mousetrap car -- gear ratios? wheel size? toomuch?

[master_alexander]

For a project in physics i'm building a mousetrap powered car.

basically, when the mousetrap is pulled the string attached to it will pull on the string tied to the axle moving the car foreward. I want my car to have some more.. umph. i've been looking into gear ratios and things of the sort and i am wondering if i'm doing too much in the thinking process.

i'm trying to figure out if when i apply the rotational pulling to a big gear to pull a smaller gear it will make my car go faster than if it was right to the axle. from there, would wheel size matter and if so, how much?

[skife]

bigger wheels means it will go faster, smaller gears, mean faster.

top end of course.


you might want to think about traction too.

[sandfreestyle]

bigger main gear and smaller secondary gear means more speed. taller tires also mean more speed. the thing u have to remember is when u get more speed in gearing, the less torque u get. if u only want speed than try to get as big as u can. it might take a while to get to speed, but it will go real fast. if u want it to ok speed but get ther really quick, than gear it for torque. not as fast but gets to top speed really fast. it may also do wheel stands if done right.

[aut911]

dont bother with gears. with my mousetrap car I used a cone pulley design. Large ratio for sart off torque, tapered down at a high rate for speed, and distance.

CD's make great wheels but they need to be fitted with a hub so you can use a smaller axle to save weight and reduce drag.



do a google search for moustrap cars and you will see alot of great designs.

aut

[tribalman]

For a project in physics i'm building a mousetrap powered car.

basically, when the mousetrap is pulled the string attached to it will pull on the string tied to the axle moving the car foreward. I want my car to have some more.. umph. i've been looking into gear ratios and things of the sort and i am wondering if i'm doing too much in the thinking process.

i'm trying to figure out if when i apply the rotational pulling to a big gear to pull a smaller gear it will make my car go faster than if it was right to the axle. from there, would wheel size matter and if so, how much?

what materials are you allowed to use? when i did this back in middle school we had a limited amount and type of supplies. i remember i put rubber bands around the drive wheels. it doesn't matter how fast or hard the wheels spin if they don't have any grip. bigger wheels are better.

in physics class in high school some friends made a car shaped vehicle and put on a 12gram and used that for propulsion. might wanna find a way to combine the mouse trap and a 12 gram.

[master_alexander]

i'm allowed to use whatever i want as long as the main force of propulsion is the mousetrap. ...i could build a catapult if i wanted to and fling the car.

what do you mean by a cone pulley system?

[daviselk]

traction is your main prob... try and find some old records or somthing... they work well

[Hilltop Customs]

i'm allowed to use whatever i want as long as the main force of propulsion is the mousetrap. ...i could build a catapult if i wanted to and fling the car.

what do you mean by a cone pulley system?


I think he means to use a cone for the surface you wrap the string around.(instead of a straight axle) The larger diameter of the cone will allow you to apply more force while the smaller section of the cone will let you get more distance.

Dont forget to extend the arm of the mouse trap.....lets you use a longer string....which lets you get more wraps around the axle or whatever your using to drive it. Also dont attach the sting to the axle or it will wrap up after and stop the car

[sandfreestyle]

ur allowed to use anything.... how about hooking up a electric motor to a wheel and when the trap slaps shut it connects the circut and powers the motor. add a mini stering system and u got and rc mouse trap.

[master_alexander]

haha. i thought about having the mousetrap as a switch but the mousetrap has to be the only means of moving the car.

i had a really sweet hovercraft idea that would basically mean no friction between it and the ground.. but then steering would be bad.

i also had an idea of making a catapult and then flinging the car. it'd probably end up more like a trebuchet (sp?) but it'd be pretty sweet.

i'll probably use 5:1 gears, cd's, and a long arm. it won't be fast but it will go pretty far.


still exploring the cone idea... anyone want to draw a diagram?

[Hilltop Customs]

for the cone idea you dont even have to think of it as a cone....think of it as a thick axle and a thin axle. Your first wraps go around the thin axle(this gets you lots of distance at the end) and the last few wraps go around the thick part...the thick part applys more torque off the start. This could be as simple as wrapping the string around the bare axle and the thicker part be made out of a bunch of wraps of tape.

If you are really going to try and make this thing badass you will want to keep the string perpendicular to the way the the the trap is pulling. If you can cut metal, find a piece of copper tubing a little smaller than the radius of the mouse trap arm....cut it in half and make notches so the locking mechnisim of the trap will still work(use a popsicle stick to extend the trigger). Glue that baby under the trap so the trap just clears the whole way around the piece of tubing. Now just use some 1/8" or 3/16" pieces of round stock for your axles.....and if you really want to put the other kids to shame; isolate the axles with bearings.....actually if you just use the bearings to isolate the axles you will probably blow everyone else away :wow:

Oh and dont forget to rub some wax on your string! :clap: Or use some fishing line or really fine braided wire to reduce friction(if you use my copper tubing idea the braided wire will make a HUGE difference.....metal on metal ftw)

Did i mention i built a popsticle stick bridge that held 300 lbs when I was in 9th grade....oh and we were limited to wood glue and 100 sticks :rofl:

[Hilltop Customs]

lol its 5 in the morning and I'm drawing up mousetrap car schematics....lucky I dont have my other computer right now or they would probably be in solidworks :ninja:

http://i62.photobucket.com/albums/h116/rhizzill/untitled.jpg

Actually what would work better than the tubing would be just one support that would catch the string about where the mouse trap arm is in the picture(at the apex). the whole goal of this is to lengthen the amount of sting you pull while keeping the force as high as possible throught the pull. (the tubing is simple, quick to make, and effective though, thats why i would use it)

If there is no support the trap will pull really hard of the break(spring tension) till it gets to the apex....then as the arm(idk what to call it....mouse killer bar? lol) moves down toward the base it will develope slack and not be applying force to the string. Where as if there is a support at the apex...as the bar moves down toward the base it will be pulling the string over the apex and still have the string taught.

Hope that made sense. Oh and you could extend the frame in the front(not the drive side)longer than the trap to use large diameter wheels too....just made it small for picture sake.

[MoeMag]

I used the mouse trap arm as an electrical switch to close an ignition circuit on a small model rocket motor.

We had to put a pin on the front of our cars to pop a balloon at 10 or 15 ft. That way we got points for going in a straight line... and how long it took to get there.

That was almost 8 years ago... I won.


:cool:

[bjjb99]

Along the line of a mousetrap catapult...

Make the car small, dense, and roughly spherical so it will roll easily (can you call a ball bearing your "car"?). Create a little trebuchet out of the mousetrap. You'll get a surprising amount of distance out of it. I used to fling pencils the entire length of a classroom with a mousetrap catapult.

BJJB