Topic: SR&CL Foundry story

[tomc]

Hi again,  Mel didn't like the looks of our queen post castings that we made so he made a new pattern and while at it, re-did the center castings to center the raised pivot on the base and raise the height about an 1/8 inch on both parts as he thought the car sat to low.  He also made patterns for the shoe that goes under the bolster.  So we fired up the furnance and made some molds and did a pour.  Our out come.

Tom C.

[rooster77777]

Hi
   This Christmas I am lining my steel hut with plywood on the inside at one end I am fed up of freezing. No decent work can be done under these conditions. I decided to give myself a Christmas present. Anyway I have started so I have to finish before doing anything else.
You should be able to biuld a thermocouple pyrometer and use the tables to calibrate it. I know that if you just use a low resistance meter to measure the current then the resistance of the leads will have an effect which will change with temperature. Last time I considered this was when I experimented with a low resistance meter I only got 1/10 scale with a gas flame(these meters are difficult to find). Now I see the chopper (non drifting) op-amps have come down in price. You could use one with x500 and an off-set and use the tables after setting two points.
I use my shop vac for sucking out welding fumes these foriegn rod smell like dead fish. Have a good holiday.       

[tomc]

I have seen where some of the melters use a vacumn cleaner with the hose pluged into the blow port with an opening they can throttle to match the air flow they need.
Something to try as everyone has a shop Vac!

Tom C.

[Arminius]

Brass is actually quite difficult to cast because of the fact that the zinc in the alloy evaporates and burns quite easily.

A better alloy to cast at home would be tin bronze ie. the classic bronze.  Although tin has a low melting point of about 450 deg F., it is quite stable in liquid form to very high temperatures.

I experimented with pure copper and pure tin in order to calibrate a home-made thermocouple meter and I was astounded at the behaviour of molten tin at high temperatures.

As to a centrifugal blower...  One could fabricate a largish one from 7074 heat treated aluminum alloy sheet by riveting, bolting, or staking.  Unfortunately this particular alloy, while very strong, does not allow itself to be welded successfully.

Using this method one could design a blower to make use of a given power source as to speed and torque available.

Arminius

[rooster77777]

Thanks Arminus
                     You seem to know your casting!! Yer I would have had a go at brass, but the only thing I would need it for would be bearing sleeves and I allready have an available source of brass tube.

I have been making a big blower not for smelting but for experiments to see how the temp rises with air compression. Car turbo,s give at least I bar but they rev up to 50000. My compressor wheel is only plastic, out of a hover mower driven by a washing machine motor which I also use to drive my lathe. The triac controllers are available at my uk calenterprises website.

There is a manufacturer of turbo impellers who reckons the best way is to make them from a solid bar by 5 azis machining. Casting produces too many defects. I would be lucky to get 1000rpm out of my plastic impeller but if I could cast one.

Dream on.          

[Arminius]

Keith,

Methinks that the first alloy you mentioned is in all likelihood ZAMAK, a very strong alloy of Zinc, Aluminum, and small percentages of perhaps copper and or iron.  And as you found it machines very nicely indeed.  This material was used extensively at one time for automotive trim such as exterior mirrors, radiator grilles, carburators, door handles, etc.  Probably cheap to get at scrap yards and castings are good for pulleys/ sheaves, bearing bases, etc.  It is not very heat resistant nor wear resistant as owners of the small Atlas lathes know:  The change gears were made of this alloy.  They did last a reasonable time with light usage.

With aluminum castings I expect you would have better results if you use as your source those items that were originally sand cast, items such as automotive cylinder heads, pistons, differential housings, and some transmission cases.  Since the alloys for these items were formulated for the gravity casting process (as opposed to pressure die castings or extrusions), using them in that fashion would produce more similar, but not identical, results. 

When casting aluminum the absorption of gasses and moisture from the atmosphere must be minimized to produce sound castings with a minimum of porosity.  If you can lay your hands on a book entitled The Metalcaster's Handbook, this tome has many tips and guidelines for sucessful casting.

Arminius

[rooster77777]

Hi folks
           I did some casting of what I thought was aluminium in the Summer. Not proper casting just in a tin can. I had various sizes of tin can to make some stock bar for turning on the lathe. I used bits of broken up motor casings and washing machine bits these must have been pot metal with zinc and it machined up really well. In contrast to aluminium, I melted later, which binds to the lathe tool and you have to use oil.
                      I did think that maybe white metal would make good bearings.  

Cheers Keith

[russ]

Fascinating ... have never really been exposed to any amateur foundry work since Jimmy Small demonstrated making aluminum casting inside a University lecture hall at a Toronto Society of Model Engineers meeting.  He cast something that was several pounds in size.  It was a scene out of Dante's Inferno with big propane burners melting the aluminum at the start of our 4 hour meeting and then at the end of the meeting out came the casting.  He started doing these castigns as he was building a self propelled riding snowblower for his long long driveway.  We thought for sure that he woudl set off the sprinkler system but he didn't.  This was 30 years ago.

Russ 

[tomc]

Well, we had more sucess with our parts coming out.  Here is the brake head that Mel designed to work with our shoes and our journal box cover. 

We also rearranged the foundry area to put the furnace out in the middle of our area.  We usually had it outdoors but with all the rain we couldn't lately. Casting must proced rain or shine.  We prefer shine.

Tom C.

[tomc]

Hello all,  we were at it again this last weekend and made more cores.  I found they would warp if left on a curved surface after being hardened.  BUMMER!!!   That didn't stop us from using them.  We used the kettle to soak the cores out.  A nice score for two days.

Tom C.

[tomc]

Ferd,  Aluminum for now.  Maybe brass some day.  I doubt iron ever.

Tom C.

[Ferd]

Hi Tom
Those look great.  Do you guys plan on casting wheels or are you primarily sticking to aluminum?

[tomc]

the results using cores the first time:

Tom C.

[tomc]

Ferd,
Yes they were and it gave us the impedess to move on to castings with cores.  We need Pedestals and Journal boxes.  Mel made some patterns and cores.  I mixed up the sand and away we went.  The patterns.

Tom C.

[Ferd]

Hi Tom
Looks like the castings were a success.

cheers Ferd