" i need a new skyviper frame


I have replaced the right front motor 3 times now. Not from crashes. It is just the right front. Not the others. I have been using motors from Hobbytron that look identical but I have to re-use the pinion gear and splice/solder the leads to the connector. No Big deal. This time, the motor was a little bit tight coming out. The new one would not go back in. There was severe interference between the pinion and the driven gear. Careful inspection showed no damage to either gear but the gears would not slip into mesh.

I tried another spare motor, same result. I tried the original motor with the original gear from the right rear. It would not fit either. I then tried the new motor with the swapped gear in the right rear position and it fit. After trying several other combinations and locations it has become obvious that the frame is the problem. The spacing between the motor shaft center and the prop shaft center at the right front is about .008" less than the spacing of the other three motor positions. The gears can not be forced to slip into mesh.

It was obviously not like this when new. I did not measure it then but I have flown this quad about twenty times and I have previously replaced this motor. Something has happened. I have not had any hard crashes and I doubt that could cause this anyway. At this point, all I can imagine is that motor heat has somehow warped the plastic of the frame. I doubt that there is anything that I can do to reverse the warpage.

I have requested a replacement part from Skyrocket but I may not live long enough for that to happen. I have also offered to buy any returned or salvaged parts from them and I make the same request here. Have you got a spare frame?

By the way, measuring the shaft spacing accurately is not easy. I could not get that measurement but I could get a very accurate measurement of the spacing difference at the two locations. Here is how I did It. I used two new motors without pinion gears, one in each location. There is a gap between the bare motor shaft and the prop gear. I could measure the difference in the two by finding what wire gauge could be placed in the tooth spacing of the prop gear that would just pass by the motor shaft. A wire size .057" would pass the “good” location but not the “bad” location. The “bad” location would only pass a .049" wire size. A difference of .008" which is more than enough to prevent the gears from passing.

I have a fairly well equipped “hobby” machine shop which includes a set of #size and wire gauge drill bits and a precision micrometer to measure them with. It doesn’t give the shaft spacing and is only an approximation of the gap spacing but it is a very accurate measure of the difference.


I got a response from Skyrocket asking for more information. Not a fix, but a very quick response! I will keep this updated with reports of their help.

Hi Jerry,

What you are describing is most likely your theory about the heat. If the props get obstructed, say in a tree branch or really tall grass, the motors will get very hot, as they are brushed motors. While we have some code in place to prevent obstruction, it can be overruled by user input, rocking the stick side to side, for example. Yes, these motors can become hot enough to change the pliable nature of the plastic when obstructed.

Add to that, when you replace motors, you should replace the whole set, as our Viper motors are custom builds, it’s hard to find a matching motor from third party. This will cause the new motor to probably work hard to match the others.

I think your best bet might be to get a heat gun and slowly, gradually apply heat to the plastic area and (with a motor in place) try getting the gears closer together. Be mindful that you don’t warp the arm, though, as that will affect the plane of the propeller.

Also, since it sounds like you have a nice shop, I’d recommend getting a nice set of Calipers for measurement. Don’t get a crappy set from Amazon… we keep sending those back. The best ones are made in Japan.

Hope that helps,

Thanks for the confirmation. Must be heat. I have been able to avoid trees and I use the lid from a plastic tub for takeoff but RTL usually puts it down in the grass. The last time that I flew, I was flying very long and high missions that pushed the limit of battery capacity. I had several batteries and I flew consecutive missions. The last flight ended with an unplanned landing. I was using a battery that I thought may be failing so I thought that had been the problem so I didn’t inspect the Skyviper for damage. The following day, with batteries recharged, the right-front failed to start up on arming.

Measuring is important in a machine shop. I have a wide variety of calipers for inside and outside calipers but I consider digital calipers to be second to a good micrometer in accuracy. Access to the measurement area is usually the big problem when deaiing with micro machines. Gauge wires are commonly used to measure gear clearance tand the shank of small drill bits serve as a good substitute for gauge wires.

In this case, the gears are to close together so I must move them apart. A heated scriber point pressed into the plastic between the motor and the prop shaft may do the trick but I will wait for more response from Skyrocket before I try that.

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I had an issue getting gears to mesh when I replaced a motor , few weeks back . I had put pinion gear on upside down , and either the pinion is tapered or has a flange ridge on bottom that would not allow gear to mesh properly . Wonder if that is happening to you

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Yes, there is a slight flange on one end of the pinion. I noticed that the first time I changed a motor. Not the problem here. There is a distortion in the frame. Looking and testing further, I have found two things. There seems to be a misalignment of the shafts caused by the heat. The bottom of the motor is farther from the prop shaft axis than the top of the motor. That causes the top of the motor with the pinion to tilt in. The other thing I see is that the inside surface of the motor seat is covered with small raised blisters, helping to push the motor towards the prop. If I had a 8.5mm reamer, it would be easy to clean up the bore, but I don’t. That translates to .3346" which falls between 5/16" and 3/8". I have some adjustable reamers but they require a through hole which would take out the shoulder stop that holds the motor. I may have to grind a custom hand reamer to do this right.

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Hi Jerry,

I know for a fact that we don’t have frames to sell. It’s not one of our normal items.

Let me know how you get along with your fix. If it’s all for naught, I can see if I can recover a frame from scrap here and send it out to you.

Let me know.


Thanks, Matt, a scraped frame is probably the only way to get this right. I did grind a hand reamer and made some progress getting the bore cleaned up but the tilt is another matter. I did get the gears to mesh but it probably needs another .002" to run freely. The motors will arm but the right front stops almost immediately when disarmed. It will fly and hold stable at altitude, but the flight time was less than three minutes on a full battery. Too much power draw leading to more heat and more dead motors.

Send me a scrap frame if you can. Let me know the cost.

Care package received, Matt. Thanks for your involvement and assistance.

Reassembly and testing starts tomorrow. The black color is definitely not a problem. I am looking up at the bottom when its flying and it doesn’t get lost in the high grass since it always knows the way home.

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