First core box

[DetroiTug]

A few additional points about propane. Propane is heavier than air and will settle in the bilge of a boat. To safely store it on a boat, it should be in an airtight locker vented to the outside of the hull. If a propane tank "pops off" inside of a boat with fire going, it's going to be an instant inferno, the fire will prevent the relief valve from re-seating.

On vaporizing burners, it was common practice at one time (30 -40 years ago) to use very convenient propane as a pilot fuel. There have been a three or four accidents that resulted in fire and in some cases people have been injured or have died. Most of the steam car tours now prohibit any propane usage.

While true propane is used as a motor fuel for all sorts of vehicles with a good safety record, the difference with steam powered applications is the perfect source of ignition (main burner) during an automatic or accidental release of LP.

I worked with Propane for a number of years back in the eighties. One important factor with handling it safely in all situations was the absence of source of ignition. Another is understanding of how it is affected by ambient temperature in regard to volume and pressure. It is most dangerous in the summer months, where pressures can exceed 200 psi . In the winter months due to it's decreased volume, more liquid can be inserted to the 80% level, that is why propane is sold by weight at the retail level and not liquid volume like other liquid fuels. It is sold in gallon volume at the residential and industrial level, as the person handling it understands it and the meters are compensated by temperature. Rail car transmissions are calculated with temperature correction formula. Most of the relief valves are set at 250. Some of the older tanks we had in the field were set at 225 (old butane tanks) and popped off occasionally in the heat of summer or during filling. The way we fixed this typically was to paint the tank white to reflect the sun's heat. If it popped off while filling, the driver reported then we waited until it was empty and went out and changed the relief valve.

Sometimes folks get lulled in to a false sense of security inadvertently releasing propane gas without incident. The conditions that prevent mishap is the improper fuel to air mixture or lack of source of ignition. If memory serves me correctly it's about 4% propane to air is perfect, when it's at that level, it's explosive. I've seen two houses destroyed by propane leaks(customer negligence on both), One it lifted the roof up and blew the walls out and the roof was in the basement, the other there was nothing left. Recalling that one there was an aluminum extension ladder in the top of a tree about 300 feet away. Both incidents no one was home nor any injuries reported.

I've rambled enough, but be careful.

-Ron

[Mike Rometer]

Propane power? Try this one for size.

http://www.nzherald.co.nz/rail/news/art ... d=11191235

Hope the link works!

[fredrosse]

Propane costs far more than Natural Gas, and its conveinence comes from being able to liquify it without needing super low temperatures.

The Natural Gas Locomotive article posted above: "Industry officials say the rising natural gas prices that helped scuttle their earlier experimentation with the fuel should not pose a problem this time because significant new sources of natural gas are now available.
Peter Roosen is CEO of VeRail, which is developing natural gas conversion kits for low-horsepower locomotives, such as those used in rail yards.
"I think we're going to have reasonably priced natural gas for decades," Roosen said, "if not for a generation or two."

Having worked in the power industry for over 40 years I have seen predictions such as this for years, optomistic statements by people or businesses that plan to profit from the switch. In 2000 you could not buy enough big gas turbines (natural gas fired) to satisfy the market. Two years later natural gas prices went way up, then you could buy big gas turbine power plants at $0.50 on the dollar, many natural gas fired plants closed down. Now the same cycle starts again, everyone is converting to natural gas, but in a few years the environmentalists will prove that fracking is dangerous, causes earthquakes, etc, and natural gas prices will shoot up again, then wholesale abandonment of natural gas burning for big power users. Then back to coal and or nuclear power.

[Rainer]

Hello Steam Friends

I am still rigging for the pattern making. As you have seen some pages before, I started a pattern mill project with a friend. Unfortunately he loaned me his for the cylinder patterns. So there was no need to build up my own.

But in the last weeks I started to complete my own pattern cnc mill. The Y-axis is running under the self made table already. Even with CAD design I like the "card board design validation" to get a good feeling of proportions and forth.

2013-12-23.225100.jpg (74.72 KiB) Viewed 8560 times

Distance will become 200 mm now

2013-12-20.142005-k.jpg (165.24 KiB) Viewed 8560 times

[PatJ]

Rainer-

Nice looking CNC machine.
I have seen several online that are building similar units.

I guess that is the future of pattern making.
It certainly simplifies making the more complex patterns.

I wonder if people will offer online CNC services as they do for 3D printed parts?

The CNC option seems to allow for a much larger pattern to be made.

Good luck with it, let us know how the software/hardware setup goes.

Pat J

[Rainer]

Nice looking CNC machine.I have seen several online that are building similar units.

Yes, this is a usual setup and nothing special. Maybe the German-Over-Engineered cast Aluminum base and the 200 mm z-travel with such a small machine makes it a little special. I don't want to bore you with this: I only wanted to show that I am still alive and still interested in steamboating )

I guess that is the future of pattern making. It certainly simplifies making the more complex patterns.

For me it's the only way because I never learned how to make wooden patterns. With this technique you give a little more computer power and invest into the scale pan to compensate the absence of skills and know how of long term pattern makers - but still - by buying a Microsoft Word program you don't win the literature Nobel price with a 100% guarantee.

Good luck with it, let us know how the software/hardware setup goes.

Here the actual status - I found some 100 x 100 x 10 mm angle profile in the laydown - makes it rigid...

2014-02-05.193824-k.jpg (131.14 KiB) Viewed 8509 times

[PatJ]

That base is a work of art and engineering.
The angle sides look very good too.

I am corresponding with a guy in Canada who is also building a large format CNC.
I can't find the specs on it right now, but I seem to recall is was 1200mm (length) x 600 mm (width) x 450 mm (height).

In my discussions with him, there is apparently much to be learned as far as finding efficient tool paths, bit sizes, cutting feeds and speeds, and optimizing things in general to minimize cutting time.

His unit is not going to use position feedback potentiometers, it will just cut blind, with the assumption that things will stay aligned correctly.

I have sent him a few 3D modeling files, and from a CNC standpoint, it seems to help to have as clean a 3D model as possible, else the CNC machine tends to overwork on too many minor irregularities in the model.

I would certainly like to compare notes between these two systems to see which one is more optimized.

I will ask him for more information. (Edit: I found a photo of his unit. Hope he does not mind if I post it here.)

From a 3D modeling standpoint, there has to be some consideration if CNC is going to be used as far as undercuts (is that the correct term?), ie: the CNC cutter is approaching the work vertically (for a 3-axis machine), and so it cannot cut beneath another part.
I suggested to him to break the more complex patterns into pieces to avoid undercuts, and then glue the respective pieces together to make the final pattern.

I have discovered "configurations" in Solidworks, and so my base configuration is the "as-machined" part generally with the final paint colors. My second configuration is the pattern or pattern half with core prints, machining allowances, shrinkage scaling, and a color scheme that reflects typical pattern colors. All of the holes for fasteners, keyways, bores, etc. are supressed in the second configuration. I generally have a third configuration that highlights all of the surfaces to be machined in red.

Making patterns in wood is a bit of an art, especially when you get into muti-part patterns with retractable and removable pieces.
I have set up a wood shop and am trying to learn pattern making.
Wood is forgiving though, and you can always glue on an extra piece and do a little more machining and sanding, if you make a mistake.

Pat J

[Rainer]

x 450 mm (height).

The height is what makes the system week or heavy. For my patterns I am using ball nose mills with 6 or 8 mm in diameter. This are available in a length of 100 mm. take 20 mm for clamping it so you have a maximum cutting depth of 80 mm. To lift this over the workpiece surface you need additional 80 mm z-travel = 160 mm z height. with some extra I went to 200 and think this is enough. If you allow bigger diameters you can use longer tools - but all this depends on your needs...

His unit is not going to use position feedback potentiometers, it will just cut blind, with the assumption that things will stay aligned correctly.

This is the normal stepper motor setup which is used in most of the hobby cnc mills. In my first build CNC mill (see some posts before) I am using a closed loop DC-Servo system (400 Watt per Motor) - called UHU - from a German cnc Forum. This is using an optical revolution indicators with a resolution of 400 ticks per mm milling travel so 4 ticks per 0.01 mm or 0.0004 inch. This Aluminum base pattern mill will use the ordinary open loop stepper system with 3 Nm stepper motors. The option is to use a closed loop stepper system. This is 270 € per axis ;-( So I will try the open system first.

I have sent him a few 3D modeling files, and from a CNC standpoint, it seems to help to have as clean a 3D model as possible, else the CNC machine tends to overwork on too many minor irregularities in the model.

Yes, it helps if the designer nows a little about the machining basics. I am designing my models with the 6 or 8 mm ball nose mill in mind...

From a 3D modeling standpoint, there has to be some consideration if CNC is going to be used as far as undercuts (is that the correct term?), ie: the CNC cutter is approaching the work vertically (for a 3-axis machine), and so it cannot cut beneath another part.

Ok, but with sand casting you have the same "problem" so if you can sand cast your model, you can 3-axis mill it. If you have undercuts in the sand you also have to split the sand form. I have done this with my cylinder - have a look here:

2012-01-16.071900-k.jpg (64.79 KiB) Viewed 8498 times

This also splits the model in parts not higher than 60 mm for good milling - see one of the first posts in this thread

I have discovered "configurations" in Solidworks, and so my base configuration is the "as-machined" part generally with the final paint colors. My second configuration is the pattern or pattern half with core prints, machining allowances, shrinkage scaling, and a color scheme that reflects typical pattern colors. All of the holes for fasteners, keyways, bores, etc. are supressed in the second configuration. I generally have a third configuration that highlights all of the surfaces to be machined in red.

Here there will be a million of possible work arounds! I always try to keep the basic CAD model as simpel as possible to let it modular/easy to change. Lifting bevel and round corners will be made only in a last "configuration" as you call it. I do the shrinking scaling while importing the file into the CAM program - this don't confuses me with to many "configurations" to keep.

[PatJ]

Rainer-

I re-read all your posts.
I have learned a lot about castings and engines in the last year, and have a better idea of what you are doing now.

Looks like outside admission for the HP and LP cylinders?

And I think you mentioned a fitting for introducing boiler pressure to the receiver for starting, if necessary.
One guy mentioned that his compound really does not have much trouble starting without the bypass (is that the right term for introducing boiler pressure to the LP cylinder?).

Watching with interest.

Pat J

[Mike Rometer]

PatJ. "And I think you mentioned a fitting for introducing boiler pressure to the receiver for starting, if necessary.
One guy mentioned that his compound really does not have much trouble starting without the bypass (is that the right term for introducing boiler pressure to the LP cylinder?)."

Certainly in the 'Traction Engine World' this is called a Simpling valve. (reverts the engine back from Compound to Simple)