Bike Pusher

Astropower · Sep 4, 2014

Hello there,

I am thinking about building some device to let me feel like ebike, but device which can connect and disconnect quickly from the bike easily.
so i am thinking about e-trailer or friction motor.

what you would suggest me?

TNX

amberwolf · Sep 4, 2014

Kepler's E-boost would probably do it. Should be a link in his signature.

Astropower · Sep 6, 2014

I got some idea, i draw it.

this my idea, and i will build one.

to use small hub motor, to push the bicycle.
i will buy some parts now.

amberwolf · Sep 6, 2014

Keep in mind you need a lot of weight on the motor to get any traction out of it using it like that. There are some other problems you may have doing it that way, too. Read up here on ES on the various powered assist trailers, especially single-wheel trailers, and BOB trailers, to get an idea of the issues involved.

Astropower · Sep 7, 2014

Hi,

Thanks for your advice.

Theoretically, Wheel with good grip should done it pretty well,

by the drawing we can see, if the front wheel cannot move, distance of the two wheels (blue lines) will generate angular strength (purple line),
and when the hub motor, will start pushing, the green force will start to apply - motor push forward and back wheel will start lose weight. which lead to yellow force start to work. means bike start to forward, and hub motor will have more traction.

this is theoretical only, i will test is soon.

Astropower · Sep 8, 2014

Step one,

i got the Hub motor about 9-8 inch size, 36V 250W.
i build somes simple device, to connect the motor to bike axis.

soon i will connect to controller and battery, and test it.

here the pictures:

tahustvedt · Sep 8, 2014

What about turning? Does the motor wheel skid or do ou have a spherical bearing in the dropout hinge?

yawstick · Sep 9, 2014

Thats pretty slick... I think I would have arms from both sides of the bike.... and have battery sitting on top of it. I think skidding will be minimal once underway but at very low speed such as maneuvering it around may have a tendency to want to break the arm off at the attachment point. Would be very easy to have it where you could rotate it up off the ground until ready to go. Interested to see how this turns out.

dingoEsride · Sep 9, 2014

It looks like from here it would be simpler to apply the pressure to the wheel not the road in reverse, ratio should be the same, traction will still be an issue, btw I like that little hub motor

JEB · Sep 9, 2014

My experience you need traction but get a lot of bounce, you need to spring load it down, or add some weight, like batteries, but then add a suspension frame (to hold batteries), a tire with a lot of rubber/air is a bouncing ball, on a rough road it will spend a lot of time in the air, not road.

gogo · Sep 9, 2014

If bounce is a problem you could always make a friction drive onto the back bicycle wheel.

Hillhater · Sep 9, 2014

dingoEsride said:
It looks like from here it would be simpler to apply the pressure to the wheel not the road in reverse, ratio should be the same, traction will still be an issue, btw I like that little hub motor

++1^^
Change it to a friction drive direct onto the tyre.
Much less issues, just relocate the pivot point.
Also, it makes no difference if the link arm is curved or just straight !

johnrobholmes · Sep 9, 2014

I built a pusher out of this trailer

http://www.mayacycle.com/

Perfect steering angle and got plenty of traction with the battery in the trailer. It felt extremely stable while powering during turns and never made me nervous of high or low sides.

yawstick · Sep 9, 2014

johnrobholmes said:
I built a pusher out of this trailer

http://www.mayacycle.com/

Perfect steering angle and got plenty of traction with the battery in the trailer. It felt extremely stable while powering during turns and never made me nervous of high or low sides.

Well that pretty effectively shows the kind of geometry you need on your pusher. Doubling as a trailer that would bolt to a trike or a bike is pretty dang handy.

Astropower · Sep 10, 2014

Hello,

Thanka all for sharing your thoughts and your opinions, i'm sure it would help me improve this thing.

I really dont like much the friction drive, because several reasons:
1. RC motor generate lot of noice because high RPM. i like the quiet of gearless hubmotor.
2. Need some mechanics system to make good pressure to able friction between the motor and wheel, which not easy to install and each bicycle.
3. Friction driver, not support bicycle with wheel cover (which protect from water and mud)
4. Absence of good friction, will cause tire damage.
5. I am using off road tire on my bicycle, off-road tire + Friction driver = not good combination in simple words.
6. Friction driver will suffer on wet or muddy rid.

Despite all this, i like the idea of small and light weight thinks, so think i have solution for most of the problems of friction driver, maybe it will be my next project

.

for now, some updates,
i purchase cheap chinese controler 350W and RC Lipo batteries, 3x 14.4V 2200mA = 43.2V 2200mA.
here some pictures:

Astropower · Sep 10, 2014

Now i need to solve some issue on the turns, that the hubwheel not be draged.

About the friction between the hubmotor and the road, test results:
Zero speed - only 30% power is available, more than that, the tire starting to slipping.
About 2-3MPH (3-5Km/H) 50% power is available.
About 10MPH (16Km/h) 85-90% power is available.
About 15MPH and up (24Km/h) all the power is available.

Hubmotor weight about 3.5KG (7.7 pounds).
This results on standard road.

Here I made my first experiment on my wife,
She like it

Video:
http://vimeo.com/105734039

Hillhater · Sep 10, 2014

Astropower said:
Hello,

Thanka all for sharing your thoughts and your opinions, i'm sure it would help me improve this thing.

I really dont like much the friction drive, because several reasons:
1. RC motor generate lot of noice because high RPM. i like the quiet of gearless hubmotor.
2. Need some mechanics system to make good pressure to able friction between the motor and wheel, which not easy to install and each bicycle.
3. Friction driver, not support bicycle with wheel cover (which protect from water and mud)
4. Absence of good friction, will cause tire damage.
5. I am using off road tire on my bicycle, off-road tire + Friction driver = not good combination in simple words.
6. Friction driver will suffer on wet or muddy rid.

Despite all this, i like the idea of small and light weight thinks, so think i have solution for most of the problems of friction driver, maybe it will be my next project .

You miss understand.
The suggestion was to use your existing small hub motor and tyre as the friction drive onto the tyre instead of the road.
With some attention to getting the correct pivot location , it will avoid most of those reasons you listed above.
It will also ovoid the problem of scrub when you turn.

Astropower · Sep 10, 2014

Hello Hilter,

You are right,
This will solve me the problems in section 1, 5 & 6. and will increase the problem in section 2.
In my next project I'll think about something like this

.

Hillhater · Sep 10, 2014

Astropower said:
Hello Hilter,

You are right,
This will solve me the problems in section 1, 5 & 6. and will increase the problem in section 2.
In my next project I'll think about something like this .

With a careful position of the arm pivot point, the drive wheel will generate its own load force vector onto the tyre, and solve your problem no 2 .!
Read the friction drive threads if you do not understand the principle of non concentric arc,s for the drive mount.
Also you could arrange it to be behind the rear of the tyre cover (problem 3).

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