MAN Diesel engine from 1907 "DM 2 * 100"

[starnovice]

Hmmm ... update!?
Re the core sand glue:
Well, it looks like I have something top secret. I couldn't find it either.
It is best if you contact your local foundry equipment company and ask for a quick core sand glue. The one I use takes less than 1/2 hour until you can cast. There certainly is more than just one manufacturer.


Nick

OK Thanks Nick.

Pat

 

[Herbiev]

Pat have you tried sodium silicate (water glass) and then apply carbon dioxide gas. Its been years since I've cast anything but from memory it sets very rapidly once the Co2 is applied

 

[starnovice]

Don't want to steal Nick's thread, but yes I have used waterglass and it is good for making cores.

However the issue is that sometimes you need to make your cores in multiple parts and then glue them together to get a complete core. Think of all of the cores that go into a water jacket on a V8 for instance.

Pat

 

[MuellerNick]

Once more to the core glue:
The problem is, what you can get locally. I do not know what manufacturers are available at your country. Here, we have at least Hüttenes-Albertus and foseco. foseco seems to be a global player, and so maybe doesn't care of you unless you order 1 ton. You still can phone them and ask for dealers. An other way is to visit/phone a local foundry and ask where they buy. If you visit them, don't forget to take some of your castings with you, that often opens the doors.

Both of the manufacturers mentioned do have a fast core sand glue. They both do contain acetone and sand. Both are waterglass based, but both do not need CO2 from a tank to react.

If all fails, high viscous CA glue works too. But you have to pay attention that it doesn't come in contact with the melt, or it would generate a lot of gas and you'll get blow holes. You also need an activator.

I know, that it is a problem to get professional foundry chemicals. Finding a source is just part of the whole process. Again, your biggest chances are at a local foundry (if still available) and being a bit penetrant and whiny to find the right person that gives you the good stuff. An other weak point to break the chain would be a local representative of a foundry chemicals company. They do have samples, and you can go a long way with what they call "sample". Big foundries need tons of the chemicals per week, you only need a kilogram a year.


Hope that helped,
Nick

 

[MuellerNick]

I hope that was worth waiting for!

Casting #28. Con-rod for the fuel pump, at the right cylinder.


As cast on the tree. Vacuum assisted casting.


Core.


Core box. Here you can see clearly, that I added a venting (better: vacuum) channel around the cavity.

Casting #29. Arm for the regulator.


As cast. The red line is where it will be cut off. Right from the blue line sits a core that makes a slot.
The two cylindrical features will be bored.


Other view where you see the slot. Wall thickness is 1.5 mm.


Core box. Makes one more core than necessary, but they are easy to throw away.


Core sand mould. In the upper mould, the cores are missing. In the lower, they are inserted. In my left hand, I'm holding such a core.


More in a few moments …

 

[MuellerNick]

Casting #30. Con-rod for the fuel pump, left cylinder. As that one has to slip over the cam shaft (the other one sits on the end), it has to be bigger and has a split big end (con-rod is "upside down")


As cast, vacuum assisted.


Sawn off. That's how the parts belong together.


That's where that con rod goes to.


Core sand mould.


And the core box. Nothing exciting.

As you had to wait so long, I'll have something special for you. It's not for this engine, but it shows how far you can push it with the vacuum assisted casting.
More in a few moments …

 

[MuellerNick]

Here's something to make you drool!

I have to admit, I didn't expect that to work. But I had to try. Well, the first two tries failed miserably, but I had enough headroom to tune the parameters and try once more.
So I cranked up the vacuum to the maximum and casted with 710°C. That worked. An other try with a bit less vacuum and 700°C also worked.
That means, I still have some room to get a better surface finish. But as it is now, slight sandblasting will give me what I want.

Handwheel for my Deckel FP1 model.
This handwheel is the bigger one. It only differs in diameter, the spokes etc. have the same dimensions.


The brown spot on the left of the rim is a cast bore. ø1.5 mm, 1mm deep. Diameter of the wheel is 16 mm.
The spokes are ellipses with 2mm mayor and 1 mm minor diameter.
There is some flash on the inner of the rim. That resulted from the milling bit being "too big". I'll tune the core box by hand at that place.


Other view. The axle also is the ingate. Diameter 2.5 mm.
At the remains of the runner, you see that the molt is succed out again. I had a spot in the mold that wasn't completely closed.


Crank for the Deckel. 13 mm wide. The handle is 8 mm long and has a diameter of 2 mm at the narrowest spot.


Handle that goes into the handweel (the cast bore).
Right from the handle is the switch for the spindle motor. Gets sawn off, so that the platen is just 0.3 mm thick.


Core box and core sand mould, one half ...


... and the other one.

Was that worth waiting for?

Nick

 

[Herbiev]

How do you do the vacuum casting?

 

[MuellerNick]

How do you do the vacuum casting?

It is top secret, unless you read posting #30.


Nick

 

[Herbiev]

Thanks Nick. Tried the search function "vacuum" but got nothing.
Never did have much luck with the search function

 

[aonemarine]

Well worth the wait. What size end mill have you been using, and how long of a run time on a mold?

 

[abby]

Nick I think your work is amazing but I am puzzled as to why you use sand castings for such small items.
It is obvious from the pictures that due to the coarsness of sand the surface quality of very small items is not as good as might be achieved by other means.
This locomotive valve hand wheel is by chance the same diameter (16 mm ) and cast in brass using the "lost wax" process

It is obvious that you possess great skill in CNC machining and could make wax injection dies as easily as core boxes so is there a particular reason why not ?

 

[aonemarine]

Nick I think your work is amazing but I am puzzled as to why you use sand castings for such small items.
It is obvious from the pictures that due to the coarsness of sand the surface quality of very small items is not as good as might be achieved by other means.
This locomotive valve hand wheel is by chance the same diameter (16 mm ) and cast in brass using the "lost wax" process

It is obvious that you possess great skill in CNC machining and could make wax injection dies as easily as core boxes so is there a particular reason why not ?

I was wondering the same thing, once my CNC mill arrives that's what I'm planning on doing.

 

[MuellerNick]

That's the endmill I'm using:


Diameter is 1.5 mm, can cut 16 mm deep (not DOC, that is 2 mm IIRC). The funny thing is, that it is intended for hardmilling up to 64 HRC.
A friend gave me the tip to buy these, he uses them a lot for milling engineering samples in plastics. Compared to what he is milling, my work looks clumsy. But he is using 0.4 mm endmills 10 mm long.
They get more expensive the smaller they get. :hDe:

Both core boxes for the Deckel took 6 hours. I roughed them with a 4 mm endmill.


Nick

 

[MuellerNick]

It is obvious from the pictures that due to the coarsness of sand the surface quality of very small items is not as good as might be achieved by other means.

That's a valid question!

There are severals answers:
The simple one: Because I can.
An other one: I wanted to know wether that works.
A third one: I have that process at hand, but not the lost wax casting in that I didn't want to invest (a friend could cast these parts for me).
And a last and the mayor reason for me: I want a casting structure. After glass bead blasting and painting, the structure almost disappears but is still visible. I want that effect, you have to see that it is a casting. The outer side of the rim can be polished (hoping I don't bend the parts).


Nick

 

[starnovice]

I was going to point out that while the surface looks rough if you compare the pits to Nicks finger prints they are about the same size as the lines on his fingers. It is just good macro photography that makes them look big.

Pat

 

[MuellerNick]

Addition:

This is not intended as an insult, this is just my personal attitude towards scale modeling:
All parts do have some character. A milled part looks like it is milled, a turned part looks like being turned and a cast part like being cast. Often, that are small details, or very obvious details.
With castings, it is the shape, the surface structure and the radii in corners.
If you look at the lost wax cast handwheel, it has lost all of it. Sharp corners where they don't belong to, smooth surface. It looks as someone has built it up from 5 pieces, soldering the spokes into the outer ring and the hub. Looks perfect as a work, but wrong as a casting.

An other thing is, that some details don't scale to scale. Means: If the roughness of the original is of value 10 (to whatever scale), that of the 1:10 model is not 1, but more. The reason is, that the human eye is scaling that different and has some prejudice about the process how it was made. If it is too smooth, casting gets excluded and it is seen as being machined.

Also, color do have a scale. A flat black just looks wrong on the model. It looks like a deep sump of black, where details are lost.

But that's just my philosophy…


Nick

 

[Dave Sohlstrom]

Nick

Did a search on those end mills. Expensive is an under statement I think you could buy gold cheaper but it does not make a very good end mill.

I think I am working with small end mills at 3/32" but they are giants by comparison.

Dave

 

[aonemarine]

They say, a picture is worth a thousand words. But they also say a picture doesn't do it justice.
Nick, your castings fall into both. Personally i need to feel one in person to get a real idea of what your doing.
I really hope to do work like yours someday. Maybe in iron too. Time will tell....

 

[MuellerNick]

Personally i need to feel one in person to get a real idea of what your doing.

Yes, it is hard to tell from pictures how the real thing looks like. I always try to show part of a reference (hand), but it still is difficult.

These Deckel parts are more from the R&D-department than being really useful. The handheels are OK, I'm happy with them and I'll keep them. The crank and the handle is ... um ... well it is a casting. In the original, they are polished and chromed parts, so the casting structure makes no sense and is no gain. I think I'll shop them out or at least let make the RTV mould as I do have a spin caster (that is collecting dust).


Nick