VEX Tetras

[skimoose]

The 1/3 scale tetras Art04 and I constructed, and have been used heavily for two years now, were made out of 1/2" CPVC water pipe available at Home Depot. Use CPVC (it's yellowish in color not white), NOT PVC, it has a smaller OD.

1 Cut the CPVC to 10" lengths to get good 1/3 scale tetras.
2 To connect the CPVC into tetras cut 1" long pieces of 3/8" wood dowel.
3 Apply gorilla glue and drive plugs into the pipe ends until flush.
4 Let dry.
5 Photo reduce the drawing of a FRC clover to 33%, or draw your own in CAD.
6 Cut clovers out of a scrap piece of vinyl siding with heavy duty scissors
or sheet metal sheers.
7 Pre-drill plugged pipe and clovers for #6 screws.
8 Assemble tetras with #6 x 1" sheet metal screws.

These tetras cost about $1.50 each to make.

We made regular tetras, vision tetras (with 1/8" Lexan painted green), and hanging tetras (with magnets from home depot). Each tetra weighs about 1 pound. A good scale match to FRC tetras. We found that vinyl siding (also a PVC) was the most durable for clovers. It would still occasionally break, but would last through several ROUGH demos before failing.

The goals were made in a similar fashion using 1/2" EMT (electrical metallic tubing) also available at Home Depot.

1 Cut the EMT to 24" lengths to get good 1/3 scale side/end goals, or 16"
and 13.25" for a center goal.
2 To connect the EMT into goals, cut 2" long pieces of 5/8" wood dowel.
3 Apply gorilla glue and drive plugs into the pipe ends until flush.
4 Let dry.
5 Photo reduce the drawing of a FRC clover to 33%, or draw your own in CAD.
6 Cut goal clovers out of a piece of 1/8" thick Lexan with a band saw and
bend it with a heatgun.
7 Pre-drill plugged pipe and clovers for #6 screws.
8 Assemble goals with #6 x 2" sheet metal screws.

Goals cost around $6-8 each to make.

Everything was purchased at Home Depot. Except we didn't buy a length of vinyl siding, we had some left over from building our house. A one foot long piece of siding should make many dozens of clovers.

Here's some of the finished products at the National Science Teachers Association conference being played with by a Vex 228 Gus and FRC 173 Rage!



Best mini tetras we've seen yet!

[skimoose]

Also, we made auto-load stations out of 1/2" square hardwood stock, purchased in Home Depot in the millwork/moldings area. With 1/8" hardboard bases which could be weighted for rough play. I don't have the dimensions handy other than to say it's exactly 1/3 scale. Again, assembly was gorilla glue and #6 screws.

Cost per auto-loader was about $5.00 per station.

Here's almost 1/3 of a 1/3 scale Triple Play field at the New England FIRST conference.



This whole setup is a real show stopper anywhere it went.

Don't worry about weight of the tetras. The Vex Gus was able to lift three one pound tetras at once. It had a two stage arm gear box (I think it was two 4:1 stages) and the elevator used a 4:1 gearbox to a 24 tooth sprocket. The two stage elevator used only single chain to lift and worked very reliably. We've had maybe 15 or 20 chain separations or breaks in two years. Changing the lift mechanism to double chains would probably make it nearly indestructible.

(Actually, this picture shows Mini Gus with the version 1.0 elevator made out of starter kit parts which still worked very well.)