Scrambler C

[Smithy0013]

Question: Has anyone experimented with a swiveling back wheel (similar to what you may see on a shopping cart)? The purpose being you don't have to try so painfully for those 90.000000000 degree angles that will get your car to go straight. Instead, the wheel will swivel so the car travels in precisely the direction you launched it. Also, no electronics allowed on the car but are they allowed to prime the car? (e.g. a motor to wind the wheels back that is removed prior to launch)

[wjnewhouse]

Also, no electronics allowed on the car but are they allowed to prime the car? (e.g. a motor to wind the wheels back that is removed prior to launch)

Rule 2i. says that "No electrical or electronic devices may be used on the Scrambler, its alignment devices, or any tools (with the exception of any type of calculator)." So I'm guessing that anything to prime the car would be considered a tool, and wouldn't be allowed if it were electronic :/

[A Person]

Question: Has anyone experimented with a swiveling back wheel (similar to what you may see on a shopping cart)? The purpose being you don't have to try so painfully for those 90.000000000 degree angles that will get your car to go straight. Instead, the wheel will swivel so the car travels in precisely the direction you launched it. Also, no electronics allowed on the car but are they allowed to prime the car? (e.g. a motor to wind the wheels back that is removed prior to launch)

For the first question, that is not a suggestion I would make. The use of a swiveling wheel wouldn't seem to work that well, because if you don't take the effort to place both the car and the rear wheel into a set position, the initial movement could easily cause the car to move ever so slightly off center. Also this with the fact that using rear wheels that swivel at one of the most crucial moments of the run is kinda not worth it. I would honestly just suggest building a normal frame just because of its reliability, but if you feel like what you mentioned could work, then go for it. For the second question, I don't see anything preventing you from doing it, but I would give the same suggestion that my coach gave to me when I had that idea. He said to be safe and not use it. I think he had the opinion that I could get DQ'ed because of it or tiered for some event supervisors's understanding of the rules. (Nevermind, look at above post and disregard my statement about it. Thank goodness you didn't do it.)

[joeyjoejoe]

I see (and fully understand) why the entire push rod should be considered part of the 2kg weight but does anybody have an idea about how this could be measured accurately? Our first attempt at a launcher uses a push-rod system with a 4lb weight at the end of the top segment. The top segment is made of PVC. The push-rod itself is made with a dowel. The problem is that the top part is glued into the ramp with PVC glue. If you haven't seen a push-rod launcher, when in the launch position our launcher looks like the number "7" with the top of the "7" being made of PVC pivoted and glued to the ramp on the left. The weight is attached to the top right corner of the "7" and the near-vertical part of the "7" is the push-rod dowel. Can this be salvaged or should we just go back to the drawing board and use the falling mass and pulley system?

[iwonder]

How is the top portion glued into the support? It has to pivot, so our version has a cotter pin style attachment that holds it into the top, and we can easily take it out for measurement. Of course, I'm looking at going from pushrod to pulley just because you can concentrate more of the mass up high and it's easier to change the aiming of it.

[joeyjoejoe]

How is the top portion glued into the support? It has to pivot, so our version has a cotter pin style attachment that holds it into the top, and we can easily take it out for measurement. Of course, I'm looking at going from pushrod to pulley just because you can concentrate more of the mass up high and it's easier to change the aiming of it.

The swinging part of our launcher uses a PVC "T" with caps glued at both ends and with a 3/8" threaded rod going through the caps. The extreme ends of the rod are attached to two 1.25X3/8" bearings that are super glued inside the PVC pipe of the stationary part of the ramp. The perpendicular part of the "T" is where the pushrod assembly actually starts. It is also glued but, even if it wasn't, I'm not sure the judges would agree that only that part below the "T" would represent the entirety of the falling weight since a small portion of the "T" contributes as well.
I agree with you. I think we will be able to get a better use out of the 2kg weight with a pulley system.

[Smithy0013]

Woot just spent 12 straight hours on this event! So has anyone been calculating scores in their test runs? I should start testing tomorrow (weather permitting i get to school :p) and I have no clue what I should aim for

[joeyjoejoe]

Hey, where are y'all getting your bearings? We were getting them at a local hardware store for around $6 a piece. We are making major modifications to our car and I was looking for places that gave us more options (flanges, grooves, different ID/OD). Most of the places that I am finding online can beat that price considerably--IF I buy a thousand of them. I need a relatively inexpensive source that can give me a good price for 8-10 bearings. Thanks!

[iwonder]

8-10 bearings for one car? wow.. we have 4 in the car and 2 in the launcher. Anyways, McMaster Carr has bearings for not terribly expensive prices, and if you want everything imaginable Stock Drive Products has everything, but the 4 in our car cost us $40 for bearings and $20 for the mounts (aluminum mounts to turn them into pillow blocks). It's going to be hard to find prices cheaper for the same thing since the hardware store probably buys thousands of them.

[Smithy0013]

I second McMaster. Great search engine for finding exactly what you want. Dont go to them for everything though cause some of their prices are a little ridiculous