GNG torque trouble (something's slipping)

[hillyterrain]

I just got my GNG setup working and it is toooo much fun :wink:

Unfortunately when I was in the highest gear on my 9 speed cassette and opened the throttle too fast the resulting high torque caused the drive-train to do a loud ratcheting sound, I thought the chain was slipping over the small gear on the cassette .. maybe a stretched chain, gotta get a new one and be more careful with torque, use lower gears .. which I did..

Now 3 days later it's gotten so bad that I can barely put any torque at all on the drive train without this slipping happening. I'm no longer sure it's the chain in the back, for a little while I thought it was the belt slipping over the little teeth on the driven pully, then I thought it was the chain again, maybe it is internal in the freewheel / crank combo? Having no clue what it is I'm having a hard time to troubleshoot it ..

It's so bad that when I open the throttle all I here and feels are the clacks from something slipping in the drivetrain, it's almost impossible to see with the naked eye which it is thought, since belt and chain are still moving in between the clacks ..

Did anyone have similar issues or ideas how to figure it out / fix it?

Thanks a lot!!

 

[mwkeefer]

Assuming this is a Gen1, check your 12T freewheel - look inside it, are you missing the NUT and has the sheer pin gone? I've lost my nut and then the pin... don't remember the size, take it to the HW store, I walk my bikes in they all know me now... Replace the sheer pin and tighten on a new nut with BLUE loctite if that is the issue.

Not much that could slip in the GNG side of the drive train that you wouldn't be able to identify immediately like belt slippage, etc... Check that your freewheeling cranks are tight (chainrings, fixing bolts, etc).. Sure it's not your bike's rear?

-Mike

 

[Tinto]

I had the same sensation and (in my wisdom) narrowed it down the the bike drive train so bought a new chain and rear cassette as mine were a bit old...
...Then realised it was the drive belt!
I was missing around 15 teeth and under load it would slip - which sounds and feels exactly like your chain slipping.

Have a look if you've got a belt - you're probably missing a lot of teeth.

I bought a couple of belts, fitted one and it has been perfect since.
Have also learned to roll on the throttle a bit smoother before opening it right up.

 

[hillyterrain]

Wow, thanks for the superfast response! I guess it might be the freewheel, when I push the bike backwards it makes an awful sound and skids a couple of times before engaging and turning the jackshaft and engine backwards .. it's GNG v1.1 I assume it's the same freewheel, when you say look inside you mean take it apart into pieces? I need to scramble the tools together, this is what it looks like, is it the same?

 

[mwkeefer]

And the awful sound is from your rear bicycle freewheel right?

I ask because pushing these things backwards makes an awful racket in some cases just does (one way forward freewheeling)...

What brand / type / tooth count do you have on the rear?

I only ask because I find going to a 7 speed shifter / cluster / freewheel affords the use of 7 speed chain which is a bit more HD than 8,9,10 - this is likely no big deal just curious

But yeah if the sound is coming from the center of the rear wheel (lift it and try to spin it / pedal it), also this happens no matter if you pedal or power right?

-Mike

 

[hillyterrain]

When pushing the bike back the sound comes from the fixed chain, I think it is a little loose, the rear cassette is quiet.

It's a 9 speed cassette, not sure about the brand some bikestore put it in a while back when I was doing a euro-tour and my original cassette was too worn ..


The slipping / ratcheting under torque only happens with the motor running, I tried stepping really hard in the pedals to see if I can make it happen without the motor but am not really successful with it, sometimes I hear an awful sound but not quite the same .. Makes me thinking again it's the belt, just took it off and it has all its teeth, looks a bit fuzzy though .. the nice black sheen is off and the fiberglass hows but the teeth look good .. I'm really lost on this one..

 

[mwkeefer]

You may have blown your 12t driver freewheel engagement arms, think you can get new ones from GNGs site... you also may have killed the freewheel in the chainring adapter, easy enough to check

-Mike

 

[Mechdude]

Hi HillyTerran, I had a similar problem after fitting Lightning rods adjuster plates.
At first, I though it was the primary freewheel, but a few days later when the belt failed, I realised that it was the belt slipping.
With a new belt it seems fine but it starts to skip after the belt has worn in, and for me re-tensioning didn't help.
As the teeth skip, it puts a shock through the whole chain system which is why it's difficult to determine where the fault is.
I've order some sprockets and chain for mine. Sick of breaking belts!
From what I have seen, the primary freewheel, if maintained is actually quite robust.

Cheers
Howard

 

[christerljung]

Excactly as described above. When the belt slips it echoes through the whole drivesystem and it's hard to identify wich part is slipping. Belt slipping is the most common i would say.
You could do a chainconversion or lower the power from the motor.
Belt life with original setup works fine for about 3 months (120km) of commuting for me.

 

[d8veh]

You can get slipping of the belt, the primary chain or the final chain. My Gen 2 started jumping the final chain when I went from 20 to 30 amps. I took a few links out to tighten the tension in the lower part and fully tightened the derailleur tension screw, and it was OK afterwards.

 

[mwkeefer]

Excactly as described above. When the belt slips it echoes through the whole drivesystem and it's hard to identify wich part is slipping. Belt slipping is the most common i would say.
You could do a chainconversion or lower the power from the motor.
Belt life with original setup works fine for about 3 months (120km) of commuting for me.

Christer,

I'm curious mostly because I've run excesses of 66.6v nominal (18S) and have pushed it as far as 38 amps battery current and a 2.5 ratio or 85A for phase current and I never skipped a belt, broke one, etc... in fact the only mechanical issue I had was a tensioner from the factory which was missing a spring and a slight miscalculation I didn't note for months until I attempted to fold my Dahon Jack 26" FS folder and realized the supports and protection plates for the large pulley had placed a truss (think that's the right word) at the very top, making the whole unit 2.5-3.5mm too tall to mount.

In either case, after a quite long run (8 miles without really letting up) the bike died... I pulled the packs and reset everything and managed to limp home, from then on it seemed I had horribly choppy performance on startup followed by once it kicked in or synced, BAM... So I am figuring I have killed hall sensors in my first Gen1 bike like I believe you did and your running on a sensor less controller now till you fix your halls (I have the SS441A Honeywells, good drop in replacement)... You were running a Lyen sensored controller right? I ask because I think we are the only two so far to damage the halls in operation (though you have gone higher voltage and likely current than I, I've been pushing them to their limits and logging data.

I'm wondering now (guess I'll check it later) what the average Hall +5v and GND rails really measure out to on a stock controller and what they measure out to with the Lyen controller.... basically thinking perhaps the voltage (especially at higher voltages without a specifically tuned 12v rail based on anticipated input voltage) even regulated being a bit higher in return (or lower resulting in persistent PWM mode) voltage and thus causing our halls to poof (or they are just cheap shit!).

I have about 10 sensor less controllers, or capable of excellent sensorless control - discovered by accident after a hall failure, unplugged the harness and whalla bike worked again... perhaps I'll mod one of these to 13-15S, re gear the secondary with a higher ratio to compensate and affix a big old 50+t chain ring on front.

In either case, sorry to hijack your thread just realized I think were the only two who have had hall issues, other than that and some minor fiddling and adjustment - even in stock form I had no problem at 2KW... I never slammed it, never went directly to WOT (okay almost never) and basically rode it mostly on reduced power setting but once I engaged full 100% power I could hit 40mph on flat ground if I tucked on my 26" Upright Dahon Jack.

Finally- if the belt is slipping it will feel exactly as when you run over the grating in the street at an interstate tollbooth to remind you oh not so politely to SLOW DOWN.... that indicated too much torque too fast for the 14T/80T stock primary combo... But the one time I slipped my belt there was no mistaken what it was, not to be juvenile but it felt like the bike violently farted.

Hope it helps!

-Mike

 

[d8veh]

Just another thought, which is probably worth checking. When you get a faulty phase wire connection, the motor jumps like a mechanical fault, and it can feel like a chain slipping.

 

[hillyterrain]

Thanks for all your replies, I'll try a new belt today (if it is the belt, then the 1st one lasted 1-2 days ..), where do you all buy your belts? I got mine from McMaster and boy it's too expensive ..

I have no experience with the crank freewheel, so how would I check whether that is the problem? Or how to check the hall wires ? Just do a continuity check? My setup is stock, 22Amps, 12s LiPo, I keep filing down the motor cog but don't want to file it down to much (not that this is what causes the belt to slip), I do go up 1.2 miles with 17% - 22% grade every morning for my commute ..

This is what my belt looks like, the black came off on one side so I filed some more and turned it around and it still rubbed the black sheen off on the other side, more filing necessary? The belt is rather on the snug side, it does have a tiny amount of give when poked from the side, do you rather want it snug or loose? It was such a struggle to get it tightened without the belt running out that I'm reluctant to touch the belt alignment ..


Thanks again!! Better be riding today than taking the bus again

 

[rp3]

My belts started slipping when they looked like that. You need to get the belt very tight to have no slippage. It really only has to slip once and it's wrecked.

 

[hillyterrain]

Thanks I'll try the new belt today if ups decided to leave it, where do you buy your belts?

 

[hillyterrain]

The new belt is goodyear and is ever so slightly longer so that it hangs limb off the pully, the Gates belt was so snug that I had a hard time getting it on and off .. I smell a chain mod coming, I finally blame it on the belt .. still eager to learn about your belt sources !!

Thanks!!

 

[mwkeefer]

The build consistency of these units must vary widely. I've had no issues with my Belt even > 2KW peaks on 18S but... I've fried or damaged a Hall Sensor. Granted I'm usually easy on the initial 0-4/5mph point when I slam it so perhaps that is why my belts and chains don't seem to break as everyone elses... then again apparently either over voltage or heat buildup (32 mile round trip) from sustained high wattage (>1500w) caused the halls in mine to malfunction so.. eh.

That 100w of pure parasitic loss is a lot to stomach on the Gen1 units, my main reason for being interested in a chain drive replacement... I figure #25 for stage #1, it will handle the RPM fine and should be plenty strong in even at over volted RPMs.

I think it would be highly possible to bump the primary using #25 without suffering breakage or cordal effects too significantly... as I've learned the hard way adjusting my LSD Hard Rock the past few days... chain alignment isn't just about power, it's about noise... right now my bike runs (Astro 3220 powered Hard Rock) but it sounds like a flaming chainsaw! Needless to say I'll address this.

I saw a post a while back about phase issues, let me ask are you using the stock controller or something else? If something else, what exactly and what settings? If it's stock, other than checking connections continuity and perhaps hot gluing them if needed to prevent intermittent issues that's about all I have.

-Mike

 

[hillyterrain]

I put the new belt on (also seems to have slightly different profile) and since I didn't feel like pulling the whole assembly together I simply threw the belt tensioner on, surprisingly first I had a lower idle wattage count, after tightening the belt real snug it is the same I had compared to using only the adjustable sheets, ~130Watts. Seems high in either case, so I guess if you loosen the belt a bit the waste wattage goes down, but the belt is also more likely to slip?

I'm using a real conservative ramp rate on the throttle and the skipping is gone .. hurray!! No more bus tomorrow! I see videos with people popping wheelies and doing jumps, I do none of that, I feel my belt should be fine .. Wondering if the belt tensioner pushes the belt so close that more teeth are engaged with that tiny pully ..

 

[christerljung]

Mike, I run a sensored 12-fet Lyen controller on my modded 24S GNG and stock controller on the commuter. No Hall issues.
That 100w of pure parasitic loss is not correct since you need to measure that under load (when the belt get lowered tension on the idler side).
And then it still would be hard to determine which Watts that is parasitic and which is forwarding power.
Maybe a combination of LRsheets and stock tensioner is the winning setup for longer belt-life.

 

[mwkeefer]

I put the new belt on (also seems to have slightly different profile) and since I didn't feel like pulling the whole assembly together I simply threw the belt tensioner on, surprisingly first I had a lower idle wattage count, after tightening the belt real snug it is the same I had compared to using only the adjustable sheets, ~130Watts. Seems high in either case, so I guess if you loosen the belt a bit the waste wattage goes down, but the belt is also more likely to slip?

I'm using a real conservative ramp rate on the throttle and the skipping is gone .. hurray!! No more bus tomorrow! I see videos with people popping wheelies and doing jumps, I do none of that, I feel my belt should be fine .. Wondering if the belt tensioner pushes the belt so close that more teeth are engaged with that tiny pully ..

Bingo that's exactly the point of it to get more wrap around the little 14t drive pulley and glad you got it working!
Is that 130w with power transmission to the rear wheel, second stage engaged or just the belt primary?

Christerljung,

I thought you had your halls fail and went to a sensorless lyen, I must have you confused with someone else on the main GNG v1 thread, sorry.
24S GNG with Lyen 12 fet - what mods? I get the 100w figure from doing nothing more than bolting on a GNG v1 stock out of box and running it on the benchtop, I see 130w add parasitic loss from second stage output (connect to chainring but without chain ring connected to rear wheel) and your now at 150w and if you remove the belt drive and run the motor without load at all it's only a mere 30w of loss (at 48.1v / 20A limit) - so no matter what you do on the stock unit... That was my uber scientific method for determining no load losses at various stages and indicates to me (rule of thumb) that:

The motor alone no load required 30w to spin up to maximum RPM at 48v that's no load current of .63 amps - this is excellent no load current for any motor!
Connect up the stock primary belt reduction with tensioner (as I received two) and run the same test and now your pulling 130w at 48v or net additional loss of 100w (yes this will change you are right but just from go for rough science) and bumped no load current to 2.7 amps...
Connect the final drive chain to the freewheeling chain ring (no connection on inner chain ring to rear cluster) and consumption jumped to 144w so an additional 14w for the final chain drive for a total mechanical (excluding rear derailleur, etc) no load loss of: 144 - 30 = 114w wasted power, 100 whole watts of that appearing to come from that primary reduction.... please friend, by all means correct me if I am incorrect?

I will add that after very roughly rounding my drive 14t (very rough, just got the sharp edges off) and putting about 120 miles on the drive system at various voltages I ran the above test and the belt system was now only costing me 75w no load so it seems to wear in over time a bit (the rounding didn't help the efficiency, I tested after that mod too) - perhaps a better belt tensioner or even a conversion to wider belt requiring less tension and yielding more wrap around or even a #25 chain drive is really the way to go, I would guesstimate 14 to 30w static losses then in keeping with the #35 second stage of the GNG and presuming a perfect chain line.

Regards,
Mike

 

[skyungjae]

Did it turn out to be the belt?

 

[hillyterrain]

Yes, and posted above, using the belt tensioner to engage more teeth and a slow and smooth throttle ramp rate keep the belt happy

 

[pollux]

Good day all,
Only posted once in my life so if I do it wrong or break any rules my apoligies in advance. I bought the GNG mid drive and have been using it for about a month. Prior to buying it I read a lot of the posts here at ES on the GNG mid, among other issues there was lots of talk about belt failure. In my first10 kilometers the belt started to wear 160km later the belt is almost finished. Filing pully teeth, adjusting tensioner, changing mounting plates (lightning rods), converting to chain and other suggestions seem not to be the complete soulution. Lots of people seem to be just stocking and carrying with them extra belts. I worked in the packaging industry and have lots of expierience with timing belts on machines and I have never seen a belt wear so fast before, my best guess is misalignment. The belt always pulls to the motor side does this happen to anyone else? To finish I just want to thank you all for the ton of info you people supply

 

[skyungjae]

Good day all,
Only posted once in my life so if I do it wrong or break any rules my apoligies in advance. I bought the GNG mid drive and have been using it for about a month. Prior to buying it I read a lot of the posts here at ES on the GNG mid, among other issues there was lots of talk about belt failure. In my first10 kilometers the belt started to wear 160km later the belt is almost finished. Filing pully teeth, adjusting tensioner, changing mounting plates (lightning rods), converting to chain and other suggestions seem not to be the complete soulution. Lots of people seem to be just stocking and carrying with them extra belts. I worked in the packaging industry and have lots of expierience with timing belts on machines and I have never seen a belt wear so fast before, my best guess is misalignment. The belt always pulls to the motor side does this happen to anyone else? To finish I just want to thank you all for the ton of info you people supply

Hmmm... I think the type of riding has more of an effect on belt wear rather than the actual design. I'm coming up on 400 miles (~640km) with the original belt. I've mentioned on various posts that I do pedal, pretty much, all the time. I also don't use the motor much from starting from a stop. I don't think the kit was designed to be ran at 1000W (probably why it's advertised as a 450W) all the time or to be full throttled from a stop.

There's also a big issue with the quality control. Not everyone has been lucky getting a perfectly functioning kit. Hopefully you can figure out what's wrong with your kit.

They way I see it, even with the original belt and tensioners, it's not all that bad swapping belts every 3-6 months. It's cheaper than an oil change. It's probably easier than doing an oil change too. I'm willing to bet it's easier than replacing the external gear boxes for cyclone style motors too.

 

[pollux]

Thanks for the comments,
I think you are right about quality and it would be cheaper to just change the belts. I found them at Vbeltsupply for under $8 but since I live in Canada there is a $20 shipping charge, imagine for an item that probably weighs 2 ounces. I guess I should order a half dozen and just consider it a maintenance cost. My riding is at least 50 % pedaling (no motor, I still need the exercise) and when I use the motor it is only as a boost to get up to speed. On my 40 K ride there is only one hill the rest is flat, I have a cycle anaylst display and I try to keep the power use around 10 amps while pedalling (no choice my 10 amp battery would never last 40 K) I will admit that I have used just the motor at full throttle a couple of times (who could resist) but only for 30 seconds or so, top speed 45 K I guess thats about 27 miles an hour. With a total weight: bike, rider, baggage, battery and motor of 295 pounds I guess thats not bad. Thanks again.