Formed cab roof angle 16 ga. steel

This forum is dedicated to the Live Steam Hobbyist Community.

Moderators: Harold_V, WJH, cbrew

DaveD
Posts: 136
Joined: Mon Aug 25, 2008 6:54 pm
Location: Central Virginia

Formed cab roof angle 16 ga. steel

Post by DaveD » Fri Jun 08, 2018 7:38 am

I am starting construction of my P7 cab roof and I have been trying to make some formed cab roof angles, so far without much success. The cab roof and the angle irons supporting it will be fabricated with 16 ga. steel sheet. The attached CAD screen capture describes the general dimensions. The roof will be about 16" wide across the top of the cab. I fabricated two 3/8 thick steel plate templates of this form and in my first attempt sandwiched a piece of 16 ga. cut to the correct inside radii between them and commenced heating and beating the edge over. It resulted in a piece of angle very close to the form I need, but so ugly that I will not put it on my cab.

The angles must be 16 ga. mild steel. The horizontal portion of the angles will vary from about 1/4 to 3/8 and the vertical portion around 1/4. Making straight angles with my 36 inch 450 pound Chinese brake doesn't do them justice, as I cannot get it to bend a sharp corner on metal that thick. And, of course, it would be difficult to then bend this straight angle into something resembling the correct form without notching the piece, which would result in an aesthetically unpleasing result.

Finally, I could make these angles by cutting two pieces for each, the vertical part properly formed and a horizontal piece which I would then silver-solder together. That would look presentable but the cost in silver solder might be prohibitive as I would need to place a continuous bead of 1/32 silver solder along the entire length.

Suggestions?
Attachments
roof angle.JPG
Dave Dalton

User avatar
Fender
Posts: 2524
Joined: Wed May 02, 2007 8:33 pm
Location: Chattanooga TN

Re: Formed cab roof angle 16 ga. steel

Post by Fender » Fri Jun 08, 2018 8:33 am

Dave, suggest getting a length of 1/2" or 3/4" square tubing with 0.063 wall thickness, bend it to match the roof radius, and then cut away everything but the angle shape you want.
Dan Watson

User avatar
JohnHudak
Posts: 1013
Joined: Sat Jan 04, 2003 2:18 pm
Location: Ohio

Re: Formed cab roof angle 16 ga. steel

Post by JohnHudak » Fri Jun 08, 2018 8:38 am

Dave, I don't know what kind of machinery you have, but I milled my angle for a water hatch from a solid piece of CRS..
hatch.JPG

User avatar
Fred_V
Posts: 4202
Joined: Sun Jan 12, 2003 3:26 pm

Re: Formed cab roof angle 16 ga. steel

Post by Fred_V » Fri Jun 08, 2018 8:43 am

Not an easy task the first time but try your method again. That is the way to do it but it takes some skill to do it well. Try cold forming it. You need to get the metal to shrink when bending it to the horizontal and heating it will make it expand.

You might try some 14ga. sheet. It is almost as thick but would be easier to form. You could also braze the two strips together rather than silver solder them or weld them with a MIG. the body shop guys weld sheet metal panels that way by doing spot welds back and for the all over the seam to keep from heating it up. Eventually the seam is all filled with spot welds and filed smooth.
Good luck.
Fred V
Pensacola, Fl.

User avatar
Greg_Lewis
Posts: 1560
Joined: Wed Jan 15, 2003 2:44 pm
Location: Fresno, CA

Re: Formed cab roof angle 16 ga. steel

Post by Greg_Lewis » Fri Jun 08, 2018 9:54 am

I vote for Dan's idea — cutting apart square tube. I've done something similar and it's rather painless.

I also made some sharp bends by putting an angle block in the hydraulic press and forcing the metal into that with a wedge-shaped die. But if the square tube thing will give you what you want, that's easier.
Greg Lewis, Prop.
Eyeball Engineering — Home of non-interchangeable parts.
Our motto: "That looks about right."
Celebrating 30 years of turning perfectly good metal into bits of useless scrap.

rkcarguy
Posts: 875
Joined: Tue Aug 22, 2017 10:33 am

Re: Formed cab roof angle 16 ga. steel

Post by rkcarguy » Fri Jun 08, 2018 10:53 am

There is always spring back, so it's difficult to form anything to a die unless the die is undersized to allow for spring back. Then, the next metal you buy may be different and spring back differently. :shock:
Heat will always shrink the side of the part you heated further past it's original size. So if you were to put a piece of metal flat on a table and heat up one side, that side will grow and the metal will warp upward in the center. When it cools however, that side will shrink more and the part will be warped upwards at the ends. If you are trying to form metal over a die and are heating it on the top, you are fighting yourself.
I think cutting apart the tube will yield the best results at this point as well.
As far as the radius of the cab roof, I made mine from 1/8" aluminum and used the roll at work, then riveted it to the cab working from the center out as the roll wasn't a perfect fit to the profile I needed. The rivets sucked the roof down onto the cab forcing it into the correct profile.
16ga is fairly light, so you may be able to rivet, tack weld, or plug weld the roof to the frame once it's done.
They also make smaller angles in aluminum, I've used 3/8 and 1/2 aluminum angle on my locomotive in many places.

Andy R
Posts: 170
Joined: Wed Sep 26, 2007 2:18 pm
Location: So. Calif.

Re: Formed cab roof angle 16 ga. steel

Post by Andy R » Fri Jun 08, 2018 10:54 am

Dave,
I would try make these angles by cutting two pieces for each, as you wrote, the vertical part and a horizontal piece, but I'd try joining by brazing. That way you could get closer to a continuous 1/32 bead which would be difficult to do with silver solder. Try a short piece first.
Andy

RET
Posts: 752
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Formed cab roof angle 16 ga. steel

Post by RET » Fri Jun 08, 2018 11:32 am

Hi Dave,

The method you use is going to depend entirely on how sharp you want the outside corner of the angle to be. If a 1/16" radius is acceptable, then cutting the angle from square tube will work, if you want to wind up with a sharp corner like real angle, then you will have to mill the angle from solid.

If the radius is acceptable, then you may still have to use the hydraulic press and die combination to sharpen up the corner. Its quite doable, just finiky and may take a few tries to get the finished shape. Forming the curve with the angle shouldn't be too hard, just remember that things will only do what you want when they are constrained so it is impossible for them to do anything else (one of Murphy's corollaries).

Have fun and I'm sure you will get it sorted out.

Richard Trounce.

daves1459
Posts: 97
Joined: Mon Jun 07, 2010 7:58 pm

Re: Formed cab roof angle 16 ga. steel

Post by daves1459 » Fri Jun 08, 2018 9:26 pm

I've run into this problem. There are several ways to skin the cat. Consider this one:
1. Cut a strip of metal 1/4" wider than both legs of your angle added together.
2. Anneal the strip to a dull red. A propane torch will do this size metal. Start on one end and move the "red" annealed area the full length of the strip. Don't worry about distortion or ripples in the metal.
3. Put the strip in your brake and bend it as close to 90 degrees as you can.
4. Securely clamp one leg of the angle on a sturdy work bench or machine table with a piece of rectangular bar stock located in the corner of the brake form. With another piece of bar stock several inches long and a hammer drive the loose leg up against the clamping bar. You won't have to hit the piece of bar stack very hard. Work your way along bending a little at a time until on the last pass when the metal is flush with the clamping bar. Flip the part around and clamp on the leg you just formed and repeat the process. This is the first area where the annealing comes into play as the metal is "dead" and will easily bend plus will stay where you form it with out spring back.
4. Shear or mill off the excess metal to your desired leg length.
5. Lastly roll form the angle to the desired shape. This is the second area where the annealing comes into play. I can see your eyes rolling from here. But, look at the attached pictures for a simple lathe and mill job roll former I made. If you want more pictures and part sketches PM me. The rolls are actually sleeves on the spindles that I lathe cut contours for the shape of the material I'm forming. The pictures show a brass "T" section I rolled for loco driver fender trim. I'm also rolled angles, channels, tubes, squares, and leaf spring leaves. One nice feature of the roller is compound radii can be made as the part is rolled in increments so that the material section does not excessively thin or buckle thus allowing different radii along a single piece if desired.

All this sounds like a lot of work. But, once the roll former is made a piece like your describing and be made in an evening.

Dave
Attachments
DSC00601.JPG
DSC00602.JPG
DSC00604.JPG

DaveD
Posts: 136
Joined: Mon Aug 25, 2008 6:54 pm
Location: Central Virginia

Re: Formed cab roof angle 16 ga. steel

Post by DaveD » Sat Jun 09, 2018 4:29 pm

Thank you all for the many helpful suggestions. There areso many I won't quote each directly, but do it as follows.

Dan, I once had thought about using square tubing (perhaps you had originally suggested that to me, but my memory being what it ain't...). So square tubing is at the top of the list. Also Greg_Lewis, but I believe I have to go to another method to get the proper bends and I will address that below. And Richard, yes, I believe the square tubing radius will be acceptable. It's just the bend radii that concern me.

Then, JohnHudak (that's a gorgeous tank cover!), it looks like CNC would be in order to properly cut the angle from a solid piece of steel and I don't have that capability, so no cigar.

Fred_V, I will try this again as a last resort, perhaps by putting a thick piece of metal strap between the hammer and the angle, which would keep the angle from looking too beat up.

Andy R, as far as silver solder is concerned, I can make a beautiful continuous bead along the inside of the angle, much better than brazing. It's the cost.

Finally, daves1459. I could use square tubing and go directly to step 5, but use my home-made slip roll that has served me faithfully now for about 15 years (Dan even has had some good bends made in this thing). Photos attached. What I would do is slot the rolls about 1/4 inch deep and ~.070 wide right at the end where the tubing grooves are cut. Putting the slots near the end in that fashion will not significantly weaken the rolls overall for my heavy jobs (I've done 3/16 x 2" flat steel in them with no damage). And yes, I have many times successfully bent a single sheet at multiple radii. So maybe that's the best answer, and it might not be too much work.

Thanks again!
Attachments
Slip roll 1.jpg
Slip roll detail.jpg
Dave Dalton

User avatar
JBodenmann
Posts: 2690
Joined: Sun Oct 26, 2003 1:37 pm
Location: Grover Beach, California

Re: Formed cab roof angle 16 ga. steel

Post by JBodenmann » Mon Jun 11, 2018 10:07 am

Hello My Friends
Here are a few photos of one way to make curved angle. I have found it to be easier to just make curved angle that to make straight angle and then curve it. In these photos the angle is copper but this is the only time I have ever made it out of anything but steel. In the top photo we have the work piece cut to fit the steel former. The amount projecting beyond the former should be the width of the angle. As you can see there is plenty of material to clamp. This is important, as if you try to form a long skinny piece it will squirm and shift when you start forming. The second photo down shows the work piece clamped up and ready to form. In photo three the material is being formed with the rawhide Mallet. Don't use a steel hammer, use rawhide or wood for the initial forming. Only use a steel Hammer to sharpen the bend as a final forming operation. Bottom photo, the angle has been cut from the sheet. Now the angle can be finessed with a drum sander in the drill press and disc sander. This is just how I do it, there are others as previous posts show.
Happy Model Building
Jack
Attachments
Angle1.jpg
Angle2.jpg
Angle3.jpg
Angle4.jpg

daves1459
Posts: 97
Joined: Mon Jun 07, 2010 7:58 pm

Re: Formed cab roof angle 16 ga. steel

Post by daves1459 » Mon Jun 11, 2018 2:22 pm

DaveD wrote:
Sat Jun 09, 2018 4:29 pm
Thank you all for the many helpful suggestions. There areso many I won't quote each directly, but do it as follows.

Dan, I once had thought about using square tubing (perhaps you had originally suggested that to me, but my memory being what it ain't...). So square tubing is at the top of the list. Also Greg_Lewis, but I believe I have to go to another method to get the proper bends and I will address that below. And Richard, yes, I believe the square tubing radius will be acceptable. It's just the bend radii that concern me.

Then, JohnHudak (that's a gorgeous tank cover!), it looks like CNC would be in order to properly cut the angle from a solid piece of steel and I don't have that capability, so no cigar.

Fred_V, I will try this again as a last resort, perhaps by putting a thick piece of metal strap between the hammer and the angle, which would keep the angle from looking too beat up.

Andy R, as far as silver solder is concerned, I can make a beautiful continuous bead along the inside of the angle, much better than brazing. It's the cost.

Finally, daves1459. I could use square tubing and go directly to step 5, but use my home-made slip roll that has served me faithfully now for about 15 years (Dan even has had some good bends made in this thing). Photos attached. What I would do is slot the rolls about 1/4 inch deep and ~.070 wide right at the end where the tubing grooves are cut. Putting the slots near the end in that fashion will not significantly weaken the rolls overall for my heavy jobs (I've done 3/16 x 2" flat steel in them with no damage). And yes, I have many times successfully bent a single sheet at multiple radii. So maybe that's the best answer, and it might not be too much work.

Thanks again!
If you deicde to do any forming, regardless of method, don't loose sight of the benefits of annealing the metal. At 16 ga., .060" thick, the stiffness and spring of cold rolled SAE 1018 is pretty high. The yield, I.E. stiffness, can just about be cut in half with annealing plus no spring back. As an alternate material consider extruded brass angle. I would also anneal the brass angle. In the annealed state the brass angle will form well and will be plenty stong enough for your cab roof rib. Also the brass will not oxidize and much as steel during annealing. 1/2" x 1/2" x .062" thick extruded brass angle can be obtained from Online Metals for about $10 per 4 foot length, plus post. One nice feature of the extruded angle is the inside and outside corners are nice and sharp thus eliminating all the forming operations except to fit the cab roof contour.

Dave

Post Reply