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MANTIS BUILD
(My 1st time doing a build thread so any constructive criticism is welcome.)

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If you want to see better Pictures, I have most the same information on a Flickr "Phlog" Album:
https://www.flickr.com/photos/he1mut/albums/72157660113270843


BUILD MATERIALS USED:
Skeleton – 1.5” PVC pipe and associated “joints” (1/2” pipe for mockup, 3” pipe for “eye sockets”). Metal pipe for spine reinforcement.
Cladding- 4 mil corrugated plastic sheets.
Arm spikes - ¾” Neoprene sheets
Fasteners – ½ and ¾ inch self tapping screws. Zip Ties
Eyes – Fire-n’-Ice lights under 10” street lamp covers.
Mandibles – Nov 1 Halloween City Ninja weapons
Antennae– 9 gauge wire clad with thin plastic water pipe.
Leg anchors – Flexible Flyer ground anchor kit (CANNOT beat this), eye bolts, cable latches


CONCEPT / PLANNING AMOUNT of MATERIALS:
NOTE: In general the following could be done with different methodology on paper. I use CorelDraw because of familiarity. To avoid math induced headaches, I go full scale in the draw program.

Place an “average Joe” for scaling purposes for the rough sketch.
After sketch is complete, angle the limb sections allow use with standard PVC elbows (22°, 45°, and 90°).
Determine all the dimensions using various lengths of rectangles (rectangle are 1.5” wide to match 1.5” diameter PVC).

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After determining (and labeling) all the lengths, Stack the rectangles to get as few 8ft “sets” as possible.
This will give the number of 8 ft lengths of PVC to buy.
Get a count on how many joining sections (elbows, “T”s, etc.) are needed.


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1/3 SCALE MOCKUP - PLANNING & BUILD
NOTE: IMO, This is a CRITICAL phase for making a very large scale construct!
It would be almost impossible to tweak poses on something 12 ft tall.
Also if the mockup is not structurally sound, then you know the full scale version is doomed.

I went with 1/3 scale because ½“ is a standard PVC diameter.
Make a copy of the material lengths in the draw program and reduced the scale to 1/3.
Re-measure and re-label the new lengths. Re-stack the components to figure out the minimum 4ft PVC stock required.

Okay, finally building SOMETHING!
Cut all the lengths per the labels on the concept page.
I label each length (leg – bottom, etc.), It is REALLY easy to mix these pieces up.
Construct and pose the concept to match your reference.
Take pictures and bring them into the concept file to see how closely they match. Then tweak and repeat as needed.

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When I know I’m happy with the skeleton mockup I used cardboard to create the mockup cladding (no photos of this part –sorry)
NOTE: Weight is a big concern so to minimize material , my cladding are mostly single pieces, folded and bent into shape as simply as possible.

After finishing the mockup cladding, lay each cutout section out flat and take measurements.
Make rectangles of these dimensions in, scaled them up 300% , and arranged them together to best fit into 48” x 96” areas (the size of the plastic sheets). This gave an Idea of how many sheets to order.
I was not sure that I could bend the plastic sheets the same way as cardboard so I ordered extra to be safe.


BUILDING THE FULL SCALE SKELETON:
After cutting/labeling the 1.5” PVC as required, put together the “spines” (separate at the waist for now) as well the six pairs of 90° elbows.

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Best-guess adjust the angles of the 90° elbows to match the mockup. Add leg portions a pair at a time. Measure the distance between the ends of the matching leg portions from the mockup. Then calculate triple that length (we’ll call it “3x”). Evenly turn the full scale leg sections until they’re at the “3x” length. Add 45° elbows and the next 2 leg sections. Measure and “3x” the next measurement from the mockup, and adjust the full scale section like before.

Shown in the picture: I used a length of PVC as a centering point.

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Repeat this until the four bottom legs fully assembled. Set the bottom section upright and compare it to the mockup.
EDIT- 12-22-15: I screw the 90° joint sections in place BEFORE attempting to stand it all up. It would collapse otherwise.
Tweak until it matches the mockup OR until you say YEAH BABY!” Screw all the pieces together to maintain the pose. I didn’t need screws in the lowest leg lengths (no angle to maintain).

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Follow the same methodology to assemble the full sized arms. I wasn’t sure how I was going to do the head yet, so I had a “place setter” the matched the rough dimensions.

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Slide upper body onto the bottom section, and see what you got!
I was just glad it stood under it’s own weight at all!

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For reassembly purposes, label EVERY section. Mark how each limb mates to its elbow with unique matching symbols and line-up points. Circle the drill points.

Markings:

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ADJUSTMENTS (Damn you –gravity and physics!)
The spine immediately started sagging. A 6 ft length of ½” metal pipe was handy to reinforce that section.
ALSO: At full scale, the proportions just didn’t seem right - I decided to take about 8 inches off the lowest 4 leg sections and add 6 inches to the forearms.


THE CLADDING (and Head Build).

Up scaling from the cardboard markups:
Mark 2” horizontal lines on the mockup.
Mark 6” horizontal lines on the plastic sheets.
Measure and write each horizontal dimension from the center line at the 2” inch intervals.
Hash mark the “3x” dimension from the center point on the plastic sheet at the 6” intervals.
Recreate the curve of the mockup using the hash marks as guide points.

This is the initial cutout of the wings:

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With the rest of the cladding I followed this method more and more loosely. The plastic behaved pretty differently than the card board.

NOTE: The best way to create curved surfaces with this material – look at how a globe is constructed. Cut symmetric wedge-like gaps, with each edge resembling the desired curvature (leave extra material for fastening flaps) and mate the symmetric edges. I’m sorry if I’m not describing this clearly - if you look up “globe construct” you’ll see what I mean.

The abdomen was done with this technique

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The Arm Spikes: simple triangles with a “lip section” that holds them in place:

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HEAD V 1
The plan was to use prismatic “disco lights” in these yard fixtures. All housed in 3” PVC. Alas the bulbs did not fit.
Head shots:

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This weird piece of scrap (along with some mean brows) is the head cladding.

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The cladding is mostly done. Some minor refinements after this, then paint.
If I had a do –over, I might have tried shaping the cladding with a heat gun and worked on ways to hide the zip ties – Such is life.


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UP NEXT - Paint, Trial Build, DISASTER, Final build.
 

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Wow! This is really awesome! Thank you for taking the time to detail this project as I know I'm picking up several good pointers! Now off to part 2. :D
 

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Discussion Starter #9
Bob, where did you buy the bulbs for the eyes?
Hey Chris
Do you mean the covers?
Those are acrylic street lamp covers. I shop around each time. but you can see whats available on this site:
https://www.lamppostglobes.com/Round-Replacement-Globes_c_15.html
and here http://www.superiorlighting.com/Plastic_globes_Round_Plain_Lip_s/238.htm
I used 12" for this project, but probably could have gone smaller.
Using 8"for the "Prey-MAN-Tis stalkaround.
For a "mounting sleeve" I cut a 1/4" slot into 3" PVC and tapered the edges.
 
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