Project Kalamazoo

[gfish]

I've been developing/obsessing over an idea for next year's Burning Man, based around the image of an old 19th century railroad handcar. I have decided to call it Project Kalamazoo, as Wikipedia tells me that is how such devices are known in Australia. Ideally it would carry the two drivers plus up to another four people sitting on the edges. I really like the idea of driving around, picking up random people, letting them swap out on the secondary drive position. That would be really fun, and I'm sure it would catch a lot of attention. I'd definitely need a kind of rough navvy outfit to go with it.

This weekend I got kind of bored and took the opportunity to play with Googles SketchUp and 3D Warehouse. This is the rough design I've been thinking of, with lots of smaller details (like support brackets) left out.



The front wheels are freely rotating caster-style (not shown). The hand pump turns the craftshaft which feeds into a small ATV differential. That turns two sprockets which drive the rear tires. Why add the complication/expense of a differential? Because the drive tires have independent brakes on them, which are also used for steering. This allows a very simple interface which can be operated while still pumping. Also, I like the quirkiness of it. Should be pretty nimble.

The connecting rod attachment point, crankshaft offset and gear ratios are just randomly chosen for this rendering. There are just too many question marks to try to decide upon those now. Once I have the platform built I can figure out just how much torque will be needed, and what pumping range of motion and force is comfortable. It doesn't have to go very fast, after all. Slow and steady is fine once it gets going, as long as pumping isn't too much work. I don't think it will need adjustable gears, but if so it isn't the end of the world. I'll probably be cutting up a pair of old bikes for parts anyway.

I can't start on this until I'm back in Seattle, obviously. And I'm going to want to get my forge back for some of it -- smithing the brackets by hand will be fun and a nice touch, visually. Most of the parts will be pretty cheap and easy. Standard wood floor design, iron pipe for the pump and connecting rod. One important design limitation is that it needs to be able to break down into pieces that can (comfortably!) fit in my car. Hopefully the longitudinal floor joists can be single pieces. They're 3 meters in this rendering, and the driver's mass is dangerously close to the rear axle. Wouldn't want to flip it while driving solo...

Comments

[dymaxion.livejournal.com]

Why not have the front wheels actively steered by rotating the hand pump pillar? Seems more elegant than brake-steering. On the playa, you can almost certainly get away with single-speed, I think.

[gfish.livejournal.com]

I considered that, but decided against it. I'm going to need brakes anyway, so I might as well use them. Making the pillar rotate would add a lot of complication and specialized machining. What really clinched it for me was the pain of coordinating every course correction with the person in the secondary drive position, who would also have to rotate. At the cost of an ATV differential, one extra chain drive linkage and a U-joint in the con-rod, I really think this is easier.

[dymaxion.livejournal.com]

Hrm. So, pump cars are normally fixies -- you brake them by simply slowing down the speed at which the handle moves; much simpler. Alternately, instead of having the whole pillar move, add a joint to the handle so that while the two sides are still fixed for the pumping motion, one side can swing back and forth, and use cable steering.

If you did actually need brakes, I think you'd be right, but I don't think you do, and I think this would end up looking a lot closer to an actual pumpcar.

[gfish.livejournal.com]

I'm not going to drive something that massive (and blunt) through crowds without brakes. No way.

[dymaxion.livejournal.com]

Hey, if it works for a messenger on a fixie coming down a hill at 25mph with their feet off the pedals... er, hrm.

Could still decouple steering and braking, but yeah, that seems sensible.

[loree.livejournal.com]

Is the steering mechanism not pictured, or am I (or you) missing something?

[gfish.livejournal.com]

The (current) idea is that it is steered through differential braking of the rear wheels. Which is not pictured.

[randomdreams.livejournal.com]

I'm thinking about a mechanism where you use a variable-length crank and some sprague clutches, so that when the pump handle is moving down on the back it's driving the right wheel, and on the front, the left wheel. Either do it with a mechanism like a helicopter's swashplate, so you'd have a separate input but the pump handles would always have the same travel, or have the separate input control the pump handle wobble distance.

Tricky but it'd make for an interesting drive.

[peteralway.livejournal.com]

For the record, I was born in Kalamazoo.

And oddly, when my family still lived in Kalamazoo, before they moved out to the suburbs, and before I was born, I am told that they owned a kiddie version of just such a device. Alas I have no recollection of it.

[gfish.livejournal.com]

Eeeee, that sounds great. I haven't found any pictures of such a device. I wonder if it was made by the Kalamazoo Manufacturing Company?

[bigbumble.livejournal.com]

The device Peter refers to is known as an "Irish Mail". There is an updated version of it sold at this website http://www.champiot.com/
The site has videos and everything. You may pick up some helpful hints there.

[randomdreams.livejournal.com]

Irish Mails show up at antique malls all the time. All the ones I've seen are single-person kiddy toys mostly intended to drive young children crazy because they rely on the cart's inertia and young kids don't get that it requires regularly periodic pumping, just as swings do. (Ever tried to teach a kid to swing? Lordy...)

[ilmarinen.livejournal.com]

Huh, most kids learn that, I thought. Pumping a swing that is.

[ionan.livejournal.com]

"I'd definitely need a kind of rough navvy outfit to go with it.
"

You probably know this one already, but-
Gentlemen's Emporium (http://www.gentlemansemporium.com/gentlemans.php), specifically, this (http://www.gentlemansemporium.com/store/vict_mens_14.php).

[gfish.livejournal.com]

Eheehee, that would be perfect.

[bakeme.livejournal.com]

how would you brake? with your feet, presumably? what kind of assemblature?

[randomdreams.livejournal.com]

Could put mountain bike brake levers on the pump handles, activating standard brakes on the rims, or for extra credit (and ease in putting on massive balloon tires that'd handle the playa) disc brakes.

[bakeme.livejournal.com]

also, my friends and i having been vainly dreaming of having some kind of art car for burning man next year. this thing would be awesome.

[irgth.livejournal.com]

I suspect (based on vague fourth hand knowledge of the difficulties engineers have had getting brake assisted steering to work on race cars) that the differential/braking/steering would be very time intensive to get right.

A possible alternative would be to have two hand pumps, each driving one wheel.

Another alternative, especially since cannibalized bikes are going to be a major source of components, would be to change gears to turn (difference in gear ratios for left/right wheels determining turning circle). This would also allow for programming the path of the vehicle (automated gear changes based on distance traveled and/or GPS).

[randomdreams.livejournal.com]

I really like the idea of differential drives to the wheels.

Using brake-steering is just so painful from an efficiency standpoint.

[gfish.livejournal.com]

Simplicity trumps efficiency here, I'm afraid. The less custom machining I'm doing, the better. And cheaper. And more reliable in a very hostile environment. Doing a differential drive would be a nightmare -- and I'd still need brakes!

[bigbumble.livejournal.com]

I am very skeptical of turning by braking. My recumbent tricycle (see userpic) has one wheel drive on the left rear wheel. There is very little or no steering effect because of it. If you have rigidly aligned wheels I am confident you will have little or no turning ability by breaking. I suggest you test it first on an Lego or Erector Set type model before you start building.

[gfish.livejournal.com]

The rear wheels will be driven through a differential, so they aren't mechanically linked. If you brake one while letting the other one continue to rotate (or continue to power it, even better), the vehicle will rotate about it, no worries there. It's the same way that wheelie cars steer.

[zzyzx-xyzzy.livejournal.com]

It seems like it'd be hard to develop the torque for turning this way. Think of turning from a stop. If you lock one of the rear wheels, you effectively double the gear ratio to drive the other wheel, AND you're trying to rotate the vehicle around the single worst point as far as its angular momentum goes (if it's longer than it is wide like your sketch)

[gfish.livejournal.com]

Yeah, there is a reason you don't see many devices like this. If I wanted ruthlessly practical I'd buy a golf cart. What fun is that?

[bigbumble.livejournal.com]

Wheelie cars don't have their front wheels on the ground when they steer that way. You would have to pop a wheelie every time you wanted to turn. (Would be fun to watch though!)

[bigbumble.livejournal.com]

As I review the fine print I see you mention casters for the front wheels. So turning is no longer the issue, going straight will be!

[gfish.livejournal.com]

My intuition is that won't be a problem. Luckily the difference between front wheel drive and rear wheel drive is simply which side of the pump I put the brake levers, so I can switch it trivially if need be. I'd rather it be rear wheel if possible, so the driver has better visibility when turning.

[bigbumble.livejournal.com]

A pair of large caster wheels can be turned in tandem using a bar linkage, off center of the caster pivots, between the wheel mounts. Only a linear motion to move the bar left-right is needed for turning. The control could be nearly identical to what you had in mind for brake steering.

[ilmarinen.livejournal.com]

This sounds like promise. I don't thin Fish could get enough motion out of a cable-operated lever on the pump to actually steer something though. Maybe a foot-operated steering tiller?

[zzyzx-xyzzy.livejournal.com]

How about cable-actuated steering? You could have brake levers on your handlebars that pull the front casters around.

[caladri.livejournal.com]

I think you should make it magenta (http://docs.FreeBSD.org/cgi/mid.cgi?18238.938873650.1).

[keystricken.livejournal.com]

This is going to be a smash hit. I'm looking forward to hitching a ride myself.

By the way, you're going to see a suspiciously derivative robot on the website in a couple days...

[gfish.livejournal.com]

Hee! I'll keep an eye out for that.

[ilmarinen.livejournal.com]

Fish, have you seen the build log for the original Contraption? (Originally pump powered, then they added that little hit-n-miss engine last year.) It's on Tribes.net. I'll see if I can pull it up.

-B.

[ilmarinen.livejournal.com]

tribe.net

[ilmarinen.livejournal.com]

http://eplaya.burningman.com/viewtopic.php?t=19038
http://eplaya.burningman.com/viewtopic.php?t=22962

(was wrong, eplaya, not tribe.net)

Quote:
"Incidentally, when I broke apart the guides that held the axles for the discs, I found that they contained wood bearings. "

He used a few big old pieces of farm equipment as the base.