pschirm

I am a senior in Mechanical Engineering at Iowa State University and our final project is to design a bike chariot that can be pulled behind another bike where the user can still pedal to help travel. We are looking into using a Shimano Nexus hub, or similar automatic hub to drive a rear axle assembly purchased from a trike manufacturer. One of the major issues we are looking into is how to recreate a bottom bracket so we can mount our crankset on the front. Is there somewhere that we could get some dimensions on the bottom bracket so we can add it to the front of our bike?

The bike is for a disabled person who is partially paralyzed (he has mobility, but it is really shaky). The goal of the project is to have it completely designed and fabricated so he can ride in RAGBRAI across the state of Iowa this year. They also want it to double as a training device that he can use in the off season. We are open to design suggestions or any links to existing chariots etc. that may help us out in this process.

Thanks in advance!!

dabac

If it was me I'd go for some sort of tandem instead, perhaps a tandem trike. I'd be very wary about hitting any kind of descent with something as heavy as another person in what's basically a bike trailer attached to my bike. With a bit of ingenuity and liberal use of freewheels you should be able to design a drive train that's allow the disabled person to assist to the best of his ability w/o having the pedals permanently tied in.

jsharr

I too think a tandem recumbent or tandewm trike would be the way to go.

https://www.greenspeed.com.au/gtt.html

Link to give you some ideas on design.

DiabloScott

Here's a Greenspeed in action:




Saw these guys on Mount Diablo a while ago - the older guy is the younger guy's dad. I'm not sure if the drivetrain is locked, requiring Dad to pedal at the same cadence as Son, but Son told me that Dad couldn't ride a regular bike because of physical limitations. Not hard to imagine someone doing RAGBRAI on one of these... probably already been done.

Not a very good project for an engineering class since the solution is already complete - but maybe you could figure out some customization for your subject's particular disabilities.

Retro Grouch 

Look up "ViewPoint" or it may be "Counterpoint".

It's a stoker-in-front tandem. The stoker has their own shifter so they can control their cadence independent of the captain.

Dan Burkhart 

Have a look at the 5th item down on this page.
https://www.freedomtrikenbike.ca/genesisbrand.html
Sorry, I don't have any better pitures of it, but the idea is pretty straight forward. It hitches to the seatpost of the lead bike, just like any trailabike.
The sizing of this particular unit is really only suitable for adolecents, but I see no reason why an adult size version shouldn't work.
I sold one of these to a family with a 13 year old daughter who has cerebral palsy, and they were very pleased with it.

masiman

Hase bikes makes something like you are describing, but as far as I know they are only for kids/small folks. Their custom options may allow for larger riders. You could get some ideas from their designs if you plan to pursue.

jccaclimber

Iowa State has a Human Powered Vehicles Team. They have built a couple decent recumbents including a very stable and easy to handle tandem two years ago. You should talk to them, they are pretty nice people. Also, you can buy bottom bracket shells, but I also advise against putting a fully grown adult in a trailer.

Edit: Link
https://www3.me.iastate.edu/asme/HPV/HPV_home.html

dabac

The easiest and probably cheapest way of getting a BB is to do some dumpster diving. Find an old bike with a gas pipe frame and a square taper crank. Let it get intimate with Mr. Hacksaw and within minutes you should have a BB in your hands.

On second thoughts: better get the BB disassembled first, then cut it out of the frame.

If this is too crude for you then do a search for frame building supplies and buy yourself an empty BB shell. You'd still have to get it threaded and reamed, which means paying for expensive tools or making friends with a good bike mechanic.

Metzinger

Check out this page.
https://www.geocities.com/aangepastfietsen/rolfiets.htm
I saw rigs like these on the pathways last summer.
Is there anything the Dutch haven't done on bikes?

And don't say the obvious, because you know they have.

2manybikes

This is probably as cheap as building one. They have an optional back rest (this one has it) and can be fitted with all sorts of extras. It works great for my friends disabled daughter. The full chain case is nice for a disabled rider. She has a lot of serious balance problems. She can't hold on with two hands or keep her feet in place without straps. The front bar folds.

If you start buying parts at retail this will probably be cheaper.


https://www.pedalcarsandretro.com/Cab...520.html#image

meb

The Hase Ketteweisell tandemizes by hooking one onto the back of another. There was a gather a couple of summers ago where they set a record by putting over 100 Kettweisells in a train.


https://www.velomobiling.com/gallery/...iKett.jpg.html

I've been told the Lepus does as well, but the rarer folding suspended Lepus is less displayed.

meb

The is a couple out of Princeton with one of the Greenspeed tandem that lets the stoker-a physically limitted person-take rests and pedal as possible. The stoker crankset (in back) drives the captain crankset up front. The captain can't rest-I believe the drivetrain can be configured inversely though.

meb

Here is Hase similar model:
https://www.hase-spezialraeder.de/2-1...aktuelles.html

jccaclimber

Nova Cycles can sell you prethreaded bb shells, although I usually just chop up $5 garage sale bikes.

Jeff Wills

Do you want the dimensions of the bottom bracket shell so you can weld it into your frame? You should try the framebuilders' forum, but there's commercial suppliers around. Nova Cycle Supply is a good one: https://www.novacycles.com/catalog/index.php?cPath=2

The vast majority of bottom bracket shells are 68mm wide, 38mm diameter, threaded 1.37" x 24tpi (right thread on the left side, left thread on the right side). It'll be be much faster, easier, and cheaper to buy a commercial one than try to make one yourself.

Here's more frame parts suppliers:
https://www.phred.org/~josh/build/suppliers.html

BTW: it sounds like you're trying to build a Lightfoot Trailer Trike:
https://www.lightfootcycles.com/trailertrike.htm

dabac

Well. at least they're honest: "It is very possible for a heavily loaded Trailer Trike to push the tow vehicle into a "jackknife" during an emergency stop"

It looks nice for a sedate ride, but if it was me I'd very much prefer a "proper" tandem, trike or not.

pschirm

I agree that the tandem would be the best possible solution to this, but one of our constraints is that this chariot has to hook up to the patient's nurse's bike. So that put a big constraint on us just constructing a tandem that anyone could ride.

Thanks for the input everyone! This has been a great help!

2manybikes

the one I posted is about $260.

dabac

In that case I strongly recommend that you put some sort of brake activation device in the trailer hitch.