Hill Scooters' Scooter

I picked up this frame from Hill Scooters a while back. I've had it in a few different configurations, but haven't quite figured out the right build for it.

In the above picture, I thought I'd get cute and try to "mini" it with some 14" motors. It looks...ok, but you can see I had to install a monsterously long rear suspension to shove the swing arm back to create ground clearance. Also, these motors are...insufficient to the task. I thought they were geared hubs, which would make some nice torque -- I was wrong, they are tiny little direct drive setups.

I'd like to find a motor setup that works and makes this a peppy little fun zip around toy. Speed is not a top priority; anywhere in the 20's is fine. I do not wish to (re)build the battery or change out the controllers. It has a 52v battery with a 14s5p Molicel p26a setup. The battery can comfortably push 100A (technically, 5x35a or about ~175A, but I'm still using the spade connectors on the the battery pack baseplate, so I don't want to go higher.) Still, 50 battery amps per motor is not small potatoes.

The controller is a Spintend 75v100A Dual controller. This can handle providing each motor up to 100 phase amps a piece.

The front fork is a 135mm dropout and the rear swing arm is 150mm; though above I've used some spacers to make the 135mm motor work.

I think I should go back to the 20" wheels this is designed for:


(When I had transplanted some A2B Metro parts onto the frame.)

I'd like some opinions on what motor setup to go with; I've been eyeballing a few options:

1. Dual 9C RH212 DD - (motor sim)
   Love DD hubs -- quiet, regen, look great, etc. These look like great performers, keep cool, and would likely just be an all around solid option. Also, middle of the pack in price.
   
   
2. Dual GMAC 10T - (motor sim)
   TORRRRRRQUE. Holds that 200lbs of torque longer than the 9c's by a good margin; I've got to believe this would be the more fun ride. They come with the downsides of being noisier and about $200 a piece more expensive. It's also listed at 138mm OLD, which is a smidge too wide for the front, and I'm not sure how much a suspension fork would appreciate that flex.
   
   
3. Dual Leaf 60v2000w
   Lots of praise around these parts about the solid reliability of the leaf motors; especially if you ferro+sink them. By far the cheapest option; no built in temp sensors. Available in any rim (they have these in 16" moto's, 20" fat and 20" skinnies). Don't want to go the fatbike tire route, though, tbh. Likely the heaviest of the bunch; no entry in the motor sim.

I'm open to thoughts and other suggestions as well!

Are you sure you want dual motors? thanks to the 20" wheels you can push easily 2kw peak into grin all axle or MAC and see in excess of 80ft-lbs ( that's a lot )

10T MAC? probably 50% more than that!

neptronix said:

Are you sure you want dual motors? thanks to the 20" wheels you can push easily 2kw peak into grin all axle or MAC and see in excess of 80ft-lbs ( that's a lot )

10T MAC? probably 50% more than that!

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Both the 10T and the 9C show an initial 200ftlbs off the line for full throttle.

I've had lots of bikes that go fast (plus, I'll be getting the allaxle fat when it hits for my "commuter" radrunner); I want something that goes up trees. So, yeah, dual for fun. That's also why I'm not going to worry about putting a larger capacity battery on this -- the 52v high amp pack fits the build theme better.

if you are only looking for 20's for top speed, and want dual motors, have you considered some geared hub motors? lightweight, and more torque than direct drives. i see you mention the gmac's, maybe get a freewheeling motor for the front? trying to turn with a clutchless motor is less than ideal if you are also slowing down IMO.

ganzey said:

i see you mention the gmac's, maybe get a freewheeling motor for the front? trying to turn with a clutchless motor is less than ideal if you are also slowing down IMO.

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Yeah, that's why they are on the list -- absolutely the most torque (without having to change controller/battery setup).

I think there's a tradeoff in going with a clutch on the front wheel specifically as it's extremely effective at regen braking in that config.

chuyskywalker said:

Yeah, that's why they are on the list -- absolutely the most torque (without having to change controller/battery setup).

I think there's a tradeoff in going with a clutch on the front wheel specifically as it's extremely effective at regen braking in that config.

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yes good point, I only implemented front regen brake out of necessity because the scooter only had 100mm dropouts up front and regen in the rear was a very fine balance between barely slowing me down and the rear tire skidding/ hopping unless a shifter my weight back to the point i am almost sitting on the tire, with your 135mm dropouts i just assumed you would use discs, my bad.

can you setup 2 separate brake inputs with vesc that are tied together via can? IE could you vary them independently from 2 separate brake/throttle's, or are they tied together and only adjusted via the app ? ive never ran into that scenario.

i did find fwd to be the most fun offroad though. my little scooter has a 16" moto rim up front with a qs212 and a knobby dirtbike tire, 12" rear (16"tire), and its a blast ripping around trails, just gun it and it will pull you through turns, pull the rear brakes and the tail end will whip around. i converted it to rwd with a geared hub and its was just meh, wheelied like crazy but switched it back to fwd after a week or so. tried awd on my crussis cross and switched it to rwd after a month or so, but wiidened the rear dropouts and stuck a 45h hub in and its just crazy, on hard accel it itll hop the rear tire, proabably fine on the street with gets a little tiring to ride offroad, , i barely even ride it anymore because it just feels to awkwardly long. IMO stick to the smallest wheels possible, with 26"/20" on the crussis i much prefer the smaller scooter with 20"/16". what is the wheelbase on yours if you happen to know offhand?

ganzey said:

can you setup 2 separate brake inputs with vesc that are tied together via can? IE could you vary them independently from 2 separate brake/throttle's, or are they tied together and only adjusted via the app ? ive never ran into that scenario.

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No; in the canbus combined mode, the controlling VESC gets the signal and forwards the control info to the second one. In fact, you can get some wildly wacky behavior if the second VESC has an "app" enabled for control purposes.

What you *can* do, however, is change the motor tune for the front motor so that it has lower amp limits for battery, phase, and regen if you want it to be less impactful than the rear.

ganzey said:

what is the wheelbase on yours if you happen to know offhand?

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No idea

Decided to go with the leaf motors; just can't beat the fact that I'll get two motors for roughly the same price as the other ones. Should see them in the next week or two.

Supplies trickling in.

(Two hub sinks and some statorade; where it's at, where it's at)

“I got two torque arms and a hub motor. Where it’s at?”

Motor's arrived



Packaged very well; actually the best packaging I've seen on a motor from anywhere. Everything fully secured (tape/zipties) and styrofoam aplenty.



Front and back view. Notably, the signal wire bundle has a 6th cord in it; which is odd since these aren't supposed to have temp sensors in them.



I guess they just connect it to the B hall sensor so someone could use it as a speed sensor. A bit odd -- but I'm happy it's there so I can desolder that and re-use it by attaching it to and NTC thermistor and ground. Yay temp sensing!


35mm was at least accurate and there's a close up of the laminations. I count 100 stacks, so 0.35mm laminations also confirmed.



Finally, I pulled out a spoke so I could install the hubsinks, and after that the spoke wrench juuuuuust fit in to tighten it back on.

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Hopefully will get the temp sensor installed tomorrow along with ferrofluid and then button it all back up. Maybe add some silicon to the side covers as that's one thing not present with this motor. Nor was there any locktite on the sideplate screws. So that too.

And then I do it all again!

Getting the NTC's soldered up to wires and the legs protected.




Last time I did this, I only used the High Temp epoxy to put the sensor in and that was a NIGHTMARE holding it in place while waiting for it to cure enough to not move all over the place.

This time, I held it in place, and put a few drops of CA glue over the probe then sprayed some accelerant on to it. BAM! Instant hold, no more fuss. I came back in later (see above) and applied the gray epoxy as the long term hold solution.

Also got one of the motors hubsinked (other tonight) and other side plates siliconed and locktite'd.

Tomorrow, after the epoxy has had some time to cure, I'll get the motors statoraded, slap some silicon on these plates and button it all back up. Then it's on to soldering on bullets for the phases and converting the hall into the JST connections the VESC uses.

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I also found out that the two Grin V7 Regen torque arms I have are 12mm versions -- these motors are 14mm. Ooops! Thankfully Grin came through and is sending out just the spline's for the 14mm setup so I can uses these. Looking forward to worry free regen on rear *and* front. (I think their testing showed that the axle is more likely to shear than the torque arm failing, lol)

Noice.

Getting those sinks in between these close, short spokes was real finicky, but wiggling them about got 'em around the hub.

Great progress! Are the motor axles 14mm on both ends? I just got in my Leaf 35mm, cassette version in 177mm dropout width, and the axle threads are actually M16 on the brake side, M14 on the cassette side...

kuromaku said:

Are the motor axles 14mm on both ends? I just got in my Leaf 35mm, cassette version in 177mm dropout width, and the axle threads are actually M16 on the brake side, M14 on the cassette side...

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14mm on both sides -- different sizes on the two sides is....really weird, honestly.

Motors finished up. Both sides on each silicon sealed and loctite'd. Sinks fully on and secure, tires and tubes installed. Only popped one tube today!

Got the connections temporarily setup (bullet connectors and wago's for the sense wires) and the motors mounted with no torque arms yet. But, for a freespin in the air, this works fine.



Ran a test and the motors kV is exactly as requested in my order; @52v these are pushing 25mph. Perfect.

Wanted to generate some heat in them, but can't ride because it's not torque arm'ed yet. Soooo.... I turned on Field Weakening and set it to a MASSIVE 80A. The motors make some pretty novel sounds when they are going SIXTY MILES PER HOUR, lol. Wires started to get pretty toasty too -- I don't think these can really handle 100A sustained, but for bursts it should be fine. Once it's up to speed, it'll probably only pull 20a per motor or so anyway, so unless I'm hitting a lot of 20% inclines, I think this should be fine.

Also, note to self: do a better job cleaning up the thermal paste before spinning wheels at 60 -- ceilings do not need thermal paste.

chuyskywalker said:

View attachment 352916
Motors finished up. Both sides on each silicon sealed and loctite'd. Sinks fully on and secure, tires and tubes installed. Only popped one tube today!

Got the connections temporarily setup (bullet connectors and wago's for the sense wires) and the motors mounted with no torque arms yet. But, for a freespin in the air, this works fine.

View attachment 352917

Ran a test and the motors kV is exactly as requested in my order; @52v these are pushing 25mph. Perfect.

Wanted to generate some heat in them, but can't ride because it's not torque arm'ed yet. Soooo.... I turned on Field Weakening and set it to a MASSIVE 80A. The motors make some pretty novel sounds when they are going SIXTY MILES PER HOUR, lol. Wires started to get pretty toasty too -- I don't think these can really handle 100A sustained, but for bursts it should be fine. Once it's up to speed, it'll probably only pull 20a per motor or so anyway, so unless I'm hitting a lot of 20% inclines, I think this should be fine.

Also, note to self: do a better job cleaning up the thermal paste before spinning wheels at 60 -- ceilings do not need thermal paste.

Click to expand...

What winding did you get?

6T?

ebike4healthandfitness said:

What winding did you get?

6T?

Click to expand...

No idea what the actual turn/wire-count is -- I just asked to hit 25mph @ 52v and they said it'd be a 9 kV motor; the pictures tell me they just increased winding to make that the right value (since it's not, like, empty or anything). Seems to line up pretty much dead on with the motor simulator.

TBH, I did try to get them to nail down an answer on the turn count and wire gauge/amount, but getting technical details out of their email replies is like pulling teeth....across an ocean...in another language. So...yea... It's a minor complaint, all things considered, since the motors came out perfectly on spec.

chuyskywalker said:

No idea what the actual turn/wire-count is -- I just asked to hit 25mph @ 52v and they said it'd be a 9 kV motor; the pictures tell me they just increased winding to make that the right value (since it's not, like, empty or anything). Seems to line up pretty much dead on with the motor simulator.

TBH, I did try to get them to nail down an answer on the turn count and wire gauge/amount, but getting technical details out of their email replies is like pulling teeth....across an ocean...in another language. So...yea... It's a minor complaint, all things considered, since the motors came out perfectly on spec.

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It looks like they gave you the 6T which works out to be Kv 8.7:


6T is also one of the windings (along with 3T and 11T) that has maximum copper fill.

Good to know; and yeah, the 8.7Kv seems to actually give me a bit closer to the 25mph my display shows when I've got the tire size and what not calibrated for the motor/tire setup.

Chuyskywalker,

Have you dared to see what kind of road top speed you can get with field weakening applied?

One calculator I used said it would take 8500 motor watts to hit 60 mph.

ebike4healthandfitness said:

Have you dared to see what kind of road top speed you can get with field weakening applied?

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It's not off the build stand yet

Even then, I doubt I have enough power from the battery to reach whatever the maximum would be, nor could the controller put up with it. I might, miiiight put 20 or so amps into field weakening, but I've never been much of a fan of that approach. IMO, if you want speed, get the right winding/tire/voltage for it. I wanted better amp handling.

ebike4healthandfitness said:

One calculator I used said it would take 8500 motor watts to hit 60 mph.

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Where is a calculator for that? And, to be fair, when I hit 60mph it was up on a stand with zero real load (other than the wheel and tires) -- it would NEVER hit that with someone on it. The controller couldn't put out both the FW amps and actual phase amps to make that happen.

chuyskywalker said:

Where is a calculator for that? And, to be fair, when I hit 60mph it was up on a stand with zero real load (other than the wheel and tires) -- it would NEVER hit that with someone on it. The controller couldn't put out both the FW amps and actual phase amps to make that happen.

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I used the following calculator with "roadster" selected as the type of bike and the rest of the settings left on default:


P.S. I thought your controller could put out up to 100 amps per motor? But yes, you do make a good point about the battery being the limiting factor. I forgot about the battery....I was just thinking about the controller. A little non lipo battery like that is probably good for 40 amps....so 20 amps per motor if evenly split. 20 amps per motor at 52v leaves a lot room for future power upgrades especially as the tire diameter is only 20" (with hubsinks) and that chassis (and fork which is triple tree and shorter in length than the typical fork for 26" tire, 27.5" and 29" tire when extended*) looks pretty tough.

*And therefore I hypothesize less suspectable to damage from forward movement (which puts leverage on the fork internals) caused by an accelerating front hub motor.

I don't think that's a good calculator to go by, necessarily.

For starters, getting above 30mph, wind resistance really starts to eat you alive for power needs. Second, even as you add field weakening, you still need the regular phase amps to push the motor faster while under load. And since you are eventually limited by how many amps total (phase + fw for each motor) you would never get anywhere near the unloaded 60mph I did on the stand. The 20" tires are a major limiting factor here as well -- you have to rotate insanely fast to hit 60mph. Also, the sounds it was making with having two phases pushing amps was...not great. I don't believe it would be sustainable for any real period of use.

Putting all that aside, the controller would need to be much more powerful. Trying to make it possible with the grin simulator it looks like I'd need 100/200 controllers with a 30Kv motor to get an 60mph on 20" tires.

ebike4healthandfitness said:

A little non lipo battery like that is probably good for 40 amps....so 20 amps per motor if evenly split. 20 amps per motor at 52v

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...

chuyskywalker said:

It has a 52v battery with a 14s5p Molicel p26a setup. The battery can comfortably push 100A (technically, 5x35a or about ~175A, but I'm still using the spade connectors on the the battery pack baseplate, so I don't want to go higher.) Still, 50 battery amps per motor is not small potatoes.

Click to expand...

chuyskywalker said:

I don't think that's a good calculator to go by, necessarily.

For starters, getting above 30mph, wind resistance really starts to eat you alive for power needs. Second, even as you add field weakening, you still need the regular phase amps to push the motor faster while under load.

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1.) According to the e-bikes.ca motor simulation example you used 60 mph "only" needed 7023 watts with dual Kv 30 motors:


.... So actually 8500 watts (given by the calculator I used) is conservative by comparison.

2.) Sorry for missing the details on your battery. 100 amps continuous discharge works out to 50 amps per motor. At 52 volts this a good amount of maximum power. With an motor Kv optimized for top speed you would probably be around ~45 mph. But I realize the 6T winding you chose (which has Kv of 8.7) is not optimized for top speed:


I guess the question I now have is how much can field weakening extend your mph? I am assuming it will not be the same as if you had a Kv optimized for top speed like the 3T winding:


But how far off would it be? How much overhead does field weakening add to the power consumption? How much heat does field weakening add to the motor?

I would be interested in using this myself one day even if field weakening only boosted mph to 30 mph (up from 25.9 mph). This provided power consumption added from field weakening wasn't too bad (reason: low speed performance is more important to me than high speed performance).