<center><img src="http://pictureposter.audiworld.com/711/altubing.jpg"></center><p>
Hint: It's 3" O.D. 6061 series seamless aluminum tubing with a .049" wall thickness and 3 ft long and I have 7 more just like it.

Mr D: you already know so don't even think about it;-)

<center><img src="http://pictureposter.audiworld.com/711/roughstack.jpg"></center><p>Turns out 6061 aluminum doesn't like to be cold-swaged to this extreme. I split 4 of em right down the side before I gave up trying to get the angle I wanted. And since so much hand holding of the part is neccsary I cant do em hot either. So I annealed em with a torch to about 800-900 degrees and let em cool on their own without quenching. That seems to work just fine, making them far more maleable.

You can see how the oxy/acet torch soots em up and heat discolors em with the O2 turned off when torch annealing. I'll fire up my plating oven later when I have a number of them cut to size so I can do 30-40 at a time.

Next I'll true em up on the lathe and get the exact inlet contour and flat base then de-burr and high-speed finish them on the lathe with rouge until they appear like liquid mercury and everyone should be pleased with the fit/finish.

... that you were going to put eight 3" tailpipes on your A4! I figured you'd look like Super-Rice or a mini-scale Patriot missile launcher! ;-)

Bob K.

that had a reinforced breech area 6" thick tapered to a 2.5" barrel. Thing launched potatoes over a mile at 3270 feet per second at a 4,700 psi compressed air charge. Was a fun project but the air pressures are a little scarey to deal with. And I still lost the distance contest by over 700 meters. Win some lose some. The secret is good ammo. Most spuds disintegrate 18" outta the muzzle.

<center><img src="http://pictureposter.audiworld.com/711/polishstack.jpg"></center><p>Outside lightly polished while the business side is polished to a high lustre.

high speed photography???

<center><img src="http://pictureposter.audiworld.com/711/chronograph.jpg"></center><p>
shot to shot consistency, ft lbs of energy, et al. It has two optical sensors 18" apart and times the spud between the first one and the second. You get a good "start" signal at the muzzle but the second sensor never gives a reading due to potato atomization.

Here's a pic of mine. You can see it's optical ports in the top at the front rear. Simple and incredibly accurate using time-to-distance by having the sensors daylight sensing interrupted at two sources then chronograph measures elapsed time between them and internal computer converts to fps (feet per second). It'll also do a ton of other processing, ie shot-to-shot consistency, mean average deviation, standard average deviation over pre-selected groups of shots. Indispensible tool for spud artillery or any other serious match airgun or firearm competitor.

So truthfully it was less than 18" before the spud didintegrated but 18" is the distance apart of the sensors so I just use that figure. Maybe it was 3", maybe 11" but at 18" it was only potato vapor.

For Audi content if you run two of these in series you can also measure any 0-whatever speed with .0000X of a second accuracy.