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Old 02-02-2011, 06:01 PM
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scootermcrad scootermcrad is offline
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Default Need panel advice - no crown to low crown panel

Hey everyone! I have a nice little project coming up that I've started making a really rough form for. Just did it to get a good solid idea what direction I want to go.

The project is an aluminum roof insert for a 1931 Model A Ford. The panel will have virtually NO crown (mostly a constant low curve from left to right) in the front 2/3 of the panel, and then slightly MORE in the rear 1/3.

Now some of you are going to tell me to make this from multiple pieces (for several reasons), but I REALLY want to see if I can make it from one piece, vs. make it in two or three pieces and welding it or creating a lap joint and riveting it each section. If it doesn't go well, I can always come back to that solution without wasting a whole lot of material.

Material is 5052-H34, .063 thickness. It WILL get reinforcing bows riveted to the bottom side for structural integrity as well as mounting, but I would prefer that the structure not be what keeps the panel in-shape, but simply to support the shape of the panel that's created. In other words, the supports will be matched to the shape of the panel, individually.

I have an English Wheel with enough throat, a shrinker and stretcher, as well as standard hand forming tools and shrinking discs.

Here's the roof in it's current form. Please ignore the unfinished, not so great looking, roof panels around it... Still have to finish all that stuff.

Rough bow construction to show the general idea... (I will be using these to make a proper wooden guide buck)









So the panel will look something like this napkin when it's all said and done...








So what can you guys recommend? I have some thoughts on doing some very light initial shrinking and stretching to get the shape going in the right direction before wheeling.

I think my biggest concern about this panel is keeping the curve in control in the front 2/3rds of the panel. I don't want the roof to have a bubble appearance to it from the side view. If I start to get too much crown in the front 2/3rds instead of side to side curvature, can it be controlled with some edge stretching/wheeling?

I'm starting to think about this panel and I really want a plan of attack so when the buck is finished I can get to work. Feel free to draw me sketches, or whatever else it takes, to get your input across.

Again, if this 1-piece panel fails, I will go with a multi-panel construction, but I would rather do it from one piece.

Thanks for any help guys!
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Last edited by scootermcrad; 02-02-2011 at 06:10 PM.
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Old 02-02-2011, 09:29 PM
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Richard K Richard K is offline
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Looks like you have the wooden pattern bows laid out smoothly. Good job.

Step one put your shrinker and stretcher somewhere out of the way. You will have no need for them and if you decide to use them to shortcut getting some shape into the panel it may cause trouble in the end.

You have a very low crown panel. It will be easy to wheel in the shape you need. I would start with a flat or the nearest to flat lower anvil you have. The flat or near flat anvil will avoid tracking marks. A flat or near flat anvil will produce a gentle curve mostly in the direction you are rolling. Very little curve will be generated perpendicular to the tracking direction.

Looking at your buck the side to side curve seems about the same at all points from the front to the rear of the car. So if you first roll across the panel from side to side with the flattest anvil you can try for consistency and a even profile on the entire length. Aim for just a bit less curve than your buck profile shows. The next step will add a bit of shape, so that is what the allowance is for.

Next use a anvil with just a bit of crown (say a 36" radius) and roll the panel in the front to rear direction. After one pass over the entire panel you will have a constant curve front to rear and have added a bit of more curve side to side. The rear section has greater curvature than the front (in the direction front to rear); thus the rear about half will require additional passes to add curvature. Do this by again wheeling front to rear and stopping at about the front of the rear side window. vary the stopping points so as not to produce a "hard edge". the curve needs to flow together.

If you have not produced enough curvature in some direction do some added wheeling in the needed areas. Follow the original tracking pattern if possible; in case there is not symmetrical curvature; you may need a bit of added wheeling to even up the panel.

For success, plan a tracking pattern for wheeling and then follow it carefully. That way you will get equal results on both sides of the centerline and be able to maintain control of the shaping process.

Tracking... I would begin my side to side (crosswise may be clearer) tracking at the front and use a shallow (closely spaced) zigzag pattern to the rear.
Next begin the front to rear tracking at the front center and work to one side then completely back across the panel to the other side, then back to the center. Then check for fit and do the additional wheeling (front to rear) in the rear portion to tighten up the curve.

Because this panel is large you will most likely need a helper to support the panel on the "other" end. Also use a very light pressure as the part is large and low crown. A almost imperceptible curve from each back and forth motion will quickly add up to quite a bit of crown; se be cautious not to overshoot. Much easier to wheel a second light pattern than try to get rid of too much crown.

The 5052 should work ok for this panel. It will be somewhat harder after wheeling it but that should not be a problem.

Do not try to anneal the panel, the H34 temper designation indicates: the material has been strain hardened and stabilized. The 5052 series is alloyed with magnesium and thus is given a stabilizing thermal treatment at a temperature lower than the annealing temp. Without the stabilizing treatment this alloy will age soften at room temperature. If annealed after stabilization and not furnace cooled the grain structure changes and the material becomes very unmanageable in forming. (source:American Society for Metals. Source book on selection and fabrication of aluminum alloys)

Note on shrinker/stretcher: many people have made low crown panels, very nice panels, by shrinking or stretching just the edges. This is still a possibility if a wheel is not available. However, that method puts the panels under a bit of localized stresses warping the metal into shape. As I say it works but leaves a tight panel. Wheeling produces a relaxed panel which is an easier panel to work with in later steps of welding and whatever. That is just my experience. This craft is filled with a variety of techniques; what works for you is best for you.

Good luck, patience will yield good results.
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Last edited by Richard K; 02-02-2011 at 09:44 PM. Reason: spelling, add shrinker note
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Old 02-02-2011, 09:41 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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What Richard said!

There is a lot more crown in that than you think. I did one for a sedan a couple weeks ago from steel.

Go slow. You'll need a helper to handle the large panel. If you try and do it by yourself, you'd likely let one end droop and kink the panel. At least I would not attempt this by myself unless I rigged up some aids to keep the panel from drooping. Life is too short and material is too expensive...get help.
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Old 02-02-2011, 09:47 PM
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Forgot to mention. I like the theme of your car. Bomber seats are cool; Stop lite is fabulous!

Thanks for the good photos
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Old 02-02-2011, 10:39 PM
Dyce Dyce is offline
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Good job Richard!! The only thing I would add is really check your wheel alignment. With wide flats your contacts need to be in perfect alignment at the pressure you are wheeling.
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Old 02-03-2011, 10:26 AM
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WOW! That is EXACTLY the response I was looking for! Thank you Richard, and everyone else! I really appreciate your input! Perfect!

Shrinker stretcher will be put of in the corner where they will mind their own or get a dunce cap! (just always wanted to use that little thing. HA!)

The car started life as a 1931 Slant Windwhield Town Sedan. The car is supposed to appear as if it were built in the late 50's early 60's...

When I bought it...



Now...







Hasn't seen the road yet, but the chassis is complete and painted, and now just getting started on finishing up the body so I can get paint on it, finish up the details, and hit the road!

In all seriousness, I really appreciate the knowledge here on this board. I frequent the HAMB, and some of you here will recognize the build, but I wanted to get a little more focused on metal shaping itself, so I thought this might be a better place.

I actually posted this part of the project on Metal Meet a long time ago, but about a week after their server crashed and the thread was lost, along with all the responses.
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Old 02-03-2011, 11:09 AM
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Okay... Just to make sure I'm on the right track, here. I sketched the two major wheeling process and will assume there will be fine tuning (OF COURSE).

Following what Richard has said, here's step one... Wheeling left to right with a flat wheel or virtually flat wheel, with about 50% overlap.



Then step two would be wheeling front to rear using a large radius wheel, starting at the middle front, working left (shown in red), working across the panel from left to right (shown in orange. Will rotate the panel 180° to fit it in the frame of the E-wheel), then finishing up by wheeling back to the center from that edge (shown in green).

Right?

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Old 02-03-2011, 12:15 PM
Dyce Dyce is offline
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I would wheel around zone 9, 10, 13, and 14. You have it outlined on this picture so you know it needs to be shrunk, or have less stretch to make the panel follow the curve of the top. I would try to use a paper pattern to see just how much shrink or stretch you are dealing with. You could use a table cloth ever the top and make folds in that area to get an idea. I have a feeling over the whole area you could have 1/2 to 5/8 of an inch.
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Last edited by Dyce; 02-03-2011 at 02:15 PM.
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Old 02-03-2011, 12:26 PM
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Quote:
Originally Posted by Dyce View Post
I would wheel around zone 9, 10, 13, and 14. You have it outlined on this picture so you know it needs to be shrunk, or have less stretch to make the panel follow the curve of the top. I would try to use a paper pattern to see just how much shrink or stretch you are dealing with. You could use a table cloth ever the top and make folds in that area to get an idea. I have a feeling over the whole area you could have 1/2 to 5/8 of an inch.
Cool! Good idea!!!

Going to start building the final buck this weekend. Once it's complete I will find something light weight to drop over it and see what I can read.

I did find when making the model out of a paper towel that it would need to be shrunk in those areas, but I wasn't stretching in the middle like I would be in Richard's description.
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Old 02-03-2011, 12:28 PM
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QUESTION! I've never used a shrinking disc on aluminum, only on steel. Can it be used to get me out of a pickle if needed, or will the aluminum cool too fast to get a good shrink?
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