news6.htm Tri-Mode ARLA

Amateur Rocket Launch Assist (ARLA)

Newsletters and Random Thoughts

This page will include progress reports, notes, random brain farts, and other ramblings.


August 16, 2000

Sheet Metal

I was informed about another source of sheet metal that sounds promising. A.M.Foils, Inc has provided me with the following information.

   .010" x 24" x 10 ft
   302/304 Annealed, Half Hard or Stainless Steel 
   $90.00 plus freight.

   A.M. Foils, Inc.
   11616 McBean Drive
   El Monte, CA  91732

   Phone    (626) 279-5830
   Fax        (626) 279-5851
   Email     thinmetal@earthlink.net

I haven't used the 0.010 I already have but after having handled it I think 0.080 might be better for the body and 0.060 or 0.040 for the flame holder.

I'm open to anyone else who has materials/parts suitable for use in making ramjets.

Sept 4, 2000

Forward

Last weekend I finally got all the water tanks, lines, and faucets in, which is why I was able to get back to the ramjet work this weekend. The water work has taken much, much longer than expected but it had to be completed during the summer weather and with a minimum of delay. I still have to get ready for winter but there's time for that.

Blower for Freejet Tests

I picked up this little blower from a local salvage yard. It's a Westinghouse Electric axial fan for ventilating mine shafts. It originally ran with an electric motor, about 25 hp I think. The motor was mounted on the side and three v-belts ran from the motor to the aft end of the shaft. I hope to drive it directly through the front with a drive shaft from my tractor. If I can't get the rpm I need then I'll pick up an old transmission from the junk yard.

The front and back covers are off as well as the pulley. I'm checking out the bearings and repairing the grease lines.

..

The blower measures 43 inches long, 33 inches inside the duct, and 16.5 inches across the bearing support tube. I may have to do some duct work on the back end to smooth out the flow (the bearing support tube comes with a flat back) and narrow it down.

Lightweight Steel Fuel Tanks

Here are the makings of my fuel tanks for model airplanes. I've taken two spray starch cans (from the 99c store) and cut the bottoms off. From one I cut another 3/4 inch band which will be brazed to form a double lap joint between the two cans. I drilled out the nozzle of one (leaving the plastic nipple intact) for filling and drawing fuel. On the inside I'll attach a fuel line, possibly a flexible hose and clunk. The other can nozzle I left intact. These come with real nice valves for pressurizing. They work with a butane cylinder just like filling a cigarette lighter.

..

Butane is often used on these types of cans as the pressurant. Just to be safe I took a similar can (shaving cream) and put some liquid butane in it. I then set it out in the sun to cook. No problem.

Together these two cans will weigh about 1/2 lbm and hold a little over 2 lbm fuel. Using the same technique a much longer tank can be built with little added weight (it's the ends that weigh the most). If I can find bigger cans that would increase the volume also. Aluminum and other materials would be lighter but I haven't seen any I like yet.

New Flame Holder Design - Lotus

I know, it sounds corny, but that's the name that came to me. The idea is to shorten and lighten the engine. I didn't have time to try this one today but wanted to show it anyway.

..

This design combines aspects from an early design that worked very well and some ideas I've come up with recently. The "petals" are similar to gutter-type flame holders. I may even crease these to get the v-shape. The rectangular holes above these are to allow flame and fuel to exit the pilot and keep the gutters lit. The problem I'm trying to solve is getting the fuel heated and distributed somewhat evenly throughout the airflow for a better total exhaust temperature. This is important for max thrust and efficiency.

Sept 17, 2000

Fuel Tank

I built my fuel tank. Rather than connect to the plastic nipple I drilled the plastic out and put in a brass tube. At first I tried to braze it in but that melted the brass tube (duh!). So then I soldered it in. Since the hole it went through was small the solder held just fine. The braze job holding the two tank halves wasn't showroom quality but good enough. Once built, I pressurized it with butane and set it out in the desert sun for a few hours. No problem.

Butane as a Fuel Tank Pressurant, Not

I filled the tank with mineral spirits using my automotive fuel pump and letting air out the aft valve. This worked great. Then I tried to pressurize the tank with butane. When I opened the valve I got about 5 seconds of low pressure flow then almost nothing. I emptied a butane cylinder trying this. So then I decided to drain the tank and the fuel came out with lots of bubbles.

What was happening was the butane was being absorbed into the mineral spirits, kind of like carbonation in soda. It would take a lot of butane to get good pressure and then it would not flow properly into the engine because of the bubbles. So much for that idea. The same happened when I used propane (being careful not to overpressurize the tank).

I now have to figure something else out. I probably should try one of the refrigerants. I would like something that changes phase from liquid to vapor. This can be stored in a small container that doesn't weigh much.

Fish Tank Air Valves

The valves I bought from the fish store worked very well. They completely cut off the flow, are easily variable, and, for the most part, don't leak. They came as two valves with a steel tube connecting them. I cut them apart and used hot glue to seal the tube. Mineral spirits disolves the glue. Next idea?

Big Fan

I'm still trying to open up the fan. I couldn't get the collar to come off the shaft so I decided to remove the four bolts holding the fan to, what looks like, a flywheel. I finally had to grind the heads off the bolts (these have 3/4 inch shanks, heads about 1.25 inch across. Now I can't get the aluminum fan off the steel flywheel. Many hours, no progress.

Sept 18, 2000

Plastic Fuel Tank?

In looking for alternative fuel tanks I decided to try out a 2 liter Pepsi bottle. I poured in a few ounces of mineral spirits and set it out in the sun. Three days of 108 F daytime and 65 F nightime and the bottle shows no sign of weakening, hazing, or discoloring. It might as well be water.

A friend who is serious about using these bottles for water rockets has tested them (with air and water) to destruction. They consistently burst at 130 psi which is pretty good, though not necessarily crashworthy.

Diflouroethane Pressurant?

I filled a plastic bottle with mineral spirits and bubled diflouroethane through it for about two minutes. There were no residual bubbles or any other indication that any of it was being absorbed. I capped the bottle for five minutes then opened it. There was no pressure buildup.

Diflouroethane is also known as refrigerant R-500 and has a 70 F pressure of 85.3 psi (www.c-f-c.com/Specgas_Products/). I got mine in a can of spray gas from the local computer store.


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This Page created September 4, 2000

Last Updated March 14, 2001