Gravity Vehicle C

[engineeringmaniac]

Even if the skidding is consistent, what is there to prevent backlash with the string system? Thats why ive always strayed away from it...

What about useing a little bit wider wheels to eliminate skid?

[fishman100]

Even if the skidding is consistent, what is there to prevent backlash with the string system? Thats why ive always strayed away from it...

What about useing a little bit wider wheels to eliminate skid?

2 years ago I used the string system for Battery Buggy and it worked just fine. We never had any problems with backlash/skid, etc.

The wheel size depends on your ramP and brake system. That being said, what are your guys' thoughts on braking systems? Obviously the wingnut will still be popular...

I'm definitely thinking putting string around both axles that's attached so they both stop at the same time, which gets double the stopping power. The skidding should be consistent.

How would you wind that? I tried to wind string around both axles but it didn't work and it frustrated me.

[Primate]

The wheel size depends on your ramP and brake system. That being said, what are your guys' thoughts on braking systems? Obviously the wingnut will still be popular...

I'm definitely thinking putting string around both axles that's attached so they both stop at the same time, which gets double the stopping power. The skidding should be consistent.

How would you wind that? I tried to wind string around both axles but it didn't work and it frustrated me.

Drill a hole through both axles, thread the end of the string in, and tie. Measure out slightly over 10m, cut the string, and attach to other axle with the same procedure. Wind all the string up on the front axle--make sure to wind forwards. Then, wheel the vehicle back the appropriate distance, and you're done!

Now, in competition, you'll have to estimate the number of winds you'll need, since you can't roll your vehicle along the floor. Do a bunch of tests ahead of time to determine your winds/distance ratio. It''ll still be quite accurate.

[Flavorflav]

If it is the same material, I see that as user error or it got bumped during transport.

Has to be, unless it was on ice. 10 cm is a lot of skid for mousetrap.

[bearasauras]

Calibrate? Unless you go to the competition area the week before, calibration is going to be hard.

2 years ago, for mousetrap, we had perfectly calibrated the MTV for our school's floor, but at the state competition, we missed the line by around 10 cm. And the floor apparently was level. And it looked exactly like our school's floor.

Do you know if there was a finish on the track and was the track clean? I've seen a different in performance of the brakes right before and right after the track is cleaned, but I agree with those above that 10cm is quite a bit.

[haverstall]

Ok, maybe I should have been more precise in my wording.

It came short of the line by 10 cm our first try, and then came short by about 5 cm on our second try. And it was weird, because we were doing the same exact turns we had used at school.
The surface looked pretty clean to me, but we were just so confused on how after so much testing, we still came short.

Maybe it was user error, but I think my other point still stands, that calibration for different floors is pretty hard unless you're testing on the actual surface itself.

[fishman100]

Ok, maybe I should have been more precise in my wording.

It came short of the line by 10 cm our first try, and then came short by about 5 cm on our second try. And it was weird, because we were doing the same exact turns we had used at school.
The surface looked pretty clean to me, but we were just so confused on how after so much testing, we still came short.

Maybe it was user error, but I think my other point still stands, that calibration for different floors is pretty hard unless you're testing on the actual surface itself.

My partner and I were testing at the exact location that BB was going to be held and got pretty good results. But the next day (the day of the competition) we did everything the same but ended up getting a lower score than we wanted. (Maybe they cleaned the floors after we left...that might have been a factor in the buggy's performance.) So even if you're testing on the same surface it may still be hard to calibrate.

[nerpas]

Regarding mousetraps going shorter than tested at competitions ( =my feelings regarding this phenomenon )...
We came to the conclusion that it was due to our string (dental floss) stretching during repeated testing, then shrinking down again overnight. (of course, this is just a hypothesis)

[haverstall]

Regarding mousetraps going shorter than tested at competitions ( =my feelings regarding this phenomenon )...
We came to the conclusion that it was due to our string (dental floss) stretching during repeated testing, then shrinking down again overnight. (of course, this is just a hypothesis)

Actually, this was the year you went to Greece, and I think we used normal string (which could still fall under your hypothesis)?

It's funny that we're talking about MTV on Gravity Vehicle forum...

[nerpas]

Actually, this was the year you went to Greece, and I think we used normal string (which could still fall under your hypothesis)?

It's funny that we're talking about MTV on Gravity Vehicle forum...

Oh yes, I know! I think we both had the same problem...maybe it's a MV thing?

And, in the interests of being semi-on topic... Based on our experiences with mousetrap, string brakes might not be as accurate as non-stretchable methods.