First core box

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Johnlanark
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Re: First core bockes

Post by Johnlanark » Thu Sep 27, 2012 8:03 am

Fabulous Rainer!
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Rainer
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Thank you

Post by Rainer » Thu Sep 27, 2012 2:24 pm

Thnk you for all the roses...

I am working in a 18 people company which is producing steady rests for workpieces from 10 Gramm up to 100 tons. All our steady rests are made from cast iron with piece weights from 100 kg to 2 tons. We don't 'rest' this pieces because the customer expect from us to deliver such a tailor made steady rest after signing the contract within 10 to 14 weeks - including full design, pattern making, pouring and machining :shock: -> but that's why they don't order in China...

This is me test running a 14 m long and 66 tons heavy workpiece at our new delivered steady rests at the customers work shop. Center height = 1250 mm. One steady rest is 2.5 tons heavy - made from 1 cast iron part.
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This is also a "normal" cast iron workpiece size for us - 1600 mm center height good for holding 30 tons turbine shafts
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One advantage of the cast iron pieces against a welded construction is that you don't have to anneal it for stress release - this saves time and money! Also meanwhile we know in which steps we have to machine our workpieces to get a high quality steady rest from it.

I think that's what I have to learn with my cylinder block too. So at first I will machine away only about half of the allowance at all "big" surfaces to get out all possible internal stress from pouring.
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fredrosse
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Re: First core bockes

Post by fredrosse » Thu Sep 27, 2012 4:03 pm

The best solution to stress relief of your iron castings, IMHO.

1. Machine surfaces very close to final dimensions.
2. Relax the casting with moderate cycles of heating and cooling, between ambient and about 160C-200C.
3. While heating/cooling of the castings, apply alternating stress loads of several thousand cycles.
4. This process can take from 100 to about 500 heating cycles, with each heating cycle having stress reversals of about 100,000 cycles.
5. At this time your castings will be well seasoned, and ready for final precision machining.

You may notice that this process will be much more pleasure to accomplish if you just build the engine and start using it in a dampfboot. After about 10 years you are ready to rebuild, and at that time the castings are all well seasoned! :D

All jokes aside, it is very nice to see your work progress, the best I have ever seen. Thanks again for sharing the process.
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PaddlewheelHub.jpg
Paddlewheel Hub, seasoned for 100 years, and machined with a well seasoned steady rest, considerably smaller than the Radow type
PaddlewheelHub.jpg (23.75 KiB) Viewed 7648 times
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gondolier88
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Re: First core bockes

Post by gondolier88 » Thu Sep 27, 2012 6:31 pm

Great to see the cylinders in the flesh.

A simple way to test how well the casting was cooled would be to file the flash on the casting- if it polishes, it has been cooled to quickly and will need heat treating. If it comes off as CI filings then it has likely been cooled down slowly and in a controlled manner.

In reality, for a casting of that size it shouldn't be too expensive to get it treated if you decided to go that route.

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Re: First core bockes

Post by Mike Rometer » Fri Sep 28, 2012 2:56 pm

I think distortion problems probably occur more easily with castings where there is effectively more "hole" than casting, i.e. where they have been deliberately kept lightweight, as in engine blocks, or long thin items. (lathe beds).
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Rainer
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Cylinder

Post by Rainer » Fri Sep 28, 2012 4:35 pm

Hello World

I am back from the foundry - without any part ...

In one cylinder a core was broken producing a "funny" steam port where it should not run. This can be fixed by a wire in the sand core - at the next pour.

The second cylinder was poured to hot. So the gas bubbles from the heated core sand produced some "sponge iron" which would let the steam from the receiver direct into the exhaust - not very efficient ;-)
Next time it should be poured a little cooler. Additional we defined some better de-gazing for the cores.

Hope all this will produce two fine cylinders next week.

This misfortune gave us the opportunity to test the strength of the construction by hammer. I was not able to crack the column mount - maybe the weak point - with a big hammer...

Next we will make a sectional model of this cylinders to reveal other problems - hopefully not!
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Re: First core bockes

Post by PatJ » Sat Sep 29, 2012 2:06 am

Rainer-

I was reminded of your posts here, and came over to take a look.

As usual, outstanding work.
Very impressive 3D and core/pattern work.

Any idea what your pour temperatures are?
I am pouring cast iron these days and trying to get a feel for it.

Pat J
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Rainer
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Re: First core bockes

Post by Rainer » Thu Oct 11, 2012 1:22 pm

PatJ wrote:Any idea what your pour temperatures are?
Hello Pat, sorry but I have forgotten to ask in the foundry yesterday...
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Rainer
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First pouring

Post by Rainer » Thu Oct 11, 2012 1:39 pm

Hello Boys (any girls here?),

now I can show you a "live cross section" view of my cylinder. The band saw cut goes right through the receiver which is located between the HP and LP side.

It is the cylinder with the "boiling core" defect because of a to high pouring temperature respectively because of a not so good degazing of the cores.

This pictures gives you the view to the LP side. Cylinder at the right. Valve at the left. The big chamber at the right is the integrated receiver. The flange at the left is the exhaust port. In the middle this is connected to the the exhaust room of the LP piston valve.

At the top you can easily identify the defect which connects the receiver with the exhaust and the LP top steam passage. The foundry men told me that it is not an unusual procedure to have some misfortune before you will know how to vent a complex part and what's the best temperature for pouring.
Image


This is the good side of the cylinder - you could make a single from it ;-))

HP Cylinder at the left, valve cylinder at the right. Big flange is the other half of the exhaust. The internal smal round part at the top left is a boss for the top cover screws. Hope to find them when drilling the holes...
Image

Same side of the cut - just to give you an other perspective. Here you can look into the exhaust room of the HP piston valve.
Image

The best news: At the foundry I did not take only this pictures - I also got two good cylinders :mrgreen: - will send some pictures later
Last edited by Rainer on Thu Oct 11, 2012 9:22 pm, edited 1 time in total.
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Rainer
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Good one

Post by Rainer » Thu Oct 11, 2012 7:24 pm

Here is one of the good ones!

Fresh out of the foundry. I told them "No cutoff grinding and no sanding please":
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Some 30 minutes later ready for painting ;)
The cores for the two drains at the right are 14 mm (0.55 inch) in diameter. The smallest core in this part builds the valverod guidance with a diameter of 12 mm (0.47 inch)
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I placed it direct at the sand plasted column support - no additional preparation.
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Before this piture was taken I milled away only about 0,7 mm (0.03 inch). The still unmachined surfaces at the left and the right are about 0,5 mm (0.02 inch) deeper. Please remember this part came out of a 4 parted mold - congratulation to the foundry!
Image

After that I turned the cylinder over and placed it with the fresh machined surface on the plane table. With the Faro Gage I found deviations from about 0,2 mm (0.008 inch) compared to the plane table at the non machined but sandblasted surface. No bending or other imperfections.
Image
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