Lets Talk about Engine Drawings

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ulfw said:
If making them better you should use mm
Click to expand...

At one time I considered going metric, but then I inherited a lot of Imperial tooling, and to change now would not be cost effective.

Its a shame everyone does not use the same system.

I generally use decimals for my drawings/designs, but things are available in inches here, such as shaft sizes, drill sizes, tap sizes, etc., and it seems like the Imperial selection of tooling and fasteners is better around here.

I did consider metric seriously though years ago.

.
 
In the 1960s I worked in an Engine refurbishment and machine shop.... Many designs of engines had the nearest Imperial dimension quoted for a metric size. There was no 3 inch piston, they were all 75mm! But quoted as 2 61/64th - or whatever!
I had a British bike with 80mm bore and 90mm stroke - or something - but nothing else metric on the whole bike. Even the oversized pistons when I did a re bore were 0.020in oversized on the 80mm bore!
Just use whatever is most appropriate for your brain....
Just avoid Korean inches, 10 to the imperial foot. Korean steel rules have 12 inches one side and 10 on the other....
K2
 
hehe Well, inches have been metricized into thousandths and they are based on the meter at NIST. Just a little bit of 2.54 on everything and you're in business.

(Edit: I'm all for metric too. Should have been switched back years ago, but all my tools are imperial like some of the others).
 
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Stacked dimensions are fine, if you are using a manual machine without a DRO, and the tolerances can really work that way.

(don't know the correct name) Zero Reference dimensions are more common with CNC manufacturing or if you are using a DRO. You need someplace to call zero and so every dimension is referenced off that point.

I have made parts where the draftsman was thinking he was being nice, but when you got all done the tolerances stacked up and parts would not work. We found out how it was assembled and the drawing would not work to make a useful part unless all tolerances from the one end were at their absolute minimum.
 
When I was a designer back in the 1970s & 80s, I had a few draughtsmen drawing my designs for a couple of years, then after an enforced change of jobs, found myself doing my own drawings. I quickly learned how tolerances make parts work - or not - and the cost of getting it wrong. But getting it right (tolerance-stack-up, etc.) was very satisfying - except the Production Engineer could not understand tolerances wider than his machining capability.... But it reduced scrap to nil, all the same!
The equipment was a mix of precisely made rods inside a pair of ceramic insulators, manufactured tolerance +/- 2mm, and welded steel frame, manufaturing tolerances +/- 1 mm. to 3 mm, but the rods were unnecessarily +/- 0.5 mm or less! There were final assembly adjusters to a setting achievable within 0.5 mm, which worked well. So I reduced the scrap rods by increasing the length tolerance and the adjuster compensated anyway...
A bit of fun when the final thing worked better than previous designs. It was helped by a computer model studying the high speed motion, stresses, measurement of elastic performance and stress in certain parts, a some clever modification of a pneumatic damper that stopped large over travel at the end on the piston stroke.

K2
 
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It’s been quite awhile since I did a paper drawing even cad as the places I worked went to paperless shops it was really rare to send a drawing to the prototype shop . Generally I completed a model of the part then saved it to a general file . A daily summary was sent to the cnc department. As far as tolerances only very specific ones were listed in notes at best the were done with adjustable tooling like a boring tool . Tolerances were controlled by how good the machines were the cnc shops iv worked with assumed a minimum of 3 places generally 4 places were easily obtained you modeled according to this clearances were built into the modeled all of us engineers has principals of geometric tolerance f so we modeled accordingly basically we didn’t worry about tolerances except as they applied to models . Bolt holes lined up bores were straight an fit mating parts as we had designed. If something was amiss we got a call “ hey Mr smart engineer you need to come and see this” “ please explained how we are supposed to put a hole like your model shows . You really didn’t want these calls as verbiage wasn’t gentle. And your reputation took a big hit .

Today if I have my son make something I almost have to go out and have a classroom session . If I could see I’d make parts myself . The doctor about has a fit if I let it slip I was making chips Out in the shop .
 
This is a drawing of my flathead engine block. Bottom view. It is dimensioned with ordinate or datum dimensions. (basically) This cleans up the drawing and makes it much easier to read. When a drawing has a lot of dimensions in a row, like hole positions, and is dimensioned co-ordinately the you have long extension lines and stacked dimensions and extension lines. There's nothing wrong with co-ordinate dimensions it's just the ordinates simplify the view. All my machine work is done manually and I find this type of dimensioning much easier to use. It has nothing to do with whether it's for CNC manufacturing.
 

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  • FLATHEAD BLOCK BOTTOM.pdf
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a41capt said:

My projects in my drafting classes (1965 to 1970) always ended with ink on vellum, including the hand lettering (anyone else remember TOM Q VAXZY? 😉). I’m not sure I could still ink with a lining pen, or even think of a reason to try! Nothing more fun that watching the ink run under your triangle on the vertical lines…

If you’re doing that kind of work GreenTwin, I’m definitely impressed!!!

John w

I would not say I am doing Kozo-level work, although I did learn pen and ink on vellum in drafting classes back in the 1980's, and made all of my engineering drawings by hand in the pre-CAD pre-computer days, using pencil on vellum, and sometimes ink on vellum (generally ink was used for Leroy lettering).

But rather I try to mimic the Kozo-style of layout, flow, spacing, clarity, contrast between various lines, etc.

Kozo is the master.
I am a little Kozo wannabe, and I understand I will never be a Kozo.

Below is an example of Kozo's work from Live Steam and Outdoor Railroading, Jan/Feb 2020, Vol. 54, No.01, pages 36, 37.

What I like about Kozo's work is the variation in line width, which gives 3D depth to a 2D drawing, the absolute clarity to each part, the dimension layout and spacing, and the dashed leaders showing association with mating parts in his isometrics.

Not only does Kozo produce very clear and useful drawings, but in my opinion he produces works of art too.

His top, side, left, right, bottom, views always align with the front view, and in general, the drawings are intuitive to read and understand.

kozo-423.jpg
 
By contrast, here is another individual's drawings, which are a metric converstion with a little bling added to the flywheel, and these were based on the information shown on my Bernay drawings. The "originator unknown" noted in the lower right of the titleblock below would be me.

(my original Bernay drawings in Imperial are located at this link)

https://www.homemodelenginemachinist.com/threads/bob-js-bernay-steam-engine.34339/

Everyone has their preferred drawing style, and I don't think any style is necessarily right or wrong.
I can only mention the things I find helpful in a drawing, such as clarity, ease of use and reading, etc.

For me, these drawings are compacted more than I would prefer.
The mix of 2D, 3D and color does give them a distinct look.

I use color in my 3D models, but not in my 2D drawings, since color drawing reproduction can be very expensive, and color drawings don't necessarily print very well on a black and white printer.
I try to use either secondary or tertiary colors in my 3D models, and avoid using primary colors, since I find the primary colors to be overwhelmingly bold.


Back in the day, we did not have computers or color graphics, so everything we drew was basically grayscale.
There was no standard method of reproducing drawings in color; it was all bluelines on an old ammonia machine.

I have seen some old drawings that did use various colored inks, but I only used Indian black ink on my drawings, and pencil.
The use of color in drawings, and especially the reproduction of color drawings on color printers is a relatively new thing.


If you are developing an engine from scratch, this sort of layout does not work very well, since you may have to change the size and arrangement of parts and their dimensions.
If you are copying someone else's drawing information (as was done below), you can more easily compact things and remove all the white space from the drawings.


bernay39.jpg
 
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GreenTwin said:
By contrast, here is another individual's drawings, which are a metric converstion with a little bling added to the flywheel, and these were based on the information shown on my Bernay drawings. The "originator unknown" noted in the lower right of the titleblock below would be me.

(my original Bernay drawings in Imperial are located at this link)

https://www.homemodelenginemachinist.com/threads/bob-js-bernay-steam-engine.34339/

Everyone has their preferred drawing style, and I don't think any style is necessarily right or wrong.
I can only mention the things I find helpful in a drawing, such as clarity, ease of use and reading, etc.

For me, these drawings are compacted more than I would prefer.
The mix of 2D, 3D and color does give them a distinct look.

I use color in my 3D models, but not in my 2D drawings, since color drawing reproduction can be very expensive, and color drawings don't necessarily print very well on a black and white printer.
I try to use either secondary or tertiary colors in my 3D models, and avoid using primary colors, since I find the primary colors to be overwhelmingly bold.


Back in the day, we did not have computers or color graphics, so everything we drew was basically grayscale.
There was no standard method of reproducing drawings in color; it was all bluelines on an old ammonia machine.

I have seen some old drawings that did use various colored inks, but I only used Indian black ink on my drawings, and pencil.
The use of color in drawings, and especially the reproduction of color drawings on color printers is a relatively new thing.


If you are developing an engine from scratch, this sort of layout does not work very well, since you may have to change the size and arrangement of parts and their dimensions.
If you are copying someone else's drawing information (as was done below), you can more easily compact things and remove all the white space from the drawings.


View attachment 146842
Click to expand...
That above - - - - its actually going to be hard to read.
I'd want to take that drawing apart for actual use.

(Hope that you're not insulted by that - - - GreenTwin!!!!)

Regards
 
GreenTwin said:
By contrast, here is another individual's drawings, which are a metric converstion with a little bling added to the flywheel, and these were based on the information shown on my Bernay drawings. The "originator unknown" noted in the lower right of the titleblock below would be me.

(my original Bernay drawings in Imperial are located at this link)

https://www.homemodelenginemachinist.com/threads/bob-js-bernay-steam-engine.34339/

Everyone has their preferred drawing style, and I don't think any style is necessarily right or wrong.
I can only mention the things I find helpful in a drawing, such as clarity, ease of use and reading, etc.

For me, these drawings are compacted more than I would prefer.
The mix of 2D, 3D and color does give them a distinct look.

I use color in my 3D models, but not in my 2D drawings, since color drawing reproduction can be very expensive, and color drawings don't necessarily print very well on a black and white printer.
I try to use either secondary or tertiary colors in my 3D models, and avoid using primary colors, since I find the primary colors to be overwhelmingly bold.


Back in the day, we did not have computers or color graphics, so everything we drew was basically grayscale.
There was no standard method of reproducing drawings in color; it was all bluelines on an old ammonia machine.

I have seen some old drawings that did use various colored inks, but I only used Indian black ink on my drawings, and pencil.
The use of color in drawings, and especially the reproduction of color drawings on color printers is a relatively new thing.


If you are developing an engine from scratch, this sort of layout does not work very well, since you may have to change the size and arrangement of parts and their dimensions.
If you are copying someone else's drawing information (as was done below), you can more easily compact things and remove all the white space from the drawings.


View attachment 146842
Click to expand...
I certainly appreciate JDWDs work, however, I always question why, during the modern ages with all the cheap storage space, one would make such crampt up and difficult to read drawings.

i have redrawn several of his drawings and even tho' my drawings always leave a lot to be desired, they are still easier to read and interpet than JDs
 
He did credit it to your website. You don't actually use your name on there so how would he have know it was PJ
 
Jasonb said:
He did credit it to your website. You don't actually use your name on there so how would he have know it was PJ
Click to expand...

Its not a problem, I was just defining who the "unknown" was to clarify things.
I don't post my name online for obvious reasons, such as identity theft.

I give him the benefit of the doubt that he credited as best he could with the information he had at the time.

.
 
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ajoeiam said:
That above - - - - its actually going to be hard to read.
I'd want to take that drawing apart for actual use.

(Hope that you're not insulted by that - - - GreenTwin!!!!)

Regards
Click to expand...

I am not insulted by anything these days; its all good.

The only thing that bothers me is folks who build magnificent model engines, and then don't come here and share photos and their building experiences.
We all need to post and share what we got, for the long term benefit of the hobby, and for the next generation that may want to build an engine.

Pat J

.
 
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gbritnell said:
This is a drawing of my flathead engine block. Bottom view. It is dimensioned with ordinate or datum dimensions. (basically) This cleans up the drawing and makes it much easier to read. When a drawing has a lot of dimensions in a row, like hole positions, and is dimensioned co-ordinately the you have long extension lines and stacked dimensions and extension lines. There's nothing wrong with co-ordinate dimensions it's just the ordinates simplify the view. All my machine work is done manually and I find this type of dimensioning much easier to use. It has nothing to do with whether it's for CNC manufacturing.
Click to expand...

That is a really good way to dimension what would otherwise be an extremely cluttered drawing with dimension lines and arrowheads.

.
 
Richard Hed said:
I certainly appreciate JDWDs work, however, I always question why, during the modern ages with all the cheap storage space, one would make such crampt up and difficult to read drawings.

i have redrawn several of his drawings and even tho' my drawings always leave a lot to be desired, they are still easier to read and interpet than JDs
Click to expand...

I have talked to several people who love JDWD's drawings, and he seems to have a great following.

But I would add this thread is about comparing various drawing styles, and I am not trying to single out or personalize anything or anyone, but rather emphasize how widely styles can vary, and point out the drawing styles I admire, and why I find those styles useful.

.
 
What Julius's drawings have done is made it clearer for a lot of people coming into the hobby with no engineering background to "see" what a part looks like and how they go together. Yes his drawings are cluttered but teh isometric images and assembly drawing are both things you seldom see and can be a lot easier for those not used to reading technical drawings to understand.

He also works exclusively in metric which again many now coming into the hobby will have been brought up on and have a problem understanding fractions and things like threads that have odd #numbers rather than the diameter.
 
I think Julius's drawings are works of art in and of themselves, but they are not a drawing method I would choose to use to design or build a model engine.

I know a lot of people who love Julius's drawing style, and so more power to those folks; whatever turns you on is good for the hobby, and will draw more folks into the hobby.

And he does have a big metric following too, which is important to the metric builders.

The added bling he occasionally introduces into an old engine design, such as round holes in the flywheel, is not something I care for, but that is his way of adding a little flair to an old design.
I prefer to keep the old designs as original as possible.

With new designs, anything goes.

.
 
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Not sure if it is added as Bling but as a lot of what he draws was originally intended to use castings the drilled out disc is at least better than a solid one and simpler than replicating a cast look..
 
My definition of "bling" is anything added to an original old engine design, but that is just my definition.

Some folks like to modify old designs in many ways, and that is part of the fun for a lot of builders.

To each their own; I can only state my own preferences.

.
 
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