DIY Aluminium café tank possible?

Gordon

Been Around the Block
I'd like to try my hand at building a simple aluminium motorcycle cafe racer tank for my Royal Enfield. Need help on the following:

  • What guage sheet?
  • How do I weld? I've heard aluminium is difficult to weld. I know of someone who can do "electric welding".
  • How do I ensure that there is no leak?
  • Mounting points?
  • Does anyone have drawings that I may use to cut the sheet?
  • Please add in any other relevant information.

I've never done this before. This is all new to me, but I somehow imagine it can be done.

Don't know if I've posted this earlier. Anyways please help me as always.
 
This is what I'm looking out for. The red one is more appropriate ;D

electra-sportsman-rear.jpg


les2ts4.jpg
 
I noticed that you posted this info at MetalMeet, which is a good place to search for this info.
Anyway, to answer some of your questions:

What guage sheet? 3003 AL around .063 (16 gauge I believe)
How do I weld? Two choices, gas or arc welding (TIG). Welding AL can be tricky. It is very easy to blow through because you have to use a lot of heat and move quickly...not to mention trying to keep track of the puddle.
How do I ensure that there is no leak? When the tank is complete, pressure test it by capping all openings (petcocks, fuel filler) and injecting low pressure into tank will submerging tank in water. Existence of bubbles indicates pinhole leaks.
Mounting points? Those wil have to be fabricated to fit the mounting on your frame.

The first thing you need to learn is how to metalshape. You need some simple tools to do that. The most basic tools you need are a hammer, sandbag and a hollowed out wood stump.
Go to the MetalMeet site and do a search for 'getting started with metalshaping' or something similar.

To do a tank like the ones indicated, you need a buck to reference against. Do a search on MetalMeet for 'making bucks' and 'flexible patterns'.

What you're attempting to do isn't easy, but it can be done.
I speak for experience because I have made a gas tank for a motorcycle, and am currently making another one for a Cafe style bike.
 
I'd start with a panel sided tank, basically just flat sheets welded together at the corners. You could easily taper one end with simple bends in the metal, but without complex forming. Something like a Honda CR750 style breadbox tank (which I happen to love). No nonsense functional tank.

One day I want to learn to weld, but frankly for the costs involved in the hardware setup, I can't justify it at the moment. I spend about $300 on having pros do all the welding I needed done on my 650 project, including materials. I'd have to do a few projects to get the equipment paid for. Granted I'd have the satisfaction of doing it myself, but I don't think I'd trust my welding skills on my motorcycle frame :)
 
Okay forget the aluminium tank for now. Lets just concentrate on normal sheetmetal :-[

I was just thinking how I'd have to cut the sheetmetal in order to make a simple tank that resembles the above red tank. This is what I could come up with. It doesn't have a lot of curves.

The below pic is a rough design. Its only of the top and side parts of the tank. Black lines indicate where I have to cut. Lightblue area will be overlapping to create the round shape in the front.

  • Should I go ahead and make a miniature tank first?!
  • Are any changes required?!
  • Or is the drawing just crap and NONSENSE and its not possible to make a tank with this design?!

cafetankan0.jpg
 
While that cut pattern you posted may work, there are better ways to accomplish what you want.

I would suggest that you make a full-sized buck of your tank. This is the buck for that tank I am building:
P1015681_640x480.jpg


From the buck you can make a flexible pattern, that along witht the buck will help you to quite accurately shape your desired tank.

Here is some of my metalshaping progress so far on my tank:
P1015810_640x480.jpg
 
That's impressive - is it the left side so far you've done, or does that extend down the right side too?
 
What is pictured is just the left side. I have started working on the right side and have the basic shape achieved like the left.
The next steps are to carefully stretch the sides to fit tightly to the buck...and then create the tunnel and the knee cutouts.
 
Wow! Thats very well done!!


That's impressive

I agree. That is very impressive. I would love this shape, but then I don't know how to curve the tank and I do not have the experience and expertise in such advanced metal working.

Which is why I opted for the less curvy tank to start with. Moreover, I also have no woodworking tools and experience to make a buck. I know I'm jumping into an unknown area and trying to create a tank without a buck :eek: If it gets too complicated I'll hire an experienced helper.

  • What guage sheetmetal did you use?!
  • And how big was that sheet?



And the most important questions:
  • Will the above layout work?! Yes/No
  • Does anyone have an alternative layout?! Or a drawing of how I'd need to cut the sheet?!
 
Gauge of sheetmetal = 18
Size = 2 pieces approx 15" x 25" each.

The layout you posted probably will not work to achieve the tank style you want. If you want more of a breadbox shape, something Tintin pointed at earlier, than yes you may be able to use it.

The red tank that you want to make, even though it isn't as curvy as the one I am building, it still has low crown compound curves...picture a shallow bowl. The only way to achieve compound curves is to metalshape (stretch the metal by hammering into a stump and/or sandbag).
 
One thing to keep in mind about aluminum is it doesn't like to be bent on a sharp angle - weakens it. You can't fold it like you can steel. So I'd think you're still better off cutting up panels and welding together a box.

I am still a HUGE fan of the Honda CR750, a tank style that would be easier to emulate than the softly rounded curves of a British style alloy tank.

http://www.airtech-streamlining.com/hondaz/CR7501969-77SINCAM.htm
 
I've been searching for another Enfield for two months. Unfortunately I stilll didn't find one. Its difficult to find one for sale and when you eventually do, they quote a ridiculous price.

Thought I'd work on the tank on the next bike, since I just cannot and don't want to touch the original chrome tank on my current bike. I just seen this tank on Benjie's Cafe Racer and it seems even more easier. Its sort of boxy with mimimal curves at obvious places.

Is it remotely possible for anyone to just draw the dimensions or the shape in which I'd need to cut sheetmetal?!

P1010071-239x214.jpg
Picture_130-242x213.jpg
 
I think your best bet is to mock one up by carving some foam blocks or something. Then you can use heavy paper to cover the shape with whatever logical peices are required. These pieces then become your template for cutting out the aluminum sheet.

You're not going to be able to cut it from one or two pieces and then bend everything. Even if you could get one or two bends done, as you bend each panel, making subsequent bends is going to become more and more awkward/impossible.

Start practicing welding aluminum sheet together - make some simple boxes etc, and test them for being air-tight. Then move on to welding a tank together.

The tank in your pics looks like it could be done with three large panels to form the upper part of the tank. One stretching from the seat, up and over the top, and then down to the front. Each side could be a single panel. Then you need to form the tunnel, weld it in place and then fill the gaps between the edges of the tunnel and the sides of the tank.
 
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