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Scratch-built Yeoman, ARC & BSC PTA Tipplers

ARC Yeoman BSC PTA 3D Modelling Resin Casting Steel Aggregate




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#1 lyneux

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Posted 14 February 2012 - 22:12

I've been a bit distracted from the JHAs recently!

For my model of Whatley, I need a variety of aggregate wagons and following on from a joint DEMU project to build an Axle-Motion bogie, I have been working on a kit of parts for the Redpath Dormand Long PTA Steel Tipplers.

I made the masters and then the moulds back in January. Since then, I have been busy casting parts for a rake of these wagons. To avoid excessive undercuts when casting these, I cast them in pieces:
  • Main wagon box
  • End panel with horizontal ribs
  • Underframe Ribs (3 types)
  • Buffered Headstock
  • Non-Buffered Headstock
I finally have enough bits to put one together (see photos below). The air distributer is from 51L and the air tank scratch build from a piece of styrene tube and sculpted filler for the ends (I still need to make a master and cast this as I can't find one of an appropriate pattern).

I'm able to put together inner wagons (two non-buffered headstocks) or outer wagons (one of each type of headstock). The outer wagons have 51L sprung Oleo buffers fitted (18 inch heads IIRC). The inner coupling will be a kadee fitted at prototype height via a hole cut in the headstock. My preferred coupling is the long shanked centre-set whisper coupler and there is just the right amount of room (5.5mm) between the frames to accept one so that the "whiskers" function without the need for a draft box.

If I ever get around to doing a Steel layout with a working tippler, I'm hoping that I'll be able to fit a rotary Sergeant coupling in place of the kadee (fingers crossed that there is enough room).

In addition, there are a couple of bits that I am awaiting etches for: the roughly diamond-shaped lattice-like surround to the auto-coupler, lamp brackets and ladder. I've drawn these up as a custom etch (just need to send it off to PPD).

The example below is of one of the better castings. Note the air bubbles along the top edge of the box (easily filled and sanded but a pain non the less). Also, I haven't got round to cutting out the holes in the left hand bogie side frame yet (just a push-fit at the moment).

IMG_4355_cropped.jpg
IMG_4357_cropped.jpg

An inner wagon awaiting the addition of under-frame components:
IMG_4361_cropped.jpg

The masters for the headstocks, under-frame ribs and end panels
IMG_4362_cropped.JPG

Mould of the main box. This is as per Jon Hall's design (using a sacrificial thin layer of 10 thou styrene sheet to reduce the number of bubbles) but modified to include lego registration holes to ensure a nice "true" fit.
IMG_4363_cropped.jpg

A casting "straight from the mould" with the scrap layer visible.
IMG_4364_cropped.jpg

Lots of pieces! There's got to be a couple more wagons worth in this lot but still a way to go before I can do a full rake.
IMG_4365_cropped.jpg
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#2 ess1uk

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Posted 18 March 2012 - 18:28

like the look of that

#3 lyneux

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Posted 03 April 2012 - 13:00

I've finally used up all my EasyFlo 60 resin. A 1KG pack of resin has cast enough copies for 9 good wagons with 5 "seconds" (too many bubbles to be easily usable) and a couple of total failures (not enough resin!). I now use about 40-50ml of resin for one casting of the box with a further 10ml used in three separate moulds to make a bogie side frame, some of the under-frame ribs, the "end plate" (with horizontal ribs) and the buffer-beams (I need 4 sets of these castings for one wagon).

Using talc in the mould helps enormously to get a good cast of the box. After realising this, I have been able to make a good copy every time. The under frame components are the most fiddly parts to cast as they have lots of nooks and cranes for bubbles to get stuck. Again, talcing the mould before casting almost alleviates the bubble problem completely.

I've been working on a 3D model of the under-frame components as I've come to the conclusion that given the time to mould and de-mould and then clean these up with a scalpel, I'm better off spending £4 on a Frosted Ultra Detail print (my time is valuable too)!

I'll post some photos of the kit of parts and the production line on my workbench at the moment.

Finally, does anyone know why I have ended up with about 50-100ml of "Part A" resin left? I've always poured part A first and then added part B to the measuring cup to the appropriate level. The only thing I can think of is that the parts mix to a different volume ( a bit like alcohol and water). If so, perhaps I've been adding too much part A to each mixed batch of resin?
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#4 lyneux

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Posted 04 April 2012 - 12:22

Here is a pic of the production line as of yesterday evening (with the spare resin coincidentally in the background).

I'm doing them in mini-batches of 3. Last night I fitted the end ribs and buffer beams to the remaining wagons, filled some air bubbles around the top rail of the boxes and made some extra beams that are only present on the buffered "outer" wagons (you can see these on the left hand wagon on either side of the buffer beam). I also made some air tanks by adding filler to each end of the appropriate diameter styrene tube and then turning in a drill with wet and dry to get a rounded end.

I've only fitted the under frame horizontal ribs to the first 3 wagons. Will probably get enough 3-D printed for the other wagons as I value my sanity. I've also filled the under frame with liquid lead and sealed with Klear on these three.

Now I need to get on with the bogies and getting the etches done for the ladders and fretwork around the auto-coupler.

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#5 owentherail

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Posted 04 April 2012 - 14:17

Fantastic, ill enjoy following this thread, well done, .........owen

#6 Penrhos1920

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Posted 04 April 2012 - 18:37

30 of these were on my to do list and will be if I continue modelling. So far I've got enough bits for 5 wagons. Are you going to make the underframe available on Shapeways? What buffers are you using?

#7 lyneux

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Posted 05 April 2012 - 10:43

Hello Penrhos!

I'm using 51L 18 inch sprung Oleos. Making the under frame components available on Shapeways is a distinct possibility. At the moment, I'm scratch building the air-tanks and using the 51L brake distributer (with the moulded mounting point chopped off and re-mounted). I'll post a render of the 3D CAD.

Guy

#8 The Fatadder

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Posted 06 April 2012 - 06:27

How did you cope with the transfers?
When i built my 2 sets of 5 based on the Lima 'box' with all the ribs/ends/underframes corrected I found that the fox yeomsn transfers were designed to fit over the incorrect Lima ribs meaning they were not straight over the scale ones.

Think in the end I cut up the transfer and applied one letter at a time (which along with a deep dislike of the horrid cast metal bogies I was fitting resulted in only finishing one wagon)
One day I when I feel like a bit of modern modelling I may even finish them.....

#9 lyneux

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Posted 06 April 2012 - 08:35

Rich,

I haven't applied the transfers yet, but I'm dreading it for the reason you outlined above! Most of these will be ARC wagons so hopefully less lettering to have to chop up!

I just realised that I haven't posted a good pic of the Axle Motion bogie on here (you'll have to go to the DEMU forum for the moment). I've done the bogies as 3D models that I've then resin cast myself. They look pretty good and you can even read the axle motion lettering in relief. 3D printing really is amazing (I feel like a fraud using it!). Maybe I'll send you some so you can finish off your rake and distract you from the kettles! ;)



#10 Pugsley

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Posted 06 April 2012 - 10:39

3D printing really is amazing (I feel like a fraud using it!).

Don't - you're just using the tools available to you to their best advantage.

#11 jonhall

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Posted 06 April 2012 - 19:12

I dont like the colour of that resin - it looks like its really close to the end of it life, and has probably been re-packaged by the outfit that you bought it from. once it goes yelow/orange, there has been crystal growth in the resin - if you get a crystal of unreacted monomer in the part, it will 'weep' monomer out, and may ruin the paintwork.

J

#12 lyneux

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Posted 06 April 2012 - 20:12

Thanks Jon, that could explain the problems I've had with the paintwork not drying completely?

I tried cleaning up the next two bodies a bit more carefully than the one that I painted. I'm going to see how the paint sticks to these and if there are problems then maybe it's time to bin the lot and start again with fresh stuff (from Nottcutts this time).

To be honest I had really bad problems getting this resin from mbfg and would not recommend them at all. First, they held on to my money without shipping anything for ages and then when I called them, they claimed that they had just had a batch arrive in stock and that it would be sent out that day. I then had a load of problem getting the package delivered that I attribute to royal mail being rubbish in London near to Christmas (rather than a problem with mbfg). Given what you are telling me about the yellowing, I'm beginning to trust mbfg less and less.

Let's see how the next paint job goes...

#13 jonhall

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Posted 10 April 2012 - 09:20

Thanks Jon, that could explain the problems I've had with the paintwork not drying completely?


Yes, possibly - its not that your paintwork isn't drying, its the resin underneath isn't 'set' - I never found a way round that - I never use the last inch in the bottom of th bottle for that reason, its also possible that if you are making rather small 'batches' of resin that it isn't being mixed well enough so that there is unreacted monomer around.

J
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#14 lyneux

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Posted 10 April 2012 - 11:30

if you are making rather small 'batches' of resin that it isn't being mixed well enough so that there is unreacted monomer around.


In the case of the wagon bodies I'm mixing 40 to 50ml at a time and mixing with a flat wooden coffee stirrer. It could just be that the one that I painted wasn't cleaned up enough before painting.

I'll have another stab at painting them later on tonight.

#15 lyneux

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Posted 22 May 2012 - 20:24

Having painted three wagons now, it looks like the weeping is present on nearly all castings I've made (both of the wagon body and smaller pieces such as the side frames too). The resin castings only appear to weep (are very sticky) once primer is applied to them. The weeping is not all that apparent until you apply paint (Tamiya Fine Surface Primer). I'm tempted to think it is bad resin (as per Jon's advice), junk everything I've done up until now and start again.

Just to see if I could rescue the work done already and following tips on the internet (http://www.therpf.co...ng-resin-18055/), I tried baking a couple of the bogies in the oven on a low temperature (80 degrees) for 15 minutes but this just made the weeping worse. In fact after removing from the oven the whole bogie was covered in sticky paint and they sat in a little "pool" of clear sticky fluid. Urgh!

The only good thing about this experience is that when hot, the side frames ping off from the etch which means I can at least re-use Colin Craig's etched side frames! ;D

Here is one of Colin's excellent etched bogie frames that I made up and fitted (prior to painting and discovering the nasty weeping problem):

IMG_0200_cropped.jpg

I've also sent off my first etch to PPD tonight. It contains the fretwork and ladders for the PTA as well as the hopper doors for the JHA. Very excited to see what comes back.

Canvas_9_lores.jpg
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#16 Mike G

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Posted 22 May 2012 - 20:39

Fabulous stuff! Really sorry to read of the resin problem, they look excellent. Where did you get the info on making the masters from, really interesting stuff.

#17 lyneux

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Posted 22 May 2012 - 21:12

Hi Mike

Where did you get the info on making the masters from, really interesting stuff.


Do you mean the prototype information? I used what I could from the diagram book and photographs supplied to me by Jon Hall (many thanks Jon!). I then drew my own set of 2D drawings before embarking on cutting styrene. Here is an example of the drawing (it's still a work in progress really):

PTA_v0.4.jpg
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#18 lyneux

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Posted 29 July 2012 - 21:43

High time for an update!

I've been getting on very well with the F31 resin and have cast enough pieces for more than 10 wagons now. Crucially, I have more or less completed 3 test wagons to a reasonable level of satisfaction. One was a non-weeping one from the first batch of resin (don't know why it doesn't weep but I'm not complaining), the second uses parts cast for me by Jon Hall using "good" EasyFlo 60 and the third one uses F31. Photo attached below taken on my phone.

PaintedAndTransfered.jpg

The wagons still need couplings fitting, hand wheels and various parts picking out in different coloured paint such as the axle boxes in yellow. Still, I am very pleased with them so far and they convey the impression I wanted.

I now need to get a bit better on my mould efficiency. Certain parts need lots of copies so I'm going to use some of the better castings to make further copies which means I can do less pours (time consuming) to get more bits! This is notably the buffer beams, wagon ends and bogie mounting plates. From the new mould, a single pour should give me enough pieces for 2 wagons with options for an inner or outer wagon.

One last thing to note is that the Fox transfers are a little small on their ARC lettering. I reckon they are about 10% too small (judging from pictures). This is disappointing but I'm probably going to have to live with it for the moment as my motivation for getting custom transfers made isn't great right now (this project has been dragging on for ages).
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#19 lyneux

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Posted 29 July 2012 - 21:53

Inner and outer wagon with etched ladder and coupling fretwork added.

PaintedAndTransfered2.jpg
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#20 hidden-agenda

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Posted 04 August 2012 - 00:56

Fabulous work and the end result looks excellent. I am new to the site but have been reading it for a while and i was wondering if you still have the problem with weeping in the castings and left over part A of the resin.

#21 lyneux

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Posted 04 August 2012 - 17:28

i was wondering if you still have the problem with weeping in the castings and left over part A of the resin.


I've been using F31 resin from Alec Tiranti and getting on very well with it. I posted a couple of posts on another thread about F31's properties:

http://www.rmweb.co....ls/page__st__25

I have also got on very well with EasyFlo 60 acquired from Nottcutts. I suspect that the first batch of EasyFlo 60 that I bought from MBFG was bad in some way. It was casting slightly yellow castings when I first got it (compared to the white castings from the Nottcutt's EasyFlo 60) and had been re-packaged into their own brand packaging (so no original shelf life indicators on the packaging). All in all, I will steer clear of MBFG and acquire resin from either Tiranti or Notcutts in future.

I am now casting enough parts for two wagons worth on each set of pourings that I do. The only mould that I don't have enough for is for the bogies. It's a bit time consuming to make another one since it is a two part mould but I will get round to it at some point. In fact, I will try and make a mould that I can pour a whole wagon's worth of side frames in one go.

Edited by lyneux, 04 August 2012 - 17:28 .


#22 hidden-agenda

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Posted 04 August 2012 - 18:29

One problem you may have all ready realised is not to use anything timber to mix it with as i found it caused air bubbles, all in all you have got an excellent end result the wagons look very very impressive and the bogies look first class did you make the side frames or can they be got commercially?

#23 rob D2

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Posted 04 August 2012 - 19:20

Wow, those are brilliant mate. If the layout features this level of attention to detail ....I think you are well beyond modelling, this is minature engineering !

#24 lyneux

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Posted 05 August 2012 - 08:51

Thanks for the positive comments! I really must put this to bed and get on with the rest of the layout. The last niggling point is that it looks like the Fox transfers are under scale by about 10% so I guess I'll need to draw up some artwork and get some better ones made.

did you make the side frames or can they be got commercially?


The side frames originated as a collaborative DEMU project between myself and Colin Craig. They were 3D printed and then resin cast. Colin Craig has provided the etched inner frame for them. Here is a render of the 3D model:

v0.1-top-view.jpg
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#25 Steadfast

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Posted 05 August 2012 - 09:14

Nice stuff Guy! It's seeing stuff like this that tempts me towards 4mm, only ever so slightly of course :locomotive: Is that a Yeoman JYA I spy in the background, too?
With regards to transfers, I've used a company called Red Firecracker for my stuff. He uses an ALPS printer, so can do white and opaque colours, and his prices are good. Kelvin's really helpful with any questions of queries about designing and printing the transfers http://www.redfirecr...er/Welcome.html. I draw them up in Photoshop then email them off to him. Drop me a PM if there's any more you want to know
Hope this helps!

jo








Also tagged with one or more of these keywords: ARC, Yeoman, BSC, PTA, 3D Modelling, Resin Casting, Steel, Aggregate

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