GNG 450 brushless Mid Drive - Primary Drive Modifications

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Cyclebutt   100 W

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GNG 450 brushless Mid Drive - Primary Drive Modifications

Post by Cyclebutt » Jan 04 2013 1:16pm

Many of us are invested in the GNG 450 watt, brushless mid drive kit. Most of us believe mid drive is the future of eBikes. This low cost kit has created quite a stir and proves that a low cost mid drive is possible. However, one common complaint is the Primary belt drive. My own stock kit shows significant belt wear after only 170 miles of use. Overvolting has resulted in belt failures occurring in minutes. I've found many of you have made chain drive modifications with some success and would ask that you share your experiences here. Please include photos.

What method did you use for removing the pulleys?

What sprocket combination did you use?

What size chain did you use (and why), proven quiet and reliable?

What was your solution for the idler?

OR

Did you keep the belt, change to another belt, and/or use adjustable sheets?

AND


How long/many miles, has your modification been tested?



Please provide links and page numbers where you previously provided or saw this information.

Thanks to all contributors of Endless-sphere, ride on!


As of Jan 28th, 2013, the following link has proven to be the most popular chain drive modification. This is a step-by-step tutorial contributed
by Denisesewa:
http://endless-sphere.com/forums/viewto ... 30#p692904
Last edited by Cyclebutt on Jan 28 2013 6:40pm, edited 5 times in total.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by spinningmagnets » Jan 04 2013 7:55pm

The 100-page GNG thread:
http://endless-sphere.com/forums/viewto ... 28&t=42785

GNG upgrade mods index thread:
http://endless-sphere.com/forums/viewto ... 39#p695839

Denisesewa, #25 chain, 65T/12T from TNC-Scooters
http://endless-sphere.com/forums/viewto ... 95#p674897
Image
Last edited by spinningmagnets on Feb 21 2013 11:17am, edited 2 times in total.


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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by spinningmagnets » Jan 04 2013 8:11pm


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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by spinningmagnets » Jan 04 2013 8:19pm

Timbuck, He hadn't posted the chain type and tooth-counts, have PM'd him, will post when he responds. (I suspect it is #420 industrial chain / also for moped chain, but I have no evidence yet), looks like 55T / 12T

http://endless-sphere.com/forums/viewto ... 75#p652564
Image
Last edited by spinningmagnets on Jan 26 2013 9:38pm, edited 3 times in total.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 07 2013 10:18pm

Thanks heaps, spinningmagnets! So far, I like the looks of the 65-12 with a #25 chain. Someone had a great idea on an idler that was mounted to the motor face plate, adjustment was with rotational slots. Do you remember where that was? I like the idlers that give the most drive tooth engagement. While the #25 chain link spacing looks good, that 12 tooth drive sprocket needs all the engagement it can get. If you happen to find the revolving adjustable idler someone came up with, please post it here, looks promising. Thanks again.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by spinningmagnets » Jan 07 2013 10:22pm

From "richard purchon", I felt it was a clever solution. Since the holding bolts are inside slots, the rotating base-ring could still have a spring attached to it if you wanted.
http://endless-sphere.com/forums/viewto ... 55#p677505
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Image

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 07 2013 10:39pm

I like this idler for the chain drive. I'm thinking It would need to be adjusted pretty tightly, a spring load would have to be hefty, don't you think?
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richard purchon   10 mW

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by richard purchon » Jan 08 2013 4:29pm

the belt is tensioned by rotating the the disk by hand.and tightening the 2 nuts up, no screw drivers used.so its not tight.note its a 460mm long belt.running on 12s cells.only had chance to use 3 times apx 15 miles and its fine.
richard

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by spinningmagnets » Jan 08 2013 7:58pm

Thanks for posting richard, I think your tensioner wheel is probably the best compromise between having "some" wrap on the belt to prevent skipping, and not having so much (like the stock tensioner) that it sucks a lot of watts just to run. Good to know the length of belt that works on this set-up. For the stock 1,000W level of power, your mod is what I would recommend.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 10 2013 4:17pm

100_2044.jpg
Belt wear after 170 miles, most of which was street.
100_2044.jpg (83.45 KiB) Viewed 2197 times
This is what prompted me to start this thread. If you can make it out, the belt is walking to one side, fraying shows on both.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 10 2013 4:26pm

richard purchon wrote:the belt is tensioned by rotating the the disk by hand.and tightening the 2 nuts up, no screw drivers used.so its not tight.note its a 460mm long belt.running on 12s cells.only had chance to use 3 times apx 15 miles and its fine.
richard
Richard, do you have the belt part number, saw it somewhere? I would be willing to try this before switching everything to chain drive. Although chain drive would surely give the longest life, I really don't want to re-engineer the entire primary. Thanks for posting, guys!
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richard purchon   10 mW

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by richard purchon » Jan 10 2013 6:33pm

HTD5-0460-15


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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 11 2013 1:25pm

Denisesewa wrote:Thread on how I did my primary conversion >> http://endless-sphere.com/forums/viewto ... 19#p686519
When you trimmed off the outer edge of the large pulley, what method did you use?
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Denisesewa » Jan 11 2013 1:54pm

Cyclebutt wrote:
Denisesewa wrote:Thread on how I did my primary conversion >> http://endless-sphere.com/forums/viewto ... 19#p686519
When you trimmed off the outer edge of the large pulley, what method did you use?
I used an angle grinder with a cutoff disc and then did a little draw filing.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 11 2013 4:45pm

http://endless-sphere.com/forums/viewto ... &start=570

Page 39 of the GNG 450 brushless $400, has some good information on removing/replacing the primary drive.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 12 2013 11:05am

Thanks, crossbreak. Hey, looks like LightningRods invented a way to stay with a belt primary! Please keep us posted. This change should help with belt longevity. Nice work!

Link to adjustable plates to improve primary drive performance/life.

http://endless-sphere.com/forums/viewto ... start=1035
Last edited by Cyclebutt on Jan 28 2013 6:11pm, edited 1 time in total.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by LightningRods » Jan 12 2013 9:51pm

I've been heading off in a somewhat different direction than the rest of the group. Having seen Matt Schumacher's gorgeous CNC drives running 6kW AstroFlight motors through belt drives, I want to try to hold on to the quiet, clean and supposedly low maintenance carbon belt drive. I read through the Gates Industries handbook on the care and feeding of these belts, and found that GNG had violated most of the "DO NOT" rules in the book. Most importantly GNG had not provided a proper way to tension the belt. Not only does the stock tensioner not provide enough tension, it bends the belt in a way it was not designed to bend. I decided to design a proper slide tensioner that would give the belt a chance to work properly.

My original design concept drawing:

Image

A 3D model rendering to help me visualize how it would all go together:

Image

And here is how the finished product came back from the laser cutter:

Image

Image

Image

Image

Image

As it turns out there are other benefits to my design. With 3/4" longer sheets it's now possible to fit larger pulleys or sprockets to get more primary reduction and allow a better pedaling cadence. For the people who have already converted their drive over to chain you can also tension your chain with the sheets and toss the noisy and power robbing tensioner. I've seen some clever idler tensioner designs here, but I still believe that the best tensioner is no tensioner.

I'm currently selling these sheets to the E-S Forum at cost, $20 US. This includes a new section of 3/8" steel tube to cut for your narrower spacers (the added inside sheets shorten the spacers by about .2"). On Monday Jan 14th I'm placing an order with the laser cutter. If you want a set, this is a good time. PM me and I'll add you to the list.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by spinningmagnets » Jan 12 2013 10:01pm

There are several benefits to this upgraded bracket. The stock bracket is made from .098-inch (2.5mm) low-grade steel, and the new ones here are .104-inch (12-Ga), and made from a better steel. It may not sound like much, but you can't beat the improvement at this price, especially adding the benefits listed above...

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by crossbreak » Jan 13 2013 2:18am

it's always nice to see how ES improves chinese stuff :D Add an chain drive to your kit and sell it for $100 on ebay, you'll find customers ;)

No seriously, I proposed to build such sheets earlier, but the main factor that keeps me from buying is the tiny belt sprocket. A chain solves all issues IMO in a much better way.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by LightningRods » Jan 13 2013 3:46pm

crossbreak wrote: I proposed to build such sheets earlier, but the main factor that keeps me from buying is the tiny belt sprocket. A chain solves all issues IMO in a much better way.
I'm going to start out trying to keep the belt drive. I'll admit in advance that I may not be able to. The stock pulley is too small in diameter and possibly too narrow at 15mm. I think it may work fine at 1 kW which is where I'm going to start out. There is another issue with the stock drive pulley, and I don't know that I've ever seen this mentioned on E-S. The way that it is machined creates a sharp edge on the cog profile. If you compare the GNG sprocket to a more typical profile you can see that the way it was machined creates a sharp cutting edge (red arrow).

Image

I think this may be a big factor in premature belt wear on the standard drive.

So to sum up the primary belt drive on the stock GNG:

No provision for proper tensioning
Provided tensioner bends belt backwards damaging carbon support layer
Drive sprocket too small a diameter
Drive sprocket has atypical profile with sharp edges
Driven sprocket has excessive runout causing belt tension to fluctuate
Mild steel sheets may be bent in transit causing improper alignment of belt
Entire belt system may be too narrow (15mm vs. 20mm)

If I continue to have belt problems after correcting for belt tension I'm going to start solving for the other issues. If it still doesn't work I'll admit that carbon belts suck and joing the rest of the gang with a chain primary.
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spinningmagnets   100 GW

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by spinningmagnets » Jan 13 2013 4:31pm

Stock GNG belt is HTD-5mm pitch, 15mm wide and 475mm long with 95 teeth. Pulleys are 80T-14T (ratio 5.7:1).

I am of the opinion that at the stock power level, the 14T drive pulley is an acceptable diameter, especially with runout removed from the large pulley and the new side-plates allowing proper belt tension. If someone were to go to the extra expense of a larger than 80T pulley to allow a better reduction, it couldn't hurt to buy a slightly wider belt/pulley set to improve the drive a little more.

If you want to replace the small pulley to remove the sharpness of the stock teeth, lets find out what the available options are (belt/pulley widths, tooth counts, shaft diameters).

edit: Matt (recumpense) uses 20mm and 25mm wide belts.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by LightningRods » Jan 13 2013 6:50pm

spinningmagnets wrote:Stock GNG belt is HTD-5mm pitch, 15mm wide and 475mm long with 95 teeth. Pulleys are 80T-14T (ratio 5.7:1).

I am of the opinion that at the stock power level, the 14T drive pulley is an acceptable diameter, especially with runout removed from the large pulley and the new side-plates allowing proper belt tension. If someone were to go to the extra expense of a larger than 80T pulley to allow a better reduction, it couldn't hurt to buy a slightly wider belt/pulley set to improve the drive a little more.

If you want to replace the small pulley to remove the sharpness of the stock teeth, lets find out what the available options are (belt/pulley widths, tooth counts, shaft diameters).

edit: Matt (recumpense) uses 20mm and 25mm wide belts.
Personally, I hope the stock setup works fine once the tension is correct. For sure that is the biggest problem. If I have to go to different sprockets I think I'll go wider if not larger diameter on the 14T drive sprocket. At about 6:1 every tooth on the drive requires 6 on the driven just to keep the reduction the same. I'd rather gear the reduction down a bit with 14T. Maybe 20mm wide with 14T/80T.

Matt's drives are awesome. Once I figure out what I'm doing with all of this e-tech I'll buy one of his DaVinci drives just for the mechanical beauty of it. For now the GNG is my poor man's DaVinci with Astro 3220.
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