122 Dmu

Simon

Flying Squad
I took myself down the shed tonight to try a few more casts.

As is often the case, it seems to me, it was a bit of a struggle to achieve the good results of the first cast, in fact the quality of none of this evening's casts were as good as the first. That said, they are all useable with work, apart from perhaps one which I took out when too soft and which has a distorted roof profile, it is the middle cast in the back row with the windows mostly cut out, the first cast is to its left and the original solid cast from three years ago is the darker one on the right.

Paricast 016.jpg

Looking on the brighter side, I used spray release wax on the core and inner mould and it all comes apart much more easily because of this.

The buffer moulds are problematic, air entrapment in a very deep mould but ye olde worlde coach springs are highly useable with a minimum of repair etc, this one has a bubble defect in its middle, easily fillable.

Paricast 019.jpg

Going back to the 122 cab, the parts which are hardest to get to cast are the front frames around the marker lights, I think these may need to be replaced with fabrications.

All looking quite DMU ish though:)

Simon
 

JimG

Western Thunderer
Why does the first shot remind me of the terracotta army. :):):) A few thousand more to make maybe. :)

A really good job.

Jim.
 

Neil

Western Thunderer
I took myself down the shed tonight to try a few more casts.

As is often the case, it seems to me, it was a bit of a struggle to achieve the good results of the first cast, in fact the quality of none of this evening's casts were as good as the first. ....

I experience similarly inconsistent results but usually it's the first cast that's a bit iffy, followed by a run of good ones. At some point I usually manage a duff one or two before getting back into my stride. On a long run of casts (I'm close to forty for the Deutz) I'll get a few of these fluctuations. The Deutz has nine components and I find that the good and bad spells for each of these parts don't coincide. Goodness knows what's going on but I am comforted that I'm not alone in generating the odd less than satisfactory casting.
 

Simon

Flying Squad
I agree that it is all a bit random, I nipped down this morning and tried another cast but with the added "wheeze" of dusting the mould with talcum powder first, which I have found helpful for assisting in picking up detail in the past.

I have left this cast in the mould and will take it out tonight by which time it will be good and hard.

Bogie sideframes and finessing cab plug moulds apart, I have got out the plan and am contemplating cutting out some large pieces of Plastikard for an exercise in windows, plus thinking about how to attach cab ends to a main structure, and where to cut/attach side to end and how I might build this up.

Current thoughts tending towards sub frame cum chassis built up from scrap (ie code 200) rail with floor etc built on to it, the roof is defo going to beremoveable for doing interiors in due course.

If Geoff Kent and Colin Parks can get the results they do in 4mm this should be a piece of cake:p

Simon
 

Simon

Flying Squad
Well I'm happy to report that this morning's cast has formed perfectly in terms of details etc.

I'm now cutting this and the first cast about with a view to making two fully useable ends to build into a "production" model. This currently involves my small hard point woodwork saw, chisels, knives and and a huge amount of mess.

This leaves me with two further ends with less well defined details that can be used and my slightly mis-formed reject, plus the original "paperweight".

Apart from possibly finessing the plug mould, which I'm likely to do out of technical curiosity, (thinking here about other cab ends that might be cast using this sort of method) I think that's it for casting at the moment.

Right, back out to the shed......

Simon
 

Neil

Western Thunderer
I agree that it is all a bit random, I nipped down this morning and tried another cast but with the added "wheeze" of dusting the mould with talcum powder first, which I have found helpful for assisting in picking up detail in the past.

I have left this cast in the mould and will take it out tonight by which time it will be good and hard. .....

That's interesting; I always dust with talc, I'm convinced that particularly with the tiny stuff I do, it is vital to minimise air bubbles in the finished cast. I'm also surprised that it takes so long for your resin to set. I've found that the 25minutes Sylmasta suggest is too short, but an hour is ample for the cast to go hard enough not to distort when being de-moulded.
 

Simon

Flying Squad
You are quite right Neil, the whole day business was related to having to go somewhere else during the day, the resin would have fully hardened in much less time as you report.

I think the talc works by reducing the surface tension of the resin, thus enabling it to better "flow" into bolt heads, rivets etc. One thing that amazes me is how well the resin flows into thin sections, such as the rain strip on this cast and the triangular strengthening plates on the lowfit solebar.

I still haven't made it back down to the shed - time for kip now I think!

Simon
 

Simon

Flying Squad
Two ends more or less prepped, sides cut back more at the guards end as there is a window placed quite close to the cab end. Here's one end with "revised thickness" window pillars

Planned 002.jpg

And both cab ends placed in position on the plan, Plastikard for the use of and a big ruler

Planned 001.jpg

There's a heck of a lot of space to fill with model:eek:

Simon
 

Simon

Flying Squad
Many thanks for the comments:thumbs:

In a spirit of nettle grasping, I have today had a bash at cutting out a side. After much looking at photographs and a bit of alteration of the drawing from Brian Golding's book, I have now got one side cut out. I have cleaned up the surface with some 600 grit wet and dry used wet on the draining board and I think the results are useable, next step side two...

Side1 010.jpgSide1 009.jpgSide1 007.jpg

Curving and glazing it is going to be interesting.

Simon
 

Steve Cook

Flying Squad
Bravo that man :)
It does look like its going to be fun, getting the curve over that distance and making room for glazing. Are you using Jenkinson's bible for ideas?
Steve
 

Simon

Flying Squad
Sort of, although saying that I can't find the copy I thought I had:rolleyes:

I can remember a lot of his wheezes though and I've got a few ideas of my own kicking about too, possibly involving epoxy filler, redundant rail and etch waste:confused:

Or possibly not:p

I've got to tackle side two first, dinner over, washing up done, cinnamon infusion infusing:cool:

Let's hit the Plastikard.....

Simon
 

Dan Randall

Western Thunderer
Nice work Simon. :thumbs: You must have a lot more patience than me - I would have taken the easy way out and had the sides laser cut or etched. Can't wait for the next instalment.:thumbs:


Regards

Dan
 

Simon

Flying Squad
Although the cutting out is tedious, it does actually yield quite a quick result - although I don't know how many more I'll ever build using this method:p

I have now completed the second side, the "kit" so far is as below.

Side1.jpg

I snapped the second side along a door hinge but have solvented it back together without messing up the finish.

The sides are quite delicate and I will be adding a degree of longitudinal strengthening along the bottom and top edges tomorrow while I consider the tumblehome options. I will also do further tidying of the window apertures but only when the structures are a bit more robust.

I need to start thinking about the chassis frames too in order to achieve a rigid structure asap.

Simon
 

Simon

Flying Squad
A very nice model in an even nicer setting

Of course, wearing my Reginald Nurd hat, I have to point out that what you have there is a the greater framed Pressed Steel variety...

Joking apart, the modifications required to my cast to make a 121 are very do-able but the framing around all of the windows is another matter, of course a bodger might just leave them off but they are such a feature of the prototype that something would need to be done I think.

At this point the laser cutting/etching or whatever route is probably the way to go, but that's not on the agenda at the mo as it is the Gloucester job that suits my timeframe and location. Although the 121 would look best in blue and is the type that I have personal nostalgia for - Severn Beach, Bridport, Greenford shuttle, Swindon late train etc

Choices, choices

Simon
 
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