GNG, 1000W 48V BB-drive, $400

Denisesewa · Dec 9, 2012

christerljung said:
We got the same weather here in Sweden.
I did the a similar process with my GNG. Take it really slow when getting closer to 10mm, it goes away much faster in the end. Mine was suddenly 9.8
The sprocket i bought was with set screws, mounted with no problem and has been sitting tight so far. Like this:

Did you put dimples in the shaft for the set screws? I just finished turning the shaft and am very happy, nice hand press fit with no appriciable runout, less than 2 hours work. you are right that the shaft turns very fast at the end ,I almost went too far as well.

Click the pic for vid.

Denisesewa · Dec 9, 2012

BZwindtalker hit it right, 65- 12 T #25 works out to give a good chain length, I bought 11t, 12t and 13t drivers and the 12T looks like this with 6 tooth engagement, should be perfect.

I'll make a roller tensioner to take up chain stretch and any runout I might get when mounting the sprocket to the pulley, hopefully there wont be much.

crossbreak · Dec 9, 2012

nice to see that mounting a sprocket seems that simple

thanks for sharing this. I'd like to use the ES Drive calculator (http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=6892&start=150#p545943)to get some simulation data from this. BUT i need at least the phase resistance of this motor to get some usable results. Could someone plz measure it? We should also write at least a short wiki page with some compressed info. I will write one if one can post the phase resistance

Denisesewa · Dec 9, 2012

crossbreak said:
nice to see that mounting a sprocket seems that simple thanks for sharing this. I'd like to use the ES Drive calculator (http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=6892&start=150#p545943)to get some simulation data from this. BUT i need at least the phase resistance of this motor to get some usable results. Could someone plz measure it? We should also write at least a short wiki page with some compressed info. I will write one if one can post the phase resistance

Well that is going to have to be someone else , I know almost nothing about the electronics involved in the motor or controller, I'd like to learn but its like teaching an old dog new tricks, nothing is written in words I can understand.

spinningmagnets · Dec 9, 2012

65T - 12T, #25 chain

bzhwindtalker is currently trying out his primary drive with #219 chain using 60T - 11T sprockets, 14S LiPo (49V-58V) on a 24-inch rear wheel.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=44623&start=45#p674387

Also Denisesewa was right about needing a 1/2 link for the #25 mod. The chain is too loose without it.

http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=795#p674897

Denisesewa · Dec 9, 2012

spinningmagnets said:
65T - 12T, #25 chain

Click to expand...

bzhwindtalker is currently trying out his primary drive with #219 chain using 60T - 11T sprockets, 14S LiPo (49V-58V) on a 24-inch rear wheel.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=44623&start=45#p674387

Yes I know, but he did mention the #25 chain combo on page 51. when I showed a picture of the sprocket I ordered.
I also run a 24 wheel and 14s 2p lipo

spinningmagnets · Dec 9, 2012

Thanks! I was just listing the working options for the readers, ones that performed well so all the choices were posted near each other.

I appreciate the pics you posted, and I am looking forward to the final results.

christerljung · Dec 10, 2012

@denizewa: I made one little dimple with a drill in the motorshaft, which one of the setscrews could dig into. Since i run this on 72v with hard accelleration and high offroad load it seem to work very well.

@crossbreak: Is it plain resistance without power and no rotation? I can do that later today.

crossbreak · Dec 10, 2012

Great! I made a short vid to show how to measure the phase resistance. You dont need a lab PSU, just one that outputs 3Volts max and many amps (not too many). One that outputs only 1Volt would be perfect.

Measure both current and voltage, phase resistance is voltage/amps. Vid: http://www.youtube.com/watch?v=HT-hEMGKXCo&feature=youtu.be

Guess the phase resistance is not less than 150 mOhms, so if you push in 3Volts you should see about 20amps. That is okay for this motor if you dont do it too long.

christerljung · Dec 10, 2012

Some facts to the wiki, of our beloved GNG:s

DC phase resistance @ 184.3 mV, 2.52 A:
73.134 milliohm

Stator thickness: 24.7mm
50 laminations
lamination thickness: 0.494mm

12 poles
copper wire diameter 0.7mm

magnet rotor
8 magnets
50 laminations
lamination thickness: 0.494mm

Inner bearing: 6201RS
Pulley bearing: 6203RS

crossbreak · Dec 10, 2012

thanks so much christerl! we have waited so long for someone to post this!

Maybe you have some pics from the inside now? i'm waiting keen to see some

You can access the new wiki page here: http://endless-sphere.com/w/index.php?title=EBike_Motors_Middrive

christerljung · Dec 10, 2012

The heart of the GNG, split up:

crossbreak · Dec 10, 2012

This is far beyond my expectation. Seems like this is a true 2kw motor, no doubt. I like the pic in which we can watch you test the magnets

Seem like it would like more speeeeeeeeeeeeeeeeeed!

Now we now why this one has 100Watts no load consumption

i'm waiting keen for miles next post here

christerljung · Dec 10, 2012

Indeed yes! :mrgreen:

I had to use help from some tools to manage pulling the rotor out of the stator because of the powerful magnets. :twisted:

Next i will put the shaft in the lathe and give it some precisionwork for the perfect pulley fit. Then try a 12/72 first gearing with 24S 88V nominal. And winter spike tyres.

Miles · Dec 10, 2012

Thanks for the pics Christer.

Please could you measure the magnet thickness? Thanks

christerljung · Dec 10, 2012

sure Miles, no problem:
Magnet thickness: 4.2 mm
Magnet size 24.5 X 24mm

crossbreak · Dec 10, 2012

ok, now while it's already open... whats the rotor dia

?

Miles · Dec 10, 2012

GNG motor data:

Weight?
12 slots 8 poles
Winding factor 0.866
Cogging: 24 step per rev.
Rm 73 milliohms (phase to phase)
Kv 67 rpm/V
Kt 0.143 Nm/A
Km 0.53 Nm/√W
Specific Km ?

Rotor OD ?
Stator OD ?
Stator ID ?
Stator thickness 25mm
Lamination thickness 0.5mm
Magnet thickness 4.2mm

circuit · Dec 10, 2012

crossbreak said:
Now we now why this one has 100Watts no load consumption i'm waiting keen for miles next post here

One difference I can see is it's rotor is made from lamination, not a solid peace.

BTW, anyone tried to peal off a nickel foil off a neo magnet and measure it's electrical conductivity? Maybe all the eddy current losses are not in magnets, but in rotor?

crossbreak · Dec 10, 2012

circuit said:
...Maybe all the eddy current losses are not in magnets, but in rotor?

the magnet path in the stator is much longer than the one in the rotor. If they use the same laminations, major eddy current loss occurs in the stator.

Edit: OK you think about the magnets... their section is tiny compared to the rest :? guess they have no big influence

Miles · Dec 10, 2012

http://www.ndfeb-info.com/characteristics.aspx

The laminations are just a constructional thing - see the magnet retaining method etc.

crossbreak · Dec 10, 2012

christerl, the GNG looks like it is made for 3000rpm. So there is n sense in using more than 20s lipo, should only get inefficient at higher speeds :?

christerljung · Dec 10, 2012

Yeah. Maybe thats something i allready feel, it kind of fades in accelleration at higher rmpm:s when run on 18S. Or is it just the different characteristics of an electric motor vs a combustion engine? The GNG has really got the bottom end grunt thats for sure, thats also the main reason for eating belts.
-Miles, ill be back tomrrow with more measurements.

crossbreak · Dec 10, 2012

the only reason i can see it eats belt is the tiny 14T sprocket. If it would was 18T there would be half the problem.

christerljung said:
... i allready feel, it kind of fades in accelleration at higher rmpm:s when run on 18S. Or is it just the different characteristics of an electric motor vs a combustion engine? ...

it depends on how your phase current is set and if you drive at pedal speeds or not - even if there is no recognizable eddy current braking (like engine brake, but it can not be really "felt" cause there are the freewheels in the drive). what batt and phase current have you set?

Miles · Dec 10, 2012

christerljung said:
-Miles, ill be back tomrrow with more measurements.

Great. Thanks for the magnet dimensions.

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