R/C Tank Combat

Rocket Launcher #RL001

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The octagonal hatbox was replaced with a 16" diameter circular base made from 1/2" ply and a cardboard form used for pouring concrete. The cardboard was screwed to 4 wooden blocks mounted on the base and a bead of hot glue was run around the seam between the base and the wall.

With all hardware removed the base was covered inside and out with gray primer.

The exterior wall was given a stone-textured finish, then the whole thing was sprayed with matte clearcoat.

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The lid was cut from 1/8" lauan plywood and finished with a sand-textured spray paint and clear coat. A small piece pivots on a machine screw to open the slot when the lid needs to be removed.

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The prior version had serious sideways movement. The flexible joint is now restrained in a hinged mechanism so it only pivots fore-and-aft (i.e. one degree of freedom).

The arms were cut from 1/8" aluminum bar and pivot on 1/4"-20 machine screws with locknuts.

The top plate was cut from 1/4" HDPE and fixed to the arms with #4 self-tapping screws. It allows the vertical feed pipe to slide up-and-down slightly as the hinge pivots.

A #4-40 ball linkage is centered between 1/2" aluminum spacers on a #4-40 machine screw.

Another ball linkage is connected by a #4-40 machine screw to a servo saver mounted on a Hitec HS-5485HB digital servo. This servo has much better standing torque than the analog servo previously used and better precision to take advantage of the elevation control on the new controller.

The hinge block, a threaded rod, the servo, and the base form a double-rocker four-bar linkage. The servo saver swings ±45deg while the hinge tilts ±10deg.

The existing rotate mechanism is unchanged except that it is mounted further out from the center, providing a little slower rotation of the base for more precision in the traverse.

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A 4 oz CO2 tank is good for a few dozen shots.

The Check It Uni-Mount used in the prior version was removed because it was jamming the pin on the tank.

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A Pelican Predator PS2 wireless controller is the heart of a new custom control box.

A 100 mm slide pot replaces one axis of a joystick and controls elevation with precision, repeatability, and best of all it doesn't return to center when released. A numeric scale allows for accurate range once calibrated.

A rotary pot with a pointer knob replaces the other joystick axis and controls the direction and rate of rotation of the base.

A low profile pushbutton provides the Start function and the original red/green LED assembly is mounted right below.

A shiny red pushbutton with a guard is the Fire control, replacing one of the original pushbuttons.

The rotation sprocket had been slipping for a while because the silicone on the floor tile was being torn up by the sprocket teeth, so during Gettysburg 2016 we replaced the sprocket with a servo mounted wheel.

This works much better, providing plenty of grip but allowing slip if there is a problem.

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