Motorcycle seat pan

[Screwdriver]

So I have been tasked with making a seat pan for a chap just up the road from me. It is a paying job and will hopefully restart my failing motivation to do anything.

Here's where it's at:

Incredibly, the mock up jig worked and the cardboard "CNC" version fitted the bike perfectly.

The plan is not to make this in sheet steel in 3 obvious parts then weld/plug weld the sections and any fittings. I am just about to buy some stock from eBay unless anyone has a bettr idea. Thinking of going with 1.5mm with perhaps some reinforcing and or swages.

Something I am not so sure of is how to attach the vinyl. Chap says he's happy for it to be glued but since I probably won't be doing the upholstery, I wonder if there's a better way for a clean finish.

 

[OJCar]

How about wrapping the vinyl under the edge and on the underside glue and clamp it with spreader strips held on by studs and nuts?
Or wrap the vinyl under and use a plastic edging channel to hold it?
Or make a subseat to go under the foam that clamps the vinyl to the seat base?

 

[Mick Annick]

All of my bikes have had the cover glued in place without a problem. One had an Ali pan which had tabs punched to help grip the cover when it’s stretched over.

I’ve had one recovered this week - fibreglass pan with the cover glued on as per the original and all looks good.

 

[Morrisman]

I’ve used contact adhesive before, which sticks like **it to a blanket. You get one chance though, so best to make sure everything in aligned and ready to go before “pressing the dry-to-the-touch faces together”

 

[Screwdriver]

Thanks chaps. I will leave the edge dressed and plain and trust whoever does the upholstery. I could always glue a wooden strip behind the flanges if <whoever does it> need staples. Having the pan made up in sections also allows for design changes if required.

I'm looking at 500x500 mild steel sheets 1.5mm thick delivered for circa £25 (off eBay). I don't know if that's a good price but seems ok unless anyone knows better. I will need 2 maybe 3 sheets.

 

[addjunkie]

Dont make it too tight to the frame tubes if wrapping the upholstery, or itll be too tight once upholstered.

Dont forget what ever keeps in place once upholstered. Quite annoying paying to have a seat done then realising youve forgotten a sticky out bit! Dont as how I know.

 

[Morrisman]

Thanks chaps. I will leave the edge dressed and plain and trust whoever does the upholstery. I could always glue a wooden strip behind the flanges if <whoever does it> need staples. Having the pan made up in sections also allows for design changes if required.

I'm looking at 500x500 mild steel sheets 1.5mm thick delivered for circa £25 (off eBay). I don't know if that's a good price but seems ok unless anyone knows better. I will need 2 maybe 3 sheets.

I’ve had success ordering 2’ x 3’ sheets of steel from motor factors such as Unipart, or whatever they are now called. It’s supplied in various thicknesses. Might be worth checking around your area.

 

[Screwdriver]

It is an unusual seat support. Just two 20x40mm lengths of box section as mocked up in my jig (in MDF). The flat surface of the jig is to ensure the tank line and seat up form a straight line with the seat base. I will probably insist on some additional bracing to support the seat edges.

This is what I am working from though the bike is kept elsewhere hence the need for a jig. Both tank fixing and seat fixing are to be decided so they can be modfied to ensure a good fit to the seat which makes things a lot easier. Looking forwards to designing and fabricating the removable seat fixing. Not rocket science but should be fun to come up with something interesting (that works!).

 

[Screwdriver]

I’ve had success ordering 2’ x 3’ sheets of steel from motor factors such as Unipart, or whatever they are now called. It’s supplied in various thicknesses. Might be worth checking around your area.

I'll have a look thanks. Delivery on such small quantities is the killer. I need to get myself a van!

 

[Morrisman]

I'll have a look thanks. Delivery on such small quantities is the killer. I need to get myself a van!

I order at their shop, then go get it from them in the car when it arrives.

ETA: Euro Car Parts is the motor factor I use, only 3 miles from me.

 

[RichardM]

If you have the facilities to punch some "V"s into the rim they could attach the vinyl to those. Otherwise a good contact adhesive or make a frame to go underneath to sandwich the vinyl and screw / rivet to base.

 

[keithski122]

I do auto upholstery and bike seats, I'd much prefer to have something to staple to than just gluing on. Maybe a 3mm band of plastic around the inner edge. I do quite a few new vespa seats which have plastic pans and I get a really nice finished edge compared to the older stuff thats glued on.

 

[Mick Annick]

I’ve used contact adhesive before, which sticks like **it to a blanket. You get one chance though, so best to make sure everything in aligned and ready to go before “pressing the dry-to-the-touch faces together”

That’s why I took it to an upholstery specialist to be done, I couldn’t forgive myself if I messed up a NOS cover!

 

[Mick Annick]

If you have the facilities to punch some "V"s into the rim they could attach the vinyl to those. Otherwise a good contact adhesive or make a frame to go underneath to sandwich the vinyl and screw / rivet to base.

That’s what my Ossa Ali seat pan has

 

[Screwdriver]

I do auto upholstery and bike seats, I'd much prefer to have something to staple to than just gluing on. Maybe a 3mm band of plastic around the inner edge. I do quite a few new vespa seats which have plastic pans and I get a really nice finished edge compared to the older stuff thats glued on.
View attachment 487312

Well, that’s what I was hoping for, a reply like that.

Brace yourself, I might try to persuade my client to ask you to do it, if you’re amenable. I’ll pm you….

 

[Screwdriver]

...after a slight delay due to plumbing, a quick update.

It's a gradual curve but still needs a slight "tuck" so it's wedged between two forms before hammering.

Turned out better than I had expected for a first attempt.

Next one is a lot more tricky. Needs a tight curve and a 45 degree flange only. 90 degrees much easier (I discover).

Bottom form is done, top is just there to stop the flat section from lifting. Decided to screw the parts together through the metalwork so that I could lay it flat for hammertime. Clamps get in the way and could allow the sheet to slip.

Very happy with the result. You can see where the "tucks" were hammered out but after a while the rebound simply wouldn't allow any further bend. I can adjust later when the flange is trimmed to about 10mm. The weird triangle bits are there to give me some meat where the compound angles meet. I can't tell you how long I spent overthinking this!

Tried (and failed) to get a nice crease with the flypress but everything was fouling. Yes the crease would be "the wrong way" in this image but I can use the flypress to hold it firm while hammering (hat didn't work either!)

Eventually I manhandled the bend using a couple of clamps, bending by hand and tidying up with a cold chisel/bolster.

Pleased with progress. The excess material prevents a more complete assembly but after all that, I'll be nibbling away gradually to get a good fit.

THIS is the problem area.

Looks easy and obvious now but I had to come up with a way to get these awkward planes to intersect and form a usable "bead" for the seat cover to follow. Clearly I need to trim away until I get a good smooth edge and the planes intersect without leaving anything nasty in the seat edging - plus of course it needs to look good!

 

[Beeezer]

I made this arris end a few years back and never finished it…..

 

[Screwdriver]

Bit short...

 

[oldbikedavey]

Had thought about having upholstery elastic strapping supporting memory foam for a really effective long distance saddle....
On either a sheet aluminium or tubular steel framework.
Hmmmmm....

 

[Screwdriver]

Memory foam will simply crush down to nothing. It has no rebound. I have seen people use a thin layer to conform but only when used in conjunction with springy upholstery foam underneath.