Sheet Metal Forming

[51fixer]

As shocked at BW's posting such an interesting thread, I must also say that it would be really neat to build your own Airacobra in your barn using nothing but wood patterns. I know next to nothing baout metal working, so this has been a really bried but interesting inro to it...Could somebody maybe use this as a intro to aircraft metal working? What are the metals you use for sheet metal, and framing, and stringers, and such? what do all those numbers mean?

Airacobra and Kingcobra used a great deal of heavy alum extrusions in addition to sheet metal parts. Think squeezing toothpaste thru a die that would leave a L, H or T shape only it is hot alum alloy and it could be 6" or more wide by 25' + long. After that, it needs to be bent, curved or joggled and also heat treated. After that it gets machined.
Rich

[Dan K]

As shocked at BW's posting such an interesting thread, I must also say that it would be really neat to build your own Airacobra in your barn using nothing but wood patterns. I know next to nothing baout metal working, so this has been a really bried but interesting inro to it...Could somebody maybe use this as a intro to aircraft metal working? What are the metals you use for sheet metal, and framing, and stringers, and such? what do all those numbers mean?

Yo Muddy,

Here's "Aluminum 101" (courtesy Aircraft Spruce).

http://www.aircraftspruce.com/catalog/m ... uminfo.php

Good stuff if you're having trouble sleeping some evening.

[hang the expense]

Most big shops will pull the material in the "W" state and then let it"cure".This eliminates the warping from heat treating a part after forming or stretching.

[ZRX61]

I'd start looking at Aircraft Spruce's catalog(www.aircraftspruce.com) or going to the auto spectrum, such as the restoration supply places, such as Eastwood Company. They have a lot of items directed towards auto sheet metal which could easily be used(and usually is) for aircraft fabrication.

Robbie
A&P
KC2TYV

Avoid Eastwoods as just about everything they sell can be sourced elsewhere for considerably less. Half of their stuff is relabeled HarborFreight junk..

[A2C]

Airacobra and Kingcobra used a great deal of heavy alum extrusions in addition to sheet metal parts. Think squeezing toothpaste thru a die that would leave a L, H or T shape only it is hot alum alloy and it could be 6" or more wide by 25' + long. After that, it needs to be bent, curved or joggled and also heat treated. After that it gets machined.

Check w/ ALCOA, they have lots of shapes which are very very close to original factory stuff, and can be modified.

[muddyboots]

As shocked at BW's posting such an interesting thread, I must also say that it would be really neat to build your own Airacobra in your barn using nothing but wood patterns. I know next to nothing baout metal working, so this has been a really bried but interesting inro to it...Could somebody maybe use this as a intro to aircraft metal working? What are the metals you use for sheet metal, and framing, and stringers, and such? what do all those numbers mean?

Yo Muddy,

Here's "Aluminum 101" (courtesy Aircraft Spruce).

http://www.aircraftspruce.com/catalog/m ... uminfo.php

Good stuff if you're having trouble sleeping some evening.

bookmarked

thanks!

[hang the expense]

Just remember when you make your die that unless you make it out of micarta or aluminum it will not hold up in a press that has any serious tonnage.So if the part is large you are going to have to hit it again on the die you made with a fair bit of hand working or slap paddling.I am making aft bulkheads for B-17s now and the parts have some serious flat areas that will warp when heat treated.Being able to hit the part in the press again will really help in turning out a good part.It will also help to fit the part in "O" condition and drill most of the holes where the part is going to live.That when it comes back from heat treat you will have an idea where the part is supposed to fit.Its more work but you will be assured that the part will fit.

[Broken-Wrench]

[quote="hang the expense"]Just remember when you make your die that unless you make it out of micarta or aluminum it will not hold up in a press that has any serious tonnage.So if the part is large you are going to have to hit it again on the die you made with a fair bit of hand working or slap paddling.I am making aft bulkheads for B-17s now and the parts have some serious flat areas that will warp when heat treated.Being able to hit the part in the press again will really help in turning out a good part.It will also help to fit the part in "O" condition and drill most of the holes where the part is going to live.That when it comes back from heat treat you will have an idea where the part is supposed to fit.Its more work but you will be assured that the part will fit.[/quote]

Hang are you makeing some particulars parts now... Do you have a press like that?..

[hang the expense]

My press has a 2 foot square bed at 200 ton.I have managed to make some really large parts in the one I have.The main frames I can do but will have to go to a much larger press when I get them heat treated.My press is great for prototyping and when its right I go down to the big bress and knock out 5 or 6 at a go.I have managed to do all my P-40 parts with the exception of 1st stage for the upper longerons.If you find a press that has a 4X4 bed or larger be prepared to pay some serious money.Oh and then there is the weight.

[A2C]

Making the molds is very easy. It's just getting your rig set up right.

[Broken-Wrench]

[quote="hang the expense"]My press has a 2 foot square bed at 200 ton.I have managed to make some really large parts in the one I have.The main frames I can do but will have to go to a much larger press when I get them heat treated.My press is great for prototyping and when its right I go down to the big bress and knock out 5 or 6 at a go.I have managed to do all my P-40 parts with the exception of 1st stage for the upper longerons.If you find a press that has a 4X4 bed or larger be prepared to pay some serious money.Oh and then there is the weight.[/quote]

Do you do contract work? I used to use High density plastic for dies at the Lazy U but it was only for one or to parts.. never production. I saw the press at american champion and they said they had to rework their metal dies after about 200 stampings. Do you have Photos of your press?

[A2C]

I like everything you said but.

american champion

Do you know why?

[Broken-Wrench]

The dies get distorted after all that stamping.

[Rossco]

Having a lot of old stock in the racks is there an easy way to remove the 40 year old wax paper from alclad?

[ZRX61]

Having a lot of old stock in the racks is there an easy way to remove the 40 year old wax paper from alclad?

If there is stil some wax in the paper just put it out in the sun...


For potential metal bashing wallahs:
A crash course to get up to speed on tin knocking...
http://www.lazzemetalshaping.com/index. ... &Itemid=18