An easy brake?

[mhorowit]

I have to build one of the ribs that goes in the rudder.
I have access to a brake about an hour away, so for practical purposes, only on the weekend.
Bending .020 4130. 18-24" long.
I can see how to do it, but my solutions usually are too complicated.
Suggestions?

[jdoran]

Re: An easy brake?

Mike,

Why not buy one?

http://www.grizzly.com/products/g5769

If the cost is steep, you could charge a modest fee for small jobs and it would pay for itself.

John

[Mark Julicher]

Re: An easy brake?

Mike,

Make a buck out of a piece of 3/4 inch MDF shaped like the center of the rib. Sand or rout radiused edges on the buck.

Mount the sheet metal blank to the MDF with a couple screws. Use a rubber mallet or a slapper to bend the edges of the sheetmetal down over the edge of the buck. Tale it slow and lay it down evenly. Use fluting pliers on the bent edges to make the rib lay flat as required.

This is not difficult with .020 metal.

[Len Petterson]

Re: An easy brake?

Here in Canada the TSC stores are sellning a small brake I think it is 30 Long. You be amased what they have what is usefull in aviation.(;f
Len

[mgold]

Re: An easy brake?

www.zena.net/htdocs/welders/projects.shtml try this site and google metal brake plans. I built a 4' one I can't find the plans or site yet.

[Sloanlow]

Re: An easy brake?

for that application, clamp a peice of hardwoood on a table then take a peice of barstock and lay it alongside the metal tap it against the 020 the hardwood turn over repeat, trim and fit.

[mhorowit]

Re: An easy brake?

for that application, clamp a peice of hardwoood on a table then take a peice of barstock and lay it alongside the metal tap it against the 020 the hardwood turn over repeat, trim and fit.

Thanks, but I'm thinking I don't know how many bends or how often I'll need a brake, so I'm looking at the on-lines plans mentioned earlier in this thread - Mike

[mhorowit]

Re: An easy brake?

www.zena.net/htdocs/welders/projects.shtml try this site and google metal brake plans. I built a 4' one I can't find the plans or site yet.

Mitch - I'll try it; opportunity to use my newly acquire welding skill.
I do have a question:

The 'clamp' bar; is there any reason that couldn't be a 1/4" x 1" x 4' length of bar stock instead of angle iron?

In the plans we see the angle iron clamp bolted to the stationary part of the brake. but the bolt doesn't seem to be going thru the angle iron. Does it appear they welded a length of bar stock to the inside of the angle iron and drilled thru the bar stock? - Mike

[mgold]

Re: An easy brake?

I use angleiron and on the backside I welded a triangle for braces
and drill holes in the end to clamp in place
there no reason you can't use the flat stock . so I done some mods.

[mhorowit]

Re: An easy brake?

Did you have any problem positioning the hinge?
I can line them up by using a 36'' 1/4" rod running thru the hinge holes, but where to position that rod is my question - MIke

[mhorowit]

bending metal

Got the brake built and am practicing on scrap sheet metal.

I've set the clamping bar about 1/8" back from the fold, and I set the intended location of the bend (the line I drew on the work) over the fold. When I bend the metal, the line ends up about 1/16" up the other side!, so I'm trying to figure out the allowance. I'm trying the build a piece of channel (see attached) with a floor of 1".

CAn anyone suggest how to set my allowances? The sheetmetal is .035 - Mike

[Hank Jarrett]

Re: An easy brake?

Welcome to the wonderful world of sheet metal manufacturing. What you need is a good primer on Offsets and Setbacks. When you bend the metal the bend doesn't end up where you expect because of the stretch and compression of the metal in the bend. I just looked for my old book and couldn't find it but it is pretty much standard stuff for sheeetmetal guys. The guys with a lot of experiance can come amazingly close just by eye.
To do it by the book (and not waste a LOT of metal learning) you will enter the tables with the type metal, thickness, heat treat and angle of bend. The tables tell you how much you have to set back from the bend and even how far past the final bend you have to go to allow for spring-back. It can get REAL challenging, and kind of frustrating when you do all the work and the part isn't right. That is usually followed by "Ole Crusty" (the guy from the shop who was bending sheet metal when the Dead Sea was just REALLY sick) grabbing a piece of the material and saying "here kid, just do it like this" and making a perfect part just by eyeball.
Go find the book, of better yet, FIND CRUSTY. I have a feeling he will look a LOT like Forrest.
Hank

[mhorowit]

Re: An easy brake?

Hello Hank - There is something in 43-13 I believe - I was hoping for a non-complex way to do this, some rule of thumb. (sigh) I was going to learn about sub-net masks and sub-netting this afternoon, but I see I'll have to reset my priorities; perhaps a quick GOOGLE - Mike

[mgold]

Re: An easy brake?

vansairforce.org/ left side at the bottom. build you own tools click on it. this the one i build sorry it took so long. you know flying honey-dos. but she cute. put a new t-wheel on the back. maule tandura it is real great. sounds great no rattles.
haha!!!!!!!!!!!

[VictorBravo]

Re: An easy brake?

Mike, the "setback" is simple. R+T, meaning the radius you are bending plus the thickness of the metal. If you are bending .020 metal around a 1/4" radius, then mark a line .270" from the edge of the flange on the flat sheet. Put this line directly under the clamping bar at the very start of the radius.

There are good simple drawings of how and why this works, available in any shop manual. Since you went through the trouble to build a brake (I'm jealous!), the invest $10 in an aircraft sheet metal book.

Now that you have built a brake, you'll want to use it, and then you will use it, and after that you will need to rivet the metal you bent. Find a surplus outlet or whatever, and get a pair of Cleco pliers and a couple dozen Clecos, and get a starter rivet gun and set kit . You can use a cheapie "Air Chisel" ir "Air Hammer" from Harbor Freight, but the pros tell me that a real rivet gun is better. Having the ability to rivet well and form sheet metal well will make you a very desirable friend to have around at the airport, which will mean you get a lot of desirable friends with other skills at your disposal.

In short, you have made a good decision to become skilled at welding and metal. Follow through and many other interesting projects will open up. The guy with the metal airplane who needs a skin repair and has an extra instrument you need... the guy who needs a weld repair on a Champ fuselage who happens to have a couple of rolls of Stits fabric, etc.