Model Boat Mayhem
Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: captain_reg on May 18, 2022, 12:00:11 pm
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I've recently got back into the hobby after a long absence. I've been discovering the joys of brushless and have converted an old (always underpowered) model to brushless as a bit of an experiment. I went with the 'Mtroniks G2 Hydra 30 system' and ran the boat with great success on a 9.6v NiMh battery pack borrowed from another boat. I was initially skeptical and was convinced that the tiny motor could do what the spec sheet promised... the description on the sellers site stated it was suitable for a 45-50mm prop, seemed incredible but with an x40 prop the boat was totally transformed and was an absolute blast. Things were cool and I had it skimming across the top of the water like a dream. Next step was to give it a dedicated 12v setup (2x 6v NiMh packs in series) and I've noticed something weird on its first bath test.
The motor starts as usual, increasing revs and pitch linearly with movement of the stick on the transmitter. Then as it approaches half way the pitch and thrust drops quite noticeably before picking up again. Best way I can describe it is like a gear change. It does the same with decreasing throttle, the revs drop as expected with bringing the stick back towards neutral and then suddenly pickup, like changing down a gear while decelerating, before continuing to decrease to a stop. I can't really handle full throttle in the bath without making a mess or the prop just aerating but it only seems to do one pitch prop between neutral and full-ish throttle.
Never seen or heard anything like this before, anyone have any ideas?
I've got a video which I'll link once I have it uploaded somewhere.
Edit: Video Link
https://youtube.com/shorts/J1rUpSktyvA
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Sounds like some sort of voltage drop under load. Possible causes abound, but I think the X40 is proving too much load at 12v. Try an S40 or x35 prop instead, see if the problem persists.