Making miniature structural shapes C-channel, I-beams, angle

[BrianS]

For an upcoming project I would like to make some miniature structural shapes. For example an I-beam (or RSJ) 0.321in x 0.714in x 15.5in long. The project needs some other sizes too. But my question is what would be the best/easiest process to make these shapes that could be accomplished by a home shop?

Should I get stock and machine out material from both sides with a ball end mill to make the I shape? If I do it this way I'm afraid that the stock might warp badly. Especially if I try to make mini C-channel or angle and mill from one side only.

Perhaps instead use 3 pieces of flat stock and try to silver solder it together? With this idea i'm afraid I won't get it square and would probably have to heat/solder it in sections down its length because I only have a MAPP gas torch. Not sure what this would do to the integrity of the entire joints.

Or maybe someone has a better idea on how to go about making stuff like this? Oh and, I'm undecided on whether to use brass or steel too. I'm leaning toward steel for its strength and cause it's cheaper. If there is a good solution but with would only work with Aluminum I could use that as well. I'm just in the planning stages at the moment. Any suggestions?

 

[shred]

Do you really want to make them? Mini structural shapes are available off the shelf in a variety of shapes and sizes. I suspect they make them commerically with a rolling mill or extrusion process of some sort.

 

[BrianS]

Thanks for your reply. Yes you are right I would rather buy them (if the price was good) but I'm afraid the sizes I want aren't standard an aren't produced, except for maybe a special order if at all. I figure a special order would be really expensive. So that's why I'm considering making them. For example I found 1/8" x 1/8" or 1/4" x 1/4" C channel in Brass but for my project I want 0.286" x 0.143" channel.

 

[Mainer]

I think you are looking at a Difficult job. No matter what approach you use (milling or fabrication by soldering) I see a great chance of warping.

How much strength do you need? Soft soldering might be good enough, which would simplify things slightly. Brownell's www.brownells.com sells some high-strength soft solders.

As far as milling is concerned, if you use steel you should stress-relieve it first or it's bound to warp. Personally, I think using steel would just be adding to your difficulties if brass or aluminum are strong enough. Brass would also need to be stress-relieved, I expect, if you milled the shapes out of solid. Not sure about aluminum, or how to stress-relieve aluminum.

 

[mklotz]

Perhaps you can tell us a bit more about what you're trying to build?

Making your own structural shapes is both time-consuming and tricky (see other comments about distortion). Since miniature structural shapes are readily available, perhaps a bit of project redesign is in order so that standard shapes can be used. With more information about your project it will be possible to make that determination.

 

[potman]

This may be blasphemy but do your parts have to be made of metal?
Could plastic or wood with a little paint work just as well?

Just a thought.

earl...

 

[Kermit]

Exactly, Several types of metallic epoxy are available that are as strong as aluminum.

You could make ONE piece the size you need and use that for making a mold. Simply pour up as many I-beams as you need from your mold and some aluminum epoxy.

 

[Debian]

As a civil engineer, I'm also very interested in this kind of models, structural shapes. Just as Brian, many times I asked myself how it would be possible to machine such shapes, to reproduce one or most of the structure I usually project for my work, by steel (S355J most of all).
I would gently ask to mklotz and shred where they found those kind of model shapes over the internet, I just made a search on google without any results, just the Plastruct, Inc. but they are in ABS and I would prefer steel.
Best regards

Paolo

 

[mklotz]

Paolo,

Here in Los Angeles, I find the miniature structural shapes in the K&S Engineering displays in the hobby/model shops that cater to the model railroading and RC car folks.
You might want to explore similar shops in Italy.

One internet source for small structural shapes (and many other things of interest to folks like us) is Small Parts. Their URL is:

http://www.smallparts.com/?gclid=CNzbr8_syJcCFRykagodsmoShQ

They tend to be pricey but I've always been well-pleased with everything I've bought from them.

 

[BrianS]

I might experiment with the Al expoy idea. Sounds like a good one. I don't know of any "pourable" ones though. Do you have a specific one in mind? Is it safe to use a silicon rubber mold? Is that the type you had in mind?

Thanks for all the suggestions so far..

 

[stevehuckss396]

For example I found 1/8" x 1/8" or 1/4" x 1/4" C channel in Brass but for my project I want 0.286" x 0.143" channel.

Maybe you could get some 5/16 X 3/16 or some 3/8 X 1/4 and modify rather than start from scratch.

 

[BrianS]

Steve,

I thought of that but couldn't find that size anywhere.

 

[stevehuckss396]

Steve,

I thought of that but couldn't find that size anywhere.

DONT LAUGH!!

Ever think about building a miniature brake press and bending your own. I am thinking of designing/scaling down one for some of my own needs. I will soon need to bend sheet brass into radiator tanks. If you build one, make two and send me one.

 

[shred]

I was thinking of K&S (www.ksmetals.com) and www.specialshapes.com, though they both mostly deal in brass & copper shapes. There are probably others out there as well.

 

[Debian]

Thanks for reply, I saw ksmetal and specialshapes sites, but they don't have any clear image to look at. Btw I'll keep searching on the net.
All the best,

Paolo

 

[Kermit]

I just got one of those Lightbulb moments.

I saw an ad on the TV for one of those "Playdough" brand shape factory or something like that.
IDEA:
A hopper with an arm which presses down on your aluminum putty and EXTRUDES the I Beam shape like a long piece of spagetti. A metal hopper and plate that fits inside; use an arbor type press to force the thicker heavier epoxy through your mold plate.


You just have to cut the profile shapes to push the epoxy through.

My ealier suggestion of "pouring" would only work for the low temp casting metals I suppose now that I've had more time to think it through.

Anyway, I KNOW this method could work. Just look what it's done for Playdough sales! ;D

Kermit

 

[shred]

There's some notes on making miniature structural shapes at the end of this useful document:

http://users.bart.nl/users/summer/16mmngm/Articles_htms/ColinBinnie/CBWJ.htm

 

[John S]

I just got one of those Lightbulb moments.

I saw an ad on the TV for one of those "Playdough" brand shape factory or something like that.
IDEA:


Kermit

I was thinking along the same lines when you posted.
Build a set of rollers with the shape in that you want, just like a mangle wringer.
feed some plasticine or similar thru and lay it out face up on a board and push with a straight edge to make sure it's straight.

Spray with silicone release or similar and cover with that casting rubber stuff.
When set use this mould to cast your liquid metal into. you may even be able to put some liquid metal in then three strips or real metal and cover over to get a stronger casting. ????????

 

[Kludge]

DONT LAUGH!!

Laugh? Us? You'll never find a more serious group than the residents of HMEM. I think a sense of humor is against the rules or something.

Ever think about building a miniature brake press and bending your own.

This is a cool idea. What's better is that I think a length of piano hinge could be coaxed into providing a ready-made hinge around which you could make it. Or weren't you thinking that miniature?

BEst regards,

Kludge

 

[stevehuckss396]

Or weren't you thinking that miniature?

BEst regards,

Kludge

I was thinking something like 12-16 inches in length. Maybe make some blocks with 45 degree angles and have a box & pan.