armor" this one a bit by replacing what plastics I can with metal parts for a more sturdy heli. You would think for the design and type of heli it is that the company would have taken all that into consideration and built it a little tougher... considering the sheer size alone would cause it to be a little heavier than some and would get damaged by a fall easier with plastics.

By the way, you did a very nice job on the upgrade mods and it looks great with all the colorful matching of parts and the technical workings look a lot like what a real helicopter has in the Rotor Head.

You mention that you have tried original style main motors from other models... In case I need a main motor, which one would you consider the best one that worked, fit, and acted like the original without modding anything?
Will that MJX F-45 F45 work in the DH9104 without modding?
I found this one - MJX F645 F-45 F45-014 Main Motor at 2 places for $8.99 to $10.00 - is that it?

As I think I said, I am quite new to the large scale RC Heli's so I don't know too much about them but I am willing to learn all I can because I love Helicopters and have always liked the hobby of RC (mainly boats and heli's).

It's a good thing the parts are pretty cheap. I just put out only $8.25 for a new tail unit including shipping from a place called RC Roanoke (which is quite close to me).

I also found a part I would like to try, for both looks and for heat dispersion - it is the Main Motor Heat Sink (baby blue) for the Honey Bee CP3 Heli. If it fits, it would help cool the main motor better.

Later on, I would love to be able to get an AH-6 MD500 Little Bird Fuselage for this 9104 as I love the military design and style of the war-heli's - I would go for the AH-64 Apache but can't really find one that would work well on this size DH and they seem to be quite expensive. There is a guy who builds them from the GI Joe BBI Apache Toy Model... he takes the model, guts it, and uses the shell and cockpit and custom builds the mechanics inside and even puts an electronic device in them that makes the sounds of a real AH-64 when fired up and flying.

I may just hold on that until I get another heli that is built better and more powerful - a 4 or 6 channel.

Thanks again
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