Motor Choice Advice for Motorcycle Class eBike

Hey all, I've finished my regular eBike, a Q100c in a Trek FX 2 with an S12S controller, and I would like to build a more "practical" vehicle for getting around my area. My excuse to build something so powerful would be that where I live currently, Prescott AZ, accessing towns just 5 miles away requires taking the interstate, and I need a better way to get around. Also, this would be a whole lotta fun . I've been doing research and modelling for a while, and I've come up with a cafe-racer style electric motorbike using 5 series-modified Nissan Leaf modules for power at 72V. I'm wondering about a motor. I've specced and modelled in a QS205 right now, but I was wondering if there was a cheaper alternative to power a vehicle such as this up to 50-60 mph. Though it's nowhere near complete, I have come up with this model which shows the general idea for the vehicle.:
https://imgur.com/a/XvAulOB
https://imgur.com/a/9KnPpDf
https://imgur.com/a/p9vObPo
https://imgur.com/a/xUA6fgK
https://imgur.com/a/iHdY7oV

It's built from a step-through bicycle with riser bars, with a dual crown upside down fork replacing the stock rigid fork. The bars are tilted sideways and clamped on for a swept-back feel. The bottom bracket serves as the pivot point for the rear suspension, while a steel bar is welded across the top for strength and rigidity. I've modelled in 17 inch dirtbike rims and some cheap rear shocks, along with the 5 batteries. Ideas for what kind of electrical system to run (72 or 12 or 6 volts) are also welcome. I'd be building this after the summer, when I'll have enough money to make it happen.

I would seriously consider using an old actual motorbike rather than modifying a bicycle.

Something like a 70's/80's Honda CB125 would be ideal.Or other Jap bike of that era, maybe a larger frame if needed. This way it already has the frame,brakes,suspension that are rated for the speed and all the lights etc. It would make getting it licenced way simpler and there are usually lots of them around and it doesn't matter if its not running.

You would just need to remove the engine, install a mid drive motor, controller and battery and use a 12V (or 6V depending on the year) DC/DC converter to power the original electrics.

One option are these guys http://www.cyclone-tw.com/motor.html have some options under 300USD around the 6KW mark for mid drive brushless motor. They have a 72v 120A controller for $165 too.

You would then just need to design the mountings for the motor and battery, and not have to worry about swing arm geometry etc.

I built what you are looking to build - but I used a Tomos Streetmate frame. It is a small motorcycle/moped. I used a QS205 motor with 72v 18650 battery. Goes 50mph. Registers as a moped. Looks awesome, handles the roads well. Let me know if you want more details. Happy to share. https://photos.app.goo.gl/NjwBrxJcjhjHZzYdA

+1 on using a motorcycle chassis. On my area we can easily register offroad bikes (and mopeds are unconmon) so that's what I'd start with.
Steel frames are easily modified as well.

Again ditch the "bicycle" idea, and stick to the "motorcycle" frames. QS motors are quite powerful hubs, you could even go mid drive motor and not have to deal with lacing a motorcycle wheel into a hub. Just take the old motor out, and place in your electric motor and start fabricating. I had bought a cheap used welder a year or so ago, for $100usd and just laid my first bead yesterday, some 6013 rod. The chinese welders work too, but go with arc/stick welders because all you need is the machine, rods, and protecting equipment whereas mig costs you a lot more, and you need to have it all setup just right and if any one thing is off well it wont work. On youtube, a welder named Chucke2000 has bought some of the chinese specials for dirt cheap and they aren't bad for the backyard hobbyist.

So say I get a pretty non-runner, like a 1960 Triumph Bonneville. It comes with 200 mm drum brakes front and rear. I would still like to do a hub motor, mostly for simplicity's sake, and since I have very limited access to fabrication equipment, given that I live on a university campus. Would just keeping the front drum brake and using regenerative braking in the rear give me enough stopping power, or would I have to install a disc somewhere? Also, what motors are available which would be able to sustain a speed between 50 and 60 miles per hour in a wheel around 24 inches in diameter? Going through what's built into the motor simulator on ebikes.ca, kv seems to be the issue, which is no surprise really. My understanding is that a QS205 can be had for somewhere in the $300 range. Are there any others worth looking at, assuming a hub motor for the moment?
WRT to your bike, changeissimple, what motor winding did you get? What's your braking system like? Was it easy to register?
Thanks.

Don't ruin a classic. Plenty of 80-90s stuff better suited and cheaper.
You need a friction brake of some sort, this is a 350lb vehicle not a bicycle and legally must have brakes.

Couldn't agree more, for highway ride, you want a real motorcycle. If the cost is a problem, look into scooters. Yeah, I know, you look gay. But they ride great, and are way more comfortable than a crotch rocket or a v twin type bike. I priced an e motorcycle, and a good car came up cheaper.

Easy to find those scooters in Phoenix or Tucson, since old farts also ride em, then die. Pay about $2000 max for em, and easily hit 90 mph. https://tucson.craigslist.org/mcy/d/tucson-2003-suzuki-burgman-an400/6797817337.html


Mine btw, costs about 12 cents a mile. All my ebikes have cost at least 25 cents a mile. The fast ones cost a buck a mile, or more.


Once you have one, DO NOT MISS a ride up the 191. From Morenci to Alpine, its the BEST MOTORCYCLE RIDE IN THE WORLD. Oak creek canyon of course too, but that road will be jammed with traffic.

Thanks everybody for the advice and the help, I really appreciate it. I definitely wouldn’t want to ruin any classic, but this one is just a rolling chassis that came out of a barn fire, no engine or anything. It may or may not still be up when I get back from the summer. In any case, a huge point of pride for me would be being able to say that I built it myself. So regardless of frame choice, I would definitely have to fab disc brake mounts if it didn’t have them in rear, right? Would I have to get a motor with motorcycle disc mounts, or are there discs that would be adequate that mount to a standard mtb 6 bolt mounting? Wrt to front brakes, should whatever comes stock on the vehicle be fine? With the size of battery I’ve been thinking of (72 volts, 30-40 Ah to start), the bike should weigh less than stock, by my estimate. Do old drum brakes stop well with new pads, or should I upgrade to discs? Mind, it’s quite possible I’ll get something that has discs to begin with, but just in case, how are drums? The only bikes I’ve ever ridden have been pretty new.

Why run a hub drive when you already have a chassis designed to handle the power through a chain? Just get a QS3000 mid drive motor and make mounts. Solves the brake problems.

If you got money and time, do it just for the fun of the project. But if you just want to get to town, buy a 250 or larger motorcycle for now, and put the e moto on the back burner till you have a ton of cash. You'll spend 5 thou on the battery alone bro. Sell that frame to somebody who will restore it.


Is there a dirt route to town? A standard big hub motor in a good MTB, like 48v and 2000w, will make a dirt ride to town a blast. That kind of bike, 30 mph, able to just about climb a wall, gets you into small motorcycle type ride a LOT cheaper than building an electric highway bike.

Lastly, what interstate in prescott? I see highway, but not interstate. I understand that state highway often has sucky shoulder, and can be suicide to ride on with bicycles. Interstate has great shoulder, but is often illegal for bikes or mopeds. Both the 69 and the 89 appear to have a decent shoulder for bikes on google earth. If the shoulder is real rough, a good full suspension MTB will eat it up like cake. Build a fast e bike before you go to a freeway motorcycle. It will teach you how much it costs to run a fast electric motor.

I live on a highway, and the frontage made a great bike route. But for most of my travel, I much prefer going 65mph on the freeway with my scooter. Its just soooo practical and cheap, compared to my cars, or my e bikes. The ebike to the grocery is fine, but a fun blast on the scoot to there is better.

Regarding brakes. I rode on and off road motorcycles with drum brakes 100+ mph in the seventies. Just bring yours to spec and they should suffice for 50 mph IMO.

Do a mid drive conversion on the Bonnie. Don't listen to the naysayers, it will be a sweet ride.

Cyclone 18kw middrive with 72v 150A controller.
Keep the original wheels and brakes, may have to replace the rear sprocket for a larger one.
Run a 72-12v DC-DC converter for the stock electrics, lights, horn, etc.
Convert all the lights to 12v LEDs.
Modify the fuel tank to house the controller and other electronics.
Design a battery mount/enclosure that fits with the original style of the bike.

That should easily cruise at 50-60mph.

I dont know about anyone else, but I prefer to have my lights on a different battery.

So by using a bunch of cycling calculators, which I know won't be super accurate for my application, I found that I should need to get 4000-6000 watts continuous out of whatever motor I use to maintain my desired speed. Can anyone confirm or deny that?

WRT the interstate comment, it's quite possible I misunderstood, since I'm new to the states and am not sure how highways are classified. I just took somebody's word for it when they told me that highway 89 is an interstate. When I carpool with someone to Prescott Valley, I notice that the shoulder is paved, but covered in gravel and debris. I have seen a roadie there once, but I didn't envy him, since he had to ride within a few feet of the lane to keep from getting caught up in the debris.

I was looking around for motors and came across Goldenmotor's 3kw and 5kw motors, among others. Does anybody have any experience with these, or know anything about them? They looked like a good performance to cost ratio, if they perform as advertised. I was also looking at Hobbyking motors, but they only specify max current. Is this maximum continuous or peak? If it is maximum continuous, RC motors seem like a great choice for performance to weight ratios. If it is a peak rating, does anybody know how I could find out the continuous rating (or something close to it) from the specs available there, namely size, mass, and resistance? If I were to use RC motors, would eRPM be a problem? They might be spinning upwards of 15,000 RPM, and I don't know if most controllers at that power level can handle that. I'd also be worried about drivetrain solutions at that kind of speed. I've looked at cyclone's website, and it seems a bit of a nightmare to navigate. Is there a page for specs and the like for each motor they have for sale that I'm missing, or do I have to find that information elsewhere?

I had originally gone with a hub drive simply as a holdover from a previous sportbike-style design based off of the Elasticycle as seen in The Incredibles 2, as silly as that sounds. It shares the same triple crown, upside down fork, and motor wheel as the model I posted earlier, and was the original end goal, with the cafe racer simply being a stepping stone towards it. I realize now that that is probably pretty impractical, and even if I were to build it, it would be pretty far into the future, and I wouldn't want to tear down this project to do it.

Thanks again for all the advice, every post here brings this project closer to reality.

Edit: The information I am looking for for the cyclone motors would ideally be something like a performance curve, or a range of optimal revs. Also, are they sensored or sensorless? With my Q100 I have major desynchronization issues when running sensorless, and I don't know if this would carry over to something much larger or not.

Those golden motors are beasts. They easily put out their quoted rated power.

AviatorTrainman said:

Also, what motors are available which would be able to sustain a speed between 50 and 60 miles per hour in a wheel around 24 inches in diameter? Going through what's built into the motor simulator on ebikes.ca, kv seems to be the issue, which is no surprise really.

Click to expand...

FWIW, if a hubmotor isn't fast enough at a given wheel diameter, you can throw more voltage at it to fix that.