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minto wheel- anybody built one
By Kwazai, Section Reviews Posted on Wed Dec 06, 2006 at 05:36:51 PM MST
other than mother earth news

I wanted to put together a small (2ft. diameter) minto wheel and have been looking at various fluids other than liquid propane and methylene chloride. r-134a is an option as well as aqueous ammonia. I was wondering if anybody had built one (other than mother earth news). I was planning on using black iron pipe fittings and a bicycle wheel--kind of a 6 legged swastika looking thing. The questions I have are in regard to r-134a and how to get the correct 'charge' into the piping. the 'legs' would have a schrader valve on the ends.
(r-134a)Can I just charge it from a recharge size can from the auto parts place and bleed it to the correct total weight to get the liquid right or do I have to pull a vacuum first to get all the air out?
(aqueous NH4+) I am assuming I would need to do something similar to the methylene chloride described here-
http://www.keelynet.com/minto/minto2.htm
I am under the impression that the nh4+ should be sufficient at 120F to get 2ft of head pressure.
(I always am concerned with the keely stuff not being right...)
Mike

minto wheel- anybody built one | 7 comments (7 topical)

Re: minto wheel- anybody built one (3.00 / 0) (#1)
by dinges on Wed Dec 06, 2006 at 11:20:58 AM MST

I'm not an expert on Wonderwheels (TM) but I know someone who has built one:

http://www.fieldlines.com/comments/2005/5/10/164555/390/3#3

Do a google on this board for 'Wally Minto Wonder wheel' and see what comes up.

I bet many more were built. So far, I don't remember reading any succes stories about it. Which doesn't mean it doesn't work, of course.

Question: have you read any stories about people who built that wonderwheel and were satisfied with its performance? I did a quick google on the web and I've found lots of drawings & plans. No finished wonderwheel that worked. Caveat emptor.

Re: minto wheel- anybody built one (3.00 / 0) (#2)
by stop4stuff on Wed Dec 06, 2006 at 04:07:38 PM MST

with a 2ft dia, you might consider a RotaColaSoda...
http://www.rotarystirlingengines.com/rotacola.htm

Re: minto wheel- anybody built one (3.00 / 0) (#3)
by RP on Wed Dec 06, 2006 at 08:02:47 PM MST

Acetone should do fine in this application and it's still readilly available at harware stores. Since methylene chloride was deemed to be cancer causing it's not as available.

Personally I'd avoid ammonia. It's flammable and highly toxic plus it's used in the manufacure of methamphetamine so expect a lot of hassles just trying to get some.

Re: minto wheel- anybody built one (3.00 / 0) (#5)
by Kwazai on Thu Dec 07, 2006 at 07:16:54 AM MST

I was thinking garden variety grocery store aqueous ammonia(17% ammonia(26 baume?) with water), but I'll definitely check the numbers for acetone-there's bound to be a heat of vaporization/boiling point/pressure/temp chart for it somewhere. thanks.
With the ammonia I'd figured on the boiling point being around 120degF and the sg at about .95. U shaped or l- shaped pipe legs rather than bottles with tubing into the bottom. The previous one I built used upside down 2-liter plastic bottles/nylon tubing and the caps leaked at a low -low pressure spraying it everywhere. best guess was approx. double(cp/cv mixture approx. 2.37) the volume in ammonia vapor to push the water to the opposite side. the ammonia should adsorb(desorb?) with the water on the cooling side. I had run some tests previously with a wok and a 1/4" tubed 12oz plastic bottle and was able to get the water part to rise about 48" in the tube at 140F from the ammonia vapor it created (got leaks then...). will definitley be using pipe fittings this time.
Mike

[ Parent ]

Re: minto wheel- anybody built one (3.00 / 0) (#4)
by Countryboy on Wed Dec 06, 2006 at 10:56:55 PM MST

The 'correct charge' will be a liquid amount that can be contained in less than 50% of the volume of one tank. (Any more than 50% will run back down the tube to the empty tank.) It isn't necessary to have equal amounts of ammonia in each canister pair, as each canister pair is a separate system isolated from the others.

You don't want air in the system, but you won't have to use a vacuum pump to remove the air. The ammonia or freon you use will vaporize easily - as long as you have a relief valve opened, you can use the ammonia or freon to 'blow' the air out. Then, close the relief valve, and fill.

This diagram shows some bad information.

The evacuated tanks should be at the bottom of the picture, not the top. The full tanks should be at the top of the picture.

Please note that the tube between the tanks does not stop at the edge of the tank. The tube extends into each tank. This makes a valve. The hot gas goes up the tube to the upper tank, and condenses in the bottom of the upper tank, but is unable to run back down the tube because the tube is higher than the level of liquid. If you fail to make this valve, you will need the vapor flow to constantly 'blow' the liquid to keep it in the upper tank, which you will find to be very difficult.

Re: minto wheel- anybody built one (3.00 / 0) (#6)
by Kwazai on Thu Dec 07, 2006 at 07:29:35 AM MST

I was thinking something like this out of pipe fittings, but the ends may work better in a Ushape rather than an L. I am leaning towards the L- end of the tube being 1" pipe or bigger with 1/2" or 3/8" connecting pipe. with it being pipe and being larger sizes than a drinking bird it will heat/cool very slowly so I would not expect a great rate of speed out of it.
Mike

[ Parent ]

Re: minto wheel- anybody built one (3.00 / 0) (#7)
by wdyasq on Thu Dec 07, 2006 at 08:30:53 AM MST

My advice, and I spent money building a large one 30 years ago, is to follow someone's successful plans. If you can't find successful plans, it may be a clue.

Ron
Adventure is just bad planning." -- Roald Amundsen

minto wheel- anybody built one | 7 comments (7 topical)

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