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Old 03-05-09, 09:29 PM   #1
maag himself
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Quad Bike

Hi all,

After making a tandem bike a few years back, I decided to fab something else up.

This time I was going after something with four wheels, and recumbent (almost) style seating. After sorta designing it and planning it out, I thought about making it a two seater. Then somewhere in the process I decided I might as well go for 4 seats, which brings me to a small hiccup with the drive system. I haven't been able to find too much about this online.

Here is a simple layout of basically what I'm trying do.



Yea, I have alot of chains, but I don't know how else to work around that without seriously complicating things. Any suggestions? Keep in mind I'm trying to keep a solid rear axle. I was also considering a suspension, but I'm not quite sure how that's gonna work out..
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Old 03-05-09, 10:34 PM   #2
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Maybe put two sprockets on the rear axle, and then hook up the chains like two tandems side by side?

With a solid rear axle, it would help to have some way for the wheels to turn at different speeds when you turn.

Putting the power of 4 people into that one final drive chain could cause problems.

They make commercial 4-wheelers with 4 pedaling positions. I'm not sure how they are hooked up, though. Google "surreys" to find them.
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Old 03-05-09, 11:03 PM   #3
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Running it like two tandems side by side is an idea. Although the solid rear axle could hinder cornering, I'd like to keep it solid due to maintain some sort of traction. I've seen one home made Quadracycle, but it appeared to have the left/right wheels completely independent. I'm not quite sure yet how to make them spin at different speeds during cornering, which would require some sort of differential.

I've looked for a few hours for Quadracycles, but whatever I did find didn't really shed any light on the design.
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Old 03-06-09, 05:52 PM   #4
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free wheels at each rear wheel would accomplish this. Both wheels would be driven in turns but the outside wheel would be allowed to freewheel faster.

Would this be a SS? If so, you could just double up that final drive chain.
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Old 03-06-09, 06:55 PM   #5
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try this differential but it cost $$ http://www.utahtrikes.com/PRODINFO-T...rsion_Kit.html
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Old 03-07-09, 01:40 AM   #6
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Ask this question on the forum at atomiczombie.com

I think I've mentioned the place on here before, so I have to be careful, or folks at BF will think I'm getting kickbacks from AZ ore something. (I'm not by the way)

There's some experienced builders there, and plenty of garage hacker types.

Personally, I'd let two riders drive each back wheel I think - solid axle would be bad.
There's plans for a side by side trike there, you could stretch it longer for 4 maybe.
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Old 03-07-09, 08:46 AM   #7
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Ask this question on the forum at atomiczombie.com

I think I've mentioned the place on here before, so I have to be careful, or folks at BF will think I'm getting kickbacks from AZ ore something. (I'm not by the way)

There's some experienced builders there, and plenty of garage hacker types.

Personally, I'd let two riders drive each back wheel I think - solid axle would be bad.
There's plans for a side by side trike there, you could stretch it longer for 4 maybe.
+1

I'm pretty sure this is the simplest and best way to go. Basically, 2 separate tandem drives.

The posi idea is interesting, but it is heavy and does consume some power in addition to being expensive.

I think you would retain a solid axle for a simple and light rear end, but, each side would spin independently.
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Old 03-07-09, 02:13 PM   #8
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I googled some surreys earlier. I'm not sure if they're all the same, but the ones I could see, it looked like they had the two riders on each side driving a single rear wheel, with a single-speed-tandem arrangement.
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Old 03-07-09, 04:33 PM   #9
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The two tandem side by side would simplify things, but I think a little bit of understeer or wheel hop would be more desireable than having the independant drives in the rear.

Where I live, I'll probably be using it off road as it's pretty rural around here and theres a good amount of dirt/gravel/grass. I need all the traction I canget. Wouldn't traction be an issue with one rider as the opposite side would have no power? I'm not quite sure what would come of things, but something tells me 3 riders would also cause a little undesired operation with twice as much power on one wheel?

This sort of thing is aching for gears which would be very complicated if not near pretty near impossible with the two separate tandem drives.
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Old 03-07-09, 09:56 PM   #10
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plenty of trikes for one rider are built with one wheel drive on the rear, without traction issues. Unless your in a mud bog, or ice, I don't think traction would be an issue.
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Old 03-08-09, 12:56 AM   #11
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Those surreys are mainly intended for rental at tourist places. You take the family, ride down the bike trail a bit, laugh, have fun, get tired, and take it back. I remember one place I looked at, they rented bicycles by the day and surreys by the hour. Meaning, they're really not intended to be the functional equivalent of bicycles.

One of the surreys I looked at, used an internally geared hub on each wheel. They also had an option using a single internally geared hub, but I'm not sure how that was chained up. They might have just had one wheel driving in that case, too.
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Old 03-08-09, 07:59 AM   #12
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Originally Posted by maag himself View Post
The two tandem side by side would simplify things, but I think a little bit of understeer or wheel hop would be more desireable than having the independant drives in the rear.

Where I live, I'll probably be using it off road as it's pretty rural around here and theres a good amount of dirt/gravel/grass. I need all the traction I canget. Wouldn't traction be an issue with one rider as the opposite side would have no power? I'm not quite sure what would come of things, but something tells me 3 riders would also cause a little undesired operation with twice as much power on one wheel?

This sort of thing is aching for gears which would be very complicated if not near pretty near impossible with the two separate tandem drives.

I think you just answered your own delema. ( The whole, I'm in RWD car with tons of horse power, attempting going up a snowy hill with an open-pin diff... )

Exept, here I think you are assuming that one or a pair ( side ) of riders, can spin the rear wheel vs. the other pair ... ( maybe put the straong pair both in the back not one side. ) but I think, under the 4 peoples weight & the weight of the whole rig, the whole thing would just stall-out ... even uphill in gravel. Its NOT the same weight-to-power ratio as a single bike & rider climbing, out-of-the-saddle, un-weighting the rear wheel, uphill in gravel.

... If the "weaker" pair has the advantage of gearing, than it doesnt really need to be, that solid rear axle thing you have cooked up ...

Just take two geared tandems, and a bunch of tubing & weld the ****os up .

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Last edited by martinus; 03-08-09 at 09:20 AM.
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Old 03-08-09, 08:29 AM   #13
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the extra push or understeer of a solid rear axle on a loose surface would certainly provide an entertainment factor on fast downhills.
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Old 03-08-09, 09:08 AM   #14
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Quote:
Originally Posted by trekker pete View Post
the extra push or understeer of a solid rear axle on a loose surface would certainly provide an entertainment factor on fast downhills.

* cough * * cough * thats oversteer.

Entertaining yes, if theres enough power ... I think, its still do-able with out the solid axle. IMO.


"Push" or "understeer", is when you turn the steering wheel ( too much, to the point where the front tires loose traction . ) in either FWD or RWD car and you just keep going straight ... easly fixable, in RWD. Just feed it more gas.


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Old 03-08-09, 09:53 AM   #15
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I do understand the difference between under and over steer.

Having a locked rear diff generally will produce understeer unless, as you say, copious amounts of power are added. More power than 4 tdf riders could produce.

I will give you that the entertainment value of oversteer is higher than understeer. Infact understeer's entertainment type is better known as terror.

The only type of oversteer such a beast could muster would be brake induced. So if he does go with the locked rear, I would recommend a good strong set of rear binders to do away with unwanted doses of understeer.
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Old 03-08-09, 05:52 PM   #16
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... OR ...

Momentum or inertia induced :



I swear both my hands are wayyyyyy to busy "working" the steering wheel. The ratio on an econo car car is stupid slow ... I know its not the fast way around, but its hard to heat up 9 inch wide rear tireas on FWD car.

( * note * The 2 black lines, from the front tires. )


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Old 03-12-09, 08:43 AM   #17
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Freewheel the rear as suggested? Simple-ish. And for your final drive off one chain, hollow schedule 40 pipe (heavy but four people pedaling...) with a motorcycle front drive sprocket and motorcycle chain for that bit of driveline.

Maybe a good idea...?
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