Full suspension mountain bike Friction Drive

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
Grantmac   10 kW

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Re: Full suspension mountain bike Friction Drive

Post by Grantmac » Aug 05 2019 10:27pm

How much contact width are you actually getting/need?
I'm thinking of the rollers which run between the tread blocks and how little could be gotten away with.

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Kepler   1 GW

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Re: Full suspension mountain bike Friction Drive

Post by Kepler » Aug 05 2019 11:16pm

I haven't personally tired it but other members have. It would be good to hear how the tire is standing up.

viewtopic.php?f=28&t=96581&start=100#p1479759


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Grantmac   10 kW

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Re: Full suspension mountain bike Friction Drive

Post by Grantmac » Aug 05 2019 11:43pm

That's exactly the one I'm curious about. Possibly if it could be combined with the cogged roller idea, but with enough space that the cogs would only make contact if it started slipping.

Unaserit   1 µW

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Re: Full suspension mountain bike Friction Drive

Post by Unaserit » Aug 08 2019 5:03am

Ride infrequently. Still rocking a Cannondale F700 from time-to-time. That's the model Cannondale loaded with as much '90s tech as was available: Headshok, Grip Shift X-Ray shifters, Onza pedals with the rubber inserts, and a subpar proprietary cable pivot for the cantilever brakes that was dropped for a Tri-Dangle which wasn't exactly an improvement.

Haven't looked at bikes in 20 years. What are the options for used, full suspension https://bikesbros.com/full-suspension-mountain-bikes/, titanium mountain bikes? Something I can find on Craigslist around a grand. Found a few hard tails in what appeared to be decent shape for less so am assuming that's a reasonable target.

Litespeed used to be good. Dean used to be good but more boutique. XC/all-around suspension rear suspension meaning it doesn't need to have huge travel (but more than a Unicoi). A good rear suspension design would be nice. Horst link? Something better than the unified rear triangles that were new 20 years ago. Titanium for no other reason than the cool factor.

Thanks.

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Re: Full suspension mountain bike Friction Drive

Post by Howiep » Aug 28 2019 1:26am

Grantmac wrote:
Aug 05 2019 11:43pm
That's exactly the one I'm curious about. Possibly if it could be combined with the cogged roller idea, but with enough space that the cogs would only make contact if it started slipping.
Each side of my roller is 4mm wide, so 8mm total. The actual contact area would be slightly more because it's angled.

There are no problems with slippage when the pressure is dialed in right, but I don’t yet know if the wear is acceptable - I rode about 70km of mixed road and mtb with almost no noticeable wear. But then I accidentally let the motor mount get crooked (maybe due to heat, or me constantly messing with it) and it munched almost through to the casing threads in about 20km. Just like a car with crooked wheel alignment.

The new mount I'm making should keep a straight even contact much better, and I'll post again when I’ve done a longer period of testing with it.


I also tried a "makes contact with casing around knobs" roller with Specialized Slaughter, and Maxxis Forekaster tyres but had the same result as Kepler.

There is always a tiny bit of slip with this system because rubber. As a result the voids in the roller always end up scootching up to the edge of the tread blocks. Even though it's not pushing on them hard, it's still striking each knob as it rolls around, which makes for the jet engine noise Kepler aptly described.

However I did find it difficult to correctly mesh the roller to the tread knobs over the curved tyre profile as the circumference changes from centre to edge. A nicely meshing volute gear profile may be more successful.

Here is the one I tried with the Slaughter tyre:
Slaughter-Roller.JPG
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SlowCo   100 kW

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Re: Full suspension mountain bike Friction Drive

Post by SlowCo » Aug 28 2019 7:05am

Great thread, thanks for all the info.

Grantmac   10 kW

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Re: Full suspension mountain bike Friction Drive

Post by Grantmac » Aug 28 2019 11:53am

It sounds as though slippage is just a fact of life. Interesting to hear that 8mm of contact can work. Although it seems like a rigid mount becomes very important with the narrow contact patch.

I wonder if you could create a roller which makes contact with the sides of the knobs or if you would have the same noise issue?

Leeleeducati   100 W

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Re: Full suspension mountain bike Friction Drive

Post by Leeleeducati » Aug 29 2019 12:08pm

Has anyone on ES successfully driven the rim? Stumbled on this the other day, seems like this concept could solve some of these problems as well as I’m sure opening up a bunch of new ones :). Thought I’d share, may spark some ideas for those that haven’t seen it.

http://www.velogical-engineering.com/ve ... rofittable

andrea_104kg   100 W

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Re: Full suspension mountain bike Friction Drive

Post by andrea_104kg » Nov 28 2019 3:59pm


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Kepler   1 GW

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Re: Full suspension mountain bike Friction Drive

Post by Kepler » Feb 16 2020 2:56am

Finally found a true MTB tire that works with a friction drive. I am not sure if the tire is new model but was very pleased to find it.

Tire is a Schwalbe Smart Sam. 2.6" wide 29'er. It has a thread section down the middle of the tire that is closely packed enough to run a roller over without sounding you have pegged a playing card in your spokes.

Fitted the tire to my current friction drive MTB and added an 8mm wide drive ring to motor to pick up the centre tread. Only just started playing around with this configuration but it is looking very promising. The drive ring is just made from aluminium at the moment but if wear is an issue, I will make it from steel. Also keen to play around with knurling the ring for better grip. So far I have put 200W through it with relatively light tension without slip in dry conditions.
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I have now fitted the tire to my 2019 Specialized Carbon Comp Stump Jumper to see how it performs out on the tracks. Really pleased with how it has performed so far. Found the grip to be more then adequate compared to the stock tire even in quite muddy conditions.
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So I can see a new Friction Drive project in my future. Hope to bring all my learnings together on this one.

The Plan:

2019 Specialized Carbon Comp Stump Jumper donor bike.
Internally mounted and fully hidden batteries. (200 Whr) (Bike has SWAT internal storage system)
Internally mounted and fully hidden speed controller and associated electronics
Pivoting friction drive motor that will mechanically decouple from the tire when assist is not required
Regen capabilities
Range extender bottle battery (200Whr) compatible.
150W typical assist with 300W boost when required.
Will only add 1.5kg to the stock bike's weight making the bike a full 2kg lighter then the new benchmark Specialized S Works Levo SL.

Stay tuned. New thread to begin shortly. :)
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telcosteve   10 mW

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Re: Full suspension mountain bike Friction Drive

Post by telcosteve » Feb 16 2020 9:20am

This is great. looking forward to another build thread!

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