Resisdence soldering or normal soldering whats the difference?

[TheWeatheringMan]

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.

Hi,

This is, I would have thought, the norm as the on off switching needs to be in the mains side of the transformer as to put it in the low voltage but high amperage 'soldering' side would require a very substantial switch with contact able to withstand switching the amperages involved without arcing and burn out.

My build complies to this and uses no power (other than the miniscule amount for the mains LED) when at rest, only fully powering up when the foot switch is depressed.

Regards

[JeffP]

That's it. The foot switch on mine is similar to that on a sewing machine.

[TheWeatheringMan]

That's it. The foot switch on mine is similar to that on a sewing machine.

Hi,

Indeed. In many of the USA articles the suggested footswitch is exactly that. In most cases the f/s is modified to bypass the variable resistance used to give a variable speed to the sewing machine motor but not able to give a variable power output for an RSU.

My footswitch came from Rapid Electronics and although the switch is mains rated the surprising thing is that the cable on it was fitted with a 3.5mm jack plug of audio type. I changed the cable so as to get a more substantial plug and a socket on the unit front panel that is completely shielded in view of its carrying the full mains voltage.

 

A relevent point about such a conversion is that of course in the USA the conversion could be considered 'safer' due to the (usually) non fatal lower mains voltage of 110 volts.

Regards

[Mark Forrest]

I've only recently got myself a RSU (a LRM one) and am still getting used to using it. However, I can already see that it is excellent for adding small details and overlays. I'm not the tidiest of workers with a traditional iron but this is much improved by using the RSU. It doesn't replace a normal iron, but definitely complements it IMO. Downside is the cost, so just depends how much use you expect to get from it.

[Jol Wilkinson]

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.

Actually there are six outputs, by selecting two of the four outlets in various combinations, as shown in this copy of one of the instructions pages.

 

Jan 2010 instr diag.pdf

[Earl Bathurst]

I see swanage model company do a rsu, is that ok or would you go for the london road models unit?

Thanks for all the advice so far. Getting very tempted to treat myself.

[EKR]

An RSU is a great tool for soldering, but one area not mentioned so far is it's additional usefulness in dismantling and adjusting things.

Being able to push at a joint with the probe whilst applying heat is very handy for taking things apart. I could use a gas burner but I try to avoid flames where possible given the state of my bench.

 

There is also the ability to tweak a joint you're not happy with.

Sometimes you finish soldering and on viewing the result are vaguely dissatisfied with it. Perhaps it's not perfectly aligned, just a small push with the probe can adjust the joint or moulding a few millimetres to rectify the problem, with minimal mess or distortion.

 

It's a great addition to the kit builders workbench and I wouldn't be without mine.

[Jol Wilkinson]

I am obviously biased towards the LRM unit, but can't make any definite comparisons because I don't know the details of the Swanage Models Unit. The LRM unit utilises a purpose built transformer, brass collett probe holder with insulated handle and stainless steel case. The footswitch is a Radiospares component., while flexible silicon coated leads are supplied as standard.

 

The LRM unit is the possibly the best selling, partly due to the fact that it has been more visible through LRM's regular attendance at various shows including the 4mm societies exhibitions. It often is used on soldering demo stands at exhibitions which I think that is probably a result of greater sales. It has also been sold through Hobby Holidays which increases it's visibility in the dedicated 7mm exhibitions.

 

If you have any queries about the unit, you can contact LRM's proprietor, John Redrup, through the contact link on the LRM website at;

 

http://traders.scalefour.org/LondonRoadModels/contact-us/

[Bruciethefish]

Since acquiring a 'Graskop' RSU, my 25 watt iron has barely seen any use;- I use the 15W antex for small jobs, & the resistance unit for almost everything else. On a high setting, it's particularly good for soldering thick brass components like milled chassis frames & spacers. You can get a huge amount of heat into these quickly, & more important, evenly. I honestly don't know how I managed without it for brass & nickel kits...

[Adrian]

Since acquiring a 'Graskop' RSU, my 25 watt iron has barely seen any use;- I use the 15W antex for small jobs, & the resistance unit for almost everything else. On a high setting, it's particularly good for soldering thick brass components like milled chassis frames & spacers. You can get a huge amount of heat into these quickly, & more important, evenly. I honestly don't know how I managed without it for brass & nickel kits...

 

 

Hi, no disrespect intended * and not directed specifically at you (just using this as an example) but to be honest I'm not surprised you have not used your 25W iron, but I would suggest that this is because I would consider the 25W iron seriously underpowered for the jobs you indicate. For thick brass components I would suggest at a bare minimum a 40W iron, but an 80W iron would be preferable. So to be honest I'm not surprised the RSU was significantly better. Soldering is very simple it's just a case of getting sufficient heat into the job so I'd suggest that you wouldn't see much difference between a bigger iron an an RSU.

 

An RSU is what I would term a "marmite" tool - you either love it or you hate it. For myself I'm in the "hate it" camp. I use an ERSA RDS-80 iron and this does everything I need for soldering. As I mentioned soldering is very very simple, all it needs is heat in the joint and the solder will flow. I can solder quite small detail using solder paste with a standard iron and I can control where the solder flows, I struggled with the RSU because the hottest point wasn't always where the probe was, it's where the resistance is the highest - hence the name! I always struggled to get the solder to flow cleanly along a seam with the RSU's I have used. When I see all these guides about RSU's using earthing plates and magnets I despair sometimes, as I believe it shows a lack of understanding about the fundamentals of soldering. As I will repeat time and time again it is all about getting heat into the job. Witness the craftsmen who solder white metal with a blow torch! They have the confidence to get heat in just where it is needed. So all this messing about with earthing plates and magnets is an anathema to me.

 

So my recommendation would be to invest in a good quality soldering station first, I'd highly recommend the ERSA RDS-80. Practice soldering on scrap etches and after you have built your loco(s) and want to try an RSU find someone or a club where you can practice with one before committing to buying one. I've had two RSU's over the years because I thought I needed them to improve my modelling - they both got sold as I never used them, one on eBay, and I actually got more value for money signing up for an evening class in jewellery making where I learnt how to silver solder, lessons learnt from that are very transferable to soft-soldering.

 

Regards

 

Adrian.

 

* sorry to use the "no disrespect intended" option as that usually means that the person saying it is being disrespectful but wants to claim otherwise and I detest using it - however in this respect it is meant honestly, there are quite a few articles on the web that talk about the 'black art of soldering' and claim to clear up 'myths and facts' of soldering and then go onto to talk, in my opinion, some utter claptrap. So my post is aimed at them rather than Bruciethefish posting per se.  

[Dazzler Fan]

+

[Dazzler Fan]

I have found a toothpick and paste is

the way to go, whether RSU or Iron.

 

Noel

[TheWeatheringMan]

Since acquiring a 'Graskop' RSU, my 25 watt iron has barely seen any use;- I use the 15W antex for small jobs, & the resistance unit for almost everything else. On a high setting, it's particularly good for soldering thick brass components like milled chassis frames & spacers. You can get a huge amount of heat into these quickly, & more important, evenly. I honestly don't know how I managed without it for brass & nickel kits...

 

Hi Chris,,

Perfectly put and so right.

Just a small question though - how do you ´strike´ the arc on one of your superb resin loco bodies !!!!!!!..

 

I´ll grab my coat as I go..

 

All the best Mate and compliments of the Season..

[Jol Wilkinson]

Hi, no disrespect intended * and not directed specifically at you (just using this as an example) but to be honest I'm not surprised you have not used your 25W iron, but I would suggest that this is because I would consider the 25W iron seriously underpowered for the jobs you indicate. For thick brass components I would suggest at a bare minimum a 40W iron, but an 80W iron would be preferable. So to be honest I'm not surprised the RSU was significantly better. Soldering is very simple it's just a case of getting sufficient heat into the job so I'd suggest that you wouldn't see much difference between a bigger iron an an RSU.

 

An RSU is what I would term a "marmite" tool - you either love it or you hate it. For myself I'm in the "hate it" camp. I use an ERSA RDS-80 iron and this does everything I need for soldering. As I mentioned soldering is very very simple, all it needs is heat in the joint and the solder will flow. I can solder quite small detail using solder paste with a standard iron and I can control where the solder flows, I struggled with the RSU because the hottest point wasn't always where the probe was, it's where the resistance is the highest - hence the name! I always struggled to get the solder to flow cleanly along a seam with the RSU's I have used. When I see all these guides about RSU's using earthing plates and magnets I despair sometimes, as I believe it shows a lack of understanding about the fundamentals of soldering. As I will repeat time and time again it is all about getting heat into the job. Witness the craftsmen who solder white metal with a blow torch! They have the confidence to get heat in just where it is needed. So all this messing about with earthing plates and magnets is an anathema to me.

 

So my recommendation would be to invest in a good quality soldering station first, I'd highly recommend the ERSA RDS-80. Practice soldering on scrap etches and after you have built your loco(s) and want to try an RSU find someone or a club where you can practice with one before committing to buying one. I've had two RSU's over the years because I thought I needed them to improve my modelling - they both got sold as I never used them, one on eBay, and I actually got more value for money signing up for an evening class in jewellery making where I learnt how to silver solder, lessons learnt from that are very transferable to soft-soldering.

 

Regards

 

Adrian.

 

* sorry to use the "no disrespect intended" option as that usually means that the person saying it is being disrespectful but wants to claim otherwise and I detest using it - however in this respect it is meant honestly, there are quite a few articles on the web that talk about the 'black art of soldering' and claim to clear up 'myths and facts' of soldering and then go onto to talk, in my opinion, some utter claptrap. So my post is aimed at them rather than Bruciethefish posting per se.  

As I said in post #3 you will undoubtedly receive several different views on Resistance Soldering. Adrian's view that an RSU is a "marmite" tool pretty much sums it up.  Some people never get the hang of using them, probably because they haven't appreciated how to get the best out of the technique.

 

I agree entirely that the first tool you should have in your soldering tool kit is a good soldering iron, preferably temperature controlled and at least 50 watts. Always go for one that has a range of bits, from 1mm to 5 mm for 4mm modelling. Follow the right approach, use the right temperature solder for the job and the right flux and you will be able to get the job done every time.

 

However, an RSU is still a great addition to the tool kit, particular for adding fine detail with the minimum of excess solder. As I said above, I've had one for years and can produce better models more easily, quicker and with less frustration than without it.

 

I use one of those earthing plates (with magnets and steel alignment blocks) successfully because I understand how the technique works. I also use them as a jig when I am using my 50 watt Antex TCU, so don't be put off. 

 

Hi Chris,,

Perfectly put and so right.

Just a small question though - how do you ´strike´ the arc on one of your superb resin loco bodies !!!!!!!..

 

I´ll grab my coat as I go..

 

All the best Mate and compliments of the Season..

Striking an arc? Sounds like arc welding, not resistance soldering.

[Enterprisingwestern]

Hammer and screwdriver comparison really, both do basically the same job, but one is more suitable than the other at times.

Likewise with irons and RSU's IMHO.

 

Mike.

[TheWeatheringMan]

 

 

Striking an arc? Sounds like arc welding, not resistance soldering.

 

Hi,

Sence of humour bypass ??

Regardss

[Graham Hughes]

Thank you Adrian, for that post. I was beginning to think it was just me as I read the posts about the things that can be done with an RSU and thinking, "But I already do that with the soldering iron." I suspect that a lot of the advantages only arise out of mis-conceptions about soldering, such as people using a lower powered iron and smaller bits for details. If you have a decent sized but and a sufficiently powerful iron then adding details by pre-tinning the parts and/or using a dab of solder paste and a quick flash of the iron is no different than what is being described for the RSU.

 

 I suspect that the main advantage of the RSU is that it is easier to become accomplished at using it to do the same things you can do with a soldering iron rather than having any additional capabilities beyond what can be done with the iron. Which, in itself, would seem to be a recommendation for someone relatively new to soldering. 

 

 

 

I agree entirely that the first tool you should have in your soldering tool kit is a good soldering iron, preferably temperature controlled and at least 50 watts. 

 

 

Can I ask why? I have a temperature controlled iron as it seemed, like an RSU, to be "a good thing" that I ought to have. I bought it at least 30 years ago now and after the first couple of weeks trying to match the setting to the task in hand I realised there is no match and set the thing to its maximum where it has remained ever since. Surely, turning down the temperature only reduces the ability of the iron to put heat into the joint quickly which is the exact opposite of what you want.

[Mark]

 

 

 

The main advantage of the RSU is it frees up a hand. You hold the part in place with the probe and use the foot switch to apply power. The joint is instant with no need to wait for the joint to warm up. I use mine exclusively for lamp irons and other small parts that are difficult to hold and solder at the same time. Maybe a luxury in General soldering terms, but it pays for itself in the time saved with small parts.

 

Regards

 

Mark Humphrys

[PGC]

Thank you Adrian, for that post. I was beginning to think it was just me as I read the posts about the things that can be done with an RSU and thinking, "But I already do that with the soldering iron." I suspect that a lot of the advantages only arise out of mis-conceptions about soldering, such as people using a lower powered iron and smaller bits for details. If you have a decent sized but and a sufficiently powerful iron then adding details by pre-tinning the parts and/or using a dab of solder paste and a quick flash of the iron is no different than what is being described for the RSU.

 

 I suspect that the main advantage of the RSU is that it is easier to become accomplished at using it to do the same things you can do with a soldering iron rather than having any additional capabilities beyond what can be done with the iron. Which, in itself, would seem to be a recommendation for someone relatively new to soldering. 

 

 

 

Can I ask why? I have a temperature controlled iron as it seemed, like an RSU, to be "a good thing" that I ought to have. I bought it at least 30 years ago now and after the first couple of weeks trying to match the setting to the task in hand I realised there is no match and set the thing to its maximum where it has remained ever since. Surely, turning down the temperature only reduces the ability of the iron to put heat into the joint quickly which is the exact opposite of what you want.

 

Unless I'm wrong (it's possible!) this statement is not accurate, The factor that determines how much heat is put in to the joint is the wattage of the iron.

 

Going back to basics, every action has an opposite and equal reaction. So when you put a hot iron to a cold piece of metal, the cold piece of metal starts to warm up while the hot iron starts to cool down. The more wattage the iron has, the more possibility it has of keeping warm rather than cooling down.

 

A temperature iron is a godsend if you want to use just one iron and want to solder brass, nickel silver or whitemetal. If you try using the one iron for all metals and have the temperature set for brass or nickel silver, you will almost certainly melt the whitemetal and end up with a blob rather than loco or wagon.

 

While on this topic, may I digress slightly and tell, as I understand it, how an RSU works. When an electircal current is passed through a medium, provided that medium has the same resistance all the way through it (like a piece of wire), the current will flow freely. OK, Yes, there are rules about induction etc, but I'm trying to keep this simple!

 

When a current, however, is passed through two mediums that either have differing resistances or a medium of a different resistance between them (a gap, for example), the current will, in overcoming the resistance, produce heat, and in resistance soldering, it is this heat that melts the solder and makes the joint.

 

What this then shows is that a soldering iron is a different tool from an RSU and should therefore be used in a different way. As some people have said, they find they only use an RSU. Others have said they can't see the point of an RSU. Personally, I have both, wouldn't be without the RSU, but also wouldn't be without a soldering iron.

 

And now I'm going to sit back and see how many people criticise my attempt to explain in simple terms how an RSU works! :-)

 

Phil

[Jol Wilkinson]

Hi,

Sence of humour bypass ??

Regardss

No, I noticed your RSU has a label saying Live/Arc, so I assumed that's what you do with it.

[Adrian]

 

As I said in post #3 you will undoubtedly receive several different views on Resistance Soldering. Adrian's view that an RSU is a "marmite" tool pretty much sums it up.  Some people never get the hang of using them, probably because they haven't appreciated how to get the best out of the technique.

 

 

 

The main advantage of the RSU is it frees up a hand. You hold the part in place with the probe and use the foot switch to apply power. The joint is instant with no need to wait for the joint to warm up. I use mine exclusively for lamp irons and other small parts that are difficult to hold and solder at the same time. Maybe a luxury in General soldering terms, but it pays for itself in the time saved with small parts.

 

What are you using the free hand for then?  Lamp irons, sometimes I'll tin them otherwise a small dab of solder paste on the joint, hold lamp iron with tweezers in one hand, soldering iron in the other hand.

 

I think what I'm trying to say is that I struggle to see the advantage of them, they are just different. I'd like to think I got 'the hang of using them' but I simply found I could get just as good a joint with a normal soldering iron, and when it came to using them I always went for the soldering iron first, messing about with all the wires, footswitch, earthing plate or strap meant that the RSU just sat there gathering dust. I just hope the guy that bought it from me gets more use out of it than I did.

[Jol Wilkinson]

Thank you Adrian, for that post. I was beginning to think it was just me as I read the posts about the things that can be done with an RSU and thinking, "But I already do that with the soldering iron." I suspect that a lot of the advantages only arise out of mis-conceptions about soldering, such as people using a lower powered iron and smaller bits for details. If you have a decent sized but and a sufficiently powerful iron then adding details by pre-tinning the parts and/or using a dab of solder paste and a quick flash of the iron is no different than what is being described for the RSU.

 

 I suspect that the main advantage of the RSU is that it is easier to become accomplished at using it to do the same things you can do with a soldering iron rather than having any additional capabilities beyond what can be done with the iron. Which, in itself, would seem to be a recommendation for someone relatively new to soldering. 

 

 

 

Can I ask why? I have a temperature controlled iron as it seemed, like an RSU, to be "a good thing" that I ought to have. I bought it at least 30 years ago now and after the first couple of weeks trying to match the setting to the task in hand I realised there is no match and set the thing to its maximum where it has remained ever since. Surely, turning down the temperature only reduces the ability of the iron to put heat into the joint quickly which is the exact opposite of what you want.

Graham,

 

the temperature/power relationship has been discussed several times on RMweb. Power is the ability to heat up the bit. Higher temperature only helps as it provides a small reservoir of heat but once the temp drops when the bit is applied to the work, it is power (watts) that maintains it. More watts, more ability to sustain the temperature.

 

Setting the temp to suit the solder prevents overheating it and forming various oxides, etc. which tarnish the bit and the solder on the joint. Likewise you can solder low melting point alloys, like white metal.

 

Jol

[Siberian Snooper]

My dad taught me how to solder at the age of about 6 with a 50 watt iron and a 1/4 inch bit without problems. I now have an arsenal of irons an 80 watt, a 25 watt, a 40 watt temp control, a 12 volt unknown wattage, used with a variable transormer, for white metal and the RSU and my favourite by far is the RSU. By the way I'm nearly sixty now.

[Adrian]

addendum : Just look at what the 2mmFS people are doing - that's some damn fine detailing with little excess solder - all done with a normal iron.

Click on the photo's to enlarge - very impressive. So this is why I say I struggle to see the advantage of an RSU as I don't think it could do it any better than this.

http://www.rmweb.co.uk/community/index.php?/blog/1004/entry-8277-2mm-scale-lnwr-diagram-88-van-building-the-van-body/

[Jol Wilkinson]

 

 

I think what I'm trying to say is that I struggle to see the advantage of them, they are just different. I'd like to think I got 'the hang of using them' but I simply found I could get just as good a joint with a normal soldering iron, and when it came to using them I always went for the soldering iron first, messing about with all the wires, footswitch, earthing plate or strap meant that the RSU just sat there gathering dust. I just hope the guy that bought it from me gets more use out of it than I did.

 

What's the problem? My workplate sits alongside my formica covered worksurface, the RSU and TCU sit side by side at the back on the bench, with the iron and probe in soldering iron rests. The footswitch is on the floor under the bench. Of course I am fortunate to have a permanent workbench, but even when I didn't I used to set up things so that the toolsI needed were to hand. 

 

Now, having the Unimat handy is a different matter.