Author Topic: Any metalworkers out there ? making new seatpan etc.  (Read 2414 times)

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Offline greenjeans

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Any metalworkers out there ? making new seatpan etc.
« on: May 29, 2007, 01:16:06 PM »
Ok.... I've drawn out and measured existing bolts etc. till I finished all the beer I had in the fridge.  Basically, I'm going to make a couple new seat pans that will utilize the existing hinge and locking mechanism as well as the rubber bumpers that rest on the frame  on my projects - 76 CB550 & a 72 CB500.  Both are going to be cafe styled rides.  I've made a pattern for the base using measurements from the original pan. I transfered this to my computer so that I could make tiny changes where necessary and have it on file.  When I'm done, I'll post a link so others can download a vector file that they could take to their local sign shop and have them cut a template out of vinyl that they could apply to a piece of metal to have an accurate template to work from.   Basically I was thinking that I'd use either aluminum or steel (I have access to both) to make the pan from.  I have made a "practice" one that is pretty close using sone 3/4" angle iron that I notched over and over to get the radius at the back that I was after & some cardboard for the base.   I was originally thinking that I'd just use that expanding foam to shape the hump I wanted and then cover it with fiberglass etc.  (I still will probably do that method)  But.....I have discovered in my dad's shop a plethora of metal working hammers, sand bad and a stump for working with metal.  I haven't worked with metal & I don't really have my own welder - I might be able to borrow a mig.     Now, down to the questions -  Would it be better to use aluminum vs steel ?   I don't have a sheet metal brake, so my practice pan was made with a vice, some angle iron & a hammer.   Should  metal (aluminum or steel)  be heated before bending ? To reinforce the pan, I was planning on using angle iron (notched on one side so I can bend it)  Does heating strengthen / weaken the metal ?  Advantages, suggestions any info or links to pertinent info is greatly appreciated.   I posted a pic of the cardboard pattern to give a better idea of what I was planning.   Thanks in advance.
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Offline babyfood1217

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #1 on: May 29, 2007, 02:03:51 PM »
Cardboard...sweet.  Well, I'll start the replies with my thoughts and opinions.  I would use steel.  Why?  For me, it's more readily available and cheaper, I've been getting the hang of forming it (I go to school for metalsmithing and metalworking, so I get graded on this) with hammer and stakes (hand dollies), and I just like it.  Both steel and aluminum can be strong and durable, but aluminum, you hanve to have thicker gauge material.  Heat affects steel and aluminum in different ways.  It can harden or soften steel, depending on how you treat it after the heating.  I have taken a piece of 16ga mild steel from the shelf at a metal supplier, and gone from a flat 9" diameter disc to a goblet shape that was 5" tall with a mouth 4" across.  I wailed on this thing, never normalized it (aka annealing or softening) it, and never had a crack or overlap happen.  I worked both in a stump and over stakes (metal forming tools), but man if you could get some thicker gauge Aluminum to do this with, you might be better off.  Softer, more ductile, and you'll probably just thank yourself later.  Weld it or rivet it.  Sheet metal screws would even do the trick.  A really easy thing to do is find yourself an extra seat pan for your bike, and use that as a base.  All you would have to do then as shape the rear hump and you'd be set.  None of that fussing with locating/drilling holes for hinge plates, rubber bumbers etc...  As for the foam, try to find the "sandable" product.  I don't think "great stuff" sands well (full of large bubbles IIRC)  Blue or pink insulation foam works really well.  Just spray adhesive or rubber cement it together and it is rock solid to work with.  Goog luck and keep us posted.

-Chris
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Offline greenjeans

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #2 on: May 29, 2007, 02:18:54 PM »
Thanks.... I have access to both aluminum & steel.  ALuminum up to 1/8"  I had planned on using the original seat pan and just putting a "hump" on it, but it was in really rough shape....rust, holes etc. - It's a bit long for what I had in mind as well.  Also, this bike is on a very tight budget & luckily I have some steel & aluminum at hand.  Plus, I'll have the satisfaction of building my own.   I have a piece of .125" aluminum staring at me as we speak.....think that would work ?  should it be heated before I start bending on it ?  Or should I dig into my pile of steel...  Found some good sandable foam at my local electrical supply house that hopefully will work.
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Offline 736cc

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #3 on: May 29, 2007, 02:46:24 PM »
Go aluminum, steel very heavyweight in comparison

Offline snyquist53

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #4 on: May 29, 2007, 03:13:11 PM »
i would use alum as well you can rivet supports where necessary if you don't have the ability to weld it.  1/8 th inch alum should be fine if you brace it accordingly.  as for foam,  i use a high density foam.  it is water resistant, shapes very easily and holds it's shape very well.  i have found a good source for it in small amounts but there has to be some at your local upholstery shop.  steel is really heavier and can stress itself and the hinges over time
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Offline greenjeans

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #5 on: May 30, 2007, 06:08:07 AM »
Got my pattern wher I want it....I think.  Gonna do one last test this evening and proceed with 1/8" aluminum....

Anybody know if I should heat it before bending ?  It's pretty beefy.  Ideas, suggestions ?
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Offline rhinoracer

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #6 on: May 30, 2007, 06:35:00 AM »
Tempered aluminum is hard to bend without cracking. Soft aluminum is ...well, soft and easy to bend and form. But again, it's soft and easy to bend and deform with use. Plus aluminum doesn't spring back to shape when slightly bent, so you can end up with a distorted seat pretty soon if not braced properly.

In actual use, aluminum weights 1/3 of steel at 1/2 it's strength so to get the same strength you'll use double the thickness, which means only 1/3 of weight savings.

The seat pan is a stressed part which means you'll have to add a lot of bracing or bends in the appropriate places and directions to get the rigidity you need, making the weight savings minimal.

I'd go with steel, which is fairly easy to cut and form and weld. Use #16 gage and you'll hardly need any additional bracing.
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Offline greenjeans

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #7 on: May 30, 2007, 08:34:21 AM »
Hey Rhino, now you got me thinking again....(usually get's me into trouble)  I was planning on using 1/8" aluminum for the pan - similar to the patternn in the photo and then using 1/8" x 1" flat bar or 1" angle (aluminum)  going around the perimeter for added strength.  I'm not against doing it in steel (the piece of aluminum I have is really nice compared to the steel I have on hand) - just being a bit lazy....  You think with the additional flat bar around the perimeter it ld strengthen it enough ?   Still haven't been able to find out if I should heat the aluminum before bending (my practice piece was thinner .063") and I was able to get good square bends in it without heating it...  the 1/8" is significantly more rigid than that .063 - half the thickness so before I ruin that beautiful chuck of metal, I just wanted some more info....Maybe I should just try one out of steel & see how it works...

An additional note...  I am using the stock rubber bumpers (5 pc total) so hopefully that will relieve some of the stress on the pan.

Keep the opinions coming.... I'm open to suggestions.    Thanks
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Offline dusterdude

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #8 on: May 30, 2007, 09:19:55 AM »
jesse james heats aluminum and makes seat pans from it quite a bit.
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Offline Short Round

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #9 on: May 30, 2007, 09:55:05 AM »
Now I am going to have to make a template and take a photo of it to let you guys see what I am thinking of while we are on the subject....................Chris
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Offline greenjeans

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #10 on: May 30, 2007, 10:54:12 AM »
Chris, post some pics.....
that's where I get all these crazy ideas I have.  When I get mine done I'll post pics and a file that has all the dimensions/holes/ bends etc that I used.
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Offline rhinoracer

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #11 on: May 30, 2007, 12:19:31 PM »
Still haven't been able to find out if I should heat the aluminum before bending (my practice piece was thinner .063") and I was able to get good square bends in it without heating it...  the 1/8" is significantly more rigid than that .063 - half the thickness so before I ruin that beautiful chuck of metal, I just wanted some more info....

It depends on the hardness of the aluminum, if it's soft aluminum you can bend it easily w/o heat treating. If you're using a hardened alloy you'll have trouble doing sharp bends without cracking it. You can heat it, just do some practice runs cause it's tricky, aluminum dissipates heat real fast, it also melts at a very low temp.

Try and bend one corner of your aluminum stock with a pair of pliers, if it gives easily you won't have any problems doing the bends you need.

Good luck
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Offline snyquist53

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #12 on: June 03, 2007, 10:07:00 PM »


this my seat i just finished.  i used an old street sign for the alum and holds fine and it's  1/2 the weight of some smaller steel seats i have made.

i would use as many rubber bumpers as possible, or brace those places with the angle iron.  if you don't it will probably deform over time.  steel is easier, but where's the challenge in that.

i used a hammer to shape mine.  you should need to heat it to bend it.  use the end of a work bench and some clamps (poor man's break)


good luck.......post some picts of the process
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Offline snyquist53

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Re: Any metalworkers out there ? making new seatpan etc.
« Reply #13 on: June 03, 2007, 10:11:26 PM »
i used a hammer to shape mine.  you should need to heat it to bend it.  use the end of a work bench and some clamps (poor man's break)

sorry i meant shouldn't need to heat :P ;)
74 cb750, 71 cb450, 77 cb550, 74 cl350, 74 sl200, 00 vt110, 77 sporty ironhead
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