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Post by peterhill on Jan 20, 2008 4:08:01 GMT
Has any one built simplex in 4.75in gauge, and if so what mods were done.
peter
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Post by freddo on Jan 20, 2008 14:33:43 GMT
What a strange question Peter.
Divide all the measurements by 1.05263157894737 or thereabouts, and away you go!
Freddo
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Post by baggo on Jan 20, 2008 20:53:09 GMT
Hi Peter,
the easiest way to do it is to reduce the distance between the frames by 1/4" by reducing the length of the stretchers, axles etc and moving the centre lines of the cylinders and motion inwards by 1/8" per side. All other frame dimensions can remain as standard.
The width of the firebox will also have to be reduced by 1/4" of course to fit between the frames which will mean a reduction in grate area unless you reduce the width of the foundation ring (probably not a good idea as this would effect circulation) I am not sure how much of an effect that will have on the steaming qualities of the boiler. Some say that the Simplex boiler can be a bit of a shy steamer so any reduction in grate area may not help. You may be need to compensate by altering the blast nozzle diameter.
In the 1960's Martin Evans described a GWR 4500 class tank (Firefly) in 5" and 4-3/4" gauges and this was the way he did it.
John
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Post by chameleonrob on Jan 21, 2008 11:00:40 GMT
Some say that the Simplex boiler can be a bit of a shy steamer so any reduction in grate area may not help. if you use jim ewins calculations pageperso.aol.fr/jemodeng/index_frames.html?f=fs then you'll see that the simplex could be considered over cylindered so if it is a shy steamer then lining the cylinders may help. rob |
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Post by freddo on Jan 27, 2008 12:25:53 GMT
Baggo mentions other's opinions of the steaming qualities of a Simplex. I'm a complete novice to this hobby, but have sat behind quite a number pf Simplex's in Oz here, and have not as yet seen a "shy steamer".
Has baggo built any Simplex's? Maybe it was the coal - the driver whatever.
Although I say I'm an ME novice, I do prefer to speak from personal experience rather than passing on other's talk.... That's how rumours start.
Just my observations
Freddo.
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Post by baggo on Jan 27, 2008 13:20:59 GMT
I'll let you know when I've finished mine later this year  As Rob suggests above, the loco is over cylindered for the size of the boiler. John |
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Post by mutley on Jan 27, 2008 18:50:07 GMT
Umm , it doesnt seem to stop them steaming though the way they hammer round our club track when passenger pulling. its not unusual to see the safteys lifting.
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Post by baggo on Jan 27, 2008 20:42:13 GMT
The only reason I mentioned it was because that was what a couple of Simplex owners at our club had told me. It may well be down to other factors including their driving ability! I have actually driven one of the locos for a few laps and found no problem at all.
My concern was that reducing the grate width by 1/4" MAY have a detrimental effect on the steaming if the boiler is running near it's limit.
John
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Post by Shawki Shlemon on Jan 28, 2008 8:17:13 GMT
Simplex is free lance and therefore one is free to make changes, if the grate area is reduced by 1/4" compensate by increasing the length by 1/2" and that should if anything improve the steaming .
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Post by mutley on Jan 28, 2008 8:53:50 GMT
As standard Martin Evans spec'd the blast nozzel at 1/4". Try using 7/32" a few people I know with Simplex's reckon it works better. Point taken about the narrow grate John.
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