Author Topic: diy cast Turgo spoons  (Read 4598 times)

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joestue

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diy cast Turgo spoons
« on: October 03, 2013, 08:53:39 PM »



I have since made another iteration to this design, and figured out how to get the spoons to nest inside each other to some extent.
I'll upload photos of the cast aluminum copies of the second iteration if i can cast more than one without destroying the plaster mold.
what you see in the photo is car battery lead + 10%(?) tin.

The spoons are about 2.5 inches long and the portion of the spoon that is flat is 1 inch wide.
the exit angle isn't nearly the 20 degrees it should be.
Looking at other commercial Turgo spoons it appears they don't bother to try and get it that low, some of them appear to be nearly 45 degrees, and the spoons do not nest inside each other either.

Mine are probably 35 but what i think i'm going to do is just tilt the turgo spoon away from the jet, so the exit angle is 20 degrees, and keep the basic profile that I have.

In theory they should work for a 3/4th inch wide jet but i don't think they would be very efficient with a jet that wide.

I've since polished one of them up and carved out the inside a bit deeper, and made a new mold.
of which i successfully extracted the metal without melting it out or breaking the plaster (wasn't that hard actually, so i can make (N) plaster molds from one master.)
I have casting sand and plenty of it but never really got it working properly.
Anyone want cast copper turgo spoons?  ::)

The application I'm building this for is:
280 gallons per minute at 47 psi, at least 4 jets required for a 6 inch diameter wheel at 1200 rpm.
I'm intending to convert a 480 volt 10 hp induction motor into a 240vac 40 hz synchronous motor, direct drive from the spoon, rectify it to dc, run the 330 volts DC the 1000+ feet and drive a VFD.. hopefully it can handle that.
My previous experiments with induction motors suggested half the nameplate volts per hz is the saturation point.
A shunt regulator or two of them for redundancy will keep the voltage down and the turbine loaded.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

keithturtle

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Re: diy cast Turgo spoons
« Reply #1 on: October 04, 2013, 03:50:47 AM »
Gotta love your determination.   Will you TIG or heliarc those spoons to the hub, or bolt them?   Balancing the assembly?

Not sure why you wouldn't run the distance in AC then rectify close to point of use.  VFD's don't put out real clean sine-wave power.  Possibly a large-capacity UPS with pure sine wave output?

Turtle
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joestue

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Re: diy cast Turgo spoons
« Reply #2 on: October 08, 2013, 04:40:12 AM »
If I cast them in brass I would very likely braze them to a brass plate. i don't have enough brass on hand to do that however. (err.. i do, but its in the form of 2 inch brass pipe... too precious to melt down, not enough buyers to sell on ebay.. too illegal to make distillation equipment from them  ;D  :P

If cast in aluminum-copper-nickel alloy as i intend to do, then i will have to bolt them, or perhaps rivet them to the runner.
at only 1200 rpm you wouldn't even need to balance it for direct drive, but its easy enough to balance such things on a knife edge.

regarding going the distance
http://www.youtube.com/watch?v=0pSlu2okpqM

Its less copper loss to transmit in dc at 330 vdc than ac at 240vac. the client doesn't have any big loads except for a saw mill that requires 10hp minimum. if i were in his position i'd make damn sure i could run my saw mill after the grid goes down for good.. and a 340 vdc battery bank and a 20 hp VFD is the easiest way to do that..

but there is no 24/48 volt battery bank to charge, so there's no point in doing anything less than 330-350 vdc or 240/120vac.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

joestue

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Re: diy cast Turgo spoons
« Reply #3 on: October 08, 2013, 05:03:55 AM »
as far as running household loads off a VFD.. 8Khz pwm doesn't take a lot of inductance and capacitance to nullify. 20 uF and 1mH should do it, very easily achieved with 6 of those useless aluminium microwave oven primary coils removed and used as air core inductors (two per phase in parallel, but closely coupled).. the 20uF caps only have to handle 2-3 amps of ripple current.. easy enough.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.