Doddys HaupWerkstatte - My build thread

[John Candy]

Gentlemen, please, can we draw a line under this and agree to disagree. 

There appears to be a range of views, particularly in the "commercial" world of G3, as to how the scale is to be referenced/defined.....the example of "Garden Rail" insisting on 1:25 (even though I explained to the author of the article, Mark Thatcher, that 1:26 was the scale used to construct the "Sentinel" locos) was to fit in with their inflexible method of "tagging" articles by scale (they use 1:25 for G3 since it is used by them for "G-scale" articles).

John

[Spitfire2865]

We model 2 1/2" to the 4'8 1/2". I expect the society to reflect this ammendment in their next website update. /s

UPDATE: Trevor made contact through moderation channels and apologises, having made this comment "tongue in cheek" and, on reflection, having realised it was probably unhelpful to have done so.
JC

[MikeWilliams]

Well, I assumed the "criticism" of Doddy was intended to be humrous, and will continue to believe that.

However, I would like to be pedantic over:

... measuring and cutting, material shrinkage (resin and plastics) all contrive to introduce errors....

I would simply like to point out that some metals expand more than plastics or resins.  I have a resin van with brass door runners and in the blazing heat a few years ago the brass expanded and buckled - the resin stayed put.

Mike

[Peaky 556]

Personally I’m a keen supporter of using the “correct” scale factor of 22.6, and it rather irks me to see 22.5 on the Society banner.  Maybe it’s a mistake of course, and it’s not the only one on those banners.  In support of the people who put them together some years ago, I know as a former design draughtsman just how easy it is to painstakingly put together a drawing title or note, only to find it mis-spelt as a result of the slow and laborious process of creating it.  What I cannot excuse however is the lack of peer review before production of something so important as a society promotion banner.

Anyhow, we digress.  The reason for 22.6 was succinctly made by IanT further up this page, and this is why we ought to be quoting the magic 22.6 number in our technical standards.  Whilst we need not mandate this scale, it is only right and proper that we acknowledge and promote its use as the technically correct number.  The measurements of 17/32” or 13.5mm to the foot need to be placed in context as approximate conversions.

I think that’s all I have to say on the matter, so, happy modelling!
Tim

[John Candy]

Mike,

The shrinkage to which I referred was in respect of the mould-making process and resin-casting process itself, where the standard advice is to allow for possible shrinkage of up to 1 percent when producing the patterns.
I have also observed that after extended time (a few years) some silicone moulds can themselves shrink (seems to be a consequence of leeching of the "oily" component in the mix). Certain brands of silicone and resin seem to suffer more than others.

As an apparent example of the shrinkage problem, I was tackled by Peter Korzelius at the 2018 AGM who had bought one of the Flexikit LMS "steel" van bodies from you with the intention of mounting it on one of his steel underframes. He said the dimensions of sides and ends weren't matching/consistent and he had difficulty assembling it. I explained that I had supplied the moulds and each side and end would have been cast from the same mould and the only explanations I could offer were that either the resin was from a different batch/mix or there was a delay in casting the second side/end, during which the mould had shrunk.

Regarding whitemetal/pewter casting, I read somewhere that, when cooling, the castings expand (not contract as I would have assumed) although I have never encountered any significant/observable evidence of that. I guess the expansion is akin to water/ice and the molten metal taking on a crystalline structure.

I remember you telling me about the problem with the LSWR van door at the time it was introduced (a good few years ago now)! I subsequently altered my original pattern/mould to cater for a plastic card runner fixed to the resin with brass rivets.

Regards,
John.

[MikeWilliams]

Well John, I am amazed because those castings were done within the space of a few days, and odd that he never mention it to me.  Think they were a gift as a trial actually, rather than "bought".

But, without wishing to prolong the 1:22.6 debate further(!) what I really meant was that its not only resin models which expand and contract - metal and wood do too, at least as much.

Mike

[John Candy]

odd that he never mention it to me.  Think they were a gift as a trial actually, rather than "bought".

Mike,
I guess that, being a gift, he didn't like to appear ungrateful.
I saw the body (which had been assembled around a plywood box) on his table at the show and (out of curiosity, since it looked to be from my original patterns) asked from whence it had come. He said from you and then became critical of the quality. At that point I explained that I had made the patterns and moulds and that my own examples fitted perfectly and that it would be odd if the sides and ends were dimensionally different since they would have been cast in the the same moulds.
I don't suppose you can now remember the time of year or temperature at which the parts were cast but I do wonder whether a great variation in ambient temperature and/or humidity could have been the cause.
Regards,
John.

[MikeWilliams]

No, sorry.  I don't remember.  It was about five years ago!

[Doddy]

If you are going to post things as "facts" then let's try to stick to the actual scale ratios.

I see where you are coming from now, many thanks for pointing this out to me, I apologise to you.
Doddy

[IanT]

No problem Doddy - I didn't set out to upset you and I'm sorry if I did so.

There are not too many places (online) that people can find out about G3 and this is one of them - so it's important we try to keep the key facts both simple and consistent here for anyone new to our gauge/scale.

I'll be looking at that webpage and will endeavour to make it clearer.

Regards,

IanT

[cabbage]

Having been brought up in a totally Metric environment... I will admit that it is easier for me to think of G3 as a gauge of 6.35cm rather than 2.5".  I have always worked from direct Metric reduction by dividing everything by 22.6 or previously 19.1 Although the model people look best at 24th scale(?) As fas as possible I have tried to make my models to the correct scale, but if there are a suitable set of plans at 22.5 -I will unhesitatingly use them!!!

Most of my drawing are taken from "00" scale A4 spiral bound books. These are I have to assume are as accurate as possible. Some of the plans I have will produce a good model but not a scale model. The Chriss Barron; Peak and 2-nol are a case in point. Both are too short. But both are the correct length not to "side swipe" another wagon if taken on 3.3m radius curves.

I have built a Golwe locomotive in SM32 which was over 118cm long but would corner a std SM32 setcurve with ease. This worked only because of the sheer bloody mindedness of the builder to produce a working Golwe articulated. The same thing happened when I built the Tasmanian J Hagans. Only by very close scale modelling did both systems work.

Absolute scale fidelity does have its place and without the drawings from Eurfort for the Hagans nothing would have worked. However I believe it is better to have a well designed working model than an exact shelf piece.

As to how the Hagans system works - it uses articulation via levers with moving fulcrums, the principle of a Golwe makes sense only after several shots of Polish Proof Spirit, but essentially it get longer the more it corners...

Regards

Ralph

[Spitfire2865]

I just draw all my drawings to the scale of 13.5mm/ft.
Or for imperial drawings in inches, multiply inches by 1.125 to get the mm I need.
No need to ever think about how best to round a fraction of a scale. Besides, even our true gauge scale has its own setbacks. One being the B2B and subsequent chassis width. No point drawing 1:1 if its not going to work anyway. Best not waste the energy and instead get it right first time!
Hell, my American required significant revisions as I was working off fully dimesioned drawings and completely forgot the chassis width needed narrowing, which changed the cylinders, footplate, cab sidesheets, frame crossmembers, pilot, and firebox just to name a few!

[Doddy]

Quite often Ralph leaves me in the dust with new ideas and topics, the Hagans and Golwé locomotives are no exception and appear to be in a league of their own.

Die Preußische T13, Bauart Hagans.




French Golwe locomotive for Ivory Coast railways.



Hagans Tasmanian J class







References:

• https://en.wikipedia.org/wiki/Golw%C3%A9_locomotive
• https://de.wikipedia.org/wiki/Maschinenfabrik_Christian_Hagans

[cabbage]

The main source of information I have are the actual book detailing the Tasmanian J and "Meyer and Meyer like articulated locomotives".

For those of a strong stomach could I recommend "The Self Site" as it is called. The pages on "unusual locomotives" and "the museam of retrotech" will provide stomach upsetting information...

Regards

Ralph

[Doddy]

Having used this software application for many years now, I have recently added the G3 ratio scale.

The software allows user configuration of different scales and makes the conversion from one scale to another possible, cross referencing the actual 1:1 dimensions in metric and imperial measures at the same time.