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Motor pulsing

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J D 811/09/2019 13:10:55
1354 forum posts
78 photos

I recently bought a little Spitfire at a club bring and buy so no instructions.

Model fly's well enough, however at low power the motor pulses on and off about once a second. Could this be a timing issue?

ESC is an FMS-DT20 but in the programming setup the bleep codes are not like any other esc's I have. Thanks for any help. John.small planes

SIMON CRAGG11/09/2019 15:20:26
522 forum posts
15 photos

Have you tried various programming cards?

Some escs have a very odd sequence of beeps.

If you can find a card that works, I would first try the default settings and then play around with the timing.

Hope you get it sorted.

Gary Manuel11/09/2019 16:37:45
2056 forum posts
1515 photos

Have a look at the following video. There is a programming chart showing all the beep codes at around 2:15.


Edited By Gary Manuel on 11/09/2019 16:41:06

J D 811/09/2019 19:12:02
1354 forum posts
78 photos

Thanks very much for the info Gary.

Tried auto, low and high timing, still the same pulsing at low throttle. Also gave restore factory setting a go there was no change.

Will try again in case I did it wrong but may end up swapping it out for a spare BRC hobbies esc I have

Cheers John.

Simon Chaddock11/09/2019 19:38:12
5569 forum posts
2930 photos

J D 8

Have you tried removing the prop to see if it still does it with the motor unloaded?

"Substitution" (one item at a time) is the most powerful way of diagnosing any fault.

I keep a spare working motor, ESC and battery driven by a servo tester to cover just this sort of situation.

The spare items do not even have to be of identical specification as in most case all you are doing is checking that it works rather than checking it delivers the same power. wink 2

J D 811/09/2019 22:04:49
1354 forum posts
78 photos

Hi Simon, Have tried with no prop same result but have thought of connecting in another motor to the original esc as a test.

If that works I will have the fun of trying to remove original motor as it does not want to come out even though screws have been remove, still solid in position.

Thanks John.

G194011/09/2019 22:19:23
3523 forum posts
1 photos

The most likely culprit is a quirk of the esc design (or a fault in the esc. Motors are relatively simple and either work or have an obvious fault ( eg loose magnets, burnt out winding, faulty bearings) so would think yours is probably OK.

ESCs on the other hand are very sophisticated and need first to generate a signal to create a rotating magnetic field at a rotation proportional to the throttle input and then, via power semi-conductors feed high currents (the average smallish foamie like - say a Wot 4 - draws upwards of 40 amps at full throttle). Power means high current and with it higher temperatures, neither of which electronic circuits particularly enjoy. Then there's the BEC providing low voltage to the receiver and servos.

In view of that I'd try a different ESC before looking elsewhere. Make sure it has, at least the current carrying capacity as the one it replaces. As Simon mentions above, one step/substitution at a time is the reliable route to fault finding.


J D 812/09/2019 11:41:15
1354 forum posts
78 photos

I was turning the motor over by hand this morning and while it felt fine going forward when turned in reverse there is a slight click and stiffness at one point. Will let you know what I find.

J D 812/09/2019 12:32:50
1354 forum posts
78 photos

Are there only two grub screws holding these bell type motors to the mount? They are out, the Spits cowling is not removable so it is hard to see anything. A small hole either side allows Allen key access.

J D 812/09/2019 21:54:42
1354 forum posts
78 photos

After much wiggling and pulling motor came out leaving the mount in the aircraft, why it was so reluctant I can not tell. Substitution has shown that neither the grating motor or jittering esc are fit for use.

As I only payed the price of the Futaba 2006 rx that came with it no great loss. Will look out for replacement motor [ have esc to suit] as airframe is good and its a nice little flyer.

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