Engineering genius requested

[marcmax]

Here is a YouTube clip of an annual race in Macon, GA where my brother lives.

http://www.youtube.com/watch?v=8fspZ6MuV-0

He wants to win it and has asked me to come up with a winning vehicle. This is an adults only competition (over 18 only to enter) and most entries are for fun but some (my brother included) take it serious.

There are no length, width, height or weight restrictions. The only requirements are a minimum of 3 wheels in contact with the ground, some form of steering (no weight shifting like a skateboard) and some form of braking (no Fred Flintstone feet on the ground). Other than that anything goes.

I have spent years building traditional push bike frames as well as recumbent bikes. I know the main things to consider are wheel resistance, bearing friction and aerodynamics.

Time for the thinking caps. How about some engineering marvels to shave a second or two off a timed run.

[Rob Valdez 79 R65]

Definitely looks like a good time!

Sorry I am not an engineering genius.  Not even half-genius, I don't think.

[MR.E]

is it a drag race or will he have to navigate bends/ corners??

[marcmax]

It is a drag race with one small curve just to make it interesting. It is run on an actual city street that is closed for the event so there are holes and bumps to be avoided.

[MR.E]

think i'd do the F1 style car on skinny wheels.
OR
street luge on 4 wheels
Laying the pilot down head first

are you going to have the wheels sharing an axle or 4 independent mountings, for drag?
You could run the steering on a foot board for the front wheels which would mean you wouldn't need a front axle either.

[Bengt_Phorqs]

Think Big Wheel but use skinny bicycle tires and caliper brakes.  Three wheels = less rolling resistance, low profile for less drag.  A couple of old bicycles should provide enough parts to weld it up.

[marcmax]

I think I have settled on a very flat, wide design with the driver feet first and almost flat on his back. 8" skinny wheels completely enclosed within the body for aerodynamics as well as an acrylic bubble over the cockpit.

Similar to this racing go-cart.

[Johnster]

I agree that skinny tires and a lay-down format are best.
  I'd consider a 'sidecar' -like layout- with the side wheel halfway between the front and rear wheels - this lets you focus on something with a  bicycle-like frontal area (remember that air resistance increases with the square of speed and the CUBE of frontal area).
  Its possible that a 'sidecar' wheel layout is worse than a "Can-Am" - layout (2 wheels in front, 1 in back), or a "Trike" layout (2 in back, 1 wheel up front), but since you have to engineer some kind of steering and brakes, they need to be as low-profile as possible.

Lightest bicycle wheels you can afford - hardcore bike racers will buy carbon fiber wheels with wide spokes, If you can only afford traditional spokes, cover them with plastic/paper/aluminum foil(?) so that they become flat disks.  Maybe remove every other spoke for weight savings (?)

If using bike wheels - pull the hubs, and replace the grease in there with a light weight oil (WD40 ?).  Replace steel/Iron nuts and bolts with Aluminum or plastic ones.

I'm not an engineering genius - but these ideas are up for discussion.
-John

[marcmax]

Bicycle wheels have several disadvantages. A decent lightweight wheel has a diameter of roughly 700cm. The smallest lightweight wheel readily available is 20" but the smaller the diameter the wider the wheel becomes. Bicycle wheels don't have a lot of lateral support and tend to fold when a side load is applied. On a bicycle (or motorcycle) the wheel always leans with a turn so the force is still in line with the vertical dimension of the wheel. On a 3 or 4 wheel vehicle there is a lot of side loading even in a small turn.

I have been looking at some cast aluminum wheels, similar to our R65's just smaller (8"-12"). They are used as casters on wheelchairs and hospital gurneys and have a narrow hard rubber tire. With precision bearings they should roll just fine. Not as comfortable as pneumatic tires but the winning time on this course is 11 seconds so a little discomfort is fine with me.

[wa1udg]

We have a sailboat race every year where you have to BUILD the boat on the shore and launch it before the race starts.  Oil drums, styrofoam, bathtubs, ANYTHING but an existing boat.  

[marcmax]

Now THAT sounds like fun!