Dani's mid drive (GNG motor) - CAD heavy pics!

I'm still wondering if there isn't a motor out there with half the kV value, so the small pulley can be a bit larger. And perhaps a reduction in the size of the larger too.

Or if using #25 chain in that ratio on the primary side then things are quieter because of the lower meshing frequency, or a cover is easily made if the large cog diameter is eliminated.

We (ES users) found the bigblock and then set about designing around that, then discovered the half kV BHT one after the fact...
 
Samd said:
I'm still wondering if there isn't a motor out there with half the kV value, so the small pulley can be a bit larger. And perhaps a reduction in the size of the larger too.

We (ES users) found the bigblock and then set about designing around that, then discovered the half kV BHT one after the fact...
Click to expand...
You can always run a motor at a slower speed - just reduce the voltage..... Obviously, the power reduces proportionately. Without reference to the motor's phase resistance, the velocity constant (Kv) doesn't tell you anything about its abilities.....
 
Miles said:
Obviously, the power reduces proportionately.
Click to expand...

We're chasing ~3000W and ~150Nm for a known construction. The bigblock exceeds it.
The standard unit is capable of murdering rear ends at that point, and we know the standard unit is too noisy, with a primary side is too large to readily enclose.

I'm unsure of why you'd restate the obvious.
 
Samd said:
I'm unsure of why you'd restate the obvious.
Click to expand...
Because you said "I'm still wondering if there isn't a motor out there with half the kV value, so the small pulley can be a bit larger". It may be obvious to you but it sure isn't to a lot of people here. By the way kV stands for kilovolts :)
 
I shall atone for my mixed-truncation sins tonight by sacrificing a beer in your name.
All the while pondering the hilarity of needing to dumb down some things for some readers whilst being a precise pedant for the other :roll:
 
something going on here :D

At this stage I need to reconsider some things, before this becomes effortless.

I want 2000W. So the small GNG motor provides 48V x 40A = 1920W. Close enough. The RPM should be 3200 something, under load maybe 3000 (hill climbing) ?
Also I want torque badly. I don't aim for highspeed, not gonna race this thing. It's for offroad use and for fun.

So in case I want to be able to pedal while using the motor rpm should go down to 80 (to 100) rpm on the crank. 3000/80 = 37,5. 3000/100 = 30. Two stage reduction of 5 each gives me 5*5 = 25. Whew, I knew that before, but I was hoping it would not be dramatic. Maybe I need to part with the idea of padeling and go for less reduction.

To go directly from the motorshaft to the rearwheel sounds nice at first. Whats the reduction I need? Diameter of my backwheel: 61cm. Diameter of the pulley: 2,865cm. 2,865*30 = 86cm. Too much. If I could manage to make a wheel the size of 60cm thats only a reduction of 21.

Regarding chain: I can't have a driver sprocket thats any smaller than those small 28,65mm timing pulleys. So I think this idea is dead.

Regarding voltage: I can't go down in Voltage, because I think 40A is the best this can handle. Also controller get a lot more expensive at this point, you need thicker cables etc.. and I think it's not safe to run this motor with any more current.

So whats left? One reasone I decided to use the GNG motor was because it was really cheap. By the time I found out about taobao agents and high delivery costs I changed my mind. It's not that cheap anymore (~100$ + taxes). Maybe I should consider something else (but I don't know any good other motor) except the bigblock.

So regarding the big block: Will I get half the rpm for the same setup? 48V, 40A max. If so that would be great. I still don't like to add a 5kg motor to my bike. Doesn't feel right.

Last question: I was thinking if 50% of the rpm will get me the torque I was hoping for. So if I end up having a bad reduction of only 1:20, which gives me 150rpm at the crank, how much of a difference would it make? I know, best efficiency is achieved on 3200 rpm. Any data sheets?
 
How about using the LH side of the crankset as a jackshaft and have a 2 stage reduction to the wheel? You could use a Token freewheel (sans pawls) on a RH trials crank.
 
Miles said:
How about using the LH side of the crankset as a jackshaft and have a 2 stage reduction to the wheel? You could use a Token freewheel (sans pawls) on a RH trials crank.
Click to expand...

That sounds good. I'd love to get rid off the chain. So noisy, very nasty. Belt drive <3.

If I chose a 30cm pulley on the rear that would give me a reduction of 10.5. Now I'd only need 1:3 for the primary reduction. So a 9cm diameter pulley would do the job (instead of the big ~14,3cm wheel). Now we're talking! Yes, that makes much of a difference to me. This looks way better. I save some components. No noise on the chain, no load on my bycicle gears (which are btw lightweight shimano something uber-cool but not-so-2000W-approved).
Also a 30cm rear sprocket would look damn cool, imho.

Okay! Yout got me thinking. I would still need a 25mm wide beltdrive on the primary, can't go down to 15mm, I think. But I could use a 15mm wide belt for the secondary drive. In case of beltwear: I have two to three times the length of a belt now compared to a GNG/LR kit, which means 2-3 times less belt wear. If 15mm should not satisfy me I can easily upgrade to 25mm if I use lasercut layers like I was going for the 90T wheel. So much to reconsider, so little time.

Thanks guys! Thansk Miles :)
 
Decide how much torque you need: http://www.endless-sphere.com/forums/viewtopic.php?p=312555#p312555

Download the ContiTech calculator: http://www.contitech.de/pages/produkte/antriebsriemen/antrieb-industrie/contitech-suite_en.html
 
Miles said:
Decide how much torque you need: http://www.endless-sphere.com/forums/viewtopic.php?p=312555#p312555

Download the ContiTech calculator: http://www.contitech.de/pages/produkte/antriebsriemen/antrieb-industrie/contitech-suite_en.html
Click to expand...

As much as a bike can handle :twisted:

I'll have a look at this later today, need to take a written exam :?

Thanks again, this is very helpful
 
Hi Dani

Look up the crossbreak setup. There are more builds and pictures than I can find. some http://endless-sphere.com/forums/viewtopic.php?f=28&t=58866 Motor would power a shared jack shaft. The crank also inputs to the jack. The jack shaft then takes either /both inputs and powers the rear cassette. This frees you to do what your looking for better than trying to step down rpms' more than needed. You can choose any crank you wish this way also.
 
speedmd said:
Hi Dani

Look up the crossbreak setup. There are more builds and pictures than I can find. some http://endless-sphere.com/forums/viewtopic.php?f=28&t=58866 Motor would power a shared jack shaft. The crank also inputs to the jack. The jack shaft then takes either /both inputs and powers the rear cassette. This frees you to do what your looking for better than trying to step down rpms' more than needed. You can choose any crank you wish this way also.
Click to expand...
I looked for the crossbreak setup, I think I found what said. It's a good setup, though it limits me in chosing gears. But I can live with that.

If I would use a small gearbox like this (with only 1 gear), this could save some space and belts and .. well, I'll stick to the two stage beltdrive for now.
p4pb10022944.jpg
 
Miles said:
How about using the LH side of the crankset as a jackshaft and have a 2 stage reduction to the wheel? You could use a Token freewheel (sans pawls) on a RH trials crank.
Click to expand...
Couldn't the freewheel body be screwed directly onto left BB cup, instead of (and also functioning as) lockring for the motor carrier?
If the square taper BB is used, offcourse.
Or doesn't it work that way?
 
silence said:
Couldn't the freewheel body be screwed directly onto left BB cup, instead of (and also functioning as) lockring for the motor carrier?
Click to expand...
That's probably a better idea. There's always a bit of eccentricity between the axle mount and the freewheel mount on the trials cranks.
 
Miles said:
Dani,

You're ok with splitting the dropout for belt access?
Click to expand...

I thought about it and I still don't know. This will be compact, but it will take space in the frame triangel, where I wanted my batteries. Next problem is to get the belt from the triangle to the rear without interfering with the frame itself. A full suspension bike will be easier as my hardtail. If I put the whole thing in front of the crank, like GNG/LR, I'll have space problems with the crank and belt. It seems to me I should go back to my first idea and continue.
 
You asked about the big block. There is two versions, one at the half KV rating of the other.

Adam Mercier uses the slower one direct drive on his LMX at six kilowatts. Albeit sitting on the swing arm.
But the big block motor is not needed here for your 2 kilowatts. Extra weight not required.

What is interesting is watching whitehawk keep up with Adam on his three kilowatt GNG with only the controller modded. Damned noisy primary though.
http://youtu.be/9uAyFw684H0


So maybe all that is needed here is a better primary inside a Bosch style case. Which is the direction I am taking. If I can get a slower wind motor inside the smaller GNG can, I can make the primary chain wheel smaller and make the casing compact.
 
Hi Dani --

Just wondering if you were finally able to independently OEM source the GNG / L-R motor. Seeing how I need to improve my machining skills and I want to do all the cool (and necessary) mods to the motor bearings and spindle, I figure I will need to destroy at least one before I get it right.
 
Hey Dani,
there is the BHT which is the big block with half kV.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=57483

But I do not think the extra weight of the big block is needed if the normal GNG size can deliver 3kW anyway. It is the rest of the drivetrain that fails with poor brackets and adjustment etc.

I would like to try one of these. If the kV was half the GNG, I would make the primary side much smaller. No output shaft. Might make a nice project then!
http://www.aliexpress.com/store/product/BM1418HQF-750w-Dc-48v-60V-brushless-motor-electric-bicycle-motor-BLDC-whitout-differential-gear/232124_1611991724.html
 
hi,

Does anyone have a clue where to order the small (original) gng motor in small quantities 2-4 pieces?
i contacted the Honglida manufacturer, but they seem to be not interested , cause they do not respond to my mails.

greets

Gernot
 
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