The International Hobby Metal Casting ezine.
Brought To You By:
Col Croucher, administrator of: www.myhomefoundry.com
Australia.
April 2007. Volume: 04. Number: 42.
I hope you had a nice Easter wherever you live around this great globe, unfortunately for some people here in OZ they never got to see the end of the holidays, as they lost their lives in tragic road accidents, a terrible waste of good lives. I hope your family is safe and well at this time.
We've had a very busy month, in fact the last three-four weeks just seem to be a bit of haze, but now I can see through the fog and things are settling down a bit more. Are your projects proceeding at the pace for you? I hope they are, as there's nothing worse than being bogged down with something and you don't know what to do or where to turn next, answer's to problems can be found by talking to others, conducting research on the net, reading books, and simply by experimenting with your own ideas and equipment, make notes on everything you do and compare results of the different trials, pretty soon you're sure to find the answer.
There would not be a week go by without recieving a request from someone to obtain our ebooks but they don't have a credit card, unfortunately purchasing and downloading ebooks on the net is all about convenience and speed, and a credit card provides that instant convenience, but we also understand that there are many who simply don't want to own a credit card for what ever reason, luckily there are other alternatives, such as; Western Union money transfer service which provides instant transfer to anywhere in the world, and it is very simple to use, yes you get slugged a fee, but most credit cards have an annual fee attached as part of the privilege, so if you only transfer money occasionally through western union, it is not much different to having a credit card.
The only other way is International bank cheque (check) transfer sent via traditional snail mail. But even pay pal offer an e-check service, i.e. you connect your pay pal account to your normal bank account and pay for your online purchases using the e-check method. It's costs Zilch to set up an account with pay pal. And we understand that you may not be willing to do that because of online security fears, but if you are careful and you have proper firewall security and virus scan programs with automatic updates installed on your computer then their is little to worry about. Pay Pal is now owned by Ebay and the service is far superior than what it was even a year or so ago.
A big thank you to the many people who take the time to email us with words of encouragement and appreciation of the hobby foundry material we have put together, we have also been working on some new material but other projects seem to be getting in the way, hopefully we will find the time soon to complete the work and be able to release them sooner rather than later.
If you have a hobby foundry success story or project you would like to share with other subscribers then please feel free to contact us, we would like to hear from you, and don't worry if you think you cant write, we'll give you a hand to put it all together... so come on, what about it, send an email to us and tell us about your success.
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Clean Sand +
Silicate + Catalyst = Great Sand Moulds & Cores.
The
simple equipment for silicate sand moulding.
Core box and resultant sand core.
ers and bronze tappets.
Result from
using silicate sand
core shown in photograph above, this metal section has been cut out of
a timing chest casting to show the wall thickness and metal form.
An
Interview With Rob White: By Paul Haney.
Inside Racing
Technology.
Below is an extract of an interview with Rob White, a
senior design Engineer at Cosworth, there is some very interesting
things pointed out to the reasons why the F1 designers/ constructors
put so much effort into getting the absolute maximum benefits from
everything they build. If you want to read the interview in its'
entiertey then there is a link at the end of the article which will
take you to the insideracingtechnology web site. It is about an hours
reading, but it is worthwhile.
Interview with Rob
White.
"All engineers are interested in materials, and we as much as anyone
else. Fortunately,
most of the things you have here are either specifically banned or
their use is limited in
the rules for Indy cars. I guess it's still worth saying that, in
modern race engines, the
most important materials are still high-strength alloy steels and
world-class aluminum
castings. There are other materials in there and you try to optimize
the materials you
use with heat treatments and surface treatments, but the real building
blocks of the
engines are still relatively traditional materials."
PH: "I've read that Cosworth has a casting process that's better in
some way?"
[Since sold to Ford.]
RW: "That's true. I'm not sure of the history, but maybe 15 years ago
or so we decided
that we should have our own foundry because of the difficulties you
have in getting
aluminum castings of good dimensional accuracy and good structural
integrity. Bottom line now is we have our own foundry with our own
unique process that achieves this by a quite novel means.
"The basic difference is that instead of taking molten aluminum from a
vat and ladling
it into molds, the stuff is pumped out of the vat so you don't have a
ladle passing through the scum on the top of the vat or disturbing the
stuff on the bottom.
You take pure, clean, molten aluminum from the center of the
vat and pump it through
ceramic pipe with a type of pump that has no moving parts. It's an
electro-magnetic
device of the type used in nuclear power stations to pump liquid sodium.
"You haul this clean molten aluminum out of the middle of the vat, and
you pump it into the mold from underneath. So the mold gets to vent at
the top, and you don't have the gas bubbles passing up through the
whole melt. It has a clear passage to the outside world. The other
thing that's important is that if you maintain a modest pressure on the
bottom of the mold until it's solidified, a number of things contribute
to the improved integrity of the casting. First is the cleanliness of
the material.
Second, there is less porosity because there's a good route
for the air to get out of the mold, and the pressure helps too. There's
another important difference in the process, and that is the sand used
in the mold is not the same stuff that's used in a typical molding
application, which is usually silicon sand.
We use zircon sand. The key feature of zircon sand is that it
doesn't have a phase shift close to the temperature where aluminum
melts, whereas silica sand does have this phase shift. What happens
when silica sand undergoes this phase shift is there is a small volume
change which results in a dimensional change to the casting.
Fundamentally, the zircon sand gives you a casting which has better
dimensional control. The stuff is damned expensive, and the only way
you can do it is by recycling the sand. Another part of the process is
a novel way of reusing the zircon sand so it's viable. I'm not an
expert on the casting process and that's about all I can remember.
"Our basic materials are high-strength steels, good castings, and
optimizing surface treatments. We use nitriding on crankshafts,
tufftriding on cams and tappets, and plating or vapor deposition
processes on titanium pieces.
"Titanium is an interesting material because it's light and very
strong. Typically it has yield strengths as good as a reasonable piece
of steel. It has several important disadvantages compared to steel,
though. First of all, it has terrible properties when any sort of
sliding friction is involved. Anytime a titanium piece has to rub
against anything else it's bad news. This means that almost any
application you can think of for titanium involves a part that's
moving, because it's used so you can reduce the reciprocating mass of
something. So anywhere you use titanium there has to be a coating."
Article content courtesy: Paul Haney.
INSIDE RACING T E C H N O L O G
Y.
To read the full interview, visit the link below. It is a rather
lengthy,
but very interesting read.
http://insideracingtechnology.com/robwhiteinterview.htm
Have You Ever Wondered How Metal Powder Products Are Made.
The
Powder Metalurgy Process, consists of mixing elemental or alloy
powders, compacting the mixture in a die, and then sintering, or
heating, the resultant shapes in a controlled-atmosphere furnace to
bond the particles metallurgically. Learn More>> http://tinyurl.com/yqoezy
Making Metal Powder.
The first
step in the overall PM process
is making metal powders. There are four main processes used in powder
production: solid-state reduction, atomization, electrolysis, and
chemical.
Learn More about the process: http://tinyurl.com/2r7zka
The Silicate Sand Moulding Method.
Cold Box or Air Set Moulding System
Have you ever thought about making your foundry moulds and cores with something other than green sand? You could use clean, graded foundry sand mixed with a self set/air set silicate and a catalyst to create sand moulds. The system is not that hard to use once you get your head around the chemistry side of things. You wont ever have to worry about reconditioning/retempering sand with water, there is no mulling as you would with green sand, and the method produces excellent moulds and cores, which show a very high strength.
The middle picture above shows a core box and the resulting core made with this system, if you have a little experience with cores you would understand that a slender core like this is fragile and easy to break while being handled, and that was the case with the first few cores that were made, but once the silicate/catalyst mix in the sand was altered to increase the hardness, everything was ok. The core box was heavily waxed and rubbed with graphite to make a good release surface, but care was still required when splitting the core box to remove the core.
In case you are wondering, the core was used to create a waterway in an engine-timing chest being cast. If you take a look at the bottom picture you can see the small section that was cut from the timing chest casting, it shows the uniform wall thickness of the waterway, a tricky thing to achieve. So lets just go back to the top picture, which shows the simple tools and things you need to make moulds and cores using the silicate sand process.
The white container holds the clean foundry sand, the yellow bucket is used as the mixing bucket, you need a small container like an ice cream bucket to use when measuring/weighing the silicate binder, a set of kitchen digital scales are perfect for this purpose, so when the little lady is not looking you can borrow the kitchen scales for the foundry for awhile, but make sure you keep them clean and return them before she arrives home from the shopping... other wise you might be banished out with the dog.
To measure the amount of catalyst, all you need is a medicine measure, the amount of catalyst required is critical and must be spot on otherwise the system just wont work, and the moulds will be weak and may break easily.
We wont go into fine detail here because if you decide to try this system, you will be supplied with data sheets when you purchase the materials on how to get the best from them.
To mix the batch of sand with the silicate you use a small hand held power drill with a wire mixer fixed into the chuck, look closely at the tool leaning on the yellow bucket and tall white container in the top picture, that is the wire mixer. Once the sand/silicate is mixed which only takes less than a minute, you then add the catalyst and continue mixing for about another minute, then you quickly ram the mould or core box with the sand, the bench life of the sand mix is only about ten minutes on a warm day, so you need to work pretty quick to get the job done.
There is a downside with this system and that is of sand disposal, with green sand you can continue to use the same sand for many years, but this system is a one shot system, where you mix - mould - pour, then destroy the moulds to retrieve the castings, then you discard the broken sand moulds and waste sand. Large foundries do have sand reclaiming equipment, but for the hobby foundry user it is not really worthwhile.
The chemicals and materials can be acquired at any foundry supply house and they are sold under many different names, another draw back is that the smallest drum size sold is about twenty litres, or four gallons, and it is not cheap. One of the best ways to source materials to start experimenting is to get to know a small commercial foundry in your area and ask if you can purchase a small amount of clean dry foundry sand, silicate and catalyst to get you going, once you start to get the hang of it you may well give the green sand away for ever, but I doubt if you would because we all know just how convenient good old green sand is.
With experience in both green sand and silicate sand moulding you will be armed with knowledge and skills that you will be able to draw upon to produce the best possible casting results for your projects, and that is a beautifull thing.
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Before we go, a quick word about the contact form on the about page at our web site, in the past few weeks we have had a huge spam attack through our contact form, so we have removed it for the time being, if you wish to contact us just follow the directions we provide on the about page, we will have a new spam proof contact form up and running soon, sorry about this, it's a real pain in the ass for all.
I hope you have enjoyed reading this issue, good luck with your projects.
Until next month.
Col Croucher.