Budget Lightweight Friction Drive

[hjoore]

Hi Ebike guru's and Ebike-curious readers!

I am new to Ebike building, but am glad to tell you that I just made my own little friction drive and had a great first test ride!

Heres the setup:
- Motor: Turnigy 6354
- ESC: HobbyKing SS 190/200
- Battery: 1 X 5S 18.5V 8000mAh Zippy
- BEC: 3A BEC
- Turnigy Servo Tester, modded with twist throttle (soon, now just a potmeter)
- Wooden single sided frame (thinking green and budget), with a little rubber band to keep the motor off the wheel.

Weight: approx. 2 kg without LiPo, 3kg with LiPo, total bike weight: just 16 kg!, I can't really feel the difference when its deactivated.

I just did 13.5 km with an average of 37 km/h with varying amounts of pedaling, but the last 6 km full throttle with no pedaling!
The battery has used about 7200Ah, so thats 7.2*18.5 = 133Wh = 10 Wh/km!
This is equivalent to 300 km/l in gasoline! So basically 10 times cheaper than a scooter/moped per km.
The top speed at first was 42km/h, at the end 38 km/h, so it is pretty consistent.
The great thing is, the 18.5V limits the speed to 42km/h, but when you get to a hill, it will keep the speed at about 35km/h without pedaling,
it just increases the torque and thus the amps and doesn't slow down much.

http://www.youtube.com/watch?v=ef2XK1nHQEE

[youtube]ef2XK1nHQEE[/youtube]
My dad had the honors of turning the throttle the first time, I didn't need any adjusting, the pressure on the wheel was perfect and the release and lock motion is perfect too.

The only thing is the grip tape has worn out, I use the self-adhesive stuff you put on stairs, but I think the glue melts and it comes off.
I will try epoxying a belt-sander belt soon, hope that lasts longer.

What do you guys think of my effort? Can't wait to get an expert opinion on this.

Hans Joore
Aerospace Engineer at PAL-V, Netherlands

 

[spinningmagnets]

Onthaal aan eindeloos gebied! :: Welcome to ES!

Your drive is similar to Kepler and Adrians. If you scan through their threads, you will find the type of adhesive and sandpaper that has worked best for them. I believe the sandpaper is a cloth belt that is advertised as wet-dry, and is a very coarse 40-grit.

Do not be embarrassed about building with wood, it is a legitimate material. Bubba glued aluminum to plywood to add some strength in certain places.

Commuter Booster - <1kg Friction Drive (Adrian)
http://endless-sphere.com/forums/viewtopic.php?f=28&t=22187

Kepler eboost. The journey and evolution
http://endless-sphere.com/forums/viewtopic.php?f=28&t=25645

An Advanced Friction Drive System (Kepler, 30 pages)
http://endless-sphere.com/forums/viewtopic.php?t=16550

A list of several other friction drives
http://endless-sphere.com/forums/viewtopic.php?f=28&t=14403

Bubba bonding wood/aluminum
http://endless-sphere.com/forums/viewtopic.php?f=28&t=14130&start=15#p223969

wooden bicycles
http://endless-sphere.com/forums/viewtopic.php?f=1&t=10697

 

[adrian_sm]

Hans,

Looks great. I love seeing people get a system up and running so quickly and successfully.

Well done.

Adrian

 

[hjoore]

Thanks guys,

I got it working so quickly because I read some of your advice on this forum,
The wood was just a quick proof-of-concept scrap material, but thanks to the little box design it is still rigid enough.
I already have some Aircraft grade 6mm aluminum and a Topeak beamrack for the next proto,
or I could try the commuter booster concept with a small motor for my girlfriend.
I have 3 possible motors, started with the biggest one, but am sure going to try the 50-65 and the 30-40 motors with
smaller ESC power pack. The lighter the better, since the big one hardly gets warm at 40km/h, I suppose it can be done with the smaller 50-65 which should have the exact same speed and force according to my calculations.

Greetings, Hans

 

[adrian_sm]

The 50mm motors will work, but you can burn them on hills if you are not careful. That is why I am now focusing on ways to limit power to them. But maybe with your nice flat country you have an advantage.

- Adrian

 

[hjoore]

My project has been on pause for 2 weeks now cause I burned my big 63-54 motor after a crash...
Aparantly the drive was warped and the stator of the motor was running onto the tyre, while the rotor was trying to drive it!!
This caused so much heat some windings were destroyed. Its a shame cause its such a nice compact motor.
So its back to waiting for new stuff from Hong-Kong..

Anyway I had a great test ride with my friction drive through the forest, but due to my dark shades I couldn't see anything when I hit a dark spot in the forest and rode through a ditch! It does look very funny on video and it didnt hurt at all haha:

[youtube]q0vWJZm_H3s[/youtube]

It was a real rush going 45 km/h without effort where I normally only have the energy to go 33 km/h.
Soon with 63-74 200 Kv motor and no more over-center locking!! Thanks for the advice Adrian.
I'm going to try the 80A superbrain ESC with the current limiting I saw on your CB website, and also got the lipo's you advised.
I just need a 50A current limit so I can also use my 50-65 motor on another bike! I'm looking everywhere in hope of finding how to do it. I saw you mention a CB50?? is that your own creation throttle interface?

 

[Powdersummit]

Loving the video up until the crash. That sucks that your motor is fried, you could always rebuild and rewind for better torque. I was amazed at how fast you were able to go off road. I was wondering how much peddle assist you were using and what kind of slopes you were pulling, either way a person could cover a lot of ground with your set up. Keep up the good work we all love videos.

Carl

 

[adrian_sm]

Aparantly the drive was warped and the stator of the motor was running onto the tyre, while the rotor was trying to drive it!!

Oops. If it was this misaligned it was probably tearing up you rear tire to by trying to shear it sideways.

Soon with 63-74 200 Kv motor and no more over-center locking!! Thanks for the advice Adrian.
I'm going to try the 80A superbrain ESC with the current limiting I saw on your CB website, and also got the lipo's you advised.
I just need a 50A current limit so I can also use my 50-65 motor on another bike! I'm looking everywhere in hope of finding how to do it. I saw you mention a CB50?? is that your own creation throttle interface?

The CB50 refers to a Commuter Booster design for a 50mm diameter motor.

As for current limiting the only options I have currently up and running are a modified watt meter. Most fo the work was done by Jonas, but I tweaked a few things to suit me.

My WIP interface is still just that, a work in progress. So nothing I can share yet.

The other option is running with no current limit, and just go easy on the throttle. The ramp control helps, by limiting how quickly it tries to accelerate the motor, but it will not ease back on the throttle when you hit a hill for example. I have been happily running my 6274-200kv on 5s LiPo without any current limiting, and for the roads I ride, and my riding style it has been very reliable. No overheating issue for motor or ESC.

But for the little 5065 motor, I don't think it will survive long without some form of current limitting. It is too easy to overload the tiny motor, generate a lot of waste heat, then the motor has so little mass it heat up quickly.

But if you want piece of mind and insurance for the motor, we really need a current limiting solution. Of which there are a few in development on the forum. Just nothing plug'n'play yet. But rest assured I am working on it.

 

[hjoore]

In the video I would say I pedaled with medium power, going 45km/h instead of 33km/h at my max constant pedal power.
It has great potential, as Adrian can agree I think.

Haha yes the misaligned motor was trying to rip my tire in two, there is a nice line down the middle with one half smooth and the other rough! I can forgive the little 6354 motor for giving up on me for that..

Untill there is a simpel current limiting available, I just use my 6374 200kv with the ramp control.

I calculated that this puts out a whopping 50% more torque than the 6354 250kV motor!!
Theoretically it can accelerate from 0-30km/h in 6 seconds without assist. And pull me up 15% slopes! The torque is 6.8Nm on the motor, with 151 N force on the motor circumference, which is equivalent to 63 Nm wheel torque on my 28'' wheel.

I can't wait to test it, it just came in the mail at my parents.

I'm still looking for a nice twist throttle that would fit on my clustered steering bar, Adrian do you have any suggestion?

See I have the thumb and index trigger gearshift attached to the brake lever, and no room there for the big potmeter of a Magura twist throttle.

 

[bigkahuna]

Very cool, would like to build something like this some day. Any photos of the wooden mount and how it's attached to the bike?

 

[adrian_sm]

Only just got a chance to watch the video.

Damn, that looked quick for some tight tracks. I guess you have riden them before an know what is around each corner.

So the throttle you have.. is that just a linear pot strapped to your handle bars, with no spring return? That would scare the hell out of me. All my throttles have a spring return.

My preference for throttles for flat bars is a half wist throttle, without any of the LED crap. These tend to give the best clearance to shifters and the like. I also prefer to modify them to be left hand operated, so my right hand can shift gears and operate the front brake. Leaving my left hand to do the throttle duties. And if it clashes with the front derailuer shifters it is no big deal since I never shift them on my electric bikes. The main battle is getting it to fit with everything else on you handlebars.

 

[hjoore]

Yes I have nice close up pictures, I just gotta see how I can post them here...

Thanks for the response Adrian, that was what I was thinking, maybe a full twist throttle on the left with the potmeter stuff on the outside of the bar, so its still operating the same way. Then I can leave all the other stuff as is.
Plus it feels special with unique leftie throttle haha
I think I'll try that then. The no-spring-return is dangerous indeed, as you can see after the crash, it was still running at full throttle. Time for a safety update.

 

[bigkahuna]

You can host your photos here: http://imageshack.us/

 

[Fietsbel]

Hey Hjoore,

Nice to meet a fellow lagelander!
Definately make a simple 50-65 friction drive for your gf, she will love it! Though.. make it fool proof, so not too much volts, and a spring return throttle
Nice video through the woods, very nice speeds and crash

Groetjes!

 

[bose]

Wow! That video was truly awesome! That's about what I want my drive to manage, some trails in the woods. And at those speeds I think one can have great fun?

Great work!

 

[hjoore]

Hey guys,

That was one crazy ride! Never had so much fun/adrenaline during my routine forest ride! Too bad it burned afterwards, but...

I just finished my version 2.0 friction drive, (still have no name for it),
with a slide-on 370Wh battery container, and the swingarm construction which bolts on to a standard Topeak EX rack! (pictures on my facebook but not here yet)
Today had my first test ride, 33 km with 37 km/h average!! The batteries still had enough juice to go 35km total! I was amazed by the results, thats only 10.5Wh/km at such a high speed!
That is only 0.23 Eurocent / km!

Monday is my first of hopefully many commutes to work! hope the cops don't impound it soon...

To FietsBel: thanks a lot! I now have a nice hall throttle which works great, and a 80A esc for my gf bike, but do you think the little 50-65 can manage the power? my 63-74 already gets hot when accelerating a lot, I think she'll burn it out quickly, or maybe on 3S or 4S it won't...

Groeten

 

[Fietsbel]

Im using the 50-65 at 6s a123, so that would be 5s lipo, and im not burning it, just only power up from 20kmh to 37.

Using 4s I have tried, with good results, than you definately wont burn it. I ran it at around 12-15 amp full throttle, with slight pedaling around 30kph
Very efficient in that way!

 

[n2wheelies]

very cool, been doing this for a while now. i sell cnc stamped brackets to mount most motor sizes. i use the seatpost bolt as the hinge position, usually i have to flip the clamp 180 degrees to get a good angle. ive clocked just shy of 50 mph, limited by my 110 HV speed controller, cant afford a bigger one. i have the sam eissue with grip tape. thinking about producing sleeves to epoxy to the motor diameter....



enjoy!

 

[hjoore]

woow now thats what i'm talking about!! 8) 7kW is insane on a bicycle! I wonder how long your tires last?

I was also thinking of replacing the sanding belt epoxy method with some kind of sleeve, maybe a metal with knurled pattern, the un-even-ness of the sanding paper causes lots of wear on the tire.
I am now testing my ebike for reliability and wear on all parts by riding it to my work (33km) and back at least once a week, so far 300km+ with one motor, and 245km with a new tire, looks like it will last only 800km or so. That will then be the most costly item per mile/km.
Today tested a smaller 5065 motor on a mountainbike (drive+electronics+throttle weigh less than 1 kg), and managed 9.9Wh/km while going 36km/h average! Thats going to be a nice commuter setup (right Adrian?). The bigger 6374 motor only manages 11-12Wh/km at best on long rides so theres a trade off between power and range.

 

[adrian_sm]

7kW is insane for a friction drive, it just requires too much tire engagement, which will kill tires.

You also seem to be wearing out tires a hell of a lot quicker than me. Try limiting the amount that the drive engages with the tire. Or get rid of the grip tape all together. I did some tests recently and was still able to get good torque transfer without it. Just haven't had much time to get on the road with it.

Interesting difference in wh/km for the different motors. I have always found it hard to get direct comparisons due to different speed etc. But I now have my electronics interface able to display (& log) instantaneous wh/km stats, perform cruise control, limit power etc. So I should be able to get a huge amount of data as soon as I find some time to ride.

- Adrian

 

[bzhwindtalker]

I liked your video a lot, you were going quite fast trough those trails! good job and not going down at one point or another means that you are not riding hard enough, you did it right