Return of the 3D Printed Friction Drive

Good day to you all,

As some of you might be aware sometime last year I released the files for a 3D printed friction drive. As time passed however I was getting increasingly disappointed by the performance of my (way too high KV) motor.

Roughly five weeks ago I decided to resume development and do it properly this time, by purchasing a 59mm SK3 motor (168 kv) and a 6S (2x 3S) LiFePo4 8400 mAh battery. New speeds and new motor weights bring new challenges so I hereby present you with the files for the beefy mount I've been using in the past three weeks.



The orange part as seen in the above screenshot is an adjustable limiter to allow you to fine tune the pivot angle. The other end is covered by a printed filter, to keep road debris from entering the motor.

The mount is held onto the 32.5mm frame tube with a pipe clamp which slides through the printed part. I'll look into taking a proper real life picture later today.

As before, the source files can be downloaded here. I've provided both STL and STP files.

Motor heat has been no issue with this setup, pushing me along at an (to me) awesome 30 km/hr. I do use grip tape for the motor as the roads tend to be wet quite often in this period.

Why share? Why not? This forum has taught me everything I wanted to know about bike propulsion systems.

Impressive! Glad to see a friction drive. It would be interesting if you could upload a couple of photos of it on the bike as well

Gryphe said:

Good day to you all,

Why share? Why not? This forum has taught me everything I wanted to know about bike propulsion systems.

Click to expand...

UR Awesome! Thanks for sharing!

Thanks for sharing !

How do you balance the motor weight ? Do you use any kind of spring ? I noticed this on other friction drives.

Good morning,

I'll get a set of pictures later today.



The above screenshot demonstrates the limiting system, which creates a 20 degrees angle for the arm to move in. When releasing the throttle I slow down, rather then completely stop the motor. (I use an Arduino for the motor control.)

So far it kept things from breaking. :wink:

As promised, some real life pictures. The bike's been quite dirty with all the construction work going on everywhere, so sorry about that.

A colleague of mine has expressed interest in letting me build a similar system for him. Obviously he wants me to do it for a somewhat cheaper price, so I designed a mount for the 50mm SK3 5065 236kv motor. I've updated the source files as mentioned in my first post to include the two new models. (Motor mount + motor filter)

The system will be running off a 4S battery, keeping the speed within a legal range.



I apologize in advance if I'm breaking rules by replying to my own post but seeing as it's a different subject I saw no harm in doing so.

Gryphe said:

A colleague of mine has expressed interest in letting me build a similar system for him. Obviously he wants me to do it for a somewhat cheaper price, so I designed a mount for the 50mm SK3 5065 236kv motor. I've updated the source files as mentioned in my first post to include the two new models. (Motor mount + motor filter)

The system will be running off a 4S battery, keeping the speed within a legal range.



I apologize in advance if I'm breaking rules by replying to my own post but seeing as it's a different subject I saw no harm in doing so.

Click to expand...

Great work! I love your posts.

I will attempt to follow your footsteps.

I am a 76 year old noobe when it comes to electric motor powered bikes (Hartley Davidson Motorcycles have no motors). However, I have built several engine powered bikes.

This friction drive recumbent trike was built about 6 years ago and it went 29 mph on a 1.5 hp 4 stroke 31cc Honda. Note the universal ball joint for steering. I can aim the rear view mirror anywhere as I steer with my feet.



I love the idea of using the outrunner case to drive the wheel using an over the center pivot lock.

Help and advice much appreciated.

My starting point is having 80 Sony 18650 cells 2200 Ah.

Questions: Should I wire the cells for 24, 36, or 48 volts?
Maximum top speed is not a problem.
Recommendation for Outrunner motor and esc?

Gryphe said:

A colleague of mine has expressed interest in letting me build a similar system for him. Obviously he wants me to do it for a somewhat cheaper price, so I designed a mount for the 50mm SK3 5065 236kv motor. I've updated the source files as mentioned in my first post to include the two new models. (Motor mount + motor filter)

The system will be running off a 4S battery, keeping the speed within a legal range.



I apologize in advance if I'm breaking rules by replying to my own post but seeing as it's a different subject I saw no harm in doing so.

Click to expand...

Would this be effective for low speed/high torque assist? How small can the battery be and what would be the total weight with a small battery that would provide 2ah of assist?

Do you have a complete parts list?

The 235kv motor should still you provide you with plenty of torque. I've tested this configuration with my old 4S Lifepo4 8.2 Ah battery and a 100A car ESC from HK. This should give you a speed of 25 km / hr and a (pedal-assisted) range of 18 kilometres. Roughly 16 miles / hour with a 11 mile range.

Besides the two printed parts all you need is a pipe clamp no higher then 12 mm and a M8 bolt to attach the mount to the clamp. You'll also need 4x15mm M4 bolts to attach the motor. Make sure to lubricate the hinge with teflon spray. It's awesome stuff.

I apologize for all the metric stuff but you have to admit, it's a lot less complicated. :wink:

I really think the whole idea of a 3d printed friction drive is very cool but I wonder how well the plastic will hold up over time with the high heat of an outrunner motor. You wouldn't want a high power outrunner flying off a mount. I've also always thought my motor has held up for a long time because my aluminum mount acts like a heat sink.

Hence me having started trying it last year. As long as you're not trying to push your motor to its limits heat really isn't an issue.

The temperate climate might be a great help in this regard but seeing as I'm printing these prototypes with a somewhat heat-proof type of plastic (needs at least 80C to start deforming) and my current setups never even reach ~40C I'm not too worried. That and I get the feeling the cooler tire rubbing against the can may aid with dispersing the heat, but that's just a non-proven theory of mine.

That and I use a metric buttload of plastic for these parts. They're almost solid pieces. A hammer doesn't put a dent in them (I seriously tried) so at least the strength isn't an issue.