Electric bike Build. Epic Power, need your help/input

[nechaus]

Hello,

So i have decided to make my own electric motorbike ( small 125cc mini frame), My aim is to be able to take it to a regular motorbike track and beat Petrol bikes in acceleration and have awesome fun with it.

I Have not yet Decided on the motor, or motors ill use, i wanted some input from you guys.

However
What I currently have,
x2hpm5000b golden motor brushless 8 inch motors, 5kw continuous rated.
Could use this as a dual motor setup, 22kg of motor weight, cost me another $900 for the exact same controller, so id have x2 200/400 amp kellys running dual hpm5000bs

Or
I was thinking
PMAC-DS (ME0913) $825 + shipping ( this way i would use my current 200/400 amp kelly controller ) 15 kg of motor
The Mars motor is rated for 12 kw continuous, 40 hp... Pretty friken awesome, but is it possible x2 hpms would run better than one of theses mars motors ?
The hpm looks slightly more efficient ?


If having 2 motors is going to be less performance, id rather just buy one of the mars motors, and use my existing controller. ( but almost feel limited with the controller)
I dont want to have to spend much more money as iv got stuff to make use of.

 

[Ratking]

Hello

I would take a step back and write down what you think is important with your new build. Write down what kind of power you want, battery capacity, design and power-train etc. The best approach would be to design every bit and part in a 3d program as Inventor. That way you can meet your goal without having to make too many design an mechanical errors.

I am in the same situation as you, I want to build an epic bike, but there is a load of variables that I need to get pinned down. So I take my time and get small drips of inspiration as I live and learn. Mostly from this wonderful site, maybe your build will be the final inspirational push I need to build the best build ever?

Good luck on your epic build, please try to make it pleasing to the eye as-well as functional.

 

[nechaus]

Well, I have ridden motorbikes,
Every single ebike i have made so far has not been up to par in power with petrol bikes.

Now i am at the stage where i want to take a big leap and just be satisfied already.


This is the frame Ill use for the build. what do you think?
Pocket rocket

 

[nechaus]

I have about 3.5 to 4 kw worth of lipo that i can use for this build, just need to take it off 2 other ebikes.
All 30 c cells, so 10 c should be close to 30/40 kw, the cells should run quite happy.. they may warm up just a bit
I am going to make a aluminum battery box that can bolt onto my frame.

Because there is so much room on this bike to mount batteries, motors, controllers ect..
I am going to make some custom cooling for my controller/controllers and hopefully motor/motors.
I have some big heat sinks sized for my new controller, im going to test out some 400 watt peltier plates and heatsink with a radiator and cooling pipes.
See what i can come up with, hopefully making some sweet cooling that is not to bulky.

 

[nechaus]

Hpm motor setup would run 100 - 200 amp each motor, x2 Controllers.
Mars Would run just one controller at full power, 200/400 amp
Same voltage and if i could make it the same gearing ect..
Based on that, Which setup would win in terms of speed, acceleration, efficiency?

Im not sure how well the hpms would run at 200 plus amps, But if it could take more than that, i could just run them at higher peak power to which i am fairly certain would beat the mars..
But I could end up with x2 burnt out hpms which would suck.

 

[Jeremy Harris]

A big challenge that I found when doing something similar with a small motorcycle conversion (but not going for ultimate power, just useful range) was finding room in the frame. I originally went with a big Mars motor, but it was heavy and took up far too much space in the frame, leaving little room for the batteries and controller. Some small motorcycle frames are really tight on space, I found.

My current plan to get the motor size down is to use two 80-100 motors connected to a common shaft, with this driving a layshaft that will drive the chain. It's early days, but it looks like coupling two motor shafts up like this allows for a small diameter motor with the capability to deliver a few kW of power. It's easier (at least in my Yamaha frame) to accommodate the extra length of the motors, as coupled together they are still only around 300mm (~12") wide, but are only about 80mm (just over 3") in diameter.

 

[gwhy!1]

A big challenge that I found when doing something similar with a small motorcycle conversion (but not going for ultimate power, just useful range) was finding room in the frame. I originally went with a big Mars motor, but it was heavy and took up far too much space in the frame, leaving little room for the batteries and controller. Some small motorcycle frames are really tight on space, I found.

My current plan to get the motor size down is to use two 80-100 motors connected to a common shaft, with this driving a layshaft that will drive the chain. It's early days, but it looks like coupling two motor shafts up like this allows for a small diameter motor with the capability to deliver a few kW of power. It's easier (at least in my Yamaha frame) to accommodate the extra length of the motors, as coupled together they are still only around 300mm (~12") wide, but are only about 80mm (just over 3") in diameter.

Coupling two of 'more' motors are the way to go with separate controllers so you dont have to deal with loads of current capability from just one controller ( works out a fair bit cheaper as well ). I have not done the common shaft option as this complicated things for my needs.

Hpm motor setup would run 100 - 200 amp each motor, x2 Controllers.
Mars Would run just one controller at full power, 200/400 amp
Same voltage and if i could make it the same gearing ect..
Based on that, Which setup would win in terms of speed, acceleration, efficiency?

Im not sure how well the hpms would run at 200 plus amps, But if it could take more than that, i could just run them at higher peak power to which i am fairly certain would beat the mars..
But I could end up with x2 burnt out hpms which would suck.

I setup a pitbike with just 1 6374 rc running at a 75A limit It was only geared for a top speed of around 22/25mph but it would out accelerate a 125cc (tuned) pitbike from the line up to around 18mph with ease and even though the top speed was only around 25mph it would hold its own on a short off road track against 125cc pitbikes, so if another motor was added the top speed could be geared for more like 40mph with the same ripping acceleration, just some food for thought.

 

[nechaus]

I would love to try an rc motor build.. been thinking about that for a long time, but im more inclined to use one on a surfboard or canoe. to cold for that now tho


But for now i cannot decide either 1 or 2 motors. Has pros and cons for each

 

[nechaus]

A big challenge that I found when doing something similar with a small motorcycle conversion (but not going for ultimate power, just useful range) was finding room in the frame. I originally went with a big Mars motor, but it was heavy and took up far too much space in the frame, leaving little room for the batteries and controller. Some small motorcycle frames are really tight on space, I found.

My current plan to get the motor size down is to use two 80-100 motors connected to a common shaft, with this driving a layshaft that will drive the chain. It's early days, but it looks like coupling two motor shafts up like this allows for a small diameter motor with the capability to deliver a few kW of power. It's easier (at least in my Yamaha frame) to accommodate the extra length of the motors, as coupled together they are still only around 300mm (~12") wide, but are only about 80mm (just over 3") in diameter.

Do you have any videos of your build jeremy?
or thread open so i can take a peak

Was the frame you used similar to mine?

 

[Jeremy Harris]

Do you have any videos of your build jeremy?
or thread open so i can take a peak

Was the frame you used similar to mine?

The part-finished build thread is here: http://endless-sphere.com/forums/viewtopic.php?f=10&t=3779&hilit=RD50 but I never got around to posting pictures of the nearly finished bike before I took it apart again, mainly as I was unhappy with the way I had to hang the batteries all over the place, making it plain ugly. I even thought of selling it for a while, but just put it on the back burner. Glad I didn't sell it, as it happens, as I now have a way forward to fit everything inside the frame neatly, I think. Your frame looks better than mine, being open at the bottom, but you may need to add something structural in there to tie top and bottom together at the back, as unlike my old frame, the engine/transmission on yours may have been a structural member in the frame originally. I may be wrong, as it's hard to tell from that photo whether the engine/trans did used to bolt to the top and bottom of that rear "C" section.

 

[nechaus]

Yeah I think your spot on actually,
Id love to weld directly on this frame, its nice and clean to.. but im not sure if that will weaken it.
If i cant do that, im going to bolt on extra support for where the original motor would support the frame, I can use this also for a battery bay.


Today i took apart some of my Hpm5000b motor. On the rear of the motor where the fan is, the fan just blows air over the shell of the motor, No airflow within the motor which sucks i think.
Iv got a bit of a crazy idea of taking the motor apart and drilling holes in the motor for a separate fan that will blow forced air through the motor with a particle filter on the inlet of the fan.

Or i just drill a crazy amount of holes and hope i create better airflow with the stock fan and hope nothing gets sucked in or jammed.

Im sure if i could ventilate it like i do my hub motors, i could really get some more continuous power out of the motor.
Im dropping it back to 20s also as its just a pain to fit so many batteries

 

[John in CR]

If you really want to embarrass them, put a big ass scooter hubbie in the rear wheel, and then install a little RC motor as a helper motor made to look like like it's the primary drive.

 

[nechaus]

Well I made the Mini Motorbike,
put on the bigger kelly controller, @ 20s i see it sucks a max so far of about 170 200 battery amps

Had 1.2 kw of battery, it was not enough, so i changed it to 24ah 20s.. getting just over 1.5/6kw b4 my controller cuts out


It does power wheelies from like 0 to 30kmh.. anything over 30 kmh the controller cuts the power
Its set back on torque this new controller, 100% battery current and 70% motor current
Throttle range is 1.1 ------ 3.9 volts

Maybe ill need to try the "speed" setting again, to stop the thing cutting out when i do WOT from 30 kmh to 40 kmh.
After 40kmh I can do WOT it just accelerates hard to 75ish kmh

The controller is hardly heating up at all feels rather bullet proof with the extra heatsink



But overall so far.. if compared to the same size petrol bike/rider, this thing will eat a 125cc bike for breakfast lunch and dinner
once i stop this controller from cutting out from 0 kmh and use WOT to full speed, im sure it could take on a 250cc bike with the same size rider, but power wheelie.


It is a joy to ride off road, the dual suspension sucks up all the bumps, at the end of a ride of hard use, lots of power wheelies ect.. the motor is actually pretty damm warm after.
When ever i ride the thing on the grass, its way to hard to not let the back wheel spin.. gotta take it slower or get some proper off road tyres

Iv spent about $2500 on this project... total amount in parts
Pretty damm happy with that figure for the power that im getting from it.