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Tacon Bigfoot 160 Motor Malfunction

Old 09-02-2022, 05:02 PM
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GorillaToast
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Default Tacon Bigfoot 160 Motor Malfunction

I have a Tacon Big foot 160 that was working fine for about a year, then suddenly it began abruptly (and I mean abruptly!) stopped spinning after about 30 sec run time at 1/3 throttle. It does this regardless of whether it is propped or not. I've tried it with 2 different esc's, a CC 120HV and a Jeti Spin 99 Opto. Both escs are functioning fine with other motors. When it stops, the CC 120 emits 3 beeps which acording to the Tacon manual indicates a "motor anomaly". No further explanation of what a motor anomaly is.

I have searched all the major rc forums and a general google search for problems with Tacon motors, but came up empty.

Has anyone out there had this sort of problem with their Tacon motor, and if so, where you able to salvage the motor?

Thanks,
Bill
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Old 09-02-2022, 08:22 PM
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ron_van_sommeren
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Does it always take about half a minute before the problem occurs?
Have you tried different batteries?
Current and battery voltage (drop) measured?
.
.

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Old 09-03-2022, 06:31 PM
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Thanks Ron for the wealth of information included in your reply.

1. yes, always about 30 sec
2. yes
3. no, I haven't. I'll try that next
4. factory mounting screws on backplate. Plate mounted to 2" standoffs
5. I've resoldered the bullet connectors on the motor twice. Have not opened up the motor to check the connectors on the motor.
6. no stuttering on start. just stops at about 1/3 throttle after about 30 sec.

The rest is probably a bit over my technical skills and/or not worth the effort for a $99 dollar motor. The only reason I'd like to get it working is because those motors are out of stock everywhere at the moment.

Thanks again.
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Old 09-03-2022, 10:41 PM
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Got it working!

I was doing the drytesting with a drill and the red motor lead fell off in my hand.

Oops...

As soon as I charge a couple of 5s batteries, I'll put it on the wattmeter and see how it performs.
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Old 09-04-2022, 03:53 AM
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ron_van_sommeren
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For resoldering with a fresh 'stretch' of wire you have to remove the insulation coating/lacquer/resin. Tough stuff.
With most motors the motor wires are extensions of the windig wires.

Can you post a picture(s)?
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Old 09-04-2022, 09:23 PM
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I understand now that I may not have made the best splice without removing the lacquer/resin from the stub of motor wire I spliced onto. But the motor is running now, although it is more than 1K rpm lower than e-calc show it shoud be.

With an 18 x 10 PJN Xoar wood prop on 10s I'm supposed to be getting ~7600rpm/ 70a/ and 2436 w. However I'm only getting ~6200 / @ 36a/ 1200w.

Could a less than stellar soldering job be causing the reduction in power?
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Old 09-06-2022, 11:39 PM
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Not caused by higher resistance due to your soldering.
For such a difference in RPM to occur, you'd have to lose/'burn' a lot of voltage&power just in that small soldering spot.
Extremely rough calculation, assuming Kv=200rpm/volt.
A difference of 1000rpm would mean voltage loss of 5volt.
Combining that with you measured current of 36A your soldering spot(s) would have to burn 5V×36A=180watt (power_losses = voltage_losses × current).
Even when evenly divided over three connectors, that would give 60watt to burn per connector. That's about the power of a decent soldering iron.

The connector(s) would get very hot and probably desolder very quickly.
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Old 09-07-2022, 02:37 AM
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And I shot the connectors at WOT and they were at 21*C, close to ambient temp for my workshop.

Someone on RC Groups said I should "Buzz out" the windings to see if I am only energizing 2 of the 3 windings. I don't know how to do that. I did put an OHMMeter from 1-2, 1-3, 2-3 and all beeped continually indicating continuity even when moving the motor wires. Is this what he meant by "buzz out"?

I also tried a different comparable esc and got similar wattmeter #s.
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Old 09-07-2022, 05:24 AM
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That's buzzing out, buzzing sound means continuity, but there's a catch.

The coils of a brushless motor can be terminated/configured in ∆/deltat/triangle/ or in Y/wye/star.
In triangle, a discontinuity in one of the phases, will give result in discontinuity in 2 of the 3 measurements.
In delta, you will not measure a discontinuity, there will always be an electrical path.
For measurements on a motor in delta you need an (expensive) milli-ohm meter that can tell the difference between the paths.

So, we need to know, is your motor configured in delta or star?
A late question, not relevant for 'buzzing', what is its velocity konstant Kv?

One coil per phase
Simplest, but our motors usually have 3, 4 or more coils per phase, as diagrammed further down.


Three coils per phase


No four coils per phase pictures, but you get the picture.

9N 12(or 6)P motor

Last edited by ron_van_sommeren; 09-08-2022 at 04:07 PM.
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Old 09-07-2022, 01:23 PM
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Originally Posted by ron_van_sommeren View Post

So, we need to know, is your motor configured in delta or star?
A late question, not relevant for 'buzzing', what is its velocity konstant Kv?
Not being an EE, how would I know if it's delta or star?

The Kv is 245.
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Old 09-08-2022, 04:50 PM
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Originally Posted by GorillaToast View Post
... The Kv is 245rpm/volt.
My earlier quick'n dirty estimation Kv=200rpm/volt wasn't that far off

However, for current and power drawn calculations the resulting difference would be massive, hence my question about its value.
Current and power drawn are proportional to Kv³
Going from 200 to 245rpm/volt would result in increase by factor (245/200)³=1.8 in current and power, 80% more.
Some expensive realistic and some extremely silly examples, hopefully instructive as well.


Originally Posted by GorillaToast View Post
Not being an EE, how would I know if it's delta or star? ...
Delta or star configuration should be in the specifications/instructions.


Although the user does not need to know it, deltastar is already incorporated in Kv.
Two almost identical motors, one with his three phases/strings connected in delta, the other in star:
Kv_delta= √3 Kv_star

In industry, motors can start up in star, low Kv and rpm, to keep startup current down.
Once constant rpm has been achieved the motor can switch to delta, higher Kv and rpm, for more speed.


The Lehner Series 30 motor$$$ have a user selectable configuration.
Both ends of each of the three phases/strings are accessible.
In the pictures below unselected, delta and star respectively.169
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Old 09-08-2022, 06:45 PM
  #12  
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A bit off topic, but ...
Important: note that Kv says nothing about motor's max. power.
Both the tiny motor in your toothbrush and the motor in a 330kmh/205mph ICE train (500kW) can have same velocity_konstant_Kv.
Kv in combination with voltage sets desired rpm.
Max.current and max.power determine whether the motor can run at that rpm and load (current and torque are proportional) without going up in smoke.

Ok, I know, I'm banging on, back to our regular programming

Siemens ICE 3 train at Amsterdam Central (Nederland), this one run by Deutsche Bahn (German rail).

Last edited by ron_van_sommeren; 09-08-2022 at 07:05 PM.
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