Fan housing fabrication

oK, I'll simplify to hopefully get a better chance at a response...

I built a cylindrical housing for a fan to be used as a supplied air system from sheet scavanged from a water cooler. It was fairly thick so bending it into a tube was tough, I managed to do a series of creases that comes close, but I'm wondering how to get a more even curve?

[hardtailjohn]

The ideal would be to use a slip roll, but I've seen it done with a guy holding the sheet over a rail or pipe, using some form of solid clamp the full length of the side, so you don't get a kink in it, and working it that way.. I've even seen guys use their hands at that point to work aluminum down to a curve..
I would imagine there will be more ideas here... these guys are awesome!
John H.

[rkilgore29]

Are you looking to close the remainder of the cylinder? I am going to take a leap here as it appears that you are. If that is the case you can use a large band clamp (hose clamp) that will reach around the diameter, a ratchet strap or even a piece of rope tied around the circumference and twisted with a stick. There are other options that work in a similar fashion. Using the band or other device for tension coupled with a hammer and your welder you shoud be able to walk the remining cylinder wall around until it meets the beginning. You simply apply tension pulling the wall in, hammer where necessary and tack weld it when you get it where you want it. Beyond this getting a more smooth curve at this point will likely mean removing the end caps and spending a bit more time trying to finesse it around something like a section of pipe or something like that. When you use the end caps to create the radius, the ends come in pretty well but the center section will often be less than perfect. It is best to get the radius correct before you start tacking the parts together. If you lack access to a slip roll or other sheetmetal equipment you can acheive satisfactory results by carefully working the part over a piece of pipe or even a 2 X 4 edgewise. The idea is to exert localized pressure using your hands and body weight by bending it over the pipe or 2 X 4. If I have missed the leap I hope I land in a soft spot<grin>.

I was thinking about the cone section you were thinking of making from the skin off of a water heater. Some of that stuff is galvinized and may not be the best choice for your application. If you decide to go forward using this material you may want to consider not welding it as a means to attach it to the cylinder. Welding galvinized releases fumes that are not good to breathe and if you are not able to clean the finished part well, you may continue to breathe in contaminants when you use the apparatus.

Thanks for the replies. I didn't even really know what a slip roll was, that's exactly what I was looking for though... I looked it up and it seems like I could make one if I had the time.

I closed the cylinder by clamping it and hammering it down, tack welding... same for the seam down the side. It worked but doesn't look so good. A hose clamp or rope would have worked even better though, I'll file that thought away for next time.

I realized that sheet was galvanized and decided not to use it, I used poster board and duct tape instead. Doesn't need to be strong so it actually worked great, I went with fast and easy because I just don't have the time.

The system is all done and running and I'm really impressed with it. I used 4" flexible foil ducting to run to the middle of the garage and then a 3" ABS section mounted through the wall with 1 1/2" fittings coming out into each room. I have caps for the 2 not in use and 50' of 1 1/2" PVC hose running to my mask. I can walk into any room, put the coil of hose on a hook, plug it in and I have supplied air. The air flow is perfect, not too much to dry out my lips but enough that no air seeps into the mask when I take a breath.

If anyone wants more details or pics I can do that. It's great for welding, doesn't interfere with the welding mask like a canister would.