Ironhead DIY Custom sprung solo gel seat

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This seat is ust one small part of my project that I started 14 years ago and am now almost finished (its runs at least). The project is here: http://xlforum.net/forums/showthread.php?t=2077210

At some point over 10 year ago I bought a solo seat pan and at some point in the last 2 years I fitted it to my frame using cheap Chinese mountain bike springs. It would have been much easier to use regular solo seat springs under the seat but I was planning to fill the area under my seat with electrics and couldn't spare the room for 2 spring mounts. so I went with these shock type springs outboard of the seat. Apparently I didn't take any photos of the seat pan on its own and all i could find of it mounted on the bike is with rags or tools piled on it. well this has just a small rag but you get the idea of the seat pan.


There it has just a thin 1/8" layer of extra dense rubber on it. I was going to add another maybe 1/2" of medium density foam to it and a skin of some sort and keep it slim. But my old 2 seater was just so comfortable that I decided to mimic that style on to my new solo seat pan. I bought this seat 25 or 30 years ago, don't know what its called but it is a Corbin and at the time it was marketed as "the most comfortable seat in the world". And it is in fact the most comfortable seat I have ridden. what an amazing improvement from the original stock seat:


to make a long story short, here's what I made:




And I do now intend on filling in more details on the long story how I made it, sources of information and materials, etc. This is not a professional job, I've never done this kind of thing before. Many of you would be able to do a better job. And I think it turned out quite well for an amatur first time attempt. Its the kind of thing that should be quite do-able by anyone with limited tools and experience

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I forgot to say above that I fit the hardware so that I can still swap it out for the dual seat in about 5 minutes if I want to take a passenger

I built up the shape of the seat using 1/2" medium density closed cell foam https://www.foambymail.com/product/g...ber-black.html as was recommended for applications of less than 1-1/4" thickness in the comment section of this article: https://www.foambymail.com/blog/diy-...torcycle-seat/

I built it up using waterproof contact cement. Any waterproof contact cement should work, what I used was Barge (the type of glue pretty much all shoemakers use to glue soles on shoes). And I shaped it using a flap disk on my angle grinder.

I first made a mold of my 2-up seat by using spray foam and used that mold to test the shaping of my built up foam rubber. Here it is built up ready for another layer and then fitting a layer of gel on top:


The gel is 3/8" thick shockteck gel https://shocktec.com/product/motorcy...sert-shocktec/, the standard 12" x 18" size was enough. This gel can be cut to size with scissors and will retain its shape. It is not the stuff that falls apart if not held in its original containment bag. If you order some be sure to call and talk to them about it. I sent an email and rather than answering my email, Tom called me and told me everything he could about what materials to use and how to use them.

Here is the gel trimmed to size and then covered with a layer of their air2gel foam:


The air2gel layer is to have some buffer between the gel and the final skin on the seat to prevent the gell from absorbing too much heat as it will if uncovered. Tom told me I could also use other cheaper foams on top of their gel, he recommended an open cell foam. I didn't want open cell because I want something that doesn't absorb water and I also didn't want a thick layer on top. So their Air2gel foam fit the bill because although he says its technically "open cell" it doesn't absorb water, and even their thinnest at 1/8" thick is strong enough to not break down in this application (one application for it is body armour). But, if you are wanting to use this air2gel, don't just order it off of their website as you have to special order it without the skrim layer that it usually comes with. Tom was pretty clear about that. He said they don't always have some in stock without skrim but I was in luck and they did have some:

More coming probably tomorrow...

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One thing to add to the shocktec gel information is about glue. On their website they list glues that work with their product: https://shocktec.com/specs-and-msds/ I used one from that list, 3M High Strength 90 Spray Adhesive and I did not have great results.

Now the gel comes already sticky on one surface with a removeable plastics film covering the sticky surface. That sticks well. I just sealed my gym foam base with some contact cement. let it dry then peeled off the protective film and laid the gel on top. It isn't going anywhere, it is stuck. The issue was trying to glue the air2gel to the gel. That 3M glue sticks great to the air2gel and also sticks to the gym foam (and lots of other things). But doesn't stick very well to the gel. The best I could get it was to apply a thin layer, let it sit overnight and then apply another thin coat of glue and then stick the air2gel to it. But if you pull hard enough the glue just comes right off of the gel. Maybe I needed to experiment some more, or try a different glue, but I went with 2 layers of 3mglue and it mostly stuck. It'll end up sandwiched firmly between the gel and the leather cover in the end and wont go anywhere.

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To cover this seat with vinyl would have required an industrial sewing machine so I went with leather which according to my research I could wet form to the shape of the seat and hand stich together. Wet forming I learned works best with Veg Tanned leather. The link for what I bought leads to a "page not found" error but my order says it was "Superior Oak Veg-Tan Single Shoulder, 4-5 oz". I was more than enough. I used about 2/3 of it. according to what I learned, if tooling the leather you should use 8-9 oz, but for no tooling 4-5 oz should be heavy enough and it is much easier to wet form than heavier leather.

For colouring the leather, I wanted black anyway and then I discovered a way to colour leather black without dye using a home made brew made of vinegar and steel wool called vinegaroon. The best description of it I found is this: https://leatherworker.net/forum/topi...uve-ever-made/. I used 3 liters of regular household vinegar with one full package of 0000 steel wool. It took one week for the steel wool to all dissolve and then it was ready to use: here is the a picture of the leather before colouring, and another after soaking in the vinegaroon for just 20 minutes:


I was amazed that it actually worked as described. After colouring I dumped the leather piece in a 5 gallon bucket of luke warm water to rinse of some of the vinegar smell, then again in another bucket of fresh water, and again in a third bucket. I opted to heed the advice of those who say not to neutralize with baking soda as the leather needs to be a bit acidic. I had my seat ready for wet forming the leather as it came out of the rinse water. I had a piece of Sheetmetal cut out around the seat to clamp the edge of the leather on to and my spray foam mold weighted down on top of the seat:


before doing this of course I adjusted my spray foam mold by adding a new thin layer of spray foam just to make it conform exactly to the actual new seat rather than the original seat. The new seat I made was close, but not exactly the same. You are supposed to keep the leather held in the form until its dry. But it wasn't drying, I finally figured out I could place a dry towel between the leather and the spray foam mold, press for a few hours, then use a new dry towel and keep changing towels till dry - like using towels for drying wool sweaters. The above photo is I think while the leather was still wet. It took a few days before it was completely dry.

The leather for the underside of the seat was actually more difficult to do. Those outboard spring mounts made it particularly difficult and in fact made it impossible to make in one piece. So I cut it in the back and laded it together afterwards. Regular spring mounts would have been easier and could have been done without cutting the back of the leather. But the junk of leather I had was a slight bit too narrow to get it all in one piece. So since I was cutting it in the back anyway, I was able to cheat and make the whole underside narrower than it should be and force it wider while wet forming. Here you can see it shaping around the outboard spring mounts:


And finally the finished underside ready to place back on the seat and mark out where to punch holes to match the topside which you can see around the edge of the seat here:


The underside leather I soaked in vinegaroon for a full 1/2 hour and it actually came out blacker than the top piece.

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Lacing the top to the bottom was actually quite easy, just very time consuming. based on this article: https://leatherworker.net/forum/topi...ep-seat-build/ I used 1/8" holes and 1/4" kangaroo lace. I got 12.5 yards of kangaroo lace https://www.springfieldleather.com/M...dage=6&width=3 and it was enough to lace the whole seat with about 8 feet left over.

Spacing for the holes, I kind of guessed. I counted the holes in the seat of the above linked article and counted 100, based on that I made my holes spaced centers 11 - 12 mm apart - I ended up with 109 holes. I trimmed the edge of the leather 7 mm out from the center of the holes. I think 8 or 9 mm would have been better as the weave was a bit too tight on the underside in some places. It did work and looks good but would have been slightly better with another mm or 2 of room to fit the lacing. Anyway, here it is with just the top piece of leather and then the whole works laced together:


The kind of lacing I did is called "Mexican basket weave" and there is pretty good video tutorial at https://tandyleather.com/blogs/leath...etweave-lacing.

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I'm still waiting for a chance to road test this seat (and the bike of course). I thought I'd be testing this weekend, but I ended up with a dud battery so now have to wait till a new one arrives and till I can build a tray to mount it.

In the meantime, 2 more photos, the back where it is stitched together, and the underside