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Cooling crank drive / bottom bracket motor like Bafang BBS

Beiträge
9
Dear all,

Firstly, apologies for writing in English. I thoroughly enjoy reading contributions on this forum, but alas, have to rely on machine translation tools to understand.

I have a low power crank drive (a GSM motor - a clone of the Bafang BBS01) in my old but functional Alligt Alleweder A4. I usually run it at low power (no more than 8A, most of the time 3-4A). However, recently there have been a number of roadworks on the quiet roads and bicycle paths on my commute, which means that I have been having to 'swim with the traffic' on some relatively busy roads.

As a result I've been using the motor more to avoid holding up the traffic, and the motor has therefore been getting warm.

Does anyone have any experience with cooling such a motor in a velomobile, where there is less airflow?

I think that I saw a photo of somebody on this forum who had a BBS motor, and had attached a fan to it, but foolishly did not take a note of which thread it was. (I don't think it was on the pedelecs forum - thus I'm asking here first).

I would also like to add more cooling on the motor if I ever close the foot holes (which in turn will have to wait until I get shoes that allow cleats to be mounted in the middle of my foot - as my attempt to modify existing shoes resulted in shoes that cannot be easily clipped or unclipped!)

Many thanks for any help that you can offer,
Regards from Scotland,
Phil
 
Beiträge
5.834
Ort
8010 Graz
Liegerad
Staiger Airbike
Hi Phil,

it might sound a bit strange, but my first thought is using heat pipes for transporting heat from the motor to the aluminium body of the A4.
Perfect heat transport without control systems, electricity supply, etc...

The big question is: Can you find a supplier for suitable heat pipes?

Best regards, Harald
 
Beiträge
293
Ort
21514 Büchen
Velomobil
Alleweder A6
Liegerad
Flux S-900
Is the position of the crank axle movable? heat pipes would eliminate the possibility. Also flexi would destroy them quickly.


What kinds of electrical power do you have? With 12V you can run any normal PC fan. (Noctua use very little power and are high quality) with 6V you can use many (some start at around 7V, some at 5V. Noctua start at 5V, I think.) For 24V there are quite some for servers (Again Noctua has an "Industrial" line.)
(Sorry for the advertising, it´s just what I know to be good)
Other Voltages can be transformed.

Does it have any flat metal surfaces with space around? Could weld / solder / thermal glue / otherwise mount with thermal paste any heatsink.
Extreme: Heat exchanger for water cooling, other side being radiators or heat exchangers on the outer body (some low place without sun) - would need power for a pump again. Similar to the heat pipe idea, but flexible.
 
Beiträge
510
Ort
Saint Jean de Luz, Basque Country
Trike
Azub T-Tris 26
Hello another GSM user.

I thought about this a lot, I was going to mount my GSM on the trike with a nose and came to the conclusion that you need a hole at the point of the nose (Stagnation point) with a pipe, say 10 cm diameter, running back to your GSM. This won't cost much in aerodynamics and your GSM will be even better cooled than on the bottom bracket of an upright where it never gets hot.
 
Beiträge
1.424
Ort
Zürich
Velomobil
Sonstiges
you run it rather low power and it runs hot?
Must be defective or you pedal a very slow cadence. These motors at a good rpm have over 85% efficiency, 10A / 36Volt makes 360Watts so heat would be around 36Watts which is not much - given A4 has large foot holes and generous man hole. The efficiency sweet spot for a Bafang type motor might be above 50rpm and below 75rpm on the pedals. Unless you pedal very slow plus give it full throttle, that motor should not overheat. I am using a Tongsheng TSDZ2 and it never gets even warm, so I did not even install a heat sensor and I don't miss it. The TSDZ is not better than BBS thermo wise.
Plus I believe ventilators and else will not be very effective, as you will not be able to cool the motor coils but only the motor casing. A thermal sensor on the coils would be a more effective protection (if necessary), but I'd say stay under 12Amps and pedal always over 60rpm should do fine.
 
Beiträge
510
Ort
Saint Jean de Luz, Basque Country
Trike
Azub T-Tris 26
The GSM is a 90 rpm motor (87 rpm to be precise) I had problems with back EMF because I pedal at about 95 rpm (I know...) so I run it with a 44 volt battery and a 15 Amp external controller. Those 660 Watts have never been a problem for me because I use the external controller version. I have never noticed it getting too warm to touch.
 
Beiträge
9
Thanks all for the helpful comments.

To clarify, in normal use the motor doesn't get hot - it has only started happening when I've been using higher power settings (12-15A) when on busy roads. I run it with a 48V battery & external controller as I also had issues with the motor speed - now have 127mm cranks to fit my large feet into the Alleweder nose, so I tend to pedal between 80-110 rpm (faster on the hills, slower on the flats).

I like the ideas of passive cooling, but agree that heat pipes might well not last - the roads are in bad condition around here - but will investigate cutting a hole in the nose at the stagnation point, then running a pipe back to the motor.

Thanks all,
Phil
 
Beiträge
1.424
Ort
Zürich
Velomobil
Sonstiges
does that motor have some kind of casing around the motor? You might take that casing off so air can directly access the motor instead of cooling the casing only. In the AW4, the motor is well protected from rain and fingers. (the TSDZ motor could run without it's motor casing in a Velomobile but it does not look very nice)
Or take the motor cover off, drill many holes into it, and put it back on.
 
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Beiträge
9
Another good idea - the motor does have a metal cover around the motor - normally this would also house the controller (like the Bafang BBS) but I run the motor with an external controller anyway. Drilling holes for extra cooling does seem like a plan.

Thanks again
 
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