Author Topic: Correct scaling  (Read 3023 times)

Offline DavidA

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Correct scaling
« on: December 11, 2010, 05:03:35 PM »
On two occasions I've tried to ask this question on MEW site.  Both times it hasn't worked. An Email to David Clark didn't elicit any response either;  most unusual.  So maybe you can help.

Whilst looking at the ME drawings for Don Young's Fowler 4f I notice that he has the wheels,  which are 63" in real life,  down as 4.19" Diameter.
Now, if you use the standard guage (4' 8.5") against 3.5" guage to get the track scaling it comes out at 16.143 : 1  (let's call it 16 : 1)
.  So I reckon that the wheels should really be 3.9" dia.

The main reason I query this is that I'd like to build,  some time in the future, a 3.5" or 5" guage model from an original general layout drawing of Stroudly's  Gladstone.  And I'm unsure of the correct scaling to use.

I do realise that the wheels are usually made slightly over scale to help things stay on the track.

Any ideas ?
Or is this a question that dare not speak it's name ?

Dave.

Offline Jasonb

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Re: Correct scaling
« Reply #1 on: December 12, 2010, 03:07:06 AM »
The wheels are not made overdiameter to help things stay on the track, its more to do with the Tractive Effort where having a larger dia wheel is less likely to give an overpowerful engine that causes wheelspin. The distance between the wheel flanges, tyre profile etc are what help keep the loco running on the track and allow it to get round the tight corners found on model tracks.

I'm not really a loco man but hopefully someone else can enlighten you in a bit more depth.

Jason

Offline sbwhart

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Re: Correct scaling
« Reply #2 on: December 12, 2010, 03:34:52 AM »
Dave the wheel difference are as near to dam it correct, he probably chose a wheel diameter that allowed him to use a casting that was available. Many of the great model designers played fast and lose with the scale of things there's no such thing as a perfect scale model. If you want to design your own engine I would recommend you get hold of a copy of:- Martin Evans Manual of Model Steam Locomotive Construction ISBN 0 85344 086 7 its out of print but they can be I picked up second hand I got mine from flea bay.

Hope this helps

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline DavidA

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Re: Correct scaling
« Reply #3 on: December 12, 2010, 07:00:54 AM »
Stew,  Jason,

Thanks for that.
Actually I missed a bit when I said made over scale.  I meant that the width of the wheel was usually wider than scale,  not the diameter. I realise that He had the diameter close enough for all practical purposes,  4.19" as to 3.9",  but my whole point is what is the correct scale ?  If it is fairly flexible then I'll go for 16 :1.

I don't intend to redesign the Stroudly,  The drawing from NRM provides most of the dimensions. But I will need to convert all these to the appropriate scale for the guage I eventually choose.
I'll keep an eye open for the Martin Evans book.

Dave.


Offline DavidA

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Re: Correct scaling
« Reply #4 on: January 02, 2013, 02:13:41 PM »
Actually bought the book last month (December 2012) from Amazon.

Dave.