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On 10/15/2002, Eric R. "Tex" Terrell wrote:
"Mark, have you considered the multistage option? After glancing at your Burt I think a 3-stage design would be optimal. What do you think? I think it would be majorly cool to add Burt's head to NORAD's database of space junk."
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Evil Bert Flies Again and Again and Again


Click [HERE] for details on the Evil Bert Drag Race!

This is a classic example of what happens when the judgment of grown men is impaired by too much coffee and too little sleep. Click HERE for backgound on how this wacky idea got started...

Our goal is to make our GHS 2002 Team Project a Bert drag race - four Bert puppets, each flying on a two-motor cluster of Aerotech G motors.

Click HERE to download a RockSim 7.2 simulation of the Bert rocket.

Construction Instructions

Parts List

1 Bert Puppet
1 Pair shoes for 18" doll
1 Pair really small trousers
1 3" coupler (2.98" x 6"; 2 7/8" internal diameter)
1 3" tube (cut to 1 1/2" long)
1 3" tube (cut to 5" long)
2 29mm tubes (cut to 11" long)
1 2.98'' x 1/4" bulkhead
2 2 7/8" x 1/4" dual cluster centering ring
1 11" x 14" x 1/8" sheet Acrylic Plexiglas
1 3" x 1.5" x 1/8" piece of aluminum
2 10-24 eye bolts
4 10-24 nuts
2 10-24 nylon machine screws
2 10-24 nylon nuts
1 8-32 aluminum screw
1 metal cable clamp
4 washers
2 #14 screw eyes (5/16" aperture)
2 #144 screw eyes
2 1" drywall screws
2 cable ties


Bulkhead and Centering Rings

Forward Bulkhead

Cut one 3" disc from 1/4" stock. This is your forward bulkhead. Install a 10-24 eye bolt in the center guide hole using two nuts and two washers for the forward shock cord mount.

Centering Rings

Cut two 2 7/8" discs from 1/4" stock. Fill the guide hole with epoxy and allow to cure.

Mark the center point of the disc and draw a line that bisects that point. Mark the center points for the motor tube holes on the line, 3/4" from the center of the disc (1 1/2" apart). Drill a 1 1/4" hole at each point.

In the forward centering ring, drill a single 5/32" hole as shown. Install a 10-24 eye bolt in this hole using two nuts and two washers for the aft shock cord mount .

In the aft centering ring, drill two 1/16" pilot holes as shown. In a later step you will install a #144 screw eye in each hole (through the trouser material) to mount the fin assembly.



Upper Torso Assembly

The puppet head is angled off-center. You may not feel this creates an aerodynamic problem, but it concerned me. I believe it can be solved two ways:

Option One:
Close Bert's mouth - use epoxy, drywall screws, sutures, whatever. This aligns the top of his head with the rocket centerline and has the added bonus of making Bert appear grumpy -- or so I thought, until Rick chose to go this path. Bert actually ends up looking rather serene (see photo, left).



Option Two:
Cut the top of the 5" section of 3" tube at an angle so that one side is 1/4" shorter than the other. The front of the base puppet head will be mounted flush with the short side edge. This also aligns the top of his with the rocket centerline.

I chose Option Two, mainly because the aged plastic of the puppet head was no longer flexible and it seemed obvious that Bert would stubbornly resist any changes in facial expression.

Mount the forward bulkhead into the forward opening of the 5" section of 3" tube (screw eye inside the tube).

Center the puppet head on the bulkhead and align the front of the base with the front edge of the tube. Drive a drywall screw through the bulkhead and into the base of the puppet head. Repeat at the back edge. (Squeeze the base to line it up - it is slightly wider than 3".) Two screws was all I felt I needed to fasten the head securely.



Lower Leg Assembly

Mount the 1 1/2" section of 3" tube flush with one end of the coupler. (This is the aft end.)

Install the two 11" x 29mm tubes in the dual centering rings. Space them 2" apart, one mounted flush with the forward end of the 29mm tubes. (This will make Bert's legs 9" long). Install this assembly in the coupler assembly, aft ring flush with the aft edge of the coupler.

Assemble the Upper Torso Assembly and the Lower Leg Assembly. Check to see that the coupler moves smoothly inside the Upper Torso Assembly - if not, then sand the coupler. (I soaked my cardboard coupler with CA and then sanded. It is now more rigid and rugged).

Align the forward and aft body sections, lift the puppet's tunic, and mark a vertical line from Bert's left butt cheek. Drill a 1/16" pilot hole on the line, through the body tube and into the edge of the aft centering ring. Then drill a 1/16" pilot hole through the body tube into the edge of the forward bulkhead.

Install the trousers.

Locate the pilot holes you just drilled on the side of the body tube and install the #14 screw eyes through the cloth of the trousers and the puppet's tunic. These are your launch lugs. (This size screw eye will accomadate a rod from 1/4" to 5/32". Use screw eyes with wider apertures if you want to use a launch rod larger than 5/32"

Next, locate the 1/16" pilot holes you drilled into the aft bulkhead and install a #144 screw eye through the fabric and into the ring. Turn them so they they are will be parallel to the center fin.



Fins

Mark the 11 x 14" sheet of acrylic Plexiglas per the markings on the template. Cut the fins and fin slots. I made the edge-to-edge cuts using several strong-armed passes with a straight-blade knife on each side; then the sheet can be flexed to break along the scored line. I cut the slots and dead-end cuts with a Dremel tool using a cut-off wheel. If you have a better way, have at it.

Drill 1/4" holes in the center fin as shown.

Align the fin slots and slide the fins together. The two cross-piece fins should extend one inch past the bottom of the large fin.

Carefully drip the CA into the end of the interlocking fin slots (after assembly) and capillary action draws the CA along the seam. If you're careful you won't have any drips and the bond will be really strong. Also, take care not to use too much or the CA will run all over your fin assembly.







Lower Torso/Fin Assembly

Position Bert so that he straddles the large center fin. The base of the coupler (Bert's crotch) should fit in the notch at the top of the center fin. The #144 screw eyes should be against the fin, one on either side. Align the upper fin notch tight against the Lower Torso Assembly and run a cable tie through the upper set of holes in the main fin and around both legs. Pull tight, making sure that the trousers aren't bunched up. Don't install the lower cable ties yet.

Mark the location of the screw eye holes on the center fin. Drill a 1/8" hole through the Plexiglas at each mark. Install a 10-24 nylon screw through each hole/screw eye and secure with a nylon nut. Trim off excess screw length.

Shape the 3" x 1.5" x 1/8" strip of aluminum as shown in the diagram to form the backplate. Drill a 3/32" hole as shown and tap out the hole with a 8-32 thread cutter. Install a 8-32 aluminum screw and washer for motor retention.

Cut holes in the soles of the doll shoes large enough for the motor tubes to pass through. Slide the shoes into place; 1/8" of tube should extend past the sole of the shoe. Stuff the toes of the shoes with cellulose insulation or similar material. Epoxy in place if you like - I didn't.

Slide the backplate into place: the tubes extend into the large holes, flush with the aft side of the plate; the top of the plate rests against the soles of the shoes. The notch should go in back (by the heels of the shoes)and the motor retention screw hole in front. Attach to the tubes with JB Weld or JB Quik Weld as the aluminum is a good conductor of heat.

Install the cable ties into the aft set of holes drilled in the center fin. Pull tight. Don't forget to tie his shoelaces.


Click [HERE] for Construction details on the Evil Bert rocket!

Click [HERE] for Background on why this even started as an idea!

Click [HERE] for information on the rocket background of the muppet's orginal creator!

Click [HERE] for downloadable video of the Bert Drag Races -- AND MORE!

Click [HERE] details on the 2002 ORIGINAL Bert Drag Race!

Click [HERE] for a frame-by-frame replay of the 2002 Bert Drag Race!

Click [HERE] for details on the 2004 Bert Drag Race, this time with EIGHT Berts!

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