Heavy forearm rigging help please: G1 Megatron's cannon arm

Heh. Thanks CB2001, I'll be sure to look at backyard FX's other videos. Neat to see others' methods!

Rnc88, the thought for adding the weight to the left arm is so that my spine has equal weight on both sides of my body. I hope to have it less than 5lbs, but am using that figure as a worst-case. By the time I wear the outfit I'll be 38...and lets say along with wisdom, the body gets more sensitive to ergonomic irregularities! I have the muscle to handle the weight, but know from carrying a 4L milk jug 6 blocks that my body demands a balanced load. I'm actually changing my exercise routine for more bicep & deltoid work. =)

We'll see how testing goes with the twist-prevention angle. Hopefully the cannon will be light and be managed enough with foam. I have it in mind to make the bottom of the forearm a double-close system; I'll first put my forearm into the molded space, strap it in tightly, then close the outer layer, sealing with Velcro.

I'd been hoping to stick with double-thickness cardboard, but we'll see if that is appropriate for this part.

I'll be sure to post results here!
 
Marthony said:
Heh. Thanks CB2001, I'll be sure to look at backyard FX's other videos. Neat to see others' methods!
Click to expand...

You're definitely welcome. BFX and Jake are two excellent examples. To be honest, Jake's done a lot of prop builds using foam and other materials. I'm glad to help you out. That's what's great about the RPF. A lot of resources at your fingertips. :)
 
Okay! =)

There have been a number of design edits & progress. I've started construction, and have one elbow joint assembled. I'm using 6" turntable bearings from Princess Auto, 90 degree angled aluminum hacksawed & drilled to spec, T-shaped steel brackets, 10-24 bolts & locking nuts for the free-pivoting joint, and 8-32 nuts & bolts for connecting the brackets, T's & turntable bearings.

Next up, I need to buy some 10-24 thread-ready rods to build the inner structure of the arms. They will go from the turntable bearings to a simple plastic/plexiglass plate (not yet sourced). Next, I need to cut & drill scrap aluminum rectangles for reinforcement as the build develops. Later on, the cannon will get attached to the forearm structure's reinforced rods.

Here are some pics:
Arm structure-
http://i1276.photobucket.com/albums/y470/Martaxus/ForearmampUpperArmstructurev42_zps231f3eb6.jpg
Arm to cannon structure-
http://i1276.photobucket.com/albums/y470/Martaxus/Forearmtocannonstructure_zps34ff3631.jpg
Elbow joint (will move pivot point to hole closer to forearm to make for longer costume forearm length)-
http://i1276.photobucket.com/albums/y470/Martaxus/Elbowjoint2_zps41cdf9e7.jpg
Joint on arm (pivot not yet corrected)-
http://i1276.photobucket.com/albums/y470/Martaxus/Elbowjoint1_zps0b103b94.jpg

So whaddya think? :D
 
I think it's a bit over-engineered, honestly. I think you'll have issues with the movement and stability if you run the support system all the way up to the shoulder. I think you'd be better off running a rod down the forearm and attached to the hand.
 
I'm not sure I understand? The upper arm's structure will consist of the 4 rods plus a couple cross-braces to keep it from twisting; otherwise I plan to fill the available space with foam. I want the rod structure to remain so the frame of the arm supports weight well.

I'm not clear on how a rod down the forearm is different than the 'spoon' in the palm concept?
 
It works! Even without the upper arm anchoring where the elbow joint is to pivot, or the locking nuts holding things in place it handles well. Eventually there will be padding inside to keep the arm centered within the build.

http://i1276.photobucket.com/albums/y470/Martaxus/Lowerarm_zpsd2cae39b.jpg
http://i1276.photobucket.com/albums/y470/Martaxus/Armprogress2_zpse6fb1582.jpg

Next, upper arm! This will be a touch tedious as there's some improv design to be done; the arm will end up being vertical, but a person's arms hang out at a slight angle. My upper arm will be concealed to be at an angle within the shape while the shape stays robotically vertical. As soon as that is done I'll be able to dial in on where the elbow joint is to be, and reinforce the structure.

Then...cannon time!
 
Progress is coming along, though slowly. I've just over 2 months left..!

It's been a process building the upper arm in such a way that it will sit properly on my shoulder, with the exterior almost vertical for effect, and then also make a harness system from an old backpack to keep the arm in place while worn. With the elastic-nylon-Velcro straps ending in backpack clips, the upper arm is self-adjusting.

Now that I'm happy with how the arm wears (other than cutting down one of the slats that is a bit tight against my bicep) I'm starting work on the cannon. It's been interesting estimating measurements & proportions based on the original cartoon, but between that and the 'forced' details of the forearm (just over 7" long, 6" wide) I am able to proceed.

Here is how the arm looks at this moment. As time permits, I'll drill more holes in the vertical supports; there will be cross-pieces running underneath the imaginary 4.25" wide poster tube, and 90 degree braces on all connecting parts to support the tube. For the forward part of the cannon (after the 'box' center of the cannon mounting) I'll transition to a 5.25" poster tube. I've yet to choose parts for the larger rear of the cannon, but may use parts of plastic buckets.

http://i1276.photobucket.com/albums/y470/Martaxus/Startofcannonbuild_zpse74011e4.jpg

(Of course, I will use hot glue to secure the staples on those straps from biting into things or coming loose)

The cannon will be huge...the 'base' of the cannon will be almost 6" before the 'box' and tubes begin. On the plus side, this will make it easier to rotate it around the upper arm.

Remember: If during your project you haven't stopped to say 'this is insane', it might not end up being awesome. =)
 
This was the model I threw together to start on the one I'm working on. Total length is just under 3 feet, give or take.
Final_Version01.jpg
 
Very nice! I plan to make the center section a hexagonal shape as well. Otherwise, I plan to have the top & side details further forward, and the bottom of the center will be as high as Megatron's arm is (in my case, 6")

I'm interested in exactly how you plan to build this. Also, are you planning for this to be only a prop, or will it be part of a costume?
 
All the round sections are built on rings I cut at the drill press and bandsaw, spaced apart with intercostal pieces, and then wrapped in plastic. The center section was built around a tube using plastic and some basic techniques.

It's as light as I could feasibly make it, and still heavier than I had hoped.

As of now, it's a stand-alone piece, but I have a removable plate in the base of it that I can unbolt and modify to allow it to be worn. The plan there is to make a separate forearm part that the cannon hooks onto, most likely using something like we do with proton wands/packs.
 
So it is built? Please give a link to any thread that's covered this. If it has yet to be written, please post a note here later so I may subscribe to yours; I'd like to see as much as possible.

I'm hoping my cannon won't exceed 5lbs, and that the arms will turn out to be the heavier part; I've only two more small pieces of aluminum to add to this, with the rest being mostly poster tubes. How heavy did yours end up?

An element of this I've yet to address is the transition from the 4.25" tube to the larger size at the back of the cannon. On my Optimus Prime toy rifle I used sections of plastic pop bottles, but none are large enough for that to work here. Any suggestions please?
 
 
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