Stuart Plans, I dislike under constrained dimentions

[HSM01]

I though I was beginning to understand Stuart D10's plans. I was incorrect.
Bare minimum dimensions are given. One would have thought paper was expensive!
I also work in thousands and the conversions from fractions is a PITA. I guess conventions were different back when.

Sometimes I failed to inspect the related sketches on the plans.
I am at the beginning and working on the sole plate.

I was tempted to lay out the centerlines for the standard (V-shaped cylinder support) using the distance between the bearing centerlines.
It didn't look right.
Then I noticed the centerlines between the bore given in the steam pipe layout as 1-13-32 or 1.565".
If I calculate the distance between centerlines on the throws of the crankshaft, it's 1.406".
One is .159 off or the crankshaft throw is not on the centerline of the bore.
I am not getting this. Does anyone care to help me out on this issue?
Thanks
Rick

 

[rleete]

Cranks are not symmetrical?

 

[ninefinger]

I think its just your conversion math that is a bit off, 1+13/32" is 1.406"

 

[HSM01]

I must have typed it into Excel incorrectly. I am going to see how it works out on my layout.

 

[HSM01]

That was it. I consider it a success if I hadn't messed up the part.
The sign of a good mechanic, is they stop right before they mess something up.
I got lucky on this one. Appreciated the help.

 

[Mark_1984]

There’s a great app for the iPhone called Fraction Calculator Plus. Calculates in fractions and gives the answer in both fractions and decimal. A real time and dock up saver!

 

[Richard Hed]

I though I was beginning to understand Stuart D10's plans. I was incorrect.
Bare minimum dimensions are given. One would have thought paper was expensive!
I also work in thousands and the conversions from fractions is a PITA. I guess conventions were different back when.

Sometimes I failed to inspect the related sketches on the plans.
I am at the beginning and working on the sole plate.

I was tempted to lay out the centerlines for the standard (V-shaped cylinder support) using the distance between the bearing centerlines.
It didn't look right.
Then I noticed the centerlines between the bore given in the steam pipe layout as 1-13-32 or 1.565".
If I calculate the distance between centerlines on the throws of the crankshaft, it's 1.406".
One is .159 off or the crankshaft throw is not on the centerline of the bore.
I am not getting this. Does anyone care to help me out on this issue?
Thanks
Rick

I'm with you on the complaints about not enough info on the dims. There may be a lot of dims that are not necessary to put on the plans but there are also a lot that really need to be added. I too like to make p;arts to correct and complete plans. The first Stuart I did, I was astounded when I was looking for certain dims. Had to find them on another part--not the way I do things.

And also, I always do up any new plans in Alibre, AutoCAD or SolidWorks so that I can become more familiar with the parts, put them together in assemblys, print out all the pages I need on clean paper with ALL the correct dims. I've complained other places, far too much before, -- soon I should get my boy scouts complainer badge.

 

[djc]

Old Chinese proverb: man with one watch always knows the time. Man with two watches never sure.

It has been a tenet of engineering drawing since forever that dimensioning is necessary and sufficient. That has been arrived at through long experience and has proved itself least costly in terms of actual and potential errors.

People reading the drawings are expected to develop the skills necessary to work within those parameters.

Consider the alternative: you would complain more (and the complaint would be justified) if a dimension was shown in two places and the two places contradicted.

 

[Richard Hed]

Old Chinese proverb: man with one watch always knows the time. Man with two watches never sure.

It has been a tenet of engineering drawing since forever that dimensioning is necessary and sufficient. That has been arrived at through long experience and has proved itself least costly in terms of actual and potential errors.

People reading the drawings are expected to develop the skills necessary to work within those parameters.

Consider the alternative: you would complain more (and the complaint would be justified) if a dimension was shown in two places and the two places contradicted.

Does this mean I finally get my Complainer's Badge?

 

[olympic]

People reading the drawings are expected to develop the skills necessary to work within those parameters.

Good point.
My Covid project was a Stuart 10V, the first thing I ever built from castings.
I'm self-taught, with no technical background whatsoever, and like HSM01 I prefer working in decimal equivalents of fractions. I found that careful arithmetic handled the fractions, and I also found, or inferred from various parts of the drawings, every dimension I needed.
My 10V ran fine on the first try.

 

[GreenTwin]

I have my preferences about dimensioning parts.
I think everyone has a style that they like.
I notice that folks often do it differently.
I lean more towards the heavy side on dimensioning, but don't really like duplicate dimensions.
And some folks start from a centerline and dimension outwards.
Others dimension as if they were programming a CNC machine, or setting up a milling machine.

Its all good as long as it is correct.
I don't use fractions; I use decimal only.
No metric for me; I am very content with Imperial.

For things like cutting grooves in pistons, I like to dimension from one end, with offsets, so I can use these directly in the digital vernier calipers mounted on my lathe tailstock (poor-man's DRO).
.

 

[Tug40]

Remember this is a model steam engine, not an airliner or a gunsight.
This is from a PM Research model blueprint.
I treat all model steam engines the same.
They’re very forgiving, you can make mistakes & they’ll still run.
As always, YMMV

 

[GreenTwin]

One thing I discovered here was folks using over and under reams, which I find very useful.
I was not previously aware that such things existed.
.

 

[Jasonb]

Back in the day when these engines first came out there would not have been much point in using decimals as most builders would have only had a steel rule and firm leg callipers. No mic let alone digital. So they would measure the part with the rule or set the calipers to diameter with the rule. I expect most here would moan about having to convert decimals back into fractions if they only had a rule to use.

Again they would not have been able to afford much in the way of reamers but would simply make the male part to fit the hole.

Same with something like that base, they would not have set it up on the mil and used the DRO to position the holes. The standards would have been stood in place and the hole positions in them transferred to the base so you don't need to dimension the holes on the base.

If you want it upto date then redraw it and offer the supplier a set of your drawings so they can then give the customer a choice. I have done this a few times not only correcting mistakes and adding missing detail to old drawings but also converting to metric. That is a full conversion using metric stock and whole millimeters not just the mathmatical conversion of 1"=25.4mm.

It is almost impossible to say "no metric or no imperial for me" but if you actually want to make engines then you are going to have to mix it a bit. Spark plugs are a good example as standards on our engines are typically 1/4 x 32 UNEF or M10 x1 and if you want to use pipe threads then they are imperial based even in the metric world.

 

[Steamchick]

My 50-year old calculator converts fractions to decimal, if you can't do it in your head, or on the back of a cigarette packet with a pencil. (My phone lets me talk remotely to people).
1/2 = 0.5
1/4 = 0.25
1/8 = 0.125
1/16 = 0.625
1/32 = 0.3125
1/64 = 0.15625
1/128 = 0.078125
etc. (Did that in my head. Do I get a gold star teacher?)
Maybe my schooling was different? Computers were Huge IBM rooms of cabinets, fed by punched cards or tapes by men in white coats. Not the things in your pocket or modern workshops. So we learned simple arithmetic.
OK, Decimal inches to decimal Metric was done by slide rule. a 6 inch slide rule fitted in your pocket next to the 6 in steel rule...
Thus we could use the old imperial lathes' indicator scales or those on the new metric machines. We just had to be careful we were using English or Metric appropriate to the machine's scales. None of these new fangled "digital verniers", but CALIPERS with Vernier scales. Perfectly good down to 0.002" (~0.05mm) as I still use them today? - The batteries have not expired yet on my Grandfather's 1920s (Vernier) Caliper. - The Vernier scale is in 1/20ths of a mm. - Who said Metric was new in British industry? - The Imperial scale is in fractions to 1/128th inch.- Easy, as my Milling machine and lathe both have metric scales.
I would guess... because I don't use one - that the electronic digital scale you use can be changed at the press of a button to with in the Alternative dimensional system? Ones I used at work (nearly a decade ago) did change from metric to Imperial at the push of the button. the dimension selection button was next to the "Zero" button, so it was easy to press the wrong button and confuse yourself. Big fat Worker's fingers and thumbs on an instrument designed for slender delicate Ladies' fingers... = like my phone, etc.!!
K2

 

[bengt-olausson]

I though I was beginning to understand Stuart D10's plans. I was incorrect.
Bare minimum dimensions are given. One would have thought paper was expensive!
I also work in thousands and the conversions from fractions is a PITA. I guess conventions were different back when.

Sometimes I failed to inspect the related sketches on the plans.
I am at the beginning and working on the sole plate.

I was tempted to lay out the centerlines for the standard (V-shaped cylinder support) using the distance between the bearing centerlines.
It didn't look right.
Then I noticed the centerlines between the bore given in the steam pipe layout as 1-13-32 or 1.565".
If I calculate the distance between centerlines on the throws of the crankshaft, it's 1.406".
One is .159 off or the crankshaft throw is not on the centerline of the bore.
I am not getting this. Does anyone care to help me out on this issue?
Thanks
Rick

I bought a Stuart S50 the drawings was the worst I ever been seen. Missing dimension,
Wrong dimension also. Fraktion dimension as well./
Bengt

 

[GreenTwin]

I started in the hobby making 2D drawings only, and I am very good at 2D drawing work, but I found that invariably I would introduce errors into an engine design if I used 2D drawings only.
I finally started using 3D modeling, and now I assemble the mating pieces one at a time, and use the motion study, along with transparent surfaces, to check for intereferences.
In Solidworks, the parts will not move in the motion study if they do not fit correctly, and that is one of the best error checks I have ever seen, and really revolutionizes model engine design in my opinion.

I have had discussions with magazine editors, and they insist that an engine be build and be run before they will publish an engine article.
I have told more than one that if the engine runs in Solidworks motion study, it will run in real life, assuming you know how to machine engine parts correctly. The editors I have talked to don't believe me, but it is true, at least for my steam engine designs.
For a complex engine like a V8, the motion study would not necessarily guarantee that the engine will run, but you could rule out conflicts/interferences.

The process of deriving the 2D drawings from a verified 3D model pretty much ensures that the 2D drawings will be correct.

As they use to say in a television commercial, "we have come a long way", and in just a few short years (during my career).
.

 

[ninefinger]

My 50-year old calculator converts fractions to decimal, if you can't do it in your head, or on the back of a cigarette packet with a pencil. (My phone lets me talk remotely to people).
1/2 = 0.5
1/4 = 0.25
1/8 = 0.125
1/16 = 0.625
1/32 = 0.3125
1/64 = 0.15625
1/128 = 0.078125
etc. (Did that in my head. Do I get a gold star teacher?)

Doing it in your head is fine, but double checking your work is better. You missed shifting a decimal place down at 1/16 of an inch and carried the mistake down through 1/128 (i.e. 0.0625 ... 0.0078125)
No gold star for you!

Its mostly not about the unit of measure, more about the attention to detail and ability to catch mistakes before they happen. Adding conversions just gives us more opportunities to make more mistakes.

 

[Jens Eirik Skogstad]

Easy to learn and use fractional to build up the Stuart Steam engine, learn by this link..

https://www.stefanelli.eng.br/en/simulator-reading-vernier-scale-fractional-inch/

I did with fractional measurements when I build my Stuart triple expansion steam engine.

 

[HSM01]

Back in the day when these engines first came out there would not have been much point in using decimals as most builders would have only had a steel rule and firm leg calipers.
If that were the case today, I would not be building models. I have trouble looking at small items and currently use magnification to read a scale to the 16th. I thank God for modern tools and the privilege of getting old.