The following hood is for a 1949 packard. I have modified the hood by cutting it into three pieces. The front/center piece will be fixed mounted to the car, and is cut with the back edges on a radius up to a point. This point matches where the hood ornament base peaks at the back. I used a shrinking disk from sun chaser tools in sothern california www.sunchasertools.com The disk is a 9" diameter steel disk that has ridges pressed into the edge. The disk, driven bya 9" grinder, is applied to the sheet metal in a sweeping pattern. You want to apply the disk flat so the whole ridge rubs against the metal. The disk being rigid will find the high spots in the metal. Through friction it heats the the high spots up. The hghest spots will turn blue (1200 degrees). I have found working an area of about 8-10" square works best when you have a panel this damaged. As you begin to straighten the metal you can work on larger areas at a time and work out the shallower dents. Once the metal is up to temperature you quench it with water. I do most of my shrinking outside so I use a garden hose with a spray nozzle. You can also use a bucket of water and a rag if it is easier. When you quench the heated metal it shrinks rapidly and brings the metal back to its previous thickness. Once I have gotten the majority of the high spots out I find it best to try heating the whole 8-10" square area up by using a criss-cross pattern. Once the metal is warm(you will be able to see the metal expanding and creating a bulge) go over it in one direction to hit the high spots only. What this accomplishes is when the metal expands it pulls the low spots up to where they are supposed to be and heats the high spots up hotter so when you quench the metal it shrinks the high spots and pulls the low spots to where they are supposed to be. After going over the whole panel until you cant feel any high or low spots with your hand( I find using a layer of cloth or a glove between your hand and the metal helps you feel the surface more accurately) sand it with your block to check the surface again. Repeat the previous steps as neccessary until the panel is straight. Remember just because you are shrinking dosent mean you cant go back and use the hammer and dolly to move things around. Once you have all the dents and waves out you switch the grinder over to an 80 grit disk. You sweep the disk accross the metal in the same fashion as the shrinking disk. You must keep the disk flat; keeping he disk flat will prevent it from removing metal. The sanding disk will heat the metal up in much the same fashion as the shrinking disk. It will also remove the dark surface finish left by the shrinker. By removing the dark finish it will reveal any remaining low spots. Once the metal is warm again you quence it with water the same way. You do not want the metal to reach a blue color when using the sanding disk, that means you are removing metal. This step fine tunes the metal and removes the very shallow waves left. By clearing off the dark finish it brings to your attention the areas that are still low. Many times the disk will leave a spot that appears low but you cannot feel a low spot. What this is is the low spot id exactly the thickness of the discoloration and does not require more grinding. Now I stated before the sanding disk doesn't remove metal which is in a way false, it only removes very very small amounts of material when used properly. Once the whole panel is repaired you are ready for primer and block sanding. There may be a couple small areas where a skim of spot putty is required but most repaired ares will be perfectly flat after some prmer surfacer and block sanding. The tools I use are a milwaukee 6096 sander/grinder with soft start control. I also use a Makita 5" grinder with a strip-it disk to remove any paint or contaminants. The panel must be completely clean of primer, paint, dirt, grease, rust or contaminants of any kind when performing the shrinking. If paint or coating of any kind gets on the shrinking disk when in use it will act as a insulating layer and may prevent the disk from working properly. This hood has been sand blasted so striping was not neccessary. I do not pretend to know it all when it comes to this system and I dont want anyone to take what I have written here for 100% of the information you need to know to use the system. The manufacturer of the shrinking system has a great 3.5 hour instructional video that I would reccomend anyone that wants to use this system purchase. He also covers some hammer an dolly technique that is useful. In picture This is the shrinking disk mounted on the Milwaukee grinder. There are two backing pads used with this system that can be purchased from various suppliers.
Here is one side of the hood before any metal shrinking has been performed. The hood has dings, dents, creases, warps and every other thing imaginable. In this picture I have ompleted most of the hammer and dolly work. I sanded it with a block to reveal the high spots.
This is what the high spots look like after the shrinking disk has been applied. The dark areas are the high spots, and a blue spot is also visible near the center of the picture.
Part of the reason this hood was so damaged was the manufacturers poor attempts at support. I welded a 1/4" steel rod around the edges to give the hood more support. Also since I modified the hood by cutting into 3 pieces additional support was required. Also you will see steam come from the metal when you quench it, you will know it it shrinking when this happens.
This shows the hood with most of the initial shrinking done. Once I removed the largest dings and dents I go back over the panel a second time concentrating on the shallower waves left in the panel.
This picture shows a section of the metal that has been sanded and shrunk using the sanding disk. The discolored sections are evident and show the shallow low spots remaining. By continuing heating the metal with the sanding disk and shrinking most of these shallow low spots will be removed. The straightness of the panel is also evident.
This picture shows the hood in its present form. I dont have a picture of the hood before I cut it but the front center section will be fix mounted to the car. The other two sections will be removable. The hood emblem base matches the point on the front piece.
I read an "advertorial" in Hemmings about this thing a year or two ago. Really amazing. I just wish someone would make something that works as well for filling big rust holes
Since I removed the one support brace that connected the edges of the hood when I modified it I needed to add some support. Using 1/4" cold rolled steel rod I formed a support system that looks like a spider web. I am nt very artistic but I think it came out nicely. The hood is now stronger than it ever was and ready for primer.
I have this article available in PDF if anyone is interested. email or PM me [email protected] if there are any questions I will do my best to anwser them
This is a very very impressive post but I'm wondering how long this whole process took. I checked out the prices and all this stuff and it adds up quick. If I were to use body filler and high build primer, so I could pocket the $500 difference in price... would that make me less of a man or something?
[ QUOTE ] would that make less of a man or something? [/ QUOTE ] yes. I dig the hidden web! Nice touch.
The kit with the shrinking disk, 5 80 grit disks, 3 strip-it pads, mandrel, instructional video, backing pads, spray dykem was like $250.00 and I got the Milwaukee for $125.00 it is a factory reman. unit but looks and works new. for some things you may prefer to use bondo but for the hood and other panels that will be seen regularly on both sides this is awesome. I wanted the hood striht because it would be seen on both sides. It did take a long time to do the hood. I probly have 45 hours in the hood including cutting, straightening, shrinking, support rods, support system, blasting, welding. basically I just though everyone else might benifit from this info. Not saying it is the way you have to do it. But I am a perfectionist when it comes to working with my hands on a project. Shawn
Sorry to be so tuff on you. I really liked what you did. It just seemed like a lot of expense and 45 hours seems like a lot of time, but you do have a work of art there. Really that is phenomenal work. Someday, I hope to have the time to be a perfectionist. Hell, I have a hard time just trying to be adequate at the moment.
Interesting read... sure beats trying to tap out every little dip, and getting metal as brittle as a potatochip... One question, is that as loud to use as it looks like it would be? Ridged disk on sheet metal...
Its not to bad. I wear ear plugs all the time when I am in the show anyway. The manufacturer has a booth at Hot August Nights in Reno and he does demonstrations all day and people are always crowded around him while he is doing it. I would say it is no louder than grinding metal. Shawn
there also is a hamber, john kelly, that makes a similar disc, much cheaper, and it helps a hamber. 50 for his disc, and 40 for a harbor freight grinder. you'll find that the time is probably the same as sanding bondo smooth.
Well done Shawn, thanks for sharing! I have commented on other posts about the motivation that we who share this obsession with cars have...we take pride in the fruits of our labor; the more we strive for perfection, the more pride we take in the final product. You get back what you put in... When this hood finally becomes a part of Shawn's finished car many will see that it is straight and fits the body well; most won't care how it got that way, but for the rest of us that really appreciate the time and love of the art of hot rods and customs, we'll know! Once again, well done!
[ QUOTE ] How do we contact John Kelly? At that price I could afford one. [/ QUOTE ] I bought one of John Kelly's disks and it works great. John is a very talented guy and is eager to help anyone interested in metal shaping. Here is his website URL: http://www.ghiaspecialties.com/ We don't hear too much from John on the HAMB because I think that he is a little self-conscious about his main area of interest which is outside the "traditional" hot rod area...however IMHO, John has made some very valuable contributions to the HAMB through his tech posts...
[ QUOTE ] [ QUOTE ] How do we contact John Kelly? At that price I could afford one. [/ QUOTE ] I bought one of John Kelly's disks and it works great. John is a very talented guy and is eager to help anyone interested in metal shaping. Here is his website URL: http://www.ghiaspecialties.com/ We don't hear too much from John on the HAMB because I think that he is a little self-conscious about his main area of interest which is outside the "traditional" hot rod area...however IMHO, John has made some very valuable contributions to the HAMB through his tech posts... [/ QUOTE ] Thanks for the kind words CharlieLed. I'm not self conscious...I just try to be restrained...don't want to be pushy. Very nice job on the shrinking tech...and a cool web. Here is a similar article (newly updated): http://metalshapers.org/101/jkelly/index.html has some welding information as well. I'm making a new shrinking disc with a shallow domed surface for easier use on flat panels or mild reverses. Almost ready for production. By the way, does anyone have a May issue of Classic Trucks that they would sell? Ron Covell mentions the sunchaser disc, and my shrinking disc in it and I would like to buy a copy. Havn't found one locally. John www.ghiaspecialties.com [email protected]
Nice job Fastcat! Great tech, and a very cool hood. I've also been using Johns disc. (I made mine, as per John's instructions)It's changed how I do metal work. John seems like a really nice guy, and openly shares his knowlege, It's just too bad about the VW thing
i gotta add some props to john kelly, cause this guy rules. he wants the knowledge spread, not to get rich off of us! if you are so bucks down that you don't want to BUY his disc, he'll just give you instructions to MAKE one! i bought one from him, probably a year ago, and got an email last week, offering a possible improvement to the disc, how's that for customer service?
Dont let em fool you. These things ARE LOUD!!!!!!!! I always keep a set of shooting ear muffs for this type of work. We use them on a daily basis at the shop. Very good tech, most people dont believe how well they work.
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