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Old Apr 15, 2004, 03:54 PM
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Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
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Another nail in the MicRoTeX coffin ...

Well I received my 20/5/18 today exactly one month after ordering from a vendor that advertised them as "in stock now".

First check with a multimeter after reading some of the other posts, yes there's an electrical circuit between the motor shaft and any of the three winding contacts. That's not so good. I measure 9.7 ohms each time, and 1.7 ohms between any two of the winding contacts. Other than that the motor seems mechanically fine and spins smoothly by hand with mild 'cogging'.

OK, fit an APC-SF 8x3.8 and connect to my 3S pack. First test, using the default 'soft' timing on my Jeti Advance 8A ESC. Ran smoothly up to about half throttle, then the 'screeching' described by others. OK, switch the ESC to 'hard' timing (recommended in the instructions for Axis). Now the motor runs beautifully, smooth startup, throttles well. Hmm ... backplate is very hot after only a couple of seconds on full power. Check the amps, yikes 11.1A

So, let it cool off then and briefly back to full power to check the rpm. I get 7,000, well that's a long way short of the advertised 8,210 rpm (and 7.7A) for this motor/prop/cell count.

Final test, increase power till the meter reads 7.7A (around half throttle) and see what rpm I'm getting - answer, 6,400.

So on the Jeti Advance it runs fine, but performance is way down on spec. and current consumption is way up. This motor is going straight back ...
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Old Apr 15, 2004, 04:47 PM
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vintage1's Avatar
East Anglia, UK
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Interesting. What did you meaure the ohms with? The windings should be a lot less than 1.7...and of course there should be no case short.

Sounds like there are production and quality control problems. The windings shouldn't short to the case in the first place, and they should be continuity tested to make sure they aren't before shipping.

Which is a shame. Even if the manufacturer fixes the problems and comes up with a half decent motor, who will believe them?
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Old Apr 15, 2004, 06:17 PM
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United Kingdom, Bracknell
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Checked with a digital multimeter using the lowest resistance range (200 ohms). That was after a continuity check that got a very definite 'beep' on windings to shaft! I was just using the standard test probes, so may not be very accurate in terms of the numbers.

The motor did run very nicely, excellent startup and slow running and very smooth at full power (I always balance my props though ). Just not giving anything like the advertised performance & efficiency.
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Old Apr 15, 2004, 06:35 PM
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Chattanooga, Tennessee, United States
Joined May 2003
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Like you, Bill - I've had enough! I can't imagine that even if we fix the ESC programming problems, we can ever get close to the spurious numbers suggested on the Microtex data sheets! Thanks for those measurements indicating shorts between the windings and the shaft - I figured there had to be something wrong, but Geologists are not the best people to conduct investigations into electrical problems!

I think I may have mentioned this but my late father LOVED Woking when he stayed there during a Sabbatical in 1971.

Cheers, Phil
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Old Apr 16, 2004, 12:12 AM
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Alberta, Canada
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What is the "Hard" timing setting on the Jeti? Is that comparable to High Advance on the castle phoenix 10?
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Old Apr 16, 2004, 01:20 AM
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Helena, MT
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So - Phil- is yours going back - are you giving up on this one?
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Old Apr 16, 2004, 03:56 AM
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Bill Glover's Avatar
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Quote:
Originally Posted by Mikey-flies
What is the "Hard" timing setting on the Jeti? Is that comparable to High Advance on the castle phoenix 10?
I don't know, it's the setting they recommend for outrunners like Axis. Seems to work pretty well, whatever it does!
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Old Apr 16, 2004, 07:28 AM
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Chattanooga, Tennessee, United States
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Is it related to "soft start"/"fast start"? Or is it a "timing" thing? Shawn Palmer suggested I use Low Advance Timing on my Nippy, and it seemed to solve the problems I had with that, but having just re-read the Phoenix instructions, I am altogether confused: I quote "The controller senses the motor type by its inductance, and automatically sets the maximum advance according to motor type (e.g.: outrunner motors will automatically be run at higher advance setting)".

So why did Shawn suggest, and I bother, to choose "low advance" when apparently the controller will over-ride my programming and run it at "high advance" anyway?

I got my Microtex from Bob Breaux and I don't want him stuck with a dud motor - I'd like to find a way of sending it back to the manufacturer directly.

Cheers, Phil
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Old Apr 16, 2004, 08:29 AM
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I've spoken to the UK source of my Microtex today, he's sending me his own personal one (with manufacturer's spec sheet) to test, and will replace with a (tried & tested) PJS 300 if necessary. I passed on the info. about a circuit apparently existing between winding contacts and motor shaft ... that's gone to Freeair in Czechoslovakia. Will let you know of any response.
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Old Apr 16, 2004, 08:37 AM
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Alberta, Canada
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Somewhere I read (I think in the manual but I can't find it right now) that the phoenix 10 has 3 different ranges for timing and the controller selects the best fit in the range. With 3s 340 kokam's and a 9x4.7 prop (or 2s and an 11x7 HD) the nippy would start but cut out at about 2/3 throttle. It would start to hiccup and sputter and sometimes make a loud screech. By changing the advance to "high" (I think it was something to 30 something degrees??) these problems went away. I also do use the soft start as it had issues starting reliable on the hard start setting. I was wondering if perhaps the same settings would help with the microtex problems (at least some of them).
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Old Apr 16, 2004, 08:59 AM
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Hi Mikey - as you see in Post #8, that's exactly the opposite of what Shawn told me to do - my Nippy had EXACTLY the behavior you describe, but after I changed to Low advance timing its been perfect. But if the controller over-rides the programming anyway? - where am I?

Cheers, Phil
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Old Apr 16, 2004, 09:51 AM
Maryland
Joined Nov 2003
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Thats just one more to build your own... no one is gonna take the time and care to put something together right for your plane except you.

There's a saying that goes something like "If you want something done right...". Maybe some of you have heard of it?
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Old Apr 16, 2004, 10:01 AM
Does anyone hear a cat?
headless's Avatar
Tallahassee, FL
Joined Sep 2003
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Actually, there are plenty of companies producing motors that put them together 'right for my plane'. Just not the one creating MicroTex motors, apparently.
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Old Apr 16, 2004, 10:45 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Back in one of the other MicRotex threads I posted pictures of mine and my initial impressions. I had seen pictures of the Rotex and assumed that the MicRotex would be a smaller version of it. In fact I'm dissapointed. The MicRotex seems to almost be from a different manufacturer. It has a somewhat wide airgap. As I rotate the bell, the air gap with the stator varries somewhat. I still haven't hooked either of these motors up. But, it has surprised me the difference in quality between them just from looking. I too got mine from Bob Breaux and don't want to stick him. My order was mostly based on my assumption that what appeared to be a quality Rotex would carry through into the MicRotex, which seems on the surface to have been a bad assumption.

gordon
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Old Apr 16, 2004, 10:53 AM
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United Kingdom, Bracknell
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Mechanically mine looked fine. Talking to someone else who got one yesterday though, his didn't run true ... he posted it back same day.
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