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Doug Ferguson describes the concept of a Grave Jumper at Phantasmechanics.

My Grave Jumper is based on a four-bar linkage. Refer to my Haunt Mechanics page for a description of a four-bar linkage.

My design was based on Brent Ross' Pneumatic Lifter at Devious Concoctions. Brent made the ground and coupler bars from 1 ¹/₂" angle iron and the crank and follower bars from single bars of ¹/₈" flat steel.

Edwin includes an example of a four-bar linkage that he used in conjunction with a Trash Can Trauma. Edwin made the ground and coupler bars from ¹/₂" square steel tubing and the crank and follower bars from double bars of flat steel.

I combined the two designs, using Brent's dimensions with 1" square steel tubing and double bars of ³/₁₆" flat steel.

The tombstone is made using Dow blue insulating foam board and a half profile foam prop skull (#SK1135, $5.99) from Steve Hickman's Terror Syndicate GraveStalkers.

The head and torso are constructed using on a Terror Syndicate Monster Mud prop frame. Steve features Monster Mud props in his Home Haunter's Handbooks.

The rigid urethane foam prop hands ($19.99) are from Steve Hickman's Terror Syndicate GraveStalkers.

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The ends of the 1 ¹/₄" angle iron,  L₁,  L₂, L₃ and L₄, are cut at 45° angles. Position L₁, L₂, L₃ and L₄ to form a frame. Position the four 1" corner brackets such that the frame is square. Mark the four holes (depicted in the illustration) of each corner bracket on the angle iron frame. Drill ³/₈" holes in the angle iron corresponding to the marks. Drill out the four holes in each corner bracket using a ³/₈" drill bit.

Reposition L₁, L₂, L₃ and L₄ on the ¹/₂" plywood. Mark the holes in the angle iron frame on the ¹/₂" plywood. Drill a ¹/₈" pilot hole through the ¹/₂" plywood in the center of each mark. From the underside of the ¹/₂" plywood (using the pilot holes as a guide), countersink each ³/₈" bolt and washer using a 1" spade bit. Drill out the pilot hole using a ³/₈" drill bit.

This picture shows how the ³/₈" bolts and washers are countersunk into the bottom of the ¹/₂" plywood using a 1" spade bit.

Reposition the 1 ¹/₄" angle iron frame and corner brackets on the ¹/₂" plywood. Secure the frame and brackets to the ¹/₂" plywood using 1" long ³/₈" bolts, washers, lockwashers and nuts. A ³/₈" bolt with washer is inserted from the underside of the ¹/₂" plywood. Just hand-tighten the nuts for now.

Drill a ³/₈" hole ¹/₂" from the end of L₅ and L₆. Note that these holes are drilled from the "top" through to the "bottom" of L₅ and L₆. Drill a pair of ³/₈" holes 3 ¹/₂" apart, centered 5 ³/₄" from the opposite end of L₆ (refer to the illustration). Note that these holes are drilled through the "sides" of L₆. Drill a ³/₈" hole ¹/₂" from each end of L₇. Position L₅, L₆ and L₇ as shown in the illustration. Mark the holes in the 1" square tubing on the 1 ¹/₄" angle iron frame. Disassemble the platform and drill ³/₈" holes in the angle iron corresponding to the marks.

Reposition L₁, L₂, L₃ and L₄ on the ¹/₂" plywood. Mark the holes in the angle iron frame on the ¹/₂" plywood. Repeat the process of drilling pilot holes and countersinking the ³/₈" bolts and washers. Reposition the angle iron frame, corner brackets and square tubing on the ¹/₂" plywood. Secure the 1" square tubing to the ¹/₂" plywood and 1 ¹/₄" angle iron frame using 2" long ³/₈" bolts, washers, lockwashers and nuts. Just hand-tighten the nuts for now.

Position L₁₄ at the point where L₅, L₆ and L₇ meet. Position the four 1" x 5" angle brackets between L₅, L₆, L₇ and L₁₄. Mark the two holes (depicted in the illustration) of each angle bracket on the 1" square tubing. Disassemble the platform and drill ³/₈" holes in the 1" square tubing corresponding to the marks. Drill out the two holes in each angle bracket using a ³/₈" drill bit.

Reposition L₅, L₆ and L₇ on the ¹/₂" plywood and 1 ¹/₄" angle iron frame. Mark the holes in the 1" square tubing on the ¹/₂" plywood. Repeat the process of drilling pilot holes and countersinking the ³/₈" bolts and washers. Secure the 1" square tubing to the ¹/₂" plywood and 1 ¹/₄" angle iron frame using 2" long ³/₈" bolts, washers, lockwashers and nuts. Just hand-tighten the nuts for now.

The original holes in the angle brackets can't be used to secure L₁₄ since the holes are slightly offset. A hole that is offset to the right on one bracket will be offset to the left on the opposite bracket and the holes won't line up. New holes need to be drilled in the upright members of the angle brackets. The holes should be drilled on center. Holes in opposite angle brackets should be drilled in the same location. Holes in adjacent angle brackets should be offset by ¹/₂". Secure the 1" square tubing and brackets using 2" long ³/₈" bolts, washers, lockwashers and nuts.

Drill a ³/₈" hole 1 ¹/₂" and 4 ¹/₂" from the end of L₁₄ opposite the angle brackets. Drill a ³/₈" hole ¹/₂" from each end of L₈, L₉, L₁₀ and L₁₁. Drill a ³/₈" hole 6 ³/₄" from one end of L₁₀ and L₁₁.

Drill a ³/₈" hole ¹/₂" and 3 ¹/₂" from one end (the bottom) of L₁₂. These holes will be used to secure L₈, L₉, L₁₀ and L₁₁ to L₁₂. From the opposite end (the top) of L₁₂, on the adjacent sides, drill a pair of ³/₈" holes ¹/₄" and ⁷/₈" from the end respectively. These holes will be used to secure L₁₃ to L₁₂.

Drill a pair of ³/₈" holes 3" apart centered on L₁₃. Position the top of L₁₂ against the adjacent side of L₁₃. Mark the holes in L₁₂ on L₁₃. Drill ³/₈" holes in the 1 1/2" angle iron corresponding to the marks.

Drill a ³/₈" hole through the center (from the left side through to the right side) of L₁₅. Drill a hole on the adjacent side of L₁₅ (the bottom) to accept the threaded end of the air cylinder shaft.

Drill a ³/₈" hole ¹/₂" from each end of L₁₆ and L₁₇. Drill a ³/₈" hole in the center of L₁₆ and L₁₇. This holes is denoted by F₁ in the illustration.

L₈, L₉, L₁₀ and L₁₁ are attached to L₁₂ and L₁₄ using 2" long ³/₈" bolts, two washers and a locknut.

L₁₃ is attached to L₁₂ using a pair of 1 ¹/₂" long ³/₈" bolts, lockwashers and nuts.

L₁₆ and L₁₇ are sandwiched together and attached to L₆ using a pair of 2" long ³/₈" bolts, washers, lockwashers and nuts. L₁₆ and L₁₇ serve to center the air cylinder under L₁₅.

Drill a ³/₈" hole in the foot bracket, adjacent to the large hole that accepts the air cylinder. The ³/₈" hole should be on center and ¹/₂" from the edge of the foot bracket. The foot bracket is attached to the air cylinder using a large washer, lockwasher and the supplied nut. The foot bracket is attached to L₆, L₁₆ and L₁₇ using a 2 ¹/₂" long ³/₈" bolt, two washers and a locknut.

Secure L₁₅ to the shaft of the air cylinder using a lockwasher and a pair of jam nuts. Secure L₁₅ to L₁₀ and L₁₁ using a using a 2" long ³/₈" bolt, two washers and a locknut.

A three-wire electrical cord with a grounded plug is wired through a ³/₈" Romex NM connector to a pair of white duplex receptacles in a 4" square outlet box. The outlet box is positioned in the corner of L₆ and L₇ and secured to the ¹/₂" plywood using a pair of ¹/₂" wood screws.

The solid-state relays are soldered to a mini grid-style PC board. The stamp, digital voice recorder and PC board are secured to the bottom of the other 4" square outlet box using metal standoffs.

This picture shows the 4" square outlet box with the cover removed. You can see the stamp, digital voice recorder and solid-state relays mounted inside. You can see the two nine volt battery snap connectors. The snap connectors are wired to the nine volt transformer and supply power to the stamp and the digital voice recorder.

A three-wire electrical cord with a grounded plug is wired through a ³/₈" Romex NM connector to the solid-state relays in the outlet box. The tab connecting the two sockets of the white duplex receptacle in the 4" x 2 ¹/₈" handy box is removed and the solid-state relays are individually and independently wired to the two sockets.

The 4" x 2 ¹/₈" handy box is positioned in the corner of L₂ and L₆ and secured to the ¹/₂" plywood using a pair of ¹/₂" wood screws. The 4" square outlet box is centered between the other 4" square outlet box and the 4" x 2 ¹/₈" handy box and secured to the ¹/₂" plywood using a pair of ¹/₂" wood screws.

The socket is cut from the 6' household extension cord using wire cutters. The extension cord is wired through a ³/₈" Romex NM connector to the solenoid valve.

This picture shows the 4" square outlet box on the left that contains the stamp, digital voice recorder and solid-state relays. On the cover of the 4" square junction box, you can see the momentary power-on-reset switch and the flashing green LED "ready" indicator. You can see the 1/8" phono plug from the amplified speakers that is plugged into a 1/8" phono jack in the side of the outlet box. You can see the three-conductor intercom wire connected to the K76 PIR movement detector. A pair of electrical wires corresponding to each of the solid-state relays runs from the 4" square outlet box to the receptacles of the 4" x 2 ¹/₈" handy box. The clamp light and the solenoid valve are plugged into the 4" x 2 ¹/₈" handy box.

The flow control valves are wrapped with Teflon tape and threaded into the air cylinder. The ¹/₄" NPT x ¹/₄" compression fittings are wrapped with Teflon tape and threaded into the output ports of the solenoid valve.

The ¹/₄" brass nipple is wrapped with Teflon tape and threaded into the solenoid valve. The solenoid is positioned in the corner of L₁ and L₇. A hole is drilled in L₁ to accept the ¹/₄" NPT female quick-disconnect fitting. The ¹/₄" NPT female quick-disconnect fitting is wrapped with Teflon tape and joined with the ¹/₄" brass nipple using a ¹/₄" brass couple through L₁. The solenoid valve is secured to the ¹/₂" plywood using a pair of bolts, washers, lockwashers and nuts.

The ¹/₄" NPT x ¹/₄" compression fittings in the solenoid valve are plumbed to the flow control valves in the air cylinder using ¹/₄" polyethylene tubing.

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The construction of the head and torso are based on a Terror Syndicate Monster Mud prop frame. For details on the construction of a Monster Mud prop frame refer to Steve Hickman's Terror Syndicate Home Haunter's Handbooks.

Steve advocates inserting a plastic grocery bag into the latex mask and filling it with foam insulation from a spray can. I've found that it's much easier to insert a foam wighead into the plastic grocery bag and pour a two-part expanding urethane foam in between the grocery bag and the wighead. The two-part expanding urethane foam sets up in minutes.

A pair of 3" wood screws is used to secure the prop frame to the 6" - 1 ¹/₂" angle iron (L₁₃).

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I covered the prop frame with chicken wire, but rather than apply Monster Mud to the chicken wire I opted to simply dress the torso in a plaid shirt in order to minimize the weight.

The momentum of the head and torso tend to lift the front of the Grave Jumper platform off the ground. I used a pair of 15" American Camper steel tent stakes to hold the front of the Grave Jumper platform to the ground. The hook on the top of the tent stake slips over the 1 ¹/₄" angle iron frame of the Grave Jumper platform.

The Grave Jumper is controlled by a First Step stamp microcontroller. Here is the stamp PBASIC program that controls the Grave Jumper,

jumper.bas

Refer to the Beginner's Guide to Haunting with a Stamp Microcontroller for more information on how the First Step stamp microcontroller is used to control the Grave Jumper and haunt props in general.

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