Not to change your technique, but you might find this guy interesting. He is doing vacuum casting. using wax and plaster. He has a homemade vacuum chamber and pump. and while the pump kind isn’t as good as a vacuum pump, he doesn’t get that bad of results. And his series goes through the whole process.
Thanks Sean for the tips. I did try to coat the wax with wall board paste (not plaster), but the process takes days. Probably much faster with plaster. I know it goes against convention, but the fast cookout works and if I don’t over fire the mold, there are no cracks. I got the idea from this guy:
https://userblogs.ganoksin.com/fredsias/2009/02/08/fast-burnout-and-no-steam-dewaxer/
I think what happens is the plaster doesn’t have time to dry and block off escape routes for the steam. The steam creates “micro channels” in the soft plaster and comes out easily. I actually get a puddle of boiling water on top of the flasks for a couple of minutes after they come up to temperature with no evidence of cracking in the plaster. I love this method as I can pour a plaster mold and go on to pouring metal in about 20 minutes.
It was interesting seeing the video showing the molten metal being pulled into the mold using a vacuum. I had considered that method but I wasn’t sure if any seal could stand up to the temperature of the flask. (That was when I was over firing it and the flask was glowing orange). If I had to recast all the pieces again, I might go that route, but with just a few left, the lengthened sprue adds enough pressure to get the job done. 
marty, thanks for the detailled fotos and explanation!
what diameter of the feeding pipe you have on your pelton turbine?
how much height difference or pressure on the feeding pipe?
can you show us more pictures?
thanks giorgio
sorry for getting here late. There is a ceramic slurry that does not require a mixer to cast lost wax ceramic shells. I am familiar with the product suspend slurry from Ransom and Randolf. I used to do a lot of ceramic shell casting, but had a mixer, and you can get great surface quality. on the cheap, you can burn out mold with a weed burner. It is not too hard to use silicon bronze, which flows like water and is very weldable. I would be glad to help with any casting or furnace building help. Kent
Sorry Giorgio, I’ve got no pictures of the old turbine. However, I will be documenting the new one as I construct it. The first turbine was more of an experiment, but now I will make it permanent in a new location. I learned a lot from the first one. First, don’t use plastic spoons. 
Next, keep it as far away from your house as possible. Despite its small size, it is very noisy even at 50 meters away. The new location is further away in an alcove in the hill. I will also be constructing the small enclosure in concrete to further muffle the noise. An upside to this reconstruction will be a roughly 50% increase in the power output to approximately 500 watts.
As you can see in the photos, the turbine spoons are quite small. I will only use about 1 liter per second at about 100 psi (680 kPa). The penstock to the turbine is 63mm pipe and the nozzle is only 6mm. I chose this size because I can get a reliable flow of 1 lps through the late fall - winter - early spring. Often times it can exceed this by 5 or more times and I could install more nozzles or a spear valve to capture more energy, but I don’t want to have to be adjusting the valves on a daily basis. Maybe in the future I will install an automated spear valve, but for now I have to just get the turbine installed.
Now that I have all the spoons cast, the next step is to clean them up (remove flashing and defects) and drill out the mounting holes. Then I will weigh them and either grind all of them down to the same weight, or more likely just match them up in pairs to be on opposite sides of the runner with some minor weight adjustment…
I don’t know if you have seen this but it is a really sweet and clever self cleaning intake for the feed tube, it does require that you can lose a bit of head and waste a little space but I think you can probably afford that with that much head to have clean water without debris.
The showing of the self cleaning intake starts at 11,33.
I see that u-tube chose the pic with the intake for us
Edit: He also wastes a bit of water with this but I think most of it could be fixed with higher and curved blades to steer the water back but still use the momentum
Thanks for sending this, I had not seen it. It is a very interesting method of cleaning the water. My system employs a coanda filter which is also a self cleaning filter:
As debris builds up on the filter face, the water flowing from the top cannot make it through the slots and runs down over the debris, forcing it off the face of the filter.
Like in the video, the water flows from the filter into a 7000 liter holding/settling tank.
I found a picture of the old turbine.
Nothing here is going to be reused, except the penstock.
thank you for the fotos, marty, i am interested in this argument, because in winter we have some water what runs useless away in the winter creek ( in summer water here is very short and must be all used for the garden, a lot of month no rain here usually).
and this could maybee used for electric light in the house…
for one light bulb or two …10 to 20 watt each, from car equipment…
we have around 3 bar pressure here and water - in winter- comes thick how a 3/4 inch pipe…
maybee for a very small 12 volt generator in direct consume…battery less…open the well and light is here!
Hi Giorgio, it seems we have similar conditions. In the part of Chile I live, during the winter it rains almost every day, but in summer we may go a month without rain.
The generator in the photo is one I got from China. It is nice in the respect that it is a permanent magnet alternator (no parasitic losses from powering an armature magnetic field) and it has an electronic voltage regulator that puts out 12V. I do use a battery with it and an inverter to get 220V.
…
Have you measured the amount of flow? Maybe you’ve done the calculations already, but I would start there if not. You can start by measuring the flow out of the pipe and see if there is still excess water passing by in the stream. That will determine if you are flow limited by the stream or by the diameter of your pipe. You can then get a good idea of exactly how much power you can harvest. You might even decide to get a larger pipe for more power.
marty , thanks, be happy with only 1 month without rain, we have had some year where for 6 month was no drop of rain, this was in beginning of the `90…
3/4 pipe for some month , maybee 1 inch for short time, is what the spring gives, not more…there up is our water reserve for the house, and there is 1 pipe for use in the water system, and 1 pipe for the water overflow, this could be used…in winter often photovoltaik is not so much, so this use would be interesting…
i think for kitchen spoons for the turbine?, but wonder what my wife will say when she not can find any spoon more…? 
Do what I do, tell her it’s for a science experiment.
I usually get stuff that I am going to beat up from goodwill or similar. 
I personally like Francis turbines the most, which also works in the widest range with great efficiency, here is a link from the Slovenian manufacturer of turbines,…
It would be very interesting to use a variable turbine from a smaller car, for example from a fiat 1.3 jtd, this one has a narrowing made with a diameter of less than 20mm and a mini Francis turbine would be created…
I actually bought a 3D printer some 25 years ago made by BPM for making investment castings. I had 2 of them. Lost one in the fire. The other sits in a bedroom nearby. The surface finish and accuracy of the BPM process was impressive at the time and still is. Just a horribly problematic build product.
There are build processes that are better for burn/melt out than others.
Marty is learning about shrinkage in addition to other issues.
Personally - if investment casting quality was desired / needed for weight accuracy without resorting to spin casting, I’d have probably made a multi-part composite mold using polyester or epoxy resin and used it to cast a wax pattern with a decent sized sprue/riser to reduce shrinkage and increase fluid density during the casting process. Then simply cast the investment pattern into plaster. Then melt out and cast while the mold was still warm.
50 years ago I started with water bonded sand. Then petro bond and isocyanurate bonded sand. We also made our own sand for ni-hard castings using the flume sand from our aggregate processing. It had a fair amount of clay and a bit too much fine sand in it for porosity to aid in degassing but it worked. If I recall correctly we were using a silicone oil as a bonding additive which worked but as the supply dwindled we then tried motor oil…talk about smoking and stink - sheesh.
Todays printers are far beyond, where they were even two years ago. You can easily add in a scale percentage to the print pre G Code to compensate for any shrinkage.
Im getting a small army of Bambu Labs X Carbon printers for my other start up companies Im working on now.
Yes, mine is a spring type spinner. Due to the fact that the spinning mechanism is on bearings it takes some time for the apparatus to coast to a stop. It is intended that during this time that the casting at least begin solidifying. I had actually conceptualized building one using a wind up small engine starter like the lawn mower I first started using in the 1960’s had. Then dad ended up bringing in the new unit that we never used. I saw one at a local auction house last year. Sadly - both the seller and I knew that there was not likely going to be much interest in it.
The new machines and processes have a lot of capability. Price point is simply amazing compared to what they were 30 years ago. I know I need to say goodbye to the 3D Modeler I have. I keep wishing for an application for a fully self contained computer with a 5 axis stepper motor gantry but know it’s not likely that I’ll be the one to do anything with it. FYI - I paid more for it used than you can buy one of the Bambu Labs units for today.
I think the lady that was casting silver jewelry for her store was using the spring type spinner. I know one of my teachers was doing gold casting and that is what they were using but that was a Long time ago now. We studied it in metals class but because of the potential danger of flying hot metal, they removed it from the shop in like the 70s.
Yes, shop class today - if a school even has it - is nothing like the job preparation shop classes of the 1960’s and 70’s. Like I said - my dad had a cyanide salt bath in his program. He also had a metallurgical lab. My first aluminum casting was done at age 11 which would have been the spring of 1972. It is what is referred to as a flat back. It is the profile of an indian wearing a head dress. I still have it and other items I made. It had a defect in the feathers due to steam from the water bonded sand but I was able to hide it by using a file. Liability and lack of funding really killed off the shop programs. Some schools prevailed. Alas - the program my dad taught and donated $30K to when he retired no longer exists. The school gutted the program - starting with signing no-competition agreements with local factories who wanted to build their own training facilities. Then forcing my dad and other high trained instructors to retire. Then scrapping 156,000 lbs of tooling from dads shop. Replaced name brand vintage but good machines with new import machines which were junk in comparison (JET brand). Then failed to hire competent instructors and eventually closed the program without notice. Then sold off everything 3? or 4 years ago. I bought a few items from the on-line auction. I shouldn’t have done so. It was too emotional to see the shop gutted of it’s machinery - and knowing the lost opportunities it represented to future students. The welding shop instructor next door was hoping to have access to the extra space. The school had no plans for it.
They killed off shop class funding in the 70s or 80s at the federal level. I want to say it was under Reagan, but it might have been Carter. Liability was a huge issue. Our school continued for a while and even the community education had classes. but eventually funding dried up. They tried to reimplement parts of it like they have a plasma cnc machine and robotics, but the mechanics, welding, etc are all over at the ISD at the “career center”.
I think it was in 7th grarde we did 1/3 of the year in woodshop, 1/3 doing metals and 1/3 doing graphic arts (like silk screening and paste ups using a light table, which is really irrelevant today.) That program is gone too.
The irony is, unless you have been exposed to say welding for say a semester, how do you know you want to become a welder?
