Trailriding short steep hills. Low top speed.

Tordnado

10 mW
Joined
Nov 10, 2016
Messages
30
Hi!

I have been reading and reading and I think I have found the best reasonable solution (probably not) but I need your input.

* I have a 26" fullsuspension MTB (145mm front and rear) that I would like to keep stealth.
* Not possbile to install bafang middrive
* I don´t want to widen the spacing in the rear where I want to install the motor by more then 1-2mm. So 135-137 mm it is.
* I use hydraulic disc brakes
* I have a 50V battery from EM3EV.COM that I want to use. (Normally use it on my commuter)
* I ride single trail, with some small jumps. There are no mountains but rather short but steep ups and downs. Normally no more then 1 minute going up. I ride these trails unassisted at the moment but my father got a Bosch mid drive kit and I am struggling to keep up with him :-(, not that far behind though so what I need is a boost up the hills in order to reduce the lactic acid in my legs so that I can keep up on the flat and downhill with my own power.
* Needs to be a cassette type of rear hub.
* So a xiongda would be great in first gear (second gear would be a nice to have but not needed) but it is to wide. Any other options that fits the bill?

Assistance to 15km/h (9-10mph), torque, light weight. I dont think it needs a VERY high torque like a lot people on this forum means high torque as in pulling 250 pound up a long hill unassisted, I just need some low speed assistance for a fairly short period of time.

I am thinking a small hub motor but except for the xiongda the ones I have found have unnecessary high top speed.

I hope my question is defined well enough for you to give some input.

Thanks!
 
Yep, you need a very slow hub, that will spin to your target top speed at 50v.

A few years ago it was pretty easy to find slow windings, but now they are very few. Yet some manufacturers are willing to make the winding that you need, most of the time without any extra other than having to wait longer for shipping.
 
Q128 "201" rated @ 48 Volts. That would be like a 170 rpm @ 36 Volts, a very slow turning motor.
I believe Dave(D8veh) has built a Billy Goat w/it. Ck his posts here, but there is more info on it @ pedelecs UK.
 
For serious off road riding, you need a serious motor. That's the MAC. em3ev.com/store/MAC Anything less and you'll probably be blowing out gears and clutches riding off road.

There is a cassette option for the MAC. A 10T would probably be low enough. There is a 12T option that goes even slower.
 
MadRhino said:
Yep, you need a very slow hub, that will spin to your target top speed at 50v.

A few years ago it was pretty easy to find slow windings, but now they are very few. Yet some manufacturers are willing to make the winding that you need, most of the time without any extra other than having to wait longer for shipping.

Sounds interesting, can you recommend a supplier that could do it?
 
Drunkskunk said:
For serious off road riding, you need a serious motor. That's the MAC. em3ev.com/store/MAC Anything less and you'll probably be blowing out gears and clutches riding off road.

There is a cassette option for the MAC. A 10T would probably be low enough. There is a 12T option that goes even slower.

A MAC is overkill both in performance and weight plus it is too fast to be effecient at the RPMs I intend to use it:

From EM3EV: At 48V expect the following, 12T - 34km/h (21mph)
 
Tordnado said:
A MAC is overkill both in performance and weight plus it is too fast to be effecient at the RPMs I intend to use it:

From EM3EV: At 48V expect the following, 12T - 34km/h (21mph)

So don't run it at 48V. Use a lower voltage. Half the voltage results in half the unloaded RPMs. A 12T MAC at 24V and the maximum allowable current is one of the only possible solutions to your problem as you've outlined it.

Yes, it's heavy and will impair the rear suspension. But no lightweight hub motor will be of any use to you.
 
nutspecial said:
Or even the standard wind smaller geared hubs on 24v. Ebikekit sells some smaller ones too I think.

Those might work fine from a strictly RPM standpoint, but they probably won't deliver the required torque to help on very steep grades, and their gears and clutches probably won't withstand off-roading.
 
Agree, though I get the feeling Op wants supplementation (~200w), but wants it geared for 10mph or so max. I'd think a small geared should hold up fine for that, and deliver some nice supplemental power for climbing when volted/geared properly? Personally I'd be more concerned with any handling deficiencies of the added weight to the bike (hub and 48v bat), and how geared hubs are supposedly susceptible to drops/jarring. Still doable if you didn't ride DH like a madperson to begin with though.

But there just isn't a diy system that will be as seamless and smooth as the better purpose made ebikes, afaict, for 'bike'-like performance offroad operation.
Op, how far would you have to spread the d/o's to fit what you want? Why don't you just do that?
 
Be aware some folks around here can “think” a lot of things but have no actual experience about what they’re suggesting.

For what you’re describing you really need a mid drive motor, IMO. Bafang won’t fit on that bike? I’d get another bike. Mid drive makes so much difference for off-roading I can’t recommend anything else.

Here’s my latest BBS02 re-build -
FullSizeRender.jpg
Literally floats over the craziest terrain.

I’ve never done a 2 wheel drive so I’m not going to comment there but I’ve ran 2qty Q128H 201 RPM motors into the ground commuting. I suspect you’ll be happy for a while but even with the supposed 800W rating it’s a light duty motor.

Knowing what I “know”, 50V Q128H 201 RPM in 26” wheel would probably top out around 16-18 MPH.
 
Yep.. the bike is the problem, fix that.

You could do a Mac, or similar rear motor. I ride dirt all the time with a similar 10t wind motor. 48v- 1000w,, once you are on that steep,, its not too fast, you don't get 28mph on the steep part. You do need to pedal hard sometimes, trying to keep the rpm up where it needs to be, above 10 mph, but it will do 15 mph up some pretty steep hills. In 26" wheel or larger, you need to charge the hills fast, or you quickly overload, and overheat the motor trying to climb steep hills too slow. So let dad catch up after the short hill.

Otherwise,, not too fast,, uhh,, that's what the throttle does bro,, lets you back off to the speed you want. pick a gear, pedal the cadence you like in that gear. Bring up the throttle to just the point where you don't puke from the hard pedaling, no more. That's how you ride. Once back on the flat, you can ride as slow as you want, 50w, 100w, 500w, whatever you choose. Throttle man,, no pas. But pick up the speed again on the steeper uphills.

But the deal breaker with geared hub motors is the jumping. hucks break the clutch inside, or shear the axle key. You can still do small pops, just land with the throttle off. But hucks,, no.

A low rpm rear direct drive motor is currently out of stock at E-bikekit. And nothing stealth about a dinner plate size motor anyway.
 
nutspecial said:
Agree, though I get the feeling Op wants supplementation (~200w), but wants it geared for 10mph or so max. I'd think a small geared should hold up fine for that, and deliver some nice supplemental power for climbing when volted/geared properly? Personally I'd be more concerned with any handling deficiencies of the added weight to the bike (hub and 48v bat), and how geared hubs are supposedly susceptible to drops/jarring. Still doable if you didn't ride DH like a madperson to begin with though.

But there just isn't a diy system that will be as seamless and smooth as the better purpose made ebikes, afaict, for 'bike'-like performance offroad operation.
Op, how far would you have to spread the d/o's to fit what you want? Why don't you just do that?


You got it right unlike some people who probably did not read my first post but where answering to their own needs.

So the problem is the durability of the clutch and gears it seems. The torque should be fine since the torque increases as the RPM goes down and it will help me go a little faster. Please note that I only have short uphills, max 1 minute ride up the hill and I ride up them with my own power currently. Running lower voltage is not going to help since I need to pour in Amps and that creates the heat. (please correct me if I am wrong). Also running on lower throttle is not going to help much because that will mean that the motor is designed with too high a gear and it will be running with low efficiency. Hence I rather run at the correct rpm meaning less energy use and less heat for the same give power.

Why do you guys think a higher voltage battery is very heavy? Is 3,3 pounds heavy to you? [url]https://lunacycle.com/52v-mighty-mini-cube-ebike-battery-pack-panasonic-ga-7ah-3-pounds/[/url]

Based on this new input do you have any other suggestions? I am considering the Q100C the Q128C and also the SWX all with the lowest possible rpm ofcourse. I do not find spare parts for the Q motors which would be easy to replace in case the clutch or gearing brakes. On the Q I would have to buy a complete motor to use as spare right? Would the SWX have more or less torque then a Q100C or Q128C?
 
Running lower voltage is not going to help since I need to pour in Amps and that creates the heat. (please correct me if I am wrong). Also running on lower throttle is not going to help much because that will mean that the motor is designed with too high a gear and it will be running with low efficiency. Hence I rather run at the correct rpm meaning less energy use and less heat for the same give power.
I think that is a fair description of the "catch 22" that a hub motor faces. A good rule of thumb is; "Never let the motor rpm fall below 1/2 no-load rpm." A high speed motor may be Current limited and it's actually doesn't reach the "on paper" no-load speed on the road.
An example in the extreem would be a high speed mini. It might have a no load speed of 27 mph, but is current limited to 22 mph on the street. So it's "1/2" climbing limit would be 14 mph, while a "260" mid-speed that also does 22 mph, but is rpm limited, so can dig down to 11 mph.

I am considering the Q100C the Q128C and also the SWX all with the lowest possible rpm ofcourse. I do not find spare parts for the Q motors which would be easy to replace in case the clutch or gearing brakes. On the Q I would have to buy a complete motor to use as spare right? Would the SWX have more or less torque then a Q100C or Q128C?
"Torque", as applied to electric motors is complicated and it's probably not correct to attribute a "torque" value directly to one motor or another. Perhaps a better way to think about this is motor mass and it's ability to absorb heat. Looking at the motor weights, we see the SWX falls between the Q100 and Q128.
I used to do light trail riding w/ a MXUS 2.3 Kg. mini on the front and while it's hard to describe "hill climbing performance, I will try.
Take a hill that is steep enough that if you were to try and scramble up on your own two legs, that you would probably have to reach down w/ your hands, well you could climb it w/the mini if you got a run at it. The faster the run-in, the further up you can go. But to sit a the bottom and start, things are going to bog down pretty Quick, or more likely, the frt. tire will probably just spin. If the same motor is on the back the traction will be better, but at the 800 Watt power level, it will just bog down to a stop. Adding a second motor improves things quite a bit, but doesn't double climbing performance. The rear tends to unload the frt. so it wants to break loose even easier
Of course, two motors doesn't ease the loads on the gears, but one instinctively realizes what's a no-no as far as they are concerned. I swear, w/the MXUS, I could feel the nylon gears flex and I would be really careful climbing over any branches over several inches in diameter. Logs, jumps and rock bashing were deffinately not in the program.
I guess what I'm trying to say is, hub motor are fine for groomed trails and Jeep roads. But the more serious MTB trails are better suited to a mid-drive.
 
I agree it is incorrect or too simplified to call it just torque. It should be torque at maximum efficiency and the corresponding speed at that efficiency and torque at 1/2 and maybe 1/4 speed. I guess one quickly moves in to graphs to describe it!

Anyways I'm still open for suggestions on a motor that has max efficiency at say 15 km/h or 9-10 mph and 135mm width or close to.

I understand your concern about "real" mtb riding and logs and small jumps will certainly be encountered along my trails. With a hub motor being really cheap and in bafangs case with replaceable parts it might be worth a try!?
If I was to replace my nice full suspension bike with another one that fits a bafang mid drive it would end up pretty expensive and I would worry about thrashing the motor on logs and rocks and also lacking the torque control of a Bosch or Shimano.
 
Tordnado said:
I have been reading and reading and I think I have found the best reasonable solution (probably not) but I need your input.

Please update with your result...
 
Ykick said:
Tordnado said:
I have been reading and reading and I think I have found the best reasonable solution (probably not) but I need your input.

Please update with your result...

If you are asking for my "best reasonable solution" it was the Q100, Q128 or the bafang swx but I find it hard to find comparable figures. I'll probably get an swx since I can buy spares for it and see how it goes.
 
Ykick said:
For what you’re describing you really need a mid drive motor, IMO. Bafang won’t fit on that bike? I’d get another bike.

The problem with that is that the best mid drives take away two of the front chainrings. That makes you dependent on the motor, which I don't think is the OP's intention.
 
Doesn't matter what wind you have or what voltage you run it at. Take whatever motor, hit it with enough current to make the make the torque you need to get up the hill. If you want to go faster or slower up that hill, just adjust voltage accordingly. If the motor melts down then you didn't have motor. The same motor wound 2T or 12T, run at 24V or 120V won't make a bit of difference to the result.
 
The motor you are describing as being perfect for your user profile doesn't exist (sorry), retailers only stock what the majority of customers actually buy (the bastards!). You can buy a cheap yescom motor and re-wind it to be a very slow winding, but...after all that trouble, you will come back with complaints about how it is slow on the flat lands. Then you might ask about running two batteries with a series/parallel three-pole switch (36V in series for 72V out, then off, then 36V in parallel for double amps on the hills). You might investigate if diodes or resisters are needed on the series connection, IDK...

As dogman said, ebikekit sells a slow 7T DD hub (which is out of stock) but...when they are back in stock, you could get one of those and mount it in a 20-inch rim, with torque-plates that adjust the axle so the frame still sits at the correct level. My opinion of the best compromise? The same as ykick:

Bafang won’t fit on that bike? I’d get another bike

Everyone who has an ebike NEEDS two ebikes. It will hurt less over time once you finally accept this. The good news is that you only need one battery pack for both of them (at least for the first year)
 
Tordnado said:
Ykick said:
Tordnado said:
I have been reading and reading and I think I have found the best reasonable solution (probably not) but I need your input.

Please update with your result...

If you are asking for my "best reasonable solution" it was the Q100, Q128 or the bafang swx but I find it hard to find comparable figures. I'll probably get an swx since I can buy spares for it and see how it goes.
I'll probably get an swx since I can buy spares for it and see how it goes.
When the motor costs $90, I'm not sure I would select it on the basis of parts avail. Especially when the replacement gears are probably for the 260 rpm version. That means they will likely not work w/ the 201 because the sun gear will be different.
If you are asking for my "best reasonable solution" it was the Q100, Q128 or the bafang swx but I find it hard to find comparable figures.
You didn't search out the thread I directed you to. I'll make it easy;
http://www.pedelecs.co.uk/forum/threads/q128h.20980/
http://www.pedelecs.co.uk/forum/threads/low-speed-hub.26190/
 
well, lets oversimplify some more.

A very small geared motor will work for you. but the catch 22 is that the slower you run it, the more of the tiny 200w of power you give it turns into motion. The rest is heat. Ever put you hand on a 100w bulb? there will be the same thing inside that motor. Give it more power, and it just gets even hotter, unless it's enough power to climb that hill fast.

So bottom line,, it will heat on the hills. If the hills are short, then it will heat for a short time. Especially if you are used to pedaling hard this will work, because you lower the load on the motor, and shorten the time. But believe me, the motor power gets addicting, and if you get in the habit of using it more, you can melt down those little motors in 45 min easy.

I'm not talking shit here, I do this deliberately from time to time. Take a motor and melt it, for the company I work for. We need to know what a new model can take, and what it can't. We don't sell the little motors anymore, because people don't pedal like you do. Or did? ( it's that addicting, the assist)

So anyway,, get a small rear geared motor, vs a whole new bike. Don't fuss too much about what brand, but get the slower rpm model, like 200 ish. Not a 350 rpm @ 36v wind. That will allow you to heat a bit less when going that slow.

One bit of advice remains,, don't put a load on that motor at less than 10 mph for very long. It's still gonna get hot.

Or two bits,, get off that throttle when you land the jumps.

Re the mid drive. Nobody misses those tiny front rings once they have a decent powered mid drive. they just stop riding up hills at 3 mph, and start riding up them at 10 mph. It's geared low enough for that. Start looking at serious money for your second e bike. Like a new trek or something, with shimano steps or bosch mid drive. Those bikes are taking over the alps in Europe. It's not happening because they suck.
 
Chalo said:
Ykick said:
For what you’re describing you really need a mid drive motor, IMO. Bafang won’t fit on that bike? I’d get another bike.

The problem with that is that the best mid drives take away two of the front chainrings. That makes you dependent on the motor, which I don't think is the OP's intention.

I’m in the “camp” that when you hang several pounds of electrical motor/battery on a bicycle you’re pretty much dependent on said motor/battery working.

Inexperienced BBSXX users probably don’t realize a correctly sized BBSXX chainring will be fairly small and well suited for majority pedaling in the event the system fails. But when the motor works, smaller chain ring is your friend.

Is it ideal and will you have all 21-30 gears of a modern mtn bike available? Of course not - even running a single chain ring 5 speeds is about all the angle I’ll apply to a motor powered chain line.

But again, I gotta motor, I’m carrying a motor, controller and battery, I’m gonna use it. Even if it’s applied only enough to overcome some of the disadvantages that come with hauling a motor and battery around.

I do wish the OP all the best with their project. Many of us would like to hear how it turns out?
 
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