A Highland Miscellany

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Jol Wilkinson
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Re: A Highland Miscellany

Postby Jol Wilkinson » Wed Apr 08, 2015 5:06 pm

Hi Steve,

I think that there are quite a few design options that could make life easier, but need to be practical for a multi gauge, commercially viable kit. The biggest design compromises are usually driven by the need to accommodate three different gauges as well as the rigid versus compensation/springing options. Just designing for P4 is actually easier than dealing with the OO compromises.

I have tended to follow the same format with the eight different loco chassis I designed for John Redrup of LRM , separate frames with fold up "L" and "U" spacers to provide alignment and rigidity. Some with a straightforward compensation option built in, etc. especially where it helps "balance" the loco as with the 2-2-2 Lady of the Lake. Sprung bogies or working radial trucks are standard, partly because it suits modelling in P4 but also because they actually work better.

It is difficult to know what percentage are build as OO, EM or P4, which are rigid and which sprung/compensated. The majority of purchasers are probably interested in "layout" locos and aren't too interested in excessive hidden detail, so that is the path I followed.

It is all rather academic now as I have told JR that I have retired from designing kits, etc, although I don't think he heard me. There isn't much LNWR that isn't already available, while he has several MR, NER, GNR, etc. locos in various stages of development. I haven't built/finished a loco for myself in the twelve years since I started designing kits, so there is quite a backlog waiting for me to do.

Jol

essdee
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Re: A Highland Miscellany

Postby essdee » Thu Apr 09, 2015 4:04 pm

Thanks Jol,

Yes, the split of the 4mm school into three camps was unfortunate.

I hope you enjoy a long and happy retirement and the chance to attack your own kit-mountain now!

BW

Steve

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Mark Tatlow
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Re: A Highland Miscellany

Postby Mark Tatlow » Sun Apr 12, 2015 8:44 pm

With the basic chassis made, it is essential to fit the nuts to secure the body to the chassis as both of these will be concealed with later work. So a quick test fit looks like this and we can get onto the next bit, the coupling rods.
_DSC0361compress.JPG

As is not uncommon, these are made from a pair of layers of brass laminated together. You can see that the outer layer is half etched for much of its length, with the full depth only being present at the bosses. I have also sought to make it easier to build these by including them in a folding jig – the folding is underway in the bottom portion of the view. The logic of the jig, indeed the whole kit, is to make a really smoothly running chassis much easier to make. Modern CAD and computer operated phototool creation techniques by the etchers means that it is possible to easily draw and then etch such that each dimension is faithfully repeated on the product. Thus, it is possible to be confident that the wheelbase will be repeated exactly on each side of the frames and also on the coupling rods. However, this accuracy is completely lost if the user has to laminate the two parts together by hand; it is not possible to get them superimposed on each other exactly or repetitively so the spacings of the crankpin holes will change. The jig overcomes this as the fold line is so long that there can not be any twist as it folds, so the two parts will meet consistently and accurately.
_DSC0271compress.JPG

It is true that there remain two areas of variability. The first is that the degree of etching will not be exact on every occasion so the holes will be slightly bigger or smaller on each occasion. This can be easily overcome by making all critical holes a tiny bit too small and then opening the holes up with a ream (not a file, reams will open up a hole consistently). The second problem is that a fold is not always consistent on a fold line so the jig can protect against twisting but might not necessarily put the two laminates directly on top of each other. However, the important point is is that they will be correct horizontally, any error can only crop up vertically. Thus, when the crankpin whole is opened up, it is possible that it will move vertically slightly but this will not change the dimension between the holes so the critical dimensions should be retained perfectly.

The above is all true in theory but in practise there was an almighty cock up in my artwork; so I was deprived of finding out. A total case of designer error and when this is yourself, there is no one else to blame……………….
_DSC0276compress.JPG

………..I made one of the coupling rods no less than 8mm too long – doh! I have no idea how, but it needed chopping; so it was back to the old fashioned way of making coupling rods despite my high ideals! Fortunately, as they were laminated, it is possible to stagger the cut to make the splice – essentially the same technique as Alan Gibson’s variable length coupling rods. Anyway, after the cutting and splicing, I did get a sweetly running chassis and this is what it looks like. The unusually large wheels for a shunting loco are already making their presence felt!
Chassis 12compress.JPG

Chassis 13compress.JPG

The chassis is created around CSB’s; continuous springy beams. For those that are not familiar with CSB they are formed of a spring wire is anchored to the chassis at four points per side (for an 0-6-0) and at the centre of each hornblock. Thus each hornblock is supported on either side and can “bounce” on the spring. However, the clever thing about CSBs is that when a hornblock is depressed, not only does the spring wire flex a bit as suspension, but it also rocks on the anchors so the adjacent wheels push downwards a bit to equalise out some of the deflection. It produces a really smooth chassis and, if it is conceived at the design stage, I think is actually rather easier to both design and build than traditional compensation. This is a close up of a pair of hornblocks and a pair of the anchor points (the other is hiding behind the frame spacer on the right). Also worthy of note is the colour coding of the hornblocks; to enable them to be reinstated in the same hornguide each time. This is probably unnecessary with modern (and therefore consistent) hornblocks and the accuracy of the etching I have noted but old habits die hard!
Chassis 16compress.JPG
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Mark Tatlow

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Mark Tatlow
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Re: A Highland Miscellany

Postby Mark Tatlow » Sun Apr 12, 2015 8:49 pm

I have just remembered; there is another little innovation in these pictures..............

I have produced the coupling rods (and connecting rods) in true scale and fattened by 15%. This, and may other pregroup locos, had very slender coupling rods - so slender indeed that I am concerned as to their durability in use. Thus, I though I would give a choice of options to the user by offering both. The OO boys won't get the choice in their chassis!
Mark Tatlow

Winander
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Re: A Highland Miscellany

Postby Winander » Mon Apr 13, 2015 12:03 pm

Mark Tatlow wrote:I have produced the coupling rods (and connecting rods) in true scale and fattened by 15%. This, and may other pregroup locos, had very slender coupling rods - so slender indeed that I am concerned as to their durability in use.


I'm curious and since I'm planning my own pre-grouping efforts, where do you think the rods will fail?

regards
Richard

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Re: A Highland Miscellany

Postby andrewnummelin » Mon Apr 13, 2015 2:18 pm

Winander wrote:
Mark Tatlow wrote:I have produced the coupling rods (and connecting rods) in true scale and fattened by 15%. This, and may other pregroup locos, had very slender coupling rods - so slender indeed that I am concerned as to their durability in use.


I'm curious and since I'm planning my own pre-grouping efforts, where do you think the rods will fail?

regards


Me too as I have a project planned that should have very slender rods. Perhaps if there is a materials scientist on the forum we will get a definitive answer, but I have always believed that as items are scaled down they get relatively stronger. Just think of the wheels - would plastic spokes survive on a full size loco? The only area where I can imagine a problem is between the boss and rod if the hole has to be reamed out by much. (Just imagine simply scaling up that process!)
Regards,

Andrew Nummelin

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Mark Tatlow
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Re: A Highland Miscellany

Postby Mark Tatlow » Mon Apr 13, 2015 6:57 pm

My concern with the rods simply had to do with a fear of then bending, either through ill conceived handling or if something gets caught. It has happened to me in the past, although to be fair when I was starting out making chassis so they were rather less accurate than I can now manage.

The intention was to offer both, to allow the user the choice which way to go.
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A Highland Miscellany

Postby Mark Tatlow » Wed Apr 15, 2015 7:27 pm

Now that the much of the bulk of the above running plate work has been completed, the running plate valences can be fitted. As these are nearly always long and thin, they are prone to distortion in the kits I have built – so it is time for another jig!! This one holds the valences at numerous places to stop it flexing and to hold it straight.
_DSC0286compress.JPG

With this, it is a doddle to fit the valences in their correct place and solder them without distortion. I did find that the running plate flexed significantly at the end of the tanks; so the final version is going to include a pair of temporary stiffeners that fold down and stop this. This would be the moment when they are removed to allow the valancing to take their place.
_DSC0352compress.JPG

And onto the boiler. In a departure from normal practise, I am not including a flat etch to be rolled into a boiler – it is relatively difficult to get even a pre-rolled boiler into a neat tube without a visible seam and if you do not have a rolling machine it is effectively impossible to do so. In addition, where boilers have been half etched to create boiler bands I find that the half etched elements that remain are overly delicate. This was something that caught me out a while back when I drilled such and area to take handrail knobs and badly distorted the metal – this kit is still sitting in its box now and I am probably going to have to replace the boiler.

With these problems in mind, I simply used a piece of brass tube from Eileens; easier and much more durable and if I were sratch-building I would not even think of taking a different route. This did still leave the need for some rolled parts, to make the smokebox and I have sought to use another little trick here to make these easier to fit – some tags and eyes. The tags are strips of half etching that pass through the eyes and then tugged back. This can’t impart a curve into the metal but does allow the parts to be pulled tight and makes it easier to solder into place without much of lip. Mind you, they were a tad short and will be lengthened slightly in the production run.
Boiler 3 compress.jpg

A second additional laminate is then needed to form the outside of the smokebox and down onto the saddle.
_DSC0349compress.JPG

I did find another little error when it came to the front of the smokebox. Whilst the diameter for the front that I had drawn had allowed for the thickness of the two laminates, when you fit these there is also a layer of solder between them and whilst this ought not be that thick, it was just enough to make the fronts too small. In the production run, I will deliberately make this a tad too big as it is easy enough to file it back but much more difficult to add the missing metal (I didn’t, I just made a fresh one from sheet metal). The smokebox door is not mine, the door from the Lochgorm Models Loch is the right size judging by the photographs (note the drawing in the old man’s book has it being smaller but this does not match the photos, so I ignored it in this respect – sorry Dad!).

The downside of using tube as a boiler is that boiler bands need to be considered. I have provided these in the kit (again using the strap and eye technique). I chose to fit them on this kit although in practise I think any metal boiler band is too thick and would probably have done it with a transfer sheet if this was not a test build (done prior to painting, the thickness of the transfer is enough to show through the paint on what will be a single colour to the boiler).
Boiler 4compress.JPG

Only the top of the boiler is visible after the first ring and a bit, so can be cut away to leave lots of room for the motor, weighting and DCC chip. I may try and fit this with sound, so who can give a view on what it might have sounded like – a jinty is my favoured guess?
Mark Tatlow

David Knight
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Re: A Highland Miscellany

Postby David Knight » Wed Apr 15, 2015 8:01 pm

Mark,

You mention making some bits a "tad" larger. Would that be a metric tad or an Imperial tad? :lol:

Seriously though, this has been a fascinating thread to follow with some great ideas that I hope other kit designers follow.

Cheers,

David

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Mark Tatlow
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Re: A Highland Miscellany

Postby Mark Tatlow » Fri Apr 17, 2015 9:40 am

Next up is the finishing of the detailing of the cab. Common with many tank engines there were grilles over the rear windows. For these, I toyed with the idea of doing these as a single etch, a bit like the Mainly Trains one (and possibly others) but elected instead that the slight roundness of the bars needed to be captured, so this meant that brass rods were going to be required. If I had either etched small holes or soldered these on top of the cab etch, I felt that getting consistency of spacing was unlikely and that this would detract from the finished effect. Thus, it was time for a little jig.

This jig is simply a sheet of brass with holes for the wire at the appropriate spacings along with half etched lines arranged such that when the jig is folded over, the wire is trapped between them. This is what it looks like with the wire in and the jig folded over (along with a dab of solder to hold it all still):
Window grille 1compress.JPG
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You will note that in the picture above, I have trimmed the wire rods to a gentle curve to reflect the curve of the spectacle plate and in the picture below, this has been soldered on the ring around the window. The jig is then snipped off and the rods can be cut away. I found that by using a scalpel, it was possible to cut a nick in the rods and then the wire could be carefully lifts so that it snapped at the point of the nick. It was necessary to ensure that the rods were soldered well to the sides as if this joint failed it was then pretty difficult to get them soldered back down neatly; I will include a space jig in the production etch of the kit to give the user a second chance!
Window grille 2compress.JPG

There is also a beading around the cab side openings, a common feature on pre-grouping locomotives. This was relatively simple to fit, although I did make it a tad too fat deliberately to assist in the process – it can then be filled back to a thinner dimension and in the process any slight irregularities taken away in the filing. In this example the stanchions are probably a bit far away from the cab sheets, so there will be a slight adjustment on the final version.
numberplate cab compress.JPG
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Also worthy of note is the cabside number plate, which I am dead chuffed with. This is a cruel enlargement as the whole plate is only 6mm across and to clearly be able to read the text which is only 0.7mm high is pretty good I reckon!
numberplatecompress.JPG
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After finishing the cab detailing, it was time to add the boiler onto the tanks/running plate and she is beginning to look like the real thing, although perhaps looking a little naked due to the missing dome and chimney at present!
Combined 5compress.JPG

I have fitted a safety valve bonnet and safety valves from those intended for the Strath/Loch and available from Lochgorm Models. I also formed the front splashers, which I had tried to make easier by the use of some tabs and formers. These did assist in the assembly but I then found that they fouled with the wheels, as I had made the splashers true to scale and the tolerances did not allow for the tabs. I will have another think here and might come up with a jig, as splashers are sometimes a bit painful to fit.
Combined 1compress.JPG

And this is what she presently looks like; definitely beginning to look like the real thing (a reminder of which is below). For those of you that are coming to Scalefour North I will bring her along for you to have a look at. As we are now about up to date with her construction (you didn’t think I can build that quickly did you?!?!) and because I am away the whole of this weekend at Scalefour North, there will be a hiatus a bit before the next posting.
scrap tank.jpg
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dal-t
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Re: A Highland Miscellany

Postby dal-t » Sat Apr 18, 2015 7:57 am

Great idea for the coal grilles, Mark, I wish I'd seen that before I sweated over individual bars for my last 7mm build. But you've missed the 'bit' (sic) I've been waiting for - how did you get the soldering iron in to attach that bunker back plate?
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Re: A Highland Miscellany

Postby Mark Tatlow » Sun Apr 19, 2015 9:57 pm

dal-t wrote:Great idea for the coal grilles, Mark, I wish I'd seen that before I sweated over individual bars for my last 7mm build. But you've missed the 'bit' (sic) I've been waiting for - how did you get the soldering iron in to attach that bunker back plate?


The rear of the bunker was made a tad (metric or imperial, they are compatible!) bit too big, so that I could be confident that there was no chance of it being at all undersize. I then tinned both the inside of the sides and the cab bunker and just sweated them together.

The more serious issue would have been if I forgot to put the nut that the chassis is screwed onto. It would be impossible to get it in irrespectively.
Mark Tatlow

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Re: A Highland Miscellany

Postby dal-t » Tue Apr 21, 2015 4:04 pm

Thanks for the explanation, Mark, but I don't think that technique would work for me - I'm sure lots of other bits would fall off long before I'd get the bunker joints to 'take'. :( Perhaps I should try using a kitchen blowtorch, rather than the Sievert? :idea:
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Re: A Highland Miscellany

Postby Will L » Tue Apr 21, 2015 4:35 pm

Mark Tatlow wrote:The more serious issue would have been if I forgot to put the nut that the chassis is screwed onto. It would be impossible to get it in irrespectively.


For nuts like this which, as you say, would be very difficult to deal with they fall off once the body is complete, I like to have the hole the nut is soldered over no larger than the tapping size for the nut your using. Slightly under that for preference. Use a cocktail stick to hold the nut in place while you solder on the nut, then I tap back through the nut, any solder that has leaked in and the brass plate underneath. That way the tread includes the brass plate and much reduce the stresses you can put on the solder joint between nut and plate. I don't think I've ever had one come away since I've been doing that and my chassis generally have several as I also like to bolt down pick-up systems and such.

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Re: A Highland Miscellany

Postby DougN » Tue Apr 21, 2015 11:22 pm

Will I like that methodology.. I will use that on the next loco I will build! :thumb
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Jol Wilkinson
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Re: A Highland Miscellany

Postby Jol Wilkinson » Wed Apr 22, 2015 7:25 am

Alternatively the designer can provide a half etched hexagon the size of the nut to locate it.

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Mark Tatlow
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Re: A Highland Miscellany

Postby Mark Tatlow » Wed Apr 22, 2015 7:39 am

I can see the merit of Will's suggestion as a little bit of the stress of the friction of the screw going in is taken by the etch, not the solder joint to the nut. I am not convinced that Jol's suggestion addresses this?

I have inserted little fold up ears on some sections of the chassis that fold out of the fret to clasp the side of the nut (and locate it). I didn't put any on the running plate and given that both of these nuts will be impossible to get in the future if there is an issue, I think it is another one for my list of corrections!
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Andy W
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Re: A Highland Miscellany

Postby Andy W » Wed Apr 22, 2015 8:33 am

Another solution is to drop the chassis spacer lower so that the top face isn't flush with the top of the chassis sides. Then the nut can go underneath the cab.
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Jol Wilkinson
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Re: A Highland Miscellany

Postby Jol Wilkinson » Wed Apr 22, 2015 9:25 am

A nut only has to be stopped from turning while the screw is being inserted, pressure when tight pulls it against the surface it sits on and friction stops it from coming undone. So far I have found that the "etched nut pocket" seems to work well enough for our applications.

On the subject of mounting body to chassis I think that a slightly loose or flexible arrangement is best. Bolting a slightly flexible chassis to a more rigid body can distort the chassis and create problems although it is probably less of a problem with sprung/compensated chassis than with rigid ones. I now favour having a bolt at one end and use the coupling hook through the body and chassis spacer at the other. The hook arrangement is very slightly loose compared to a bolt fixing and so prevents distortion.

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Re: A Highland Miscellany

Postby 45609 » Wed Apr 22, 2015 10:49 am

Some interesting thoughts and discussion on body to chassis attachment methods. Just to add another variation to the mix I have got into the habit of not trying to solder a nut (from my experience of kit, typically 8 or 10BA) to the upper surface of a running plate. Instead I always replace the nut with a much larger piece of rectangular brass or nickel silver soldered over the mounting hole. This is typically 0.5 to 1.0mm thick. I then mark out, drill through and tap to suit a mounting screw(s). The advantage I see in this is that there is much less risk of this plate moving due to adjacent soldering when build the remaining body work of the loco. In addition a further refinement I apply is to put two mounting screws in, equi-spaced either side of the longitudinal centre line, in place of one screw on the centre line. By doing this I avoid any potential fouling and upset of, primarily, the AJ coupling shank but it is also useful for missing things like brake gear pull rods etc....

Cheers....Morgan

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Mark Tatlow
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Re: A Highland Miscellany

Postby Mark Tatlow » Fri Jun 26, 2015 9:47 pm

The update on the Scrap Tank test build shows it looking like this:

Tank 1.JPG

The eagle eyed, and indeed even the slightly less than eagle eyed, amongst you will notice that this is not a whole lot different to the last update, just a few fittings have been installed – basically the ones I could glean off other things; the safety valves/bonnet and smoke box from Lochgorm Models and the clack valves from Alan Gibson (but much cut down as they are really much too big). I have not been able to fit any other castings because they don’t exist, so I have had to do some more work on these.

So it is back to the CAD machine to draw up a series of 3D masters; in the top view some piston rods/part of the cross head, rear sand boxes, clack valves (now the right size which is much much smaller) and some lubricator valves. The bottom view has some tank filler lids, front sandboxes and piston ends.

Masters 6.JPG
Masters 2.JPG

These have been printed for me by Alan Butler of Modulu who is a new entrant in the field of 3D printing and has a system/machine that can do really small parts very well indeed; definitely better than Shapeways. Alan is a railway modeller here and blogs here – https://oswestryworks.wordpress.com/category/modelu/ - well worth a look I suggest and if you are thinking of having some things printed then I would get in touch with him.

I did not get Alan to print the dome and the chimney, partly because I had my doubts that the print would do the fine lip of the metal where it meets the boiler but mostly because I just could not work out how to draw the damn thing! Instead, therefore I commission Jeremy Suter to make these for me:

Chimney 2.JPG

……..and very fine the look too!

So, these are the masters all sorted and they will shortly be sent of for casting. I will be using lost wax again, as I much prefer this to white metal; although I do accept that the better white metal casters do do a grand job.
Last edited by Mark Tatlow on Sat Jun 27, 2015 8:51 pm, edited 1 time in total.
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Will L
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Re: A Highland Miscellany

Postby Will L » Fri Jun 26, 2015 10:57 pm

Mark Tatlow wrote:.. Alan is a railway modeller here and blogs here – well worth a look I suggest and if you are thinking of having some things printed then I would get in touch with him..


Were you planning to put a link in here?

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Re: A Highland Miscellany

Postby David B » Sat Jun 27, 2015 8:00 am

Alan Buttler can be contacted at info@modelu3d.co.uk. His website is just one page as he has been very busy setting the business up. See: http://www.modelu3d.co.uk

Alan was at Scalefour North and has been booked to be at Scaleforum in September.

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Re: A Highland Miscellany

Postby billbedford » Sat Jun 27, 2015 11:26 am

Mark Tatlow wrote:I did not get Alan to print the dome and the chimney, partly because I had my doubts that the print would do the fine lip of the metal where it meets the boiler but mostly because I just could not work out how to draw the damn thing!


In the spirit of blatant Cut-My-Own-Throat marketing I've put a new video onto my dropbox which shows how to form the flare.
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Mark Tatlow
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Re: A Highland Miscellany

Postby Mark Tatlow » Sat Jun 27, 2015 8:55 pm

Sorry, I did mean to put in a link but it seemed to fail. The longhand link is here: https://oswestryworks.wordpress.com/category/modelu/. There is a bit more on this than on his business site presently.

Thanks Bill, I did not manage to get to grips with it previously. Presently I am away from WIFI, so I will look at this another day. I do, however, still remain concerned wiht regard to the thinness of the flange if the chimney/dome is to be seperate from the boiler. 3 inch scale thick flanges is one of my pet hates in white metal chimney/domes!
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