|08-01-2004, 06:25 PM||#1|
Joined: Apr 2004
Making washers out of aluminum flat sheet
,for welding in between the inner tube of a can, and the outer "sleeve" ain't easy, but a lathe really helps. Use a kid's compass to layout the OD of the circle. hack saw out the strips, cut them into squares, center punch and drill their centers,mount them on a 3" long bolt,which has a nut at each end of about 1" of thread, along with a lockwasher. chuck up the protruding 1/4" or so of thread, center drill the bolt head, use a live center to mount the bolt head to the lathe's tailstock. Now you can spin 6-8 squares into circles of whatever OD you wish, and deburr them.
Now comes the touchy part. Open the jaws of a caliper to the width that you need, and lock the caliper jaw. Use it to scribe a line all around the circumference of the washer, marking the ID that you need, so that the washer will neatly fit in between, say, a 1 3/8" OD tube and the ID of the 1 3/4" sleeve tube.
Mount all 4 of the washers in the chuck, and don't tighten the chuck enough to deform the washers. Use increasing sizes of drill bits to remove as much of the unwanted metal as possible from the center of the washers. After you have used your largest drill bit, you have to start using a boring bore. Perhaps the hole in the washers will still be small enough that you have to MAKE such a boring bar, out of a small lathe bit, ya know. Using a very sharp boring bar, high rpms of the lathe, and light cuts,you can perhaps get very close to the ID that you want for the washers, before they weaken enough that they collapse in the chuck, enough that they are no longer held securely. Use your caliper to keep checking for roundness of the ID hole you are boring in the washers. When they start getting egg shapped, you have to clamp them in a vise grip, one by one, and use the Dremel grinder and a couple of cutting disks, or the sanding drum, to finish making the washer's ID large enough to slip over the smaller "inner' tube of your can.
Sleeving a can, venting the rear half of the inner tube into the sleeve area, makes the can far lighter, more efficient. It gives the hottest, highest pressure,dirtiest gases a place to go, instead of carboning up, melting your screenwire donut baffles.
Washers, of a much smaller ID than the baffles in the vented area, serve to make the gases right near the muzzle go out into the area between the 2 tubes. These vented off gases have to travel to the front of the can, meet the welded up washer there, then FIGHT more gas to bounce back to the rear of the can, and fight to get thru the baffles AGAIN, to FINALLY exit the front of the can. T
The gases that are not vented into the sleeve-area, are dealt with by the alternating ID hole size baffles in the front half of the can,along with the small ID washers that are placed at the end of each of the small ID screeenwire donut baffles. That is, the washer is away from the muzzle, on the side towards the front end of the can, atop each neoprene "wipe". The neoprene washers have too big an ID hole to be real "wipes", but they still serve to stop any gases that are trying to filter their way thru the screenwire. So they are worth including in the design.