Geared motor on tough off-road terrain - wrong choice?

Hi,
I am interested in adding a geared motor to my mountain bike.
I ride on single tracks with lots of rocks, gravel, very mild jumps (30cm at most), and on insane inclines - +14% and -30% or more...
It seems obvious a geared motor will serve way better for the torque required - but how will it's teeth and clutch work under all those vibrations and shocks?
Imagine going uphill so the motor is at it's full torque, with lots of rocks and gravel coming under. I can't avoid using it while approaching obstacles, because all the ride is obstacles...

I am interested in Justin's ezee geared motor - the new version which allows a modern cassette to be fit in.
It seems like a solid device, capable of 1000W max.
On my bike I have a 10 speed cassette and I understand there should be no problem with fitting it as it's standard from 8 speed to 11 speed - but,
I do remember when I had another MTB with 8 speed cassette and thought of upgrading to a 9 one, I was told it wouldn't fit physically. Is it true?

If all the above are feasible, safe and reliable on long term - let me ask further:
I consider opening the motor and locking the freewheel clutch so I would have regen - Very useful when your track is mostly with two digit number grade percent, up or down...
It will ease up the brake heating and increase the range dramatically.
I only found just one post here of a guy that had to lock his clutch since the sprang mechanism got broken (and it wasn't an ezee motor), and he was going on roads only - but has anyone else have experience with an geared motor also as a regen capable? And how is the cogging torque perception? (I expect the cogging torque to be negligible as I will be barely going on flat ways - where it is mostly felt)
Of course I will have to take a non-ezee controller, and I think to implement it with Justin's new ASI FOC controller - It can be programmed to have the delicate ramp-rate for the teeth, so it won't "hammer" the gears like an infineon would have done. It seems also much better for the gears with it's sinusoidal waveform.

What is your opinion?

thunderstorm80 said:

Hi,
I am interested in adding a geared motor to my mountain bike.
I ride on single tracks with lots of rocks, gravel, very mild jumps (30cm at most), and on insane inclines - +14% and -30% or more...

Click to expand...

I think a middrive, especially the BBSHD or BBS02 will fit your riding style way better. The middrive works through any gears on the back and you will be able to go up +30% easily. Was a middrive something you considered?

If you choose to lock the clutch in the geared hubmotor the resistance when pedaling will be significant, most people would hate it.

Regen never increases range dramatically on ebikes, more like slightly.

For really steep and rough stuff the geared motor will not last long, and they overheat on steep climbs if much power is applied.

The extra unsprung motor wheel weight will make handling of the bike be poorer.

A powerful mid drive is preferred for steep conditions.

Alan B said:

If you choose to lock the clutch in the geared hubmotor the resistance when pedaling will be significant, most people would hate it.

Regen never increases range dramatically on ebikes, more like slightly.

For really steep and rough stuff the geared motor will not last long, and they overheat on steep climbs if much power is applied.

The extra unsprung motor wheel weight will make handling of the bike be poorer.

A powerful mid drive is preferred for steep conditions.

Click to expand...

On my city-commute E-Bike, with a 9C+ 2706 and powered by A123 cells - the range is extended by around 20%, but that's because I usually prefer to go downhill fast, wasting most of the potential on wind resistance.
I'm sure if I was more economic - I would see figures of 30%. I live in a hilly city.
On MTB, because you have to go down slowly, especially with insane grades, I thought regen would be even more effective.
But I take all what you said - I was considering a mid-drive but it can't do regen. But, Mid-Drive would be lighter, and lighter means spare weight for extra battery...
So you recommend the BBSHD or BBS02? I will read about them.
Where would you recommend to buy those? (online shop)

You are also right about the unsprung weight on the rear wheel...
Even though you have convinced me not to choose it - I am still curious from engineering perspective just to ask: If someone does put a geared motor for the scenario I described - will all the jumps, shocks and vibrations (while the motor is putting torque) will shorten significantly the teeth's life? Or was it meant to accept that kind of abuse as well?

30% is phenomenal regen energy recovery, if it is an accurate average. I've not seen anyone document more than about 20% and generally it is around 5%. I've never seen more than about 10% on my setups, and that requires going downhill fairly slowly. Justin achieved 20% in the Canadian mountains going downhill most of the day. We're talking about the actual energy back into the battery over a discharge cycle, not a momentary peak.

There is an offroad frame someone makes and sells here on ES that debuted with a rear gearmotor. The motors failed fairly rapidly as I recall, clutches mostly, and then gear teeth generally go when the motor gets hot and the teeth soften and strip. I haven't followed what they are doing now. If you don't mind the maintenance and limitations on gradient it can work. They were in Southern California, their videos didn't look as steep as some places.

I'm not saying you can't do it, just reporting what experiences most have had.

Anytime you operate an electric motor at high torque and low speed it gets pretty hot. Gearing helps solve that problem. Gearmotors are 5 up to 11 to one, mid drives can be much higher ratios. The other thing that reduces heat in a hubmotor is to reduce the torque required by having two of them, 2WD.

I am putting a BMC gearmotor on the front wheel of my oldest ebike, a Bonanza mountain bike which has a DD motor on the rear wheel so it will be 2WD, but that is not complete. As a hard-tail mountain bike with a 9C DD on the rear it doesn't have enough torque for steep trails. With the 2WD it will have plenty of torque, but no suspension and it will be heavy, probably not ideal if you want to go fast. It will be more like a "tank", point it somewhere and it will get there. It is a project I started long ago, so the motor wheel was purchased before I got a newer Diamondback.

The Diamondback 27.5 hard tail with front suspension I set up with a BBSHD. This is my newest bike, I call it the RidgeRunner, it really likes climbing the steep stuff. The Diamondback is more like an offroad sports car with front suspension (but not rear), very light, with tremendous torque from the gear train. It doesn't have regen but will climb trees if you can stay on the bike. I upgraded the brakes to handle the downhills. This setup will require more chain and brake pad maintenance.

For a pavement commuter the DD hubmotors are lower maintenance, especially with variable regen so the brake pads last just about forever. If it is steep pavement then a gearmotor or larger DD hubmotor is the ticket.

It just depends on what you want to do. If you want to do it all with one bike then a mid drive is probably the best compromise.

I would use the BBS02 on a street rig for light weight and modest speed. For steep stuff or pushing harder to higher speeds I would stay with the tougher BBSHD as the BBS02 gets hot fairly easily when pushed.

I'm planning a BBS02 for a folding bike that I'm working on. Don't need much power, don't want much weight, but still need to climb some steep stuff occasionally.

I have threads on my builds in the signature line below if you want to see more, and ES is full of builds to look at.

IMO, major problem with geared hub motors for rough terrain is that the axle isn’t a through piece. I don’t think a 2 piece axle can ever be as strong as 1 piece axle.

We had somebody use a small geared hub motor on a trike and it sure didn’t like side loading much either.

A lot will depend how rough, how fast, how heavy, how powerful, etc?

BB drives are probably best bet for off road. Keep gear ratio low (numerically high) when using BB drives.

Interesting. I didn't know they had to have a 2 piece axle. Do they fail there often?

Maybe that's why the gears and clutches end up failing with drops?

Def middrive for what you're describing, as optimal. More power possible to the road, and thru a much larger gear ratio! Sure, you'll know (or learn) more about bike drivetrains and their upkeep and replacement, but there is no comparison for what you are looking for.

To not answer your question tho: I have no idea how long a geared hub will last, but 10% for a length of time is asking alot in tech terrain to begin with. Dogman Dan had a pretty knarly video of some rocky climbing with geared up "can your electric bike do this" I think it's called. I think that's the most extreme I've seen from one.

Alan B said:

Interesting. I didn't know they had to have a 2 piece axle. Do they fail there often?

Click to expand...

Of course... The axle on the ring ring side ends where the clutch is. Because of the speed difference between the motor and the wheel, it has to be more than one spinning axle.

In the meantime I was learning about the BBS motors.
It seems I will have to give up the triple crank on my MTB, and only use a single chain-ring if I pick that mid-drive motor.
Are there other mid-drives that retain my original crankset?
Maybe a direct-drive BB motor? Is there such thing?
I don't need much power, as it will be only for assistance.

I think one of them (bbsxx?) allows two chainrings. Some people just manually go from ring to ring though, prob due to deraileur/middrive integration. . . 48t x 11-36t will work excellent from a crawl to around 30mph for pedalling, and with even 250w you won't need the little extra ratio and inbetween gears made possible with 2x and 3x chainring sets.

If you want the best 'assist' mtn bike, be prepared to pay for a proprietary model like haibike or others. Among them is the most polished assisted bikes.

thunderstorm80 said:

In the meantime I was learning about the BBS motors.
It seems I will have to give up the triple crank on my MTB, and only use a single chain-ring if I pick that mid-drive motor.
Are there other mid-drives that retain my original crankset?
Maybe a direct-drive BB motor? Is there such thing?
I don't need much power, as it will be only for assistance.

Click to expand...

Why do you need more than one chainring? With a BBS02 or BBSHD and a single 42 tooth lekkie chainring,
you can climb 30% grades AND hit 30mph on the flats. You will have the power of three Lance Armstrongs*
backing you up IF you need it

(Lance = 510W)

tln said:

thunderstorm80 said:

In the meantime I was learning about the BBS motors.
It seems I will have to give up the triple crank on my MTB, and only use a single chain-ring if I pick that mid-drive motor.
Are there other mid-drives that retain my original crankset?
Maybe a direct-drive BB motor? Is there such thing?
I don't need much power, as it will be only for assistance.

Click to expand...

Why do you need more than one chainring? With a BBS02 or BBSHD and a single 42 tooth lekkie chainring,
you can climb 30% grades AND hit 30mph on the flats. You will have the power of three Lance Armstrongs*
backing you up IF you need it

(Lance = 510W)

Click to expand...

Lance was using drugs to achieve those 510W...
I need the other chainrings because I want the MTB to stay as is, and so I can use the motor when I want to. If I will have just one chain-ring (or two), because of the lack of ratios, I will be forced to use the motor all the time on hard grades which I could have done without it before.

Well maybe you can get puffs from the magic dragon to 'assist' you then :lol:

Seriously bro: "need" - you don't. You don't even "need" the ratio WITHOUT ASSIST.

Assuming you've considered and reject the high dollar offerings, it's time to 'get with the program', or make your own 'program', or forget about an ebike for 2016.

Lance was using drugs to achieve those 510W...
I need the other chainrings because I want the MTB to stay as is, and so I can use the motor when I want to. If I will have just one chain-ring (or two), because of the lack of ratios, I will be forced to use the motor all the time on hard grades which I could have done without it before.

Click to expand...

So, when do you want to use the motor? Only on grades tougher than you could do today?

You can get more gear range just in the rear. There are geared hubs that also take a cassette like SRAM dual drive. Or a Rohloff hub. Or maybe just a 42 tooth rear sprocket.

(No guarantee that the dual drive can take three juiced Lances )

If you want to keep all three chainrings there aren't too many (or any?) DIY mid drives.

I'm maintaining all three front chainrings, and six or seven rear ratios by putting two hubmotors on a mountain bike. A DD in the rear and a geared in the front. With double torque it will climb like a tractor. But it adds a lot of weight, and I had to take the front suspension fork off. So it will be more like a tank, able to climb anything but not really great in the handling department.

I guess it is time to look either at a Roholoff rear IGH to get a wide range with single front chainring or a high dollar commercial mid drive ebike. I'm not even sure they have the triple chainrings, generally they've found out already they're not needed and are omitted.

You could always add a friction drive if you don't want to change the bike much. Good for modest assist on dry non-steep stuff.

Or just go for a geared front hub, leave the rear drivetrain alone. But the front hubmotor messes with the front suspension and adds unsprung weight and won't hold up well in the rough if you ride it fast and hard. Jumping really bashes the clutches. I won't be doing that so I don't mind.

At some point you have to decide if you want a pedal bike or an ebike. You can't have everything in one machine without compromise.

Incidentally, "maintaining all the gears" is a common first time goal for a newbie's ebike conversion. Then after awhile they find out that you never ever use the front chainring. Happened to me, too. I still have the front chainrings on a couple bikes, but they never get used. So I had no problem taking them off to put on the BBSHD. They are still in a box if I ever want them back.

Alan B said:

If you want to keep all three chainrings there aren't too many (or any?) DIY mid drives.

I'm maintaining all three front chainrings, and six or seven rear ratios by putting two hubmotors on a mountain bike. A DD in the rear and a geared in the front. With double torque it will climb like a tractor. But it adds a lot of weight, and I had to take the front suspension fork off. So it will be more like a tank, able to climb anything but not really great in the handling department.

I guess it is time to look either at a Roholoff rear IGH to get a wide range with single front chainring or a high dollar commercial mid drive ebike. I'm not even sure they have the triple chainrings, generally they've found out already they're not needed and are omitted.

You could always add a friction drive if you don't want to change the bike much. Good for modest assist on dry non-steep stuff.

Or just go for a geared front hub, leave the rear drivetrain alone. But the front hubmotor messes with the front suspension and adds unsprung weight and won't hold up well in the rough if you ride it fast and hard. Jumping really bashes the clutches. I won't be doing that so I don't mind.

At some point you have to decide if you want a pedal bike or an ebike. You can't have everything in one machine without compromise.

Incidentally, "maintaining all the gears" is a common first time goal for a newbie's ebike conversion. Then after awhile they find out that you never ever use the front chainring. Happened to me, too. I still have the front chainrings on a couple bikes, but they never get used. So I had no problem taking them off to put on the BBSHD. They are still in a box if I ever want them back.

Click to expand...

The reason I want to also keep the MTB as is, is because it's for my dad's MTB. He is very conservative but getting old, so I want him to be able to use the motor or not using it at all if he choose not to. (so he can slowly adapt to what it feels to go with a motor)
I can see how hard it becomes for him to do the same old single-tracks we do, so a motor can definitely keep him going on trails (at parts), instead of staying home.
The Roholoff is a great idea! With their 14gear ratio, even with a single chain ring you get around the same gear range of a traditional triple crank.
Too bad it's so expensive, but I guess it's worth it.
Thanks for the idea!
If I have only a single sprocket and a chain-ring, will a belt drive provide a better longevity and less wear-off than a chain?

Look at serial drives. A small motor to the rear wheel on the left side. Look at Recumpence's builds. Or my mountain bike build.

drewjet said:

Look at serial drives. A small motor to the rear wheel on the left side. Look at Recumpence's builds. Or my mountain bike build.

Click to expand...

I couldn't find "serial drive" motor. You have to understand those kind of things bring too many unrelevant results on Google
A direct link with an example would be so much easier...
'
I looked at your mountain bike build, but I prefer to buy "shelf" products, and assemble them together. I am good with improvising, but don't like to do it unless it's necessary.
Home made improvision + shaky MTB rides = early failure (from my experience)

Belts require breaking the frame triangle for installation if it is in the way. They take more horizontal space, add a bit of loss and are much more sensitive to consistent and proper tension and alignment. Chains are amazingly forgiving and just easy. The Rohloff will likely require some type of chain tensioner.

Belts seem to be best when done by the manufacturer of the bike, they are difficult to add later due to frame, tension and alignment requirements. A lot of people talk about using belts, rarely does anyone actually do it. It makes a project more difficult.

A Left hand side drive is more motorcycle like, generally reserved for high power builds. The motor is always in circuit and pedaling it while the motor spins much faster than the wheel creates resistance most people dislike.

If the drops are really minor as you indicated and the rider is less aggressive the gearmotor may last a long time. The motor takes width so you may find it difficult to get more than 7 or 8 gears to fit, even that may require spreading the dropouts which is only recommended for steel frames. But it would allow the full front chainring set to remain, which allows a wide gearing range (at low cost) just not quite as many in-between ratios. If the gearmotor clutch fails you can always disable it at that point, or replace it as parts are generally available.

Adding a hubmotor to either axle makes flat tire repair much more difficult, wrenches are required, there is more axle hardware such as torque arms, lockwashers and lug nuts plus the wheel is quite heavy. Careful attention is required to absorbing the torque of the gearmotor without over stressing an alloy frame. Mid drives allow QR axles to still be used, and the wheels are stock standard to changing flats is the usual annoyance rather than a larger project.

The PhaseRunner is a great controller, I'm putting a pair of them on my 2WD now, just getting the BMC Gearmotor running at this point. They have a large number of parameters to set up, but the throttle response is quite nice. One concern with the PhaseRunner and Gearmotor is when you "get air" the torque throttle will accelerate the unloaded motor wheel very quickly and the landing will stress the clutches and torque arms. I expect that dropping the throttle on jumps can be learned but forgetting will hammer the motor.

If your father has a motor and you don't, it will create a disparity between capabilities, you may not catch him again.

One thing I’m always surprised about no matter what style motor I install on a bicycle is how few gears are actually needed.

On/off-road, 3-5 gears with a motor is more than I know what to do with. Folks talk themselves into more gearing but the fact remains, it’s a much different game when using even a low power motor.

I suggest people start with some sort of basic eBike experience and work from there. Trying to “nail it” ALL out of the gate without BIS (butt in saddle) experience is an expensive and fleeting game.

To add to the above, I'm using 8-speed, 11-17-28 with a 30 tooth ring on my BBS02; climbs anything I've encountered with a 22-24 mph top speed, shifts perfectly. Also, if your dad has been mountain biking for a long time, he's not going to enjoy the extra 10-15 pounds a rear motor adds, or the sensation of the front wheel spinning when it's off the ground on a front hub system.

Ykick said:

IMO, major problem with geared hub motors for rough terrain is that the axle isn’t a through piece. I don’t think a 2 piece axle can ever be as strong as 1 piece axle.

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what motor you are talking about?
the MAC, ezee and like many more geared motors have a 1-piece or through axle.

madin88 said:

Ykick said:

IMO, major problem with geared hub motors for rough terrain is that the axle isn’t a through piece. I don’t think a 2 piece axle can ever be as strong as 1 piece axle.

Click to expand...

what motor you are talking about?
the MAC, ezee and like many more geared motors have a 1-piece or through axle.

Click to expand...

Sorry, Q100/128 here and I can assure you they're 2-piece axle. I have no idea if other designs do or don't.

Thank you for adding more and better info to the discussion.

Have there been any problems with the two piece geared motor axles?