I just happened upon this discussion about the IVOProp IFA motor. Not long after my first flight in October of 2017, I started to have a string of failures with the prop electric motor armature. After spending way too much money on replacement armatures, I was determined to get to the bottom of the failures, or at least find a cheaper alternative.


I got in touch with John Holmes at Holmes Hobbies in Missouri. He specializes in custom motors for remote control enthusiasts. The 540 type motor used in the IVOProp is among the motors he makes and sells. John was enthusiastic about helping me find the culprit.


John examined more than one of my failed armatures and determined that the failures I was experiencing were due to the armature windings shearing apart. Eventually, we found that the breakage would occur where the windings meet the tabs connecting them to the commutator. This may or may not be the failure everyone else experiences, but it is definitely the failure I was having.


At some point along the way, I balanced the Medium IVOProp using Dorsal's generously-shared prop balancer. I wanted to make sure I minimized excess vibration as a source of motor failures.


During the time I started having these motor failures, I was developing a constant speed controller for the IVOProp. The many activations of the motor during constant speed operation no doubt exacerbated my motor failure situation.


John Holmes attempted to cure the winding breakage with an epoxy he had on hand. He applied this around the top of the armature, hoping that it would prevent the windings from shearing at the tabs. That attempt lasted only a few hours before I had another failure. John's epoxy was relatively soft, so we wondered if a stiffer epoxy might be the answer.


To make things easier on myself, I decided to try to roll my own armature, making a jig to machine the armature shaft so that it would accept the small gear that drives the IVOProp gear box. Once I was able to machine the shaft, I could experiment with readily-available, low cost armatures.


I followed John's lead with the epoxy idea, but used good-ol' Hysol 9460 to encase the top section of the armature windings. I did that with a twelve-dollar, twenty-seven turn armature I bought off of eBay (actually that was the whole motor; I only used its armature). I have not had a failure since -- about 140 hours so far -- even with the abuse the motor takes from the constant speed controller. I do keep a backup armature handy -- I bought one of the Holmes Hobbies hand-wound armatures, modified its shaft and epoxied its windings.

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