I have been asked whether or not a properly balanced 3D printed PLA spring powered vehicle could pull a wheelie and, well, Wheelie is the result, as it is indeed a 3D printed, PLA powered, wheelie pulling vehicle in dragster form.
Wheelie, like it's predecessor (PLA Spring Motor, Rolling Chassis, is printed entirely in PLA, spring and all, requiring no batteries, bearings, screws, power supply, electric or drill motors to operate. With a beefier spring and fatter drive wheels, Wheelie will run as far if not farther than PLA Spring Motor, Rolling Chassis while pulling a wheelie.
(I had not yet lubricated Wheelie when this video was made and overwound the spring, thus a little "nudge" was required to break the surface tension :) ). The video also shows where the PLA spring torque becomes greatest, at the point Wheelie pulls a wheelie.
SPOILER ALERT: As designed, Wheelie should be fairly close to balanced. But just in case yours is not, the spoilers are "ballast tanks" that allow balancing of Wheelie for the performance curve of your choice by adding weight to either end of Wheelie. If your Wheelie does not wheelie, then add ballast to the rear spoiler. If your Wheelie wheelies too much (as did mine), then add ballast to the front spoiler. My wheelie balanced to my liking using just a few BBs (as in those used in a bb gun) in the front spoiler for ballast, but small nuts (2-56), pellet gun pellets, fine sand, etc. can also be used. Once balanced, place a small square of electrical tape or equivalent over the holes, then turn the spoilers over to hide the tape.
You may also wish to print johann517's gorgeous Wheels Add On Pack located here:http://www.thingiverse.com/thing:448354. I haven't had time to print and test them yet, but with Wheelie's beefier spring, they should turn them quite well.
As a final note, use safety glasses when operating Wheelie. While I've operated the mechanism well over a hundred times without a failure, I always recommend erring on the side of caution as the spring could snap and send pieces flying where they shouldn't be flying, and that's never a good thing.
Designed using Sketchup 8, and printed in PLA on a Makerbot Replicator 2 using Makerware 22.214.171.124.