Dartmouth paused

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Paul Townsend
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Dartmouth paused

Postby Paul Townsend » Sun Sep 12, 2021 5:18 pm

Due to my recent health drama ( mentioned ad nauseam elsewhere ) nothing has moved since June :(
I stopped in the middle of an awkward job due to fainting, so need to finish that asap.

The offending track is mixed gauge bullhead rail a la BrookSmith with C&L half chairs glued in. All was tested, wired ,ballasted and painted in 2015.
I attach a sort of Templot .pdf to show my level of masochism and failed in the attempt to highlight the offending common crossing. It is one near the centre diamond.

broad_gauge_dartmout_pages_2021_09_12_1735_54.pdf


The problem was not apparent on waggon tests in 2015 for either gauge or loco tests with two different BG 0-6-0 s, A GWR pannier and Robin's Adams radial in NG.
When I attempted transit by two different BG 2-4-0T I got consistent derailments. My diagnosis was that the fine point was in longtitudinal positional error by some 0.3mm. I had to use butchery to extract the crossing and its assorted bits of rail so sadly it is now in two parts and needs reassembling as an extended Vee. Tricky ! Then I must solder it back into place WITHOUT the Vee separating again.

Yes I do know about step soldering but doubt if I will get away with it. In such an exceptional situation I am contemplating brazing the Vee. Never having done that, it is a tooling and skillset challenge......
When I eventually get it back into position, it will be a further challenge to reinstate cosmetic half-chairs, repaint and patch up the ballast etc. Heigh Ho
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LesGros
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Re: Dartmouth paused

Postby LesGros » Sun Sep 12, 2021 8:23 pm

Paul,
Instead of brazing, you could try soldering the vee with a higher temp solder, then using a lower temp solder for the formation installation on the layout.

As you know, it is a method recommended for multi-component brass work.

Cheery,
LesG

The man who never made a mistake
never made anything useful

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Paul Townsend
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Re: Dartmouth paused

Postby Paul Townsend » Sun Sep 12, 2021 11:23 pm

LesGros wrote:Paul,
Instead of brazing, you could try soldering the vee with a higher temp solder, then using a lower temp solder for the formation installation on the layout.

As you know, it is a method recommended for multi-component brass work.

Cheery,

As I said, I am aware of step soldering but am unsure if I will get enough discrimination in this crowded space. For the final re-fitting I would not use a solder with very low MP or the awkward joint would be too weak. 145 would be my choice. For the pre-assembly , I would use 188.
The issue then is to get into an overcrowded space with the exact amount of heat to fix the sub-assembly without either again disassembling the two parts or worse, unsoldering adjacent parts.

One builds complex formations like this from centre outwards. I have to repair it in the wrong order, I.e. last part in is in the middle.
I will provide a picture tomorrow, oh, later today!

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LesGros
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Re: Dartmouth paused

Postby LesGros » Mon Sep 13, 2021 9:29 am

Hi Paul,
The fine points of a resistance soldering tweezer could provide a solution to getting heat precisely where you need it. If we lived closer, you could try mine. (I live near Nairn, by the Moray Firth)

The link below shows the nature of the beast.
https://www.americanbeautytools.com/Res ... dering/100

The entire kit would be a bit pricey for a one-off job, but there was a discussion about resistance tweezers a few years ago, so perhaps someone nearby to you has one you could borrow.

I look forward to seeing your images, and the adopted solution for holding the bits in place to guard against movement due to overheating.
LesG

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never made anything useful

Terry Bendall
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Re: Dartmouth paused

Postby Terry Bendall » Mon Sep 13, 2021 11:16 am

Paul Townsend wrote:I am contemplating brazing the Vee. Never having done that, it is a tooling and skillset challenge......


The alternative is to silver solder the vees. Brazing and silver soldering are similar processes. Silver solder is an alloy of silver and copper, with some zinc added for the lower melting point types as follows

Grade silver copper zinc Approx melting point

Hard 80 20 778 - 825 degrees C
Medium 75 20 5 750 - 775 degrees C
Easy 50 30 20 690 - 740 degrees C

The easy grade is sometimes known as easy-flow solder. A flux, traditionally borax, which is ground to a powder and mixed with water is needed.

Brazing uses an alloy of copper and zinc, traditionally called brazing spelter and again different grades with different melting points are available -between about 890 degrees C and 940 degrees C. Both processes can be used on ferrous metals (those containing iron) and non ferrous metals but usually silver solder is used on non ferrous metals and would be the best process for soldering rail for crossing vees. It is possible to buy miniature brazing torches that would be suitable for the heating. Again flux is needed which can be borax although modern propriety fluxes are usually more effective.

The main problem would be holding the rails in accurate alignment whilst doing the soldering and to do this something would be needed that would withstand the heat.

Paul Townsend wrote:Then I must solder it back into place WITHOUT the Vee separating again.


One possibility is to solder some scrap rail or pieces of brass offcuts across the tops of the rails. It does of course introduce more heating but it may work. I have not done this for the assembly of complex formations but it was useful earlier in the year when I wanted to transfer something a bit complicated from the building board to the layout.

Another technique is to solder thin pieces of brass or nickel silver under the vee in the gaps where the sleepers will come, either by soft soldering or by silver soldering. This then gives more holding points and hopefully some of them will remain in place when further work is done.

Terry Bendall

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Paul Townsend
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Re: Dartmouth paused

Postby Paul Townsend » Mon Sep 13, 2021 1:55 pm

LesGros wrote:Hi Paul,
The fine points of a resistance soldering tweezer could provide a solution to getting heat precisely where you need it. If we lived closer, you could try mine. (I live near Nairn, by the Moray Firth)

The link below shows the nature of the beast.
https://www.americanbeautytools.com/Res ... dering/100

The entire kit would be a bit pricey for a one-off job, but there was a discussion about resistance tweezers a few years ago, so perhaps someone nearby to you has one you could borrow.

I look forward to seeing your images, and the adopted solution for holding the bits in place to guard against movement due to overheating.


Ta for that, however I do have those tweezers and used them a great deal to build the baulk road track at Dartmouth.
Sure the precision positioning of heat will help but does nowt to overcome the differential temperature required.

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Paul Townsend
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Re: Dartmouth paused

Postby Paul Townsend » Mon Sep 13, 2021 1:58 pm

Thanks Terry for your several bits of advice, one of which may solve my problem.....lots of things to try......must summon the courage first :D

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Paul Townsend
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Re: Dartmouth paused

Postby Paul Townsend » Mon Sep 13, 2021 2:25 pm

Here are promised piccies.
Wide angle one shows my level of masochism, close up shows the offending two bits of rail just placed in position, no joinings yet.
Once joined the two tails will be shortened c 0.3 mm enabling a longtitudinal slither.

20210913_091414_001.jpg


20210913_091923.jpg


Brian Harrap's magic wand would help but his zany common crossing technique may solve my problem!

For the unitiated, he folds the rail through say 350 degrees to form the fine point.....cunning chap.
Oh yes, he does a bit of filing too.....
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andrewnummelin
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Re: Dartmouth paused

Postby andrewnummelin » Tue Sep 14, 2021 7:54 am

Might a totally different approach be worth considering?
- Fit droppers (nearly as thick as the rail width) under the little bits of rail;
- drill holes through baseboard for droppers;
- check that the rail can be inserted where needed and clamped in place (modified hair grips possibly)
- glue the rail in place (epoxy in the holes for the droppers should secure everything).
Consider little bits of epoxy putty between rails (spacing blocks, bits of cast chairs...) as extra security.

Good luck!
Regards,

Andrew Nummelin

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Winander
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Re: Dartmouth paused

Postby Winander » Tue Sep 14, 2021 2:09 pm

Paul Townsend wrote:Brian Harrap's magic wand would help but his zany common crossing technique may solve my problem!

For the unitiated, he folds the rail through say 350 degrees to form the fine point.....cunning chap.
Oh yes, he does a bit of filing too.....


As detailed here https://www.rmweb.co.uk/community/index.php?/topic/37678-handbuilt-track/page/2/

It still relies on a soldered joint as the bend is completely filed off.

As an aside, the method Brian uses to measure the crossing angle is Centre Line Measure and I believe Templot defaults to Right Angle Measure. The two systems are close but not exactly the same and as you are replacing a component in a complicated formation, you may wish to check which you used originally.
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Paul Townsend
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Re: Dartmouth paused

Postby Paul Townsend » Tue Sep 14, 2021 2:20 pm

Winander wrote:
Paul Townsend wrote:Brian Harrap's magic wand would help but his zany common crossing technique may solve my problem!

For the unitiated, he folds the rail through say 350 degrees to form the fine point.....cunning chap.
Oh yes, he does a bit of filing too.....


As detailed here https://www.rmweb.co.uk/community/index.php?/topic/37678-handbuilt-track/page/2/

It still relies on a soldered joint as the bend is completely filed off.


Good point. Not having used his technique I was expecting to revisit B rian's destructions.

Yes to need to check crossing angle precision. My cunning plan is to fix the bits onto a proper Templot printout.

Its perhaps worth mentioning that Templot for mixed gauge is quite challenging so I leave a lot of bits off of the Track plot and add eg check rails ad hoc with gauges.

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Paul Townsend
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Re: Dartmouth paused

Postby Paul Townsend » Tue Sep 14, 2021 2:22 pm

Winander wrote:
Paul Townsend wrote:Brian Harrap's magic wand would help but his zany common crossing technique may solve my problem!

For the unitiated, he folds the rail through say 350 degrees to form the fine point.....cunning chap.
Oh yes, he does a bit of filing too.....


As detailed here https://www.rmweb.co.uk/community/index.php?/topic/37678-handbuilt-track/page/2/

It still relies on a soldered joint as the bend is completely filed off.

As an aside, the method Brian uses to measure the crossing angle is Centre Line Measure and I believe Templot defaults to Right Angle Measure. The two systems are close but not exactly the same and as you are replacing a component in a complicated formation, you may wish to check which you used originally.


Now that is a REALLY good idea, TVM

I think its worth adopting as the nasties all seem to go away.

I will report back asap

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Re: Dartmouth paused

Postby Terry Bendall » Tue Sep 14, 2021 8:08 pm

Paul Townsend wrote:For the unitiated, he folds the rail through say 350 degrees to form the fine point.....cunning chap.
Oh yes, he does a bit of filing too.....


I had to make some turnouts at the start of the year and used Brian's technique for the crossing vees. Very easy to do and speeds up the process no end. Also easier to make the vee to the correct angle since it can be adjusted whilst the vee is in all one piece.

Terry Bendall


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