Budget RC car races (Challenge Setup)


Old 12-07-12, 10:28 AM
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Budget RC car races (Challenge Setup)

A few of us in this engineering office are truly big kids.
Got talking over lunch and came up with a fun, affordable weekend challenge for a small group of us, Racing heavily modified, department store RC cars.
Long story short, we'll meet up a Saturday or Sunday every few weekends to drag race RC cars we bought at a department store. The car and modifications can't exceed a set limit (say $100)
The drag run will be ~100ft, using an LED trip line to start a timer and another to stop the timer. Weíll probably have a winners pot (say $5 buy in, winner take all).

What I am looking for is ideas on how to set the rules. We want to set a level playing field where no one is limited by $$, and only limited by their creativity. Itís all in good fun and although it can get competitive, there really isnít a huge monetary value to win (other than bragging rights).

So far, the rules a few of us think would work is;
- RC car must be purchased at a brick and molder chain store (Radio Shack, Walmart, etc) and not from a hobby specific shop or online only store (i.e. amazon, ebay, etc)
- Car and parts cannot exceed $100 or $125 total (before taxes), batteries not included in price limit. (Not 100% sure which limit to set)
- Alkaline batteries only (Handheld radio transmitter excluded)
- Must retain original car frame/chassis, but may be modified (cut outs, added parts, etc).

The issue I have is how to accommodate parts and materials for custom fab stuff. It's hard to account for a small piece of scavenged metal, washers, fasteners, wire, tape, etc, under the limited $$. Maybe set an estimated limit of ~$20 of miscellaneous fabrication parts?

The interesting and entertaining bit about this is most/all department store RC cars are not designed to be modified or fitted with aftermarket parts. A lot of creative work will be required and we should see some good mishaps (looking forward to seeing a wheel go flying).

Any thoughts as to how to address the custom fab costs in the rules and or anything I might have over looked?
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Old 12-08-12, 08:16 AM
Join Date: Nov 2007
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I would limit vehicle power to the originally-supplied battery voltage. Boosting the volts would be the easiest "cheat" to getting across the 100' line quickest and certainly isn't much of an engineering challenge.

My opinion on a good $100 Rx to victory:

high-current battery pack
high-torque motor
large "pizza-cutter" wheels

But a department store car might only survive 1 run. The torque & acceleration is likely to turn the cheap gearbox to mush
Old 12-08-12, 08:45 AM
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How many mods do you think will happen other than paint? More mods = more weight = slower speeds. And is there enough torque in a over the counter RC car to warrant mods to wheels for better grip? Just curious, no expertise what ever, but we are all just big kids at heart.
Old 12-08-12, 09:39 AM
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This is the fun of this type of race. Can't just dump a large motor as you'll destroy the car on launch as you'll have to budget support mods.
I have a few ideas for the drive system which will include a 555 timer switching from lower voltage, high current to high voltage, lower current. Gears will be pretty tall as most RC cars are at top speed within 20ft or so. A rewound brushed motor will be the power plant.
Old 12-08-12, 10:17 AM
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If you make the rules too limiting you'll end up racing them just as they came out of the box. I first thought of limiting them to their stock motors but removing high performance brushless motors as an option seems boring. Limiting the cars to a maximum number off the shelf, brand name alkaline batteries I think is an interesting rule. Everyone would be working with the same power source and alkaline's limited ability to dump power quickly turns it to a game of drive system efficiency, aerodynamics and weight.

Hold a first "season" race series requiring that you stick with the stock chassis and motors. Then after a champion has been chosen loosen the rules and create a new race series base off the original cars. Say if you allow custom built chassis for the second race series. This would allow much of the parts from the first series to be re-used helping to keep the cost down and it allows a whole new chance for competition and someone else to win.

With each series you can relax or open up another area to modification. After a year you'll all be running brushless motors and whipping LiPo's till their too hot to touch.
Old 12-08-12, 11:39 AM
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I was thinking of leaving the motor option open. After all, $100 for the car and mods sure won't leave any budget for a motor and controller for it. Also keep in mind, those kids cars don't have the electronics to support brushless so there will be some interesting electronics to compensate for that. Odds are, the stock motor controller for mine will simply fire a relay which would allow a pair of caps to dump power to the motor. Most cars I've seen worth working with are about $35 to $45.

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