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Old 01-01-2014, 12:35 PM   #1
rodm1
 
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Default People that build from blueprints?

When you get a large complex print do you review the job until you see the project in your head in 2 or 3 dimensions? I can read the easy less complex prints but the large complex prints get me baffled. I have a hard time seeing the end product and I think it's a must to avoid mistakes and develop a game plan.

What do you think in your head when you start on a large project and what process do you go threw.


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Old 01-01-2014, 01:20 PM   #2
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All of my engines have been built from drawings. Elmer's, Bill Reichart's and Liney Machine.
Early on, I don't think I could have had working engines without the extensive notes with most of these. Photos and assembly drawings are also important. The last engine, the Liney RV2 was very short on notes and "good" assembly drawings and made for a bit more thinking about what part goes where and what that part does. I wasn't shy about emailing Doug at Liney to ask questions.
Unfortunately, Elmer and Bill Reichart are both gone so the email isn't an option.
I spend a bit of "chair time" with the drawings until I think I have a pretty good handle on how everything works and fits together. I also try to think about how I'm going to hold and machine a part. On small or irregularly-shaped parts, I try to keep enough extra metal to safely and securely hold the part as long as possible in the machining sequence.
On most engines, I've built from the base up. That way I can do a rough assembly as I go to be sure I haven't made some major error.
Finally, on parts that require a number of machining steps, I write a list of the steps in sequence. This has saved me from stupid mistakes or "painting myself into a corner" more than once.
It's also likely that someone here or on other forums has either built the engine or can explain why a part does what it does. Ask questions.
Hope this helped.


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Old 01-01-2014, 01:21 PM   #3
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I find it very difficult to visualize in 3D if the part is at all complex, like a cylinder casting with multiple cores/ports, and have to sketch it in multiple sections (slices) to visualize how things relate to each other. I just spent months figuring out how to design a rotary valve for Trevithick's 1803 engine in 1:12 scale because I can't "hold all the detail in my head at once" and an isometric drawing was just too complex to follow. In the end I had to do multiple sections and views on paper (CAD) to figure it out, about 3 sheets just to detail the valve body. When it come to the workshop, I will just follow the drawings carefully because I wont be able to visualize the 3D part until it is almost finished.

Some people have better 3D abilities but I am not one of them.
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Old 01-01-2014, 01:27 PM   #4
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Now that's a hard one, some people cannot visualise a finished project just by looking at the drawings, although in this day and age with CAD systems to do the drawings with, you often have a 3D solid to look at. On the other hand, there are people who can visualise the finished job from the detail and assembly drawings. I guess that, with practice, the ability to visualise the end result becomes easier.

My wife cannot visualise any renovations that I want to do before they are started, she always says that once they are done she will see if she likes them, a bit late by that stage.

Paul.
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Old 01-01-2014, 01:30 PM   #5
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Quote:
Originally Posted by Swifty View Post
My wife cannot visualise any renovations that I want to do before they are started, she always says that once they are done she will see if she likes them, a bit late by that stage.

Paul.
Are you married to Nancy Pelosi?
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Old 01-01-2014, 01:51 PM   #6
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rod most prints have a sheet with the assembly drawing. so it shows all the parts and there relative position.

start simple if you have never made an engine make a few easy ones to gain experience before you dive into a large project.

Read project books explaining the details and steps of the project. The Kozo locomotive bools are great even if not building a loco it breaks down the steps shows a plan and shows in detail how to make parts that add up to a model locomotive.



Quote:
I have a hard time seeing the end product
1) I encourage all in this hobby to learn free hand drawing. It trains the eye hand and mind to work together.
A copy of drawing on the right side of the brain is a few dollars on the web.
2) I encourage all to redraw each part to be made. this will help you wrap your head around it. draw the part on a file card that can easily be placed near your tools or machine for handy reference. then file in a card file or recipe notebook when done.
many people like to redraw in 3-D cad this can really help see what the part will look like.

Quote:
I think it's a must to avoid mistakes
3) I have told folks here before there are no mistakes . The home model shop is akin to a college engineering laboratory. It is a learning lab. As such expect to make a few practice pieces. Practice with a goal in mind ! Make the goal a model engine of your choice. In the beginning you may have have to make to or three practice pieces before you get one that is up to your standards . but that is OK.
Quote:
develop a game plan
4)By all means develop a plan but make it flexible fluid even.
I think the key here is what works for you but will give ideas.
a) the obvious first step is to choose a plan set.
b) choose a starting point . some will start at the base of an engine and add parts one at a time . this is a good method.
Others will start with the cylinder make the piston, heads con rod cross head etc then mount the parts on the base.
b) then assemble material and tooling for at least the first part of the project. And remember extra stock for those practice pieces.
c) choose a part and start then when complete make another part.
5) Keep a notebook white down what you do. record your successes so you can repeat them. ad record your failures so you can avoid them.

An please ask questions here folks can help with any step from selecting a plane to setting up a particular part.

Tin
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Old 01-01-2014, 02:37 PM   #7
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To amplify what Tin said:

"I encourage all in this hobby to learn free hand drawing." I'm not good at it, but sometimes just drawing the interrelationships of parts (in different positions if they will move) helps. If it's for yourself, then it only needs to have significance for you. I have a problem with keeping scale and perspective, so I always have some graph paper (although it's getting hard to find nowadays) for helping my sketches stay oriented and rough-scaled.

I have CAD on more than one computer, but not always in the shop, so I still work off paper there most of the time. I sometimes re-draw in CAD, but just to the level I need for my own use. What I take into the shop might flunk me out of a CAD class, but It will be what I need to understand and make the part. (Aside: This is what's good about designing in 3-D modeling mode, you can generate any view or 2-D dimensioned plan from the model without changing anything in the actual virtual design.)

I also translate the working sketch or drawing into instructions, especially if they are more complex.

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Old 01-01-2014, 02:46 PM   #8
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I'm not very good at seeing things in 3 dimensions. I studied the Stephenson Reversing linkage on a number of engines but just couldn't see how it worked. I was working off plans of a very well known and respected designer, Ray HasBrouck. Finally I decided to make all the parts and assemble them. Once I did that it was astonishing how simple the mechanism is.

I had the same problem seeing the Watts linkage approximating linear motion on a beam engine I built. I just made the parts, then fit them together.

Cheers,
Phil
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Old 01-01-2014, 03:02 PM   #9
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I have found that it helps me to redraw in CAD even when I have the original drawings. I spent most of my working life designing and building industrial equipment so I have been making and using drawings most of my life. Every time I try to take a shortcut and just start making parts I end up regretting it. I have never used 3D CAD but because of my experience I generally can envision it from 2D. Obviously folks with different a background are going to have a different reaction. Place a complex financial statement in front of me and I wonder what all of the numbers mean.
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Old 01-01-2014, 03:09 PM   #10
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Professionally I'm a machine designer - particularly leak test machines, often for the automotive or pharmaceutical industries. I do the mechanical design of the machine and my own prints which are then transferred to the company's the machine shop for manufacture.

I can tell you that sometimes as the designer you just can't win.

There was a time, several years ago, that I did a print of a part. It was given to two machinists concurrently. Neither of them liked the way I dimensioned the part. Either they didn't understand what it was to look like or they were just lazy. The weird thing, was that the each machinist wanted the print drawn differently!

...So I had ended up doing a print for the same part three times.

As for visualizing what the part is to look like, it's very important to know if the drawing is in first or third projection. Most drawings in the USA are drawn in third projection. (i.e. if you're looking at the top view of the part, the view to the right will be the right side of the part).

Many drawings from Japan and Europe are drawn in first projection. (i.e. if you're looking at the top view, the view to the right will be the left side of the part.) This seems confusing, but it has to do with which direction the view is rotated (concave - third projection vs convex - first projection).

Often times it doesn't matter (e.g. the part is symmetrical). But when I'm looking at a catalog of parts, like electrical sensors or vacuum pumps, I really need to pay attention which projection the drawing shows so I can re-model the part correctly to incorporate into my designs.

...Ved.


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