I have been playing with k'nex for a while now and thought to myself, this would be better if it moved, so instead of going out and buying a knex motor piece, i made one myself.

What you will need:

1 Motor (mine came out of an old printer)
1 drinking straw
1 of those wide blue spacer things that you find in the the mini knex
1 pen (more specifically the ink cartridge)
4-8 yellow knex peices
4-8 green knex peices
tape (i just used electrical, but on previous version i used masking)
Model's glue (or super glue epoxy etc)
1 knex wheel without the rubber piece (you will be gluing this to the motor)
6 white pieces

Step 1: Wheel Mount Part 1

For this, we are assuming that you have already pulled the gear/what-not that is already on the motor off, if not, please do so now, I'll wait for you.

*insert jeopardy music here*

Done? cool, now for this step, take your ink cartidge and push the end of it over the motor shaft, try to get it as far down as you can. Next clip off the excess and toss it into your "for later parts" bin. I had a slight issue with it not going as far on as i wanted it, so i took the scissors (not really the safest tool for this) and tapped it further on. next take a little tape (i used electrical on this one) and wrap only one layer on it, basically enough to cover the pen peice.

Step 2: That Little Blue Piece

now that you have the tape on the pen piece, pop the little blue piece over the pen piece and tape, If you want dab a little modeler's glue on there to give it a firmer grasp on the situation.

Step 3: The Straw

next take the straw and cut it to length of the blue thing. Put a dab of the modeler's glue on the blue thing and slide the piece of straw over it.

Step 4: Wheel Time

Now that you have the straw in place, and let the glue set some, place the wheel over the straw piece, if you are lucky it will be a snug fit and all you have to do is add a dab of modeler's glue to it to secure it into place, if you are like me and have a wider whole than the straw is thick, take another piece of electrical tape and wrap only 1 layer over the straw, then feed the wheel back over the straw.

Step 5: Now for the Mounting Bracket

For this you are going to need two of the yellow knex bar pieces, 4-8 of the yellow knex connector pieces, 4-8 of the green knex connector pieces. and 6 of the white bar pieces ( assuming that you have the same sized motor as mine)

First you are going to need the Yellow connection pieces, 2 white bar pieces, and the 2 yellow bar pieces.

Ok, to make this, it is hard for me to discribe, but you take the yellow connection pieces and lay them with the spikes pointing upwards, take the first two and set them next to each other so that they are parallel to each other, and set the next two behind them in the same way, now take the white bars, and connect them to the ends that are in the middle. then on the outside take the yellow bars and pop them into place... for a better understanding take a look at my horrible picture, the yellow rectangles are the yellow connection pieces, the red rectangles are the white bars, and the blue rectangles are the yellow bars. mind you this is with the spikey parts facing up on the yellow connections.

Make this again, but leave out the yellow bars

Now on the one with the yellow bars, place the motor so that the wheel over hangs the yellow connection pieces, take a piece of tape and loop it around the yellow bar, and run it over the motor going around the second yellow bar. I just went over it a few times to make sure that it was held down tight. Now, take the white bars and slide them into the top center pieces of the yellow connections pieces, and mount the 2nd half of it to the top of the white bars. With that, you should be all done.

now to transfer the power, I just use rubber bands, make sure that they are taught, but not stretched, I have found that this motor does not like to run with stretched rubber bands, but i have used really big (as in long) rubber bands with no issues. This motor was originally built to be the source of power for a paddle wheel boat made out of knex and the cover to my knex container, which worked really nicely. It was later used to make a 4 wheeled drive vehilce, but didn't have the umph to make it over many obsitcales, but did move pretty quickly on a flat surface, and more recentally was used in an attempt to make an O scale Knex engine to run around my track, the placement of the motor wouldn't allow me to balance it quite right, so i gave up on that one. Hope you enjoyed my instructable, and was able to follow the last part.