The Home Machinist!

Patterns, in the hands of a fool, won't necessarily produce high quality. A great deal of credit should go to the man ramming the sand.

I have long been an advocate of one making reasonably high quality sand castings, but it requires an individual with the proper attitude, along with considerable skill. It's very different from investment (or shell) casting, where the pattern, alone, dictates quality. How a mold is rammed and the pattern removed plays a huge role in the end product. I won't make mention of the fineness of the sand in use, but it, too, is important, especially if fine detail is a consideration.

Harold

And if the foundry does make an excellent casting, it can be destroyed by the cleaning crew that grinds the gates off later in the process.

Jim B

rrnut-2 wrote:And if the foundry does make an excellent casting, it can be destroyed by the cleaning crew that grinds the gates off later in the process.

Jim B

Yep!
I had a cone mold poured, long ago. I made the pattern with nice little feet, which were all removed by the cleanup operation, just as you described.

Cone molds are commonly used in the smelting process for precious metals. The values accumulate in the tip of the cone, with the sulfides, as well as the slag, forming distinct layers above the values. The relatively small surface area of the resulting button is much easier to clean.

Harold

There's been some interesting discussion on the post recently, thanks to all the contributors! The past month has been great as far as progress is concerned, I've had an average 2-3 hours a day in the shop making chips. Work is still concentrating on the modification of Challenger frame castings to suit the Big Boy design. I've also been fabricating various ancillary components such as the front engine lubricator supports and boiler centring device.

The front engine lubricator supports have been fabricated in brass to match the drawings. Once all the parts were brazed up I finished off all the profile radii on the rotary table. It was tricky to get all the radii correct, but I took my time and I'm happy with the results. I took to all the edges with a dremel and carbide burr to blend, smooth and replicate the contours of the cast original.

Components for the boiler centring device brackets are all done, hoping to get a chance to braze them in the next day or two. I do my brazing at work where I can use the company o/a set and not have to worry about lack of heat or the gas bill haha

Dan,
I sent you the drawing of the 4000 series injector. It's in your PM inbox.

Big boys did pull group trains on occasion and pictures are around to prove it. My grandfather rode behind one in WW2 don't remember which one though.

So It's been just over a year since my last update...

I've been distracted with the crane build and a few other little projects, but with the news that Roger has dropped the last of my castings off at the freight forwarder I've found the inspiration to get stuck into the loco once again. I decided I should finish off the engine truck first as that would make a nice milestone. As most of the tracks down here in Australia have steel rail I new steel tires were a must.

In keeping with the rule of thumb, allowing 0.001" of undersize for every 1" of diameter, the cast iron wheels were turned to 4.1250" and the steel tires were bored to 4.1210". The tires were left on the stove until they showed the slightest sign of colour then dropped over the wheel.

I chose 4140 for the steel tires because that seems to be the most popular material for the application. They should last longer than my lifetime!

Next I'll turn the treads after I grind up an appropriate carbide tool.

Two weeks ago I finally picked up the last of the castings at the docks, all 600lbs of them! It feels good to be at a point where I have all the major components and from here on out it's a case of making parts and machining castings. I figured I would document the parts in one big progress photo for posterity so I laid them all out, climbed a ladder and snapped a few shots.

Since then I've been tackling the manufacture of springs, something entirely new to me. After a lot of reading and asking around I decided to cut all the leaves with an angle grinder and clean up the burrs with a "flappy disc" abrasive wheel. The 1mm ultra thin cut-off discs made light work of the cutting and kept heat to a minimum as to not affect the temper of the 1095 material. Next step is to drill or punch the holes, I'm still on the fence between deciding to drill or punch. Straight flute carbide drills are reputed to make light work of such a task but I've been told using a punch is the way to go from a number of sources... we shall see what eventuates.

After having no success turning the treads with the carbide tools I'd ground, I opted to buy a parting tool holder and radiused profiling insert for the job. I'm pretty happy with the results but there was a bit of chatter right in the corner where the tire meets the flange.

Turning the treads between centres with my home-made fixed steady.

Hello DanSmo,
The photos you took of all those lots of castings well arranged look great!
Your method to shrink steel rims on casted spoked wheels seems just right to me: 1 / 1000 can be used as a standard due to stay within the limit of elastic deforming of materials ( < 0.2 %) - just good!
I did the same just recently by using an electric pizza oven to warm up the rims to about 250 °C.
A little less than 1 / 1000 may be used safely for cold press fits to fix wheels on the axles, too. No ahesives necessary at all!
Your centering device looks simple and needs very small height, I like it.
Please continue posting your progress for all of us modelers, thank you!

Asteamhead