Derwent Slide Bars

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Derwent Slide Bars

This topic has 4 replies, 2 voices, and was last updated 2 September 2013 at 21:03 by Jeff Dayman.

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29 July 2013 at 17:28 #38771
JasonB
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29 July 2013 at 17:28 #125664
JasonB
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@jasonb
I see that a new drawing standard has been used in fig 13 page 153 of issue4461.

The cross section of the slide bars for Derwent is shown at twice full size BUT the dimensions have also been doubled, what should be 0.125" square slidebars are shown as 0.250" as is the 0.125" rebate on the sliders. The only correct one is the knuckle.

And just to make things harder to follow the pin has been drawn at twice length but the diameters are still at 1:1

J
2 September 2013 at 18:43 #128451
Jeff Dayman
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It looks like another new standard for sheetmetal cross sections has been applied to Derwent's tube and back plate drawings in ME 4461 pg 156 fig 15. The sectional views show the holes crosshatched and the rest of the section with no crosshatch! This is the exact opposite to any draughting standard I have ever seen. In addition, the flange edge behind the section should be shown but is missing. The cutout notch for the gas pipe is not shown in the section. No inside radius for the bends is shown.

I also note that on the backhead plate drawing there is no dimension in the X direction to the centre of the lower water gauge hole.

On the smokebox tube plate view in fig 16, a .125 dimension is given from the 1.232 dim on the left view to the centre of the .750 hole for the flue. When making the tube plate, there will be no physical reference and no way to pick up the 1.232 dim, which is the centre height of the flue hole on the firebox tube plate drawing. On the smokebox tube plate a dimension to the centre of the 2.375 dia from the centre of the .750 hole would be far more useful.

JD

Edited By Jeff Dayman on 02/09/2013 18:45:18
2 September 2013 at 19:05 #128453
JasonB
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There is also a lot of difference to the Smokebox Tubeplate shown in fig 16 and that in photo 18 where the two stay holes look a lot closer to the watertube hole

Jeff you missed off the use of perspective for the tubeplate girder stay.
2 September 2013 at 21:03 #128460
Jeff Dayman
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@jeffdayman43397
I didn't see the perspective, but did notice the artistically angled cuts. Maybe they are angled cuts to lighten this massive stay. (!?)

As to the holes differing in drawings to pics, it may be that the builder used that special migratory copper famed in song and story, and I believe the illustrator intended its' use. I say this because I also noticed that the sheetmetal thickness changes in the copper from the sides to the top of the crown sheet in the left view of fig.16. (This used to happen in the drawing office many years ago when careless junior draughtsmen wouldn't bother finding centres when manually drawing concentric arcs. Couldn't be that today……..>ahem<

This migratory copper is sometimes difficult to work with. I marked up a piece the other day, cut it, and damned if it hadn't shortened itself 1/32" from the time it was cut to when I went to solder it. I've also noticed a tendency for the air to turn blue with profanity after such migrations.

JD

Edited By Jeff Dayman on 02/09/2013 21:04:20
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