First bike idea, how would I attach sprocket to rear wheel?

Hi, been thinking about this on/off for a few years, got this bike just over a month ago.
Wanting to attach an RC motor of some sort (are 12v motors enough? With no job etcetc I'd like to avoid having to get multiple 12v packs to put in series), don't want to go the hub route.

I have 0 experience, but how hard can it be?
Here was my idea:



I've got about 85mm in height to work with, probably about the same or less in width.
With that idea, I need to figure out a way to attach a sprocket of some sort to the rear wheel,
which would also mean that the motor would be always spinning while the bike is in use (is this bad for the motor?).


(Somehow attach here. Bolt on, clamped tight? Hurt spokes?)

Battery plan for later would be to have the batteries along the top of the frame.

The reason for it all would be to help on 10km-ish (6 mile) rides, as they're not too fun on 20" wheels with my low gearing ha.
So yeah, not sure on what power I need. Mostly to make things faster on slight inclines probably (or even to just reach the estimated google maps bicycle speeds of around 10km/h lol).

I weigh 55kg, bike weighs about 10kg. Any other information I need?
Is this viable in any way?

If it were me, I'd go with a new hub.
Either a disc brake hub, or a 5 speed hub...
Either fix the sprocket to disk mount and use a freewheel on the motor shaft, or substitute cassette for two single sprockets side by side.
Though I think side by side would force peddles to spin without a freewheel crank?

There's quite a few ways to do it, including dual freewheels on the right side (so neither power source spins the other but both spin the wheel).

Before you decide which way to do it, I highly recommend reading as many build threads here in this subforum as you can, as far back in it's history as you can, because you'll see the advantages and disadvantages of each, and how complex or simple each one would be to build and maintain.

There's also some info in the Technical Reference subforum about different chain and sprocket types you might use.

You can also run it thru the regular bike chain, in a number of ways.


As for voltage to use, that will depend on the speed you want vs the gearing ratio you use vs the motor's speed at that voltage, and the motor's power capabilities (W) vs how much you'll pedal at that speed and the gearing ratio of the pedals.

It's going to take some reading around to learn all you will need to know for this kind of drive system, so take your time and look at those many other builds before you continue. When you're ready, we can certainly help with the details, but definitely read around first--it'll help you better understand the problems you're facing.

If you're looking for something really simple to build/install, a hubmotor is what you're after. (it can be cheaper, too, as there will be less broken stuff figuring things out )

Guess I have lots of reading to do

Thanks'

azk said:

Hi, been thinking about this on/off for a few years, got this bike just over a month ago.
Wanting to attach an RC motor of some sort (are 12v motors enough? With no job etc etc I'd like to avoid having to get multiple 12v packs to put in series), don't want to go the hub route.

I have 0 experience, but how hard can it be?
Here was my idea....

Click to expand...

I'd recommend you reconsider a rear hub motor kit, complete with battery, as it is in most cases its the better way to go. Rear hubs accommodate putting on a freewheel. Your bike remains the same in all other respects. And if money is the issue, downsize the capacity of the battery so it fits your budget. Can always get more battery latter as money allows.

Looks like a trials bike. If you are trying to commute to a location then use it as a trials bike then a friction drive that clamps on may be your best bet. You could ride to a location under power then pull the whole drive off and ride trials with a lightweight bike.

If you put an rc motor in the spot where you have it pictured you may not have room for enough reduction. Small motors turn high rpm so you would need a very small front sprocket and a very large rear sprocket.

You could use a freewheel mounted on your crank and drive through the normal chain as well. This would keep you from having to match the speed of the motor with your pedals.

the extra sprocket on the other side is part of the kit for building smokers. go google the gas powered bikes. you will find bunches for cheap.

Hi,

One way:
http://endless-sphere.com/forums/viewtopic.php?f=28&t=11690&p=177845&#p177845

I took a circle of 9 ply 1/2 inch plywood, bored a hole to the diameter of the flat end of the taper of the rear hub, put artist oil base paint on the surface of the spokes eye balled the bored hole to the hub, pressed the wood to get the marks of the paint on the wood, took a hand grinder (cut off disk) ground out the area of the spokes only, so that the wood would sit flat on the hub, (spokes into the wood) made split clamping rings to hold the wood to the spokes, drilled holes for screws, to miss spokes, (6 flat head) and nuts to clamp wood against the spokes, cleaned the hub, epoxied the wood to the hub and spokes, bolted on clamp rings.

Drilled 6 holes into the sprocket, (between spokes) using a vise clamping axle (wood on vice jaws) to hold wheel flat, put sprocket on wood, spun the wheel till the sprocket ran true, used hot melt glue in the holes to hold to wood, drilled out each hole in turn, inserting a screw and nut to hold in place as I drilled out next hole. Put epoxy between the sprocket and wood, and on each screw (to fill the hole clearance) loosely held in place with all 6 screws, spun to check sprocket to turn true, tightened the screws down, spin check again, cure.

(10:32 screws were strong enough)

Nobody seems to have pointed out the obvious, which is that there's no speed reduction in this plan. Without approximately 10:1 reduction from motor speed to wheel speed, an RC motor drive would be less than useless.

My very first e-bike was homemade with a DC scooter motor mounted under the down tube of the bike, driving a reverse threaded freewheel on the left side through a 12:144 tooth chain reduction. I had to machine for myself the motor mount, a 144t sprocket that clamped onto the teeth of a 16t freewheel, and a pulley-like chain guide that rode on the left bottom bracket cup.

It would be plausible to do something similar by using a disc hub, lockring-threaded track hub, or Currie RH/LH hub.

This seems like a super backwards thing to do, just to ride distances on a bike that was never intended for transportation. Much cheaper, easier, and more effective to get a real bike for the job. That bike won't be any good for flatland (bike dancing) after getting converted, anyway.

Chalo said:

This seems like a super backwards thing to do, just to ride distances on a bike that was never intended for transportation. Much cheaper, easier, and more effective to get a real bike for the job. That bike won't be any good for flatland (bike dancing) after getting converted, anyway.

Click to expand...

I'm sure that if anyone in the world could build something for bike dancing, it'd be you Chalo. What tunes would you play for that?
[youtube]ltrMfT4Qz5Y[/youtube]

Chalo said:

Nobody seems to have pointed out the obvious, which is that there's no speed reduction in this plan.

Click to expand...

I guess my post didn't make that obvious enough?
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=65456&p=989871#p983895

I second the friction drive idea for this bike. Mount a motor for the commute and then remove it for trials riding. Just 250-500W will give you a LOT of help when pedaling. Cheap and simple.

Might not apply here but for trials bikes i would like to see a device that drives the chain and is easilly removable. Lots of trials bikes use freewheeling crank arms instead of fw on the wheel. A chain puller drive wouldnt have to contend with the knobby tires like a friction drive. Basically a small modest power unit that clamps on and leaves the bike completely stock when not in use. I've added that idea to my someday list. I need a trials bike first.

arkmundi said:

Chalo said:

That bike won't be any good for flatland (bike dancing) after getting converted, anyway.

Click to expand...

I'm sure that if anyone in the world could build something for bike dancing, it'd be you Chalo. What tunes would you play for that?

Click to expand...

How about this?
[youtube]B9i95q4S_XA[/youtube]

I mistook the OP's trials bike for a flatland bike, which looks very similar. If anything, a trials bike is even less appropriate for transportation because of its lower gearing and high rolling resistance tires. But either kind of bike is surely the wrong tool for the job if you want to get around.

Some flatland trickery:
[youtube]6A_aGlxTMKM[/youtube]

For a different angle of attack, how about an ebike that can carry or tow the trials bike?

Ykick said:

For a different angle of attack, how about an ebike that can carry or tow the trials bike?

Click to expand...

Now thats a clever solution. Trials bikes are light and if you break something you can still get home.

Guess a pusher trailer wouldnt be a bad solution either.

why the rear wheel --one speed
Which needs to be in the range thats usefull , like higher ratio if biking on flat or lower if mostly up hills --crank drive unless the wattage is over 1000