Animal, you should dig this. I am scratchbuilding a guntruck from a M 21 frame up. The only thing is, I'm not sure how I'm going to make the body panels that have rounded seams. It's going to be a 4X4, Chevy 454 powered, dual.50 cal. armed monster ala "Road Warrior" type. Has anyone ever carved a body out of wood and "cooked" sheet plastic over it? I'm thinking that's the only way to get the rounded body style I'm going for, but, I've never tried it.
Anybody got any tips?
Cuhail

Hi Cuhail,

Do you have picture of the guntruck?? I can't figure out what you're trying to make
. I might be able to give you an idea on how to make it if you post a picture of the truck

Best and happy modeling

T. Chouman

If you have a photo of what you want to build it would be easier to help you. Using very thin plastic stock can be use to make the rounded cab portions. The thin stock by Evergreen is almost paper thin and can be bent and shaped.

Sorry guys, I should of put the picture in my gallery before I asked for help. It is now in my gallery. It's just a dwawing, so, let me slide a little on the art critique.
Cuhail
P.S. Thanks for the help!

er...this?....hehe

What part do you want to carve from a solid block?....there's nothing here, your drawing, that sheet styrene could not be used to frabricate....check out http://www.guntruck.com/ or http://talalchouman.com/ or some searching on joe wallace's webshot site, http://community.webshots.com/user/wallace1212-date...could'nt help you with, or, Animal's site of projects.....http://community.webshots.com/user/gtadw or Cliff's place....http://groups.msn.com/armorama/newgmcs.msnw.

Carving from a solid block is not a bad idea, but, I can't think of any body on this site that builds the main body of a vehicle by carving a block and "coating" with vac-styrene method..4. Buy some more sheet styrene and get to work...you have a wonderful design to build on...heck if I ever get the time around my house full of kids, I may even try to build it myself....need to get some rivets though or change to a welded joint between seams.

Good luck and keep us posted with your choices...

Judging by the lower view, which I think is the top, the very top portion is curved in at the front and back, but again, nothing that can't be done with styrene. You might carve your wood for these two contours then form a sheet of styrene over it, then remove the styrene and transfer it to the model.

Hi Cuhail

I think I know what you're trying to do. The best way is to use basswood or REN Shape or other material that you can shape first then vacuum form styrene on top of it. Another way is to use a thick styrene, for example for the hood on the truck, use, let say .125" thick styrene sheet, file and shape the edges with a file then sand it until you get the rounded shape. You can do the same thing at corners where two plates meet at 90 degrees, glue the 2 plates then file and shape the corners.

I hope that's what you're tying to do.

Best regards, and happy scratchbuilding

T. Chouman

AHHH, very perceptive guys. First, let me apologize for the rough drawing, I sketched it out and scanned it really quick ( by my standards) and it's just a rough drawing, not an actual plan of building. Second, yes I was thinking of (sorta) vac forming the front end/ hood area because I want it to be a modern body shape and not all angles and rivets. I was thinking of carving the front hood/fender area out of basswood or the like and "oven forming" the plastic over it. I've never done this kind of thing before and I don't have any vacuum forming equipment, so, basically I'm asking for help with the "oven forming" process if there is one.
Thanks to all of you for the other ideas too, I could do it with cutting sheet plastic and sanding round edges to it, but, I'd like to try softening plastic over a carving.
Also, thanks for posting that AWFUL drawing I did! :-) :-) :-) :-)
Cuhail

There's a Article in the May 2002 issue of FSM on vac forming @ home.

Nice project . The best method for carrying it out would be by trying. Your way of thinking softening plastic over a carving is good to me but i dont know about accuracie and uniformity of bends and all these... Good luck

You can actually make a home-made vacuum forming machine pretty cheap and easily. I did it a few years ago myself (read about 10). Take a small metal loaf baking pan, a section of heavy metal mesh (I actually used plastic mesh ,but would use metal if I did it again), some PVC pipe, and some pieces of "L" shaped aluminum. The bread pan is your base. Cut a hole in the side of the pan that will accept a piece of PVC pipe that is the size needed to hook up to your vacuum cleaner hose. Epoxy the PVC to the pan. Next, use a couple pieces of 1/4 inch bass wood going across the inside of the bread pan with holes drilled in them to allow air flow. These will be your internal bracing so the metal mesh doesn't collapse into the pan when the vacuum is applied. Epoxy them in as well. Now epoxy the metal mesh to the open top of the bread pan. You should now have a bread pan with PVC pipe sticking out one end, wooden braces inside, and topped off with a mesh top. The vacuum chamber is complete. Now you need to make the frame to hold the plastic. Use the 'L" angled aluminum, bend it into a square just big enough to fit over the meshed top of the chamber. You need to make two identical frames. Once these are completed, the two frames need to be held togeteher, drill holes through both frames and place screws with wing nuts to secure them. The plastic sheet gets sandwiched between the two frames. Your vacuum machine is now complete. To use it, simply carve your master and place it on the mesh. Take your plastic sandwiched in the frame adn heat it over the stove till it visibly droops in the frame and bows down. Turn on your vacuum and quickly transfer the plastic in the frame from your heat source and bring it down over the master on the vacuum machine. The vacuum will pull the plastic down to the mesh and around your master making an exact copy of it. It is pretty easy to do. Here is a photo of the machine I built.


Hope this helps.

Neat vaccuum-forming rig... there's worthy of an article in and of itself, IMHO.

I don't know if this will help, but here goes anyway...

After you carve your basic shape out of wood, you lay the styrene sheet on top of it and use a heat gun (like the kind they sell to strip paint) to very slowly heat up the plastic so the it forms over your mold.

where is guntruck in this discussion? I'd have thought he would be the first and foremost person in this discussion?

My purpose here on Site is mainly to support operations behind the scenes. I feel no need to dominate any discussion or to "flex" when it comes to proving I might know more than the next guy when gun trucks or other subject matter comes up. I think it is fun for the other members of our site to jump in there and participate - without me always having to insert a word in edgewise.

Everyone who knows me hopefully knows my experience and knowledge level. There's no need to "prove it" in every thread, is it? That certainly wouldn't be a "fun" forum would it? I answer the questions when they come my way - and most of them come privately - that's all.

Gunnie

Boatswain, that's the idea I was looking for!!! Brilliant! I don't know why I didn't think of that, but, that's the one I am going with...I think. I'm also thinking of using thin aluminum flashing and bending and hammering it out and then using sheet plastic to do some hood scoop type action. Thanks.
What do you think Gunnie???

Sounds ambitious. I've done the same in the past, only using .010, .020, and .030 thicknesses of lead foil sheet. It made for a 'harrowing' experience because the lead sheet is so malleable - but - it responds to "wear and tear" readily. You should share some pics of your progress - this is gonna be very interesting...

Gunnie

O.K., it's been a few days of work now, I think it is coming around to good things. The frame, suspension and engine are finished and as the glue dried on the transfer case I installed the gas tank and some of the hosing. I scratch-built the radiator and when you see the upcoming photos of the 454 Chevy BIG block, I think you'll be raising an eyebrow!
The rear suspension is a spring shock and traction bar get up and I'm hoping to come across a bigger tire and rim set that fills it out a bit more. I'm using the front tires from a Tamiya Halftrack M21on the driver wheel rear end gear box of that same M21 and they dont quite have the width and tread you would think to see on such a vee-hiclke.
I'll have photos as soon as I get the setup and my buddy over with the Digital.
I also came up with a bit of aluminum .10mm thick flashing for free. Being an associate with the fine company of The Home Depot, I come across many things slightly damaged and unable to be sold. We write them off and normally throw them away, except I am a scale modeler and a pack of 3x7 .10mm flashing squares with all of them having one bent corner, means I get to take it home. I'm thinking to carving wood into the shape of the body panels and forming the aluminum around it with a small ball peen hammer and soldering the joints as I go. Don't worry, I'll take lots of pictures!
So, If anybody has any Phat tires and rims for a heavier style truck, lemme know!
I'm not at all good at posting pictures on the threads, but, I am good at posting pictures in My Gallery so, if someone who is good at thread pix can post for me when I holla "help", I'd be much obliged.
Keep an eye out, Cuhail

Alright! I've gotten some appropriate wheels and tires. It seems that my favorite hobby shop in Mundelein, Il., has gone through their stock room and found a Tamiya British Quad Gun Tractor laying around. They brought it out and marked it 25% off just in time for yours truly to pay just $8.99 for it! I brought it home, ripped it open, pulled out the wheel sprue and voila... my guntruck now has bit chinnn big tires!
Pictures soon!
Cuhail

Good deal we are looking forward to seeing some progress photos of your beast.

I GOT PICTURES!!!
:-)
Check out the Guntrucks! Thread for "SB Guntruck update"


Cuhail

The main problem with Bo'sun's idea is assuming that sheet styrene will just soften and lay over the underlying mould.

It generally won't.

Having vac-u-formed a lot of parts over the years, the edges of melting sheet styrene will almost always start to pull themselves towards the centre of the sheet as surface tension in the material tries to pull the material into a sphere. Without an edge frame the material will thicken at the edges as it is heated (by as much as 2-4 times, depending upon how thick it was to start) and then wrinkle and warp, not laying onto your mould at all. If you heat it actually to the melting point it will run off the mould into a stinking puddle.

Vacform is by far the best way to make such parts, but another might be to make a positive master, cast a negative master out of resin, spray it with mould release and push-cast the shapes out of epoxy putty. You can then get wall thicknesses as thick or thin as you like and selectively thicken up parts for better structural rigidity. Use a putty that is soft before it cures (i.e.NOT Milliput or Knead A Tite. A+B is good.) If you have used the mould release properly, then even if you screw up the first casting, you can make another, taking special care in the areas you messed up the first time.

Now this method will work, but you won't be able to get parts with seruious undercuts out of the mould. For hoods and body panels, this should be OK. If you need parts with significant undercuts, then latex or silicone rubber moulds can be used. Watch out for latex moulds, though, they shrink about 5% which is enough for parts to not fit correctly where the master fit just fine.

HTH

Paul

I think I'm going "real thing" and using a form, a ball peen hammer and some .10 aluminum flashing. I want to do a whole engine compartment (wheelwells, firewall and crossbracing) out of aluminum too. I'm not too worried about thickness as it will be "armored" anyway. There will be some soldering, some filling and a lot of sanding, but I want to have a good time and this process will be that.
The process you've described was well put together and I followed your procedure and plan to print this thread out so I always have it!
Thanks and welcome to Armorama!!! Me thinks you'll fit just fine!
Here to help AND to be helped

Cuhail