Resistance Soldering

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David B
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Resistance Soldering

Postby David B » Sun Oct 26, 2008 10:08 am

I have recently bought a London Road Models RSU. I have made a label to show where to put the leads for the various power outputs, so have attached the graphic in case it is of use to anyone else. It is designed for an Avery L7161 label, 63.5mm x 46.6mm.

David B
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RSU Voltages.jpg
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Last edited by David B on Tue Feb 28, 2012 9:12 am, edited 1 time in total.

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Jim Summers
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Re: Resistance Soldering

Postby Jim Summers » Sun Oct 26, 2008 10:13 am

A really useful contribution. Thanks, Jim

nigelcliffe
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Re: Resistance Soldering

Postby nigelcliffe » Sun Oct 26, 2008 1:01 pm

The "missing" combination of "red1 + red3" gives approx 2.5v.
I don't know if you want to add this to the set, it wasn't documented on mine (numerous years old LRM unit), though I do find it a useful output level.


- Nigel

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Rod Cameron
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Re: Resistance Soldering

Postby Rod Cameron » Mon Oct 27, 2008 8:57 am

Thanks David - a useful replacement for my long-faded-away handwritten one! :)
Rod

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chrisf
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Re: Resistance Soldering

Postby chrisf » Thu Feb 15, 2018 6:03 am

As promised in the Scalefour News 206 thread, here is a reading list that I compiled ahead of the Chilterns Area Group RSU Day:

Resistance soldering: Iain Rice. A handy and readable overview of equipment and techniques in typical Rice style. MRJ 51

A review of the MMS RSU: John Hayes. MRJ 77

Resistance soldering - what, how, why and where: Jol Wilkinson. Perhaps the handiest guide to the subject. MRJ 74

Readers’ letters. Various issues of MRJ

A review of the GB Electronics Ltd RSU: John Hayes. MRJ 73

Workshop: The Road to Damascus: Tim Shackleton. A self-confessed Luddite describes his experience with a Graskop RSU. RailModel Digest 1

Offset resistance soldering: Mike Grey. Application to soldered trackmaking. MRJ 82

Resistance Soldering – how to do it: Raymond Walley. Raymond is a 7mm practitioner who uses a London Road RSU supplemented by a steel baseplate and rare earth magnets to fine effect. www.raymondwalley.com

Have Gas Will Travel: David Brandreth. David describes the building of a GWR Cordon gas tank using both resistance and conventional soldering techniques. Finescale Railway Modelling Review 1

As you will see, the list does not include David Brandreth's articles in Snooze 206 or 207 and it is high time that it was updated anyway. I would welcome any further suggestions for inclusion.

Chris

Enigma
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Re: Resistance Soldering

Postby Enigma » Thu Feb 15, 2018 4:19 pm

Thanks Chris, very useful.

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steve howe
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Re: Resistance Soldering

Postby steve howe » Thu Feb 15, 2018 9:56 pm

Can anyone advise where to get the carbon rod for the RSU probe? I have one that was given to me (provenance unknown) and am keen to try it out, but the collett needs a new probe.

Steve

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LesGros
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Re: Resistance Soldering

Postby LesGros » Thu Feb 15, 2018 10:31 pm

Steve,
Eileen's emporium have them.
LesG

The man who never made a mistake
never made anything useful

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David B
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Re: Resistance Soldering

Postby David B » Thu Feb 15, 2018 11:22 pm

steve howe wrote:Can anyone advise where to get the carbon rod for the RSU probe? I have one that was given to me (provenance unknown) and am keen to try it out, but the collett needs a new probe.

Steve

Also London Road Models and Hobby Holidays.

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Jol Wilkinson
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Re: Resistance Soldering

Postby Jol Wilkinson » Fri Feb 16, 2018 7:53 am

Steve,

check the diameter of the probe. LRM have always had 5mm, Exactoscale used 4mm. I don't know what the Graskop unit used.
Jol

Enigma
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Re: Resistance Soldering

Postby Enigma » Fri Feb 16, 2018 2:08 pm

Jol Wilkinson wrote:Steve,

check the diameter of the probe. LRM have always had 5mm, Exactoscale used 4mm. I don't know what the Graskop unit used.
Jol

I bought a length from Hobby Holidays last year and it is to small to fit my LR probe. Luckily I still had the original that came with the set. Next time I see Phil I will have to check that he stocks the 5mm size.

I believe they may be a 'standard' material used for spark eroding or similar? Possibly available from specialist suppliers also.

But you may have to buy a mile's worth at a time!

shipbadger
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Re: Resistance Soldering

Postby shipbadger » Fri Feb 16, 2018 2:36 pm

When the MMS resistance unit was developed the electrodes were from the carbon arc unit that came with my arc welder. Subsequently a box of the electrodes was bought from a welding supplier. Eileen's still sell them in 4, 5 and 6mm diameter.

Tony Comber

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David Thorpe
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Re: Resistance Soldering

Postby David Thorpe » Fri Feb 16, 2018 3:58 pm

I've got one of the Swanage RSUs. The probes are a fraction under 4mm in diameter.

DT

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Paul Townsend
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Re: Resistance Soldering

Postby Paul Townsend » Sat Feb 17, 2018 12:22 pm

I have been using an RSU for donkey's years. It is in a home made box and used the transformer supplied by Bernard Weller ISTR, together with his steel plate and magnets....all pretty good. The weakness IMHO was the probe handle and collett, so I have been using an alternative from London Road.

I have used several makes of Cu plated carbon rods and cope OK usually.

However the recent thread has alerted me to the American Beauty range.
I would not buy their work staitons as I don't need another one and they are over-priced for hobby use.

The Cu plated stainless steel electrodes are definitely of interest and, because I have a long series of RSU jobs to do soon which have proved tricky the classic way, I am pondering a dosh-splash on the tweezer thingies and am awaiting quotes from USA and their sister UK Co.

Like someone above I have thought about a DiY tweezer but have come to the conclusion it would be hard to make well and I don't have time to develop that anyway.

Does anyone here have experience of either the electrodes or tweezers?

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LesGros
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Re: Resistance Soldering

Postby LesGros » Sat Feb 17, 2018 4:05 pm

Hi Paul,
I have one of the American Beauty tweezers. They have the dual virtue of being fine pointed; and that you can hold small parts together, under a little pressure, before zapping with the footswitch. :thumb

Also quite good for repairing separated rail dropper connections; dab a bit of liquid flux into the gap and straddle the joint with pressure from the tweezers prongs, zap-fizz, and the joint is re-established. :thumb

Les G
LesG

The man who never made a mistake
never made anything useful

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zebedeesknees
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Re: Resistance Soldering

Postby zebedeesknees » Sat Feb 17, 2018 4:58 pm

Not for the faint-hearted, but a pencil can be used for very fine work. 2B or preferably higher. I take about 6-10mm of the wood off the non-pointy end, and wrap the 'lead' - which isn't of course, it's a mixture of graphite and clay, the higher the B the less clay - with foil, and clip over that. The tip can be sharpened with a pencil sharpener! But I don't make it too sharp. Trial and success recommended, and eye protection.

Ted.

DougN
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Re: Resistance Soldering

Postby DougN » Sun Feb 18, 2018 1:49 am

Many moons ago a local modeller here in Melbourne manufactured RSU's for sale unfortunately Roger Howell passed away. He was a great exponent of RSU's and also had a pair of the American beauty tweezers. He would zap away happily.

I purchased a RSU from him but found the prob clumsy due to the lack of flexibility in the leads. Since this topic has been started and my aim of finishing a model a month this year the idea of using the RSU is starting to rise in my interest again. I have to finish some track work first and then I will have a go at a brass kits with the RSU again. I need to get some solder paste as I think my last jar went in the bin after going hard. As has been suggested it could have been revived! Oh well!
Doug
Still not doing enough modelling

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Paul Townsend
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Re: Resistance Soldering

Postby Paul Townsend » Sun Feb 18, 2018 7:56 am

zebedeesknees wrote:Not for the faint-hearted, but a pencil can be used for very fine work. 2B or preferably higher. I take about 6-10mm of the wood off the non-pointy end, and wrap the 'lead' - which isn't of course, it's a mixture of graphite and clay, the higher the B the less clay - with foil, and clip over that. The tip can be sharpened with a pencil sharpener! But I don't make it too sharp. Trial and success recommended, and eye protection.

Ted.

Great tip Ted.
Good to hear from you....it’s been a while

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Paul Townsend
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Re: Resistance Soldering

Postby Paul Townsend » Sun Feb 18, 2018 7:57 am

LesGros wrote:Hi Paul,
I have one of the American Beauty tweezers. They have the dual virtue of being fine pointed; and that you can hold small parts together, under a little pressure, before zapping with the footswitch. :thumb

Also quite good for repairing separated rail dropper connections; dab a bit of liquid flux into the gap and straddle the joint with pressure from the tweezers prongs, zap-fizz, and the joint is re-established. :thumb

Les G

Excellent. I will defo get one. Which size is yours?

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LesGros
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Re: Resistance Soldering

Postby LesGros » Sun Feb 18, 2018 8:27 am

Hi Paul,
Some sizes:
From cable crimped connection to tip = 7inches
Rubbery padded finger grips = 4 inches
Grips are tapered from 3/4 inch to 1inch; [comfortable to use.]
Tips diameter 1/16 Inch
With Tips set to project by 1 inch, the gap between the points is 5mm [ sorry for mixed standards]
The 40 inch long, two core cable is quite beefy, and a bit stiff, but it will tend to hold a kink, which helps with control.
The cable ends have an unusual fitting, so they were cut off, and standard Banana plugs attached.
LesG

The man who never made a mistake
never made anything useful

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chrisf
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Re: Resistance Soldering

Postby chrisf » Sun Feb 18, 2018 9:31 am

On 15th February I posted on this thread a reading list on the subject of resistance soldering. I have now updated it to include some entries that had somehow become overlooked. It does not yet include David B's article in Snooze 207 for the simple reason that it has not yet been published.

Here, then, is the revised version. I would still welcome suggestions for useful material that I have not yet discovered.

Resistance soldering: Iain Rice. A handy and readable overview of equipment and techniques in typical Rice style. MRJ 51

A review of the MMS RSU: John Hayes. MRJ 77

Resistance soldering - what, how, why and where: Jol Wilkinson. Perhaps the handiest guide to the subject. MRJ 74

Readers’ letters. Various issues of MRJ

A review of the GB Electronics Ltd RSU: John Hayes. MRJ 73

Workshop: The Road to Damascus: Tim Shackleton. A self-confessed Luddite describes his experience with a Graskop RSU. RailModel Digest 1

Offset resistance soldering: Mike Grey. Application to soldered trackmaking. MRJ 82

Resistance Soldering – how to do it: Raymond Walley. Raymond is a 7mm practitioner who uses a London Road RSU supplemented by a steel baseplate and rare earth magnets to fine effect. http://www.raymondwalley.com

Resistance Soldering: Bob Alderman. A concise and well – ordered guide to the tool, its use and maintenance. EM Gauge Society Manual 5.7.3 (5)

Resistance Soldering Part 1 – Setting the Scene: David Brandreth. David explains the concept, benefits and uses of resistance soldering. Scalefour News 206

Have Gas Will Travel: David Brandreth. David describes the building of a GWR Cordon gas tank using both resistance and conventional soldering techniques. Finescale Railway Modelling Review 1

Working with Whitemetal: David Brandreth. David explains whitemetal soldering with a conventional iron and shows how an RSU may be used in adding brass detail to a whitemetal model. Finescale Railway Modelling Review 2

Chris

junctionmad
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Re: Resistance Soldering

Postby junctionmad » Sun Feb 18, 2018 11:48 am

I am going to build RSU , anyone have any specs or design criteria , also a source of the carbon probe etc. ( particulary a copper covered carbon probe preferably )

Thanks
Dave

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PeteT
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Re: Resistance Soldering

Postby PeteT » Sun Feb 18, 2018 7:50 pm

Thanks to David for spending the time writing the article, I look forward to part 2!

I am one of those who has had one in the cupboard (LRM, bought via ebay in unused condition, but did come with one of David's handy labels) which I picked up mid last year. Initially it was waiting for me to make a suitable baseplate, material for which I had a source in mind but was waiting for a trip. Then along came the members sales stand at the Portsmouth Exhibition in November (always worth a visit) - and there one was, for a mere £4.50!

So that left the round tuit as the only thing required. The article, the discussions on this forum, and a few face to face conversations made me hook it all up this afternoon and have a play! After a couple of tests with scrap, I bit the bullet and had a go for real.

The coach is an ex-LMS period 2 D1807 TO. The example I'm modelling is the solitary member of the type converted for push-pull use (M3484) by which time (or at which point?) the 2 large droplight windows on each side had gained an extra weather boarding strip along the top edge. Having already fitted the Stones ventilalors, I was rather dreading adding these weather boards (its been waiting some time for them...). I wanted to use thinner material than the half etched 10 thou in the ventilators (between the panes) - so had picked up some 2 thou brass sheet from Eileen's.

My 'iron' soldering isnt bad, but its fiddly tasks like this - which need previous parts not to move, the current piece to sit right and not move when nudged with the iron, my fingers not to burn through, etc, which I find a pain (often literally!). With the RSU it was a doddle! Very impressed with it. I used solder paste (Carrs 188) and found it perfect for the job.

20180218_172735.jpg


Also visible in the photo, alongside the job in hand and the RSU plate, are magnets I picked up from ebay. Some big chunky cylinders, and some smaller cubes.

Chris - I can't add to your list, but thanks for compiling. I've read Jol's and Raymond's before and found them good. I'll look out for the others!

One thing I did find a bit odd (but works to my advantage) is that it can't be as simple as the point of highest resistance in the circuit generating the heat (though I understand the theory as to why it should be, and can't work out the phenominon I'm seeing). On my test piece, I just had the carbon rod at the top of a 00 frame spacer I was attaching perpendicularly to another scrap held on the plate with a magnet. A tap or two on the foot pedal and nothing happened... but when I held the top of the frame spacer with something else, and had the rod closer to the joint, it worked.

Likewise with the coach, it was held on the baseplate with a magnet pretty much as per the photo, and it was the required joint which melted (right next to the probe), and not the ones on the coach side/end joints which the current was also passing through (I didnt have a spare lead to do a croc clip attachment directly onto the coach side, and tentatively gave it a go this way, having seen what I did on the test pieces).

This thing is seriously about to start earning its keep... :thumb

Cheers,
Pete

Phil O
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Re: Resistance Soldering

Postby Phil O » Sun Feb 18, 2018 8:29 pm

Try your local welding supplies, for carbon rods, the last time I got a couple for free, as that was all they had. Carbon rods can be used for cutting or gouging steel when used with MMA welding gear.

Phil.

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Jol Wilkinson
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Re: Resistance Soldering

Postby Jol Wilkinson » Mon Feb 19, 2018 7:20 am

Dave,

as the owner of LRM is a close friend of mine, I"ll leave you to work out your own RSU spec. Maplin used to sell a suitable transformer kit on which you could wind your own secondary outputs, but these are no longer available. I wound my own when the LRM unit was being developed but later replaced it with a professionally manufactured LRM transformer which was better.

The carbon probe is the easy bit, making a good probe holder is more difficult, which is why the LRM version is sold as a spare part and has been bought by owners of other makes of RSU.


Pete,

sometimes there isn't a good "connection" between the carbon probe tip and the workpiece. I keep a small piece of card near the return plate and rub the tip lightly on that. If I can write with it it is clean enough to work. The RSU voltage is low and won't always work on dirty or oily metal, so cleanliness is important.

Jol


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