Attach Bicycle Tire to Live Axle

[EVBiker2000]

Okay guys, I am stuck.

I want to build an electric push trailer for my bike. It will have two 24 inch bicycle tires, one on each side. There will be a live axle that connects to both bicycle tires and a single 48V motor will drive a sprocket between the tires.

But I can't figure out how to attach the bicycle tires to the live axle so that when the single axle turns both wheels turn also. Please help me, my ship has hit high ground. :lol:

 

[spinningmagnets]

Here's a push-trailer thread that may have some useful info and pics:

http://endless-sphere.com/forums/viewtopic.php?f=6&t=9855

Get two pillow block bearings and a keyed shaft, they are available and cheap at any industrial or farm supply, such as Graingers. They are available with common shaft sizes such as 1", 3/4", 1/2", 5/16", etc. Slide on a a pulley, and drill/attach a bicycle chainring (perhaps from a Kart site or Staton-inc). A 47T chainring is pretty common on trash-day road bikes.

I honestly don't think you need to have both wheels powered, but if you really want that, perhaps start with a wheelbarrow like the pic below. I noticed them recently, and they use 16"/20" bicycle tires.

 

[Drunkskunk]

Normal Bicycle Axles don't turn, they are stationary. The hub turns on the axle so there isn't a way to have a single axle turn both wheels.

there are some Trikes that use a common drive axle and special wheel hubs. You may have better luck cutting up a trike if you want a powered axle.

 

[JEB]

I started with a trailer bike pusher driving a single wheel (2 wheel pusher) using a 2 hp motor the thing would crab wearing out the tires in short order. I ended up with a jack shaft from the motor to drive 2 freewheels one to each wheel, one drives when turning corners, both driving when going straight.

 

[EVBiker2000]

Yeah, I think the pillow blocks are the way to go for the live axle. Here is some good pics of how I would do the motor drive and the live axle...

Pillow Blocks

Spocket and chain attached to live axle using a axle hub

I think it is important to go with bicycle tires for the following reasons...

High pressure tires can be run at low pressures to add some shock absorbtion for the potholes.
Tire treads can be easily replace every year or so from wear.
20 - 24 inch tires need to be used for greater mph.

But because bicycle tires use a fixed axle, I'm stuck at this point. There must be a way to do this without complexity or welding. Any ideas?

 

[Drunkskunk]

there is no simple answer, but it could be done off a jackshaft ahead or behind the wheels driving the normal bike sprockets through chains. Since the wheels would keep their freewheel, the outside wheel would be able to "overrun" the chain speed in a turn, and work effectivly like a differential.

 

[spinningmagnets]

I ended up with a jack shaft from the motor to drive 2 freewheels one to each wheel, one drives when turning corners, both driving when going straight.

I have never thought of that, JEB/Drunkskunk. It would solve several problems. Differentials were put on early cars because in a sharp turn either one wheel would be drug around because its spinning slower than the other, or the other would skid and hop because it was spinning faster...depending on which tire had traction in the turn. Having a single shaft driving two chains, that are driving two wheels, with a freewheel at each wheel, would definitely work well...thanks for posting that!

 

[EVBiker2000]

Hey Jeb, how did you attach the differential axle to the freewheels of each tire? That's the part I'm stuck on.

 

[spinningmagnets]

Perhaps mount a full-width jackshaft ahead of both the 20" wheels (on two pillow-blocks), with each shaft end having a sprocket and chain that travels back to a 20" BMX rear wheel, each with a stock freewheel that has a chainring (47T-ish) attached with an aluminum disc?

Consider having the electric motor drive the jackshaft with a toothed belt and the appropriate pulleys (rather than a chain).

 

[Papa]

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[EVBiker2000]

spinningmagnets, good idea! I like it. I drew of a picture of what you described.

One thing tho, why did you suggest the belt drive instead of the drain drive?

Here's the design so far. The drawing is pretty much to scale...the frame is 1.5 in 14 gauge steel square tubing, 36 inches long and about 26 inches wide with 20 inch bicycle tires. This will be carrying 4 12Volt, 125 Amp Hr Deep Cycle batteries (240 lbs). I have a long long way to commute each day and I don't want to ever go past 50% DOD.

 

[Papa]

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[spinningmagnets]

I first read about a high RPM motor with a 2-stage drive belt/chain from Eric Peltzers electric bike a few years ago. If you have a choice of motors, using a higher RPM motor helps its efficiency (provides more range from the same size battery, or...same range from a smaller, lighter, less expensive battery)
Doing so also helps heat dissipation and system torque per volt applied.

Peltzer started with a tiny motor cog driving a giant wheel-sprocket with a single chain. The tiny high-RPM cog was very noisy and caused rapid wear on the chain. He tried two-stages with two chains, and it allowed him to use more normal-sized sprockets that were easily available and cheap. However the first stage (motor to jackshaft) was still very noisy. Someone suggested he try a toothed belt/pulleys and that ended up working well.

Recently, Recumpence has developed a tiny well-engineered and beautifully machined 2-stage drive for small RC motors. They work well. Nothing wrong with using two belts, but bike chains are strong, cheap, and easy to acquire and change their length for the second stage when developing a project. But I suppose it also depends on the RPM range your motor was designed for. Direct-drive hub motors are simple and inexpensive, but hard acceleration from a stop converts much of your battery into heat at low RPMs.

This small purple motor is the size of a coffee cup, but it runs at over 3,000 RPMs...

 

[EVBiker2000]

Ok, so that makes sense. I have a 48V, 1000W, MY1020 motor and it operates at around 3000 RPM. So I guess it's going to make some noise. I would go with a belt drive for this, but I'm not sure I can locate the parts. I'm even having trouble locating the parts for the chain system. I can only find keyed live axle hubs that have 1" or 0.75" bore. I think that is way too big....I think 0.5" steel axles would be large enough for the jack shaft. All that turns up is go kart stuff like this northern tool hub ....

Does anyone know where I can find keyed hubs like this for 0.5" axles? It may turn out that since 1" bore is so widely used that it's cheaper for the parts than the smaller axles.

 

[EVBiker2000]

Well, thinking about this some more. Maybe I can get away with the following:

2 - pillow block bearing, 0.5" bore
1 - shaft, steel keyed, 0.5" diameter x 26" length
3 - sprocket, 0.5" bore, with keyway and set screws
6 - shaft collars, 0.5" inner diameter

Here's the sprockets I'm referring to:

It seems like going this keyed sprocket with setscrew opens up a wider selection of parts. But I don't know about the mechanical design aspect. If I do a 4:1 ratio from the motor sprocket to the drive socket on the jack shaft, the whole steel axle will be spinning at around 700 rpm. I'm not sure if the sprockets/shaft collar combination can handle this. The 48V, 1000Watt motor puts out a lot of torque.

Any thoughts about going with the keyed sprockets/shaft collars versus the expensive hub/sprocket adapter from Northern Tool? Do I even need the shaft collars, or is the set screws too under-designed for this? (I put the image of the expensive hub adapter in my post above)

 

[spinningmagnets]

The pillow-block bearings are relatively cheap because of mass production. They are popular in farming equipment and industrial applications. In spite of their affordability, they can handle 3,000 RPMs easily and will last for years if you give them a monthly squirt of quality grease. I "think" Grainger is the best place to start, but there are others once you start looking locally (to avoid waits and shipping charges). http://www.grainger.com/Grainger/ww...ockets&op=search&Ntt=sprockets&N=0&sst=subset

Here's a pic of an industrial jackshaft with a centrifugal clutch. Having two freewheels makes this a self-actuating 2-speed transmission:

http://endless-sphere.com/forums/viewtopic.php?f=10&t=9695

 

[EVBiker2000]

That is cool! But way beyond me for now.

Thanks for the pillow block answer. How about the sprockets that have the set screws as opposed to the go kart hub/sprocket adapter? Looks risky to me but I'm a newbie. :lol:

 

[EVBiker2000]

wow, I am really stuck.

I can't find a #35 pitch sprocket that will fit my MY1020 Motor. I did find a #25 sprocket that fits the motor, but then I can't find a #25 Sprocket that has a 1" bore and is keyed; nor can I find a #25 sprocket with a 2" I.D. that will fit the Northern Tool hub adapter.

Woe is me....any one got any massive sprocket parts links?

 

[amberwolf]

Maybe try
http://mcmaster-carr.com
Lots of interesting things there; oh what I could build if I A) knew what I was doing and B) had somebody else's credit card. :lol:

 

[EVBiker2000]

ok, thanks. I forgot about McMaster Carr.

I did manage to find Aluminum sprockets that are #25 and will fit on to a keyed aluminum hub adapter with 0.5" bore size. Here's what I found....

http://www.andymark.biz/am-0077.html

Material: 6061 Aluminum
Bore: 0.501-505" diameter bore, with 1/8" keyway
Bolt Pattern: 0.204" diameter holes, evenly spaced on a 1.875" diameter bolt circle
Outside diameter: 2.25"





So with this I could use a #25 Double D gear on the motor, chain that to the jack shaft that has this alumimum sprocket/hub adapter on a 0.5" steel shaft.

Then use two more of these that chain up to #25 sprockets/freewheels on the 2 bicycle tires of the trailer.

Things to be concerned of ...

1. Wear of #25 chain on the aluminum sprockets?
2. Would 0.5" x 26" steel jack shaft be too undersized for this 250+ pound trailer?

 

[REdiculous]

1. Wear shouldn't be a huge issue if you get it properly aligned.
2. 0.5" is pretty thick..go for it!

I'm using a regular back wheel hub as my jackshaft so I'm sure whatever you do will be better. later