Want suggestions: DD hub motor for recumbent

[Phalix]

Hi,

I need help choosing a hub motor for my recumbent lowracer with 20" wheels.
This forum has so much experience, I am really curious to hear your suggestions. I can only get so far on my own


My Goal: Cruise at 40Km/h (~25mph) for enormous distances flat lands, no hills, throttle only - For the lowest wh/km figure

Therefore I am interested in the highest efficiency at this cruise speed of 40Km/h.

Battery: not yet build can be any voltage, dont care.
Motor type: I have it configured currently with a BBS02 mid-drive, but I am not happy with the cruise efficiency. So I am looking at hub motors
Motor placement: Rear makes most sense I think? But open to any of your suggestions
Gears: I have a 9speed cassette, so a freehub body on the motor would be preferable
Wheels: As mentioned 20" 406 . Larger will not fit the frame

Choices I am looking at currently:
9C RH212 Widely marketed as a premium motor, but got scared by some posts on here about cracked hub shells. Weirdly enough this motor comes out less efficient than the MXUS XF40

MXUS XF40 (3005) Looking for a reputable seller if this motor is a good choice

My current research:
https://ebikes.ca/tools/simulator.h...&hp_b=0&throt_b=11.489368209472575&bopen=true

 

[calab]

Leaf 35h 1500w direct drive
https://www.leafbike.com

 

[Chalo]

As calab said, Leaf Bike 1500W. It's pretty darned efficient, pretty darned cost-effective.

Since you're already using a gimpy recumbent, you should consider adding a fairing and/or tailbox to reduce power requirements at speed.

 

[dogman dan]

slow down 2 mph, to 18 mph for more efficiency with the setup you have. It will gain you far more than any differences between a mid drive, or different brands of hub motors. You are already pretty efficient, except when you go fast.

The effect may be less than on an upright bike, but its positively amazing what slowing down to 18 mph does, vs 20 or higher. While slower, its not that slow. Not as much as a crawl as 15 mph. Of course, you want real efficiency, slow to 15.

Chalo has it exactly right, a fairing may gain you much more than changing motors. Then slow to 18.

But if you insist on a hub motor, E Bikekit sells a direct drive hub motor that has a slow winding. On 13 or 14s, its maximum speed is about 18 mph in a 20" wheel. This is what I did with my most efficient e bike I ever built. It was so efficient because I could never go 25 mph on it, unless downhill. So I never got throttle creep, never rode fast, and could go amazing distances on that bike. The slow motor meant I always rode wide open throttle, where the motor makes the least heat, and runs at its max potential efficiency, but not at fast speed catching wind drag.

But to do the same thing, all you have to do is pick a lower gear with your mid drive. 8)

 

[999zip999]

A mxus 3,000 45mm magnets and width is more efficient then a 9c 28mm or the bigger leaf motor 35mm if you choose a direct-drive I would get the leaf and a 40 amp controller . do they sell a controller that has the 6-pin CA plug ?
Yes at 18mph you can see the butterflies at 30 miles an hour the butterflies go splat on your face.

 

[Phalix]

Leaf 35h 1500w direct drive
https://www.leafbike.com

That is a fantastic suggestion thank you! I had no idea these motors had such outrageous peak efficiency numbers. It looks like it outperforms any other motor in the 15km/h - 40 km/h speed segment (20" wheel context) , only losing out at very low rpm in the efficiency department.

Do you know if these motors are represented in Grin Tech's motor simulator?

 

[Phalix]

slow down 2 mph, to 18 mph for more efficiency with the setup you have. It will gain you far more than any differences between a mid drive, or different brands of hub motors. You are already pretty efficient, except when you go fast.

The effect may be less than on an upright bike, but its positively amazing what slowing down to 18 mph does, vs 20 or higher. While slower, its not that slow. Not as much as a crawl as 15 mph. Of course, you want real efficiency, slow to 15.

Chalo has it exactly right, a fairing may gain you much more than changing motors. Then slow to 18.

But if you insist on a hub motor, E Bikekit sells a direct drive hub motor that has a slow winding. On 13 or 14s, its maximum speed is about 18 mph in a 20" wheel. This is what I did with my most efficient e bike I ever built. It was so efficient because I could never go 25 mph on it, unless downhill. So I never got throttle creep, never rode fast, and could go amazing distances on that bike. The slow motor meant I always rode wide open throttle, where the motor makes the least heat, and runs at its max potential efficiency, but not at fast speed catching wind drag.

But to do the same thing, all you have to do is pick a lower gear with your mid drive. 8)

I am well aware of wind resistance increasing in a squared fashion haha. This advice goes for every motor. I deliberately set the 40km/h condition to get an idea of what motor is most efficient given this constraint.

I extensively tested various conditions for my BBS02 but the max efficiency allways left a lot to be desired. Especially if I compared my numbers to those given by Grintech's simulator https://ebikes.ca/tools/simulator.html?motor=MX3006&batt=cust_48_0.2_40&wheel=20i&frame=full&mass=120&hp=0&motor_b=MBBS02&batt_b=cust_48_0.2_40&wheel_b=20i&frame_b=full&mass_b=120&hp_b=0&bopen=true&mid_b=true&gear_b=1&tf_b=42&tr_b=11&autothrot=true&autothrot_b=true&throt_b=6.925794763860592&throt=5.5247068095617955&eff_b=97&cont=PR&cont_b=PR

I suspect the inefficiency is largely due to the long chainline of the recumbent. That or Grin's numbers are simply off. The speed estimates GrinTech's sim gives for the BBS02 are wrong compared to what I see in the real world

Not going to toss my BBS02, it will find new life on my regular bicycle.

Do you think I might have done something wrong in my testing? To me it makes perfect sense that a motor that doesn't have to transmit it's power through a number of gears and chain will allways be more efficient. What's your thought on this? Even grinTech gives a drivetrain efficiency estimate of 97%. That 3% drop is not insignificant and likely will be more on a recumbent given the longer chain and pulley system

 

[calab]

Go down to the bottom and click more motors in the motor sim and the trip sim, Leaf is only represented in 5T but you can change the kv if you know the others and they are listed in the big Leaf thread, you might have to hunt for that info, I always do as no one has cleaned it up to put all the pertinent info on the first post. I usually go looking for the specs to put into the spoke calculator. Unfortunately the Leaf isnt in the spoke calc, and might not be in the trip sim.

Do you know if these motors are represented in Grin Tech's motor simulator?

 

[Phalix]

Go down to the bottom and click more motors in the motor sim and the trip sim, Leaf is only represented in 5T but you can change the kv if you know the others and they are listed in the big Leaf thread, you might have to hunt for that info, I always do as no one has cleaned it up to put all the pertinent info on the first post. I usually go looking for the specs to put into the spoke calculator. Unfortunately the Leaf isnt in the spoke calc, and might not be in the trip sim.

Do you know if these motors are represented in Grin Tech's motor simulator?

Thanks a lot.
https://ebikes.ca/tools/simulator.html?motor=MX3006&batt=cust_52_0.2_40&wheel=20i&frame=full&mass=120&hp=0&motor_b=Leaf%205T&batt_b=cust_52_0.2_40&wheel_b=20i&frame_b=full&mass_b=120&hp_b=0&bopen=true&autothrot=true&autothrot_b=true&throt_b=89.3&throt=100&cont=C25&cont_b=C25

Weird how the efficiency improvement is not shown in the simulator. Did I miss something or are Grins numbers wrong?

 

[dogman dan]

You could be riding it in too high a gear for the speed you are in. Maybe not, but my limited experience with a mid drive indicated that the rider gets little seat of the pants input when riding if they are in too high a gear. Ride with the motor going fast as possible, but in the lowest gear it will do that in. WOT in a low gear better than mid throttle in a high one.

The other problem could be the load for the motor size, some of us are big boys. This should not be the problem, but the more you weigh, meaning over 300, the more you need that really low gear.

Sorry if I insulted you, but so many others without your knowledge read this too, so I dumb it down in replies.

Anyway, the best way to get the max efficiency is to ride with a cycleanyalyst or other watt meter. Maybe you do this too.

Everything I know about how to stretch range comes from doing that. Sometimes its just a bit steeper than you thought, but looks flat. Sometimes you have less tail wind than you think, or a side breeze affects you more than you could dream it does. But the wattmeter tells all, and lets you know when you can ride 25 mph and make it, or you need to slow to 15-18. Pedal harder was not an option for me, as a west nile long hauler.

Any kind of testing you do needs to be done on a circular route, so you go uphill and down, and about equal distances into and away from the wind, including both side winds, so it all averages out. Do these tests with typical weather, so they can compare over years of time. So wait till winter is over for tests you can compare to others. I used to think my battery was on its last months in winter, till an 80 degree day came along and then WOW!

Lots of motors out there with better efficiency these days, and I never tested them. But in general, the worst will equal the best, if you slow down the worst by 2 mph. Especially in the lower speeds. I found 18 mph to be the fastest speed I could ride, and have the pedaling effort significantly affect the range. It was simply amazing how much farther I could go at 18 mph, vs 20 mph. Especially if the bike kept throttle creeping up to 23 mph. Drop a gear lower with your mid drive, and eliminate throttle creep, and you might be surprised how much you let that happen without really noticing.

But if you put a very strong 30 mph dd motor on that bent, it will seem hard to ride it efficiently. But it will be easy to ride it more fun!