Hub mid-drive dual motor combos

[Chalo]

Although it is somewhat disturbing to me that fat bikes have such wide q factors.......having fat bike rear spacing doesn't necessarily mean the q factor has to be so wide.

Well, chainline isn't negotiable once it starts to foul the tire. And since every feckless poser in the world has to have at least 11 sprockets back there now, the cassette width isn't very flexible either. Frankly I'm a little surprised that the BB can be shaved down to 83mm and still work with 100mm fat tires and derailleur gearing. But that Otso bike isn't as greedy for short chainstays as most.

The original fatbike, Hanebrink Extreme Terrain, was immune to the factors that result in wide Q.

Hanebrink Extreme Terrain: The First Production Fat Bike

Released in 1991, the Hanebrink Extreme Terrain might be the most radical bike ever to land on Earth. Discover its fascinating history...

bikepacking.com

Here's a new bauble to distract folks who must take things to foolish extremes:

Surly Moonlander | The Largest Fat Tire Bike | Worlds Biggest Fat Bike

The Surly Moonlander is the most capable fat tire bike ever created. Featuring this worlds widest bike tires

surlybikes.com

24 x 6.2" tires! Who will be the first to put in a pair of All Axle hub motors?

 

[hillslayer@]

I can't see a downside to DD hub mid-drive combo superior hill climbing without overheating either motor, using the DD hub for all high speed and none uphill work saves wear on the drivetrain. Side covers breaking is more from bearing failure than design problems.

 

[Chalo]

Side covers breaking is more from bearing failure than design problems.

Then you're not a mechanical engineer, because that failure is foreseeable. A thin flat aluminum casting with a cantilevered bending load in the middle, as far as possible from all its attachment points. It's remarkable that they don't all break eventually-- but it's probably more of a testament to how much/little folks actually pedal their e-bikes. And also to how barely-good-enough is still good enough.

 

[hillslayer@]

Then you're not a mechanical engineer, because that failure is foreseeable. A thin flat aluminum casting with a cantilevered bending load in the middle, as far as possible from all its attachment points. It's remarkable that they don't all break eventually-- but it's probably more of a testament to how much/little folks actually pedal their e-bikes. And also to how barely-good-enough is still good enough.

Your not a mechanical engineer either I pulled the side cover looks pretty well built to me. How many miles do I have to put on this before you admit your wrong. It's not like I have been taking it easy on it pedal assist 9 on anything steep.

 

[Chalo]

Your not a mechanical engineer either I pulled the side cover looks pretty well built to me. How many miles do I have to put on this before you admit your wrong.

All the ones I've opened have wrong material/wrong geometry for what can approach 1000 pounds of chain tension in some gearing scenarios. But you can decide it looks pretty well built if that makes you happy.

 

[neptronix]

We've seen tons of side plates shear from pedal power on this forum.
..and yeah, few people actually pedal, so that rate is pretty high.

Good luck, but i wouldn't recommend it until you have a few thousand miles on the odo!

 

[hillslayer@]

We've seen tons of side plates shear from pedal power on this forum.
..and yeah, few people actually pedal, so that rate is pretty high.

Good luck, but i wouldn't recommend it until you have a few thousand miles on the odo!

If the bearing on the cover fails l can see it taking out the cover. It's probably worth it to pull it and check that bearing once a year or so.

 

[neptronix]

it's not really a bearing problem when these fail, it's the side cover shearing in half and leaving you with a wobbly wheel.
Basically a matter of aluminum fatigue on a side cover that's weak to begin with ( they expect the rider to be pedaling less when they design these things )

You can't inspect for aluminum fatigue w/o very expensive equipment.
The taller the motor, the worse the problem.

 

[scianiac]

Man 7 pages in and I still don't see any real reasoning that this is better than just using an appropriately sized motor. Every combination of hub motor and mid-drive for the same weight would be worse in just about every way than one or the other appropriately used. If a given motor doesn't have power to think that adding a second type of motor with a second controller and often second gear reduction is better than the same weight as both of those devoted to one motor is silly. Let alone the tried and true method of just putting more power into a motor. Like if a BBSHD isn't enough power a controller swap to boost the power will add a lot of power for no additional weight.

Are there some weird edge cases you could get a setup like to be more efficient, probably, but most of the time 1 larger motor will probably be more efficient unless you are heavily under utilizing it. And that's not considering you could use a motor that was say 50% larger, have the same power as the two motors and spend that rest of the weight on more battery.

Maybe it's this thing that for some reason people want a bike that both can provide 100w while they pedal along at 10mph and be a 8kw monster sometimes and to be super efficient at the same time. Figure out what you want the bike to do is size things accordingly, which is not always easy but you can normally get close enough with some planning.

 

[hillslayer@]

Man 7 pages in and I still don't see any real reasoning that this is better than just using an appropriately sized motor. Every combination of hub motor and mid-drive for the same weight would be worse in just about every way than one or the other appropriately used. If a given motor doesn't have power to think that adding a second type of motor with a second controller and often second gear reduction is better than the same weight as both of those devoted to one motor is silly. Let alone the tried and true method of just putting more power into a motor. Like if a BBSHD isn't enough power a controller swap to boost the power will add a lot of power for no additional weight.

Are there some weird edge cases you could get a setup like to be more efficient, probably, but most of the time 1 larger motor will probably be more efficient unless you are heavily under utilizing it. And that's not considering you could use a motor that was say 50% larger, have the same power as the two motors and spend that rest of the weight on more battery.

Maybe it's this thing that for some reason people want a bike that both can provide 100w while they pedal along at 10mph and be a 8kw monster sometimes and to be super efficient at the same time. Figure out what you want the bike to do is size things accordingly, which is not always easy but you can normally get close enough with some planning.

This will help you out - YouTube

 

[neptronix]

I'm also in the big single motor camp.
Less complexity is good!

But i did show you can combine the DD and the geared motor to get an effective big power density gain when climbing.

I always prefer single motor and the smallest wheel i can get away with to gear it down ( increasing the power density and efficiency )

 

[scianiac]

This will help you out - YouTube

I'm not sure you actually paid attention to the video. The first half is Justin explaining how it's normallly not a good idea. Then he gives some reasons why you might want to do it, most of those are not the ones talked about in this thread. We aren't talking about weird vehicle designs or about driving multiple wheels.

Redundancy is debatable as making something that is redundant while also making the whole system less reliable and more complex defeats the purpose. In general electric motors are extremely reliable and if you want something that is reliable you should address the reasons why ebike motors fail not just slap another motor on while not addressing the issues with it either.

In terms of power I honestly think Justin is somewhat wrong, he's kind of just ignoring the fact that more powerful motors exist. If you want a more powerful hub motor QS will sell you any number of insanely powerful hubs and if you want a mid drive kit that will do the same you can buy an LR kit in whatever your flavor of insanity is. I've seen people put LR big block XLs or QS 205 50Hs on unmodified bicycle frames, those people were insane but they did it without much difficulty.

I'm not even against dual motors, I actually built a dual motor bike, a 2WD fatbike with identical motors but the reason was not for more power it was for the 2WD and I was willing to take the multiple motor penatly to get that capability. My point is the reasons for a dual motors hub + mid are very few with lots of reasons against. Honestly the reasoning for many builds like this seems to be slapping cheap ebike kits together is easier than designing the vehicle from the start to do what it needs to. Which I guess is fair but I would rather have 1 motor that I've designed to be efficient, powerful enough, and durable for the application.

 

[ebike4healthandfitness]

I'm also in the big single motor camp.
Less complexity is good!

Except for the fact that with 135mm rear spacing there aren't many (if any) options that are cheap and powerful.

For example, the Crystalyte H+55100 (actually 137mm, not 135mm) used in the Stealth Bomber is only rated at 2500w continuous (as installed in the Stealth Bomber) and the price tag for it is $873 new on eBay.

2500w continuous is 1500w continuous below the European spec for pedal mopeds.

 

[hillslayer@]

I'm not sure you actually paid attention to the video. The first half is Justin explaining how it's normallly not a good idea. Then he gives some reasons why you might want to do it, most of those are not the ones talked about in this thread. We aren't talking about weird vehicle designs or about driving multiple wheels.

Redundancy is debatable as making something that is redundant while also making the whole system less reliable and more complex defeats the purpose. In general electric motors are extremely reliable and if you want something that is reliable you should address the reasons why ebike motors fail not just slap another motor on while not addressing the issues with it either.

In terms of power I honestly think Justin is somewhat wrong, he's kind of just ignoring the fact that more powerful motors exist. If you want a more powerful hub motor QS will sell you any number of insanely powerful hubs and if you want a mid drive kit that will do the same you can buy an LR kit in whatever your flavor of insanity is. I've seen people put LR

I'm not sure you actually paid attention to the video. The first half is Justin explaining how it's normallly not a good idea. Then he gives some reasons why you might want to do it, most of those are not the ones talked about in this thread. We aren't talking about weird vehicle designs or about driving multiple wheels.

Redundancy is debatable as making something that is redundant while also making the whole system less reliable and more complex defeats the purpose. In general electric motors are extremely reliable and if you want something that is reliable you should address the reasons why ebike motors fail not just slap another motor on while not addressing the issues with it either.

In terms of power I honestly think Justin is somewhat wrong, he's kind of just ignoring the fact that more powerful motors exist. If you want a more powerful hub motor QS will sell you any number of insanely powerful hubs and if you want a mid drive kit that will do the same you can buy an LR kit in whatever your flavor of insanity is. I've seen people put LR big block XLs or QS 205 50Hs on unmodified bicycle frames, those people were insane but they did it without much difficulty.

I'm not even against dual motors, I actually built a dual motor bike, a 2WD fatbike with identical motors but the reason was not for more power it was for the 2WD and I was willing to take the multiple motor penatly to get that capability. My point is the reasons for a dual motors hub + mid are very few with lots of reasons against. Honestly the reasoning for many builds like this seems to be slapping cheap ebike kits together is easier than designing the vehicle from the start to do what it needs to. Which I guess is fair but I would rather have 1 motor that I've designed to be efficient, powerful enough, and durable for the application.

I'm not sure you actually paid attention to the video. The first half is Justin explaining how it's normallly not a good idea. Then he gives some reasons why you might want to do it, most of those are not the ones talked about in this thread. We aren't talking about weird vehicle designs or about driving multiple wheels.

Redundancy is debatable as making something that is redundant while also making the whole system less reliable and more complex defeats the purpose. In general electric motors are extremely reliable and if you want something that is reliable you should address the reasons why ebike motors fail not just slap another motor on while not addressing the issues with it either.

In terms of power I honestly think Justin is somewhat wrong, he's kind of just ignoring the fact that more powerful motors exist. If you want a more powerful hub motor QS will sell you any number of insanely powerful hubs and if you want a mid drive kit that will do the same you can buy an LR kit in whatever your flavor of insanity is. I've seen people put LR big block XLs or QS 205 50Hs on unmodified bicycle frames, those people were insane but they did it without much difficulty.

I'm not even against dual motors, I actually built a dual motor bike, a 2WD fatbike with identical motors but the reason was not for more power it was for the 2WD and I was willing to take the multiple motor penatly to get that capability. My point is the reasons for a dual motors hub + mid are very few with lots of reasons against. Honestly the reasoning for many builds like this seems to be slapping cheap ebike kits together is easier than designing the vehicle from the start to do what it needs to. Which I guess is fair but I would rather have 1 motor that I've designed to be efficient, powerful enough, and durable for the application.

big block XLs or QS 205 50Hs on unmodified bicycle frames, those people were insane but they did it without much difficulty.

I'm not even against dual motors, I actually built a dual motor bike, a 2WD fatbike with identical motors but the reason was not for more power it was for the 2WD and I was willing to take the multiple motor penatly to get that capability. My point is the reasons for a dual motors hub + mid are very few with lots of reasons against. Honestly the reasoning for many builds like this seems to be slapping cheap ebike kits together is easier than designing the vehicle from the start to do what it needs to. Which I guess is fair but I would rather have 1 motor that I've designed to be efficient, powerful enough, and durable for the application.

 

[hillslayer@]

You guys are so stuck on your one motor thing, I have already explained the advantages of this setup less wear and tear on both motors and you completely overlook how Justin explains how dual motors are more efficient due to the heat loss being spread between the motors.

 

[scianiac]

You guys are so stuck on your one motor thing, I have already explained the advantages of this setup less wear and tear on both motors and you completely overlook how Justin explains how dual motors are more efficient due to the heat loss being spread between the motors.

Less wear on both motors? Depending on the setup you have far more moving parts and we've already pointed out how in these hub + mid you are putting more wear and tear on parts that would otherwise have none. I didn't take away the same things from Justin's video, for instance he starts it with this. My takeaway is dual motor setups can have their applications, I mean I just pointed out I'm not against dual motors, I built a bike with dual motors, but you have to consider what those are.

Dual motors dissipating heat more efficiently I don't think works in most fair comparisons. That is for the same system weight the single larger motor which will have more copper than both of the smaller motors combined will be more efficient because it will generate less heat from resistive losses. Also you only get more heat dissipation when you're using both motors. There are some very specific cases where you could get a hub + mid to be more efficient but I don't see them applying for most people.

Honestly you can build your bikes however you want, using a undersized hub motor and mid drive combined to is a perfectly reasonable way to achieve a power goal but it's not how I would optimize it. You can't really make any fair comparisons unless you are adjusting for weight or cost or something like that. Just saying well if I add more motor it's better than less motor is true but you haven't compared it to an equivalent system. How much does your hub + mid weight and how much power does it output vs the same weight in a larger hub or larger mid controlled for how hard the motors are being driven.

 

[hillslayer@]

I can climb a hill way faster with both motors and they only get warm, either by themselves would be slower and motor would be way hotter it's that simple.

 

[ebike4healthandfitness]

You guys are so stuck on your one motor thing, I have already explained the advantages of this setup less wear and tear on both motors and you completely overlook how Justin explains how dual motors are more efficient due to the heat loss being spread between the motors.

Two hub motors is very likely going to be cheaper than one big rear motor anyway.

With that noted, what I want is a beefy rigid fork that lets me mount a rear hub motor and therefore use as a front hub motor.

 

[yantra yatra]

This idea would be good for a front hub I think as Chalo may have mentioned.

Actually I’m looking at doing it as I have a BBS02 on a bike that is a bit underpowered for me (putting a HD controller on it), and putting a front geared hub motor BPM 500w on the front, with a controller that can operate at a bit higher current at 30-40amps.

A matter of having the parts available that suit the possibility, and it solving the issue of drivetrain wear for me and hill climbing without slowing right down in granny gear. I can ride at higher speeds under most conditions, eg up slight hills, can sit at the top speed using the hub without putting heaps of stress on the smallest gear with the mid, and more than double the power of the setup for a lot cheaper than buying new motors and batteries. I can also climb hills without having to keep it at a high speed eating lots of power, as would be required with direct drive to stop it bogging down, like the leafbike, which would otherwise be my preference.

I have two TO7 DM01s and they are a disappointment. The Bafang M635 is apparently no longer available on Ali. So the advantage of a torque sensing high power mid drive is limited to noisier and more expensive CYCs, and still you have drive train wear issues.

The Freegen Grin motor would be the next choice for me when released, besides the Leaf. But I also don’t have super high rated batteries to draw lots of amps for the Leaf. So running two batteries with two motors is quite good. It’s not so easy to get high amp consumer packs.

Also seems like a bit of an investment and some research required for either (leaf or freegen) to get a good setup.

 

[hillslayer@]

This is why my setup works for me, already had 48 volt batteries CSC 1500 watt hub was $ 165 and now have a bike that climbs way better than most and can hit 35 mph and as a bonus puts less wear on my drive train.

 

[yantra yatra]

Yea it makes sense. Front might be safer. Geared hub also handy.

Do you you know how much power you can put through the CSC? I’m interested in getting one maybe. And 35mph is your top speed? A lot cheaper than the Leafbike or Freegen. Interested to hear how this setup works out over the longer term.

 

[hillslayer@]

I am running the stock controller 35 amp, you could probably run 72 volts and do 50 mph . On a fresh charge and full throttle on the mid - drive have seen 40 mph but not very good for battery range, hub will do 35 mph by itself.

 

[ebike4healthandfitness]

I am running the stock controller 35 amp, you could probably run 72 volts and do 50 mph . On a fresh charge and full throttle on the mid - drive have seen 40 mph but not very good for battery range, hub will do 35 mph by itself.

50 mph is going to be tough unless you have enough aerodynamic advantage:

Bicycle Speed (Velocity) And Power Calculator

Bicycle Speed (Velocity) And Power Calculator, comparing different kinds of bicycles

www.kreuzotter.de

A mtn bike or LWB recumbent (with Under seat steering) will require more power than a road bike:





Even LWB recumbent with above seat steering would (very likely) be slower:

 

[neptronix]

Yeah you would need a semi recumbent at least.

Here's 86.5v/~35A on a semi recumbent.



I can hit 33-34mph on 900W with mine... on a motor with currently poorer efficiency than what you see above.

..it also helps that 20" wheels produce a large efficiency/continuous power output versus a much larger wheel. Can extract incredible power from a small motor thanks to the higher RPMs. This bike with a small DD would be a land rocket..

 

[ebike4healthandfitness]

I can hit 33-34mph on 900W with mine... on a motor with currently poorer efficiency than what you see above.

..it also helps that 20" wheels produce a large efficiency/continuous power output versus a much larger wheel. Can extract incredible power from a small motor thanks to the higher RPMs. This bike with a small DD would be a land rocket..

What altitude are you at?

I ask because the elevation a person rides at can have a very significant effect on aerodynamic drag.