Real World Model Building

[Grant Jones]

This dissertation is really more about how/what we build rather than what we build it with.

 My background is Mechanical Engineering. In the time I have been doing model engineering projects I have made a few observations that I want to make comment on.
 These comments are specific to all components that are constructed by the casting process and machined to finished size.

In the real world (long before the advent of CNC), the process of casting is/was selected for many good reasons:

1.       -It allows odd shaped parts to be mass produced.

2.       -It allows non-critical surfaces to be left in their cast state, with machining labour expended only on critical  surfaces.

3.       -Types of cast metals are generally very machinable.

As model builders I think we lose sight or do not know these aspects of the real world.
I note that builders machine several, if not all of the surfaces on a giving casting, something that does not happen in the real world.
If we are building a true model of the real world, it should look like the real thing!

There are two forms of drawings for a cast component. The first drawing is the patternmaker’s. His drawing takes into account the mould-making process, and for this reason, expresses dimensions in a more approximate form, which is usually whole numbers and fractions (in the Imperial system). The second drawing is that of the machinist’s. First of all, his drawing should denote all surfaces requiring machining by placing small “V”’s on the drawing. Secondly the drawing is dimensioned in whole/decimal numbers, with the number of decimal places indicating the precision of machining.

All of the model builders drawings I have seen, do not show the “V”’s and mix fractional dimensions with whole/decimal dimensions. I think the reason for this is due to the fact that model design drafts people do not know these facts.

As I said above, model builders are machining/surfacing surfaces that should be left in their “as-cast” state to resemble the real world component. Drawers and builders should be made aware of this. Of course components in this day that are produced by CNC and not casting is a different situation.

Grant Jones

[Jasonb]

Unless you are working in larger scale leaving a model casting "as cast" is often not appropriate.

-The foundry seldom use scale sand so the texture of the surface is often far too rough for example say full size has a surface similar to 120grit arasive paper, I have yet to see  a 1/12th scale model with a surface like 1500g. So to get a scale looking model the surface may need work with a diegrinder and or filler.

- Mould part lines, this simply do not scale the part line on a 1:1 casting is as big as that on a 1:6, 1:12 etc casting so again these need dressing.

- Mould shift again on a full size casting a shifty of say 1/16" is left but if the mould boxes on our small models move the same amount the step will scale upto over 1" of shift

- Poor Fettling a small nick with a grinder, saw or linisher at the foundry on a full size casting will not be that deep but the same size nick on a model could again represent a large flaw when scaled.

As for drawings not showing which surfaces are to be machined you obviously have not seen as many model drawings as me I quite often see the V, VV or VVV marks and various other tollerencing.

Fractions and decimals on the same drawing are also used in the same way as the number of decimal points to signify tollerence, the fraction being the least critical, the one with the most points the most critical.

You also missed off your list that castings were used for economy of material

J

[b.lindsey]

Grant, your observations are interesting and will likely generate some interesting discussion, which I look forward to. If I may, let me ask you to post an introduction in the "Introduce Yourself" section so that we all have a greater sense of your background, interests in model making, etc. if only to provide a larger context to your comments in this thread. Meanwhile welcome to the forum and I look forward to your active participation.

Bill

[fcheslop]

Pretty much as Jason. But if you want the model to look like a slap in the gob just leave all the mould lines and fettling faults
Its each builders option to finish or not
CNC in the home shop can be a great asset and not simply for industrial use just wish I had one
cheers

[Tennessee Whiskey]

Mr Jones,  I concur with b.lindsey , an introduction would be much appreciated.  While I do take merit to a portion of your comments,  I must admit,  as your first post,  it was somewhat insulting to the collective of fine builders here. We will welcome you here as we would family,  yet,  I feel your "greeting " wasn't appropriate for a first post. 

Eric Douglas
Cletus

[Stuart]

With regard to castings I have to agree the quality of green sand castings we get are vey corse texture far to rough for our size.

Now if they the CI ones were made with a shell moulding system then they would be to scale , the bronze ones are the same but some are lost wax castings again these are ok .

Now I have worked in works that did green sand and shell mouldings the latter was used to cast nuts and bolts in ductile they screwed together without machining , at the other end of the scale vertical sand cast 36 inch CI pipes and large built up mould for slag ladles .

The main problem with the current crop of castings is they can be course or they are under sized , both cause us the purchases many headaches


So to sum up yes they are a boon but they are also a pain the smaller the scale the uncouth texture is objectionable in my eyes and needs to be reworked to get the desired finish.

But each to his/her own the above is my personal view

Stuart

[Don1966]

What I would say to your observation is, if you have a better method of casting the models to a scale that meets the proportions of a larger size engine, I for one am all ears. Most of the people that work with casting already know about your observations.

Don

[zeeprogrammer]

Grant's post did raise some thoughts in me.

I know there are people who will do anything/everything to make a model look as prototypical as possible. (Right terminology?)
I'm not one of those but certainly admire those who are.
My only gripe is that once in a while you come across someone who looks 'down' at those who don't.

He also raised the discussion about scale and some have commented on the difficulties to get 'scaled casting features' (flash, texture, etc.)

I can't say I've seen much on this...but are there members who try to simulate casting by machining raw stock and either using a blaster or paint with fine sand or powder in it? I recall Stan's project...can't remember at the moment though.

In any case...yeah Grant...make an introduction and join the club. 

[fcheslop]

Maybe Im looking at this wrong but Iv yet to see a quality machine tool manufacturer leave a cast finish unless its war finish machines
Also the castings from the good old days ?? are of a higher quality even for mundane kitchen equipment .
Times have moved on so I suppose I should accept what small manufacturers can supply at a reasonable cost. Still dont like casting
cheers

[jadge]

Maybe Im looking at this wrong but Iv yet to see a quality machine tool manufacturer leave a cast finish unless its war finish machines

You beat me to it! Most of my older machine tools have a nice smooth finish on those parts of the castings which are not machined. But they were fettled, filled, rubbed down and painted.

On my traction engines I am definitely not machining areas that do not need it. I usually fettle with wire wheels and flap wheels to get rid of casting sand, dirt and the worst of the lumps. Then files for the odd hard to get at lumps and sometimes a bit of filler and sandpaper for holes. I'm not aiming for a super finish and it doesn't worry me in the slightest if things aren't exactly true to prototype. 

The main thought I had from reading the OPs post was that he possibly needs to get out into the real world a bit more. 

Andrew

[derekwarner]

Guys....one manufacturer [Winfried Niggle in Germany] manufacturers a range of model steam fittings, valves & accessories

The process he uses with these fittings is Auto/CNC machining, precision silver soldering and finished off by glass powder blasting with the finish a realistic scale of cast components 

I have a number of components & the quality is excellent with the image of a steam isolation below......  Derek

[gbritnell]

Hi Mr. Jones,
Might I ask what prompted you to write your introductory story? My take on your presentation is that modelers who work with castings are finish machining them completely.  Having been involved in this hobby for a great many years and starting out by machining and building engines supplied as casting kits from companies like Stuart and Reeves and from individuals like Paul Breisch and others I can say emphatically that I have only ever machined a casting where it was necessary.
If as others have stated the casting has a rough texture due to the type of sand used in casting or the parting line has produced a fin then some filing or sanding is necessary to show that we as craftsmen care about the finished presentation of the part or assembly.
In regard to drawings being a mix of decimal and fractional dimensions I won't say they don't exist but what I have found is drawings produced by Stuart, at least the ones I worked from, are fractional inch dimensions. Most likely because at the time they were drawn this was the standard for dimensioning. 
Drawings created by myself and most of the other fellows that venture into that area are all done with decimal dimensions.
I think we are fully aware of the proper drafting requirements when we create our drawings.
On another note, I was a metal patternmaker for 40 years working for an automotive company and I can tell you that we worked from the same engineering drawings that the machinists worked from. The pattermaker's job was to be able to read a drawing and make pattern or corebox from that drawing. We never had two different drawings for given part.
I think you are remiss in stating that we as model builders don't understand the aspects of the real world when it comes to castings. If you would follow these forums you would find that quite a few of the fellows do a lot of searching and studying on how things were made 'back when' and have an extensive knowledge of the design and engineering that went into machines and castings.
It's hard when someone makes a first posting and basically tells us we are doing everything wrong without providing some background for your argument.
Please give us a little more insight into what your background in modeling or machining is. This way we may better understand your dilemma.
gbritnell

[Stuart]

That's why a pattern maker uses a pattern makers rule which automatically add the correct allowance to the pattern when working from the drawings


Stuart

Ps  I am not the Stuart that produces castings and I have no link to the company that uses my name

[Jasonb]

I can't say I've seen much on this...but are there members who try to simulate casting by machining raw stock and either using a blaster or paint with fine sand or powder in it? I recall Stan's project...can't remember at the moment though.

Zee go rub your hand over a few full size castings and they should not feel like a surface with sand mixed into the paint!

On my fabricated engines I go over the surfaces that will be painted with die grinder, flap wheels, files etc which knock off all the hard machined corners and add a few undulations. On some I have also stippled on a thick primer coat which leaves a texture that carries through to the finished paint.

For non painted parts that have needed work to tidy up poor cast surfaces I have used an electric engraver to put teh texture back onto the surface. This carb casting needed a lot of work around the boss where the elbow fits



After a bit of work with teh engraver the texture has returned



J

[Jasonb]

George touched on the subject of fractions on drawings in particular Stuart's drawings. Mr Jones may do well to bear in mind that at the time these engines were first designed and marketed the average model engineer was working with a steel rule and a pair of friction leg callipers, a micrometer was rarely seen in the home workshop.

I would very much like to see some examples of Mr Jones's models and also some examples of all these castings that he has seen that have been machined all over. In 30yrs of model engineering I can only think of 2 or 3 castings that I have had to extensively machine "cast" surfaces. In all cases there were due to poor castings and I did my best to rework the surfaces to again look like they were cast.

Mr Jones if you are reading you may also want to take a look at this rogue casting thread as I will be covering surface defects and why they need to be addressed to make the model look like the real thing.

http://www.modelenginemaker.com/index.php/topic,5908.msg115742.html

[Jo]

All of the model builders drawings I have seen, do not show the “V”’s and mix fractional dimensions with whole/decimal dimensions. I think the reason for this is due to the fact that model design drafts people do not know these facts.

The "drawings" supplied for models are normally referred to as plans rather than drawings as they are rarely done by professional draftsmen but by hobbyists. Often by the original designer who out of the goodness of their heart having created a design have made their plans available to others. Commercial companies looking to provide the castings for engines have often redrawn the original design as part of their Model Plans service so that the purchaser has something to build from. There is little money to be made supplying castings, so they are not going to pay to have professional drawings made and if they did the strange modern drawing notation would no doubt confuse most of their audience, who are still working in a measurement system that was superseded in the UK by metric nearly 50 years ago  .

As I said above, model builders are machining/surfacing surfaces that should be left in their “as-cast” state to resemble the real world component. Drawers and builders should be made aware of this. Of course components in this day that are produced by CNC and not casting is a different situation.

Grant Jones

A model is made by an individual to meet their own intent: some to prove that they are capable of making a running engine and they care little for the model's aesthetics, others prefer that their should make a shiny jewel the exceeds what the full sized engine would have ever been and they (and their wives) give it a place of affection in the house, and then others will be looking to produce a scale model right down to requiring the casting to have a scale cast finish so that they can enter them into shows and win prizes with them. All will meet the intent of their builder and will have given them many happy hours building them

Jo

P.S. If I called our Draftsmen at work "Drawers" I would have my ears chewed off 

[paul gough]

Hi grant, The points you raise may be true of the 'real world' however imposing the parameters by which something is made from here to the model world is failing to grasp the essential differences in these two dichotomous realms. The designer in the real world is usually faced with producing something under the dictatorship of profit generation. The modeller on the other hand has and should have the freedom to express his intentions as he see fit. Suggesting a narrow catechism for production is likely to snuff out the creative candle that burns within modellers and indeed potential modellers. I noted a similarly confined view in a communication elsewhere regarding Gauge One Locos where the author demanded of builders to conform to their 'responsibility' to paint their engines in exactly the same colour as the original ones. Some pointed replies were forthcoming. Also, and in the context of modelling, I cannot help but recall a profound piece of philosophy by a French fisherman commenting on life, "Everybody should have the right to live out their own madness unmolested". I'm not suggesting you are molesting any of us, but the notion of suggesting a conformity to 'prototypical' precedence for its own sake seems to me to be a confinement many object to and is only one way among the infinite. Rigidity leads to brittleness, flexibility leads to resilience. Regards Paul Gough.

[Stuart]

Jo

I thought females wore drawers    not called technical draftspersons names



Opps got the wrong end of the stick again good job I have got an appointment with spec savers

Stuart

All in the best possible taste   

[Stuart]

Well said Paul


Must say I am a bit worried about a single post that the OP posted and not been seen since


Stuart

[tangler]

This little troll has turned up on the Yahoo Myford group as well.  Has he been wandering to any of the other home engineering sites?

I am constantly surprised by, presumably intelligent, professional engineers who assume that the "proper" way to engineer something is to use techniques that are appropriate for mass production.  It seems to suggest that they can only make something if they have precise, mindless, instructions to follow.

I think our pécheur has it absolutely right.

Rod

[10KPete]

Rod, it has been my experience (being in mechanical engineering for 50 years) that the best Engineers are the ones who are able
to build what they design. Usually it's a life style, not a job based on a bit of paper.

Pete

[paul gough]

Rod, Don't know if the fisherman philosopher would appreciate being labelled a 'sinner' though like most of us he probably is. I think you meant pecheur with ^ above the e. Makes a big difference in meaning and pronunciation. Regards Paul Gough.

[tangler]

Pete,

I'm not making a dig at professional engineers as a class - I've worked with them all my life .  Just those that occasionally pop into "our" world and say that they "can't make something from these scrappy drawings, there isn't enough information, it isn't drawn to the correct ISO standard and I can't see which surfaces have to be machined and which don't".  You and I can work out which are the important dimensions and which aren't.

Rod

[tangler]

Rod, Don't know if the fisherman philosopher would appreciate being labelled a 'sinner' though like most of us he probably is. I think you meant pecheur with ^ above the e. Makes a big difference in meaning and pronunciation. Regards Paul Gough.

   I really must use a larger font on my screen.  I read recently of a plan by the French to reduce the number of accents, particularly the circumflex.

Cheers,

Rod

[Jo]

This little troll has turned up on the Yahoo Myford group as well.

Thanks Rod 

Jo

[fcheslop]

Boy we sure know how to make people feel welcome

[10KPete]

Pete,

I'm not making a dig at professional engineers as a class - I've worked with them all my life .  Just those that occasionally pop into "our" world and say that they "can't make something from these scrappy drawings, there isn't enough information, it isn't drawn to the correct ISO standard and I can't see which surfaces have to be machined and which don't".  You and I can work out which are the important dimensions and which aren't.

Rod

Oh, I never took it that way at all. I was just saying that the best I've met could build as well as design. I spent the last 10 years or so of my career in a position of being able to provide some OJT to green engineers. I was kind of shocked over how
little practical engineering these kids were taught in school. They had some good theory but some had no idea of tools....

Pete

[b.lindsey]

Pete, you are right about that!!  Dealing with engineering students every day from freshmen through seniors they come to think of design as being skilled in Solidworks, et.al.  To them the difference between .001" and .0001" is simply a setting within the CAD program. Little  recognition of what that difference means as far as actually making a part and or what it takes to do so. Once they get down in the shop though to actually work on the prototypes for their senior design capstone projects, the full force of reality hits them square in the face. That alone is probably one of the most valuable lessons learned in 4 years of engineering school, just wish it could be poured into their head a few years earlier

Bill

[philjoe5]

"I fear we may have had a visitor from the Academy of Projectors" - Gulliver

[sshire]

Bill is spot on.
He at his university and Scott(Cheepo45),at the U. Of Delaware, are opening the eyes of many student engineers. Going from CAD to turning the handles on a Bridgeport is a "character building experience."
I'm sure that, once they must build what they've designed, much redesign occurs.
It's good to have a nutburger post occasionally. Keeps us on our toes.
Waiting for reports from the other forums that he's infiltrated.

[90LX_Notch]

To me, Mr. Jones comes off as a "bench racer". Or, as the younger generation says "a poser".   I don't understand the machined all over point of view unless he doesnt realize that some people polish, etc. there models to a high finsh.

I eagerly await photos of his highly and authentically detailed engines.  Even then, it depends on the scale of the engine.  At 1/2 scale, it is very easy to make something look authentic  At 1/10, it becomes daunting.   And of course this depends on the original size of the engine being modeled.

One engine that I did pieces of fuzz and dust would scale to the size of electrical wires.

-Bob

[wagnmkr]

I think Mr Jones has what he wanted ... attention and a bit of pot stirring. I would doubt he has ever built anything of substance. I would be very curious of his take on the "threading root vegetables" thread.

Tom

[b.lindsey]

As I had said in my initial reply, I felt that this thread could generate some interesting discussion and it has done that. Let's all be careful about not letting the thread turn into a bashing of any particular point of view though or anyone for that matter. Perhaps Mr. Jones will return to clarify his post, perhaps not. In any case let's DO preserve the level of decorum that MEM is known and appreciated for.

Bill

[10KPete]

I think Mr Jones has what he wanted ... attention and a bit of pot stirring. I would doubt he has ever built anything of substance. I would be very curious of his take on the "threading root vegetables" thread.

Tom

Aye! Let's see the pattern maker drawings for that turnip! 

Pete

Oops, sorry Bill.

[mklotz]

As I had said in my initial reply, I felt that this thread could generate some interesting discussion and it has done that. Let's all be careful about not letting the thread turn into a bashing of any particular point of view though or anyone for that matter. Perhaps Mr. Jones will return to clarify his post, perhaps not. In any case let's DO preserve the level of decorum that MEM is known and appreciated for.

Oh, rats!  And I was just finishing typing a reply prepared with my usual delicacy of expression and sympathetic charm.  I even had a cheerful, piquant video to accompany it.

[tvoght]

... my ususal (sic) delicacy of expression and sympathetic charm...

I thought that was the level of decorum that Bill was referring to.

--Tim

[steamer]

As I had said in my initial reply, I felt that this thread could generate some interesting discussion and it has done that. Let's all be careful about not letting the thread turn into a bashing of any particular point of view though or anyone for that matter. Perhaps Mr. Jones will return to clarify his post, perhaps not. In any case let's DO preserve the level of decorum that MEM is known and appreciated for.

Oh, rats!  And I was just finishing typing a reply prepared with my ususal delicacy of expression and sympathetic charm.  I even had a cheerful, piquant video to accompany it.

 

[crueby]

Aw come on Marv, post it! Probably some good quotes I could use elsewhere!!   

[Maryak]

My only gripe is that once in a while you come across someone who looks 'down' at those who don't.

Hi Zee,

Known in the Land Down Under as Rivet Counters and is definitely meant as a derogatory term.

Regards
Bob

[Maryak]

Ever been sucker punched?

Well, by reacting to his initial post, I feel the pain in my kidney, exacerbated by my moral outrage.

The cure is a large dose of, "Who gives a shit what he thinks?"

Bob

[wagnmkr]

Bill, you are absolutely right ... the Gentleman is innocent until proven guilty. I apologize for jumping to conclusions,

Tom

[b.lindsey]

Tom, I was not referring to any specific post, including yours, just the direction of the thread in general.

Bill

[Tennessee Whiskey]

Bob, I agree wholeheartedly.  The rest of the crew here was quite eloquent in thier replies,  and I commend them on their behavior,  I just think the old boy shot his mouth off in the wrong "bar"  , and you know where that will get you  .

Cletus

[b.lindsey]

OK, I think we have covered the modeling side of this issue so with that I am locking the thread.

Bill