BBISHOPPCM wrote:By bazooka tube, do you mean a roof-mounted rocket launcher? What line of work are you in, anyway? I would first cover the roof with asbestos for fire resistance, and maybe build a frame out of 1/4" thick steel angle irons that can be used to secure the launcher's mount (1/2" thick steel plate, about 2'x3') Cut holes in the roof , you're going to mount the plate 3" above the asbestos heat shield, to the steel frame that will pass through the roof. The frame will be secured (welded) to the perimiter of the car. Be sure to reinforce the car's chassis by running two I-Beams parallel to the frame rails. It wouldn't hurt to install run-flat tires, a snorkel, and a roof-mounted jump seat. Good luck!
A bit of overkill, but a good start. There are three basic problems you have to solve: Mechanical installation, electrical integration, and targeting.
PART 1: MECHANICAL INTEGRATION
First off, shoulder-fired rocket launchers have no significant recoil, so you don't need the heavy-duty mechanical support. An ordinary roof rack will be fine, and you won't need to develop your own attachment to the roof. It also minimizes the impact on the car's resale value.
A common newbie mistake is to mount the launcher horizontal to the ground. Unless you go with the more-expensive guided missiles, you'll be limited to a range of about 250 feet befor the rocket hits the pavement. You'll actually reach the impact point a second or so after the rocket explodes. The shrapnel, of course, if flying BACK at you faster. Not good.
So you need a bit of "up angle" on your rocket. About eight degrees will give you ~500 foot range. Unfortunately, the rocket will reach about 15 feet above the deck at the midpoint, so if you're too close, you'll miss the target entirely.
Best to compromise. Two degrees will give about 350 foot range, with a mid-course height of about 6 feet. Too high for an econobox, but pretty good for an SUV.
However, if you intend to continue the Yaris/Fit arguments on the road, this is probably not acceptable. In that case, go with about a half-degree angle (this gives a ~350 foot range, with next to no loft above the Versa's roof eight) and plan on hitting the brakes...HARD...right after launch. Down south, this is called a "Crazy Jim-Bob."
Use 0.090-thickness 2" angle aluminum (alloy 2024-T3) to provide mounting brackets for the launcher. Tie-wraps can be used to attach the launch tubes to the brackets, but they will deteriorate in the sun and the tubes do get a mite warm. Instead, drill ~3/8 holes through the vertical sides of the angles and use stainless-steel hose clamps (sized as needed) to lock the tubes in place.
The need for thermal protection on the Versa roof is mostly limited to the exhaust end of the launch tube...most rockets expend all their propellant before they actually leave the tube. If you're rigging up just a single launcher (more on that later) you can get by with purely ablative protection. This means, essentially, a sacrificial material that is allowed to get burned away and can be easily replaced. 1/2" birch plywood will be fine. If you intend the launcher as primarily a deterrent, apply two coats of Val-Spar varnish.
If the installation is for more regular encounters, the plywood can usually take a couple of blasts, but it does look ugly real quick. Ordinary ceramic tile from Home Depot works pretty good, and one can gain points with the girlfriend by letting them pick the pattern.
However, the ultimate protection is a sheet of 0.016-thickness stainless steel (alloy 302 has a nice shine). You'll need a set of sheers to cut it, though...stainless is tough material.
To absolutely minimize the danger of blistered paint, a bit of heat-proof insulation should be applied beneath it. Asbestos is rare and a rather severe health hazard; my recommendation is a product called "Fiberfrax." Comes in rolls, and you can cut it with scissors. Put it under the stainless steel, pin the whole thing down with #8 stainless-steel sheet metal screws, and mechanical integration is complete.
In Part 2, I'll discuss the more-thorny problem of adding a firing mechanism.
Ron