Installing a thermometer inside an Aotema brushless motor

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dogman dan   100 GW

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Installing a thermometer inside an Aotema brushless motor

Post by dogman dan » Mar 14 2009 8:49am

Living in the desert, and having an uphill ride home of 15 miles makes it easy for me to melt a motor. This summer I am using a cooler running Aotema (WE) brushed motor at 36v. It runs about 40 F cooler than the brushed hub, that is on the verge of overheating at all times. But I still want to know when I am flirting with a meltdown and when I am not, to better learn to ride cool. So I am installing a cheapie indoor outdoor thermometer sensor in my motor. A Bell product, I got it at wallmart for ten bucks. Look in the car accessories section. I took a pair of snips and cut off the plastic from the sensor, but I doubt it was really required.

This seemed like a good time for a tutorial on opening an Aotema brushless motor so it gets a bit heavy on the pics. It's the first peek inside for me on an aotema brushless.

There is a metal collar around the wires like a bushing, that I pulled out of the way first. It protects the wires from rotational rubbing, but looked to me like it could cut the wires when the cover is lifted.
bushing.jpg
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After removing all the hex nuts from the cover, I very gently tap a knife blade into the seam. It's easy to strip the inside of the hex nuts, since they a put it while the paint is still a bit green. sometimes a vise grip may be needed to get em started. But with this whole procedure, BE GENTLE. Everything is done very slowly and patiently, and in tiny increments.
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After this step, the hammer is put away, and any tapping in of screwdrivers or prybars is done with the handle of a screwdriver. Again, easy does it. Next is a thin screwdriver. Do not shove anything in very far, seriously, past a quarter inch and you are going to mash the windings inside! so it's just the very tips of all the tools.
thin screwdriver.jpg
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Slowly and patiently, work around the cover, getting in a bigger screwdriver, then another, till you have three in place. The idea is to genlty pry the cover off with even pressure all the way around. Of course a gear puller the right size works great, but at my local auto parts place, I haven't seen the perfect one yet. Most of em don't have jaws wide enough, and thin enough at the same time.
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By the time I got the third screwdriver in, I heard a pop and the cover came up a bit. Still not loose completely, I switched to a big flat bar. The flat bar is not for more leverage, it's just thicker and less awkward to pry with as the cover comes up. It might be possible to just wiggle the cover off by hand once it pops up a little, but I just use a thicker thing to pry. You never pry hard on any thing, and just tap in the screwdrivers with the handle of another driver. It's an easy pull, but you can bust stuff easy if you act like it's your car you are taking apart.
final pry.jpg
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And there you have it. the cover off. This aotema brushless motor was bought from High Tech Bikes, and in my opinion, it is very high quality looking inside. Its a 7 wire winding, so I guess it compares to a clyte 407. The motor is pretty happy in the 15-22 mph range at 36v. Looks to have lots of magnets, and they appear to be pretty wide. If they are just as long on the other side, they would be 35 mm wide.
Aotema brushless inside.jpg
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Now for the thermometer sensor. Two wires, it doesn't seem to care about polarity. My favorite epoxy is pc 11. Marine grade, it takes heat well, so that should do. Just a dab to mount the sensor on the inside and a zip tie to keep the wire from getting wild in there.
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sensor in the motor.jpg
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Replacing the cover is sort of the reverse of pulling it. Pay a lot of attention to the wires, and the collar goes in after the cover is in place. I gently tap the cover back on with a screwdriver handle.
tapping back the cover.jpg
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And finally, the sensor wires connected, I cut it about where the motor wire plug is, and the thermometer works, goody I didn't cut the wire. After I got the cover on, I realized, dooh, I could have put some shrink tube on it! pic in the next post, I'm too pic heavy on this one.

Now this summer, when I am riding up a looooong hill in 105 F, I'll know if my motor is running too hot. Anything over 140-150 F is getting to the damage zone in my opinion, if you ride for a full hour at a time like I do.

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dogman dan   100 GW

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Re: Installing a thermometer inside an Aotema brushless motor

Post by dogman dan » Mar 14 2009 8:54am

Here is the finished thermometer. Kinda cold in the house this morning, I'm not turning up the heat with solar heat coming in a few hours.
thermometer working.jpg

nathan_jones   100 mW

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Re: Installing a thermometer inside an Aotema brushless motor

Post by nathan_jones » Mar 14 2009 10:25am

good thinking nice idea. however living in wales, i have no change of sunshine or heat . :(

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fechter   100 GW

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Re: Installing a thermometer inside an Aotema brushless motor

Post by fechter » Mar 14 2009 10:39am

Nice job dogman.
I did something similar on my Puma motor (untested so far).

I would have suggested placing the temp sensor next to one of the hall sensors, since those are what fail when it gets too hot. The thermal conductivity of the stator frame should be good enough to be in the same ballpark though. Most hall sensors are rated for 125C.

I hope the maximum your thermometer can read is high enough.
"One test is worth a thousand opinions"

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ekingsting   100 mW

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Re: Installing a thermometer inside an Aotema brushless motor

Post by ekingsting » Mar 14 2009 11:54am

Thanks for the look inside. Can't wait to see results as it gets hot during the summer and its all hills around here. By the way the new Aotema brushless does not use hall sensors with supplied controller. Dogman, did you see any sensors?
48v 12ah tempest sla's, aotema brushless, 1980 king sting 1300 mi.
7 original Zappy's 12v 22ah 12mph/ 1 at 24v 10ah 20mph

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dogman dan   100 GW

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Re: Installing a thermometer inside an Aotema brushless motor

Post by dogman dan » Mar 14 2009 1:38pm

Nope no halls. Its a totally pedal first design, but the motor spins up fine as long as I roll it about one inch forward as I put on the trottle. It can start from a dead stop too, but will occasionally go bacwards one magnet, and then go forwards.

This thermometer over temps and stops reading at 150F, so if I see high temp on the readout I know it's time to stop. Somewhere around 150 is where magnet epoxy starts getting pretty soft. The issue isn't really so much a high temp, as riding say, another 30 minuites when at that high a temperature. Eventually the magnets start falling off if you are riding that hot. I can barely wait to see just what my normal operating temps are, but I need to wait till at least evening for the epoxy to set. The slower the set, the higher the temp epoxy can take I'm told.

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fechter   100 GW

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Re: Installing a thermometer inside an Aotema brushless motor

Post by fechter » Mar 14 2009 11:06pm

What kind of controller are you using?
"One test is worth a thousand opinions"

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dogman dan   100 GW

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Re: Installing a thermometer inside an Aotema brushless motor

Post by dogman dan » Mar 15 2009 6:25am

It's the high tech bikes aotema kit, Terry says it's a 22 amp controller. I believe it is the same thing as a WE kit, but I am not positive the same amp controller is used. Sensorless controller. It works great for my application, 23 mph cruise speed with a 36v ping, and me on a bike with upright posture. Climbs 10% fine, but bogs down on steeper hills. The only steeper than 10% hill on my route is short enough for me to just charge it and make it on momentum. After a year riding the WE bd36, it feels very torquey to me. I barely shift down at all anymore, and my high gear is 56-14.

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