The real argument against Direct Drive Front hubs

[Dan K]

I just want to chime in here that you don't have to be "Joe 6 pack with no mechanical skills" to go over the bars. I've been building my bikes, component by component, since I was a wee lad. I do 90% of the wrenching on my truck, and 100% of the wrenching on my dirt bike. Top ends, carbs, etc. I race RC trucks, which I build piece by piece. I fly RC planes and do aerial photography, and I build my planes from glider-only kits, building the kit and choosing each component. I also don't drink. So, in short, I'm not drunk when I work on my shit, I do know bikes inside and out, and I am far more mechanical than your average Joe. That said, I lost a front wheel today, and went over the bars as a result. I had been tightening my axle nuts daily, and carrying the wrench with me (as well as the charger). I had steel forks. I think what happened is the force of the motor actually spread the dropouts, although I have not verified that yet. What I have verified are my injuries, and the very expensive damage to my e-bike. Just throwing it out there.

Dan I hope you were not seriously hurt.

What kind of setup did you end up getting? If you got a 408 and that happened to you I'm REAL nervous now.

Bill

I'm not too bad off, the bloody spots will heal before the sprained thumb. I think the hurt of no longer having an e-bike, the $ spent for just a couple weeks fun and the damage to the donor bike will last longer than the injuries.

it was the worldwide electric bikes kit, I had a test version of sorts. It still wasn't free, nor were the clothes and forks destroyed in the crash. I believe you have torque-arms on your kit, correct? If so, you should be OK. I was running a review kit, so I was testing the "locking" washers that came with the kit. Not fair to test an "everything you need" kit with stuff added, although in retrospect I wish I'd said heck with it and added torque arms anyway.

 

[dogman dan]

Dan, if you are tightening your axle nuts daily, that's a BIG RED FLAG, that the fit of the hub on the dropouts has a problem. The force of the nuts on the washers will slowly spread dropouts if the fit is bad. This is well known by ebike professionals. I'm sorry you weren't aware of that, but it's a big forum and it takes months to read it all. I tried to make some of this clear in the first pages of my aotema review, but maybe we need a thread just on hub fit on dropouts in the tech section.

I find that when installing a virgin motor and washers on virgin dropouts, you can tighten them some more one time. After that, they won't loosen for thousands of miles. 2000 for me. Coming up on 1000 miles with no loose nuts on the current motor. A good fit on a front hub is far more important than torque arms. With a poor fit, you are lucky to go around the block before you head over the bars.

Too bad you had to get such a lousy introduction to ebikes. My first ride ended similar, though I didn't go over the bars. Also having multiple bikes laying around, I put the motor on the handiest one, and promptly spread the dropouts, cut the wires, smoked a controller. The second try, I had a more suitable set of forks. My rule of thumb now, is forget any dropout that takes a quick release hub. Justin at ebikes ca now sells a special washer for quick release lawyer lips on dropouts.

 

[Dan K]

Dan K. wrote:

I had been tightening my axle nuts daily, and carrying the wrench with me (as well as the charger). I had steel forks.

Dan, did you have any torque arms on your axle? Sorry to hear about your accident, but as a knowledgeable mechanic you should have known something was wrong if you always had to tighten the axle nuts. I had a similar problem on my very first e-trailer, and was lucky to only ruin some spokes when the wheel folded under the trailer. Since then I have been putting torque arms on everything and have had no further problems.

No, I did not, and I knew that it was an issue. Actually, the forks were chromoly, which is stronger than steel - my mistake in the original post. Since I was "testing" a new kit for the vendor/manufacturer, I was running it as it came, rather than making my own additions. The axle nuts also didn't tighten much each time, just a hair at most. Still, I did know it was an issue, and should have put torque arms on it. I actually planned to, but as I was reviewing a kit that was supposed to include everything you needed, I was in no rush to install them.

Details on the whole thing can be had here... the last couple posts detail everything.
http://endless-sphere.com/forums/viewtopic.php?f=4&t=9707&start=30

 

[Dan K]

Dan, if you are tightening your axle nuts daily, that's a BIG RED FLAG, that the fit of the hub on the dropouts has a problem. The force of the nuts on the washers will slowly spread dropouts if the fit is bad. This is well known by ebike professionals.

I find that when installing a virgin motor and washers on virgin dropouts, you can tighten them some more one time. After that, they won't loosen for thousands of miles. 2000 for me. Coming up on 1000 miles with no loose nuts on the current motor. A good fit on a front hub is far more important than torque arms. With a poor fit, you are lucky to go around the block before you head over the bars.

I suppose I should have been more clear. I was checking them daily, not necessarily tightening them daily. That said, I had to tighten them more than twice, and that should have been enough to let me know. I actually planned to install torque arms this weekend, but as I said in my previous 2 replies, I was testing a kit that should have worked as is so I wanted to test it that way. As dissapointed as I am about the crash, the injuries, the toasted battery and forks etc. it could have been worse. I'm glad I wasn't doing 23MPH alongside traffic at the time.

 

[dogman dan]

Were they lawyer lip forks? On of the things I like about the cheap bikes is the big flat dropouts.

 

[Dan K]

Were they lawyer lip forks? On of the things I like about the cheap bikes is the big flat dropouts.

Not as you'd expect, since the original wheels were bolt-on and not QR. At the same time, they were not the huge flat mount points of some ultra-cheap bikes.

 

[dogman dan]

Well well well. That one sure snuck up on ya then didn't it? Usually this story is told by the one who had the cup shaped quick release dropouts. I appreciate my cheap 1" headset, trash suspension forks more and more. They seem to really have a bulldog of a dropout.

At least you didn't go to the e room. When I went over the bars last summer, I broke both collarbones, seperated a shoulder, and dislocated another. The bones healed, but I have a few years to go to heal the joints. I had a bike with a funny waterbottle mount. Use only when stopped. pulling it moving, i stuffed the bottle into the forks, and wheeee! Torque arms don't fix that problem.

 

[Dan K]

Well well well. That one sure snuck up on ya then didn't it? Usually this story is told by the one who had the cup shaped quick release dropouts. I appreciate my cheap 1" headset, trash suspension forks more and more. They seem to really have a bulldog of a dropout.

At least you didn't go to the e room. When I went over the bars last summer, I broke both collarbones, seperated a shoulder, and dislocated another. The bones healed, but I have a few years to go to heal the joints. I had a bike with a funny waterbottle mount. Use only when stopped. pulling it moving, i stuffed the bottle into the forks, and wheeee! Torque arms don't fix that problem.

It certainly did, and it wasn't a pleasant surprise. I'll probably need a day or two to be sure the thumb is just a sprain, but I think that's all it is. I've had my share of broken bones and injured joints, so I feel your pain there.

Looks like I need a new platform if I'm going to continue with this kit. Not sure if I'll be able to replace that BMS, if that's actually the issue, etc. If I need to start from scratch it'll require some thinking, and probably a RWD setup.

 

[fifthmass]

I'm not too bad off, the bloody spots will heal before the sprained thumb. I think the hurt of no longer having an e-bike, the $ spent for just a couple weeks fun and the damage to the donor bike will last longer than the injuries.

it was the worldwide electric bikes kit, I had a test version of sorts. It still wasn't free, nor were the clothes and forks destroyed in the crash. I believe you have torque-arms on your kit, correct? If so, you should be OK. I was running a review kit, so I was testing the "locking" washers that came with the kit. Not fair to test an "everything you need" kit with stuff added, although in retrospect I wish I'd said heck with it and added torque arms anyway.

Dear God Dan! A test pilot usually gets hazardous duty pay! Did they make you sign a waiver? Seriously I'm glad you didn't break any bones or get otherwise seriously hurt.

No I don't have torque arms but will be getting some very soon. There is a great machine shop here in Waltham near where I work. I'm going to have them milled out of 0.1 inch mild steel with an inch of steel around the axle hole. That way if the axle does spin the wheel should stay with the fork and I should retain some control. Till then I'm keeping the current under 10 amps. Still plenty of power for what I need and the exercise won't hurt either.

I'll be up at Goldleaf this evening. Swing by if you have time.

Regards,
Bill

 

[Dan K]

I'm not too bad off, the bloody spots will heal before the sprained thumb. I think the hurt of no longer having an e-bike, the $ spent for just a couple weeks fun and the damage to the donor bike will last longer than the injuries.

it was the worldwide electric bikes kit, I had a test version of sorts. It still wasn't free, nor were the clothes and forks destroyed in the crash. I believe you have torque-arms on your kit, correct? If so, you should be OK. I was running a review kit, so I was testing the "locking" washers that came with the kit. Not fair to test an "everything you need" kit with stuff added, although in retrospect I wish I'd said heck with it and added torque arms anyway.

Dear God Dan! A test pilot usually gets hazardous duty pay! Did they make you sign a waiver? Seriously I'm glad you didn't break any bones or get otherwise seriously hurt.

No I don't have torque arms but will be getting some very soon. There is a great machine shop here in Waltham near where I work. I'm going to have them milled out of 0.1 inch mild steel with an inch of steel around the axle hole. That way if the axle does spin the wheel should stay with the fork and I should retain some control. Till then I'm keeping the current under 10 amps. Still plenty of power for what I need and the exercise won't hurt either.

I'll be up at Goldleaf this evening. Swing by if you have time.

Regards,
Bill

I don’t need hazardous test pay. I don’t even need reimbursement for my injuries, or my clothes. Heck, not even really the forks, since I would apparently need a different set for this to work anyway. I’m really only annoyed about being out the $ for the battery I paid for, which in the scheme of things is only about ½ my loss… would be well under half if I took this thumb to the e-room. We’ll see what happens. I spoke with Steve @ WWB and he agrees they need a better wheel retention system and they are already working on it, so they may do something for me. I don’t know yet. I think it would be cool if they did, since they apparently already knew this was an issue and were working on it, and said issue is the only reason my battery is now toast. Regardless there will be something in the works for full-price customers, they know this is an issue and are addressing it.

On the bright side, it’s not that bad. I’m not all that hurt, it wasn’t on the most expensive of bikes (the first bike I tried to install this kit on had a $600 fork!), etc. It could have been worse. I’m working on looking at the bright side.

I’d come by the spot tonight for sure if this didn’t happen, but I was counting on the bike to get me home. Looks like I might be staying in Georgetown tonight now, since it’s a much shorter distance. We’ll see how the night unfolds, if not this time I’ll aim for next.

 

[The Stig]

The title of this thread is misleading at a toxic level. It needs to be changed to The real argument against Non-Geared Front Hubs

 

[mybad]

My front dropouts gave way this year @ 36v. When I got home I put the fw hub up for sale. done and done ....

 

[John in CR]

The title of this thread is misleading at a toxic level. It needs to be changed to The real argument against Non-Geared Front Hubs

Good point. Title changed. Happy?

John

 

[fifthmass]

Regarding new title of this thread when it comes to axle spinout you can argue that geared hubs are actually worse than DD because of the much higher low speed torque. According to ebikes.ca simulator a geared hub has almost twice the low speed torque of a DD motor of the same nominal power output.

When it comes to plug braking resulting from controller failure DD is worse than geared hubs that can freewheel.

All in all it seems that axle spin out is the more common problem of the two. With either failure mode a rear motor failure is more recoverable/survivable.

Bill

 

[Rassy]

fifthmass wrote:

Regarding new title of this thread when it comes to axle spinout you can argue that geared hubs are actually worse than DD because of the much higher low speed torque.

Good point, except, it's the rocking back and forth that is most apt to cause the problem. With the free wheeling hubbie, even if the torque is greater, pressure is only applied in one direction, hence the probability of spinning out or loosening the axle nuts is lower. Has anyone here spun out a free wheeling hubbie?

 

[aurum]

I have broken 2 front alloy forks because of my nine continents at 48V. The torque arms must be secured very tightly or the crappy alloy forks break. A Marzocchi and another SID Team fork down the tubes before I learned my lesson. I am going to try a Surly steel fork from now on.

 

[Russell]

Regarding new title of this thread when it comes to axle spinout you can argue that geared hubs are actually worse than DD because of the much higher low speed torque. According to ebikes.ca simulator a geared hub has almost twice the low speed torque of a DD motor of the same nominal power output.

When it comes to plug braking resulting from controller failure DD is worse than geared hubs that can freewheel.

All in all it seems that axle spin out is the more common problem of the two. With either failure mode a rear motor failure is more recoverable/survivable.

Bill

An axle spin-out from too much torque is most likely to occur at low speed such as on take-off or up a steep hill so while it is the more likely failure it isn't nearly as big of a safety problem as having a motor slam on the brakes at high speed. The most common cause of axle spin-outs however appear to be caused by using improper forks, not using or incorrectly installing torque arms and generally poor installations.

-R

 

[The Stig]

Regarding new title of this thread when it comes to axle spinout you can argue that geared hubs are actually worse than DD because of the much higher low speed torque. According to ebikes.ca simulator a geared hub has almost twice the low speed torque of a DD motor of the same nominal power output.

When it comes to plug braking resulting from controller failure DD is worse than geared hubs that can freewheel.

All in all it seems that axle spin out is the more common problem of the two. With either failure mode a rear motor failure is more recoverable/survivable.

Bill

An axle spin-out from too much torque is most likely to occur at low speed such as on take-off or up a steep hill so while it is the more likely failure it isn't nearly as big of a safety problem as having a motor slam on the brakes at high speed. The most common cause of axle spin-outs however appear to be caused by using improper forks, not using or incorrectly installing torque arms and generally poor installations.

-R

X2!

 

[Dan K]

Has anyone here spun out a free wheeling hubbie?

Yes, me, yesterday.

 

[Russell]

Has anyone here spun out a free wheeling hubbie?

Yes, me, yesterday.

Yeah Dan but you didn't say why...no torque arm and worst of all dropouts that were made for a larger axle
:|


-R

 

[Dan K]

Has anyone here spun out a free wheeling hubbie?

Yes, me, yesterday.

Yeah Dan but you didn't say why...no torque arm and worst of all dropouts that were made for a larger axle
:|


-R

True, but that wasn't the question - the question was has anyone, ever? The torque arms were "supposed to be" unnecessary due to the special rotation locking washer they included. I'm also still not 100% sure the dropouts were too large, although I suspect they were. The axle could not fit in unless lined up so that the flats were going in, the flats just were not as tight as it appears they needed to be.

I'm not saying it was unavoidable, almost all accidents could have been avoided. I was merely stating that it happens. I doubt I was the first, and doubt I will be the last. As mentioned elsewhere, I'm sure when that happens to a lot of people (I imagine lawyer lips and aluminum forks are a huge issue for this) they don't post up about it, or follow the board, they probably just give up on e-bikes.

 

[Russell]

True, but that wasn't the question - the question was has anyone, ever? The torque arms were "supposed to be" unnecessary due to the special rotation locking washer they included. I'm also still not 100% sure the dropouts were too large, although I suspect they were. The axle could not fit in unless lined up so that the flats were going in, the flats just were not as tight as it appears they needed to be.

Those anti-rotation/torque washers aren't all that much help on front forks. First of all my dropouts like many others aren’t deep enough for the tab on the washers to fall within the dropout and second because the axle will torque CW when power is applied (as viewed from the left side) the tab would be pushing on the dropout where it is weaker and tend to spread it open. I think because the washers are closed around the axle instead of an open slot they help if the nuts are tight but otherwise they don't do all that much. For proper fit the axle must be absolutely snug with the flats parallel with the dropout. Even the act of tightening the nuts can rotate the axle if you don’t take care. I recommend using two wrenches to tighten both sides simultaneously or tighten one side a little then the other and repeat. If there is any slop in the fit or the axle starts out skewed in the dropout it won’t take much force to rotate it further and spin it.

Torque arms will definitely help but they need to be installed correctly. On front forks they could as some say be mounted on the front but the preferred side is the back. The reason for this is once again there can’t be any slop in the fit. Any play in the torque arm about the axle, and there is always a little bit, needs to be taken out and that is most easily done by securing the arm to the rear of the forks and tightening the hold-down clamp to take up any slack. To do otherwise is like constructing another dam a few feet from a potentially weak dam instead of shoring up the first dam. The first dam will still probably fail when stressed and the water will have momentum when hitting the next new dam.

-R

 

[Dan K]

True, but that wasn't the question - the question was has anyone, ever? The torque arms were "supposed to be" unnecessary due to the special rotation locking washer they included. I'm also still not 100% sure the dropouts were too large, although I suspect they were. The axle could not fit in unless lined up so that the flats were going in, the flats just were not as tight as it appears they needed to be.

Those anti-rotation/torque washers aren't all that much help on front forks. First of all my dropouts like many others aren’t deep enough for the tab on the washers to fall within the dropout and second because the axle will torque CW when power is applied (as viewed from the left side) the tab would be pushing on the dropout where it is weaker and tend to spread it open. I think because the washers are closed around the axle instead of an open slot they help if the nuts are tight but otherwise they don't do all that much. For proper fit the axle must be absolutely snug with the flats parallel with the dropout. Even the act of tightening the nuts can rotate the axle if you don’t take care. I recommend using two wrenches to tighten both sides simultaneously or tighten one side a little then the other and repeat. If there is any slop in the fit or the axle starts out skewed in the dropout it won’t take much force to rotate it further and spin it.

Torque arms will definitely help but they need to be installed correctly. On front forks they could as some say be mounted on the front but the preferred side is the back. The reason for this is once again there can’t be any slop in the fit. Any play in the torque arm about the axle, and there is always a little bit, needs to be taken out and that is most easily done by securing the arm to the rear of the forks and tightening the hold-down clamp to take up any slack. To do otherwise is like constructing another dam a few feet from a potentially weak dam instead of shoring up the first dam. The first dam will still probably fail when stressed and the water will have momentum when hitting the next new dam.

-R

I don't disagree with any of this. I was just pointing out that I installed a kit as it came, as many come, and it failed in the method described. I've learned my lesson, and will not use a FWD system without torque arms again. Period. However, I'd be willing to bet dollars against donuts that someone, somewhere, sometime in the future will repeat my mistake & mishap, and I'd make the same bet I'm not the first person it has happened to. When ordering my new fork I will also order torque arms, I'm just waiting for verification that a new battery is on the way before I do this. I'm sure it will be, Steve @ worldwide electric bikes has been very supportive and more than willing to stand behind his products. He told me that even if the manufacturer did not cover the battery he would, since he does not sell anything he is not willing to stand behind. A stand-up guy from my experiences with him. Unfortunately, I did learn the lesson you're telling the hard way, and like I said, i'd bet I'm not the first or the last.