Lever
!/j"x9"
w,th
welded counterweights* Sec DctO'l "A"
Tilt lever to fill
A Home-Made x 7 Sand Blaster A NYONE WHO has ever cleaned paint and rust off an old steel tubing airplane structure knows what a boon a good sand-blasting machine would be. Sometimes you can find one in a city, but even then it's a problem whether or not its owners can or will handle a job the size of a fuselage. For many, a sand-blaster is as far away as the moon. Shown here are drawings for rigging up one of your own at modest cost. The prime requirements are a source of suitable sand and a compressor large enough for the job. Manufacturers of commercial sand-blasting equipment sell special grit, but you can get by with common dry sand sifted through insect screening. Any industrial compressor of the size commonly used at gasoline stations and aircraft repair shops will do well. This would be something on the order of a machine delivering 14 cu. ft.
of air per minute at 80 lbs. pressure, although a smaller one might do if it has a generous size storage tank. Don't
-Form ring of welding rod
Bevel hole in VA" plate as shown to f i t gasket
Cement rubber gasket to reducer
7 V 3/4.
x 2"
screwed reducer
DETAIL "A"
Continual
weld
Union
Hose
Vs" « '/«"/ swage nipple/
S*0 Detail "B"
waste time trying to make a little one-butterfly-power portable compressor do the work. The drawings, by Robert McRoberts, EAA 2271, of
1014 Earle St., Apt. 8, Houston, Texas, are practically self explanatory. The reason why air is led into the top of the sand tank is to equalize pressure on the top and bottom of the sand. Without this feature, air would simply blow up through the sand like a geyser and nothing would flow down to the nozzle. The stopper at the top (Detail A) can be made of almost anything you might hit upon, the main requirement being that it have a good wedging action. An old valve from a big airplane engine might work, if fitted with a guide and rubber "O" ring for a seat. The tank itself could be adapted from a surplus aviation oxygen tank. When the tank is finished, use an automobile tire pump or airplane shock strut to fill it with air to about 50 percent above normal pressure for a safety check. All welding and threading must be of good quality. Take off any sharp edges! Clean out chips from the threading work. Do the welding before installing the gasket and sealer material. The valve at the bottom of the tank must be of the gate type for anything else will jam with sand. Buy 3/32 in. standard steel lettering nozzles from an industrial supply house, a monument works or from Granite City Tool Co. in Barre, Vt. You can make up your own
nozzles from rod stock, too. VA" x. Vs" screwed reducer with Ye" threads drilled out with 3/a" drill
3
/a" x. VA"
swage nipple
DETAIL "B" 36
JUNE 1965
Commercial nozzle
Close the sand valve in the bottom to prevent clogging the pipes, and fill the tank with sand almost to the level of the top air inlet. Shake down any grains left on the filler plug or its gasket. Close the nozzle petcock. Open the air shut-off valve, aim the nozzle at the work and open the nozzle petcock. Adjust the sand valve to get a good flow . . . too much sand may cause clogging. To prevent the sand from piling up in the hose, shut the sand off before closing the nozzle valve. Goggles are essential when using the machine. Don't point the nozzle too long at any one spot on the work, especially where thin stock is concerned. Do the work out-of-doors as flying sand will cover everything in a shop. Wear heavy work gloves and, preferably, coveralls that will keep most of the sand from filling your clothes. *
