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Old 04-08-2010, 09:49 AM
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BarelyAWake BarelyAWake is offline
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Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default Re: DIY tank... even if you can't weld

Clamping the two side panels together using popsicle sticks to pad the C-clamps and making sure to not crank 'em down too tight (metal distortion);

I started bringing down the steel till the two pieces were flush and to the indicator line. I started with a Dremel of course, but this leaves a wavering finish with low and high spots no matter how careful you might be, but if ya always make long, sweeping passes it'll reduce the amount of "dig-out" and result in smoother lines. For the outside curve and flats - I used a large, flat file much like you would a planer. Slow and somewhat tedious, it's really the best method for getting a nice, smooth, regular surface - particularly on an outside curve. Inside curves are the same deal - ya just need a 1/2 round file (bigger = better) and remember - long passes result in less irregularities and "even out" high and low spots.

The two panels now about as identical as humanly possible and this is where I call it quits for now. Although it's tempting to round the corners to what it's "supposed" to be - it's far, far better to make the top and bottom panels and bend those first, then grind the rounds on the sides to fit. While I know what shape/angle I want the bends to be - no amount of planning can account for the real world and I'm sure the rounded bends wont be quite exactly as I thought they would be. I'd rather wait to grind and test fit then guess and hafta try and put metal back lol Also... the math gets tricky with mutable bends & curves... and math was never my strong suit heh

Most of this back & forth, test fitting & shaving a bit more off is simply due it being a curved tank and the fact it's a "one-off" - the first attempt at a product you've not made before. Should you ever wish to make another - it'd be far easier as you'd already know what shapes you'd need and if'n yer clever - you'd have used the original bits to make "finished" templates before ya weld them together. Even tho I don't think it likely I'll ever run into another, identical Rollfast that needs a real fuel tank - I'll be makin' 1/8" thick, epoxy-coated plywood trace templates for each piece... *shrug* Ya never know - I might dent this one and want another, maybe - just maybe someone else will have a Rollfast and those bdanged templates are where all the effort is...

I've done three test layouts for the top and bottom panels, the first two proving yet again that there's a huge difference between "planning" and the real world lol

My first idea was to have a somewhat angular tank, sorta coffin shaped if viewed from above. It's quite important for the tank to have a fairly abrupt taper in the front as the rear forks for the springer will hit it when I turn the handlebars all the way to one side or the other. Too wide and I'll limit the steering - too narrow and I'll not only have a dang strange lookin' tank, it wont hold much and I'd be forced into havin' a pinhole for a fuel fill. While some cap will be smaller than normal - I really don't want to be forced into using a funnel to fill the blasted thing.

So while the angular tank looked great in my brain, when I got around to draftin' out the shapes it jus' didn't work. Sure - I got it to all "fit together" (sketched out anyway) but it jus' looked stupid as heck. The sides will be rounded front and rear (they're only angled in the pics 'cause I've not ground the rounds yet) and the clash of rounds and angles combined with the gently swooping frame was too much to bear. Additionally, the taper in the front needed to be so abrupt to give me the flat sides where I wanted 'em... well... trust me - it looked really bad lol

No materials wasted tho, as I didn't cut anything and it's funny how easily Sharpie wipes off with a lil acetone FTW. My second attempt was similar to the first just with the bends/angles in slightly different places, but with the same disastrous results - they offended mine eyes. More acetone and back to the drawing board.

I really don't know why I had my heart set on angles... they don't make the math any easier and the Rollfast is all curves so I shoulda known better *shrug* For whatever reason that's what I had envisioned from the moment I thought about makin' a tank and bein' a stubborn fool I ignored alla my past experience and tried to make it work anyway. Sure - I could make it work, I've even finally figured out where the bends need to be - but on my third attempt I jus' grabbed a batten (jus' a thin strip of scrap plywood to plot curves, ply so the grain doesn't effect anything) and did a test curve... lo and behold, a classic curve pleasing to the eye with alla various widths in all the right places o_O BTW, battens are also handy for figurin' out what the length of a curve is if flattened out - bend the batten to the curve - mark, flatten and measure. Ya can use a bit o'string... but it tends to get all squirrely on ya.

K - so I'm going to have a curved tank then heh, it's sometimes a lot better to listen to what the materials have to say than my silly brain;

This is actually just my test piece - I'll be cutting out just the top half of the drawing, the bottom isn't to scale and is just there to help me envision the shape. Once the top half is cut, I'll use it as a trace template and flip it over to get as close to a symmetrical, mirrored shape as possible. While battens are great for plotting nice curves - you'll never get quite the same shape twice so it's best to not rely on 'em too much. The 1" band going down the middle is the top tube of the frame, the straight lines comin' off the ends are for the wrap-arounds front and rear. As they'll need to be some mysterious hourglass shape from the sides tapering in - I'm gonna wait till the rest is cut and I can bend them into place and trace. Yeah, I could use the ol' math... but we've already discussed the insidious shortcomings of my brain;

While it's all ready for the jigsaw... it's also about 5:30am here and despite all my threats of audio revenge - I'm still jus' not bastid 'nuff to make screamin' sheet metal death noises and wake the entire house.

Ah well heh
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