Hub motor on 17" moped rim

[DmitryK]

Hi guys. I have a vintage trike. It's powered by a 49cc t2 motor that powers the differential on rear axle. Right now the bike weighs at least 200 lbs and climbing the more improvements I make. It's geared super low for high torque but low high end speed. My goal is to find a happy medium of hill cllimbing and decent top end. I can get good top end with a big bore kit and higher hearing. But I need an electric hub front wheel conversion for MOSTLY take offs and hill climbing. The gas motor can power the trike on straight aways and through minor hills.

All my rims are 17x1.4. I think a 6000-8000W electric motor is a good option in my case, but I'm open to suggestions. Right now my front end consist of KX65 forks with modified triples, CR85 rim with disk brake. The goal is to lace the hub motor into an 17x1.4 rim. I do need the front disk brake function, so I'll probably be adapting a rear hub motor on my front wheel. I'm a noob in the ebike scene so help along with my project. I'm attaching a photo of my trike.

Here's a few questions right off the bat:
- What capacity motor is suitable for my machine
- Will the right size spokes be available
- Where to buy parts

 

[E-HP]

Since it seems like any solution will require a fair amount of custom fabricating, I'd suggest leveraging/augmenting your existing drive train, and supplement the gas engine with an electric one. If you use a freewheel/clutch, then you would have minimal drag when using the gas engine alone. You could still use a hub motor, but in a Stokemonkey like configuration: https://ebikes.ca/product-info/retired/stoke.html

A big hub motor in the front isn't generally a good idea, even with the weight you're carrying. Electric motors have a lot of torque down low, so the wheel will likely spin if you have a big motor. You'd want a geared hub to avoid the drag when not using electric, but geared hubs aren't generally available over 1000W.

 

[goatman]

the rear axle, is it limited slip, posi or just one wheel gets powered?

east gem has electric motors and gear boxes

http://eastgem.net/accsesories.html

dont know how you will fit a 8000watt DD up front. you need a thru axle motor like grins, but more powerful. how many spokes on front rim?

https://ebikes.ca/product-info/grin-products/all-axle-hub-motor.html

 

[DmitryK]

Here's a shot of the drivetrain. It's the Peerless Gear differential. There's no adding or subtracting to my existing drive train, so mid motor placement is not an option.



My front wheel is the standard 17x1.4 aluminum rim off Honda CR85 dirt bike; it has 28 spokes if I countd right. I don't care if the existing front wheel stays or goes. I can lace my electric hub motor into a new 17" rim if the spoke placement is an issue. Also, the front hub will do only takeoffs and hill climbing; the gas motor takes over on straight aways. Quite possibly I do not need an 8000W DD motor. Maybe a 3000W one will siffice for my application?

 

[goatman]

i played with those cheap ebay 49cc motors and i think my top speed was about 50km/h

most electric hubs are 36 spoke

the all axle hub is 32 spoke holes , lace it in a 32 hole rim.
whats your axle diameter in front fork?
then its just figuring out the torque arm
and you need a way to put a couple amps into the motor to overcome cogging and/or you could try to incorporate PAS into your system to power the electric motor in sync with the gas motor. a PAS potentiometer would be handy also

try to get the attention of ES member, John in CR

 

[E-HP]

Here's a shot of the drivetrain. It's the Peerless Gear differential. There's no adding or subtracting to my existing drive train, so mid motor placement is not an option.

microcar differential.jpg

My front wheel is the standard 17x1.4 aluminum rim off Honda CR85 dirt bike; it has 28 spokes if I countd right. I don't care if the existing front wheel stays or goes. I can lace my electric hub motor into a new 17" rim if the spoke placement is an issue. Also, the front hub will do only takeoffs and hill climbing; the gas motor takes over on straight aways. Quite possibly I do not need an 8000W DD motor. Maybe a 3000W one will siffice for my application?

IMG_20200824_220126653.jpg

You could add a chainring parallel and attached with some posts to the existing gear. I also see what looks like through bolts that are attaching the existing gear. Another place to mount the chainring with the same bolts, but on the right side. That is closer to the center of the axle and you have more room to work with for the motor mount.

Anyway, seems your set on a front hub, so I think you're biggest issue is the brakes. You need it to be pretty strong given the amount of weight it has to stop on it's own. Hubs are mostly 36 holes, so that's an easy check.

 

[E-HP]

then its just figuring out the torque arm

I'd probably fabricate steel dropouts that can be mounted to the fork with bolts through the axle holes, and tackle both issues at once. Some measurements between the existing forks would be helpful to see what would fit, or not.

 

[DmitryK]

Holmes Hobbies used to sell 17" hub motor specific spoke rims, but not anymore. Maybe I can find a used one? Moped rims on high performance ebikes has been a hot topic on here. Here's a sticky thread about it: https://endless-sphere.com/forums/viewtopic.php?t=69104 started by spinningmagnets. I can't imagine people people stopped putting 17" rims on their bikes, so the quest continues.

Anyway, my front fork is off Kawasaki KX65 kid dirtbike. Inside spacing between fork legs is about 4.5". Front wheel axle diameter is 12mm.

Regarding my existing 2t motor: it's not a cheap China one; it's an Italian Minarelli V1.

 

[goatman]

what speed do you do or want to do? your not doing 30mph are you?

i dont think you need electronic free wheeling with a grin thru-axle do you? its a thru axle so no cogging like most DD hubs

if you got a phaserunner and a high amp battery you could put 3000watts through it and program regen at 1500 watts to be your front brake

if you did that with a gas motor you would probably get something like 70% regen ah recovery into your battery :lol: :lol: :lol:

did you see the sailboat with the motor and phaserunner?

https://endless-sphere.com/forums/viewtopic.php?f=39&t=108411

 

[spinningmagnets]

I dont know what axle would be guaranteed to fit your fork/drop-outs, but...once you actually get the rim you want plus the hubmotor you want, you can measure them to see what size spoke would work.

There are online spoke calculators that seem to work fine. I have ordered spokes from danscomp twice, happy so far with them. Their phone customer service can order stuff that's not listed in their catalog.

 

[SlowCo]

This would be the perfect motor to replace the stinky, noisy, polluting two stroke engine: https://endless-sphere.com/forums/viewtopic.php?f=12&t=99606
Go all electric with that motor-gearbox combo and you can choose the ideal motor rpm and speed of the trike for every situation.
http://www.eastgem.net/gb200-kit.html

 

[DmitryK]

Thanks for all the replies and referrals.

The electric motor is supposed to get the trike up to speeds of NO MORE that 20 mhp from standstill or uphill and then the gas motor takes over on the straightaways.

The "All Axle Hub" is for all axles with whatever spacers maybe needed I asssume? Good news is that the 17"x1.4", 36 spoke rim is available; there are no 32 spoke rims out there in the size I need. Is my fork leg inside spacing of 4.5" going to be an issue with fitment of a lets say 3000W hub motor? What axle diameters and lengths do those electric hubs come with?

Braking with the front hub would be ideal; eliminates the need for disk brakes. Where do I go shopping for one of those 3000W DD hub motors?

 

[ZeroEm]

vintage trike

Starting to really like this build. Set of peddles would be great and call it a bike. 8)

 

[goatman]

good news, grin has the crystalite 3525 with a 12mm thru axle but its for the rear tire, id send them an email to see if you can get a different side cover and/or maybe machine the axle to 4.5 inches? edit* you already have a 12mm axle

https://ebikes.ca/shop/electric-bicycle-parts/motors/m3525r-ta.html

 

[DmitryK]

I called ebikes today regarding their thru axle hubs; they're 2000W maximum. Do you think 2000W hub motor will pull 400 lbs 250lbs trike + adult + 6yo + 3 yo) uphill or have decent acceleration at a stop sign? I ran their motor simulator for the crystalite 3525 got these results:

Performance Syst A
Acceleration -0.00 kph/s
Consumption 71.1 Wh/km
Range 23 km
Overheat In 20 minutes
Final Temp 183 °C

So I'm considering adapting a rear wheel hub (3000W or higher) in the front and am running into all kinds of fitment issues with my 4.5" fork clearance. Here's a drawing of an MXSUS 3000 3K-Turbo. If I'm reading it right I need 138.5mm clearance between the fork legs for it. I have only 114.3mm. So some 24mm short and need to machine them down or get different forks.

 

[markz]

Hub motors come in rear, front and fat. You need a front hub for 110mm dropouts.

 

[goatman]

im not sure what you entered in the simulator. i got different results

the mxus v3 3000 watt is like a crystalite 3540, i put 3500watts through my 3540 no problem

the crystalite 3525 (clyte 3525) thru axle i would put 3500 watts thru it but after looking at the schematics you cant shave metal off the motor axle and keep the wheel centered in the fork unless you replaced the disc brake cover plate with another freewheel cover plate so you have 2 freewheel side cover plates and no disc brake then you might have to "machine " the motor axle to move the torque arm OR get a wider fork

https://ebikes.ca/amfile/file/download/file/73/product/1024/


machining down the mxus, its not a thru axle so then you need to machine the fork also or how about different crowns

 

[SlowCo]

So I'm considering adapting a rear wheel hub (3000W or higher) in the front and am running into all kinds of fitment issues with my 4.5" fork clearance.

Why would you want all the trouble of trying to mount a front hub motor in a motorcycle fork when it's clearly a much better idea to add a mid drive motor to the rear? Or even completely replace the ICE engine for an electric motor so you don't have the noise and smell of the stinker 2 stroke! Why are you so fixated on adding a front hub? It's a really dumb idea...
When going uphill most of the weight will be on the rear so the traction of the front wheel will be limited.

 

[John in CR]

+1 If you really want an improvement in every possible way, unbolt that stinky, noisy, under-powered ICE motor that spits out more pollution than a car engine, and replace it with an electric motor. I assure you that once you experience it, you'll start figuring out cool ways to convert your mopeds over to electric too. You don't need anything near the cost and weight of a 6-8kw hubmotor, since you obviously don't want to go fast with that vehicle, and unless you have some crazy steep hills to climb, you don't need the weight or efficiency loss of that electric motor with a gearbox. Don't waste time with lead batteries, since you want decent range based on the size of that gas tank.

 

[ARod1993]

Hi guys. I have a vintage trike. It's powered by a 49cc t2 motor that powers the differential on rear axle. Right now the bike weighs at least 200 lbs and climbing the more improvements I make. It's geared super low for high torque but low high end speed. My goal is to find a happy medium of hill cllimbing and decent top end. I can get good top end with a big bore kit and higher hearing. But I need an electric hub front wheel conversion for MOSTLY take offs and hill climbing. The gas motor can power the trike on straight aways and through minor hills.

All my rims are 17x1.4. I think a 6000-8000W electric motor is a good option in my case, but I'm open to suggestions. Right now my front end consist of KX65 forks with modified triples, CR85 rim with disk brake. The goal is to lace the hub motor into an 17x1.4 rim. I do need the front disk brake function, so I'll probably be adapting a rear hub motor on my front wheel. I'm a noob in the ebike scene so help along with my project. I'm attaching a photo of my trike.

Here's a few questions right off the bat:
- What capacity motor is suitable for my machine
- Will the right size spokes be available
- Where to buy parts

Webp.net-resizeimage (1).jpg

Honestly, if you want to push 8-10kW you'd likely be best off putting together a mid-drive using something like the Neumotor 8057; it's optimized for about the same rpm range as your engine is (assuming you put 80-100V lithium on it, which you really should if you can afford to), and so you could probably run it straight through your existing gearing and differential. You're gonna get a hell of a lot more usable power and torque out of that than trying to run a front hub that's gonna have questionable traction going uphill anyway because of weight distribution.

The other big thing to remember is that ICE vehicles wind up needing a lot more horsepower per unit of torque you actually get on takeoff; I have a 50cc Tomos moped that I got because the pandemic cut bus service to my job, and I basically have to peg the throttle on takeoff to get any torque. For the 8057-100 motor; the torque constant is about 0.1Nm/A, which means that 150ish phase amps gets you 15Nm at the motor. Gear that down 8:1 or 10:1 and you're getting more rear wheel torque than a Smart Fortwo on an vehicle that weighs about 8x less, and all that torque is available at 0rpm; it's an amazing adrenaline rush (and will also unceremoniously dump you on your ass if you don't respect it, but that's part of what makes it fun )