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EMAX 3526/05 odd underperforming symptoms

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Geoff Sleath05/05/2018 17:32:59
3272 forum posts
251 photos

I was hoping to test fly my DB Cirrus (Gypsy) Moth tomorrow. It's all ready to go and I fitted a prop to the motor for the first time about 30 minutes ago. I had run it off load whist setting up the wiring

I chose a 13x6.5 as a starter and expected it to be far too powerful (the spec suggests a 13x7 for 47 amps and 8600 rpm). I think I need around 500 to 600 watts for the estimated 6lb all up weight. perhaps less).

When I powered up I was surprised to find that I was only drawing about 22 amps (around 320 watts) and turning the prop at 7500 rpm. That equates to 500 rpm/v on a motor specified to be 710. A bit of a shock because I was expecting it to be an animal!

I use a similar motor on my DB Tiger Moth but the 3526/04 870 rpm/volt which I run with a 12x6 prop. I chose the slightly lower kv for the Cirrus so I could turn a bigger prop at lower rpm.

I can only think that either the motor is wrongly labelled or that it's faulty.

After all the discussion on arming plugs recently I inserted one in one of the motor feeds from the esc but never actually tried to run the motor other than to very, very briefly to see if it worked. I can't see why that should have harmed the motor but I reconnected everything directly with identical results.

The motor runs very smoothly but doesn't draw much current.

Any ideas?


gangster05/05/2018 17:48:05
929 forum posts
16 photos

In assuming that you programmed the esc to max and min throttle positions

Geoff Sleath05/05/2018 17:57:51
3272 forum posts
251 photos

Another lesson learned! After I'd posted and checked when I bought the motor (from Totem Hobbies on 16 Aug 2016 - it's taken me a while to build the Moth!) I suddenly realised it was the first time I'd used this esc (Black Mantis 60 amp) with the Horus. So I calibrated the throttle (I'd already checked it was set to 100% in the transmitter set up) by switching on with full throttle, waiting for the 2 beeps before closing it and I seem to have solved my problem.

The motor now draws 37 amps for 550 watts and 8900 rpm which should be more than enough to fly the model.

So let that be a lesson to my readers ... and me Simple things can trip you up even on topics in which you're supposed to experienced. That's the second time in about a week! Old age is rapidly encroaching.


Geoff Sleath05/05/2018 17:59:05
3272 forum posts
251 photos
Posted by gangster on 05/05/2018 17:48:05:

In assuming that you programmed the esc to max and min throttle positions

yes Yeah I realised I hadn't done that as I commented


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