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Old 03-10-2009, 05:38 PM
Scored: 10
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Fender Bender: A Lesson in Metal Shaping.

So now I'm into the thick of shaping. I'm working back and forth between stretching the center of the panel to get the shape and shrinking the sides to gather all the extra material. If you could check the metal thickness, you would be finding the sides to be getting thicker and the middle of the fender to be getting thinner. Metal is definitely moving, like if you were rolling pizza dough with a roller. So while your working with the english wheel and the shrinker, you need to be checking your shape along the way so that it does not get out of control. I keep the radius gauge close by and after a shrink pass and a stretch pass I check the surface with the gauge.

In this picture you can see that I'm close to the #4 radius that I want but not there yet, as light can be seen between the gauge and the fender surface. The gauge will show you where you have not stretched enough, or where you have done too much. In some places it may be good and in others it may need more, to keep the surface even you must constantly check it or it can get ahead of you and cause a mess.

Another concern is the shrinking you do on the sides. You MUST shrink evenly, or the fender will twist, spiral, tweak out of shape, or just generally become deformed. If your shrinks are not evenly dispersed both down each side, and the same on both sides of the fender, you will not get a nice even curve. Pushing harder on the shrinker in one place compared to a place even just an inch away will give you hard peaks instead of a gradual curve as it follows the line of the tire around. Shrinking more material on the left of the fender than the right will pull that side harder, both making one side a different diameter then the other, and giving the fender a twist. Basically it will not fit as a fender should.

At this point it has really come around and is starting to look like a fender. I have got another dolly out which has a really nice smooth shape to use to blend the transition from the shape of the top of the fender into the sides. I used the nylon and rubber hammer to bump it over the dolly, but at this point I'm starting to smooth out the shape of the sides as I'm working them so the body tools come out. Also the shrinker will leave some puckers here and there from pulling the material, so I use a flat faced body hammer and a slapper to even it out. You have to remember that if you strike hard and here the tink of the dolly solid under it, you will be stretching some. The slapper helps to not stretch so much. So basically this is how the shaping goes, stretching, shrinking, checking the surfaces, always trying to stay ahead of the metal. You need to understand what it is doing so that you can properly adjust your actions to how it is acting. I'll fast forward now to a fender that is ready for all the details.

So why would anyone go to the trouble of scratch building a fender anyhow with all the fenders you could buy on the market of just about any size and shape you ask? Well I now do work primarily for one person, Shane Gatto. You may know him on Club Chopper as Rootbeer Float, and if there is one thing I have learned about him, he likes to really challenge people for their best work. We could have just modified an existing fender, but it makes the bike all the more special and interesting when it has a few hand made parts with character. So now that I had a good shaped fender, we worked out the details of the fender that will set it apart from any others. The fender will not only have a rib up the center, but also a bead all the way around it, with strut mounts integrated into the details. So after trimming the edges to the fenders final dimensions using tin snips I start laying out the lines for the rib.

Now the problem with needing to run a rib down the center of the fender is a good one. I only have at this point in my equipment collection a bead roller. The bead roller has a deep throat to it, but no depth at all. Which means that the sides of the fender will prevent the fender from passing through the machine. After a lot of thought, I made the decision to cut the fender in two pieces length wise off center, run the rib down the center, then weld the other half back on. So after I marked the center line of the fender and the off-centered cut line.

I cut the fender in two using a very thin cut off wheel. The thinnest cut off wheel you can get along with light pressure will give you a nice clean cut when it's the only thing that will get the job done. Let the wheel do the cutting at the speed it likes, don't try to force it to cut fast, that's when you end up with a cut edge that looks like a lightening bolt...not good.


Last edited by Ace of Spades; 04-28-2009 at 06:38 PM..

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Old 05-12-2009, 10:01 AM
CC Member/Contributor
Awesome Oilburner! thanks for all the info and pictures too. For me this has always been interesting and your article took alot of the mystery out of it. --Drew
Old 05-12-2009, 12:12 PM
Club Chopper Member
fuckin cool ! bravo !
Old 05-12-2009, 07:43 PM
Club Chopper Member
Glad to see some feed back posted up, thanks guys. I wanted to really explain what was going on so maybe people would get something out of it more than just "he used an english wheel and this shrinker thing". I'll answer any questions anyone has about the process if something isn't clear. Mark.
"I go to bed at 10 now".
Old 10-07-2010, 05:06 AM
Club Chopper Member
OMG This post sucks! now I have to go invest in an english wheel, bead roller, and shrinker!!!! LOL

Just kidding about the suckage... very nicely don sir!
Old 06-06-2012, 11:45 PM
Club Chopper Member
Mark that's a great write up and pictures. I appreciate how long that must have taken besides actually making the fender. Thanks lots. I know a bit about machining and welding after 25yrs in the game but sheet metal work is out there.
I now have more of an appreciation of just how specialised those skills are.

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