Linear distance

I've found a few topics discussing the use of rotary encoders to calculate linear distance traveled, but I'm looking for other ideas that may be better.

My project is this; I built an r/c truck pull sled and currently to measure distance I use a tape measure. To up the cool factor I'm thinking about using an encoder to calculate the distance traveled and display it on an LED screen mounted to the sled. Only 2 ways I can think of to do this, 1 is to use a belt or something similar to use the axle used to move the weight box to also rotate the encoder. The other is to try to mount a small rubber wheel directly to the encoder and have it roll along the top or side of the sled to do the same thing.

Actually just thought of another method. What if I try to mount a spool of string onto the encoders shaft and attach it to the weight box? Would I need to make a spool that prevents the string from winding up on itself to be able to get accurate results? Looking to get an accuracy of .1". Thinking that one of the 200rpp encoders from sparkfun would work and I would need to make the drum spring loaded so the spool rewinds when I move the weight box back.

Now that I've explained what I'm trying to accomplish here are my questions.

Will a rotary encoder be my best option for this project? Will there be any problems using the encoder from sparkfun (I don't understand this grey signal stuff yet, but I'm looking for info on it)? Is it possible to use a momentary contact button to reset the counter in my UNO R3 and when it does to change the display back to zero? The weight box moves roughly 24" (don't remember exactly since I built it 2yrs ago) when the sled travels 30', and the 1st 10-15 feet usually only takes a couple of seconds would I see any counting problems with the encoder? To add more cool factor will I be able to turn a light on when the sled hits full pull? And possibly turn another light on when the sled gets to 25'? Eventually I want to put a limit switch on the sled so that when the sled hits full pull it hits the switch my UNO will trigger an actuator (I'll link to what I'm thinking of using on sparkfun when I get to my laptop) to trip a quick release that will allow the rear of the sled to come off ground so the dragging of drive tires don't induce more drag. Will it be possible to do this as well. I use my UNO on anther project, so is there a cheaper, smaller controller I can do all of this stuff with instead of my UNO?

Thank for any help.

banshee1a: My project is this; I built an r/c truck pull sled and currently to measure distance I use a tape measure. To up the cool factor I'm thinking about using an encoder to calculate the distance traveled and display it on an LED screen mounted to the sled.

Buy one ?

http://www.ebay.co.uk/itm/like/201217988116?lpid=122&chn=ps&adgroupid=35836733199&rlsatarget=pla-260581918282&adtype=pla&poi=&googleloc=1006494&device=c&campaignid=672517669&crdt=0

I am searching on here because I am looking at a similar project, I have a sprocket with a shaft encoder and I am need to measure distance based upon the circumference and revolution of the sprocket, I am wanting a trigger, when it reaches a certain distance traveled, assembling the parts now and and trying to educate myself on the programming, I am a newbie to programming.

You could make your setup pull a long measuring tape...

regards

Allan