spinningmagnets
100 TW
Whether its 2WD or just a single hub motor, I don't like the Direct Drive (DD) hubs on the front. Aluminum rim with a double-wall for strength, stainless steel nipples...
Epic rim failure. Why?
- Thread starter Rifle
- Start date
recumpence
1 GW
The basic truth of hub motors is; the heavy motor puts ENORMOUSE stress on the rim and spokes from jarring. Also, potholes are completely different than downhill riding. Downhilling is primarily jumping and landing. Landing from a jump puts a relatively spread out load on the rim from landing on flat (or relatively flat) ground. However, potholes put all the stress on one sharp point on the rim.
I am not a fan of front wheel drive at all. My personal opinion is that driving the front wheel should only be done on a relatively slow bike for additional traction (like a fat bike for snow, for instance). Every possible step should be taken to minimize any potential problem with a front wheel. If this happened with the rear wheel it is much more surviveable. A front wheel failure is catastrophic.
Matt
I am not a fan of front wheel drive at all. My personal opinion is that driving the front wheel should only be done on a relatively slow bike for additional traction (like a fat bike for snow, for instance). Every possible step should be taken to minimize any potential problem with a front wheel. If this happened with the rear wheel it is much more surviveable. A front wheel failure is catastrophic.
Matt
MadRhino
100 GW
It was obvious that it would fail, long before this happened. You just didn't notice because "maintenance schedule" was not part of your bicycle vocabulary. Now it should be, for there is nothing like a crash that is caused by negligence, to teach proper maintenace. :wink:
rider95
1 kW
Did you keep an eye on the spokes?? If they got lose and you didn't catch it and tite em could have caused it
spinningmagnets said:
This was a double wall aluminum rim with stainless steel nipples
.MadRhino said:
I searched this winter for a list I once had of the various periodic maintenance that should be done to see if there was anything important I was missing, but I wasn't able to find the one I liked, and I didn't encounter anything I saw that needed attention, but as I said I wasn't aware spoke tension was so important, so it may have been on there but I didn't realize the importance. Part of why I didn't put more maintenance into the bike in general is that I have muscular problems that make it so I'm only able to be on a my feet so much in a day: if I grocery shop and cook, that's about all I can do for the day. Other part of why I didn't do more maintenance is I kept thinking I was going to build a new ebike soon. But anyways, maintenance is obviously going to be higher up on the priority list. Still wish I could find a maintenance schedule that lists the potential consequences that can arise with each component. Anyone have one?
recumpence said:
I think people are forgetting the wonder of TIRES! They will spread out the stress of hitting a pothole or anything out offering a huge reduction in stress to the rim. And as has been pointed out, wheels that don't have suspension have 10+ times that amount of un-sprung weight on them and they manage just fine. Motors do cause quite a bit of torque, but regular bikes would still experiences similar forces when braking. The big difference is just the consist high speeds that can be traveled. But I believe the rim would have been fine if the spokes had not been loose for months. I've determined the noise I was hearing was very likely the spokes rubbing against each other as the wheel turned, and given the sound I heard, it seems very likely that the majority of spokes were quite loose.
This crash probably wouldn't have gone much better if I had a rear hub. I didn't or flip or anything. Just fell to the side. Pretty hard to stay upright regardless of which wheel that happens to.
recumpence
1 GW
Your thinking is incorrect on this........
First, we are not dealing with rotational torque at all. I have a bike pulling over 30,000 watts through 32 15 gauge spokes. Rotational torque does not brake spokes or rims (or it takes an ENORMOUSE amount of power to do it).
Second, the weight of a hub motor is WAAYYYY harder on spokes and rims than the weight of a bike inside the frame or from the rider. This is not an issue of unsprung weight, it is an issue of dampening between the weight and the spokes. In the case of a heavy rider and his weight transferring into the spokes, you have to realize the rider's weight is suspended by his legs (if standing) or the fat in his butt (if sitting). The weight, then, goes through the seat of the bike (or pedals), through the frame (which has some flex), through the dropouts, through the axle, through the hub and finally into the spokes. Then, as you mentioned, there is the tire that adds a bit of give to the equasion. In the case of a hub motor, any jarring from road imperfections ONLY has the tire to dampen it. After the tire, the load goes directly into the spokes with NOTHING else to absorb the load, thus very easliy popping spokes and/or braking the rim.
I hit potholes all the time with rigid bikes to the point of getting pinch flats regularly, yet I have never popped a spoke or damaged a rim. Conversely, popping spokes is a regular occurance with hub motors......
Lastly, in my many years of bike and motorcycle riding, I have had multiple lock up issues with the rear wheel and had to skid to a stop. It is many times easier to hang on with rear wheel issues than front wheel issues. Yet, I am missing cartillage in my left knee from the ONE time I had a front wheel lock up while riding.
Matt
First, we are not dealing with rotational torque at all. I have a bike pulling over 30,000 watts through 32 15 gauge spokes. Rotational torque does not brake spokes or rims (or it takes an ENORMOUSE amount of power to do it).
Second, the weight of a hub motor is WAAYYYY harder on spokes and rims than the weight of a bike inside the frame or from the rider. This is not an issue of unsprung weight, it is an issue of dampening between the weight and the spokes. In the case of a heavy rider and his weight transferring into the spokes, you have to realize the rider's weight is suspended by his legs (if standing) or the fat in his butt (if sitting). The weight, then, goes through the seat of the bike (or pedals), through the frame (which has some flex), through the dropouts, through the axle, through the hub and finally into the spokes. Then, as you mentioned, there is the tire that adds a bit of give to the equasion. In the case of a hub motor, any jarring from road imperfections ONLY has the tire to dampen it. After the tire, the load goes directly into the spokes with NOTHING else to absorb the load, thus very easliy popping spokes and/or braking the rim.
I hit potholes all the time with rigid bikes to the point of getting pinch flats regularly, yet I have never popped a spoke or damaged a rim. Conversely, popping spokes is a regular occurance with hub motors......
Lastly, in my many years of bike and motorcycle riding, I have had multiple lock up issues with the rear wheel and had to skid to a stop. It is many times easier to hang on with rear wheel issues than front wheel issues. Yet, I am missing cartillage in my left knee from the ONE time I had a front wheel lock up while riding.
Matt
goodgnus
100 mW
- Joined
- May 14, 2012
- Messages
- 49
As a bike mechanic, my opinion is that ebikes need fatter tires in general. Especially as speeds increase. Larger air volume decreases the spike loads from hitting pavement lips, curb edges, potholes, etc.
Ebikes also need to be inspected regularly. If indeed there was galvanic corrosion at the nipples that would weaken the wheel notably, leading to the catastrophic failure you experienced after hitting a pothole.
I'm running a mid drive on a 29+ bike (29x3" tires). To me this is an excellent platform for ebikes, much better than 26 fatty tires.
I would suggest running as wide a tire as will fit in your frame.
Ebikes also need to be inspected regularly. If indeed there was galvanic corrosion at the nipples that would weaken the wheel notably, leading to the catastrophic failure you experienced after hitting a pothole.
I'm running a mid drive on a 29+ bike (29x3" tires). To me this is an excellent platform for ebikes, much better than 26 fatty tires.
I would suggest running as wide a tire as will fit in your frame.
Ah, dampening, good point.
If this had happened on the back instead of front I would have been able to steer better and maybe stay up longer, but I think anyone would have to expect they're going to go down if that mess is hanging onto their back hub.
Anyways, the main moral of the story here is to check your spoke tension and make sure you figure out the source of any unusual noise your bike starts to make.
If this had happened on the back instead of front I would have been able to steer better and maybe stay up longer, but I think anyone would have to expect they're going to go down if that mess is hanging onto their back hub.
Anyways, the main moral of the story here is to check your spoke tension and make sure you figure out the source of any unusual noise your bike starts to make.
recumpence
1 GW
Good call...... :wink:
Game on.
Matt
Game on.
Matt
John in CR
100 TW
Rifle said:
You need to see the pic of what LFP did to a rear wheel. I believe he was riding with one hand, and carrying lunch for everyone in the other. His wheel looked like yours, but being on the rear, he arrived with himself and the food intact.
MadRhino
100 GW
Rifle said:
Well, I guess every rider has his own, for they all ride different bikes and components on different terrain, with various level of performance and aggressivity... With consequences accordingly, imagine this "incident" of your's happening in a mountain trail at 50 Mph. Hard riders are having their maintenance agenda reminders written in their skin and bones.
Brakes, wheels and steer inspection should be often for anyone. Bikes are not very forgiving in that matter. :wink:
Because of the heavy loads I often enough have, and the unpredictable nature of road damage and detours here, as well as the usually-well-used nature of stuff I build things from, I check my wheels and stuff before every ride. Whenever I have not, I have paid for that with problems of one sort or another, though so far not to the point of being unable to ride home (cautiously, though, sometimes). 
It's been a long time, so my memory is hazy, but I don't think Liveforphysics' rim actually broke apart like this one did, though the failure was certainly right up there with the worst I've ever seen. :lol:
As for the actual reason for this rim failure, based on the single pic provided, and my own experiences with these "champion" rims, I'd say that the nipple holes corroded and stress cracked (allowing even more surface area to corrode) so that on this last pothole some of the nipples/spokes just pulled right thru the rim's nipple holes, and the sudden change in loading and tension caused/allowed the rim itself to just collapse along pre-existing cracks radiating from other nipple holes.
I have at least two of those rims with very obvious cracks radiating out from several of the nipple holes, in 26". I think there is a 20" with barely visible ones on a couple of the holes. I'm sure there are many more cracks I can't see.
Armchair failure analysis mode:
I think that the largest contributor to the cracks is that in order to almost-sufficiently tension the too-thick 12g spokes they come with, so much pressure is put on the unreinforced nipple holes in the rim that they just don't have any give left for even just a *little* road-bump absorption, even when used with (cheap) suspension forks and 2"+ tires.
So every bump stresses the associated nipple holes, and eventually some get stressed enough they begin cracking.... Then teh spokes are looser as the nipple hole is pulled by the stresses, and expands a little bit toward the hub, away from the nipple's seating edge, and then if you tighten that up it puts even more stress on that hole, and they cycle accelerates.
At that point, a failure will eventually happen if ridden long enough, especially if you have to keep tightening spokes to fix the problems the cracks allow.
It is possible (probably likely) that if normal spokes (14-15g, or 13/14butted, etc) were used, these kinds of failures on this class of rim would not happen as much / as quickly, as the spoke tension would not need to be so high, and the rim might have enough elasticity to survive the bumps/etc.
But a rim with eyelets might be a better choice, even then. (unfortunately there are people that buy a better rim with eyelets, then drill out the eyelets to use too-thick spokes on them...might as well have stuck with the cheap rim to start with).
And a good quality rim with eyelets, that is designed for thicker spokes and higher tensions, would almost certainly be a better choice if using these 12G+ spokes. :/
John in CR said:
It's been a long time, so my memory is hazy, but I don't think Liveforphysics' rim actually broke apart like this one did, though the failure was certainly right up there with the worst I've ever seen. :lol:
As for the actual reason for this rim failure, based on the single pic provided, and my own experiences with these "champion" rims, I'd say that the nipple holes corroded and stress cracked (allowing even more surface area to corrode) so that on this last pothole some of the nipples/spokes just pulled right thru the rim's nipple holes, and the sudden change in loading and tension caused/allowed the rim itself to just collapse along pre-existing cracks radiating from other nipple holes.
I have at least two of those rims with very obvious cracks radiating out from several of the nipple holes, in 26". I think there is a 20" with barely visible ones on a couple of the holes. I'm sure there are many more cracks I can't see.
Armchair failure analysis mode:
I think that the largest contributor to the cracks is that in order to almost-sufficiently tension the too-thick 12g spokes they come with, so much pressure is put on the unreinforced nipple holes in the rim that they just don't have any give left for even just a *little* road-bump absorption, even when used with (cheap) suspension forks and 2"+ tires.
So every bump stresses the associated nipple holes, and eventually some get stressed enough they begin cracking.... Then teh spokes are looser as the nipple hole is pulled by the stresses, and expands a little bit toward the hub, away from the nipple's seating edge, and then if you tighten that up it puts even more stress on that hole, and they cycle accelerates.
At that point, a failure will eventually happen if ridden long enough, especially if you have to keep tightening spokes to fix the problems the cracks allow.
It is possible (probably likely) that if normal spokes (14-15g, or 13/14butted, etc) were used, these kinds of failures on this class of rim would not happen as much / as quickly, as the spoke tension would not need to be so high, and the rim might have enough elasticity to survive the bumps/etc.
But a rim with eyelets might be a better choice, even then. (unfortunately there are people that buy a better rim with eyelets, then drill out the eyelets to use too-thick spokes on them...might as well have stuck with the cheap rim to start with).
And a good quality rim with eyelets, that is designed for thicker spokes and higher tensions, would almost certainly be a better choice if using these 12G+ spokes. :/
I'd agree with that.
Hub motor wheels tend to fail because of the weight of the motor? Or because they tend to be poorly built? Drum brake wheels are also heavy, yet don't see, to suffer the same fate?
Doubtless the forks/frame on a rigid does have a little "give", but a heavy hub should be bearable by a properly build with wheel, with multiple spokes in their elastic region distributing impact forces over a considerable portion of the rim.
Hub motor wheels tend to fail because of the weight of the motor? Or because they tend to be poorly built? Drum brake wheels are also heavy, yet don't see, to suffer the same fate?
Doubtless the forks/frame on a rigid does have a little "give", but a heavy hub should be bearable by a properly build with wheel, with multiple spokes in their elastic region distributing impact forces over a considerable portion of the rim.
e-beach
10 MW
Sorry you are hurt! But, please just go and see a doctor if you can. Like others, I have had 2 bad e-bike accidents, fractured a rib in one of them.......I feel your pain which is why you should see a doctor to find out if something can be done to help you heal faster. Your pain is our pain.
My question is, were the spokes loose due to the non-occasional maintenance, or because the micro-fractions that happened over time led to the loosing of the nipple seats?
Could hot and cold weather caused the various metals in your rim to stretch and crack as the got cold and hot?
Was it over tightened originally causing fracturing?
I am agreeing with the "over the life of the rim fatigue" theory. Your rim probably had lots of fractures that finally gave way.
Maybe it was just a poorly made rim and your bad luck to end up with it. The Champion rim I got with my Yescomusa front hub motor seems to be doing fine, well into my 7000 miles of big city street riding, pot holes and all the other junk.
Moral of the story: Time to budget time to inspect the rims more often and if you see a crack or cracks around the rim, have a money reserve to replace the rim.
Get well soon!
My question is, were the spokes loose due to the non-occasional maintenance, or because the micro-fractions that happened over time led to the loosing of the nipple seats?
Could hot and cold weather caused the various metals in your rim to stretch and crack as the got cold and hot?
Was it over tightened originally causing fracturing?
I am agreeing with the "over the life of the rim fatigue" theory. Your rim probably had lots of fractures that finally gave way.
Maybe it was just a poorly made rim and your bad luck to end up with it. The Champion rim I got with my Yescomusa front hub motor seems to be doing fine, well into my 7000 miles of big city street riding, pot holes and all the other junk.
Moral of the story: Time to budget time to inspect the rims more often and if you see a crack or cracks around the rim, have a money reserve to replace the rim.
Get well soon!
Ykick
1 GW
goodgnus said:
Very much agree! Quality rim/spokes too...
Chalo
100 TW
Punx0r said:
Think of it in terms of peak forces. The frame and especially the fork have a measure of flex to clip the peaks off of bumps. The wheel has very little. The rider is a big loose bag of flex compared to every other part of the system.
I'm reminded of the first e-bike I built, which had 40-some-odd pounds of lead batteries hard attached to a sturdy rear rack. Somehow that amount of uncompliant dead weight positioned directly on top of struts over the rear axle did more to wreck the rear wheel than much larger amounts of weight as items in panniers.
Pound for pound, the human body is a very forgiving kind of weight for your wheels to carry. But there is no less compliant mass that you can put on a bicycle wheel than one located in its own hub.
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