Bafang Ultra pedal engagement issue

BCBeaver

Member
I have an ultra in front of a Rohloff hub. I pause pedalling to shift then hit the pedals again. Doing this repeatedly under heavy acceleration is probably not the best for my drive but it happens. The issue that has developed is that my cranks don't engage for almost 1/2 rotation. I haven't pulled it apart but plan to soon (before it becomes unrideable). Has anyone else had this issue and if so what parts will I need? Is it smashed dogs? I'd like to minimize my downtime by having parts ready.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
The first thing I would look at would be the front drive sprocket. When turning the crank that first half turn, is the drive sprocket turning as well?
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
There's your issue. That sprocket should turn any time the crank is being turned in the forward direction.....
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
You asked didn't you? Or have I misunderstood your question?

Just trying to help. No point in getting pissy about it....
 

Pulsar

Member
Region
USA
City
DFW
Roller clutch bearing maybe? I assume our Ultra motor has a RCB bearing to allow us to freewheel as needed. If the sprocket is no longer fully locked to the crank at all times that bearing may be going out.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
There's 2 clutches on that shaft. There's the internal one that allows the motor to stop spinning while coasting, and the second is on the sprocket itself that allows the motor to turn the shaft without spinning the crank.

In our OP's case, it sounds like the one on the sprocket has an issue.
 

BCBeaver

Member
Update in case anyone has a similar issue.

I had complete failure on the way to work this morning. I stood on the pedals and something went snap, I could pedal all I wanted and go nowhere but the motor still engaged under throttle so I wasn't walking.

I got to work and ripped the motor apart (I work in an E bike shop). The primary steel gear has a pawled clutch inside it, the notches that the pawls engage in were all stripped out, the pawls look fine.

I ordered the parts from Green bike kit. I ordered a new pawled clutch as well because they're cheap.

 

JRA

Well-Known Member
Update in case anyone has a similar issue.

I had complete failure on the way to work this morning. I stood on the pedals and something went snap, I could pedal all I wanted and go nowhere but the motor still engaged under throttle so I wasn't walking.

I got to work and ripped the motor apart (I work in an E bike shop). The primary steel gear has a pawled clutch inside it, the notches that the pawls engage in were all stripped out, the pawls look fine.

I ordered the parts from Green bike kit. I ordered a new pawled clutch as well because they're cheap.

That is the very area that is being discussed in another thread on here that locked up due to grit ingress over a relatively short period of time. Was there any sign of contamination or did it just fail due to use/lubrication going away?

Good to know that GBK supports Bafang parts for the Ultra for all involved. Bearing issues like this are not exclusive to the Ultra motor by any means and why Bearing Man has his business.....the upside with the Ultra is that someone handy can get the part and repair unlike the take the motor off and replace sort...which is somewhat palatable while under warranty but those don't last forever. Which once again brings me to services like Bearing Man.
 

BCBeaver

Member
That is the very area that is being discussed in another thread on here that locked up due to grit ingress over a relatively short period of time. Was there any sign of contamination or did it just fail due to use/lubrication going away?

Good to know that GBK supports Bafang parts for the Ultra for all involved. Bearing issues like this are not exclusive to the Ultra motor by any means and why Bearing Man has his business.....the upside with the Ultra is that someone handy can get the part and repair unlike the take the motor off and replace sort...which is somewhat palatable while under warranty but those don't last forever. Which once again brings me to services like Bearing Man.
No dirt ingress. It was all clean and greased with the exception of all the metal bits that smashed off and were floating around. It wasn't a bearing issue, the notches that the pawls click into to engage the cranks are smashed off. Surprisingly the pawls look fine, the leading edge may be a little bit rounded but I don't know for sure because I don't have new ones to compare to yet. I was surprised that the notches were blown out I expected to see the pawls smashed.

The bike is a Wattwagons Ultimate Commuter with a Rohloff 14 speed hub. I need to pause pedaling to shift. I know why they stripped, when I first started riding this bike I was all about pinning it off the lights. After each shift I put the power down with my legs to help accelerate as fast as possible, occasionally I would hear a crunch like noise. I thought it might be my belt skipping so I checked the tension, it was good. I thought it might be my Rohloff disintegrating under way too much power, when I changed the oil it was clean and metal free. The pause and slam power to my pedals was the problem, I suspect once it started metal bits were floating around and would occasionally interfere with one of the pawls putting more strain on the others.

I've broken pawls on a mountain bike hub when riding in a situation where I had to pause pedaling then resume with max power (riding through an uphill rock garden), the little play before engagement allowed the pawls to have some speed when they engaged so they hit harder. The mountain bike hub probably used higher quality metal for the engagement side so the pawls broke instead.

My biggest problem now is that my other commuter bike doesn't have studded tires and will be sketchy AF. As much as I don't want to I might have to ride my Moose E Fat to work, it's got studded tires and a Shimanoo E8000.
 

Jon A

Active Member
Region
USA
the notches that the pawls click into to engage the cranks are smashed off. Surprisingly the pawls look fine, the leading edge may be a little bit rounded but I don't know for sure because I don't have new ones to compare to yet.
Any chance you could take a pic of that?

Good to know that GBK supports Bafang parts for the Ultra for all involved. Bearing issues like this are not exclusive to the Ultra motor by any means and why Bearing Man has his business.....the upside with the Ultra is that someone handy can get the part and repair unlike the take the motor off and replace sort...which is somewhat palatable while under warranty but those don't last forever. Which once again brings me to services like Bearing Man.
That was definitely one of the attractions for me in getting a Bafang powered bike. The control--if something breaks, buy the parts and fix it. If all else fails, one can buy a complete replacement motor ready to bolt in for less than you'd need for a replacement battery for some high-end bikes.
 

theemartymac

Well-Known Member
No dirt ingress. It was all clean and greased with the exception of all the metal bits that smashed off and were floating around. It wasn't a bearing issue, the notches that the pawls click into to engage the cranks are smashed off. Surprisingly the pawls look fine, the leading edge may be a little bit rounded but I don't know for sure because I don't have new ones to compare to yet. I was surprised that the notches were blown out I expected to see the pawls smashed.

The bike is a Wattwagons Ultimate Commuter with a Rohloff 14 speed hub. I need to pause pedaling to shift. I know why they stripped, when I first started riding this bike I was all about pinning it off the lights. After each shift I put the power down with my legs to help accelerate as fast as possible, occasionally I would hear a crunch like noise. I thought it might be my belt skipping so I checked the tension, it was good. I thought it might be my Rohloff disintegrating under way too much power, when I changed the oil it was clean and metal free. The pause and slam power to my pedals was the problem, I suspect once it started metal bits were floating around and would occasionally interfere with one of the pawls putting more strain on the others.

I've broken pawls on a mountain bike hub when riding in a situation where I had to pause pedaling then resume with max power (riding through an uphill rock garden), the little play before engagement allowed the pawls to have some speed when they engaged so they hit harder. The mountain bike hub probably used higher quality metal for the engagement side so the pawls broke instead.

My biggest problem now is that my other commuter bike doesn't have studded tires and will be sketchy AF. As much as I don't want to I might have to ride my Moose E Fat to work, it's got studded tires and a Shimanoo E8000.
Which gen motor is it? UART or Canbus plugs?

If it's a UART motor, sounds like a great candidate for one of the improved tunes. My update with the Frey Tune completely eliminated the surging and hammer-down on acceleration. Very smooth now.
 

BCBeaver

Member
I don't know which gen it is. I assume UART. I reprogrammed it a couple months ago to a "someone's smooth tune" I found here but the damage was already started. The damage was because as I was pinning it to get to a reasonably safe traffic speed (throttle is one of the best safety features of a vehicle because you're just gone) I would release the throttle, shift, then pin the throttle and hammer pedals at the same time. The motor would spin sooner than my pedals so it would take a 1/4 stroke to catch my pedals up to the motor. That 1/4 stroke would allow a bit of interface speed so when thing meshed they did it violently. I stopped doing that but it was already on stressed and damaged.
 

theemartymac

Well-Known Member
Yup. the Ultra is just a bit too powerful for conventional drivetrain parts. It can be managed, but you have to be on top of it from day one. I shredded my first drivetrain pretty quickly by being a little to fast and loose with it, but the second is doing far, far, better.

A minor inconvenience for that abundant power though...
 

BCBeaver

Member
Any chance you could take a pic of that?


That was definitely one of the attractions for me in getting a Bafang powered bike. The control--if something breaks, buy the parts and fix it. If all else fails, one can buy a complete replacement motor ready to bolt in for less than you'd need for a replacement battery for some high-end bikes.
I had it all "reassembled," taped up and stuffed in a box before I saw the photo request, I'll take some photos when the parts arrive & I put it back together.
 

JRA

Well-Known Member
I have only got about 50 miles of ride time on an Ultra so far and am thankful for all the warnings I had in advance about possible preventable faults.

I chose a derailleur based system because it is what I understand but after some rides have come to the conclusion that having a tight gear ratio is a good thing, at least how the stock programming is set up, as it rewards am acitve spin to keep me on top of the motor which is fine with me. In stock form there is plenty of runout that makes the shift for you while you back off pressure on the cranks. Although I have a shift sensor coming I doubt I will use it.

I can see exactly the possibilities that the OP presents due to the combined backlash of the rear hub, at least on my bike, and the cranks that don't engage very smoothly either. For rear hubs traditionally the more pawls of engagement you have the better. Not sure what my stock hub has but a known favorite is the DT350 that has 36t of engagement.

It would be interesting to know the specs on the Ultra pawl system? But whoever said they should have used a sprag clutch is probably right? I'll look forward to your pics also BCBeaver.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
Regarding clutch types, thought here is needs may change with the amount of power, your riding style, and rider experience. That's going to be a player as well.

I'm no engineer but it would seem the sprag (roller) type may not hold up to occasional/accidental shock loads that are bound to happen with this kind of power. They work well in automotive automatic transmissions, but there are clutches in play to take up shock loads in that application. Used to use them in and ATV application where 2 of them would each drive a front wheel. We broke the alum. roller cages pretty regular there. When 4wd turns to 3 wheel (2 rear, w/1 front) unexpectedly, things often got interesting.....

DT350's are expensive as hell, but look like a good plan if you are going to be riding hard. Not sure how necessary something like that would be for casual riders.

Anyway, I'm an old man riding my Ultra well within it's design limitations, not pushing it at all, and happy to report everything is working fine here. -Al
 

JRA

Well-Known Member
I should mention here that I had a different sort of pedal engagement on today's ride. As I was exiting a trail on relatively smooth well packed gravel I was heading into a left hand corner posting with my right foot in the down position without pedaling. My suspension must have compressed enough to allow the pedal to dig into the ground which effectively brought the bike to a halt and myself falling off to the side and landing somewhat heavily on my thigh....

Nothing broken on me or bike, except the handlebars tweaked a little although tight, but I could feel my thigh ache a bit. I continued on with my ride and did so for another 16 miles but all the time I was very concious of not doing that again and only posting at level position or 4 and 2 at worst.

I do have a bike with 160mm of travel and am aware of pedal strikes with my 170mm cranks as far as general side snakes on the trail type of strikes which I haven't been having but am switching to 155's as soon as they get here.