Resisdence soldering or normal soldering whats the difference?

[Earl Bathurst]

I am after some advice started building locos, my last model I completed was using a normal soldering iron and solder. At a show in reading the weekend and advised to use resistance soldering when building as its alot easier. Any thoughts on this topic? Any advice would be most helpful

Scott

[jamie92208]

I've only started using an RSU recently and was amazed by it's capabilities.  It is very useful for attaching details to a part completed model but I always kep my normal iron fired up to use in awkward corners.   It's main use is to stop heat built up by in effect spot welding parts on. 

 

Jamie

[Jol Wilkinson]

Scott,

 

you will undoubtedly receive several different views on Resistance Soldering. Having used a RSU for over twenty years on 4mm models, I see it as complimentary to using a soldering iron. I would always recommend having a good temperature controlled iron as your main implement with an RSU for specific tasks. 

 

It is ideal for adding detail parts without excess solder around the joints, soldering overlays with minimum distortion, etc. When I start on a new model, I use the iron totally for the major components, with the RSU being increasingly brought into play as the model progresses and the finer detail is added.

 

Whilst I regard my Antex TCU as my main soldering tool, equally I wouldn't want to be without my RSU for the adding detail, etc. quickly and neatly.

 

Jol

[Andy Hayter]

I have both and in my opinion, both have their place.

 

I mainly use conventional soldering and as such the resistance unit could be viewed as a luxury.  Where IMHO resistance does come into its own is in places where you need to get a lot of heat in, but in a very controlled fashion.  So for example fine brass overlays on a coach or wagon side can be done with a conventional iron but you have to be careful not to distort the overlay in the process - get in and out fast with a heavy duty iron, but sometimes the size of such an iron can be a disadvantage.  This is one area where resistance soldering is a real boon.

[JeffP]

If you do buy one, you need to learn the technique and don't get confused when switching from RSU to normal.

 

In normal soldering the iron heats the joint, solder flows, the iron is REMOVED and the solder hardens.

 

Using an RSU, the current heats the joint overcoming it's resistance, you then switch off the current BEFORE removing the probe. The probe can be left in place while the joint cools and can hold the part in place. The probe will not solder itself to the joint.

 

But removing the probe BEFORE switching off results in a large arc, in some places it could be enough to seriously damage the etchings/castings.

 

Just be careful, that's all.

[Graham Hughes]

I am after some advice started building locos, my last model I completed was using a normal soldering iron and solder. At a show in reading the weekend and advised to use resistance soldering when building as its alot easier.

I have always got on fine with the soldering iron without any drawbacks. It is hard to envisage something else being "a lot easier". I often wonder if I am missing out on some great advantage from not using an RSU but I haven't ever seen anything to suggest what that might be. Apart from the occasional large brass dome, where I use a precision gas torch, and a particularly poorly designed etched kit many years ago that I don't believe was possible to solder. (Slatted grills on the side of a 3mm scale diesel loco which were etched in two layers. They buckled as soon as the heat got anywhere near them.) I can't say I have ever wanted to solder something that could not be done perfectly satisfactorily with a soldering iron. In view of their apparent popularity and comments like the one you received, I feel I ought to have an RSU but so far haven't been persuaded of the advantages of it. I do wonder if rather than being easier to use they are easier to learn to use.

[Talltim]

I've never used one, but I understand that the main advantage is that the heat can be generated more quickly in a small area, so you can solder next to previously soldered items without affecting them.

[Jol Wilkinson]

I've never used one, but I understand that the main advantage is that the heat can be generated more quickly in a small area, so you can solder next to previously soldiered items with affecting them.

That's one advantage, which also means that overlays can be added with less likelihood of distortion. Fitting parts where access with a soldering iron to get good contact with the tip of the bit is another.

 

Anther major advantage is that the item to be attached can be tinned so that there is only as much soldered as required to make the joint. Using an iron normally means that you get some additional/excess solder where you apply the tip to create the soldered joint.

 

The attached photo shows a small 4mm tender on which the long riveted strip under the side of the tank, the riveted horn guides either side of the axleboxes, the guides above the axleboxes and the steps (amongst other bits) were added with a RSU. They are as fitted with no further cleaning up afterwards.

 

It's one of those tools where all the uses aren't obvious until you have used one. To fit handrail knobs I tin the shank of the knob and hold it in place with a flat ended RSU probe which has a small dimple drilled in it, and apply the power. Result, accurately aligned knob and a clean joint with no excess solder.

 

 

Edited to correct spoling, damn, done it again.

[PGC]

To fit handrail knobs I tin the shank of the knob and hold it in place with a flat ended RSU probe which has a small dimple drilled in it, band apply the power. Result, accurately aligned knob and a clean joint with no excess solder.

 

 

Not thought of that before - and just as I'm coming up to adding handrail knobs to my J19. Thanks for the tip, Jol.

 

Phil

[chrisf]

I come at resistance soldering from a different perspective.  Having lashed out £150 on the unit I want to see just what it will do!  Most of our learning is done the hard way and I discovered that, for example, there are better ways of seaming than with the RSU.  One of my HMRS area group colleagues reminds me that he included this activity in a demo he did years ago but then he is a clever so-and-so!  For most tasks I would say that they can be accomplished both with the RSU and a conventional iron but there are times when my humble 25 watt Antex struggles.

 

In addition to the RSU I have a work station.  Made for me by Barry Fitch, it comprises a piece of MDF to which is attached a rectangle of mild steel, a pillar for attaching the negative lead and two adjustable bits of angle iron.  Add to these a dozen assorted magnets and with careful planning you should find that more hands are freed up than the good lord gave us.  Burnt fingers?  No thanks!

 

Chris

[Siberian Snooper]

Since I bought a London Road RSU a few years back I wouldn't be without it, you can do quite a bit with it, especially if you tin small bits first, add a little flux and a quick zap job done. Also very useful for holding bits in place using the probe, you can't do that with a conventional iron.

 

Instances of singed fingers is also much reduced.

[Earl Bathurst]

So do you use normal solder with residence soldering?

scott

[Siberian Snooper]

So do you use normal solder with residence soldering?

scott

Yes Scott, I do. If I have pre tinned something with electrical solder it will work with that. I also use solder paint/paste and Carrs solder creams.

[Earl Bathurst]

So solder paint, you paint it onto parts which need soldering then apply the probe is it?

scott

[Earl Bathurst]

Having built a loco using traditional soldering I can have a few messy joints and burnt fingers can be a pain. Rsu was highly recommended for loco building.

[TheWeatheringMan]

Hi,

Hope this isnt considered to be off thread as its not quite what the OP was asking but I thought it might be of interest here.

 

As a Resistance Soldering Unit is a fairly large expenditure I thought a working alternative to buying a ready made one might be of interest. This is based on articles published in the USA.

 

The total cost of this unit was aprox £60.00 when I built it in 2011.

 

This is my RSU constructed (or perhaps more correctly, reconstructed) from a standard battery charger.

 

Here are several photos of the unit. To save taking up this thread if its not of interest i'll not go into any more detail at this stage but if it does hold any interest for anyone i'll happily fully describe how it was done by starting a new thread.

 

Regards.

 

PS.

 

Have tried to upload photos on this tablet but file size is too large for RMWeb.

Will need to turn on laptop to reduce file sizes and then will upload pics shortly.

Sorry about this delay.

[Earl Bathurst]

Be interesting to see how you built the unit.

scott

[JeffP]

Solder cream or paste is good for adding small stuff, like, say, lamp irons.

Place TINY blob of solder cream/paste onto lamp iron base, place it in position, holding down with probe, tap footswitch, tap again it's fixed.

 

Most of the Far Eastern brass models you see will have been done with an RSU.

[TheWeatheringMan]

Hi,

well here go after a little delay.

The photos of my Resistance Soldering Unit refered to above.

 

This unit was rebuilt from a battery charger in 2011 and has been in regular use since, being used for anything from attaching lamp irons on etched kits with solder paint through to soldering the rail ends to pcb strips on a portable layout with normal cored solder - and pretty heavy working that was.

 

When the idea of building an RSU was first mooted in the USA there were, as is usual, several 'experts' who said it wouldn't work - even offering reasons why.

All I will say is many modellers went ahead and did it and have had no problems since - me included with the RSU you see here.

 

More info if anyone's interested.

 

Regards

[Horsetan]

Serious bit of kit, that.

 

I forgot that I had one of these RSUs buried somewhere - it is the LRM variant, but Exactoscale also used to produce one during the Bernie Weller era.

[Jol Wilkinson]

There are/have been severally commercially produced RSUs for the UK market.

 

The first was the Bernard Weller Exactoscale unit, introduced to the modelling world by Iain Rice in one of his WSP books. This came in "kit" form, with various optional extras, such as a case.

 

The London Road Models unit, designed by the late Mike Gray ( a highly qualified Electrical Engineer and lecturer). Introduced by LRM back many years ago, for a time it was produced and marketed by John Shelley of Fourtrack Models, but has been available again from LRM for several years. It is probably the most commonly used RSU in the UK owing to it's continued (with a brief exception) availability.

 

The Graskop Unit from Dick Ganderton, I believe now sold through Swanage Models.

 

All these provide varying output voltages from several secondary transformer windings, which gives a greater range of settings than was provided by the Mignon Models version which switched the transformer primary windings. As this was apparently some sort of off the shelf high power low voltage lighting transformer , this gave very little range of output voltages. 

 

The American Beauty range of RSUs  is also available in the UK but are considerably more expensive than the home grown offerings and  therefore not commonly used by modellers in my experience. The only person that I knew that had one was an optician who originally used it to to carry out repairs to spectacle frames.

 

A number of modellers have produced a home made version, usually based on a 12v battery charger. An internet search will turn up a variety of "how to" articles, mostly from the States. Some of the designs I have seen don't appear to have much variation in the output voltage but that may not be an issue for some applications of the technique. Clearly an understanding of safely designing 230 volt devices is a good idea.

[TheWeatheringMan]

There are/have been severally commercially produced RSUs for the UK market.

 

The first was the Bernard Weller Exactoscale unit, introduced to the modelling world by Iain Rice in one of his WSP books. This came in "kit" form, with various optional extras, such as a case.

 

The London Road Models unit, designed by the late Mike Gray ( a highly qualified Electrical Engineer and lecturer). Introduced by LRM back many years ago, for a time it was produced and marketed by John Shelley of Fourtrack Models, but has been available again from LRM for several years. It is probably the most commonly used RSU in the UK owing to it's continued (with a brief exception) availability.

 

The Graskop Unit from Dick Ganderton, I believe now sold through Swanage Models.

 

All these provide varying output voltages from several secondary transformer windings, which gives a greater range of settings than was provided by the Mignon Models version which switched the transformer primary windings. As this was apparently some sort of off the shelf high power low voltage lighting transformer , this gave very little range of output voltages. 

 

The American Beauty range of RSUs  is also available in the UK but are considerably more expensive than the home grown offerings and  therefore not commonly used by modellers in my experience. The only person that I knew that had one was an optician who originally used it to to carry out repairs to spectacle frames.

 

A number of modellers have produced a home made version, usually based on a 12v battery charger. An internet search will turn up a variety of "how to" articles, mostly from the States. Some of the designs I have seen don't appear to have much variation in the output voltage but that may not be an issue for some applications of the technique. Clearly an understanding of safely designing 230 volt devices is a good idea.

Hi,

My 'conversion' from a battery charger makes use of a dual six/twelve volt charger with 'fast' and 'normal' settings.

As converted this enables four power output levels which is more than sufficient for any modelling job i've needed to use it for.

As the conversion does not alter the mains side of the charger other than to transfer same to the fully insulated new case (as is done with most of the USA ideas mentioned) its not really necessary to know how to 'design' mains voltage equipment. All that is needed is common sense in doing the work.

The other thing that is worthwhile remembering if contemplating producing an RSU by this means is that the transformer in a battery charger is designed to be very rugged and to take an element of misuse - this is of great value when reused in this way, which is afterall actually a short term short circuit of the transformer secondary winding.

 

If you are looking to aquire an RSU its well worth considering as the results are excelent and the cost savings can be substantial.

 

Regards

[Siberian Snooper]

So solder paint, you paint it onto parts which need soldering then apply the probe is it?

scott

Hi Scott

 

Just a small amount to one surface place in position and hold with the probe a quick press of the foot pedal, I usually keep it depressed until the flux starts to "smoke" then lift off the pedal, don't move the probe until the job has cooled a bit. You soon get know how long you need to keep it depressed.

 

HTH.

[Siberian Snooper]

The London Road unit is excellent as it doesn't use any juice until you depress the foot pedal, as this is the on off switch. There are three power settings set by pushing the probe lead into the appropriate socket. A lot better than leaving the soldering on all night.

[Adrian]

There are/have been severally commercially produced RSUs for the UK market.

 

The first was the Bernard Weller Exactoscale unit, introduced to the modelling world by Iain Rice in one of his WSP books. This came in "kit" form, with various optional extras, such as a case.

 

 

Not sure if it pre-dates or post-dates the Exactoscale unit and Iain Rice book but there was a RSU produced by Cherry Scale Models IIRC circa 1984-1986. Complete and ready to use, i.e. not a kit.