Best way to bend this seat pan

My DOHC 750 has a less than ideal frame shape for a seat pan. I've got the first bend done and happy with it. How do I make the second, without ruining the first in the process?

I'm using 18 gauge steel.

I know I can just use lots of clamps to get it to sit the way I want, but I also know the moment I take those clamps off the pan will spring back.

Ideas?

Below is an example of the shape I want. However the thread where I found that pic is long dead.

I spent some time beating a stock pan to fit and wasnt happy with the results yet.
 

Attachments

I wonder if bending a 1/8" flat bar that is about 10" long and 1/2" wide would be easier, then tack welding the pan to it ... 9r if that would be too weak and straightened out somewhat by the pan as well ‍♂
 

Tim

Administrator
Staff member
I'm no metal shaping genius, but my brain tells me to cut a piece of 3/4" plywood or take a chunk of a 2 x 8 or 2 x 10 on top of the flat section, and clamp that to the frame. This will hold the flat section in place, with an emphasis on getting nice support along the current crease to prevent it from warping there.

Then bend away.

The 2nd pic of the target shape looks like a very thin sheet of what almost appears to be galvanized sheet metal which would have made it easier to shape and retain the shape, but wouldn't be a very solid seat pan.
 

SONICJK

Reminds me of...me No, I'm sure of it. I hate him
Basically you'll need to clamp down the bend you have done, and then overbend the next one so that when it springs back the profile is right.

Find a pvc pipe or similar that's close the the radius that you need and use that as a bending form. You'll never get it to bend correctly on the frame because as you mentioned it's just going to spring back every time and you don't have any way to overbend it while on the frame.

I would clamp what you've got to 4" pvc pipe (or whatever is close the the frame radius) and wrap it around the pipe slowly removing it incrementally to check the bend until you have a good fit.
 
So, for anyone else that comes across this in a search at some point, this is how I'm doing it.

I welded a support through the tube so I can clamp it, then welded a flatbar on top through which to feed the sheet metal.

It's working ok. I bend down and tap tap tap with a rubber mallet.
20200412_102748.jpg
20200412_103738.jpg
 

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I have not seen anyone use aluminum for a seat pan that they plan to bend to shape.

I mean, if you're going aluminum for ease of bending you'll just end up with a flimsy pan. If you go with something that will be sturdy, then it won't be any easier to bend

*shrug*
 

Maritime

Well-Known Member
I think Titan suggested aluminum as it is less springy when bending it vs steel, it's also lighter and easier to cut/shape. when you bend aluminum, it just stays bent and you don't need to over bend past for the spring back. Now if you are welding it etc. then steel is much easier. Either way keep going, it's starting to shape up for you.
 
I think Titan suggested aluminum as it is less springy when bending it vs steel, it's also lighter and easier to cut/shape. when you bend aluminum, it just stays bent and you don't need to over bend past for the spring back. Now if you are welding it etc. then steel is much easier. Either way keep going, it's starting to shape up for you.
Ah, ok. I suppose that would help. I didn't think aluminum wouldn't bounce back.
Probably might just have to tack a couple of machine screws to the pan, and that's it
 

NoRiders

Well-Known Member
I used an alloy seat pan, didn't need the bends you have to make, but to add stiffness, and you may have to anyway even with steel, I ran a few bead patterns.

 

sav0r

Member
Seat pans aren't that heavily stressed. They hold at most 2 peoples weight. So 400 lbs, and they are generally supported by the tubes under neath. The pan really just bridges the gap. IMO, rolled beads are mainly for stopping pans from drumming, though they do increase rigidity.
 
That would certainly be the way to go, but i just don't have the tools to do that and make it look good.
OEM seat pans are a different story. Those are stamped out and yes, have a ton of rigidity to them as a result.
However, unlike the OEM seat pan, this will sit along the frame and have more support all around than the OEM one does. We'll see. Plenty of others have done the same and it worked out fine for them.
 

CarbsAndCylinders

Careful With That Axe Eugene
Seat pans aren't that heavily stressed. They hold at most 2 peoples weight. So 400 lbs, and they are generally supported by the tubes under neath. The pan really just bridges the gap. IMO, rolled beads are mainly for stopping pans from drumming, though they do increase rigidity.
Yes, you could be right but that 400lbs is spread over usually 6 or so rubber mounts not over the entire pan surface. By drumming do you mean to keep it from noisily resonating, if so, That's interesting, I never thought about that before.
 

sav0r

Member
6 or so rubber mounts as opposed to the pan sitting on a significant section of the frame in this scenario. This requires far less rigidity from the pan.

Yes, resonance is a large issue with big panels, so they roll beads to help keep them from generating noise. Sometimes the stiffness is needed for other purposes as well.
 

CarbsAndCylinders

Careful With That Axe Eugene
6 or so rubber mounts as opposed to the pan sitting on a significant section of the frame in this scenario. This requires far less rigidity from the pan.

Yes, resonance is a large issue with big panels, so they roll beads to help keep them from generating noise. Sometimes the stiffness is needed for other purposes as well.
Do they muffle farts?
 

doc_rot

Oh the usual... I bowl, I drive around...
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you need rigity in the pan to prevent the seat cover from turning it into a taco, whatever supports below are probably fine. The first time you park in the sun and the cover shrinks its game over.
 

pidjones

Well-Known Member
Most early GoldWing pans had only the front tongue (with support from a frame-mounted hoop under), two rubber pads in the middle, and the two bolt ears near the back. Ten large holes, I guess to let air in & out. And one X near the front to reinforce. The sides rolled down over the frame significantly which added strength. I have never seen one that was bent in use. Now, those were the early ones - before Honda saw the loads that GoldWing seats would be asked to carry. Also required to be comfortable for older butts on longer rides than most of the seats I see on here. Notice tbe reinforcing buttresses on each side to prevent the tacoing doc_rot mentions.BTW, with the foam glued to tge pan, there should be no resonance problems. Easy to find dense (you need dense to keep butt bones from hitting the pan) foam is carpet padding called "rebond". I have found carpet dealers will either give away left-over scraps, or sell it in small quantities cheap. Glue with 3M 80 spray adhesive, cut with electric carving knife (NOT hers!) Final shape with a course grit grinder.
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ok. does anyone have any pics of the so called "tacoing" phenomenon?

While it makes sense in theory, i've come across MANY builds that use sheetmetal seat pans and i have yet to see a single one complain about this.
Grinding on the seat with your ass seems like it would put more stress on the fabric than just letting it sit out in the sun for a while.

Fiberglass would be more rigid, i agree, but i have zero fiberglass experience and don't really want to invest in all of the materials only to come out with mediocre results from me not knowing what i'm doing

I think i repaired a canoe once like 15 years ago, and it all came out lumpy like a pile of garbage. Just don't really have the desire to learn the process.
 

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