Using two drive chains to one hub - one on each side?

Guys, I see a lot of you working on how to combine pedal and motor power and see it finally coming together with a few questions about Matt's drive in the last few days in other posts.

Here's my thinking - not new at all, but incomplete - I hope it contributes something.

If you use use a chain on the left side of the rear wheel hub for motor power transmission, you could leave the pedal driven side intact.

The dual sided or "flip flop" fixed gear hubs facilitate this nicely.



Typically, these are used with a "fixed", non freewheeling sprocket on one side, and on the other side, either a similar sprocket with a different amount of teeth (for a different "fixed" ratio) or a freewheel to allow the bike to coast.



My Motobecane moped uses a freewheel on the right side and a "fixed" 41 tooth (or more, I have a 45 and a 50 for experimentation later) sprocket on the left - the left being driven by the motor. I'll edit with a picture as soon as I have the opportunity, but suffice to say it's pretty much the exact same setup.

If you're powering a BMX with a huge amount of horsepower, a single ratio is perfect. But I hear from everyone else that being able to shift is really important. Driving both sides of the rear hub would mean you'd need a left-side derailleur to accomplish this - unless you could change the ratio somewhere further up the driveline. I think it was Miles that proposed the two-speed "retro direct" concept, which I like.

Here's my idea of an alternative.


Now on this particular moped, the 41T sprocket is driven by a 14T cog on an 8" v-belt pulley. That pulley is driven by the motor, but here's where it gets interesting.

The motor (on "V" designated models) is fitted with a continuously variable pulley, tensioned by a spring on the motor mount. Like so:

[youtube]1LCi6pVTb9g[/youtube]

This bike has it's crank arms removed and there are footpegs installed where they should be. But the pedal crank shaft (bottom bracket) supports the driven pulley (left side) as well as the sprocket for the pedal chain (right side).

You can see the pedal chain sprocket sitting there in the video without a chain on it. This shaft turns when you pedal - the driven pulley is on a roller bearing on the other side and so can spin independently.

The variable pulley incorporates a clutch as well so there is no resistance when pedaling.

Could this be done with an electric motor instead of gas? I don't see why not!

A crank with space on the left side for a driven pulley+sprocket would have to be engineered, that's the only "hard" part. These variable pulleys are widely available as aftermarket performance parts for many different bikes, not just Motobecane.

Worth a think?

If you're powering a BMX with a huge amount of horsepower, a single ratio is perfect

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Hello, I agree with you here. I did some research and found that the specialized fuse 1 and 2 bmx bikes come with a 13t freewheel on the right, and left hand threads on the left for 13t or 14t LHD freewheels. I plan on putting an 80t sprocket over the left freewheel and using motor direct drive to wheel.

80T!

That will be huge! What's your voltage and motor KV? What size drive sprocket on the motor?

More:

Use a Paul Components Disk WORD and machine an adapter so you can bolt a chainring on the left where the disk brake is supposed to be.





Of course, then you couldn't have a rear disk, but oh well.

I guess I should have said #25 chain sprocket, so 80t isn't very big.
24V
135Kv
16t sprocket on motor
top speed will be geared for 42mph, if it doesnt accelerate well I may try 90t or higher on rear.

northernmike said:

Guys, I see a lot of you working on how to combine pedal and motor power and see it finally coming together

The variable pulley incorporates a clutch as well so there is no resistance when pedaling.

Could this be done with an electric motor instead of gas? I don't see why not!

A crank with space on the left side for a driven pulley+sprocket would have to be engineered, that's the only "hard" part. These variable pulleys are widely available as aftermarket performance parts for many different bikes, not just Motobecane.

Worth a think?

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I am slowly getting some parts up together to try this, I think it could work really well but it would have to be made small and compact enough for it to be any good on a pushbike. But first things first for me, got to finish my rc setup e-trials bike 8)

Yes, you could use a V belt CVT, but they are not very efficient.....

Yes, you could use a V belt CVT, but they are not very efficient.....

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thats what I was thinking, a lot of things on gas powered vehicles can be designed without much thought of efficiency as long as it works. maybe someone can come up with a new design that is more efficient somehow

I would like to see a source for the efficiency of CVT V belt. I have seen it when comparing gearbelt pulley vs. V belt, but they said it CAN be very inefficient, I wonder how a properly setup V belt drive really is. Maybe you can get 90% efficiency, but overpowered and geared might make it worth it.

Now that variator creating friction when the plates are squeezed together is another story, I'm not expert (except online) :wink: , but it seems this would be a drain. Mike, I wonder if you started cold, and then ran the motor up and down for a minute, if you could get a temp reading on the variator, maybe then you so what is going on, granted the motor will heat it a lil. DOH... That wasn't yours in the video... Does anybody have one that could be tested?

You know looking at the picture of that hub makes me think that an adapter could be made in a universal size to fit against the 36 spoke holes, bolted on, and the shorter spokes attached outside on 36 holes on the adapter. And then of course you could bolt anything you want to the adapter ring, and still keep your disk brake too.

Mike, do you have a better picture of a high end Moped rear hub? How wide are they usually?

Guys, I already ditched my variator ...





Right now I feel my gearing is a bit on the high side, though.

Also, I ordered a better driven pulley, should see it next week:



I hear what you're saying about the loss in efficiency. That IS a concern, and should be looked into. I wonder if there's another way to change gears before the rear hub? Anyway...


Moped rear hub:







Note these have cable actuated drum brakes, parts are still readily available.

This post seems to have gone a bit off track. Oh well, that is what it is about here. Anyway, to get back to 2 chains driving one hub. I have come up with a good way to do that on my current build. The pics are all there and what you need is all there as well, with a couple of ways to set it up.

http://endless-sphere.com/forums/viewtopic.php?f=28&t=8492

The short of it is, to use an externally threaded cassette hub. You can still find the older uniglide ones that are already threaded, or you could cut threads on a newer on with the right die. Then you use what ever standard bike sprockets you want and can fit on the hub to give you several gears for the motor, using the rear derailleur. You thread a freewheel on the cassette body to hold the sprockets on and drive that with the pedals. If you are using a bike with a triple or double crank and front derailleur, you can even have 2 or 3 gears for your pedals.

The alternative way to do it is to stack 2 freewheels on the rear hub and run a single speed for the motor and the pedals. I believe this is what Matt has done on his PK, but I can't quite tell from the pictures. Either way it is quite clean and shouldn't be much harder to remove the rear wheel than a standard bike. Unlike driving both sides of the hub. Also, it allows for gears on the motor and the pedals, so you can pedal efficiently with the motor, or without the motor. It lastly uses all the bike components, so there is very little modification of the standard bike drive train. If you didn't modify the bike any other way for mounting the motor or batteries, you could easily return the bike to a standard bike.

I almost have my drive set up, I am struggling with an extra wide tire on a chopper bike. It makes the rear hub a bit of a pain. On a standard rear wheel, it only takes swapping out the hub or cassette body, or cutting threads on the cassette body.

Hope this helps.

FM

Hey Guys,

I will try not to hijack this thread. But, I wanted to give my $.02.....

On my PK, I have one freewheel on the right side with two sprockets mounted to it. What I did was take a 22 tooth White Industries freewheel (used because it does not have the slots in the side) and drilled 12 holes around the sprocket to mount an aluminum adaptor plate to. That adaptor plate holds a 94mm BCD 52 tooth sprocket. So, the 22 tooth pedal sprocket and the 52 tooth E-drive sprocket turn together. The E-drive has a freewheel on the jackshaft output sprocket and I have freewheeling cranks (this thing has 3 White Industries freewheels). This setup allows for pedalling, motoring, or both combined without any interfereance.

Now, I am a big fan of using the disc brake flange on the left side of the hub and a freewheel on the E-drive output shaft. That is the most elegent system and only requires minimal modification to accomplish.

I think the twin right side chains like mine is a good setup assuming you are willing to do a bit of fiddling to get it all sorted out.

Matt

You can still find the older uniglide ones that are already threaded, or you could cut threads on a newer on with the right die

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nope, the steel used for the cassette body is hardened and cannot be threaded with a die.

Either way it is quite clean and shouldn't be much harder to remove the rear wheel than a standard bike. Unlike driving both sides of the hub

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how would it be easier? seems like It'd be about the same.

Also, it allows for gears on the motor and the pedals, so you can pedal efficiently with the motor, or without the motor

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not sure what you mean by this, but with a left drive system you can also pedal efficiently with the motor, or without the motor.
Don't forget if you put 2 freewheels on the right you have a dished wheel, if you put one on each side you have a stronger non-dished wheel.
and the minute freewheel wobble becomes more pronounced on the outer freewheel when you thread them together. more so with the cheap freewheels that you need to buy because more of the better ones have a metal ring around the threads with notches cut for removal and cannot be used as the inner freewheel.
speaking of removal its harder to remove 2 freewheels that are threaded together, sometimes they get stuck together.

Awesome, this thread is getting somewhere!

Matt thanks for sharing your secrets I thought you had a pair of freewheels on there...

I rather like the idea of left side drive right side pedal, but I am confused. On a flip flop hub both freewheel threads are cut in the same direction, and both are designed to be used on the right side (hence the name). So how does one go about using a freewheel on the left side that works with the rotation of the tire? OK, I understand that there are lock rings that the fixies use because they brake with the pedals and this force can loosen the cog, is this enough for our purposes?

Here is a good source for flip flop info

http://en.wikipedia.org/wiki/Flip-flop_hub

Oh, and where the hell did we get off topic?

We are on topic, which is the topic of how to make non-hub motor drives awesome.

A hub driven from both sides allows the use of alloy or molded plastic wheels, where no dish is possible.

As for the dual-sided-ness of freewheels, are there not BMX bikes with drives on the left side already? I saw a Haro yesterday at the park that was LHD...

quote from posted wikipedia page

Left side drive introduced a different type of flip flop hub for BMX. This hub is a Right Hand/Left Hand flip flop hub.One side of the hub allows the use of normal right hand freewheels, while the other side is threaded with left hand threads (1.375" x 24L tpi) and accepts the new left hand drive freewheels. The first/most common was the ACS South Paw Claw model, available in 16T. Later, a version of this hub was made with small metric BMX (30 mm x 1 mm) threads, left hand on one side and right hand on the other side. These hubs accepted either Left or right side drive freewheels in the smaller 13T-15T sizes.

DK bicycles introduced the dual drive hub which is a BMX Left/Right drive flip flop hub with the smaller sized metric (30 mm x 1 mm) BMX threads for 13T-15T freewheels, but also includes two threaded adapters, one left and one right, threaded inside to match the smaller metric threads and threaded on the outside with standard ISO threads. This allows the hub to use any size or combination of left and right drive freewheels available

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etard said:

I rather like the idea of left side drive right side pedal, but I am confused. On a flip flop hub both freewheel threads are cut in the same direction, and both are designed to be used on the right side (hence the name). So how does one go about using a freewheel on the left side that works with the rotation of the tire? OK, I understand that there are lock rings that the fixies use because they brake with the pedals and this force can loosen the cog, is this enough for our purposes?

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The common flip flop hub is not what you need.

Some double-sided hubs are made to be driven from either side. On the left side they have left-hand threads for left-hand freewheels. These hubs are sometimes referred to as "bi-drive" or "dual-drive". They are no longer made for BMX use but are still available as old stock. Double-sided hubs for use on motorised bikes are made by Staton Inc. and Grubee.

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=9342&start=70

Edit: Ooops, didn't read second page before replying

I didn't mean to start a huge debate about the topic of this thread. lol It just started to go in the direction of a CVT, which is just fine. It is all about different ideas here.

Mud -

I haven't tried to cut threads in a cassette hub, but it does make sense they are hardened. Have you tried one? That leaves the uniglide hub option. If you use a cassette hub, then you do not have to change the wheel at all. If you are worried about the strength, then go with a DH wheel and you will be sweet as.

I agree the stacked freewheels is not the best option and has draw backs. Definitely hard to get apart as you said. It is just another way to set up a double right side drive. I prefer the cassette option myself.

As for getting the rear wheel off, having a chain on both sides of the hub makes it difficult to get a wheel out of horizontal dropouts. Vertical dropouts wouldn't be so bad, but I can see trying to get both chains on and the wheel in the dropouts a challenge as the sun goes down and the mozzies are eating you up on the side of the road after changing a flat tire.

Matt -

I was wondering how you set up the rear wheel. I couldn't tell if you had 2 freewheels or 2 sprockets attached to 1 freewheel. Looks very clean, I like the parallel chains and can't wait to see how mine looks.

Anyway, keep it up, I love all the ideas being thrown around.

FM

I haven't tried to cut threads in a cassette hub, but it does make sense they are hardened. Have you tried one?

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this was my first plan for a drive system, so I bought a cheap cassette hub wheel and a die to thread it. I had a way to align the wheel to keep the threads straight, but the cassette body just spun in the die. not knowing any better I just put more pressure on the wheel and turned it but it still just spun. I ended up scuffing the freehub real bad and ruining the die.

I have a stacked freewheel drive system on my current bike and am putting left side drive on my next bike. both systems are actually quite good, but do have their nuances.
If you could get someone with a thread grinder or maybe a lathe with a carbide tool to thread a cassette body (freehub?) you could have 2 freewheels plus the freehub for 3 freewheelin action

I also like the idea of putting a gear on a left side brake mount and using a freewheel adapter on the output shaft, that way the freewheel can be put up higher and covered easier for dirt protection. I may try this on my next build

whats a mozzie?

Good to hear some first hand experience with cutting threads in a cassette body. I guess I won't order a die just yet. I might have to stock pile uniglide hubs as they already have threads on the outside.

I wouldn't want to give up my rear disc brake if I had one, but a left hand drive does seem an elegant solution as well. Not too much fuss with machining parts.

Mozzie: Kiwi for small biting insect, usually a mosquito.

FM

Here are a couple high rez pics of my rear drive.

Matt

Here is a shot of my dual chain drive.

Bubba

I'm finally scrounging around for parts to mount the rear sprocket and found this guy:



http://web.tampabay.rr.com/bikeparts/sprocket_adapter.htm

He said you need a cylindrical hub (not football shape) and he will be machining custom dished sprockets for cheap too! $28 for that clamp is insanely cheap! He even gets your hub diameter and custom machines it. I told him he needed to come over into the light from the dark side of ICE. :wink:

Thread the other end of those three posts and use two plates to mount to the sides of Matt's drive and off you go! Just tell him the diameter of your frame tubing.

wow that is a sick adapter! great idea as long as its tight, there is alot of torque on that adapter and if it slips, goodbye spokes .