Can you "crown" sheetmetal without an English Wheel?

Some good answers so far.
Drawing the grid pattern on is a good idea to track progress.
It is possible without an E-wheel, and would be a good learning experience (read - you may frustrate the **** outta yourself!)
Achieving it all with compressive stretch (like an e-wheel or power hammer does) will take a lot of consitent hammering. You may consider starting with elastic stretch - large radius hammer/mallet with fairly gentle overlapping blows (grid will help keep track) into a soft backing that allows the metal to "give" - ideally a sand bag, but even a couple of blankets/carpet might work . Hell you could hammer directly onto soft ground if you wanted.
You ideally want to avoid "walnuts" as they make for more planishing work after.
Once you are pretty close you can move on to planishing (hammer & dolly work) to bring about an even surface and final stretch - which will now be compressive ie forcing the metal to "grow" sideways by hammering it thinner.
By defintion crown is curve in 2 directions (so rolling won't be enough)
I'd stay away from any mechanical shrinking, as it is tougher to do/control and may induce unwanted stresses that will likely show up when welding. Nothing wrong with a shrink disc to tighten up loose edges though.

This is one of those things that can be done, but some of the other solutions (donor panel etc) may be simpler. Depends whether you simply want the patch, or want to learn something new - either how to make a low crown panel, or some interesting new phrases!!!

Also best advice is take it slow and creep up on the shape - any panel is tough to "undo" a mistake - low crown is probably worst.

Good luck and keep us updated!!
Barry

 

Correct me if I'm wrong, but that door doesn't really crown. It rolls in at the bottom and the whole side of the truck is pretty flat. If it were crowned it would look wrong with the front fender.

Thinking that that's the case, you need to very carefully weld the top 1st with lots of control and pa***ience. Once tied in at the top you should be able to pull the skin to the shell and create enough surface tension to maintain the look that was designed into the door. The weld at the joint is the key. Win that and you won the repair. I just can't see a 60 Ford PU having a crown vs a roll. I hope this makes sense. If it is a roll only then you could also put a partial roll in the repair panel before welding (yeah the welding bottle is a good tool for that), but leave enough to pull the repair skin tight enough to create tension. Without surface tension the door will be easy to flex won't keep alignment after a few months.

 

Good ****, boy we have talent out there!

 

I'm with you,I've seen this work in person.Its amazingly simple and effective.

 

Place a tiara on it.

 

I have two skins but they're both pretty beat up - I could work the dents out but I want to try something new and hopefully learn something - so far, I have.

I'm guessing the gauge to be about 18-20?

Looking top down at the door there seems to be an ever so slight crown in the center of the door - it absolutely has a roll.

As far as attaching the skin goes, I was thinking about some (gasp!) modern methods of attachement - bonding adhesives - due to the potential to warp the hell out of this ****er. Just a thought. Most likely, I'll end up welding it with my MIG. In any case, I understand the necessity of tacking nice and slow, damming the surrounding areas to eliminate warping and allowing plenty of time for cool-down.

Thanks for your thoughts, guys. This has really been helpful.

 

Use a s**** of heavy cardboard or thin paneling to make a template of the crown you need from the other door. Use both edges of the template to get the shape side to side and up and down (does that make sense?...) Take your template to the wrecking yard and if you can find a door or roof skin with the right crown or slightly more, you're in bizness. If not, make your own using the template. Unkl Ian's 2" grid method works well, I've made a few panels that way. The only thing I would add is go very slowly with a very light hammer, if you find you need more crown after the first p*** hit between the grid second time around. If the metal is shiny you should be able to see the hammer marks easily, little circles 3/16- 1/4 inch in diameter. If you get too much crown, weld it in and go over it with your shrinking disc.

And yeah, hammer welding is another whole topic. Tig is best IMO. Tack it together, keep the hammer and dolly real close by. I like to have a cardboard box near by, weld an inch, toss the torch into the box, hammer the bead. Go easy, it's easy to stretch the metal too far when it's hot.

And Ron Fournier is a master. His Metal Fabricator's Handbook should be required reading for anyone building a car.

 

can someone explain the grid pattern idea ?

I understand making the grid , but unless you are trying to make a bowl do you hammer 4 grids horizontal and only 2 grids vertical to make it curve one direction over the other ?

Beaulieu

 

Bealieu,
It actually doesn't matter, as "shape" and "arrangement" are seperate things. What this means is that the panel does not need to be made (shaped) with the same crown as is required when you come to fit it up.
A panel with the same curvature in both directions (ie it's shape) can be rolled to a tighter curvature in one direction, and in doing so, will open up in the other (perpindicular)direction - this is the principle that a flexible shape pattern (search on one of the metalshaping sites) takes advantage of.

What will be neccesary is a pattern of hits that induces more stretch in the centre, and proportionally less as you move outboard - otherwise the whole sheet will be flat, just bigger and thinner in theory anyway....

Glad to hear you're gonna give it a try Tace!
When it comes to welding, it is as important to be restretching the shrink induced by the heat of the weld, as it is to try to control the amount of heat in the first place. The trick is to do short sections, grind flat and hammer on dolly before progressing. The more it pulls and buckles, the more difficult it becomes to read what is going on, and what action is needed. But that is probably a topic for another thread.....

Barry

Barry

 

try using a rubber mallet and a very low crown die underneath. be very gentle. its how ive done a few low crown panels myself. ex. richards helve hammer dies.


more http://allshops.org/cgi-bin/community/communityalbums.cgi?action=openalbum&albumid=9980291441693

 

With all this time spent talking about it, I could have gone down to the junkyard with my chizel, cut one out and made it back home already....

 

(Snip)

Actually, most vehicles have some small amount of front to back curve on the sides. Looks better, less noisy (I think), and resists dents and olicans.

John www.ghiaspecialties.com