GNG 450 brushless Mid Drive - Primary Drive Modifications

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Denisesewa   100 W

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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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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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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 14 2013 11:49am

I'm definitely "IN" with the adjustable sheets. However, I have a gut feeling that part of the reason the GNG primary has that "deep plunge" idler, is for teeth engagement. I seem to remember someone installed a smaller belt (same width) on the stock kit. This resulted in stripped teeth, thought to be caused by less engagement (or lack of an idler?). Anyone remember this, gotta link?

Anyhow, I see these sheets as the best "first step" because it allows us to be rid of that crazy stock idler, the likes of which I have never seen before. If I end up with a chain drive later, the adjustable sheets should make adaptation that much easier, anyway.

Edit: Oops! Just realized that the sharp edged (thanks, LightningRods) drive pulley could be the "teeth stripper" of the smaller belt conversion, hmm...
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by LightningRods » Jan 14 2013 12:38pm

The order for the first beta production run of adjustable sheets is at the CNC shop. I stuck my neck out and ordered 10 sets for the Forum to get a better price. Thanks to your support I sold all of those and had to order more. In addition to the sharing of valuable knowledge and experience this is another great thing about E-S. We can go in together and have custom parts made at prices that start to become reasonable. I'll be contacting everyone who placed an order to wrap up billing and shipping. Everything will go out this week.

If you've found this post late, as often happens, and want a set of adjustable plates for your Gen 1 GNG send me a PM and I'll see what I can do. The initial run is sold out as of 1/14/13.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by LightningRods » Jan 14 2013 12:44pm

Cyclebutt wrote:I'm definitely "IN" with the adjustable sheets. However, I have a gut feeling that part of the reason the GNG primary has that "deep plunge" idler, is for teeth engagement. I seem to remember someone installed a smaller belt (same width) on the stock kit. This resulted in stripped teeth, thought to be caused by less engagement (or lack of an idler?). Anyone remember this, gotta link?

Anyhow, I see these sheets as the best "first step" because it allows us to be rid of that crazy stock idler, the likes of which I have never seen before. If I end up with a chain drive later, the adjustable sheets should make adaptation that much easier, anyway.

Edit: Oops! Just realized that the sharp edged (thanks, LightningRods) drive pulley could be the "teeth stripper" of the smaller belt conversion, hmm...
IMO the sharp teeth on the small drive gear are a result of using a round nosed cutting bit on the cylinder of steel that the entire rotor spindle is machined from. They make longitudinal cuts and don't bother to radius the top of the cog (which engages the base of the belt cog). Easy, lazy, cheap production the way that much of the kit was made. At this point all we can do is keep going down the list of half-assery, correcting until we get acceptable results. I come from a background in hot rodding cars so I am used to making silk purses out of sow's ears. :D
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by justlooking » Jan 15 2013 7:43am

LightningRods wrote:
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.
just a thought, but what are the chances of useing a belt tensioner from a car timeing belt for the primary drive?? ok the bearing might have to be removed from the centre then a spacer made up ,, or the centre to be modded some how, but they are made so that they do not strip the belts ,, and the belts last for 10s of thoughsands of miles under a lot more stress than one of these kits could very give out ..

there is also the timing wheels on a car that could possibly be used as well for the larger wheel

here is a link to different types ,, its a thought to ponder on http://www.ebay.co.uk/sch/Vehicle-Parts ... ming+wheel

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Needmorespeed » Jan 15 2013 1:36pm

Needmorespeed wrote:
justforfun wrote:We also have got rid of the belt, in the UK mud this time of year was killing belts on average every 8 miles, if it gets wet and slips it snaps the belt.
We have changed to BS 04b chain and sprockets 12t on motor & 57t on the jackshaft. With this setup there is no need for a tensioner or different mounting plates :D but we did use a half link.

Link for chain and sprockets http://www.technobotsonline.com
Here's some pics to go with your post!
You'll have to excuse the muddy bike! It's been stupidly muddy recently :wink:
Now the snows arrived it might clean it up a bit :D
It's a great little mod, hope it holds up.
Both running over 60v nominal ,also running 48 tooth sprocket to good effect.
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Denisesewa » Jan 15 2013 2:00pm

So it appears the BS-04 chain is 6mm pitch which would be very close to the #25 chain I use which would be roughly 6.35mm , nice to know these sizes are close and seem to be holding up well on both sides of the pond.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by LightningRods » Jan 15 2013 6:43pm

I received an e-mail from an engineer at Gates Corp. that I have been communicating with about our belt problems. I sent him pictures of the small 14T drive pulley and also attached my diagram showing how the pulley teeth have a flat top with sharp edges. This was his response:

"The sprocket with the sharp edges is a definite no-no. It’s very likely a big part of the cause of how your belts look after the short run time that you mention."

He asked for some more information which I sent on to him. I'll share return information as I get it from Gates.

You trail riders have some very valid points in favor of chain drive. I've ridden both dirt and street motorcycles for years and they're very different. I'm building a street fighter out of a hardtail MB so I want clean and quiet. For off road you just want the thing to perform and get you home.

I expect that the stock drive pulley is junk and needs to be machined off no matter what. The only option is to keep a backpack full of drive belts with you. I'm going to talk to Christer about extracting the rotor spindle so that it can be properly turned down to 10 or 11 mm and a keyway machined in. The file technique is okay but it limits the choices on pulleys and sprockets.

Image
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 18 2013 12:04pm

[img]
100_2034 (2).jpg
Belt fraying after 170 miles
100_2034 (2).jpg (90.85 KiB) Viewed 1741 times
[/img]Here's another photo of the stock belt configuration after 170 miles. Only around 30 of these miles were trail. Can you see the edge fraying?

I'm going with adjustable sheets for now.

1) During installation I will rotate the motor power lead to a more "protected" clock position.
2) Run shorter belt with sheets in most closed position. Anyone have that part number? I'll look for it. test it..
a) In case belt's too short for easy installation, go back to original belt. test it...
3) Find a screw type idler for this configuration. It is my belief that a spring loaded idler is not appropriate for this type of belt, also not designed for serpentine use, other members have confirmed this. A spring type idler allows jerking motion which (IMHO) leads to premature belt failure. A screw type idler would allow enough slack in the belt line for easy belt change in the field, would allow perfect "FIXED" tension adjustment as well. test it...

I'm fairly confident these mods will at least quadruple the belt life. If it'll go three thousand miles, I'm satisfied. If not, I'll go with the chain mod. Adjustable sheets will still allow easier adjustment for chain drive choices. Besides, if I have to turn down (machine off) the drive pulley, a drive "sprocket" will replace it, I'll be finished with the attempted salvaging of the stock primary drive.

This bike is being built as a commuter with occasional off-road capability. Sort of a KLR (Kawasaki motorcyce) of bicycles.

So this is my "IF-THEN" plan. Anyone remember the part number for the shorter belt and any suggestions for a screw-type adjustable idler that will slap right on, without (or very little) modification?
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Denisesewa » Jan 18 2013 1:37pm

:oops:
Last edited by Denisesewa on Jan 18 2013 1:57pm, edited 1 time in total.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Denisesewa » Jan 18 2013 1:45pm

[quote="Cyclebutt"][img]
100_2034%20(2).jpg
[/img]Here's another photo of the stock belt configuration after 170 miles. Only around 30 of these miles were trail. Can you see the edge fraying?

I'm going with adjustable sheets for now.

1) During installation I will rotate the motor power lead to a more "protected" clock position.
2) Run shorter belt with sheets in most closed position. Anyone have that part number? I'll look for it. test it..
a) In case belt's too short for easy installation, go back to original belt. test it...


I know that the people who tried the short belt said it was an extreemly tight fit and at least one was damaged trying to install it, you may be able to deepen the slots in the adjustable plates to allow ease of installation. I know the part # is in this thread somewhere but couldnt find it right away. I also think the hard edges of the pully teeth need to at least be smoothed over, I am trying to think of a way to make a tool to do this.

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Denisesewa » Jan 18 2013 1:52pm

Just realised I posted the throttle stuff in the wrong thread :oops:

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by justlooking » Jan 18 2013 2:22pm

Denisesewa wrote:Just realised I posted the throttle stuff in the wrong thread :oops:

blends in with this thread tough m8 :)

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Cyclebutt » Jan 19 2013 10:58am

Denisesewa wrote:
Cyclebutt wrote:[img]
100_2034%20(2).jpg
[/img]Here's another photo of the stock belt configuration after 170 miles. Only around 30 of these miles were trail. Can you see the edge fraying?

I'm going with adjustable sheets for now.

1) During installation I will rotate the motor power lead to a more "protected" clock position.
2) Run shorter belt with sheets in most closed position. Anyone have that part number? I'll look for it. test it..
a) In case belt's too short for easy installation, go back to original belt. test it...


I know that the people who tried the short belt said it was an extreemly tight fit and at least one was damaged trying to install it, you may be able to deepen the slots in the adjustable plates to allow ease of installation. I know the part # is in this thread somewhere but couldnt find it right away. I also think the hard edges of the pully teeth need to at least be smoothed over, I am trying to think of a way to make a tool to do this.
Thanks, Denisesewa. I just couldn't find the details on the short belt results. I'll skip that part now, for sure. Any suggestions for a screw (bolt) adjustable idler for belt drive? I'm positive that a constant tension idler would deliver better belt performance/life than the spring loaded type. By the way, hows the chain drive doing? You and a couple of other member have great looking, working chain drives. Bike on!

My new sheet should arrive soon. Thanks, LightningRods!
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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Denisesewa » Jan 19 2013 11:17am

So far the chain drive is holding up very well even with the cheap chinese chain, I found a soure for Diamond chain that I think I'll replace it with.
I'm thinking there would be no need for an idler if using the adjustable sheets, I suppose if you really want one you could do something like I did for the chaindrive system and use a turnbuckle instead of the spring.

Image

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Re: GNG 450 brushless Mid Drive - Primary Drive Modification

Post by Denisesewa » Jan 19 2013 11:25am

BTW, the big reason for going to chain for me is that unless the two belt pullys are perfectly aligned and absolutely perpedicular to each other ( this includes any idlers) the belt will "walk" to one side or the other and wear along its edges, there also has to be zero runout to use a static tension system or the belt will experience various tensions as it spins, that along with the poor tooth profile of the stock pullies leads me to believe its a ton more work to get it right than the chain mod as the chain will torerate some runout.

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