mathil
Been Around the Block
Hey guys,
I started building the tank for my bike, thought I'd do a photo journal/tutorial type job on it. I'll show the whole process from plug to mould to finished part.
I started from some pictures of a "continental" style tank, and the dimensions. One like this : http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-custom-motorcycle-chassis-fuel-tank-parts-legendary-motorcycles-continental-gt1651gn.html
Everyone wants around 500$ for them with a cap, and that's too rich for my blood. Don't get me wrong, it's a perfectly reasonable price for the materials and time that goes into the parts. I deal with glass all the time, and make my own plugs and moulds for my business (pop-top van campers) so I have the materials and experience laying around. If it turns out well, maybe I'll do a run of them and sell a few to recoup the costs and make some coin...
So I started out tracing profiles on to 1/8" meranti and cutting it out to make a skeleton of sorts. It looks like what you'd see in hammer forming metal, a buck of a type. Use whatever you have laying around if you choose to make one. Mine involved the profiles, some 1/4 meranti and a cardboard tube with a 3.5" ID that a roll of fiberglass used to be wrapped around...
I had some 2 part urethane pour foam laying about the shop from my previous plug builds. It's a pain in the ass to pour in to an "open" space, and to get it to fill. It's messy, takes a bunch of pours, and looks like something from ghostbusters when you finish. I used a 2lb density. You mix part A and part B, stir for 30 seconds, and from there it's a race to pour it out of the cup before it expands.
Some people stack together insulation foam and carve out of that. It's one way to go, and definitely cheaper... 10 gallons of the pour foam (expands to like 35 cubic feet or something) costs around 500$. You can buy smaller kits for less, but you pay more per the amount you get, as usual. I like the skeleton/pour foam route because I can tune and sculpt the profiles before the foam comes into play, and the profiles give a nice guide to sand down to when you're contouring the foam. As you can see in this picture, I chase the foam down to the profiles, being careful to angle the block in the correct way. I found with the block carving that I was constantly trying to maintain square, symmetry and the curves I had decided on. With the guides most of the sanding is a no brainer. 36 grit on various blocks works great to quickly get rid of it.
From there its a connect the dots kind of thing. Sand down the high sections, being careful to sand in the proper curves. When I do the foam I try to get everything smaller, but within around 1/4" of the final shape I want. Bondo goes on next, and you don't want to have to slather on 3 cans of the stuff to get your form. The 2lb foam leaves bubble holes around 1/16" in diameter. First job is just a scrape coat of bondo to fill the holes, then a quick sand to knock down the bumps and ridges from the scrape job. From there it's all bodywork baby...
I've got a scrape coat of bondo on the foam now, but my phone died before I could snap a pic. Next update I'll go over the bodywork. Lots of tips to save time and effort, like being neat in how you "tool" the bondo instead of slapping it on, and how to progress through the grits.
Here's a pic of the tank in foam, on the bike.
Input appreciated, questions will be answered as best I can!
I started building the tank for my bike, thought I'd do a photo journal/tutorial type job on it. I'll show the whole process from plug to mould to finished part.
I started from some pictures of a "continental" style tank, and the dimensions. One like this : http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-custom-motorcycle-chassis-fuel-tank-parts-legendary-motorcycles-continental-gt1651gn.html
Everyone wants around 500$ for them with a cap, and that's too rich for my blood. Don't get me wrong, it's a perfectly reasonable price for the materials and time that goes into the parts. I deal with glass all the time, and make my own plugs and moulds for my business (pop-top van campers) so I have the materials and experience laying around. If it turns out well, maybe I'll do a run of them and sell a few to recoup the costs and make some coin...
So I started out tracing profiles on to 1/8" meranti and cutting it out to make a skeleton of sorts. It looks like what you'd see in hammer forming metal, a buck of a type. Use whatever you have laying around if you choose to make one. Mine involved the profiles, some 1/4 meranti and a cardboard tube with a 3.5" ID that a roll of fiberglass used to be wrapped around...
I had some 2 part urethane pour foam laying about the shop from my previous plug builds. It's a pain in the ass to pour in to an "open" space, and to get it to fill. It's messy, takes a bunch of pours, and looks like something from ghostbusters when you finish. I used a 2lb density. You mix part A and part B, stir for 30 seconds, and from there it's a race to pour it out of the cup before it expands.
Some people stack together insulation foam and carve out of that. It's one way to go, and definitely cheaper... 10 gallons of the pour foam (expands to like 35 cubic feet or something) costs around 500$. You can buy smaller kits for less, but you pay more per the amount you get, as usual. I like the skeleton/pour foam route because I can tune and sculpt the profiles before the foam comes into play, and the profiles give a nice guide to sand down to when you're contouring the foam. As you can see in this picture, I chase the foam down to the profiles, being careful to angle the block in the correct way. I found with the block carving that I was constantly trying to maintain square, symmetry and the curves I had decided on. With the guides most of the sanding is a no brainer. 36 grit on various blocks works great to quickly get rid of it.
From there its a connect the dots kind of thing. Sand down the high sections, being careful to sand in the proper curves. When I do the foam I try to get everything smaller, but within around 1/4" of the final shape I want. Bondo goes on next, and you don't want to have to slather on 3 cans of the stuff to get your form. The 2lb foam leaves bubble holes around 1/16" in diameter. First job is just a scrape coat of bondo to fill the holes, then a quick sand to knock down the bumps and ridges from the scrape job. From there it's all bodywork baby...
I've got a scrape coat of bondo on the foam now, but my phone died before I could snap a pic. Next update I'll go over the bodywork. Lots of tips to save time and effort, like being neat in how you "tool" the bondo instead of slapping it on, and how to progress through the grits.
Here's a pic of the tank in foam, on the bike.
Input appreciated, questions will be answered as best I can!
