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Wheeled Vehicle B

Posted: August 7th, 2013, 7:32 am
by Jim_R

Re: Wheeled Vehicle B

Posted: October 30th, 2013, 10:31 am
by goodcheer
Could someone comment on the rule about the dowel rod being the foremost part of the vehicle? Does that mean that whatever secures the dowel rod to the vehicle must stay behind the dowel rod? For example, a piece of wire wrapped around the dowel to hold it in place could not be used because part of the wire would be in front of the dowel? Also, it looks like the rules require the students to bring the dowel rod, so, ok they should be able to build it into their vehicle and not just place it in a "holder" like mousetrap vehicle. But that might make it clumsy to transport. Just thinking out loud, but this looks like a unique challenge. Any comments would be appreciated.

Re: Wheeled Vehicle B

Posted: October 30th, 2013, 4:37 pm
by Balsa Man
You raise some good questions and observations.

Clearly, as rule 3.f. reads, it is saying that NOTHING (“no part”) may extend beyond the front of the dowel. That clearly covers a/any part used to hold/secure the base of the dowel if it wraps around, and hence extends beyond, the front surface of the dowel.

Yes, by saying the vehicle must have the dowel attached to it, the student must bring it; it must be part of the vehicle. If your solution is to permanently attach it, say by gluing on the front (being careful the glue does not extend to/past the front edge), it would be very clumsy to transport- as well as being a real pain to work with in testing and competition (dowel breaking off, having to re-glue, repeat ad nauseum…. If it falls off on a competitive run, construction violation).

Yes, the rules as written do create a “unique challenge.” While the purpose and use (tripping timing gates) is exactly the same as the vertical dowels called for in both Scrambler and MagLev (and used previously in Mousetrap Vehicle), only Wheeled Vehicle has this significant, additional engineering challenge. On both Scrambler and MagLev, you can use a ‘holder’ configuration- a hole the dowel slides down into, or a tube it slides down into- a solid, reliable, easy to construct attachment, where the dowel can be removed for transport, and easily replaced. If, for instance, the rules said, “must be placed within 1cm of the foremost part of the vehicle…”, a) it would not make a measureable difference in timing, and b) it would make using a reliable holder easy.

It makes sense to think then, given the timing dowel rules for Scrambler and MagLev, that the Wheeled Vehicle rules were intentionally written differently; were written with the intent of making it significantly more difficult for this event; of creating this unique challenge. That may well be the case here. We have no way of knowing, unless someone involved in the rule making were to shed some light. With all due respect to the people who volunteer their time to put together the rules, there have been instances over the years when significant consequences were unintended; where the implications of particular wording just didn’t get completely thought through, and the result was ‘oh, we weren’t trying to do that…’

Regardless, there are a couple things to think about is mastering the challenge. First, you want the dowel as light as possible. Given how high it has to stick up, and the acceleration/deceleration the vehicle will experience, every little bit of weight off will make a major difference in the strength needed at the attachment point. Second, by working to close tolerances, one could get pretty close to a “holder”- play around with drilling a ¼” hole in a nice solid piece of…..something, then slice off (saw, file, etc.) a side of that piece until the edge of the hole just emerges- that way you have a hole almost all the way around the dowel…..

Re: Wheeled Vehicle B

Posted: October 31st, 2013, 6:19 am
by chalker
Note a 1/4" dowel is pretty thick. It's easy to drill small holes in it (across the diameter of it) and put some small nails or countersunk screws. Alternatively, you could trim off a bit of the thickness to create a small indented area, then have some sort of strap / tape / wire / etc hold it in place.

Re: Wheeled Vehicle B

Posted: November 5th, 2013, 12:15 pm
by Terminader_SciChamp
Does anyone have aqny recomendations for brakes or launch systems? :D

Re: Wheeled Vehicle B

Posted: November 6th, 2013, 6:56 am
by goodcheer
Thanks for the comments about the dowel rod. Based on the suggestions, we are going to try for a removable holder attached to the dowel as per the rules so it can be installed and removed easily.

Also, for Terminader_SciChamp, the Wheeled Vehicle Image Gallery link above has some good ideas. Choices for power: rubber bands, fiberglass rods, etc. Braking: threaded rod with wing nut works great.

Re: Wheeled Vehicle B

Posted: November 6th, 2013, 4:01 pm
by Infinidude
For this event, can you propel the vehicle with a rubber band along with a mousetrap (making it -sort of- a mousetrap vehicle) or would you have to rely on the elasticity of the rubber band itself? If that is allowed, how could you apply a precise braking system?
Also, what would you recommend to use for the axles?
And can anyone give an example of how to incorporate the threaded rod with wing nut braking system?
Thanks in advance.

Re: Wheeled Vehicle B

Posted: November 9th, 2013, 12:32 pm
by goodcheer
For this event, can you propel the vehicle with a rubber band along with a mousetrap (making it -sort of- a mousetrap vehicle) or would you have to rely on the elasticity of the rubber band itself? If that is allowed, how could you apply a precise braking system?
Also, what would you recommend to use for the axles?
And can anyone give an example of how to incorporate the threaded rod with wing nut braking system?
Thanks in advance.
The rules state the material used to propel the vehicle must be "non-metallic, elastic." So, the mousetrap would not be allowed because of the metallic spring.

As for the axles and braking system, the threaded rod works great with a wing nut used for braking. Many of the photos in the Image Gallery link above show examples of this system. Here are the key steps you need to include in your design: The wheels have to be secured to the axle usually with nuts on both sides of each wheel. The threaded rod has to be attached to the vehicle so the rod and wheels rotate together when the vehicle moves. Don't forget to include a wing nut on the axle in such a way that it will move toward one of the wheels when the axle rotates: one of the tabs of the wing nut will have to slide along something like a piece of wood arranged parallel to the axle. Used in this way, the wing nut will stop the axle from rotating when it travels as far as it can toward the wheel. You adjust braking distances by locating the wing nut at different positions along the axle. This is probably not worded very well, but if you get the materials you need and work around with them, I believe you will get the idea.

Re: Wheeled Vehicle B

Posted: November 13th, 2013, 12:38 pm
by Bali90
because you cannot use any metal things where can u get a plastic fishing rod to use?????? please help me help me

Re: Wheeled Vehicle B

Posted: November 13th, 2013, 6:07 pm
by A Person
because you cannot use any metal things where can u get a plastic fishing rod to use?????? please help me help me
You can use carbon fiber, a common material for fishing rods due to their strength but reliable flexibility.