HubMonster mid-drive (who says chains have to be noisy?)

I got to test ride my latest build yesterday. It uses a HubMonster high efficiency 6phase motor on the swingarm as close to the pivot as I could get it without raising the heavy battery higher. In this placement the motor has an effect on unsprung weight of just 2.7kg. With the big 21" moto wheels, the 28t front 57t rear gearing reduction is like putting HubMonster in a 13" OD wheel, so it will have no issues at all with any trail I have the balls to attempt. The top speed on flat road with the battery at 80V was 87kph, which is incredible with a no-load at that voltage of 91kph. The chain and wheel friction and windage are so small that they didn't affect no-load more than just rounding, since I took the chain off and still got 91. Achieving such a high percentage of no-load speed means it will be super efficient at any cruising speed and even going up very steep climbs.

Despite the consensus that moto chain is noisy, this drive is near silent even with 08B motorcycle chain. These big diameter tires are more quiet than my smaller wider tires on my other bikes and only sometimes can I hear the slightest hint of chain noise while riding. I'll do some drive-by videos from a stationary point at the same speed with my various ebikes to demonstrate.

With this gearing it's really something in terms of acceleration, and I haven't even pegged the throttle quickly or tuned the pair of Nucular 12Fs beyond the factory settings for acceleration other than phase and battery current. Though I made mounting holes for them, I didn't think I'd need to use my pair of 24Fs on this build due to the low gearing, and I was right.

It's disassembled now for some final metal work as well as grind and cut off a kilo or more of unnecessary steel and prep it for paint and make the covers. Here are a few pics in the meantime.

The bare bones frame with wheels mounted


As test ridden with 21s pack of Chevy Volt v2.0 module (52ah)


A close up of the motor mount. Note that the pink arrow points to a 1/3 circle of steel that the round axle sits in so the motor installs only perfect alignment. Those openings in the motor are to install blades like I've used with tremendous success before. That's the exhaust side. I will make a close fitting cover with a filtered intake on the left, and exhaust down and slightly rearward so mud and debris won't enter. This motor will run nice and cool even in the most abusive use.


More pics and video to come in the near future.

Dude that thing looks freaking sweet! Must be silly fast being so light

Where did you get the frame idea? Very wonky looking with the shock joining the two halves together!

also that chain is fairly large so it wont be nearly as loud as most of the setups people complain about

It's not very light. While I have it apart I'll weigh the parts to get an accurate weight, but the bathroom scale I used to get an idea put it something around 85kg, almost 190lbs. but yeah lighter than my other builds mostly due to a lighter front end.

I laid the bike out with an original plan to put the battery up higher, but I'm really glad I didn't do so with that 70lbs or so of concentrated weight. That's why the big hump in the top tube is there. It's quite heavy schedule 40 pipe, so no flex in it. I got tired of waiting to test ride and did a quick bike seat mount. If I go to the dirt bike moto seat I already have, then I'll need support tubes tying the top and bottom together and that rigid schedule 40 will end up overkill.

Regarding the chain, I think it's the equivalent of 428 motorcycle chain, and yeah I think it's a horrible mistake to run 218 or other small pitch chains. I've used bike chain before on some quite high power mid-drives, but always with small gear reductions and always with sizable drive sprockets, and they were even more silent than this one...of course those motors weren't spinning up to 1700rpm.

I think I'm going to make some minor changes to make it easy to swap a smaller capacity battery in and out. I run an even heavier battery on my big scooter, but it's mounted so low that I don't even notice the weight. The same isn't true on this bike, and I think I'll have more fun on my usual in town riding with half the battery weight. It's significantly more efficient zipping around due to the low gearing, that 21s26ah will be plenty. I can't get it to draw max power unless I accelerate hard on a fairly steep hill. On flat ground I've only gotten it to pull just over 17kw, but accelerating on hills I've seen 21kw+.

wow monster indeed

I'm sure detailed pics howto stuff would be very useful to lots of members and posterity

Is the tire tube, tied to the footpeg arm, another form of suspension?

skeetab5780 said:

Must be silly fast being so light

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Light? Those moto wheels weigh as much as a bicycle by themselves, each.

I’m sure its fast, though, since John uses dozens of HP in his machines (and then calls them e-bikes).

It’s a motorcycle. My last motorcycle measured 108 HP on the dyno, topped out around 150 mph, and got to 60 mph in about three and a half seconds. But I’m not crazy about motos, so I haven’t had one in many years.

re title, i do like the sound of a 10t motor sprocket spinning fast, seems to wear chains though :lol:

btw i tried that once, putting the motor on the swingarm, even went as far as centering it on the pivot axis. it still retarded the swingarm movement. but it's fine if not going off-road

E-HP said:

Is the tire tube, tied to the footpeg arm, another form of suspension?

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No, just extra security for the temporary battery install. The front is bolted into the rack, but not the rear, so I didn't want it to move.

Overclocker said:

re title, i do like the sound of a 10t motor sprocket spinning fast, seems to wear chains though :lol:

btw i tried that once, putting the motor on the swingarm, even went as far as centering it on the pivot axis. it still retarded the swingarm movement. but it's fine if not going off-road

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You must like the sound of blenders and other noise pollution too, not me I prize silence.

When installed in the pivot, it depends where the motor is anchored to determine how the thrust will act on the bike. If anchored to the swingarm then there will be anti-squat forces during acceleration and anti-dive under regen braking. These forces are opposite to a gasser moto, so they can feel quite different, especially the shorter the swingarm, the higher the pivot, and the lighter the load. Anchored anywhere on the swingarm has the same forces on the suspension other than the effect of unsprung weight, so hubmotor users may not notice a difference.

Having the motor anchored in the frame gives rise to all the traditional issues of chain drives...squatting under acceleration and diving while braking, not to mention the problems of changing chain length if the axle isn't in the pivot point. Just like the guy who put a hubmotor on a swingarm that was little longer than half the wheel diameter, so the rear of his vehicle bounced up and down with every blip of the throttle, these forces can be a negative when not properly considered in the design. I use them to create a positive impact, and yes I plan to hit some mountain trails with this build, though I won't be going for air with such lightweight suspension components.

Balmorhea said:

skeetab5780 said:

Must be silly fast being so light

Click to expand...

Light? Those moto wheels weigh as much as a bicycle by themselves, each.

I’m sure its fast, though, since John uses dozens of HP in his machines (and then calls them e-bikes).

It’s a motorcycle. My last motorcycle measured 108 HP on the dyno, topped out around 150 mph, and got to 60 mph in about three and a half seconds. But I’m not crazy about motos, so I haven’t had one in many years.

Click to expand...

By definition anything with two wheels is a bike, and adding any electric drive makes it an ebike, regardless of what laws are written by cyclists prejudiced against electrics are jammed down much of the world's throats. Go to a biker bar and start spouting off about how their hogs aren't bikes...see how far that gets you.

You're just jealous, because despite my rim and tire selection that mean virtually no flats that end up with a bit more rolling resistance than a bicycle tire, my ebike can cruise at your chosen cruising speed with greater efficiency with my advantage getting much more pronounced on hills.

John in CR said:

Overclocker said:

re title, i do like the sound of a 10t motor sprocket spinning fast, seems to wear chains though :lol:

btw i tried that once, putting the motor on the swingarm, even went as far as centering it on the pivot axis. it still retarded the swingarm movement. but it's fine if not going off-road

Click to expand...

You must like the sound of blenders and other noise pollution too, not me I prize silence.

When installed in the pivot, it depends where the motor is anchored to determine how the thrust will act on the bike. If anchored to the swingarm then there will be anti-squat forces during acceleration and anti-dive under regen braking. These forces are opposite to a gasser moto, so they can feel quite different, especially the shorter the swingarm, the higher the pivot, and the lighter the load. Anchored anywhere on the swingarm has the same forces on the suspension other than the effect of unsprung weight, so hubmotor users may not notice a difference.

Having the motor anchored in the frame gives rise to all the traditional issues of chain drives...squatting under acceleration and diving while braking, not to mention the problems of changing chain length if the axle isn't in the pivot point. Just like the guy who put a hubmotor on a swingarm that was little longer than half the wheel diameter, so the rear of his vehicle bounced up and down with every blip of the throttle, these forces can be a negative when not properly considered in the design. I use them to create a positive impact, and yes I plan to hit some mountain trails with this build, though I won't be going for air with such lightweight suspension components.

Click to expand...

i hate blenders :lol: but i do have several angle grinders and there's one that i'd say i like the sound of :lol:

there are ways to deal w/ the squatting. the motor is mounted low enough such that if you look closely my chain almost crosses the pivot axis. that's possible because it's not a "thru-bolt". and the chain is flying like 3mm above the crossmember where the lower shock mount is attached to. so the resulting geometry provides a decent amount of anti-squat

the chain growth is easily fixed by tensioner w/ a hard plastic roller. the rubber ones wear out fast

overall this setup works so much better than when i had my motor on the swingarm

Poor seat iand shock it looks like it's just floating there I don't see how it's it's going to support Big John . It looks like it would tweak but then again I don't have my hands on it.
All thiis on two Russian 6f controllers wow. I think I will buy the 12fet. What display are you using ?

Overclocker said:

overall this setup works so much better than when i had my motor on the swingarm

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In what specific ways? I want to understand. I think it's guys being so accustomed to the feel of the traditional way using gassers that they don't like the feel because it's new. To me anti-squat and anti-dive are desirable as longas it doesn't get so pronounced that it's "jacking" the seat when accelerating.

999zip999 said:

Poor seat iand shock it looks like it's just floating there I don't see how it's it's going to support Big John . It looks like it would tweak but then again I don't have my hands on it.

Click to expand...

I've done the horizontal seat tube before and it works fine with a thick wall tube. On this one I started with solid round stock, turned it down to the correct diameter and drilled a hole down the center to shave some weight. It's still overly strong.

JohnCR
All thiis on two Russian 6f controllers wow. I think I will buy the 12fet. What display are you using ?
I Papa John I know how you love the Russians if you don't say yes you're in a big trouble right .
Haha

999zip999 said:

JohnCR
All thiis on two Russian 6f controllers wow. I think I will buy the 12fet. What display are you using ?
I Papa John I know how you love the Russians if you don't say yes you're in a big trouble right .
Haha

Click to expand...

Sorry about the typo, those are dual 12F controllers along with a Nuc display. The 12F on my son's bike is plenty pushing a 3 turn MXUS 3K Turbo in a 22.5" OD 18" moto wheel.

John in CR said:

Overclocker said:

overall this setup works so much better than when i had my motor on the swingarm

Click to expand...

In what specific ways? I want to understand. I think it's guys being so accustomed to the feel of the traditional way using gassers that they don't like the feel because it's new. To me anti-squat and anti-dive are desirable as longas it doesn't get so pronounced that it's "jacking" the seat when accelerating.

Click to expand...

View attachment 2


like i said the motor-on-swingarm retards movement so it feels harsh on fast hits. it wasn't horrible because i had a small light motor right on the pivot axis but still. yours is a lot heavier and closer to the wheel axle so the negative effects will be more pronounced





quick and dirty calculations on my current setup. ~120% anti-squat fully-extended. ~100% anti-squat at ~30% sag.



(from tony foale used w/o permission)

since you don't have the chain pull component then the anti/squat forces come from your swingarm angle (plus the wheel torque cranking on the swingarm?) so do the calculations. when sagged it seems your pivot is way lower than your wheel axle. i haven't figured out the calculations for a hubmotor setup

With my large sprockets to keep things silent things would get horrible in terms of the chain pull effect on the suspension if I put the motor on the frame, unless I gave up regen braking. I'm just after some light trail riding and street riding. Yours look like much more serious dirt bikes. Here most roads headed uphill turn into a dirt road higher up the mountain and turns into a trail further up. I want to go exploring where I've never been, and need plenty of battery just to get to where the pavement ends. 2.5kg or so of extra unsprung weight is a small price to pay.

The drive sprocket's teeth look shallow and pointy. That should allow the sprocket teeth to meet the chain more gradually (softly). The chain has to be tensioned more though. Those are some impressions I've picked up.

How does the motor look in this setup with the fan blades installed on the shell? I just pulled apart my hubmonster for ventilation and I'm trying to get an idea for fan blade spacing and how they create enough vacuum to pull air out through the holes. Also, regarding the close fitting intake cover, you might try using a brush seal. They make ones with flexible backings, so bending one into a circle to fit around the left side of the motor wouldn't be too hard.

Any progress?