Turbine

Whatisit?
Think of this as a virtual notepad. We can post up ideas, questions, photos and so on while trying to develop turbines in various designs, scales and associated equipment with the idea of using resin casting, 3d printing and anything else that comes to mind to produce these models for eventual sale.

Sketchup-osity
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Musings with coffee
Gate Shaft Casting

Gate Shaft Casting

Sitting here with my morning coffee while cleaning up the current mesh a bit. One of the things that becomes more and more important with a Sketchup construct as it becomes – more and more complicated is to divide it up into sections. This allow you to modify/affect one section with affecting the others. A Sketchup mesh can be pushed and pulled much like warm taffy .. pulling on one bit stretches the part you are pulling on and everything that is attached to. While this might be exactly what you want – often it is not. An example is the bit in the distance in the pic here .. the shaft support. I made the hole for the gate control approximately 1/2″ dia as that seems to me to be a logical size for the mechanism. If it is determined that it needs to be .. 3/4″ dia then it would be much easier to modify the gate control for that new dimension before adding back to the entire gate.

Doing something like that .. enlarging the shaft hole from 1/2″ to 3/4″ becomes more involved since you have to always keep in mind that the end purpose of this is to create a 3D mesh that can be uploaded for printing. Since I am designing for FUD I have to keep in mind then the design guidelines for that material.

I said ‘approximately’ 1/2″ dia shaft. In 1:48 1/2″ equals 0.0104~” .. more or less .01″. That is 0.264~mm. I made the hole 0.254mm dia. Am I crazy? lazy? .. nope. If and when I have this printed I will want to use a nominal wire size. I have some 0.010″ music wire .. which is .. .254mm .. that’s the sort of thing you have to keep thinking about.

So. Look at the pic. The shaft hole is 0.254mm. The surrounding boss is 0.8mm and everything sits inside the casting that measures 0.853mm tall. Do a little math and the wall thickness is 0.273mm .. OOPS. That is already a ‘fail’ most likely. The FUD design guidelines specify a minimum wall thickness of 0.3mm .. meaning that this needs to be fixed. It *might* slide by the automated software checks .. but things like this are a lot simplier if I just make the walls thicker now. The gate control is MUCH easier to modify as a separate mesh. Note that I need to increase the thickness of the walls by 0.027mm .. not much at all .. about 0.001″. Silly yes .. what does 0.001″ matter? Probably not much and possibly would slide through the automated checks. Probably though can get you in trouble (if you have a map for passage through a minefield .. that is *probably correct* .. you might regret following it .. for a bit)

If Russ informs me that .. a 3/4″ dia shaft would make more sense then more radical measures would be required. In 1:48 – 3/4″ equals 0.015~ .. or .. 0.397~mm. If I was going to use this dimension then I would use the 0.15″ dimension exactly (.381mm). That would calculate to 0.72″ dia .. ‘close nuff’. Adding the 0.3mm wall thickness would then give a boss measuring 0.981mm. That’s larger then the current height of the shaft casting shown (0.853mm) requiring the made larger also.

The point of all this is that .. I can modify this gate control as I need and when finished I can then ‘stick’ it back to the top of the rest of the model.

I put some dimensions of the bits and pieces

Centrifugal GateHere’s something else. Looking at the pieces of the gate separated into individual sections, I put dimensions of them. The minimum size of an object printed in FUD is 5x5x5mm. This is simply that a human has to pick them up and Shapeways considers this the smallest that their workers can reliably handle (find). Notice that the gate shaft casting at the far end only measures 4.667mm .. meaning that is too small to be a separate printing. That’s no problem here because (probably) it will be part of the center barrel-like object. Just pointing out that you have to keep in the back of your mind these things.

The reason the near vanes are while and the rest of the mesh is green was that I am cleaning it up. Going though bit by bit .. fixing holes in the mesh; removing un-needed lines and so on – and coloring it white as I finish each piece. This makes it easier to keep track of where I am. Color has noting to do with printing in FUD .. this is simply a visual help while designing.

Cylindrical Gate Turbine
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General Dimensions

Proportional Dimensioning

Using the photograph of the Type B Cylindrical Gate Turbine I will develop some general dimensions. I imagine that if I had photos of ten different models I would come up with ten different variations .. so .. I will be quite happy with these. I’m not using a set of engineering drawings so that the design is an exact copy – but a generic model with the feel of the beast.

  • (a) Since it is easy to see in photographs I used the Cylindrical Gate as a base for the dimensioning, setting it to 1
  • (b) Flange diameter
  • (c) Flange thickness
  • (d) Cage length
  • (e) Body length
  • (f) Second flange thickness
  • (g) Body diameter
  • (h) Gear diameter
  • (i) Shaft diameter
prop_dimWith the dimensions above I can start modeling in Sketchup. Just to show how I’m going about it – I set that dia of the Cylindrical Gate of 1 .. to 1ft in my Sketchup model. I then quickly create the other shapes based on the proportional dimensions I estimated. Once I need to get an exact measurement I can simply scale to what I need. For example .. in the next bit on scaling the turbine to the cylindrical gate I figure that the turbine is 3/4 that of the gate. Since the gate is about 1/2 the dia of the casing – and my design is for a 4ft casing that means that (currently) 1ft gate diameter simply needs to be scaled to 2ft .. and everything will scale appropriately.
Proportional Diameter

Proportional Diameters

Taking a look at this Cylindrical Gate Turbine we can get a general idea of the dimensions. A RED Elipse outlines the end of he Gate. From the center a GREEN line is drawn to the casing. This gives us a general dimensioning shown – The Gate/Turbine occupies approximately 1/2 the dia with 1/4 dia on either side. Think that’s ‘good nuff’ for me.

More – Proportional Diameter

Gate and Turbine Proportional Diameters

Once again I drew a Elipse around the circumference of the Cylindrical Gate. I then drew GREEN Elipse around the circumference of the white bit .. that would be the gate assembly according to Russ. The turbine wheel/runner would be inside that. From that I get that the white part of the gate has a diameter 3/4 of the outside diameter of the Cylindrical Gate assembly.

Using the 4ft dia casing I have currently designed that means the Cylindrical Gate assembly would be about 2ft in dia, the white inner part about 18in dia. Knocking off an inch off the dia and let’s make a WAG that the turbine wheel/runner would be 16in dia.

In-Progress Shots
Centrifugal Gate

Centrifugal Gate

The Centrifugal Gate. You have to remember here that this is quite small (this is about 1/2″ across). I am limited by the minimum wall size for FUD which is .3mm .. which means airfoil shaped blades are out. Remember this is a model .. it only has to LOOK correct .. not actually work!

I am thinking that I will put a ring around the top and bottom and leave a hole in the bottom. That way the turbine wheel can slide up inside easily.

Runner

Runner

Working on the runner, removing the ‘bits’ not needed. Here .. the tops of the vanes that extend into the support

Wicket Gate
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Wicket Gate
I finally got a good cross-sectional view of how the Wicket gate and Turbine blades all fit together. Now I have to ask .. when a book is referring to a turbine ‘wheel’ .. as in a chart showing estimated power based on water flow, head .. and WHEEL DIA. .. what is this referring to? The dia of the turbine/blade structure? I’m guess that is true .. then I need to figure out how much ‘add on’ is then represented by the gate (Wicket gate in this case). What I’m saying is that .. my ‘guesstamate’ from photos is that the gate you see inside the turbine housing is approximately 1/3 the dia of that casing. If the ‘wheel dia’ is the outside dia of the blades on the shaft .. then what is the estimate of the Wicket gate to that dia? That affects the design of the casing.