Car curves on the way back

[theredbirdy]

Hey Guys,

My partner and I have been having problems with our car curving on the way back. Our car goes straight on the way forward though. We are completely confused. Help!

[dragonfruit35]

Hey Guys,

My partner and I have been having problems with our car curving on the way back. Our car goes straight on the way forward though. We are completely confused. Help!

Is your car designed to go straight or curve a certain direction? Also, is your axle securely positioned?

[theredbirdy]

Our car is designed to go straight. The axles are straight. The back wheels are on a threaded rod and are slightly angled, but the car curves significantly. It doesn’t curve when we roll it without power though.

[Dreamz]

Our car is designed to go straight. The axles are straight. The back wheels are on a threaded rod and are slightly angled, but the car curves significantly. It doesn’t curve when we roll it without power though.

When you wind the string around the axle, make sure that you're winding consistently every time as close as possible to the center of the axle. My team had a problem where our string would stray to an end of our axle, thereby changing direction a ton. These inconsistencies get worse if your axle isn't secured.

[dragonfruit35]

Our car is designed to go straight. The axles are straight. The back wheels are on a threaded rod and are slightly angled, but the car curves significantly. It doesn’t curve when we roll it without power though.

Wait, your axles are straight but the wheels are angled? How does that work?

Also, if it doesn't curve when you roll it without power, maybe the mousetraps are pulling unevenly on your axle somehow- are they/the string centered?

[cuber]

I had this issue as well. Not entirely sure what caused it but adding a ~200g chunk of pewter to the back end fixed it for me. Unfortunately it also raised my times from ~10s to ~14s, but the accuracy gain was worth it. My hypothesis is that the jolt of the reversal lifts the back axel ever so slightly, and while midair, it gets dragged slightly in which ever direction the lever arm is torqued.

[MTV<=>Operator]

I find that having a front drive axle helps avoid this problem. The front cannot lift upon reversal due to the weight of the mousetraps and the entire back of the chassis holding it down to counteract this. This is the main reason why I switched from back to front wheel drive. Increasing traction can also reduce the issue.

In addition, speaking of vehicle curves, does anyone know what would cause a steering lock bolt to move during the run? This messed up my runs at states yesterday by allowing a piece of gym tape on the floor to change the axle offset causing my car to curve outwards but not back inwards towards the CTP. I went from scoring consistent 25s in practice to 125 at states. My guess is that there may be too much play between the bolt and nuts but I am still unsure of what happened exactly.

[Fridaychimp]

I find that having a front drive axle helps avoid this problem. The front cannot lift upon reversal due to the weight of the mousetraps and the entire back of the chassis holding it down to counteract this. This is the main reason why I switched from back to front wheel drive. Increasing traction can also reduce the issue.

If both your drive axle and mousetraps are in the front of the vehicle, how do you get enough distance? Are you using pulleys?

[MTV<=>Operator]

I find that having a front drive axle helps avoid this problem. The front cannot lift upon reversal due to the weight of the mousetraps and the entire back of the chassis holding it down to counteract this. This is the main reason why I switched from back to front wheel drive. Increasing traction can also reduce the issue.

If both your drive axle and mousetraps are in the front of the vehicle, how do you get enough distance? Are you using pulleys?

Sorry, that statement was misleading. I meant that the weight of the mousetraps over the back/middle stops the lighter front end from lifting up off the ground. I had actually originally created a design with a 1:3 gear ratio and a 10 cm lever arm. It accelerated to a ridiculous speed, but due to the high rotational inertia, it took almost the full 8 meters to get to this speed, making it impractical.