Sunday, April 8, 2012

Concept Vehicle: ATV

I've always had an interest in ATV's and there are numerous necessities I've found that are required to build a successful one:

- Power/Torque (any speed is just bonus)
- Flexible chassis (stiff vehicles get stuck and lose traction)
- Good suspension system (goes along with above; as suspension systems enable you to keep traction)

Trying to implement all these into a Lego robot, I came up with this:

This is a concept ATV I made out of Mindstorms, I followed the three guidelines I set for myself above, and I'll explain all of them in further detail here in this post.

1. The drive system- Power and torque are essential in an ATV, as the motor must be able to push the robot across any terrain. If you recall an earlier post, I demonstrated how you can get power through gear ratios. I utilized a worm gear meshed with a 24t gear to give me a ridiculous 1:24 gear ratio. That's 24x the power the motor is outputting.
Example of a worm gear              
I transferred the motors power into the worm gear, which turned the 24t in a gearbox that came standard with my RCX. So though I dealt with a low speed bot, the power that came with it was extremely helpful.

The gearbox 
2. A flexible chassis- I put this as a guideline for myself because I felt like without a certain degree of flexibility from your robot, Mindstorm bots can be prone to getting stuck on uneven terrain. Adding a degree of rotation on your chassis helps keep this from occurring.

To achieve this, I simply built the chassis in two separate parts; the drive system, and the suspension mount. This way I was able to lock the two together using two single beams, adding a degree of flexibility.

The rotation radius of the bot is illustrated in these two pictures of the chassis.

3. A suspension system- A good suspension system is NECESSARY for an ATV. Unfortunately these are a bit tricky to build out of Mindstorm parts. I found an interesting solution using the rubber bands found in many kits, and attached the front two wheels to independently attached mounted suspension beams, supported by said rubber bands. By inverting the system, you have a make-shift suspension.

Normal drive
There are other guidelines into making a successful ATV as well, however these should get you going for now.

Send me pictures of your own ATV's!
Happy building guys.

Suspension flex

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