Scrambler C

[Chris_L]

Depending on how fast your ETV is going it could be that it skids differently between these distances which could be a combination of both wheel skid or the dirty floor. Cleaning the floor and taking into account skid of the wheels should help with your problem. How fast is your scrambler going?

[iwonder]

So I have been having a consistency issue when testing my scrambler. The number of wheel rotations is pretty consistent at every distance except those between 10 and 11, where it seems to take more winds than normal to achieve the desired result and the graph for rotations is not very linear. Would this be caused by the floor being different at that distance or is there an issue with the wheels? I have tested in a different area, but the same pattern still happens where the 10-11 points are the outliers.

I would definitely suggest cleaning the wheels with something like isopropyl alcohol and the floor all along the track (towel, swiffer, something). If it's having issues at the closer distances and not the farther ones then it's definitely a skidding issue (depending on bearings and friction it could show itself differently). Does the car stop straight or does it turn slightly when it stops?

I'm assuming you have a wingnut type of braking system, I used that every time I competed and my distance vs turns graph always had an R value >.99

[A Person]

I would definitely suggest cleaning the wheels with something like isopropyl alcohol and the floor all along the track (towel, swiffer, something).

I'm kinda confused on how rubbing the wheels with isopropyl will help more than, say, a wet paper towel. What material wheel would you have suggested that for? Rubber?

So I have been having a consistency issue when testing my scrambler. The number of wheel rotations is pretty consistent at every distance except those between 10 and 11, where it seems to take more winds than normal to achieve the desired result and the graph for rotations is not very linear. Would this be caused by the floor being different at that distance or is there an issue with the wheels? I have tested in a different area, but the same pattern still happens where the 10-11 points are the outliers.

I suggest that the first thing you do is change your location or run the opposite direction or something like that. Depending on the consistency of the car at other points, it could tell you if it's a problem with your car or your testing surface. However, because you said it takes more winds, I would suspect that your car is just slowing down or something like that. If your car goes fast, you'll have your first few distances skid a lot more than your later ones, meaning you'll have a sharper rate at the beginning of your graph before it reaches a constant rate, which would be your car maintaining that speed.

Man, I hardly post Scrambler stuff anymore. Good luck at Nationals, I hope you get everything straightened out by then!

[someusername]

So I have been having a consistency issue when testing my scrambler. The number of wheel rotations is pretty consistent at every distance except those between 10 and 11, where it seems to take more winds than normal to achieve the desired result and the graph for rotations is not very linear. Would this be caused by the floor being different at that distance or is there an issue with the wheels? I have tested in a different area, but the same pattern still happens where the 10-11 points are the outliers.

I would definitely suggest cleaning the wheels with something like isopropyl alcohol and the floor all along the track (towel, swiffer, something). If it's having issues at the closer distances and not the farther ones then it's definitely a skidding issue (depending on bearings and friction it could show itself differently). Does the car stop straight or does it turn slightly when it stops?

I'm assuming you have a wingnut type of braking system, I used that every time I competed and my distance vs turns graph always had an R value >.99

ya, we used to clean them with Isopropyl alcohol, but it was too time consuming in competition so we switched to rolling the wheels over duct tape before each run, which keeps the traction consistent. We also clean the track with a swiffer sweeper before each run. The time on it is about 2.2-2.3, so yes there is skidding, but the amount of skid is about the same at every distance except 10-11, which is weird. Another issue we had was it started skidding sideways when it braked (front end usually swings right) and we couldn't/can't figure out why it started doing that. As far as the braking nut goes, its a square nut in a square channel, so a little different than most, but it gets the job done. Anyways, I'm assuming its something to do with the floor, but I just can't figure out whats wrong with it.

on a side note, my threaded axle (front axle) just stripped out today and it is a square rod, so threading a new one by hand one week before nationals is going to be a blast...

[iwonder]

Definitely with the same skidding at something like 12m, it's a track issue. Skidding sideways is something I saw a lot before I switched to softer wheels (for a few seasons, actually) that got rid of the skid.

I'm a bit curious about the axle.. are the threads only on the corners then or do you mean square threads?

[someusername]

Definitely with the same skidding at something like 12m, it's a track issue. Skidding sideways is something I saw a lot before I switched to softer wheels (for a few seasons, actually) that got rid of the skid.

I'm a bit curious about the axle.. are the threads only on the corners then or do you mean square threads?

I'm using vex robotics rubber wheels, so the actual axle is square, so when threaded the nut only really uses the threads in the corner of the square because that's where the threads are the deepest

[fishman100]

Similar issue; our wheels skid upon launch (run time is about 2.00s) if the wheels/track are even slightly dirty. Be sure to thoroughly clean the wheels/track; we change the pad on our swiffer after every 2 runs or so to ensure the track stays clean every time we sweep it.

[iwonder]

Similar issue; our wheels skid upon launch (run time is about 2.00s) if the wheels/track are even slightly dirty. Be sure to thoroughly clean the wheels/track; we change the pad on our swiffer after every 2 runs or so to ensure the track stays clean every time we sweep it.

Our solution for that was to add a track in the launcher that guided the vehicle for the first bit of acceleration, the wheels would still skid but it would at least stay straight. Because of the soft rubber and cleaning the wheels (by the way, the isopropyl evaporates and leaves a much drier surface than possible with water) we didn't have major issues with skidding, even at <1.3 second run times.

[InfiniCuber]

Our solution for that was to add a track in the launcher that guided the vehicle for the first bit of acceleration, the wheels would still skid but it would at least stay straight. Because of the soft rubber and cleaning the wheels (by the way, the isopropyl evaporates and leaves a much drier surface than possible with water) we didn't have major issues with skidding, even at <1.3 second run times.

Little skidding issues with <1.3 seconds?? We have a car that goes 1.6-1.8 and we have skidding issues...

[iwonder]

Our solution for that was to add a track in the launcher that guided the vehicle for the first bit of acceleration, the wheels would still skid but it would at least stay straight. Because of the soft rubber and cleaning the wheels (by the way, the isopropyl evaporates and leaves a much drier surface than possible with water) we didn't have major issues with skidding, even at <1.3 second run times.

Little skidding issues with <1.3 seconds?? We have a car that goes 1.6-1.8 and we have skidding issues...

Ours weighed ~550g(maybe 450? It's been a year since I weighed it) with an egg, and the vast majority of the weight is directly over the braking axle so the front wheels have a ton of traction. Plus they're the softest, smallest ones we could find. We did have issues with the back end skidding out when it accelerated, but we fixed that with a rail on the launcher that held it in line until the string released. We cleaned everything for every run.