I was thinking the other day that there needs to be a few more threads on here about what people are making, either for themselves or as production runs. A bit like Keith's Bubblecars. Then I thought perhaps I should put up or shut up, so here goes.
Tar Tank
This is all John Candy's fault because he suggested it! John and I have been thinking how to keep costs down and introduce a small range of kits which are entry level, but dimensionally correct and with no less detail than more up-market kits.
John's idea was that by designing a wagon kit in a series of simple parts it would be possible to cast them in resin at home and save the cost of professional casting, which is typically about a third the total cost of a kit. John made Plastikard patterns for a wagon underframe - the skeleton we call it - which he cast himself and then taught me to cast. Because the casting doesn't include a floor this needs to include the prototypical diagonal framework in order to give strength. The casting is devoid of all detail except little dimples for buffers, couplings and W irons, all of which are then drilled through by hand.
The diagonal framing prevents to use of my usual pre-bent W iron units, so we needed another way of keeping them in the right place in all three planes. The solution is the noted dimples in the solebars which are drilled through and 6BA countersunk screws and nuts used. The final location is done by eye on a flat surface, and the nuts then nipped up tight. I also assemble with Araldite to make quite sure they can't more. Home-cast resin overlays are then stuck to the solebars and headstocks to cover the screw heads and provide the detail. Since many post-Grouping railways used 16ft 6in wagons built to RCH designs, the same skeleton can be used with different overlays for detail correct for each company.
We agreed that the first wagon would be a tar tank. One reason for this is that back in 1907 they used the same 16ft 6in underframe, so the kit could use the standard fittings I already have with no need for the cost of new patterns, moulds and castings. Having said that, post-1923 patterns are on the way. My job was to make the tank. We thought about fabricating a pattern in Plastikard but there are a lot of rivets which would all need to be marked out individually. I considered 3D printing but although that would be fine for the main structure, small detail like rivets don't come out well with that process. Since some etched details like straps, corner plates and end stanchions would be needed anyway, I decided to etch the whole tank too. That still left some decisions to make: should the final product have an etched tank, or would that be a pattern for resin casting?
Well, if each kit had an etched tank, the builder would have to fold it up and either punch all those rivets, or add them through holes provided, and we thought that was too much to ask. So, the etching was the pattern, but the question of rivets remained. In my opinion half-etched rivets are horrid because they either look like discs with flat tops, or they are far too small. If they were half-etched from the back, then we were concerned that after punching those long rows of closely-spaced rivets the sheet would kink and it would be hard to fold to shape. Incidentally, the rivets are so close together that a special dolly would be needed anyway, with a flat on one or two sides. Therefore the decision was made, the artwork changed and the rivets were etched holes, into which small actual rivets would be added.
In the next instalment I'll tell you what happened when the etchings came back and post some photographs......
Mike
Here are John's pictures of the main chassis parts.
Mike
looks good Mike.... Ill start a thread later in the week on the OaK foster yeoman hoppers I am making....
looking very good Mike, like the idea of a chassis for the Bachmann opens as well.
At last - an underframe - this is going to be useful Mike.
Can you expand on the W irons, it sounds like you will make individual W irons available to bolt to the inside face of the solebar - is that the plan ?
Richard
Hi Richard.
Yes. In the early days I had separate W irons and crossbar, but some were not keen on soldering steel, so I changed to a pre-folded single unit. That was fine, but location of the brake V hanger required some care by the builder, so for some kits I tried pairs of W irons for each side including V hangers, and using the same crossmembers.
Because the framing gets in the way, these use the same original single W irons in which I had included a couple of holes "just in case they might come in useful one day". I have to make sure the back face of the solebar is dead square and both the distance apart and wheelbase are not absolutely positive as in the other methods, but with care it works very well.
To make it really easy for people I'm minded to offer underframes RTR - but since I only have one actually finished at the moment, that's a bit premature!
Brakes are an issue - more on that later ....
Mike
P.S. Great to see you back.
The etchings were done by Precision Photofabrication Developments Limited (PPD) this time and came back quickly. All the brackets, straps, owners' plates etc came out well - better than expected in fact. Making representations of cast iron plates in this way is not so easy as some may assume because for every thou the acid etches down into the surface of the sheet, it also etches sideways. For that reason, many etched nameplates, numberplates etc are made in very thin material. I wanted to put the whole lot on one sheet to keep the cost down, which meant 18thou brass and all the lettering thickened up so that after etching it would be reduced by 9 thou either side and come out to the correct width again. Even that is not easy because if you take a letter like a "B", thickening all the lines enough for 18thou brass means that the two holes in the letter disappear altogether. In short, its a compromise, but I've done a large number of plates now and it all worked well.
Back to the tank itself. It folded up easily, but as the rivets were originally going to be half-etched from the back, I had forgotten to enlarge them sufficiently to take the actual rivets. Therefore every hole had to be drilled out by hand, and then the burrs removed with a larger drill, and then 1/32in brass rivets inserted and glued in place. At the joins, the long rivets on one plane interfered with those in the second and third planes, so many rivets had to be cut and filed to length before being inserted - a time-consuming job. To make it worse, I had expected the rows of rivets at joints to be staggered as that would be easier to peen them over in real life, but they are actually aligned, meaning that the vertical and horizontal rivets exactly get in each other's way inside.
After several days of this - actually several weeks, but full time equivalent of several days - I've now completed all the rivets on the top face, both sides except the bottom row (all of which can be full length rivets, so quick), and just the ends remain. I totted that up today and I've "only" got 450 rivets still to do! How depressing! Drill - countersink - cut - file - insert - glue. Drill - countersink - cut - file - insert - glue. Drill - counter.... zzzzzzzzzz!
Mike
Here are some of the plates.
And here are the first rivets inserted. The size of rivets is an art, rather than a science, as the ratio of head to shank varies between sizes and manufacturers. I selected these as the size of each head and the gap between heads looked to be about right compared with photos of the real ones.
Mike
By the way, the half-etched strip across the tank is not prototypical but a) helps locate the strap in the right place; b) reduced the apparent thickness of the strap to something closer to scale. I guess it could have been 1/4in plate at the most, which is less than 10thou on the model and would easily kink. Model strap is actually 18thou, so if half is hidden it should look about right.
Mike
Here's John's resin casting for the filler.
Mike
Back on the job and another 97 rivets done yesterday. I've just realised that the lower parts of the ends are completely hidden by the baulks of timber, so I could miss out those rivets.
And just as I was thinking I never want to see another rivet again John Candy suggested doing a circular petrol tank too. Argh!!!! (only joking John)
Mike
Mike,
Well, I searched high-and-low for any evidence that a "flush" finish tank (whether of rivetted or welded construction) existed prior to the grouping but have drawn a blank.
If anyone knows of any such wagons, we shall be pleased to hear from you!
Photographs suggest that the cylindrical tanks had fewer (larger) rivets at wider spacing than the rectangular tanks (perhaps a consequence of the greater inherent strength of circular objects). I think it only fair that it be my turn to deal with the rivets next time around!
At present I am focused on the RCH dia. 98 from 1911 for a 14 ton tank on an 18ft underframe (the "skeleton" for which I am about to commence work).
This will produce both "cradle" and "saddle" mounted designs and were used for both classes "A" and "B" traffic, so there will be plenty of scope for variety in detailing (both Shell and BP, in particular, owned a lot of these and several photos exist of them liveried for the familiar "Mex Fuel Oil" traffic).
John.
Blimey! Will you be including the lateral and longitudinal tie bars?
By the way, I would like detailed articles describing the preparatory and production work involved in these models please for the G3 Newsletter. Deadline for the 1st article - approx 1,000 words + hi res images - is 15 November.
ho ho
Ian
Ian,
The tanks will be fully detailed with a "proper" open underframe pattern and are expected to be surprisingly affordable....that is the aim of the new range of wagons being designed in conjunction with Mike and based around the "skeletal" underframe concept for which I am producing patterns for 18ft and 17ft 6ins over headstock patterns (in addition to the 16ft 6ins pattern already produced for the tar tank and RCH 1923 coal wagons).
The versatility of the design revolves around the supply of a range of different solebar and headstock overlays to permit the easy (and low cost) construction of a wide range of vehicles while not compromising on correct detail/authenticity.
I will liaise with Mike on producing articles for publication.
Currently, another batch of projects revolves around a "special" order from a G3S member for a complete train of fish vans (comprising 5 different diagrams of GNR/GCR/LNER Standard origin), so there will be plenty of material for future editions of the G3S Newsletter!
John.
Hi Mr.Editor,
I'm sure we can get an article done by then. Longitudinal bars will be brass rod. Etchings include fold up supports for these. Will describe those when the first model is assembled - and that means after the tank has been cast (and the rivets finished!).
On a possible circular tank, the pattern won't be as bad because the only a few rivets will interfere with each other on the inside. But that's a long, long way off yet so please don't ask when that will be ready.
Mike
Mike,
Would you be able to supply etchings for the tank (and plates etc) as an alternative to a resin casting?
Those rivets have aroused my curiosity, though I haven't used them on things with wheels yet. Can you tell us what size (shank diameter) and material you are using?
I have to confess that I actually enjoy riveting. It demands a few special tools and considerable concentration at times, but is almost relaxing. That's apart from the occasional interlude of blood-curdling profanity after the wrong length of rivet has just been bucked in a difficult corner.
Andrew
I'm using standard 1/32 brass domed-headed rivets. I'm not actually rivetting them over but just glueing them in because this is a pattern for casting. I had intended to solder them, but glueing is easier and they don't have to last long.
Jamie - you could have a set of etchings, but don't forget that you'll need to buy c1500 rivets and insert them all.
Mike
Mike, Yes please.
When the rivets have been finished I intend to thicken the sides and top with resin, making them 5 or 6mm thick and then the fun will begin trying to cast it. Remember all this work is in order to reduce the cost of the final product - in this case a kit. I intend to paint the tank before casting to help fill any crevices beneath the rivet heads. Even so I am sure the rubber will get behind some and pull them out when the pattern is removed from the mould, but hopefully only a small number which can probably be removed from the mould and all will be well. Too much undercut beneath rivet heads could make them tear the mould, so fingers crossed!
In order to keep future costs down and also to retain control, I've decided to invest in my own vacuum resin casting equipment. A local fellow G3S member with considerable experience of this has guided me on what is needed, but rather than pay over £2,500 for a ready made system I intend to get much of it made by local engineering firms, or myself. I'll report on progress as it happens (he says optimistically!)
Mike
Depending on how you can support the other side, a carpenter's nail set and a hit from a light hammer works very well for settling the rivet head on the base material. I've done thousands like that! In some cases it also helps to paint the surface first and then lightly wire brush the area when the riveting is finished.
Andrew
Should have added to the above: Never clean up riveted areas with steel wool. Some of it will get trapped under the rivet heads, which you will discover just after the first coat of paint, no matter how carefully you think you cleaned it.
Andrew
Thanks Andrew, worth considering next time. If I can face a next time!
Mike
Mike
The tar tank should cast well, I am working on some large casts this weekend, I'll post some pictures.
Regards
Keith
Other work, some of which is modelling(!), has slowed work on the tar tank, but in the mean time here's the new vacuum tank I've had made so that I can cast it in resin when finished. I think its big enough!
I thought I may as well have a tank large enough for any casting I'm likely to need, but the down side is that it needs a big pump in order to evacuate it quickly, before the resin sets. The tank is 460mm dia by 300mm high internal and I should be ready to use it within the month - I hope.
Mike
Hi Mike
Very nice vac chamber, how thick is the flat bottom (and top)?
With that area and atm pressure being 14.5 psi, a big pump may well distort the flat bits.
Presumably the topface will be a bit of acrylic sheet, how will you seal it?
Richard
Richard,
Indeed, people (including me in the past!) under-estimate the pressures. The sides are 3mm, with an additional 3mm band around the top. The base is 6mm and the top will be 25mm clear acrylic sheet (perspex). I've copied the dimensions from a commercial product costing rather more than I could afford. The seal is a rubber L section made specially for the job and is one of the most expensive bits of the whole setup.
I just need one hose and the acrylic sheet, and then I'll switch it on and stand back!
Mike
As the 25mm prespex lid arrived this week I assembled all the bits today and tested the new pump but it seemed to pump away for ages with no movement of the gauge. Dejected, I turned it all off, checked the connections were tight and started again.
It pulled the chamber down to 22in/hg in one minute, and will go further if I needed it and could wait long enough. Other people have talked about wanting 10in/hg for de-gassing resin, so hopefully that willl work OK. Turning the pump off and closing the valves it will hold that vacuum for long enough for me to get bored and open the taps to atmosphere again. And there were no hissing sounds!
Now I need to complete that tar tank pattern and seek advice on mould making from my mentor.
Meanwhile, as I'm a modeller rather than a model engineer, I need to get back to actually making parts, rather than just making tools.
Mike
If the pump does not work Mike then try piping it up to a Dyson.
I was shocked to see its more than a year since I posted on this thread.
After greasing and tightening all the connections I managed to get a good vacuum. The gauge shows close to a perfect vacuum (I think a perfect vacuum is impossible?) and it works well. I've now cast many hundreds of bits, but am still learning about how best to make moulds, where to feed, where to put vents, which way up etc. I'm using a fairly soft rubber which flexes away from deep detail to get the parts out, but can flex when you don't want it to under the weight of the resin.
When I vac resin it expands to about twice its normal volume, so you also need a large catch tank at the top of the mould, and consequently a larger and more expensive mould.
Now that's all sorted out I am back working on the tar tank pattern. Working with Superglue and a magnifying glass - all 3in from my nose, upset me a bit last year, so I stopped. Yes, I probably should wear a mask (I do for casting resin!) but in small doses its OK.
So, will post an update on the tar tank body soon....
Mike
Excellent news Mike. An article for The Newsletter looms ever closer
Now get a move on ...
Ian
Just a reminder to those thinking "what on earth is he droning on about?" - this thread was started because detailed step-by-step posts on members' projects appear on other forums and it would be nice to see a few here, so I started one. Its not a lecture, but warts and all report as it develops.
The rivets are completed! The problem was that at the corners the real rivets were not staggered, but in line, meaning over-long model rivets could not be used on both faces of the corner. the first row were put in easily enough and glued, and every one (many hundreds) in the adjacent rows had to be cut short - less than 1mm - and glued in from the outside.
They are 1/32 rivets by the way.
Anyway, the plan now is to clean up with a glassfibre brush today, replace any rivets which have fallen off, give the outside a quick spray of primer to seal them in and help to fill any little gaps beneath their heads where rubber for the mould could get a hold and pull them out.
THEN, we start on the inside which is rather rough at present - to say the least! I need to make a bung for the filler hole and then pour (probably resin) inside, top, sides and ends, to thicken them sufficiently so this can be used as a pattern for casting in resin.
THEN we have the fun of making the complex (for me) mould.
Target is to complete all this before the AGM. I know I said that least year ....
Mike
Looking forward to seeing it Mike , will have to console my self with a L.N.W.R. open for X mas .
John
Progress with the tar tank at long last. The first resin tanks have arrived from CMA, so I'm assembling the various parts which surround the tank, prior to fitting it. Its a complicated assembly job, but then its a complicated wagon compared to simple opens.
Mike
Re-reading this thread I see I missed out a whole section. The whole intention was to cast this tank myself to save cost, but ....
After riveting the tank I had to thicken the etched sides to cover the rivets inside and make it suitable for casting. I poured some resin into the top of the tank and to my surprise there was slight shrinkage - enough to bow the sides inwards just slightly. At this point panic set in but I was due to visit CMA anyway, and showed it to them. They said they could sort that out and cast them, which they did. Nice job. Thickness means heavy and lots of resin, and that in turn means cost which is a disappointment, but at least the job is done and it will last.
I still have a lot to learn about resin casting, but I'm getting there. Now wondering about a circular tank and determined to cast that at home!
Mike
Almost there!
that looks very nice. I'm already on your waiting list for one, have you thought about lettering?. My vote would be Smith and Forrest (like the one at Didcot), I'd be happy with anything pre 1914.
Geoff,
"No" is the honest answer to that! Several of the photos taken by wagon builders when new, show no lettering at all - just a cast iron plate on the solebar. I suspect they quickly became very dirty, so they didn't bother with expensive lettering. I've etched three alternative owners' plates.
The one I'm doing myself is photographed as pale grey with all ironwork picked out black, but no lettering. In fact, even the cast owners' plates are just grey all over with letters not picked out. In spite of the photographic evidence, I'm tempted to do this one plain black all over.
Just to be clear, I had test tank castings. The fit is proven, so now I'll order the batch, so will be a few weeks yet.
Mike
I've looked online but been unable to find an answer- does anyone know how these wagons were loaded and unlaced?
So far as I know they were loaded via a flexible pipe and the tar was warm. It was unloaded via a big pipe in the bottom.
From memory there were heated pipes at unloading stations where the tar was steam heated prior to unloading - i.e. connected up to the train of wagons whilst they sat there. I think?
Not sure whether your "unlaced" was a typo, but the tank was not removed from the wagon.
Mike
I seem to remember seeing cylindrical tar tanks in Norwich in the early 70's (when on student placement there); they appeared to have a pair of internal flues heated by gas jet. I will try to find out more!
Ian the Gauge '3' Pirate
Gas lances inserted into "flame tubes" were used from the late 1940s (in cylindrical tanks) for melting bitumen. I have photos of these and the tanks have flat or flattish (not domed) ends.
Rectangular tanks (where fitted with heating) were fitted with steam coils connected to a steam supply at the discharge facility.
Early wagons (like those represented by the RCH 101 Flexikit model) had neither heating coils nor insulation fitted (the bottom discharge valves are not usually visible in photos. since were not of the "side discharge" type which protrude below the solebar on later wagons) and I presume they would have been used for journeys, during which the tar remained warm enough to be pumped out on arrival at its destination or (for longer journeys) a steam heating coil was inserted through the manhole to reheat the tar.
I did read (during research for the Flexikit) a comprehensive article on tar handling methods between gasworks and end-users but cannot now remember where I found it.
Some types of tar had other chemicals mixed with it to improve flow when cold and some non-heated (cylindrical) tar tanks were built as late as BR days.
John.
John,
I seem to remember that because the tanks were rectangular the tar was shipped solid i.e. it was allowed to cool as on a long journey so would be solid at destination. Being a rectangular tank the solidified tar would not slosh around like a liquid would, which tended to be in cylindrical tanks so it was safer for tar to travel this way. The tar was heated, I think by steam, at the delivery point & discharged on the underside.
This I seem to remember from decades ago but could have been lost in the mists of time.
Correct me if I'm wrong.
Dave
454
Thanks for all the info, will be in touch to order a couple soon Mike. Have a perfect place to model a loading/ unloading siding, plus they look really interesting wagons.