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

[wavezz2k]

Still wondering if anyone's figured out is this small pulley part of the electric motor's armature shaft ?? -

Torque rotation shouldn't be an issue because under load, the assembly is pulling itself "into" the down tube. However, at the power levels some of you are operating, "assembly flex' could become a problem, might require some beefing up.

; FWIW, my undergraduate is structural mechanics - the chain 'pull' is eccentric to the motor / bike/ mount hardware centerline, so there's definitely a 'torque' on the motor assembly rotating clockwise, when looking down from above, hence Christerl's 'torque strut' makes perfect sense, and assumes to work well.

And agreed with earlier post, the 'deep knee' idler tension is to get more teeth on the drive pulley.

 

[christerljung]

fabio: It should be in the feeding positive line yes. However i haven´t tried this myself, cant be sure what the result will be.

Here is what happened so far with my firstreduction-chain-conversion:

Grinding with rotating motorshaft:

Some frightening oval result, I belive the grinder oscillated in some way.

Tried the sander-grind instead? What is it called in correct english?

Much better. Within 0.4mm without any detailwork.

The pulley seem to be part of shaft. If there was a pressfit, i would at some level of grinding get some loose parts from the pulley, right?
Or maybe shaft is smaller than the 14mm i got right now? Will probably take it down to 12mm, then fit the new chainpulley with a 3mm pin straight through the shaft.

 

[epack]

Nice work on the first reduction chain conversion. When you are done, please post your thoughts on the change in noise levels with the added chain.

 

[Kepler]

Thats weird about the pulley seeming like its part of the shaft. You would think the pulley would need to be pressed on after the shaft is assembled through the motor case and bearing.

Has anyone pulled one of these motors apart yet? It kind of looks like the pulley comes in contact with the shaft bearing rather then the shaft. It would be interesting to see what is on the other side of the motor front housing.

 

[heathyoung]

Yeah thats odd alright. I just recieved mine yesterday, need to take a close look at it. It does indeed look like the pulley is supported by the bearing, what is inside that motor?

You could put a freewheel on the large cog part, the metal and plastic ones that scooterparts have are designed for them and large belt reductions.

Has anyone tried the shorter belts on these on a bike yet? That tensioner - mmmm.... not inspiring at all.

BTW - Something clicked when I looked at that small pulley - it looks very familiar to the pulleys used on the GEBE (golden eagle bike engine) kits - they are threaded onto the motor shaft.

http://www.bikeengines.com/orderpage2.htm - Look at the HTD gears. IIRC they are 10mm wide belts, driving HUGE 250 something tooth reductions. I wonder how they manage not to cog / break (I had one of these, they had thin little belts that used to snap, went to one with a thickr backing, lasted forever...

 

[ebiker1]

I'm following this thread and missed something. how did you grind the shaft differently to get a better result? just in case i have to do it at some point.

 

[Rassy]

My unit has a tic tic tic ... that comes and goes. Has done this on and off since the beginning. Seems to come from the motor/belt area. Can't find anything loose, etc.

This noise is only under load, with or without pedaling. The tic is speed related, such as once every revolution of the belt. Sometimes goes away when shifted to another gear, sometimes doesn't.

Anyone else have this problem? Any ideas?

Thanks,

 

[bzhwindtalker]

Sounds like belt skipping to me, but it could be a lot of things!

 

[RustySpokes]

how did you grind the shaft differently to get a better result?

He looks to have used a flap disc instead of a grinding disc.

 

[christerljung]

how did you grind the shaft differently to get a better result?

He looks to have used a flap disc instead of a grinding disc.

Yes, the grinder was in some kind of oscillation with the shaft. No matter how i tried to keep it steady.
-Flapdisc!! So thats the correct name! Thanks!

 

[bzhwindtalker]

Any advice about going with a single #25 chain drive? It would be the simplest cheapest option out there. 12-68t and renforced chain.

 

[Cyclebutt]

Still wondering if anyone's figured out is this small pulley part of the electric motor's armature shaft ?? -

Torque rotation shouldn't be an issue because under load, the assembly is pulling itself "into" the down tube. However, at the power levels some of you are operating, "assembly flex' could become a problem, might require some beefing up.

; FWIW, my undergraduate is structural mechanics - the chain 'pull' is eccentric to the motor / bike/ mount hardware centerline, so there's definitely a 'torque' on the motor assembly rotating clockwise, when looking down from above, hence Christerl's 'torque strut' makes perfect sense, and assumes to work well.

And agreed with earlier post, the 'deep knee' idler tension is to get more teeth on the drive pulley.

Ahh, yes. It's been many moons ago I earned my little string of letters (AET,BSET), I wasn't considering all aspects. Torsional forces on one side oppose the other and leave only an eccentric pull to the whole assembly? Thus, flex? Anyway, the torque converter shaft is what makes this design superior to the one-sided affairs, just saying.

Where did Christer. show (page?) a "torque strut?" Missed that. I'd like to see it (for future reference), I'm sure he needed it for the power levels he's running. Thanks, wavezz2k.

 

[Cyclebutt]

how did you grind the shaft differently to get a better result?

He looks to have used a flap disc instead of a grinding disc.

Yes, the grinder was in some kind of oscillation with the shaft. No matter how i tried to keep it steady.
-Flapdisc!! So thats the correct name! Thanks!

Christerljung, you are making things very interesting, my friend. I'm checking this post almost exclusively now. This way, I don't have to miss my engineering days, get to LIVE it! In some cases, re-learn it, HA! Good fun.

 

[fabiograssi]

In my experience, with standard power levels (14s lipo and stardand 20A controller from GNG), I can say that is a LOT of torque problem in structure... I am using a kona kikapu full susp frame. First ride destroyed the balls in axle (ok, that was old and used), and each hit in throttle, i can fell and see all the motor structure moving to right, and the mais chain bringing the cassete to front, "twisting" the back susp strut to right...

I will try to add a "torque arm" like christer, but I fell that the bushings and bearings of the back of the frame won't last too much!

- Fabio

 

[bzhwindtalker]

The frame twist you are experiancing is very dependant on the frame you use. My first mid drive bike had this problem and the frame broke two times, just saying... My freeride Lapierre has zero issues on that subject.

 

[fabiograssi]

The frame twist you are experiancing is very dependant on the frame you use. My first mid drive bike had this problem and the frame broke two times, just saying... My freeride Lapierre has zero issues on that subject.

Yes, I really believe that is one reason... Just to know, this Lapierre frame have bushings, bearings or both? Can you post some pictures of the back suspension unit?

- Fabio

 

[ebiker1]

Still wondering if anyone's figured out is this small pulley part of the electric motor's armature shaft ?? -

Torque rotation shouldn't be an issue because under load, the assembly is pulling itself "into" the down tube. However, at the power levels some of you are operating, "assembly flex' could become a problem, might require some beefing up.

; FWIW, my undergraduate is structural mechanics - the chain 'pull' is eccentric to the motor / bike/ mount hardware centerline, so there's definitely a 'torque' on the motor assembly rotating clockwise, when looking down from above, hence Christerl's 'torque strut' makes perfect sense, and assumes to work well.

And agreed with earlier post, the 'deep knee' idler tension is to get more teeth on the drive pulley.

Ahh, yes. It's been many moons ago I earned my little string of letters (AET,BSET), I wasn't considering all aspects. Torsional forces on one side oppose the other and leave only an eccentric pull to the whole assembly? Thus, flex? Anyway, the torque converter shaft is what makes this design superior to the one-sided affairs, just saying.

Where did Christer. show (page?) a "torque strut?" Missed that. I'd like to see it (for future reference), I'm sure he needed it for the power levels he's running. Thanks, wavezz2k.

well. i managed to get a BSFA and topped it off with a BSBS........but am curious about the torque arm also.

 

[fabiograssi]

The "christerljung torque arm" is here:

http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=300#p646441

 

[parajared]

So far my only problem is the belt slips when under higher power (around 1500watts). The kit worked fine until the belt stretched. I think the solution may be as easy as a way to put a little more tension back on the belt.

I am going to push for an easy solution that anyone can do with common tools and materials. I will report back if I find one.

 

[deepfraught]

Two of these are enroute for a friend and myself. He will be commuting 27km. Me just for the experience/offroad trial/wheelies. I was considering an old bike to fit it to, but stumbled on near new 2011 Scott Scale 50 for sale only $75 more than the kit. So now I have a good hard tail to install the GNG on.
I was considering the idea of a single 10S 5800mah Zippy Compact battery for lower cadence and simpler packaging. I have a 36V/48V 9C 27A controller to see if it will work. Otherwise have two 8Ah Turnigy 6S on stock 48V 22A controller to get started with.

 

[Cyclebutt]

The "christerljung torque arm" is here:

http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=300#p646441

Ahh! Thanks Fabio! I guess I was looking at the chain guide back then as that was my personal issue at the time.

 

[bzhwindtalker]

I just ordered some stuff to build a 219 reduction set based on a 11-60 ratio. Here is where I got the big sprocket : http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=320978565858 It was the smallest thooth count I could find on ebay in a non-split sprocket. I did not find an extron composite sprocket in this size (tey are very nice for noise and weigth reduction). 60t of #219 works out at about 15cm in diameter, the original pulley is 13. Bombproof and quite silent but testing will tell!

 

[christerljung]

#219 is a nice pitch. What motorpulley are you buying? Is was really close to order my new reduction from the kartingscene. There is that extron sprocket and also these small pulleys with a nice flange for mounting, but they are maybe for #35:
http://www.forsman-motor.se/motordrev-11-t/787-0 That flange starts ideas about great mounting alternatives. 8)
However i ended up with the #25 for some other reasons. Should have been delivered this afternoon but the post did something wrong

 

[christerljung]

Here is that torque-strut again, since some of you friends asked for it:

 

[bzhwindtalker]

I got a really similar one from ebay a while ago. Same shape and all, made for a Rotax motor if I recall.