Concept Analysis: In Line Cargo Trike, Tandem Axle Rear Drive?
Okay, Iíve had this thought for a while now and just found this forum a couple days ago and thought Iíd ask for some thoughts critical analysis on this idea:
Basically, take an older 90ís era name brand steel frame mountain bike and do some major re-arranging of the tail end. Two smaller size BMX free style heavy duty wheels mounted low with a cargo rack built around them. Both rear wheels driven by the pedals with the forward of the two wheels having a gear spool that is one gear more then the shifter/derailer is set-up for (example: 7 gear spool with 6 gear shifter/drailer) with the same spool on the rear wheel and a slave chain on the extra (7th in the example) gear running back to the same gear on the second drive wheel. 2x3 drive traction with two wheels in the rear to provide two axles to bear the cargo load instead of just one. Not to mention the uniqueness factor.
What do you guys who have experience chopping and splicing think of the concept? Comments, suggestions, critical analysis, etc . . .
I think you could make it work. I do like your idea about the derailer action, you would have to limit it to a 5 speed because with a chain on the 7th gear a chain wont fit on the 6th.
Or you could build off a Fixed/Free Flip flop hub and have all your gears on one side and use the fixed side for your slave chain, add horizontal drops for the rear wheel to tension the chain.
I can see in your pic that the two rears mount to a triangle and then that mounts to the frame, good thinking for bumps and such.
Then the only issue would be tight turns, one of the rears would have to skid, (like a 4x4 truck making tight turns). How tight would the turn have to be I wonder.
I say you should build it for sure.
It should be possible to build it (especially if you only try to drive the center wheel) but I think it would have issues with poor steering, because the two rear wheels are going to scrub laterally when turning. -That is, if it will even turn at all....
If I had to build a cargo bike like this for someone and wanted it to NEVER fail, I would use a single small car or motorcycle wheel & tire for the back end.
I remember seeing a 3wheel in-line cargo bicyle a looooooong time ago, but the third wheel was just a front fork in a headstock trailing the drive wheel.
check these out:
Somehow you gotta be able to turn.
As a proof of concept go get 2 pcs of perforated angle stock(HomeDepot, Lowes, L HDW), long enough to go from trailing 3rd wheel axle bolts to rear axle bolts or even chainstays of drive bike, clamp it together with U-bolts and see if you can ride it. You might want to borrow some bikes and another front wheel from someone who wont miss them, JIC.
What happens when you go over a speed bump?
or in a less extreme example, when the ground is not a pefectly smooth plane and not all 3 wheels can touch at the same time? ie, curbs, potholes, hills, -pretty much every place outside of an airport tarmac
is the entire cargo section with the two wheels supposed to pivot vertically to account for such situations? what would such a mechanism do to your weight distrubution? how would the drivetrain work around it?
I assumed the two wheels were mounted on a bogey. If that were the case, then the pair of rear wheels has a common pivot point, allowing them to separately ride up & down small obstructions.
Originally Posted by xenologer
Here is an example of tank treads using them (rather common)-
It still leaves the steering problem though.
If they are to be mounted on a bogey, why not take the bogey's pivot point, replace that with a single axel for one heavy built wheel? From the cargo's perspective the weight distribution would be identical (all the support at the one point). and this simplifies the drivetrain.
Originally Posted by Doug5150