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.

This entry was posted in Turbine Page by etraxx. Bookmark the permalink.

About etraxx

Retired from the Army in 2006. Served during Vietnam - 1969-1972 as as 72B - Communications Center Specialist (Teletype Operator). Got out .. and went back in 1987 as a 19K - Armor Vehicle Crewman - (M1/M1A1 tanker) getting out in Korea in 1999. Went into the Reserves .. got mobilized in 2001 .. stayed active until my retirement with 20 years in 2006.


Sketchup-osity — 9 Comments

  1. Well. After going on about the Gate Control shaft possibly being too small at 1/2″ .. I decided to ‘bump it up’ a little to ~3/4″ (actually .720″ .. that’s 0.15″ in O scale)

    While I was browsing the net I rendered the current state of the turbine. Next .. need to put in the gearing from this shaft to the one at right angle to it … maybe. I need to decide exactly where the shaft from the outside enters the casing.

  2. a bevel ring and pinion gear allows control of the gate from the outside. Depending on the direction that the pinion faces you could have the control shaft exit the end of the casing along-side the power-shaft (A) or out the side of the casing (B). If it’s out the side then the pinion would hit the face of the gate assembly and would have to be raised (C).

  3. I finally sat down and sketched out the power take-off from the turbine over to the power-room. It will be off-set by about 2″ .. some 8ft in ‘reality’. The original position of the gate control shaft support is shown in Green. With the way the power is taken to the power-room it makes more sense for the control-shaft to exit the end of the casing as in (A).

    To do that I will have to see where the shaft exits the end-cap .. to see if the cap needs major modification or not.

  4. At this point I need to stop and work on the gearing. The ones I used in the drawing above were just a quick-n-dirty set. For 3D printing there is a lot more needed .. I would *like* something more ‘Steampunkish’ .. and I also need to keep in mind the design limitations for the material I will have the thing printed in (FUD).

    I imported a photo of the Cylindrical Gate Turbine. I had earlier decided that the diameter of the section with the vanes was 24″. Reduced to 1:48 that is 12.7mm. Dimensioning that now in Sketchup allowed me to get dimensions on the gears and even the tooth angle on the pinion gear. These are OF COURSE just rough approximations but .. get’s me in the ballpark which for me is – “good nuff”.

    • A few more measurements and I am ready to proceed. Note: Yes .. I know that the numbers mean little. They DO though provide some basic proportions that I can use to good effect .. I believe. If wrong … sue me.

  5. Working on the gears. Trying to keep to the general size as proportionated off of the photo (I KNOW .. not a word but I LIKE it!). The problem has been trying to keep to the .3mm minimum wall and .1mm minimum detail. The teeth are .3mm wide and tape down to a .1mm face. That .. SHOULD .. work. Still need to draw the ‘cage’ on the back of the ring gear.

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