Commuter Booster - <1kg Friction Drive

Adrian... Vary nice drives, Almost makes we wish I had seat tube :wink: Great pix as usual..

Kepler used the word ELEGANT in a post .. It fits in yours and his work...LIke fine jewlry.. Whoa!! now don't be raising the price :lol: Bill
 
Thanks Bill for the very kind words.

Hmmm, I was just looking at the pics of the bent you have your friction drive on. Is there anything on the back of the seat near the seat stays that you can bolt something to? I am picturing my CB mounted to the back of your seat. Looks like there is enough room. :) I am sure it could be done.

- Adrian
 
Bicycle handlebar stems can be found with a cylindrical center section. They come in a variety of length and angles, and also there are adjustable-angle units for under $30. Such a stem might be helpful in adapting your drive to recumbents or other non-conventional frames...

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I got everything put together tonight, and gave it power for the first time!

However, as with all new things, there are some issues, and I was hoping for some clarification. I have the spring set to keep the motor off the tire, and assume the torque of the motor will overcome the spring and engage the tire, is this correct? I ask because my motor is not giving good, constant contact with my tire. Rather, upon a hard start it will bounce and contact the tire, but once its up to speed, it drops back down.

Additionally the top speed seems low. I may need to play around with my speed controller.
 

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That is so cool. Great to see it coming to life.

The spring is actually there to help lift the motor. But with the location of your pivot point being almost exactly above the motor, the spring doesn't need to contribute anything, so could be very neutral in force at that position. If you have the spring pulling the motor away from the tyre, yes you may have trouble with it picking up the tyre. Oh, it also won't ride up the tyre unless the tyre has load on it, so if you are just testing it with the wheel off the ground, take it out on the road to test it properly.

Top speed should be a bit over 40kph on the flat with 5s LiPo battery. What battery are you using?

Again, great work putting it together. It is so good to see others pick this up and have a go.

Adrian
 
New cruise control.

The description/source code of the cruise controll is now available at the german pedelec-forum:
http://www.pedelecforum.de/forum/showthread.php?8137-Projekt-Tempomat-Bitte-um-Hilfe-bei-der-Elektronik/page2

Unfortunately in German language.

The Board consists of very few parts - really no problem

http://www.youtube.com/watch?v=mXOBU7IQFW8
 
Update: Springs !!!

My spring order finally arrived. This was the final part I was waiting on.
 
Now I get bored to wait to winter end and putning the assisat on bike to test the current limit in real.
It seems work seting max amp at 45 give peak at 55-60A and not 100-110A as before .
Running at 6S given peak 1100-1200Wp so it seems to work good.
Was litel cold only -10C wene out hope it get warmer soon.
Now I have to build a bigger batteribox with room for the wattmeter.
The down side is it has less power now :D
//Jonas
Edit !
Now i have a batteri box for 2//6S 4.5AH + wattmetterbat_box.JPG
 
Great to hear you are on the bike. -10C :shock: you are braver than me. :D

Good to hear it seems to be working properly. I managed to break my one and only watt-meter, and hobbyking are out of stock at the moment. So I haven't been able to help out with testing. Where else can we buy these from.

What batteries are you using. I was really happy with the large topeak aero wedge bags, for a quick release battery storage option. Big enough to fit 4 5s5Ah LiPo. But doubt you could get as many 6s batteries in.

Yeah it is hard to accept a lower power, once you know it is possible to have more from your setup. On my hub motor bike, I have a speed switch which drop the power down from a 70V setup to similar to a 48V power levels. I initially thought I would use this a lot to keep speeds down, and get a longer range..... but I only use it as a limp home setting now. :lol:

But for the friction drive, I really need it to protect the smaller 5065 motors. They just don't have the thermal mass/size to reject the waste heat at high power, low speed scenarios.
 
Busy weekend, so didn't get a lot done on the bike. Did manage to finish building the deck & steps down to the backyard. Also got half way through building a bed for my youngest, now that he is ready to get out of the cot.

As for the bike..... I ordered a few Watt Meters from epbuddy. So I should be able to get back on the electronics side of the development soon.
Also managed to modify one of the stock springs into the form I need, with out too much trouble, and this will be much easier and more repeatable so will make my life a lot easier when I make a batch of the drives.

How come in a whole weekend, I can only manage to get 30 mins to myself?
fr_666_size400.jpg
 
How come in a whole weekend, I can only manage to get 30 mins to myself?
Click to expand...

Don't your wife and kids realize that you are making E-bike HISTORY!??

"Oooooh!...mister big-shot 'genius'...you think you're gonna be some kind-of physicist someday?...you think you could maybe take out the trash, or put down the toilet seat once in a while?...you better apply for that job at the patent office, or you'll be sleeping on the couch!"
-Mileva Einstein (his ex-wife)

hm_but_story_roll.gif
 
:lol: Funny.

Update: Brain Box
Managed to water proof my little brain box that contains the ESC, modded servo-tester, and ramp rate adjuster. So I don't have to worry about weather. This will allow me to do a lot more testing, including more specifically in the wet.

Update: Robustness
Road it in to work again today. I was pretty tough on it today, using it the drive to accelerate from lower speeds etc, and managed to cook the windings of my 6374 motor.
I will have to do the post-mortem before I know for sure what caused the failure. As my modification to this specific motor to move the motor shaft, means that the motor could creep axially in some scenarios. Maybe this happened and it was rubbing on a swing arm. Or maybe I just bogged it down too much, which highlights the need for power limiting.

So what this has taught me is that I won't be making a batch of these and selling them to people, until I know what was wrong. I don't want to waste peoples time and money blowing up motors because of something stupid I have done, or that I don't have sufficient safety measures in place to let the drive protect itself.

It has also got me thinking about motor alternatives. Motor efficiency, the ability to reject waste heat, and thermal limits of windings are the major restrictions in performance/robustness for this type of drive. So spending a bit more on a motor with better efficiency may only increase the total package cost by 20%, but prove to be much more robust.
 
Hmmm. That's not right.

IMG_2449 (Small).jpg

Looks like a combination of things:
- a cir-clip had been removed that stops axial float of the can relative to the stator
- misalignment of the drive to encourage axial travel of the can, in the bad direction
- no spacer between the inner race of the bearing and motor,
- bearing pocket mad too deep, and
- insufficient clearance between motor and swing arm

Ooops.

Luckily most of those are really easy fixes.
 
You must have been pushing it really hard to kill the motor. I wouldnt have thought the contact would cause enough drag to over heat the motor. Current limiting is a must. Speed sensitive current limiting is even better (in my opinion :) )

The actual windings look OK in that photo. Is the motor actually dead?
 
Yep windings dead. Just can't see the insulation bubbles/blobs in the photo.

I didn't think I was going that hard on it to be honest. So it must have been scrapping pretty bad to cause this... Don't know.
It will at least give me a chance to pull apart the motor properly, and look at the quality without fear of damage.

Totally agree on the current limiting.

Better order another motor I guess.
 
I think the biggest issue is the motor shaft cir-clip grooves. If I want to slide the exist shaft along to get the second swing arm support, then I would need to push it almost all the way through so I can use the groove on the end of the shaft. This means that the axle sticks out a bit too far on the support swing arm side.

I really should just get the right tools so that I can go back to my single swing arm design. Then this problem goes away, and the motor shaft doesn't need to be moved/modified. Unless it is too long and gets in the way of the riders heal.

I really wanted to avoid any modifications to the motor, so that the end user can just buy the motor separately and assemble to the swing arm.

Hmmm this requires a little more thought.
 
Sorry for you motor Adrian :(
I hade some problem with bearing moved soo I fixed the axel to the support bearing at svingarm and have the this bearing fix in the svingarm but I have no support bearing on can.
Bad cooling is not good even with current limiting . I may try to mont a NTC in my motor to.
To reduce width you may can have the C6364 250Kv
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5144
I will try this later on wene I get some time at home.
/Jonas
 
Yep motor efficiency is what causes the heat. I haven't found a good source for data in these motors, and haven't dreamt up a way to measure it, but if I knew that for a few similar motors, I would be happy to switch for a better one. But for now I will focus on improvements that help any motor married up with the drive.
 
Yes ofcourse the efficiency causes the heat, what I meant was that to burn the motor it might have been at the edge already, scraping or not.

As for motor alternatives, there are not many as far as i know.

Possibly the the best outrunners (efficiency wise) are the large plettenbergs terminator/predator, and possibly the large hackers (not suitable for frictiondrives i think, large diameter and short stator)
Torcman has a 68mm stator, Axi has a 53mm stator, scorpion have some 55mm, hyperion has some 50mm stators. As for efficiency i am GUESSING
the hobbyking motors are in the lower range among the outrunners.
All in all hobbyking is alone with offering a large stator for almost no money.

If you could choose(cost excluded), what motorsize would you want, taken your experience from this build in account?
Obviously a low kv can be acieved with long stators as well.

I wish you the best of luck with your work, I think this could become a really good product.
 
Hmm, looking closer at the motor from hobbyking, the stator is 52x40mm. The labeling doesnt corrolate to the statorsize as with most other brands. (my bad)
In that case there are plenty of alternatives. Motor mass is a tad over 900g. Possible alternatives with similar mass: Axi 5345/18 is a 171kv motor. Hyperion 5045/18 is a 149kv motor. (both are more expensive than the turnigy)

Abit OT but worth some consideration:
I like to compare the kv of equal motors, if the kv is higher for no reason on one motor (equal turns, statorlength/width etc), one could suspect worse efficiency.
For example, putting weaker magnets into a motor, will increase the kv. Big gaps between stator/rotor will increase kv.
So whenever I see a huge outrunner with alot of turns and high kv, I am getting suspicious. Too bad hobbyking are really bad at posting additional motor data like noload current at stated voltage and internal resistance. Gets the impression of a jokesite in my book.
 
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