Author Topic: Made without castings ???  (Read 16959 times)

Offline metalmad

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Re: Made without castings ???
« Reply #30 on: October 31, 2012, 04:58:18 AM »
Hi Dave
The sand was just from the landscaping shop mixed 10 to one with cat litter
the cat litter was unused so not green at all  :Jester:
Pete
A little bit every day, sometimes the same little bit

Offline Artie

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Re: Made without castings ???
« Reply #31 on: October 31, 2012, 09:56:43 AM »
Love your thread mate, my love is in the actual casting and Id prefer to go to the effort to make the plugs/cores etc than fabricate (sometimes), different strokes for different folks.

One use Ive found is that I now have every size piece of bar stock I ever need, just need to do a casting. I often just make up strange sizes with excess melt, and put it into stock for whenever.... using a piece of timber pushed into the sand (open top) or made up ingot molds...

Good stuff mate, enjoy the journey... some brass bits...



became these...




Offline maury

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Re: Made without castings ???
« Reply #32 on: October 31, 2012, 12:52:54 PM »
Metalmad, that is a nice casting, looks like you are on the track for making a nice model. In your post you mentioned not being sure why the shrinkage appeared. First off, aluminum is a nutrously bad metal for shrinkage and porocity, to me, one of the more difficult metals to cast. A few hints.
1) to avoid the shrinkage, use a riser. You could put it on the vent side of the casting, and make it about as big in dia as the coke can, and about half as tall. The rule is the cross section of the riser should be about 1 1/2 times the largest cross section you are trying to prevent shrinkage in. Put it as close to the casting as possible. Metal freezes in the mold from the thinnest cross section to the thickest, so for the riser to work it needs to feed through a still melted section to the thick section of the casting. Put the vent in the drag, and make the cross section thick.

2) For aluminum especially, you need to reduce turbulence in the mold. Feed the casting from the sprue through a gate in the drag. Turbulence causes oxidation of the metal, and with aluminum, the slag is about the same density as the metal. So the slag will not float up, it will be included in the casting.

3 If you need vents ( your sand is dense) you may make a ice pick poker with 1/16 or 3/32 drill rod and use it to vent at the top most features in the cope.

Good luck
maury
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Offline DavidF

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Re: Made without castings ???
« Reply #33 on: October 31, 2012, 02:09:47 PM »
metalmad, looks like you got your greensand dialed in, I all ways had a habit of making mine too wet.  Here is a pick of what I mean about the feeder blocks and extended sprue and vent. This part was actually a fail because I put the cope on 180' out.

Offline DavidF

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Re: Made without castings ???
« Reply #34 on: October 31, 2012, 02:13:01 PM »
Artie, nice bits of brass you have going on there, cant wait to see the rest of it!!!

Offline zeeprogrammer

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Re: Made without castings ???
« Reply #35 on: November 01, 2012, 01:33:43 AM »
I don't think casting is in my future. But I sure enjoy reading about it. I'm impressed with the knowledge of material and process one has to have.

With respect to some comments about 'using casting for first engine'...I went down that route. I ended up buying 3 (or was it 4?) kits before I got a runner. At the time I knew more than I do now. By which I mean...I've learned how little I knew and how much more there is yet to learn. Also at the time...I didn't know about these forums, the kit was fairly inexpensive, and a video was available to take me through the steps. (Turned out the video was incomplete.)

Even kits that come with plain stock are iffy. They just save you the trouble of getting the odd bits of metal. Although some come with decent construction manuals that I found useful (and aggravating at times). But being a beginner I ended up buying more material anyway. Still...it was a help to know what I had to buy.

Now I'm building up some inventory and whenever I do buy some standard material, I'll get an odd bit of something 'just in case'.

So I'm on the side of using plain stock for a first engine.

Now some of you might be thinking...'uh...didn't you just get a dynamo  and boiler kit?'. Well yes. I'm still a beginner and for me...those kits fit into my way of learning. That is, when something is different or parts are hard to get or when a model is very new for me. I don't think my next engine will be from a kit. Might be from a casting set though  ;D
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Bogstandard

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Re: Made without castings ???
« Reply #36 on: November 01, 2012, 04:49:10 AM »
Zee,

Many kits and plansets grossly over engineer the engines.

So all those 'special' materials are just not needed in a lot of cases.

If you were building say a nine cylinder radial, or a highly stressed ic engine then yes, some exotic materials will need to be used for coping with the stresses involved. But on small scale models of air or steam engines, or even low power ic engines, then almost any materials could be used in their construction, as long as things like galling and expansion rates are taken into account.

Beginners tend to think that the correct materials shown on plansets and kits are definitely needed, but they are usually not, and they can spend great deals of time and money attempting to obtain what is shown on the plan, when in reality, a quick scrabble around in the scrap box can usually turn up something that will do the job admirably.

John

Offline zeeprogrammer

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Re: Made without castings ???
« Reply #37 on: November 01, 2012, 11:26:57 AM »
Beginners tend to think that the correct materials shown on plansets and kits are definitely needed, but they are usually not, and they can spend great deals of time and money attempting to obtain what is shown on the plan, when in reality, a quick scrabble around in the scrap box can usually turn up something that will do the job admirably.

Yes, that was true for me as I knew virtually nothing when I started this hobby. Materials have been (and still is) a part of my learning. When I started all I knew was 6061 aluminum was a popular metal. I didn't know anything about types of steel or brass (other than surely there were different types). The kits gave me a starting point (along with the Doug Briney's book - 'The Home Machinist's Handbook' which I found immensely helpful to me).

I would note also that as a beginner I hardly had a scrap box. A bit of metal from the projects I did in that book. The scrap box really began with the first kit  :Lol: With the first parts I screwed up and extra stock I had to obtain to replace them.  ;D

By 'special' I didn't really mean exotic. As a beginner I meant the 'odd' bit or the 'more difficult to find'. For instance some bolts, or brass or copper tubing (that is often difficult to obtain until you learn more about vendors or hobby shops - or even gather a few friends like this forum that can help). Or like that armature for the dynamo I want to build.

We forget what we didn't know. And you kind of fell into that trap when you mention 'as long as things like galling...are taken into account'. I didn't know that when I started...and I'll probably forget that I didn't know that some day too.  ;D
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Bogstandard

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Re: Made without castings ???
« Reply #38 on: November 01, 2012, 12:06:52 PM »
Sorry about that Zee, I realised afterwards that the word 'galling' might be a problem to some people, but usually a quickie visit to Google sorts things like that out.

You should get your neighbours and friends involved in your metal acquisition.

I have told everyone I know not to throw anything away that has metal in it, until I can have a look at it.
It might mean you get a yard full of junk, but at least, all you have to do is to strip the stuff down, and I will guarantee that you will get more raw material than you could ever buy for the cost of a trip down to the garbage dump to get rid of the leftovers.
I have even been given long lengths of large diameter brass and bronze bar that someone had stashed in the back of their garage for years. Most probably picked up from their fathers garage many years before, and they have never found a use for it.
I have more stock than ever I could use in my lifetime, and even the local model engineers come to me to raid my stash boxes in the hope that there is something in there that will help with their builds. And I have never had to pay for any of it, so I don't expect them to pay for it either.

John

Offline Bezalel

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Re: Made without castings ???
« Reply #39 on: November 01, 2012, 09:37:21 PM »
Snip>

You should get your neighbours and friends involved in your metal acquisition.

I have told everyone I know not to throw anything away that has metal in it, until I can have a look at it.
It might mean you get a yard full of junk, but at least, all you have to do is to strip the stuff down, and I will guarantee that you will get more raw material than you could ever buy for the cost of a trip down to the garbage dump to get rid of the leftovers.  Snip>

John

What John said  :Director:

When you have a furnace your trips to the dump are even less frequent.  For jobs that are more ornamental than structural, what its made of is more about final colour and melting temperature than it is about the chemical composition of the alloy.    :stir:
 
Bez
 
Queensland - wet one day, humid the next

Offline DavidF

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Re: Made without castings ???
« Reply #40 on: November 01, 2012, 10:34:19 PM »
I dont know how things are in other areas of the world, but around here metals are high dollar and its next to impossible to find non ferris scraps (cans not included) There are alot of scrappers running around that only see things as thier weight in metal and not thier antique or usefull value. I purchased a clausing lathe off the back of a scrappers truck for 200.00 for a friend of mine. it was a perfectly good lathe that was bound to be melted down into some junk crap. It scares me to think about all the good stuff that was just scrapped out for a few bucks worth of scrap metal. I cant find very much brass or bronze scraps any more so I had to crank up the heat on my furnace and go for iron (which I can still find some scraps of) to make what I want. salvage and pack rat what you can, you might not be able to in the next few years.  :ShakeHead:

Offline zeeprogrammer

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Re: Made without castings ???
« Reply #41 on: November 01, 2012, 10:52:53 PM »
Yes google is great...once you know the term or concept to look for...or what to look for. Otherwise it's a bit of hit and miss.

I've found this (and prior) forum a more invaluable tool and reference. I try to use google when I come across terms or concepts I don't understand and get an answer there before bothering people here. Although sometimes I ask just so others (that no doubt are wondering the same thing as I) will see the answers too. You just can't substitute the direct knowledge and nuance of experience you can get here.

If I have any advice for a beginner it would be to join a forum.

I have few friends and don't interact with neighbors much. Not that I'm anti-social. Believe it or not I'm somewhat introverted and have great difficulty striking up conversations. The 'mask of zee' helps a lot'  ;D

Still...word is getting around. Especially at work. We're moving a few miles down the road and they're getting rid of old equipment. Scored a nice dial indicator and a multi-meter and I've got my eye on a bunch of plate aluminum.

On a different note (somewhat from the thread talking about mags)...I often cruise google now as if I'm reading a magazine. Now that I've gotten a better handle on what to look for.

As a kid, the model engineering magazines had a huge influence on me. Better than comic books. And the advertisements were a big part of the enjoyment where you could see all the offerings and drool over things. But over time the articles got smaller, there were more and more of the same ads, and the price for value got out of hand. And...I hate to wait. The internet is a winner there too. But I do miss those magazines.

Side note: I've been keeping everything now. If it's bigger than a chip...it's in my scrap box.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Zee-Another Thread Trasher.

PatJ

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Re: Made without castings ???
« Reply #42 on: November 28, 2013, 03:51:28 AM »
This is a really old thread, but I am getting really old too, so maybe a good fit?  Only a year, that is not nearly as crusty as I am.

Getting into castings is not an easy road from any prospective, for a number of reasons.

I set my entire shop up for bar stock work, and then had to compress everything to create space for mixing, molding, woodworking equipment for pattern making, and space for general foundry equipment.  I had to "go vertical" with wall mounted shelving, and an outdoor storage shed for non-essential equipment like my wife's car.

Learning foundry work has been much like learning how to machine model engines, it can be difficult and tedious to learn.

For machining, I had to learn how to read the machine dials, how to use all the bits, how to grip the material, types of bits, shapes of bits, drill and tap charts, thread types, metal types, finishing, silver soldering, etc.
The drawings I made were drawn 1:1 on paper, in a what-you-see-is-what-you-get fashion.

For a foundry, you have to start all over and learn an entirely new skill set.  Woodworking becomes critical.  Patternmaking is an art by itself.
Things to consider for patterns include draft angle, machining allowances, shrinkage, etc.
Drawings for patterns are nothing like drawings for the finished part, and you have to think about parting lines, core prints; all sorts of things.

To keep expenses reasonable, most backyard foundry eqipment is hand made from scraps of things.
Many burn waste motor oil to keep the fuel costs down.  Propane is also an easy and economical fuel for most types of castings.

I would guess that anyone with good general modeling skills would also be good at foundry work.
You get out of it what you put into it.

I have read the excellent posts here about how to machine castings, and as a result of those posts, I spend a considerable amount of time thinking about how to add bosses and other temporary projections to allow a cast part to easily be held and machined.  I have found that most commercial casting kits throw you under the train when it comes to giving you a good way to hold a part in the chuck or vice.

The most difficult part of casting for me is........................did you guess it?
Thats right, getting the sand to have good green strength so the pattern can easily be removed to make the mold.

I don't do lost wax, that is a whole new level, and not one that I am going to go to.
I will stick with sand, although I have converted to a self-hardening resin-binder sand, and that solves a world of problems, but is not an inexpensive way to go for just a few castings.

The big payoff is never having to make heavy machining cuts.  The worst case for me is a few skims of the surface, and perhaps drill a hole.
With silver soldering, you can avoid most heavy cuts too, but I love gray cast iron, and don't know of a way to silver solder it.

So you basically have to learn two hobbies, machining and foundry work.
It can be done, but takes time, effort, planning, and money, and the risks have to be well understood and avoided (burns, fumes, etc).

A good half way point for many is to make patterns, and then find a foundry to cast the part.
Unfortunately finding a foundry, especially an iron foundry, is about like finding a diamond, and about as expensive as buying a diamond.
It is really no fun going around begging a foundry to do a one-off small part in iron.
Pouring your own iron is not easy, but more fun than begging or getting denied multiple times, or getting qouted exhorbitant prices.

Foundry work, like model making, is addictive.
Once you get into it, you can't really do enough of it.
There is always that next more challenging project/engine.
Add 3D modeling to the mix and chances are you will need to consult a therapist.
But its fun, that is for sure.

Why do I post here?
I know a lot of these folks from old forum times, and have admired their work for years.

And I use people like JasonB's work as a gauge for my casting quality (sort of like a machinability index for metals).
Right now my castings are at about 20%JS (Jason scale, remember you heard it here first).
If I can get to 80% JS, I will be whistling Dixie and considering my work an overwhelming success, but that is a tall order, and the JS scale is like the Richter scale, the difficulty of achieving quality goes up exponentially as the numbers increase.
« Last Edit: November 28, 2013, 04:23:17 AM by PatJ »