Trailer roof edge question.

[Hersbird]

off original topic but about faraday cages, I was wondering why the back of my mail truck doesn't seem to be a faraday cage. It is aluminum all around with a metal divider door from the cab to the back. I don't see any holes larger then 1/2 inch but I get a cell signal back there. Is it because the rubber gasket around to door acts as an antenna in?

[freebeard]

Cool. Is it a Grumman?



There's a local Burning Man truck that has an aluminum body. The finish is swirl marks from an angle grinder. I'd go with 6-8" overlapping circles.

About the Faraday cage, there may be RF field strength meters for testing the cage-iness as close as your local Radio Shack. Oh, wait.

It has one sliding and one roll-up door? It may need [ionically compatible] grounding straps or electrically-conductive grease on the rubber seal?

[Hersbird]

Actually looking at it today I think it's the 3rd brake light. A 2"x6" direct penetration and all plastic. I'll try and cover that with foil and see what I get.

[freebeard]

Is there a thread about aluminum mail trucks? Because if you spin one off, I'd follow there.

If I was a kid starting out today with no vehicle but a perceived need, priced out of the classical VW market, that's what I'd do. Get a Grumman mail truck (the one with the three-piece windshield and fiberglass nose) as they are being dumped into the market by the Post Office. Begin the electrical conversion with things like the charger, DC-DC inverter, hot water for space heat and battery boxes; follow with the batteries themselves when the price/performance number ramps up; and finish up by replacing the diesel engine with the motor/regenerator. After using it as a mobile back-up battery pack to the tune of 20-100 Kw/h.

Baja the nose so it looks like a 1930s Burney; clip-on pods abaft the roll-up door.

[ThomCat316]

Nice thing about those is that they are basically GMC S-10/Sonoma chassis, so there's a HUUGE aftermarket.

Want to lower it 'til it sucks the stripes off the road? No problem! Air suspension? Sure! Swap in anything from a 3-cyl diesel to a Chevy LSx V8. Install proven electric drive conversions. Convert it to 4WD. Have a ball!

Pricey for an S-10, though - just looked at a closed auction, 56K miles, $3500. Cheap as a base for an RV, though...

Obligatory-return-to-topic: The side-roof edges are nicely rounded, but I think the sliding door tracks at the top of the side panels might ruin the effect.

[Hersbird]

"Mine" looks like this
although it is the property of the federal government. It is all aluminum even the nose. They are in process of a new design to replace over 140,000 of these as they are all 20-30 years old now. They will be very inexpensive to buy once they are finally surplused. The test image of one of new designs looks like it follows the template some but is much taller with 6' stand-up height inside.
Anyway, they are on an s-10 chassis but I have heard there are no more good transmission cores out there anymore, we have used them all and they now have be rebuilt so any times the rebuilders won't give us warranties anymore. Plan on fabricating some kind of swap if you buy one, they are only non-lockup 3 speed automatics anyway so would be the first thing to ditch for economy.

[freebeard]

They will be like the 'used school bus' of this era. At least one will be painted magenta and turquoise.

Maybe start a thread when they go up at auction?

[ChazInMT]

I found a good image of the new mail truck HERE Below is a small version of it to fit in the Sub 580 Pix Ecomodder format.



Following the template......not so much. But at least it ain't a shoebox any more.

[ThomCat316]

Here's a very primitive CAD drawing of what I have in mind:

[Hersbird]

RE, the future mail truck. For some reason that small pic looked like it tapered but I guess not. That is also just an idea to show the general specs. It has an immediate problem as the driver's side door needs to be sliding but immediately behind that is another side door which would be some kind of magic trick to make work.

I like ThomCat's primitive on topic drawing though.