Author Topic: Model Engine for LMS 1831 (AKA Wallaby)  (Read 28770 times)

Offline NickG

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #15 on: November 04, 2012, 11:20:35 AM »
Very interesting, thanks for showing  :ThumbsUp:

Offline Bezalel

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #16 on: November 04, 2012, 12:17:28 PM »
Nick, Jan


Thanks for dropping in.


After ramming up a mould and doing a pour I ended up with these castings.
 





As the photos above show, there is what looks like a horizontal crease along the outside of the casting. This is the signs of a "cold shut" where liquid metal coming from two directions meet at a temperature too low to blend into a continuous solid piece of metal. This one is not bad enough to be porous but I think I'll discard it any way, for aesthetic reasons.


A cold shut can occur when the metal is not very hot (cool ali gives a smoother finish) and the mould takes too long to fill, which may indicate that the gates into the mould from the runners are either too few or too small.


The gates into this casting are in the ends of the casting (as can be seen the photo).
I moved the gates around to the sides for all future sump castings - problem solved.  This one is going back into the furnace for another go.









Apart from the observation about the gates, I'm pretty happy with whats coming out of the sand from those two patterns so now I need to move on to considering the core for the main block, which is a little bit more complex than ordinary cylindrical core used for making simple steam cylinders (ones that don't have cast in steam passages at least - I think that's what they are called)


I drafted up a rough representation of what I think it should look like  - I used Google sketch up ( the free-bee )


a quick animation gives you an idea of what the core should look like from all sorts of angles. remembering that the real core also needs to take into account the horizontal cylindrical cavity for the cam shaft.


Click:Click



Bez
« Last Edit: November 04, 2012, 12:43:38 PM by Bezalel »
Queensland - wet one day, humid the next

Offline ScroungerLee

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #17 on: November 04, 2012, 01:34:01 PM »
Thanks for this, I will certainly learn a lot.

Lee
Mmmmm.... Shiny!

Offline NickG

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #18 on: November 04, 2012, 03:12:38 PM »
nice work, I wish I could do my own casting.  :ThumbsUp:

Offline Bezalel

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #19 on: November 04, 2012, 08:58:00 PM »
Nick


Wishing is usually the first step.


I might go out on a limb here and suggest you also once said "I wish I could build my own engines"


My sources tell me you have taken a few more steps since then, you not only build 'em, you design and Power them as well.





nice work!


What you are seeing in this thread so far, is not the result of any formal training just lots of individual lessons that each casting provided. The bigger the stuff up, the more important the lesson. And trust me I have made quite a few "important lessons"  :facepalm:

But that shouldn't discourage you.  Just jump in, like you did with engine building.


Try this...............    step 1. "I wish I could do my own casting"


...........................   step 2. "I wish know I could do my own casting"


...........................   step 3 "I wish know, I could do my own casting"




 
Bez
« Last Edit: November 04, 2012, 09:16:48 PM by Bezalel »
Queensland - wet one day, humid the next

Offline Don1966

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #20 on: November 04, 2012, 09:08:44 PM »
Nice work Bez, this may motivate me into starting. I do have all the equipment. My trouble is time and business as I haven't retired yet.

Don

Offline Bezalel

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #21 on: November 04, 2012, 09:21:25 PM »
Thanks Don,


I'm just about to finish my weekend very soon too   :'(


off to work  :atcomputer:  and  :killcomputer:


Cheers


Bez
Queensland - wet one day, humid the next

Online steamer

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #22 on: November 04, 2012, 10:04:56 PM »
Nice Thread Bez!   I'm not there yet....but i MIGHT be......one illness at a time though... 8)

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline NickG

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #23 on: November 05, 2012, 07:05:10 PM »
 :Lol: Thanks Bez,

I guess you're right, I've done a few bits when I've put my mind to it and I am the sort of person that needs a shove in the right direction from time to time.

But what you've done here feels a million miles away from my simple trig and machining!

That said, would love to give it a go one day. When my dad used to work at a school I did do some small aluminium castings with him, and they turned out ok but they were very simple - there seems to be so much to think about.

Nick


Offline Bezalel

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #24 on: November 05, 2012, 11:57:03 PM »

Your welcome Nick.


When it came to building the core box, I had to find a way to simplify the complex shape into a few easy to make flats and curves.


Strange as it may appear at first sight there is only 3 simple shapes involved;


  • a rectangular prism ..................................the water jacket
  • 2 bell shapes with flat, parallel sides...........the crank cavity
  • 3 cylinders...............................................the cam recess & cylinders
The parting  line


Is important because I need to get the core out (and be able to use the core box again) so I elected to put the main parting line parallel to the crank axis.


Having decided on a parting line, lets start with the most complex of the simple shapes,


The crank cavity

Starting with a block of  2" x 2"  of brown stuff, (about a 6" length is enough) draw one half of the bell shape on the end grain to mark where you need to remove the inside of the bell. You can see the marker line in some of the photos below.


Cut the 6" length in half  or into two full lengths of the finished core.  Take one side (now the cam side) and drill a 7/16" hole where the cam recess is to be. Then smooth up all the contours with some sawdust making devices.


Water jacket


Take a bit more of the 2"x 2" and cut a wide channel in it, then cut that to be the same lengths as for the crank cavity.   These will form the sides of the water jacket.





Cylinders

The remaining shape is the two cylinders.  T make these it is just a matter of  drilling/carving/filing the two 3/4" holes down through all the parts assembled so far.


Top & Bottom core prints


So far we have only accounted for two sides of a 6 sided core box. At the top and the at the bottom of the core we need some core prints, (protrusions that can support the weight of the core until it can be suspended in a sea of the liquid metal.



For the top core prints I made two cones, drilled into the top board. These need to be accurately (who im I kidding this is W### ) aligned with the cylinders.  I made a core print drill to do this, which may sound like a waste of a spade bit but I'll probably use it on future core boxes.











The bottom needs some core prints also, to support the core in the mould. This comprises of two tapered recesses in the bottom board.


Between the two tapered recesses and also glued at right angles to the bottom board is a 12mm wide divider that will form the center main bearing support web.


This may sound all very complicated but its not really,  I'm just organising wood to be where I want aluminium and sand where I don't, and building it one bit at a time. 
Dare I say? its a bit like the reverse of machining. Instead of machining off the bits I don't want I'm gluing on the bits I do.   (and hacking off the bits I don't want too)   


The last two sides


These are just two flat boards or at least they w### be if the water jacket didn't stick out either end of crank cavity. This problem is easily solved, again with a ball nose bit to carve out the extra bit to make the water jacket longer.




Assembling the core box & Ramming up


The core box parts



The Water jacket



The crank cavity



top and bottom boards



side boards to line up all the bits and start ramming up the core sand



Fully Assembled  ( you can see here the intricate w##d craftsmanship they'll be admiring for centuries to come) :lolb:



Ramming up  (I think you can see the table is still shaking from the vigorous ramming up) :LittleDevil:



releasing the core












In this state the core is very carefully transfered to the oven.  For instructions on how to prepare the oven for concurrent achievements there is another useful thread HERE http://www.modelenginemaker.com/index.php/topic,878.msg9924.html#msg9924


The core sand is not normal green sand, its a tried and tested formula I got from Tel.
basically, when mixing the core sand, do the same as for green sand.  Except,  just substitute a couple of ingredients.   Replace the bentonite with flour and add molasses to the water, in a mix of 1:10 -( add a bit more if you like the Anzac biscuit smell. Just don't taste them else you'll have to make more!! No need to any way, I can tell you, their just like eating sandwiches at the beach  :naughty: )


After baking, the core will happily support its own weight between its extremities.







next post I'll drop it in a mould cavity.


Thanks for dropping in.


Bez
« Last Edit: November 06, 2012, 02:48:03 AM by Bezalel »
Queensland - wet one day, humid the next

Offline Don1966

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #25 on: November 06, 2012, 03:11:25 AM »
Wow! Bez that is so awesome stuff. Thanks for the blow by blow and the great photos. You might just inspire and motivate me into starting my own casting. I just need to figure out what to start with and not start to complicated, less I would fail and get discouraged. I am learning a lot here, keep up the great work.

Don

Offline Bezalel

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #26 on: November 06, 2012, 12:48:39 PM »
Just grab anything just to get started.


Here is one

The pattern was plastic





I had cast a lot of things before I started making patterns,  I think the first thing I cast was a small metal draw handle off a chest of drawers, and my Avatar was among the fist half dozen things I cast. It is Aluminium.
The only reason its Black is because I was experimenting with electro-plating copper onto cast Aluminium. It got a nice thick fluffy coat of copper on it but when I lifted it out of the electrolyte the copper literally dropped off leaving behind that layer of rich black copper oxide that leached into the casting. :insane:
An unplanned result but quite pleasing just the same.


Go on get into it  :Director: you know you want to.


Bez
Queensland - wet one day, humid the next

Offline Don1966

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #27 on: November 06, 2012, 03:20:27 PM »
Thanks Bez for the motivation, I will have to start some time. Work has picked back up again. I guess I need to pick back up when it slows down. I will be following as you progress and try to pick up some good pointers.

Don

Offline Bezalel

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #28 on: November 07, 2012, 12:17:57 AM »
Don


Regarding those "good pointers"; its worth checking them for inconsistencies against an independent reference!

Don't want anyone picking up any "bad pointers" I'm self taught after all ,...... and the teacher..... Well..... lets not talk about him. :censored:

Bez

Queensland - wet one day, humid the next

Offline Don1966

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Re: Model Engine for LMS 1831 (AKA Wallaby)
« Reply #29 on: November 07, 2012, 12:44:08 AM »
Not to worry Bez, I have my own set of books to reference to. Just want to pick up some of the tricks the book doesn't teach. I am self taught also down to my machining. There are online videos that do get down to the basics. The machining videos I bought from Swarfrat.com are very good educational videos on setup and how to use certain tools.

Don

 

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