Battery Buggy B

[andrewwski]

I don't see any way that you could interpret the rules so that you could use them. They are pretty specific. EV rules did allow them. Microcontrollers and the like do not fit that line you posted, so the answer would be no, they're not allowed.

[fleet130]

The rules seem to be quite clear on what is allowed. Past rules for other events have no bearing on current events. What you see in SO videos only shows what was applicable at the time the video was made. The only rules are the rules found in the current rules manual and as clarified on http://soinc.org/. Videos have no bearing on the rules.

[Cyberdyne-850]

Thanks. The key piece of information I was missing (that Andrew provided) was that "EV Rules allowed for it." Since I did not have those rules, I was only a little worried (say, 1 tenth of 1 percent) that EV had a similar clause about electonic components, and the presence of microcontrollers at competitions represented a very liberal interpretation.

So, with this posting, let me say I stand convinced that microcontrollers are not allowed (in Battery Buggy B). As an aside, I am glad for it. As a volunteer mentor, it will be more fun for me teaching (and learning about) basic electronics (vs. microcontroller programming).

[bob3443]

So i have to build something for tryouts to get onto the team. I think I'd be best off building another sort of vehicle, so I'm going to build a battery buggy. I still don't have the rules and i don't think i'm getting them till wayyyyy later. I have two weeks and i want to get parts soon. I was wondering if someone had the rules so i don't have to build a completely new car for the competition. does anyone know if we're allowed to use laser pointers? and if so can we have like a person stand by the end of the track and hold up a paper or something there to see where the laser is actually pointing to? If we can't use lasers can we use scopes? also how many/what type of batteries are we allowed to use. What are the min/max dimensions of the car/wheels? How heavy can it be? is the tie-breaker by weight? any other important rules?
also, would any of these two switches be the type of power switch i'm looking for? and although it doesn't say dimensions or weight it says it mounts in a 7/16" hole, so it can't be that big.
http://www.radioshack.com/product/index ... Id=2062532
http://www.radioshack.com/product/index ... Id=2062515
which is the best micro switch?
http://cgi.ebay.com/4X-15A-Long-Lever-M ... 286.c0.m14
http://cgi.ebay.com/Cherry-snap-action- ... 286.c0.m14
http://www.radioshack.com/product/index ... Id=2049718
please tell me if the are ok under the rules or not.

edit: is there any thing special i should look for in a motor? I should put a small gear on the axle and a bigger one on the motor right?

[Uncle Fester]

Let's simplify spec stuff-- a lot.

Switches: For the voltages you'll be working at, and the current load you'll have, "cheaper" works just fine. don't worry about VAC or VDC, you won't be at any load that will matter. If you use a magnetic reed switch, however (I've never seen anyone do this), their current limits are so low that yes, it's a worry.

I've had very good luck with adding an extension to snap switches (even though the stainless steel is virtually impossible to solder anything to) by wrapping solder braid (the stuff that sucks up solder so you can remove soldered parts) around the lever and the extension, adding solder to the wrapped assembly, and then pinching it with a pair of SMALL needlenose pliers or diagonal cutters to make it tighter. USED solder braid actually works easier because it's nice and stiff. I've made many a DPDT switch out of a pair of SPDT switches by placing them side-by-side and linking the lever arms together in this fashion. Heck, I made an 8PDT switch once this way.

Relays will work at a lower voltage than specified. Many 12V relays will "kerchunk" quite solidly at 9V. Excessive voltage CAN be a problem, if you overdo it. A 5V relay run at 6V or even 9V is NOT an issue. A 3V relay at 12V will let the magical smoke out.

I just did business with ALL ELECTRONICS, ELECTRONICS GOLDMINE, and KELVIN. All have websites, are easy to order from, and have pictures of almost all the stuff. Of the three, Kelvin is the simplest (little unnecessary detail), but is the slowest and seems to always backorder something when I make an order.

[ROFLWAFFLE]

What STUFF do we need for the battery buggy event?

[fleet130]

The design of the buggy is entirely up to you so the "STUFF" you need will vary, depending on your tastes. Here's a post from the old Electric Vehicle thread that should be applicable to this event:

Basic Electric Vehicle/Battery Buggy

With Dark Sabre's help, I've added some pics on the Battery Buggy Image Gallery. The vehicle above could win medals at many tournaments if it were made to the current required dimensions.

Some features of this vehicle:

Chassis: a simple rectangle of 1/4 in thick wood, available from most home repair stores. Any material could be used, but it's best to use the lightest material you can. It's also easy to drill holes for mounting components.

Wheels: Rear/Drive wheels appear to be 4in diameter "lite flight". These cost a little extra, but are considered the best by some. Many others that are less expensive (or even free if you recycle) are almost as good.

Drive axle/Transmission: One of several Tamiya gearboxes available. Assembled straight out of the box without modification.

Note: You might be able to recycle the entire rear axle with transmission and wheels from an inexpensive Radio Control vehicle.

Motor: The gearbox/transmission usually dictates what motor can be used. Motors are supplied with the Tamiya gearboxes.

Battery Box/Holder: This vehicle uses a common battery holder available from Radio Shack and others.

Steering: This is pretty basic, an articulated chassis with a vertical bolt to hold the two parts together and act as a pivot point. A longer wheelbase is easier to make go straight. Use a wing nut for easier adjustment.

Distance Measuring: Classic threaded axle/wing nut system. You have to go quite a ways to better this arrangement. As the axle turns, a wing nut travels along its length. As the wing nut nears one end of its travel, it contacts a switch and turns off the motor to stop the vehicle.

Brakes: None. As long as speeds are relatively slow, brakes are unnecessary. It would be fairly simple to add "Dynamic Braking" to this vehicle.

Electrical System:

Battery Box/Holder: Selected to hold the size/number of batteries used. Battery holders can be as simple as a piece of wood with nails driven into it to hold the batteries in place and make contact with the terminals at each end.

Batteries: Any size batteries can be used as long as they comply with the voltage and current requirements of the motor. Larger batteries are heavier and require a sturdier chassis, stronger motor, more braking force. Normal dry cells (primary cells) can be fairly expensive over time. Rechargeable batteries (secondary cells) require a greater initial outlay, but can reduce costs significantly over time.

Switches: The vehicle above uses separate start and stop switches. A common slide switch, located near the center of the chassis, is used to start the vehicle. This type of switch can require significant force to actuate and may cause the vehicle to move before it is actuated. It may pay to investigate other options that take less force. The stop switch is a lever switch (sometimes referred to as a micro switch) is located near the wheel in the upper left of the vehicle as shown. As the wing nut travels on the axle, it contacts the lever on the switch and depresses it to stop the vehicle. These switches are available from Radio Shack and many other electronic/robotic suppliers.

Wires: Almost any electrical wire can be used. A common source is recycled 4-conductor telephone wire. It can be separated into individual wires by removing the outer cover. Solid wire (has only 1 large strand of wire inside) is stiffer and easier to work with, but breaks sooner when flexed. Stranded wire (has several thin strands of wire inside) is more difficult to work with, but doesn't break as easily when flexed.

Motor: Motors determine the voltage and current capacity needed from the batteries and must be mechanically compatible with the transmission/gearbox used. Motors are usually supplied as part of commercially available transmissions/gearboxes. Another source for gearboxes/transmissions is old (or not so old) battery operated screwdrivers. The batteries may even be recycles if they are still good.

Dynamic Braking - Uses the drive motor to slow the vehicle. When the electrical current is turned off, the motor/vehicle begins to coast and the motor begins to act as a generator. The force required to turn the generator is proportional to the current (not voltage!) generated. When the generator is connected to an open circuit (infinite resistance), no current flows and the force needed to keep the generator rotating is only that needed to overcome friction. If the generator output terminals are connected together with a low resistance connection (short) the current in the circuit increases which, in turn requires more force to turn the generator. This acts as a brake to slow the vehicle.

[bob3443]

Would a roller chain be better than a gear on an axle? How would you start the car with a pen/pencil/etc. What type of switch would it be, rocker, toggle, button, etc.?

[robotman]

i am using a button switch and right now just have a rubber band attaching my gear ratio to my axle

[bob3443]

what cell batteries would be the best? and if i have 4, 1.5 volt batteries and put them in a battery holder wouldn't that become a battery pack and there have to be less than 4.8 volts?