Derwent main frame

[Eric CoxParticipant @ericcox50497]

Main frames ME4455, p663.

The drawing for the main frames shows a line of dimensions running along the bottom. What does the 0.687" dimension on the extreme right refer to.

Where is the pivot point for the 33 degree angle and how far from the edge are the two holes lying on the 33 degree plane.

[Eric CoxParticipant @ericcox50497]

[Eric CoxParticipant @ericcox50497]

bump

[Sub MandrelParticipant @submandrel]

Crikey, I've gone grey waiting for the digital version to load and then navigate to the page. It was quicker to go upstairs and get the mag!

And the answer is… I haven't a clue!

Actually I suspect the line was originally alogned with the holes in the end of the frame, but has accidentally been shifted and recalibrated its distance – a hazard that applies to some CAD stuff, as it's possible to create dimension lines that are aligned with guides or even nothing instead of the feature they are meant to reference..

Neil

[Diane CarneyModerator @dianecarney30678]

Dick Allan has kindly replied thus :-

The .687 is an obvious error and should read .093 and taken to the forward end of the frame as calculated by subtracting the bottom line of dimensions from the overall 8.469 length. The two holes at the rear are not very critical as they are for fixing the struts to support the footplate. The pivot point is .840 vertical from the top corner of the frame. By comparison with the 5 holes at the back make the first .125 from the edge, and the second, as shown, a further .188 away. Easier still, leave them out until you come to fix the footplate.

Diane

[JasonBModerator @jasonb]

Posted by Diane Carney on 02/05/2013 21:52:18:

Dick Allan has kindly replied thus :-

The .687 is an obvious error and should read .093

I think you will find that it's 1.093"

J

[Diane CarneyModerator @dianecarney30678]

Correct Jason.

Dick corrected it early this morning. It is indeed 1.093.

Diane

[Martin KyteParticipant @martinkyte99762]

Could someone tell me the center coordinates for the r0.583 radius that is drawn hanging in space on the back of the main frames please. That or the vertical distance of the top of the buffer beam to the top of the frames.

Thanks in advance.

Martin

[JasonBModerator @jasonb]

The extended length of the arrow does not help but I would say horizontally it is in line with the end of the frame and 0.583"above the top of the 0.625" end. You can locat ethe bottom of the 0.625 end by swinging the 1.193 radius.

J

[Martin KyteParticipant @martinkyte99762]

So if the centers are concentric that gives (1.193-0.583) = 0.61 rather than 0.625 for the buffer end.

M

[Martin KyteParticipant @martinkyte99762]

Drawing it like that puts the top of the buffer beam above the top of the axle box cut outs which are shown as 0.625 below the top of the frames. Looks wrong to me.

M

[JasonBModerator @jasonb]

Did not say the centres are concentric, you can work out the centre position of the 1.193R with trig.

The base of the triangle is the 1.189" dimension, the hypotinuse the radius of the circle 1.193, the short side is the end of the frame which works out at 0.0095" above the line of the axle box cutouts.

This is what I come out with when using the drawing dimensions in Alibre, you should be able to see the three springing points of teh arcs highlighted and notice the one for the 0.583" is above the 1.193", click to enlarge.

Though my feeling is that the 1.193" radius is wrong as it pouts the front buffer lower than it looks or the illustrator has not plotted the positions correctly which is quite possible as the junction between th etwo small curves is not exactly flowing

 

Edited By JasonB on 03/12/2013 18:23:55

[JasonBModerator @jasonb]

Just played about with it a bit more based on the 0.840" Diane gave for the 33deg line so the corner must be a little more than this below the top of the frame, 0.875" is the next obvious size. I have plotted it over the one above and it does look more like the printed drawing but really need the o.875" confirming as it could be plotted up or down from that.

 

The two large dotted circles are sprung from each end of the 1.193" curve, where they meet is the centre of the curve

Edited By JasonB on 03/12/2013 18:58:42

[Diane CarneyModerator @dianecarney30678]

I have asked Dick Allan to hop on and help you out.

Diane

[Martin KyteParticipant @martinkyte99762]

Sounds like a plan. Thanks Diane.

Martin

[Dick AllanParticipant @dickallan56872]

I am delighted to have given so much amusement to you all in worling out what the back end of Derwent's main frames should look like! Martin Kyte is right, I should have given dimensions for the buffer beam (actually the drag beam) and these are 0.842" from the top line of the frame to the top of the beam and 0.470" from the bottom of the horns to the bottom of the beam. That done the exact shape of the curves is not very critical – for my own Derwent I set them out by eye! Neverthe less I am full of admiration for the display of mathematical wizardry.

While I am at it, several of you noticed the errors in positioning the water tender axle boxes (Fig 25, ME4469). Of course it is blindingly obvious the something is wrong and, no, it is not an optical illusion as one contributor wondered! This is what happened. Using Draftsight (CAD programme) when drawing in multiple objects of the same design one designs only the first and then ' copy/paste as a block/ paste as a block etc for as many as required, placing them only roughly in place. The objects are then moved into acurate positions. I did this for the pair on the righthand side of the drawing when an interruption took me away and I forgot to finish the job. Anybody building the model will find it obvious where the axle boxes have to go as they have to fit into the limited spaces in the under frame. I was surprised that the plan was redrawn for ME without this being noticed!

I will be pleased to meet any of you who may be attending the Sandown Park exhibition where I will be exhibiting a gauge 3 model of the Crampton 'Liverpool'.

Dick Allan

[JasonBModerator @jasonb]

Thanks Diane for chasing this up and Dick for comming back so quickly.

Martin I have drawn it out again with Dicks info and shown the dimensions to locate the centres of the three arcs

[Martin KyteParticipant @martinkyte99762]

Brillig. Thanks.

M

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