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windu34 wrote:

Aristotle wrote:Hey everyone,

I was watching a few videos and saw the usage of geared axles. I was wondering what the advantages/disadvantages were of using geared axles instead of a simply thicker axle.

Thanks

Gearing is typically used to increase torque allowing faster acceleration in this application (unlikely its being used for the reverse). Not sure why you would think a thicker axle is equivalent to gearing

I believe he's referring to the fact that a thicker axle has a heightened wheel and axle-like effect when the line is ultimately wrapped around it. When the axle becomes thicker, the applied force is farther away from the axis of rotation which increases the torque given angle and applied force remain the same. So, I believe torque could be increased through either of these methods, but I'm guessing the gearing ratio allows for larger adjustments at a lower weight sacrifice. Either route will, however reduce how many rotations the string will directly impart.

Could a circle cut out of a sheet of wood be used a dowel?

Daquan wrote:Could a circle cut out of a sheet of wood be used a dowel?

I don’t think so... Dowels are not very expensive, is there a particular reason why you can’t get one?

Has anyone found a mousetrap more powerful than the basic Victors that still fits the dimensions in 3a?

Fridaychimp wrote:Has anyone found a mousetrap more powerful than the basic Victors that still fits the dimensions in 3a?

Apparently Tomcats are more powerful, but they don't last as long and require frequent changing.

Have used both in the past and I think that the tomcat was a tiny bit stronger. They vary in strength quite a bit in the same package of 4. We ended up using a fish scale at the 90 degree point to find the relative strengths. We kept the 2 strongest for the state event and used the next 2 until then. With several teams, I think that I have 16 used ones.

Hello guys,

How are you guys making the vehicle go foward and back? I’m kind of stuck on that because my idea is to turn the rod foward then loop and turn it backwards if that makes sense. Thanks

just finished prototype build:



Build notes:

• I'm so happy our school was able to purchase 2 prusa i3 Mk2 3d printers this year, it really makes prototyping exponentially faster
• Banebot wheels are really good traction wise but I wish they came in larger diameters
• 1/4 threaded rod is a little on the heavy side, so acceleration is slow
• Doubling back the string certainly seems like the most effective manner of reversing the car
• You probably want to use stiffer parts than basswood for the frame and lever arm, as both flex slightly. Square carbon fiber tube should be optimal
• Making sure that the car runs perfectly straight is a major key to accuracy

I'm tossed up between fixing a pair of calipers onto the nut braking system, or counting wheel rotations (with a protractor for extra accuracy) as a method of setting the braking distance.

cuber wrote:just finished prototype build:



Build notes:

• I'm so happy our school was able to purchase 2 prusa i3 Mk2 3d printers this year, it really makes prototyping exponentially faster
• Banebot wheels are really good traction wise but I wish they came in larger diameters
• 1/4 threaded rod is a little on the heavy side, so acceleration is slow
• Doubling back the string certainly seems like the most effective manner of reversing the car
• You probably want to use stiffer parts than basswood for the frame and lever arm, as both flex slightly. Square carbon fiber tube should be optimal
• Making sure that the car runs perfectly straight is a major key to accuracy

I'm tossed up between fixing a pair of calipers onto the nut braking system, or counting wheel rotations (with a protractor for extra accuracy) as a method of setting the braking distance.

Very nice looking build! Do you mind posting scores?

I’ve personally been using larger wheels and a much smaller lever arm, but I don’t know this event very well.

Also, a random tip for all: using nylon threaded rods for your drive axle doesn’t work unless they’re very thick; the tension from the string bends them too much. Windu posted this previously, but I second it: thin steel/titanium is the way to go for threaded rods. (IMO)

4 mm threaded brass rod works quite nicely.
Question, since your pulley/axle appears to be the same size on both sides of the pin, how are you accommodating the difference in forward motion distance and the reverse motion distance?
Taking the thread off to wind each side separately is a royal pain.
Cut down wine bottle corks work well to have a larger "pulley" of various sizes. You can put them on a threaded rod (with washers and nuts), load it in a drill motor and have a poor mans lathe.