Member postings for Tim Taylor 2

Let me take a swing at it..

1.Create a new plane parallel and tangent to the tapered cylinder surface using the 3 point method.
2.Create a horizontal axis through the new plane using a reference point at the center of where the hole will be and one other reference point on the plane at the same height - this is the axis the new plane will pivot about
3.Create a second plane using the plane/axis option - select the plane created in step 1 and the axis in step 2, then select the angle of the new plane. It will display graphically...get it where you want it and hit "apply".
4. Select the plane from step 3 and enter 2D sketch mode
5. Use the circle function to create a sketch on this plane centered where the hole will be.
6. Use the extrude cut function with dual depth option to create the hole.

There may be a faster way using constraints - I haven't played with them much....maybe David or Jason would have an easier approach.....

Tim

Just a word of caution, this particular valve is designed & rated for compressed air service only by the manufacturer (Kingston). Their catalog doesn't specify a temperature rating, but this model has a soft silicone seat - not sure how well that would stand up.

They do make similar models that are also rated for steam, but the smallest has a 1/4" connection.

Blowdown valves have a couple of purposes. A bottom blowdown valve as Brian describes, allows you to blow out any crud that may have settled near the bottom of the lower drum or water legs..

A top blowdown valve is typically located below the minumum water level and is used to control the buildup of dissolved solids such as calcium and other ions left behind when the water is evaporated. If this isn't done, over time the concentration will build up to the point scaling can occur. On model engine boilers i doubt if this would be much of an issue. If the boiler isn't run continuously for long periods of time and flushed when you're done, you shouldn't have much of a problem.

Tim

John,

You are correct, it can be done using a combination of the sweep boss and sweep cut functions. One caveat is that Atom3D is a somewhat stripped down version of what was shown in the video, and doesn't include all of the full package's functions.

Tim

You can do some really neat things with the helical functions once you figure out how they work. This a coil of 0.125"OD x 0.063"ID tubing centered on a 0.5" radius....

Mick,

I find the helix cut function done as Jason described above is easier and looks better.

You can do it with the helical boss function, but it is more cumbersome. What you have to do is to first create the object to be threaded with the section to be threaded stepped down to the root diameter.Next you create the thread profile that will be added, and place it at the starting location of the thread. Open the helical boss function, select the axis, height and pitch - I find it easier to use the height/rotation option, but use what you feel most comfortable with. Hit "OK" and the thread profile will be extruded - problem is it doesn't have a clean beginning and end, so you need to do an additional revolve and extrude cut to clean it up.

I created a sketch of a 60 deg thread profile by creating a triangle with all sides constrained to equal length and saved it as a separate part. I open that sketch and copy the triangle, then paste stamp it where needed on the part where the thread is being created - use edit to scale it as needed.

Hope this helps....

Tim

Yep, that would work as well..........need to set the chamfer equal to or greater than the depth of cut, correct?

A neat little trick I figured out for adding "real threads" to a part using the helical cut function, that gives a nice tapered entry (and exit for internal threads).

Create the sketch profile to be cut at least one thread width above the part, then exit sketch mode
Select the sketch and the helical cut function
Click on the face to be cut (if an internal face, position part as needed to make it visible)
Set the length to be cut to the desired cut depth plus the offset
Set the pitch to a value slightly greater than the cut width.(for example, if you use a 0.050 diameter circle for the cut sketch, set the pitch to 0.060)
Select apply.

David - is there another way to do this using the advanced tab?

Thanks!

Much depends on your climate.

In humid climates where condensation is an issue, just a little heat works wonders - every 3degC you raise the air temperature doubles the amount of moisture it will hold, thus Clogs 11 watt bulb is a good idea. Isolating the machine and keeping the air inside the barrier a few degrees warmer than that outside works wonders.

We get quite a bit of rain here. My machines are in attached garage which though not directly heated, stays above outside temp., and in the 30+ tears we've been here I have never had a condensation issue. For preventive purposes I periodically coat all unpainted surfaces with a light film of way oil, or I use a product called Boeshield T-9 - not sure if it is available in the UK. Other moisture displacing compounds like WD40 also work pretty well.....

Tim

TG,

The Coppus TF design dates back to the 1920's. 15 psig is on the low side of inlet pressure - depending on materials of construction they could operate up to 650psig/750F steam with back pressures up to 150psig, and could produce up to 1000bhp. They also had a vertical version of the design...

In the 1970's the TF design was superseded by the RLA design, which changed from a flyball governor to a woodward oil relay governor and a new safety trip design. In the 1980's a horizontally split design called the RLH was introduced. Coppus is now part of Dresser. The following link is to a brochure describing the various designs - you might find it of interest.

http://www.mercado-ideal.com/catalogosd/DRESSER-RAND%20COPPUS%20STEAM%20TURBINES.pdf

The one I am going to model is actually similar to one of the horizontally split designs - both have similar wheels.

Tim

I remember those days - took my first mechanical drafting class back in 1966, and I still have a complete K&E drafting set, complete with nibs for india ink, that was my fathers before he gave it to me on my graduation from high school in 1969.

And I agree, there's no need for fully modeled threads except in very special circumstances - a simple note with a call out is all that is really necessary.

Tim

Also the helix extrude and cut functions can be a little tricky and are less than intuitive - essentially, you need to create a scaled sketch of the profile to be extruded or cut, located where the extrude or cut will be -- then with it selected, select the plane, height and pitch, then apply. There are a couple youtube videos out there that show the basics.

You might want to create a dummy part or two and play with it until you are familiar with how it works. Once you get the hang of it, it's not all that difficult.

If you don't need to show a real thread, you can use the "note" function on your 2D drawing to show specifics, as threads and hole call outs are not currently supported in Atom3D.

Tim

What David said.....

rotate part so back face is visible
click on the face then open 2D sketch
draw your sketch & close sketch mode
use extrude cut to depth

Welcome Tom!

I'm another newbie, also from North America (Oregon) - where are you located?

Tim

A "mil" is indeed = 0.001".

It is still commonly used in some areas such as machinery alignment where you will see offset expressed as mils and angularity as mils/inch.

Tim

That's one on the things I really like about A3D. You can make an edit in the 2D drawing or on an individual part while working in the assembly mode, and when you save it, all the original part files get updated as well - no need to go back and do them individually.

Tim

TG,

The way full size single stage Curtis turbines are made, the blade size is related to the wheel diameter and pretty much fixed. Instead of changing the blade size, they adjust the number and throat diameter of the nozzles to fit the application. As I'm sure you are aware, all full size turbines are sized for at least 10% reserve above rated capacity based on worst case (minimum inlet/maximum back pressure) specified steam conditions, and if dealing with a spec like API, you get an additional 10% on top of that. This is why the hand valves - isolating single or groups of nozzles allows you to adjust for optimum efficiency in actual operation - not really that relevant for a model turbine though......

If I have enough room, I'll probably use a nozzle block instead of machining the nozzles directly in the steam chest. What I am working on right now is how small I can make the buckets while maintaining a reasonably accurate profile. I plan on using a built up wheel - the buckets will be individually made and silver-soldered into slots in the wheel, then a shroud silver-soldered around the outside. Then the wheel will be chucked in the lathe and faced and turned to uniform OD.....at least that's my preliminary plan....

Now that the holidays are over, maybe I'll get some more time to work on it......then again, winter Steelhead season is just getting into swing here, so I'll likely be spending a day or two here and there on one of the local rivers with my fly rod.....

Tim

It was easier than I thought!

This pic is a cutaway of an actual Curtis type single stage turbine - this one happens to be a Coppus TF-9.. You can see the 2 row wheel, the reversing sector, and the cutaway nozzle. The hand valves on top are used to isolate one or more nozzles. Reducing the number of active nozzles to the minimum needed to maintain load insure that the pressure drop is happening across the nozzles, where is designed to, and not the governor valve.

Tim

TG,

I intend it to be able to run on either compressed air or D&S steam - not to exceed 50 psig inlet.

In a Curtis type Turbine, pressure is converted to velocity in the nozzles and remains relatively constant going through the rotor blades. The cross section of a nozzle looks somewhat like a venturi sliced on an angle - it tapers from the throat diameter to about 75% of the blade width at the discharge point. This is where the velocity angles come into play........the velocity angles of the nozzle and buckets need to line up correctly to get the best performance.

I'll try to post some diagrams when I figure out how to include them........

Tim

TG,

You understood it correctly - the design I'm working on is a Curtis type velocity-compounded style turbine, single wheel, with two rows of buckets and a stationary reversing sector between them. As you stated, the additional pass lets the machine develop more power at a slower run speed.

The trick is going to be how small I can make the buckets while maintaining reasonably accurate profile and velocity angles. It will probably mean going with fewer buckets on the wheel - I'm not overly concerned with efficiency, but I would like it to look as much as possible like the real thing.

I might start off with a single row wheel, as I can design the casing to accommodate either. That would be simpler and quicker.........hmmmmm, even with fewer blades, it might be interesting to compare efficiency of a single row to two row wheel.....have to think about that.

Tim