212cc friction drive.. Will it work or not?

[Motorbike Mike]

Yes 1 bearing will swivel but 2 bearings fastened together on opposite sides of the mounting plate (and on the same shaft) will not. If I have to upsize the diameter of the rubber drive wheel to get it to grip to the tire then its worth a try.

 

[Barnfresh]

Will it work? Of course it will work! How well it works is going to be up to your patience and engineering skills. I learned a lot on my first friction drive project using a super torquey electric motor. Toughest part was overcoming premature tire wear. Good luck with the project MM and please continue to post your progress.

 

[CrazyDan]

A small pneumatic tire might be usable for the roller.

 

[Deleted member 26224]

I think you need more space between the bearings. Those things feel great when they are new but wait till you run it some then you will know what I mean. They have no way of locking them down from moving within the housing. The only thing you get is the pin on the od of the bearing that wedges against the valley cast in the housing with the inner race locked down to the shaft.

The skinny flat aluminum plate will twist up, or clockwise looking from the back of the bike, because of the roller as it tries to climb up on the tire. Especially with 212 I think the FD assembly has to primarily be a part of the bike that holds the rear wheel.

 

[Motorbike Mike]

I think you need more space between the bearings. Those things feel great when they are new but wait till you run it some then you will know what I mean. They have no way of locking them down from moving within the housing. The only thing you get is the pin on the od of the bearing that wedges against the valley cast in the housing with the inner race locked down to the shaft.

The skinny flat aluminum plate will twist up, or clockwise looking from the back of the bike, because of the roller as it tries to climb up on the tire. Especially with 212 I think the FD assembly has to primarily be a part of the bike that holds the rear wheel.

More space between the bearings is definitely better but... dimensions are what they are and it will have to do.

I doubt a 212 would be able to twist the flat plate (at this short length) but I could be wrong. If it does twist I would just upsize the thickness until it didn’t fail.

 

[LewieBike]

Should work fine, especially if you disconnect the governor so you don't get that big pulse of full throttle when powering up from idle. Make a few different sizes of friction wheels so you can experiment with the best size for hill climbing and speed. I think you'll be fine with the bearing pillow blocks separated by the width of the plate, you can always add more thickness by cutting a few more plate chunks to stack between the bearings.

Frankly I'd be more concerned with the chain drive, this can work just as well with a pair of V-belt pulleys and an idler to pull in the tension on the V-belts to clutch the drive.

 

[bike4life]

I would suppose it should. but would be worried about the tires wearing out. About your little gizmo, I disagree with tony. That looks like 3/8 plate. It will NOT bend, but... I don't know why you are using aluminum. Steel is the way to go for anything structural. Not sure how you can attach it to the frame as it cant be welded because its not steel. I would use steel instead, as its not brittle at failure, can be welded, and has a much higher modulus. Steel is 3x stronger than aluminum given the same scenario. 30gpa vs 10gpa. Like Lewiebike i would have the engine above the wheel and not in the frame.

Here is some stuff. You didn't give dimensions. I assumed you have a 3/8 x 4" x 8" plate of aluminum. If your plate is less than 3/8" i would fail it. Even 1/2 of that, around 3/16 would mean 8x the center deflection. So you take 0.03x8 and get a whole 1/4". That's horrendous. 3/8 is the bare minimum. To bend this out of standard deflection tolerances.... Assuming its placed flat between two points like plywood such that its only 3/8" tall and 4" wide and spans 8". Here is the graphs of the forces. I know you have it vertical and with gears and crap so its not a purely accurate representation but....

The moment of inertia is 0.0175

Why not add a cnc wheel hub gear to the tire and run a chain, it would be easier. I think friction drive well creates friction and 7hp is a lot of friction....
Friction = Coefficient of Friction x Normal Force, so i think you can calculate that with the 8ftlbs torque of a 212cc and turn that into newtons and multiply it out if you want....

It says that it would bend 0.03" at the center given a 500lb center point load across an 8" span of plate. 500lb is overkill but has a good safety factor i would guess With steel, it would be roughly 0.01".
Aluminum sucks for building most things IMHO....

 

[CrazyDan]

I would suppose it should. but would be worried about the tires wearing out. About your little gizmo, I disagree with tony. That looks like 3/8 plate. It will NOT bend, but... I don't know why you are using aluminum. Steel is the way to go for anything structural. Not sure how you can attach it to the frame as it cant be welded because its not steel. I would use steel instead, as its not brittle at failure, can be welded, and has a much higher modulus. Steel is 3x stronger than aluminum given the same scenario. 30gpa vs 10gpa. Like Lewiebike i would have the engine above the wheel and not in the frame.

Here is some stuff. You didn't give dimensions. I assumed you have a 3/8 x 4" x 8" plate of aluminum. If your plate is less than 3/8" i would fail it. Even 1/2 of that, around 3/16 would mean 8x the center deflection. So you take 0.03x8 and get a whole 1/4". That's horrendous. 3/8 is the bare minimum. To bend this out of standard deflection tolerances.... Assuming its placed flat between two points like plywood such that its only 3/8" tall and 4" wide and spans 8". Here is the graphs of the forces. I know you have it vertical and with gears and crap so its not a purely accurate representation but....

The moment of inertia is 0.0175

This nerd's math is correct, he reminds me of a 17 year old me.

Why not add a cnc wheel hub gear to the tire and run a chain, it would be easier. I think friction drive well creates friction and 7hp is a lot of friction....
Friction = Coefficient of Friction x Normal Force, so i think you can calculate that with the 8ftlbs torque of a 212cc and turn that into newtons and multiply it out if you want....

It says that it would bend 0.03" at the center given a 500lb center point load across an 8" span of plate. 500lb is overkill but has a good safety factor i would guess With steel, it would be roughly 0.01".
Aluminum sucks for building most things IMHO....

I agree with overkill, but 500lbs is beyond overkill. Unless you are doing over a 60:1 reduction the lb/ft of a near stock 212 isn't overdoing that. as long as you have proper plate thickness or gussets.
I think I might be overdoing it on my jackshaft output to chainring at 50.37:1 with near 3 lb/ft on the engine output. So I'm easily maxing out at over 100 lb/ft at that point. Yes that spot is a weak point.

 

[Ralpho]

A 300 hundred ft.lb engine on a car, only has (4) 3/8 bolts on a 3/16 flex plate to the transmission. If the materials and geometry are good then that is what really matters.

 

[bike4life]

This nerd's math is correct, he reminds me of a 17 year old me.


I agree with overkill, but 500lbs is beyond overkill. Unless you are doing over a 60:1 reduction the lb/ft of a near stock 212 isn't overdoing that. as long as you have proper plate thickness or gussets.
I think I might be overdoing it on my jackshaft output to chainring at 50.37:1 with near 3 lb/ft on the engine output. So I'm easily maxing out at over 100 lb/ft at that point. Yes that spot is a weak point.

Yeah these days I like using overkill for

This nerd's math is correct, he reminds me of a 17 year old me.


I agree with overkill, but 500lbs is beyond overkill. Unless you are doing over a 60:1 reduction the lb/ft of a near stock 212 isn't overdoing that. as long as you have proper plate thickness or gussets.
I think I might be overdoing it on my jackshaft output to chainring at 50.37:1 with near 3 lb/ft on the engine output. So I'm easily maxing out at over 100 lb/ft at that point. Yes that spot is a weak point.

Back in the day most things were built very very overkill. Old table saws from the early 1900s weighed nearly a 1000lbs of cast iron. If you look at the gears and axles and such in old machinery they are over rated by a huge factor. The only thing left that is still overbuilt are trains. It’s crazy, a hunk of 50tons of steel..

For our purposes, it doesn’t take much extra money, surprisingly to build our fabrication work overkill. Yeah engines and gears and bearings are pricey but steel plate and angle isn’t. Structural Steel is around 50cents/lb. doesn’t hurt too much to use thicker plates and axles. Especially as my 5/8 one broke but I just got the parts of the upgraded axle and they are crazy...
Yes and don’t use aluminum. Like 3 years ago I made a crappy trailer thing that hitched on with aluminum angle and it twisted in half and broke in about 20minutes. Replaced it with steel of around the same dimensions and it held up ok. Plus steel is cheaper.