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Comments 2
  1. — James May    Jul 20, 2006 17:15 PM    #

    Just following on from your optimising mileage link, I have been wondering about how to go about making an umdertray for my EV. It’s pretty rough underneath with a step down to the battery box just in front of the rear wheels. What has spurred me on a little is a surprise 5% improvement on energy used on one of my standard journeys caused by lowering the car about 3-4 cm. This is easy with hydrolatic suspension. I just let the fluid out over the floor!.I don;t really believe this 5% improvement is down to reduced frontal area, I think i’s more likely down to the car being previously too high and running the driveshafts at an angle. This would have reduced the efficiency of the CV joints and put the tyres at slightly the wrong angle, preferentially flexing the outer tyrewall and losing energy through rubber hysteresis. Its currently running a shade too low because I took out too much fluid. Reminds me to make changes slowly.

  2. Jerry Halstead    Jul 20, 2006 18:50 PM    #

    Here’s an idea for material to use (from Adrian on the EVList earlier this year):

    Coroplast (corrugated polypropylene, correx, corroflute, etc.) is available in 2, 4, and 10 millimeter thickness. 3mm and 6mm are less common. A 4’x8’ sheet of 4mm runs $15 to $30 depending on the supplier/color. Smaller pieces can be much cheaper due to shipping restrictions. You can get it FREE from gas stations/grocery stores (old signs) or after an election – vote for free plastic!.

    You can use it to block off grilles, as a belly pan, flexible spacer, wire race, etc. It’s also used to make R/C airplanes, hamster cages, USPS boxes for sorting mail, as shipping/packaging material, etc.

    Corro will warp when it gets warm (in a car in the sun), so store it flat. Cuts with a utility knife, heavy scissors, X-acto knife, etc. Gluing can be tricky – Goop is probably the easiest:

    Goop/shoe goo – slather it on!
    Gorilla glue/ProBond/poly glue – rough the surface & mist with water. If possible, poke lots of little holes for the glue to seep through and create small “rivets”. Poly glue expands significantly with water.
    Cyanoacrylate/CA/Super glue – Scrub surface with mineral spirits or “flash” with a propane torch to drive out manufacturing oils – be careful! Results can be spotty depending on age of glue, humidity, etc.

    Test glue a few pieces first. With poly glue or CA the corro should rip before the pieces come apart!

    Here are some sources and websites with good tips/tricks for working with Corro.

    www.spadtothebone.com (see corro hinge tool, supplier list)
    www.harborsales.net (2,4,6,10mm coroplast)