Geared vs Direct Drive - Regenerative Braking Work?

[Trailblazer]

Hi Guys,

First build was a Specialized Expedition with a Currie Power Kit from Amazon. Great bike! I use it for commuting almost every day. It is fine on flat and small hills, but doesn't have much ooomph at all.

Second bike I want to climb some hills here in Moab, UT (world famous slickrock bike trail). The hills are around 10% grade, some maybe even at 20% or so. These are shortish climbs (10's to a few hundred feet). I don't need the motor to go up these grades for hours.

I have a fully-suspended Specialized M5 http://www.score-outdoors.com/shop/specialized-s-works-m5-full-suspension-mountain-bike-nice/ from the glory daze and was thinking of putting one of two hub motors on it. I already have a 48V20AH Headway battery from eBay (for better or worse).

MAC motor from EM3V. http://em3ev.com/store/index.php?route=product/product&product_id=138
I'm working with Paul now to spec out what I need to do the hill climbing - 10T? Will an 8T do it?

Crystalyte HS3540 from Grin. http://em3ev.com/store/index.php?route=product/product&product_id=138
My understanding is that the direct drive motors don't have the torque of a geared hub motor. They also don't have the clutch and provide resistance to pedaling (which I do a bit to stay in shape).
These DD motors also have regenerative capabilities.

Does Regenerative Braking work specifically on the Crystalite hub?

I've heard that it just doesn't do that much. If it works well, it could come in handy for longer rides that are mostly up on the way out and then mostly down on the way back.

I also need a rack for the battery on the back. Does anyone know of a good seat post rack that can hold 25lbs?

Thanks for any help, guys!

 

[Drunkskunk]

Regen only works on a direct drive hub. Geared hubs are freewheeling when the power is off and can't generate anything. But Regen is a luxury. Its realy only good for getting 5-10% of your power back. It does far better for helping with breaking, but that will add heat to a motor and offroad, heat is the enemy.

There is some drag from a Direct Drive motor when the power is off. Its about like riding a bike with knobbies instead of slicks, or running a tire about half flat. Somepeople mind, some don't.

Cheap Bell seatpost racks have a main arm and clamp made of steel. the deck is plastic trash, but the weight bearing part is stronger than anything else I've found.
Unfortunatly, if you make the rack strong enough, you may break the seatpost. IIRC Dogman had troubles with exactly that. Since the M-5 is built with very light weight parts, you are likely going to have a problem with that. You are likely going to have to build your own rack, that bolts onto the frame with some form of braceing.

But be aware that all that weight on the back will upset the balance a lot. 25lbs of battery on a 23 lbs bike is going to affect your handling no matter what you do, but adding it high and over the rear along with a 10-12lbs motor will ruin the feel of the bike. It would be better to find a way to carry the battery on the frame, even on top of the frame if you have to. Or mounted to the handlebars if nothing else, that will preserve the handling better than a rear rack on a Full suspension off road bike.

 

[bowlofsalad]

The whole concept around direct drive hubs creating drag is, I think, called cogging. But I don't know if I really see this as an issue myself. In order to eliminate this issue, all you need to turn the throttle to 1%. A lot of these matters have been discussed to death and asked many times. I recommend doing some searching around. I am not sure if I fully understand the torque concept myself. On a simulator such as ebikes.ca/simulator the numbers are just numbers, they sort of tell the story but it's still hard to know. I like to think of various motors in their windings or geared equivalent like gear ration. The problem is thinking of this in an abstract concept when comparing each kind of motor can be a little difficult, even more complicated is fully understanding how these various motors will climb hills.

There are a tremendous numbers of pros and cons when considering each style of propulsion. It'll be tough for anyone to really say or know how or if a motor will handle your particular situation and moment. Things like your height, weather (wind, temperature), your collective weight, tires, momentum and the path itself can all play massive roles in how everything is going to groove together. There haven't been too many hills I wasn't able to pedal up without an ebike, if you are willing to put that energy into climbing a hill, I think that no matter what setup you have, you will probably be pretty a-ok. The worst case scenario if you are really worried about whatever setup you get, you might setup a temperature monitor.

Extreme hills often call for very slow geared hub motors, two motors (one in each wheel) or mid drives. The beautiful curse is that the choice is yours.

 

[Trailblazer]

Regen only works on a direct drive hub. Geared hubs are freewheeling when the power is off and can't generate anything. But Regen is a luxury. Its realy only good for getting 5-10% of your power back. It does far better for helping with breaking, but that will add heat to a motor and offroad, heat is the enemy.

OK, yeah that's not enough power back to really even enter into the equation. Thanks very much for that.

But be aware that all that weight on the back will upset the balance a lot. 25lbs of battery on a 23 lbs bike is going to affect your handling no matter what you do, but adding it high and over the rear along with a 10-12lbs motor will ruin the feel of the bike. It would be better to find a way to carry the battery on the frame, even on top of the frame if you have to. Or mounted to the handlebars if nothing else, that will preserve the handling better than a rear rack on a Full suspension off road bike.

I hadn't thought a ton about that, but I know that you're right on this. I would like to find a way to suspend it within the frame. I see a lot of photos of people doing this, so I figured that was the way to go. I can really see why when you put it that way.

Extreme hills often call for very slow geared hub motors, two motors (one in each wheel) or mid drives. The beautiful curse is that the choice is yours.

Beautiful curse...I like that. Yeah, I guess the absolute best would be a mid drive, but I didn't want to be so intrusive. I want to be able to throw the other tire on there, remove the battery/controller and ride it like a normal MTB. Maybe I'm trying to be too flexible. Huh. All good stuff to think about.


Thanks for the input!

 

[DAND214]

If you go with the Mac, I would go with the 10t. You will have plenty of speed with 48v. Also think of what controller you will be using. You will need some amps to get any motor to climb a good size hill.

As for the Xylte HS, why not the HT? Also on the regen, my mot be much in recharge but will help save your rim brakes.
that si the next thing to think about. does the bike have disc or rim? The one you listed was rim but has provisions for disc.

I am also assuming it's aluminum. You better get 2 Torque arms, with any motor choice you make.

As also stated above, you don't want to mount the battery in the back or off the saet post. Split the pack and hang it over the top rail if needed.

Dan

 

[neptronix]

10%-20% grades? you'll melt 95% of motors on the market doing that.

I live in Utah and the hills near bountiful on the way up to the shoreline kill my poor little MAC motor.
You will melt a MAC motor doing that in record time. Forget it.

You either need a mid drive, or the smallest hub motor you need is a Cromotor or HS4060 in a 24" wheel.

 

[Trailblazer]

10%-20% grades? you'll melt 95% of motors on the market doing that.

I live in Utah and the hills near bountiful on the way up to the shoreline kill my poor little MAC motor.
You will melt a MAC motor doing that in record time. Forget it.

You either need a mid drive, or the smallest hub motor you need is a Cromotor or HS4060 in a 24" wheel.

The hills I'm talking about are short. The entire hill is ~ 1.5mi long and overall grade is 5% with 2 short 10% grades. So the MAC can't do it, eh?

What if I'm pedaling a lot? Will that help it enough? I found the Cromotor at one place for $650 as a standalone - methtek. Can't find the HS4060 for sale anywhere.

As far as the middrive - the GNG looks to be in my price range but the kit appears too cheaply made.

Dang.

 

[Trailblazer]

As for the Xylte HS, why not the HT? Also on the regen, my mot be much in recharge but will help save your rim brakes.
that si the next thing to think about. does the bike have disc or rim? The one you listed was rim but has provisions for disc.

I am also assuming it's aluminum. You better get 2 Torque arms, with any motor choice you make.

As also stated above, you don't want to mount the battery in the back or off the saet post. Split the pack and hang it over the top rail if needed.

Dan

Thanks, Dan. How is the HT different? Where can I find one? Rim brakes is what I have. Yeah, good idea on splitting the pack and hanging it over the top rail. OK, wow. Two torque arms from cabikes would be expensive. Any other supplier recommended?

 

[neptronix]

5% it will do.

10% grades, it might stall. i mean, if you are having to walk up something like that, it's likely that the motor won't go up it even if you feed it good power. 20%, no way. Not gonna happen..... even a cromotor will start complaining about the job it's given to do. 150 horsepower cars have a hard time pulling that off...

Yeah, the GNG kits aren't put together well at all. Keep an eye on the bafang drive. It's not very powerful, but if you need just a little help, then it may work. 350w actually makes a lot of torque when it is geared down to your highest torque / slowest speed gear. If you are willing to fork over, there are stronger mid drive kits out there, but.... $....

As for the 4060, act fast because maxwell65 is about to close this group buy.
http://endless-sphere.com/forums/viewtopic.php?f=31&t=48717

Don't bother with the HT unless you put it in a 20" wheel or something. It will burn up on those 10% sections unless you do oil / air cooling. Air cooling is prolly gonna be a no-no considering you're doing offroad though.

10%-20% grades? you'll melt 95% of motors on the market doing that.

I live in Utah and the hills near bountiful on the way up to the shoreline kill my poor little MAC motor.
You will melt a MAC motor doing that in record time. Forget it.

You either need a mid drive, or the smallest hub motor you need is a Cromotor or HS4060 in a 24" wheel.

The hills I'm talking about are short. The entire hill is ~ 1.5mi long and overall grade is 5% with 2 short 10% grades. So the MAC can't do it, eh?

What if I'm pedaling a lot? Will that help it enough? I found the Cromotor at one place for $650 as a standalone - methtek. Can't find the HS4060 for sale anywhere.

As far as the middrive - the GNG looks to be in my price range but the kit appears too cheaply made.

Dang.

 

[-dg]

5% it will do.

10% grades, it might stall. i mean, if you are having to walk up something like that, it's likely that the motor won't go up it even if you feed it good power. 20%, no way.

I dunno, maybe the gravity is better in Utah, but here in CA, a 10T MAC in a 700c wheel with a 35A controller will take my 270 lbs up a half mile of 7 to 9% grade at about 17 mph with moderate pedaling. I think you may be a little pessimistic.

 

[Trailblazer]

I dunno, maybe the gravity is better in Utah, but here in CA, a 10T MAC in a 700c wheel with a 35A controller will take my 270 lbs up a half mile of 7 to 9% grade at about 17 mph with moderate pedaling. I think you may be a little pessimistic.

Huh. Well, that sounds good/do-able. Those other options are so expensive that if it'll do what you describe, I'd be happy. I wonder with the 12T will do? I've emailed Paul @EM3EV with my requirements. I'll see what he says.

So, is Amperage = Torque? I'm still pretty new at this. What voltage are you at on that or does it matter? (Voltage = Speed, right?)

Thanks for the input, -dg!

 

[neptronix]

Well, i'm 250lb, though i do run an 8T motor in a 26" wheel. Definitely have problems with stalling or getting close to it on ~10% grades.
I've demagnetized my motor pulling up extended hills. It's got so hot that it really lost it's power.

This is the hill that i significantly demagnetized my motor on. I was pushing 1500W and pedaling with all my might doing 15-19mph on a battery/controller combination that usually pushes 25mph on the flats ( 36v/42a )

p.s. you can generate routes like the above via toporoute;
http://www.toporoute.com/cgi-bin/bicycle.cgi

Just saying that you are playing with thin margins. You said 10-20% at the start of this thread which made me think that you need something larger. If you walk up hills above 10%, then go ahead and get one of these.

Geared motors have wonderful performance per lb but shed heat very slowly and very poorly. If you're going to go ahead and buy a MAC motor anyway, get the temp sensor setup from cell_man. It will give you a far better idea of the internal temp of the motor than the outside case will.

 

[-dg]

Well, i'm 250lb, though i do run an 8T motor in a 26" wheel. Definitely have problems with stalling or getting close to it on ~10% grades.
I've demagnetized my motor pulling up extended hills. It's got so hot that it really lost it's power.
,,,
p.s. you can generate routes like the above via toporoute;
http://www.toporoute.com/cgi-bin/bicycle.cgi

Just saying that you are playing with thin margins.

Checking the simulator shows that the 10T does a lot better than the 8T on 10% grades. I don't think the 10T would want to do miles of hill like that, but as I recall the OP said the steepest bits were short. It also depends on what the OP weighs and how hard they pedal. A strong light rider probably could take a short 20% grade, at least the simulator thinks so.

I like that tool, thanks for the link. Sadly, at least around here, the elevation data is a such mess that it is not useful. I tried it on several hills that climb and It shows random points that are over 100 below ground level so the plot looks like there are steepsided valleys in the middle of the hill. I don't know how accurate the rest of the points are, but I do know there are no decents on any of the hills I looked at. I hope they can sort that out or get access to better data because it looks pretty sweet otherwise.

 

[dogman dan]

The crux of the problem, is how long you will climb that 10% + grade. I've done 10 miles of 5-10% with ordinary 2807 9 continent motors. I had to use half throttle and pedal hard, but I made it up it cool enough.

But for really steep stuff, a big slow winding dd motor shines best. I'm not sure the HT is slow enough, but it will do 10% for a mile I bet. It won't be cool at the end, but it should make it up it.

Above 10%, that's where you really need either slow windings, 20 inch wheels, or both. I use a 2812 9 continent and 40 amps of 72v to climb 15 degrees. degrees not percent. It chokes to a stop at 20 degrees. I do it too long at least once a year, and melt another motor, usually just smoking the halls. So it still fails if the ride is too long. 26" wheels btw. I never smoke a motor on 20 amps though. and definitely still climb 15%.

Or two hubmotors. You are on the right track with double motor I think, provided your battery can stand it. Others have proven it works. I'd say an HT in the rear, and a 12t mac in front. Run about 30 amps rear, 20 front. When the HT bogs down, hit the switch and engage the front motor. 90% of the time, let it just freewheel.

 

[Trailblazer]

Well, i'm 250lb, though i do run an 8T motor in a 26" wheel. Definitely have problems with stalling or getting close to it on ~10% grades.
I've demagnetized my motor pulling up extended hills. It's got so hot that it really lost it's power.

Just saying that you are playing with thin margins. You said 10-20% at the start of this thread which made me think that you need something larger. If you walk up hills above 10%, then go ahead and get one of these.

Geared motors have wonderful performance per lb but shed heat very slowly and very poorly. If you're going to go ahead and buy a MAC motor anyway, get the temp sensor setup from cell_man. It will give you a far better idea of the internal temp of the motor than the outside case will.

All good to know, and after all this 'schoolin', I am willing to walk up the steeper hills in favor of something light and affordable. I was planning on getting the new version of the MAC with the temp sensor from cell_man. So, that seems like I'm on the right track. I really had no idea that it had those limitations, so thank you very much for your input.

Man there's a lot to learn about this stuff.

 

[Trailblazer]

Checking the simulator shows that the 10T does a lot better than the 8T on 10% grades. I don't think the 10T would want to do miles of hill like that, but as I recall the OP said the steepest bits were short. It also depends on what the OP weighs and how hard they pedal. A strong light rider probably could take a short 20% grade, at least the simulator thinks so.

Wait, what simulator are you using, the one at ebikes.ca? I can't find any 10T/8T settings. Am I missing something? I'm about 180lbs and can be a good pedaler if need be...but sure like the 'magic button'.

 

[-dg]

Wait, what simulator are you using, the one at ebikes.ca? I can't find any 10T/8T settings. Am I missing something? I'm about 180lbs and can be a good pedaler if need be...but sure like the 'magic button'.

The settings for BMC V2 torque and BMC V2 speed are roughly similar to the 10T and 8T MAC respectively. I assume a reasonably normal adult can pedal at 100 watts indefinitely and comfortably and at 200 watts for a few minutes. Most people can do better. If you slide the vertical line on the simulator to the right until the motor power is 200 watts less than the load you get an idea of how it will do with that much pedaling.

The key thing is that when the motor is turning slowly every bit of pedaling effort pays double or even triple. You go faster, the motor makes more power, the motor makes less heat. So pedal hard on the steep bits and keep your speed up. I'd say as rule of thumb with a geared motor if your are under 10 mph for more than a couple minutes you are asking for it.

 

[mark5]

Trailblazer, for whatever it's worth below is Hightekbikes' Terry Reilly and a Mac 10T climbing a hill.

[youtube]RIHJPOL3_HQ[/youtube]

 

[neptronix]

Looks like it was going 3-5mph... probably far below 50% efficiency.
So you can technically do it, but the heat is gradually building and building.

 

[Trailblazer]

Trailblazer, for whatever it's worth below is Hightekbikes' Terry Reilly and a Mac 10T climbing a hill.

Exactly...that's what sold me on the MAC. 'Course we don't know if he melted the motor on that hill.

 

[mark5]

ebikes.ca's simulator predicts overheat after 4 minutes for a 20% grade.

For the HS3540 motor you mentioned there's ebikessf Ilia Brouk's video. See around 7:02 when he's going up a hill.

 

[waynebergman]

Hi Trailblazer

I have ridden the slickrock trail a few years back on my 250 dual sport. Just a great trail and area to ride. Lucky you to be there.

I have an HS3540 that was run on 48v 35 amps and also the mac 10t run on the same 48v 35amp. The good thing about the DD hub is it can take a bit more of a beating smashing over bumps and stuff than the geared hubs but for the slick rock trail the HS3540 would be a really limping at 48v. At 48v with the HS3540 you have no torque at slow speeds and it will just feel like you are beating a very tired horse.It does not even sound happy dishing out the power from a dead stop on a hill, it just kind of groans till it gets up to speed and on the slick rock trail you will be doing a lot of groaning at 48v. The mac 10t on the hills is much better but unless you have it set up as a mid drive you will have to baby it a bit and keep an eye on the motor temps but it will still be super fun.

My advise would be if you are going to go with a mac 10 keep the bike as light as possible and still have around 1500 watts on tap for max power and know when to let it cool down if you are pushing it.

 

[Trailblazer]

ebikes.ca's simulator predicts overheat after 4 minutes for a 20% grade.

For the HS3540 motor you mentioned there's ebikessf Ilia Brouk's video. See around 7:02 when he's going up a hill.

I had seen that video but had not watched it all the way through. Wow, that 3540 isn't going to work at all. Thanks for that!

 

[Trailblazer]

Hi Trailblazer

I have ridden the slickrock trail a few years back on my 250 dual sport. Just a great trail and area to ride. Lucky you to be there.

I have an HS3540 that was run on 48v 35 amps and also the mac 10t run on the same 48v 35amp. The good thing about the DD hub is it can take a bit more of a beating smashing over bumps and stuff than the geared hubs but for the slick rock trail the HS3540 would be a really limping at 48v. At 48v with the HS3540 you have no torque at slow speeds and it will just feel like you are beating a very tired horse.It does not even sound happy dishing out the power from a dead stop on a hill, it just kind of groans till it gets up to speed and on the slick rock trail you will be doing a lot of groaning at 48v. The mac 10t on the hills is much better but unless you have it set up as a mid drive you will have to baby it a bit and keep an eye on the motor temps but it will still be super fun.

My advise would be if you are going to go with a mac 10 keep the bike as light as possible and still have around 1500 watts on tap for max power and know when to let it cool down if you are pushing it.

Wow, great advise from someone who knows the area I'm talking about! I had all but decided on the MAC 10T, now I'm in for one...off to cell_man's site. Thanks!

 

[dogman dan]

Just pay attention to the heat sensors, and you will know when you are pushing it an when you are not. 5 mph up 10% grades are too slow. That 10 mile ascent I spoke of, I maintained 15 mph the whole way. Only the last mile was 10% the rest was 8% with some 5 between the switchbacks. Paved road.

One time I melted the halls in a motor, I was easily able to do the grade faster, but it was such a ride though boulders that I couldn't really hang onto the bike much faster than 5 mph. I kept coming off, or just having to slow down through it, then trying to get back up to 10 mph on a steep grade of perhaps 15-20%.

I knew I needed to stop, but sometimes the little brain won't stop. It's always been a problem for me. Sure enough, just as I was thinking, " I really must stop soon", the ol smoke poured out the motor.

Whatever you've chose, if you really ride, you'll do the same thing. Ride that one mile too far. Just budget for a few melt downs. You really should be thinking in terms of a stock of motors, not which ONE motor. I have two 2812's and a 2810. So far, all have been repairable after a melt. I just keep at least one always running.