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Jan 18, 2012, 04:34 PM
Crash and learn
Originally Posted by Chester1 View Post
The 9116 is still not available on
Wreck the DH9104 first. By that time the latest and greatest will be out.

The DH9116 is smaller than the DH9104, though it is 4 channels adding aileron roll left/right for the next skill level. And 2.4GHz. I wonder how many of the DH9116 control problems are actually transmitter problems, maybe using 1.2v nicads instead of 1.5v standard dry batteries. I think the DH9116 transmitter is 9v, where the (outdated) DH9104 transmitter is 12v and should be able to work down to about 6v as the batteries die.

DH9116 is too big to fly in my bedroom, so I have a Solo Pro V2 enroute from China with 6 LiPo batteries, a 4 channel much smaller than the DH9116.

These things are toys, but I am amazed at the Chinese technology after taking the helicopter and transmitter apart to see what makes them work (sometimes not work).

And modifying is half the fun - something can always be made better, at least as we see it.

I couldn't resist. The DH9104 transmitter worked fine at 4.5 volts (with only 3 of the 8 alkaline cells). At least at 1 meter with no transmitter antenna. Not bad for 40 year old technology. Didn't work at 3 volts. Will have to figure out a way to try a 3.7v LiPo without shorting the terminals. A 7.4v LiPo should work fine. An 11.1v LiPo even better. I suppose the best range is with 12v, maybe not if the output transistor is biased to operate in a small linear range, which appears to be the case.
Last edited by Ribble; Jan 18, 2012 at 06:10 PM.
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Jan 18, 2012, 07:40 PM
Chester, the PCB and servos from the 9116 should work for the 9104 frame. With the two upper frames being mirrors of one another, it is possible an order for another frame to get the exact frames on each side. The electronics do not care what bird it is in just as long as all the parts are there. I might do this myself as I do like the heavy and larger frame. Once I get it dialed in and figure I am doing well enough, I will try it or just order a 9116 just to have the frame, also. it would cost around $75 US for the parts, so it might pay just to order the entire copter. Who knows what will be out by the end of spring.
Jan 18, 2012, 09:04 PM
Crash and learn
Originally Posted by Ken59 View Post
PCB and servos from the 9116 should work for the 9104 frame.
A note of caution. The DH9116 uses a lower capacity battery with likely smaller main and tail motors. And some extra battery capacity goes to the receiver and extra servo.

My DH9104 ESC board has a least heat fins on the switching transistors and perhaps higher rated transistors and snub diodes.

Stormforce thinks the thick red loop could be a fuse link. DH9116 LiPo batteries are not readily removed and it may be to prevent battery fires. Probably can handle DH9104 motors. "MOPS (Motor Overload Protection System)" ??

Right click the photo and open in new tab or widow to enlarge.
Last edited by Ribble; Jan 18, 2012 at 11:32 PM.
Jan 18, 2012, 09:21 PM
Thanks Ribble! I sure wish I could get some specs on the motors for each. I do see the 9104 ESC is a more robust on the heatsinks. If I recall the motor in the 9104 is of the 370 variety, but the motor in the 9100 and 9116 is a 180. Again, the specs would be nice.
Jan 18, 2012, 10:00 PM
Crash and learn
Yea, I'd like to know what those 4 squares (top-right, only 2 visable here) are doing there. Original gyro crystal location?

I once built a digital clock that used those for setting the time by touching 2 squares at the same time.

I can ID nearly all components and their function from trying to draw a schematic of the DH9104 board, which is more complicated than this DH9116 board. It is a nice board though, not so busy as the DH9104.

Those two servo connectors are certainly a temptation.
Last edited by Ribble; Jan 19, 2012 at 12:00 AM.
Jan 19, 2012, 12:10 AM
I can see a 9116 coming in the future if nothing else comes out better. Just to do a convert and if it blows the ECS, it will just be a low cost fix and get the 9116 up again. That is after I get used to flying it before I experiment.
Jan 19, 2012, 11:37 PM
I should have my swashplate replacements in tomorrow and maybe get some flight time, if weather permits, with the new center pivot mod. I picked up some small screws with matching bolt which might actually sure things up a bit. Might look at a small 4ch for indoor practice and/or flight sim.
Jan 20, 2012, 01:48 AM
Crash and learn
Ken - "mounted a ball link on either side"

The part I didn't understand, so went back and read your posts again and I still can't figure how you did those ball links. In part because I never saw ball links until I started playing with the DH9104.

Actually, it is the balls mounted on the side of the old swashplate. You just drill holes and srew them in? And where did the balls come from?

It is very professional and doesn't appear to weaken any of the plastic parts.

Looks like the pivot point remains on the new swashplate center rotor and it also looks like the pivot point is on the plate below with the new balls. Can't be both if they are glued together?

Real nice though, and if (when) I brake something topside I'll do the same before fixing the damage.

Looking again, from the bottom of mine, the pivot is actually on the upper rotating swash and there could be enough play on the lower normal fixed plate. It worked for Sparky Paul, though he only has the rotating and fixed swashplates.
Last edited by Ribble; Jan 20, 2012 at 02:14 AM.
Jan 20, 2012, 06:50 AM
I looked at the way the original swashplate was designed. I thought of just drilling into the bottom piece and putting the balls there, but the ball links on the rotation would strike the newly attached ball link. So, once I made the piece, it solved this problem. I clipped the two together to see if they would work and it does. The bottom piece I made was from the top half of the old swashpalate (it was the rotating half). Once you get them apart, just drill out to a larger size to allow for movement. The balls links I installed are available from many shops, though I got mine locally. They are a set for a blade if I remember. Once I get the new bits in, I will do the final mod and take pictures and maybe video
to post.
Last edited by Ken59; Jan 20, 2012 at 06:56 AM.
Jan 20, 2012, 05:44 PM
Always, against the wind
Thetis's Avatar

Trimming after a crash

I have my 9104 for two months with more than forty flights with no problems and repairs. Last Sunday I flew her in a high school football field next to my house. It was a really calm and clear morning. I had a bad crash, but no breaks. I tried to fly her again but she was going around in a circle!!!. I tried to trim but no success. I went back home I charged the battery and took her for a spin and the same thing happened. I bought today a lazy Susan made from marble (very heavy). I taped her on and tried to trim. No luck. On low throttle let's say she trimmed to no spin around but as soon as the throttle is increased the trimming is lost and you must start all over again. Eventually, this kind of excersise can not be applied in the real flight. I checked the rear motor and blade and the seem to be OK. I also checked the PCB board for any lose ends or brakes but again everything is OK. Any suggestions?
Jan 20, 2012, 05:52 PM
Crash and learn
Thanks Ken. I'd like to see what is actually screwed into the sides of your new lower plate.

I hadn't noticed before that the pivot is on the rotating plate. The stock DH9104 has another set of pivots forward on fixed links. These forward fixed links were bending aft as the servo pushed up because I had already made the servo link longer by CCW turning the turnbuckle. It also explains why, with the forward fixed links removed, my swashplate can tilt right by pulling the servo turnbuckle to the left side - the fixed swashplate is lower than the rotating swashplate pivot and the fixed swash can move sideways but the rotating swash cannot, resulting in both tilting to the right side.

My DH9104 is trimmed well and I didn't fully understand why.
Jan 20, 2012, 05:57 PM
Crash and learn
Thetis - Stormforce has a test for the gyro. Hold the helicopter and increase throttle then rotate the helicopter by hand - the tail rotor will try to hold heading (correct the yaw).

OK, for the purists, the DH9104 gyro doesn't actually hold heading as it doesn't continue to correct yaw if the yaw isn't corrected.

After the crash, the DH9104 now rotates Clockwise (CW) or Counter Clockwise (CCW), looking from above? CCW means a weak tail rotor, while CW means too much tail rotor.

Inspect that the flybar does indeed change the blade pitch, no links off the balls, no bent flybar.

Another, test that the tail rotor is mixed with the throttle. Remove the main rotor plug from the Electronic Speed Control board. Increase throttle. The tail rotor speed will track the increasing throttle. Also check the gyro again and note that the tail rotor will indeed slow as the helicopter is rotated clockwise.

With the main rotor connector removed, increase thottle. Then test right stick, left and right, and note change in tail rotor speed. Now turn the TX upper right "left/right turn" potentiometer full CCW and test right stick rudder again. Turn pot full CW and test again. Note CCW kills any right stick, left rudder. Do same test with "backward/forward" potentiometer and note no effect on tail rotor, but servo does indeed tilt swashplate forward and backward, as does the right stick elevator control.
Last edited by Ribble; Jan 20, 2012 at 09:15 PM.
Jan 20, 2012, 10:44 PM
Got it running again, but no true test (modded swashplate) as the wind was kicking a bit. I tried to keep it low and dial it in, but the wind won the day. Found a the main shaft bent and got it pretty close bending it back (more on order). I have been looking around for better swashplates which may work. I might have found one and it may be a better answer than what came stock. Look up the SH8830. It has a metal swashplate which can be ordered for about $5. One place to find it is The only thing I can't find the tube diameter. Tempting to take a chance.

Not too sure of the mod, but it actually worked. Ribble, I know about the flexing and that is what I was trying to get out. The actual center pivot point for the swash is on the rotator. If I pivot it below, at the point where I mounted it, it would actually have to float under the swashplate. It has to do with the pendulum effect of the center point higher up. I did a little test by making a crude clip which provided a little pressure on the two pieces and it did work. Then, I did a "hillbilly" and used a rubber band to see how less pressure to keep it all together. It still worked, but I could see the swashplate rising off a bit. It may work, it may not. For now, I went back to one side fixed with original and the other with a servo to swashplate link attached to allow adjustment. I hope the wind dies a little tomorrow.
Jan 20, 2012, 11:21 PM
Crash and learn
I was surprised to see that my DH9104, when taking off with a wind, just wants to roll over. Was one of my 2AM flight festivals at my nearby park. Got about 45 minutes under a full moon before the wind picked up. At least no water puddles that time, just ice.

On another 2AM flight (still 2 weeks fying with no transmitter antenna) after tuning my receiver, I found myself walking 50 feet through mud puddles to salvage my crashes and thinking it was better only walking 15 feet with an untuned receiver.

Then I had my transmitter apart for reverse-engineering. Tried to increase output power and found that my transmitter antenna wasn't even connected.

Waiting for a full moon and not too cold to see if I finally get more than 50 feet range, now with a tuned receiver and a connected transmitter antenna.

I just can't get myself outside for morning flights when there is light and no wind.

Should try just before dark, but it must be mating season and even at 2AM, ice cold, and a school day, there are teen couples roaming my park. I don't mind crashing if noone is watching.

Flight tested at the park at 1:15am for 45 minutes until the 25F wind picked up and it started snowing. Now I am walking 200 feet to pick up my crashes. Gotta put more LEDs on the DH9104 as the blue LED forward only tells me nose in. Also flew 100 feet up into a tree, never had it that high before. Never had it fall 100 feet to the ground either. No damage, everything works. Loud "whack" when it hit the tree and leading edges look somewhat abused.
Last edited by Ribble; Jan 21, 2012 at 03:03 AM.
Jan 21, 2012, 11:09 AM
I got out a flew a little this morning. I am able to throttle up and take off without too much left drift. The problem I am having is with the response to moving the tail against the rotation of the blades. It is very slow when at higher throttle. When you throttle down, it can compensate faster, but the copter decends. I think it is a weak rear motor and I have another on the way, which I will test once it arrives. Any ideas????

I may try to design another swashplate adapter which puts the pivot center in the correct place. It really should be a 180 degree plate so you have true pivot on the one axis for a fixed pitch copter. Anyone know of a 180 degree swahplate for a 4mm main tube??

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