GNG 450 brushless Mid Drive - Primary Drive Modifications

LightningRods said:
mr.electric said:
This is the GNG build I have been working on. Belt died today. Time for a chain conversion ....
Click to expand...

Great looking bike, Mr. Electric! Perfect for the GNG mid drive. Am I seeing correctly that the parcel rack moves with the rear suspension?
Click to expand...
I just installed the gng the bike owner fabbed the rack when he initially converted with a hub motor. I think the rack does move with the suspension. The bike looks very cool. I am going to convert my personal bike with a gng soon too
 
so what is the outcome of these chain conversions ?? are they working ok?
any one found any problems so far ?
i know most are running over voltage and high watts with these so they must be strong if they are still going well.
 
LightningRods said:
Hey Guys- Sorry for the absence. I been chasing the almighty dollah. Gotta pay for those e-bike parts. :mrgreen:

First of all, yes I have the adjustable sheets tutorial up. The url is: http://www.backusstudio.com/gng/

I've posted this over on the main GNG thread but I'll repeat it here. I've developed and I'm getting ready to have made adjustable bottom bracket sheets. They should be available by mid February. I'm also working with a pulley and belt manufacturer to have custom 20mm wide pulleys made for the GNG that are as good as we're going to get them. I'm enlarging the driven pulley from 80T to 100T. That's 25% more primary reduction. The tech also recommended AT5 belts rather than a HTD belt. It's still a 5mm pitch but is "much stronger".

I'll have this drive setup manufactured and try it first on my own bike. If it still doesn't work I'll give up and convert to chain. If it does work I'll make the pulleys and belts available to anyone who wants a set.

Belt drives work on everything from racing Karts to computer drives to heavy industrial machinery. Matt Schumacher makes them work on his own custom e-bike drives. There's no reason a properly made belt system shouldn't work on the GNG.
Click to expand...

Nice tutorial Mike. Hope to get to my sheets installed this week, will paint first. How's you sheet equipped, idlerless set-up working? Mileage? When I install these sheets I'll also install a GoodYear Hawk 475-5m-15 belt (bought 2 through Amazon) without an idler. Then testing will resume, weather permitting. Bike on!
 
Since the primary drive feels less torque than the secondary drive (primary: higher RPMs/less torque...secondary: higher torque, less RPMs), it is looking like #25 chain is working well for this, compared to the stronger and more expensive #219.

Here are all the #25 suppliers I could find. If anybody here knows of more (even if you didn't buy from them), it might be useful if we could find more suppliers to post.

https://www.surpluscenter.com/sort.asp?keyword=PH25&catname=powerTrans&PAGELEN=20&PageNo=1
http://catalog.bbman.com/db/service?domain=bbman&command=locate&category=finish_sprockets
http://www.andymark.com/product-p/am-25sprockets.htm
http://www.electricscooterparts.com/sprockets25chain.html
http://tncscooters.com/index.php?route=product/category&path=63
 
Interesting links.

The main problem is the larger sprocket - the hubbed sprockets surplus centre have look good, but they have a 1/2" bore (12.7mm) vs the 12mm bore needed. The smaller one's bore isn't as critical (since the motor pulley is being machined off). Bloody imperial/metric system problem as usual!

You really need something with a smaller bore that you can enlarge for the larger pulley.
 
these are the ones i bought
57t http://www.technobotsonline.com/04b-steel-chain-sprocket-6mm-57t.html

12t http://www.technobotsonline.com/04b-steel-chain-sprocket-6mm-12t.html

chain http://www.technobotsonline.com/steel-roller-chain-04b-6mm-m.html

and the half-link [needed] http://www.technobotsonline.com/chain-offset-link-04b-6mm-32771.html
 
So after a week of corresponding with a helpful gentleman named Daniel at BrecoFlex and exchanging numerous drawings and measurements, we came up with this:

BrecoFlexDriven.jpg


It's a beautifully CNC crafted, 100 tooth, 20 mm wide, 5mm AT5 pitch aluminum pulley that will bolt right onto the GNG jackshaft. It's perfect.

It also costs this:

BrecoFlexPrice.jpg


If 30 of us duct taped our wallets together we could each get one of these beauties for a mere $171 apiece. Ouch.

If you look further down the price list you'll see that I also spec'd a 14 tooth 20mm drive sprocket. Those are more possible. If 30 of us went in together we could get those for $25.75 each. I think that would be worth it. Unfortunately this one is an AT5 which means it won't work with any cheapie HTD pulleys or belts.

Ordering a CNCed HTD sprocket from BrecoFlex is also a possibility if Daniel is still speaking to me.

I also have a quote request in at a company that makes decent looking fiberglass reinforced nylon pulleys with aluminum hubs. I'll report back on how that turns out.

My engineering drawings are in at the metal fabrication shop to get the 68mm adjustable BB sheets made. I should get a firm bid on that tomorrow. If you are one of those 73mm guys looking for a GNG solution give me a PM and I'll look into getting a run of 73mm BB sets made.
 
Good work. Before going this route, I would make sure they note radius /edge conditions that you are good with.

I would have quote also a taper lock hub if that is available insert from the cad files. You would also need the center bushing but it is small and could be supplied inexpensively for a variety of shaft diameters. You could re purpose it in many more applications. It could also open it up to many common cart and motor bike shaft sizes which could expand the market potential to the point where you could injection mold the whole thing and make enough back to pay for the mold. IMO it is a perfect part with a few mods to convert to (glass filled nylon) plastic.
 
Big difference in cost for a stock 80 tooth compared to the custom 100 tooth :shock: The shaft size issue needs to be addressed :?: Hard to beat on value compared to the #25 chain solution :| The belts shine when motor rpm gets high as is typical with higher voltage RC motors.

Consider that by going to a 5/8 inch jackshaft and replacing the bearings you can economically resolve belt or chain primary issues as well as improving the jackshaft freewheel to stock 13 tooth units. Now to get the cadence down to 80-90 rpm and get a robust bottom bracket for those 12 foot drops :twisted: :mrgreen:
 
LightningRods said:
It's perfect.

It also costs this:



If 30 of us duct taped our wallets together we could each get one of these beauties for a mere $171 apiece. Ouch.

If you look further down the price list you'll see that I also spec'd a 14 tooth 20mm drive sprocket. Those are more possible. If 30 of us went in together we could get those for $25.75 each. I think that would be worth it. Unfortunately this one is an AT5 which means it won't work with any cheapie HTD pulleys or belts.
Click to expand...

ouch!!!
think i will have to stand down on this mod :(
 
The main problem is the larger sprocket - the hubbed sprockets surplus centre have look good, but they have a 1/2" bore (12.7mm) vs the 12mm bore needed.
Click to expand...

SDP-SI has affordable sleeves to enlarge a 10mm or 12mm shaft to 1/2-inch. That may add too much wobble, but if it ends up being snug enough, it may be helpful.

https://sdp-si.com/eStore/Direct.asp?GroupID=273
 
I'm building a GNG bike for a friend. He is adamant that he wants the primary to run with bike chain not #25 as I would recommend. Has anyone done this. He has the adjustable lightning rod plates so tensioning should be quite easy.
 
mr.electric said:
I'm building a GNG bike for a friend. He is adamant that he wants the primary to run with bike chain not #25 as I would recommend. Has anyone done this. He has the adjustable lightning rod plates so tensioning should be quite easy.
Click to expand...

I did this my first ebike (not GNG). It made for a very large (physical size and 3 stages) reduction unit due to the size of bike chain. I would tell him it is #25 or nothing. It is easy to get and deal with. It is strong and runs quiet as long as it is lubed. It also keeps the sprocket sizes to something manageable.

I wanted to use all bike components so replacements were easy to find and deal with. #25 is easy to get and deal with once you look and get the right chain breaker.

Clay
 
http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=1320 Scroll down to "bee" posted pictures of a 3D printed pulley

There are some interesting things going on here. Seems there may be a lower cost solution to the primary drive problem. I had heard of 3D printing before but had little working knowledge about it. My proposal is a 3D slip-on teflon primary drive pulley shell. Match the inside of the shell with the outside pattern of the existing pulley, make it large enough (however many tooth count necessary) to be strong, slip it on/glue it in place. The original belt (using the adjustable sheets) could be retained, sharp edged pulley would no longer eat away at belt, and the large pulley could be retained. Also, a slightly larger drive pulley could provide enough tooth engagement to eliminate an idler. Teflon just sounds right, easy on the belt, anyone? Different material?

From a commuter standpoint, the loss of some gear reduction wouldn't matter that much. From a reliability stand point, this could solve the primary drive issue and off-road riders could still change the large pulley to gain back some torque.

A teflon slip-on drive pulley enlarger, no filing required.

Does anyone out there have the knowledge and connections to try this? I would love to try this. My project is still (work load) on standby...

Bike on!
 
Miles said:
Cyclebutt said:
A teflon slip-on drive pulley enlarger, no filing required.
Click to expand...
Teflon?????
Click to expand...
Whatcha think? Could it handle the heat? Definitely would be easy on the belt. Would a slip-on brass shell be possible for 3D printing? That drive pulley seems to be the main issue. Just looking for a simple, effective fix.
 
The first problem is that a plastic pulley which could be fitted on to the existing 14t would probably have to be at least 21t. You'd have to gain back the loss of reduction somewhere. A 120t driven pulley would do that, I guess....

I only know Teflon (PTFE) as a coating or addittive. I couldn't imagine that it's possible to use it for 3D printing - it has quite a high melting point of 330 deg. C. You probably don't want something so slippy...
 
Miles said:
The first problem is that a plastic pulley which could be fitted on to the existing 14t would probably have to be at least 21t. You'd have to gain back the loss of reduction somewhere. A 120t driven pulley would do that, I guess....

I only know Teflon (PTFE) as a coating or addittive. I couldn't imagine that it's possible to use it for 3D printing - it has quite a high melting point of 330 deg. C. You probably don't want something so slippy...
Click to expand...
True. Nylon, perhaps? Maybe a brass slip-on shell? A slip/glue-on shell would be a nice simple up-grade, just needs to be the right material. As far as a glue, "doctorbass" recommends Scotchweld DP420(?) for gluing his torque arms to drop-outs. With that kind of shear strength it's gotta be good for this application.

I need to get on with this project. Still haven't mounted the adjustable sheets and my new GoodYear belts have already arrived. Time, time, time....
 
Interesting development regarding the primary drive pulley going on at this page:

http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=1380

Nice!
 
Here's a link to the primary drive pulley development:

http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=1395

Summary:
On this page you will find that a slip-on pulley shell may soon be available for the motor pulley. Hopefully it will be a 18/20 tooth in 15 or 20mm width made of steel. ScotchWeld DP420 epoxy could be used to attach it to the original pulley.

christerljung found a link to buy the motor for a good price.

LightningRods is manufacturing both, adjustable plates for the motor-to-jack shaft mount, and the bottom bracket-to-motor mounts.

Conclusion: We are just a drive pulley away from a total reinvention of this basic kit that has little belt life, to one that could be the answer to our affordable Mid-Drive quest. Not only this, but one can now acquire the individual pieces to custom build their own thoroughly improved version of the GNG kit. Very nice.
 
It has been recommended from
Miles (very well respected in this forum) and Crossbreak another great contributor.
They said it here.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=1335

Potential EASY most ECONOMICAL Solution for improving stock belt drive IS

95 Tooth pulley/top sprocket $12 http://tncscooters.com/index.php?route=product/product&path=63_94&product_id=463
16 Tooth Drive
And I would add LightningRods ADJUSTABLE top plates to the solution.


Questions about this solution are?

1. About the top socket from TNTthat has a "threaded center"
Will it screw on or will the part from TNT need to be drilled out for holes to bolt on?
Maybe a way to answer this is to ask if the stock pulley treads on or is bolted on?
2. Where is the best place to buy the recommended 16T drive sprocket. If no one knows where then what do we need to know to order a
compatible one (do not want to file shaft)?
3. What size belt is needed (length)and what is the strongest most reliable belt and where can I get one?
Would you go with 15mm or 20mm wide? Afraid 20mm may drift off the top pulley. Your opinions about drifting are welcome.
4. Would the chain on the opposite side need to have its length modified.

If we can find the answers to these questions it may prove to be a reasonable easy to install economical solution.
Thank you every one in advance for contributing.


Stock Ratio 80 and 14 = 5.7
Modified Ratio 95 and 16 = 5.9

The benefit of using 16 vs 14 for drive unit is more teeth=less chance of slippage. Also changing the drive sprocket my eliminate the "sharp" edges from the stock one that appears to be responsible for premature ware and tear.
 

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microbatman...

1. Yes it will screw on the adapter that the original pulley is already on. Already discussed.
2. Don't know the best place to get, depends on where you live I guess. The only way to get a new pulley on the output shaft of the motor is to file or turn the old pulley off as it is milled into the shaft. Already discussed. A slip over pulley is in the works, but it will be closer to 20 teeth.
3. Not sure, but answered in the thread earlier. Look for it. 20mm is recommended for handling the power and not slipping. Already discussed.
4. yes, already discussed as well.

Search the forum using google ("whatever you are looking for" endless sphere) and you will find these answers.

Clay
 
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