Author Topic: Scaling question  (Read 4143 times)

Offline iosens

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Scaling question
« on: April 23, 2016, 03:15:23 AM »

This is about scaling bolts and nuts for a steam engine model.

Let's say it is an engine with a cylinder diameter of 20 inches in original scale.

If I want to create a model in a scale of 1/20 how big do the bolts and nuts have to be?

Even the smallest size 0-80 bolt with a 5/32 nut will be  1.5 inches in real life, while the nut will be  3 inches in 1/20 scale.
(and it gets worse for bigger engines and let's say 1/30 scale).

It seems to me that 0-80 is really the biggest size that can be used to be close to scale.


Am I wrong?

Thanks






Offline Alan Haisley

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Re: Scaling question
« Reply #1 on: April 23, 2016, 03:25:40 AM »
How big would the bolts, nuts, and studs be in the full size engine?

Alan

Offline Dan Rowe

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Re: Scaling question
« Reply #2 on: April 23, 2016, 04:32:43 AM »
You will need to use scale nuts to make it look right.
The scale nut size for 0-80 is 3/32. See here for source:
http://americanmodeleng.com/id41.html

Dan
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Offline GailinNM

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Re: Scaling question
« Reply #3 on: April 23, 2016, 05:06:25 AM »
It can be a problem.  We had a discussion about some of this about a month ago at:
http://www.modelenginemaker.com/index.php/topic,5946.0.html

Some times you just have to make your own.  Here are some M1-25 hex head bolts that I made for a current project.

http://www.modelenginemaker.com/index.php?action=dlattach;topic=5946.0;attach=44893;image

These were made on my small CNC lathe but I have made them on manual tools also.  I have made screws down to 0.5mm diameter (0.020 inch) in the past but eyes don't work that well now that I have passed the 3/4 century mark.
Here is a link to the making of these screws.  It is part of the above thread.

http://www.modelenginemaker.com/index.php/topic,5946.msg117769.html#msg117769

Gail in NM
I would like to be the kind of person my dog thinks I am.

Offline Ian S C

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Re: Scaling question
« Reply #4 on: April 23, 2016, 03:33:08 PM »
A twenty inch bore steam engine is going to have studs at least 1" diameter, so if it is Whitworth the nut will be 1.48" AF, or if UNF/C It will be 1.5". I think the old standard for Whitworth nut was 2D.
Ian S C

Offline iosens

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Re: Scaling question
« Reply #5 on: April 24, 2016, 12:25:26 AM »
Thank you very much. That's just what I thought.  The typical 0-80 or M1.8 screws that are commercially available are just too large, especially the nuts.

Thanks again

Offline Dan Rowe

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Re: Scaling question
« Reply #6 on: April 24, 2016, 02:18:12 AM »
Here is a list of sources for small fasteners.

http://www.modelenginemaker.com/index.php/topic,628.msg5766.html#msg5766

Dan
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Offline b.lindsey

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Re: Scaling question
« Reply #7 on: April 24, 2016, 02:48:51 AM »
Is there a particular engine you have in mind? A picture of it perhaps. While I understand and agree with the dimensions discussed above, use of 0-80 hardware for a 1" bore engine, seems small to me. Most model engines of that size would typically use 4-40 or even 5-40 hardware. The nuts would need to be "small pattern" to look more realistic, there would only be 4 to 6 fasteners or studs with nuts typically holding the head to the cylinder. Would help to know what you have in mind.

Bill

Offline paul gough

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Re: Scaling question
« Reply #8 on: April 24, 2016, 07:05:24 AM »
Ian SC Touched on something important if you are intending to be  prototypically accurate. During the war nearly every means possible was applied to reduce the amount of metal to do any particular job. Hence the Whitworth bolt head and nut sizes were supplanted by B.S.W. or 'British Standard' Whitworth which had reduced sizes ( 1.5 x Dia.), I assume the same sort of thing might have applied to the Unified system in the U.S. It is not a huge difference but might be noticeable to a connoisseur or give you a size bigger stud or bolt to use. For a working engine some latitude is usually allowed especially if you want to use steam at 100 psi or 6 Bar, approx. Sometimes absolute scale accuracy cannot be achieved. With sensitivity, what looks right is entirely justifiable and can be just as aesthetically pleasing. Regards, Paul Gough.

P.S. In the 19th century a lot, if not all of nuts were chamfered on the top face only, the face that mated with the part or washer was flat. Looking at some of my early 1850 locos engravings some manufacturers used square nuts for securing iron or plate work and hex nuts for machinery or machinery fixing. Square nuts invariably used securing timbers whether with square head bolts or coach bolts.
 
« Last Edit: April 24, 2016, 08:39:52 AM by paul gough »

Offline Ian S C

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Re: Scaling question
« Reply #9 on: April 24, 2016, 01:23:55 PM »
Nuts! With square nuts, most people put them on upside down, on old machinery the idea was to put the side with the chamfer against the item being bolted up so that the corners didn't dig in.  Modern nuts often if not chamfered on the face have a ( :headscratch:)washer face, and the chamfer on top so you don't knock your knuckles on the corners.
Over the last few decades the AN standard for UNF/C aircraft nuts and bolt has changed and the AF size has been reduced by one spanner size, ie 10-32 used to be 3/8", now the size is 5/16", the bolt heads also have a dimple, all this removes many pounds of weight from a large aircraft.
Ian S C

Offline Dan Rowe

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Re: Scaling question
« Reply #10 on: April 24, 2016, 02:40:58 PM »
The original question was asking about a 0-80 screw, this leads me to believe that the OP lives in North America where such things are common.

The rule for hex nuts and square nuts in the US at the time most steam engines were built is 1.5D +1/8". So to make that simple I just multiply the diameter of the bolt by 1.5 then look for the nearest larger fractional size for the AF.

So for a 0-80, D=0.06" X 1.5 = 0.09". The nearest larger fraction is 3/32" so that is the best choice for the AF for a scale US heavy hex bolt. This is the size used by American Model Engineering and all the bolts they sell follow this rule fairly closely.

Cheers Dan
« Last Edit: April 25, 2016, 03:01:47 PM by Dan Rowe »
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