Another friction drive

[drifter]

Hi all, I thought I would have a go at building a friction drive after seeing Kepler's fantastic idea on The Inventors.
I decided to try out the cheapskates method, and only use the bare minimum of parts and use readily available bits as much as possible and also could be easily copied by the average handyman.
I have just finished putting it together and have not ridden it yet but the motor engages and disengages from the tire ok and drives the back wheel while I hold the brake on. I don't know if I can ride it without a throttle as I only have a servo tester. Maybe I will give it a try tomorrow.
Yes that is a $2.00 hinge and a piece of 25mm square aluminium , don't know how the motor will go being only mounted on one end but I will report back. This is a very quickly built prototype to test my ideas and I intend to modify or improve on anything that doesn't stand up to the pressure.
Robbo

 

[buzzfirst]

Oh yeah, simple simple and pretty straightforward. I was thinking of about the same thing once I saw the thread on this kind of drive. If the motor needs support on the other side all you would need is a longer hinge and another piece of aluminum! Cant wait to see how it works. Zipties rock!

 

[spinningmagnets]

Very clever! Drifter, what city you live in? If you made a cover and had the same performance as a more expensive drive, nobody would know. What motor, battery voltage and size, and ESC are you using? I HIGHLY recommend adding a support arm to the other end of the motor...for friction drives, here is "the list":

http://endless-sphere.com/forums/viewtopic.php?f=28&t=14403#p214997

edit: Also, what wheel diameter, and whats your top speed?

 

[etard]

very cool! It doesn't get more off the shelf than that.

Test it with that servo tester, it will be like cruise control, you could even just have an emergency pull cord zip tied to your top bar for easy access. :lol:

 

[def215]

is it even possible to call something too simple?...lol.

i like it. it looks like almost anyone can replicate it if they take a trip to the hardware store. thats what i like about builds like this. what motor, esc, and voltage are you running at?

 

[Kepler]

Now thats just too simple. You are going to put me out of business

Cant see any reason why that wont work. Can I suggest you experiment with some sort of rubber damper between the hinge plates. It should make the take up on the tire more progressive. With out some sort of damper, it will clunk on and off.

 

[drifter]

OK some answers, spinning magnets, etard, def 215 and Kepler, I live in Sawtell, near Coffs Harbour NSW.
Motor- turnigy 50-65
Speed controller- turnigy K force 100
Battery- turnigy 5000mah 30c 5cell
E-sky servo tester
26" wheel with 8 speed internal gear hub and drum brakes.

Dont know top speed , my bike speedo doesn't work.
Tried it out on the road today with some success. You are right Kepler, it needs some rubber to dampen the motion when the motor clunks into drive, sometimes it bounces badly ,especially at low speed, there is a bit of slop and flexing in the hinge also. I found that the bike needs to be traveling at approx 10-15 kph
before engaging the motor or else the motor is not happy, I have read of your similar experience, so you know what I mean. When the bike gets up to speed, it runs along very happily and goes up hills with assistance from me to keep the speed up. I am not interested in going fast but more interested in using the motor for assistance up hills so I think next I will try using a smaller diameter drum mounted directly on the motor shaft and drive the tire with that to lower the gearing.
Drifter

 

[drifter]

Could someone please suggest what size roller to use, I am 1949 vintage and need all the help I can get going up hills.
Drifter

 

[jdcburg]

I put up a table of rpms:speed for different size drive rollers. As you know lower speed = higher torque. It at the bottom of pg 2 of the "resources" section here: http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=7192&start=15 - jd

 

[drifter]

jdcburg, thanks, just what I wanted.
Robbo

 

[Hillhater]

Drifter, i dont know if you have seen this,? ..it may be useful.
http://www.staton-inc.com/store/catalog/Parts_for_Friction_Drive_Kits-31-1.html

 

[spinningmagnets]

Knurled and hardened rollers for $20, 1/2" shaft, (but only 1.00" dia and 1.25" diameters)

http://www.bikemotorparts.com/parts.html

 

[veloman]

You beat me to it. That is literally the same design I have in mind, once my HK order shows up. It's for my road bike, so I can flatten out he hills at 20-25mph, when visiting family/friends far away.


I love how real this is becoming. I have been dreaming about adding LIGHTWEIGHT power to my road bike forever. I'm really excited.

 

[drifter]

Ok there is a good selection of roller sizes there. My motor has an 8mm shaft so I would need to adapt to fit that
Robbo

 

[spinningmagnets]

There needs to be a bearing on each side of the roller to take all the stress of the roller pressing on the tire (also bumps, etc). Whether you use the motor shell as the roller, or connect a roller to the shaft of the motor...if you are putting a side load on the shaft, it will break soon. Here's a build that had that problem.

http://endless-sphere.com/forums/viewtopic.php?f=28&t=20901

Here's a pic of a gasoline motor kit. Notice the bearings in the sidewalls on both sides of the roller

 

[veloman]

I got my motor in today. I just took a pic of the cheapest, most lightweight ebike design. (somewhat copied from Robbo here). I went to upload the pic and my camera battery is dead, so will have to wait an hour or so.

I'm so excited.

Oh BTW, cheapest way to get 4 8mm bearings - ebay - skateboard wheels with abec 9 bearings. $10.

 

[amberwolf]

Here's a build that had that problem.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=20901

And another :
http://www.endless-sphere.com/forums/viewtopic.php?p=231011#p231011

Oh BTW, cheapest way to get 4 8mm bearings - ebay - skateboard wheels with abec 9 bearings. $10.

Unless you get your skateboards from freecycle. :lol:

 

[drifter]

Spinningmagnets, Thanks for that link, it looks like my simple drive is indeed too simple. I have ordered a roller, shaft and bearings from the supplier in your previous post.
I like the look of evtodd's build very much and might build a version of that.
Robbo

 

[spinningmagnets]

I'm glad I could help, but...I still don't know how I want to attach the motor shaft to the roller shaft. I'm sure there's several ways possible.

 

[drifter]

Going by evtodd's description, I imagined He used something like this

or this

 

[spinningmagnets]

Good drawing to clear-up some remaining questions. I am building a tiny table saw with 3" Dremel diamond wheels from Harbor freight ($13 each) to slot my shaft end. Its an experiment, so don't laugh too hard...

The thought of drilling tiny holes into steel makes my head hurt. So, to avoid that, I am hopeful that it will work to cut two flats on the 10mm motor shaft, and a central slot on the solid roller shaft. SDP-SI makes a sleeve to adapt the 10mm motor-shaft up to 1/2" to keep them concentric while mounting the motor.

Fingers crossed...

 

[Hillhater]

..... so don't laugh too hard...

The thought of drilling tiny holes into steel makes my head hurt....

Ha ! .. you brought back distant memories of having to drill 0.004" holes in test pieces !! .... tricky ! :lol:

The motor shaft is not hard ( dont know about the roller shaft though ? but unlikely to be very hard)...
......... so wouldn't a simple 3mm (1/8") roll pin thro' the two do the job ?

 

[EVTodd]

Good drawing to clear-up some remaining questions. I am building a tiny table saw with 3" Dremel diamond wheels from Harbor freight ($13 each) to slot my shaft end. Its an experiment, so don't laugh too hard...

You just made me cringe! Be VERY careful doing something like that. You have to make damn sure you have a really good way of holding that shaft. Man, I don't know. Be careful!

 

[spinningmagnets]

Man, I don't know. Be careful!

You can tell I am right-handed, because...I have so many scars on my left hand! Yes, I also have concerns which led me to build a tiny table saw from scratch with some type of jig to hold the shaft still, and the blades (spaced like a dado) are on an all-thread rod, so they can be moved left and right in tiny increments.

If I was still an un-scarred youngster, I would've slapped an angle-grinder with an abrasive wheel into a vise (safety guards removed, of course) and free-handed the shaft ("OW, thats HOT!"...[ZING]...sound of window shattering as shaft flies through the air...).

I am reminded of Lee Marvin in the movie "The Big Red One" [1st Infantry]..."relax kid, ya still got one testicle left!...thats why they gave you two of 'em"

 

[Hillhater]

Ya know ! ?... i am sure that shaft is soft enough to file in less time than it take to fab up your mini grinder !!
( but i know you enjoy these sideshow type distractions ! :wink: )
.........any yes, i would have used the bench grinder on those flats !