The Adventures of an RSU Virgin

Includes workshop practice, painting and weathering, model photography etc.
Enigma
Posts: 289
Joined: Tue Aug 13, 2013 2:49 pm

The Adventures of an RSU Virgin

Postby Enigma » Thu Feb 15, 2018 2:53 pm

Following my contribution to the S4News 260 thread regarding Dave Brandreth's article, I'm starting this thread to allow myself and other neophytes to tell all about their experiences with their still pristine RSU's. Mine is a London Road one, purchased at least 20 years ago (and probably more. When were they introduced?) and has been in its box on a shelf in the workshop ever since. I can't really say why I have never used it. Plenty of my modelling friends use theirs to great effect and express surprise when I tell them of my non-experience. This will now change! I can't promise to add posts every day but if you want to - then go ahead.

Earlier this week I added another small shelf to my workspace, on the right and just above worktop height. On this I have positioned my trusty RS Components temperature controlled iron and the LR RSU. I have also made an RSU 'workplate' using a small rectangle of 6mm ply (approx 9" x 6") with a rectangle of tinplate and a length of aluminium angle (originally intended for cassette manufacture) screwed to the surface. The black RSU lead is attached to a 3mm bolt screwed up from underneath through both the angle and the tinplate in one corner. Small screws fix the remaining corners in place, one of them passing through both the angle and the tinplate. Electrical continuity is therefore maintained. A photo will follow in due course.

This morning I decided that the time had come to break my RSU celibacy so a few oddments of brass etch scrap were gathered. One was already tinned so with a touch of thinned Powerflo flux it was zapped onto another scrap with absolutely no trouble at all. A third piece had a minute blob of Carr's 188 solder 'paste' added and this in turn was zapped onto the first piece. All incredibly simple and clean - why haven't I done this before!!!

I'm now trawling through my 'stash' of old kits looking for something to 'have a go at'. I think I have a Jidenco brake van somewhere so that may well be a starting point. If I can get that together satisfactorily then I can probably build anything!

Over to you now!

User avatar
RobM
Posts: 954
Joined: Sun Feb 15, 2009 4:39 pm

Re: The Adventures of an RSU Virgin

Postby RobM » Thu Feb 15, 2018 5:37 pm

They are addictive Paul........
I have some M3 studding to add to the legs of my headstocks to attach it to the baseboard, will be much easier with the RSU, certainly could not attempt it with a soldering iron, the whole structure would probably all fall apart if ever I was able to get enough heat from a soldering iron!!
Rob
http://www.robmilliken.co.uk
Updated December 2016

Enigma
Posts: 289
Joined: Tue Aug 13, 2013 2:49 pm

Re: The Adventures of an RSU Virgin

Postby Enigma » Fri Feb 16, 2018 4:26 pm

Here's a couple of photos of the new shelf and the RSU 'table'.
Soldering Shelf.2.A.jpg
Soldering Shelf.2.A.jpg (196.74 KiB) Viewed 6222 times

RSU table.2.A.jpg
RSU table.2.A.jpg (232.18 KiB) Viewed 6222 times

I've started on the Jidenco Brake Van. It's the Cambrian one and, on checking with a couple of photos in Jim Russell's first GWR wagon book - it ain't very accurate! Par for the course I suppose with Jidenco. However, it'll do as a first attempt with the RSU although I think there may well have to be some 'normal' soldering involved in several places.

Watch this space!

BTW, what sort of small magnets do people tend to use with their 'tables'? I've seen some on 'First4Magnets.com', neodymium ones, round approx 4-6mm diameter x 10-12.5mm long. This the type?

User avatar
chrisf
Posts: 157
Joined: Tue Jul 22, 2008 10:59 am

Re: The Adventures of an RSU Virgin

Postby chrisf » Fri Feb 16, 2018 6:44 pm

I bought a selection of magnets from Squires. These have since been supplemented by some corsage magnets which may be had from department stores. I understand that their purpose is to attach flowers to ladies.

Chris

Enigma
Posts: 289
Joined: Tue Aug 13, 2013 2:49 pm

Re: The Adventures of an RSU Virgin

Postby Enigma » Tue Feb 20, 2018 2:03 pm

Finally lost all patience with the Jidenco 'kit'. Ended up jumping on it and chucking it in the bin! That's three days modelling time I won't get back. Can't say that the RSU was much help either. Lots of joints wouldn't stay soldered, had to get the iron fired up to complete them. Possibly I'm now unconvinced as to how good RSU's actually are.

User avatar
Guy Rixon
Posts: 709
Joined: Sun Mar 27, 2011 6:40 pm

Re: The Adventures of an RSU Virgin

Postby Guy Rixon » Tue Feb 20, 2018 4:16 pm

Carrs' 188 solder paste and an RSU are together very good at making dry joints. Back when I had a working RSU (it died just as I was getting good with it) this combination gave me no end of trouble. Pre-tinned parts spot-welded with the RSU worked better for me.

I speculate that the solder paste only works reliably if the joint is sweated such that all the flux reacts. An RSU is not well placed to do that.
Last edited by Guy Rixon on Tue Feb 20, 2018 6:00 pm, edited 1 time in total.

User avatar
David B
Posts: 1247
Joined: Sun Jul 20, 2008 5:30 pm

Re: The Adventures of an RSU Virgin

Postby David B » Tue Feb 20, 2018 5:05 pm

A useful way I have found to butt joint two pieces with an RSU is to lightly tin just the ends of a piece with 'proper' solder - I use 145o - and a conventional iron. These two blobs will lift the piece up but when the solder melts, the piece drops in to place and is tacked at each end. I have never been successful with solder paste.

I then run some flux along the length of the joint and, in the middle, put a small piece of solder I have cut off the reel. You can see bits in the pot at the end of my article in S4 News 206. Make sure it is touching both pieces of metal and apply the probe from the opposite side, the probe again being put right in the joint, touching (and heating) both bits of metal. If the flux boils and pops the solder off, put it or another piece of solder (the first having got lost in the carpet) back and try again. I often find re-fluxing is unnecessary but you will have to try this.

The solder should flash along the joint and you can sometimes 'drag' the solder by sliding the probe (you have, of course, made sure the metal was clean first!). Solder follows the heat. You can then repeat the process in any gaps.

I am sure other people have their own way of doing this with an RSU. If you try tinning an edge along the whole length, it is very difficult (= impossible) to get it to sit right down in place because you can't melt all the solder at once, hence my 'tacking' each end first.

It takes less time to do than I have taken writing this.

Enigma
Posts: 289
Joined: Tue Aug 13, 2013 2:49 pm

Re: The Adventures of an RSU Virgin

Postby Enigma » Tue Feb 20, 2018 5:23 pm

Thanks for the tips guys. All the parts/joints I had fail were pre-tinned and seemed OK at first but then failed later when I was trying to attach something else - but nowhere near the failed joint! I'll keep trying, possibly with some alternate flux etc. and report back to you at S4N!

That's if,of course, I'm still sane by then.................. :?

BTW, the Jidenco kit was abysmal. Badly 'designed', badly etched and lots of variances from the prototype. I was only using it as a test piece but even so I completely lost it! Should have kept it in the packaging and sold it on as a 'collectors item'.

Hopefully I'll get on better with my RSU and my next High Level kit, the L&Y steeple cab which has lots of overlays and seems ideal for this method of building.

User avatar
RobM
Posts: 954
Joined: Sun Feb 15, 2009 4:39 pm

Re: The Adventures of an RSU Virgin

Postby RobM » Tue Feb 20, 2018 5:42 pm

I have never used solder paste.......on my headstocks which I would consider to be slightly more heat requiring than a loco or wagon, included standard etches and some milled brass section and M3 studding I tinned all the parts with a soldering iron then a zap with the RSU and all was very solid and remains so.
I use 188 solder and green flux.
Paul, good luck with your next trial venture, I'm sure you will get there and finally accept the RSU as the next best thing to sliced bread!!!!
Rob
http://www.robmilliken.co.uk
Updated December 2016

Enigma
Posts: 289
Joined: Tue Aug 13, 2013 2:49 pm

Re: The Adventures of an RSU Virgin

Postby Enigma » Tue Feb 20, 2018 6:05 pm

Perhaps I could bring my unit down on the 3rd for some practice and 'coaching'?

User avatar
David B
Posts: 1247
Joined: Sun Jul 20, 2008 5:30 pm

Re: The Adventures of an RSU Virgin

Postby David B » Tue Feb 20, 2018 6:10 pm

Enigma wrote:Hopefully I'll get on better with my RSU and my next High Level kit, the L&Y steeple cab which has lots of overlays and seems ideal for this method of building.


Don't forget, Paul, that the RSU is not always the right tool for some jobs. I am aware that a few people use one for virtually everything, but in general, it is a tool best used in conjunction with a conventional iron. Some jobs really are better done with a conventional iron whilst for others, you can't do the job anywhere near as well with an iron as you can with an RSU. Experience, practice and perseverance are the important words.

I use an RSU for attaching almost all brass bits to white metal. The RSU is brilliant for attaching detailing bits and, as you suggest, overlays (think about applying the probe from the back rather than the face). I don't even think of using one to make screw couplings or moving parts.

User avatar
David Thorpe
Posts: 920
Joined: Tue Oct 21, 2008 11:13 pm

Re: The Adventures of an RSU Virgin

Postby David Thorpe » Wed Feb 21, 2018 8:43 am

Guy Rixon wrote:I speculate that the solder paste only works reliably if the joint is sweated such that all the flux reacts.


I've used solder paste quite successfully with my RSU, but I always add extra liquid flux before applying the iron. While the paste incorporates flux, there doesn't seem to be enough for use with an RSU.

DT

jasp
Posts: 120
Joined: Thu Dec 04, 2008 9:24 am

Re: The Adventures of an RSU Virgin

Postby jasp » Wed Feb 21, 2018 5:36 pm

One thing I have found useful with my LR RSU is to sharpen the carbon to a point using a desk mounted pencil sharpener. When it wears/rounds off, another wee turn in the sharpener does the trick.
Jim P

User avatar
steve howe
Posts: 610
Joined: Sun Feb 01, 2009 10:16 pm

Re: The Adventures of an RSU Virgin

Postby steve howe » Wed Feb 21, 2018 11:28 pm

David B wrote: The RSU is brilliant for attaching detailing bits and, as you suggest, overlays (think about applying the probe from the back rather than the face).


David, would you be able to elaborate a bit more on attaching overlays? I've got a couple of Mallard 517s awaiting attention and having built one years ago, I recall it made extensive use of overlays for the tank and cabsides. I'm interested to know how the RSU makes the task easier than a (large) conventional iron?

Steve

User avatar
David B
Posts: 1247
Joined: Sun Jul 20, 2008 5:30 pm

Re: The Adventures of an RSU Virgin

Postby David B » Thu Feb 22, 2018 9:24 am

I tin the overlays whilst still on the fret. This makes handling easier and you can run the iron off on to the etch edge as you always get a thicker blob where the iron is lifted off.

Where the overlay is going, I wipe thoroughly with flux. I use Carr's yellow which I understand to be phosphoric acid. This not only brightens the brass but also cleans off any remaining light greasy areas. I suggested a little experiment at the end of Part 1 of my article in News 206:

On a piece of scrap fret, wipe a small area thoroughly with flux, then tin it but at the same time, try to tin the adjacent, un-fluxed area. If the scrap is old or has been handled, the solder should flow easily on the fluxed part but not adhere or flow well on that which has not been fluxed.

The overlay is then put in position, lining up the centre, and I hold it in place, often with clips - I usually use those small wooden pegs from the Pound shop or hackle pliers from the angling shop. There are other methods. The first zap of the RSU is in the middle, then a short distance to the left, then right, left, right, working my way outwards from the centre towards the end. After the first two or three zaps, the clips can be removed. Never tack an end (until the last) as the overlay expands slightly as you solder and you will be left with a bump. With a broader overlay like a tank side, put the first zap in the middle and work outwards in a spiral or circular manner. Similarly work from the centre outwards with ironwork overlays on the ends or sides of wagons.

Sometimes, you might find it useful to make a jig as I did for solebars. You could make something similar for buffer beams.

You ask about comparing the RSU and an iron. I suppose the job can be done in a similar way with an iron, but you would need the bit to be clean (no solder) and hot. You might have trouble getting the bit in a channel such as a solebar and supplying sufficient heat. The RSU supplies plenty of heat and because the tip is narrow can get in to smaller spaces.

For a second experiment, I suggested in the article:

Tin, not too meanly, an area [of scrap brass] about an inch in diameter. Put the probe in the centre and operate the switch. Watch how the heat flows outwards, melting the solder. Leave the probe in place and take your foot off the switch. See how quickly the solder cools. Do this at different voltages. You should now have an idea of what is happening when you use the RSU on your kit.

The RSU supplies the heat quickly and locally. The conventional iron supplies heat much more slowly and heats a much larger area which means there is a danger of unsoldering nearby objects, a danger significantly reduced when using an RSU. This is not so important with overlays where the RSU is, in my opinion, quicker and easier than a conventional iron. On the whole, I also find the RSU cleaner.

I have said before and no doubt will do so again: the RSU is not a tool that will solve all soldering problems. It is right for some jobs and not for others. Ultimately, it is up to the modeller to decide when it is appropriate to use which tool, but I think you will find that amongst those modellers who have got to grips with resistance soldering, the RSU is the preferred tool when applying overlays. You can also hold smaller overlays in place with the RSU probe before and after soldering.

Enigma
Posts: 289
Joined: Tue Aug 13, 2013 2:49 pm

Re: The Adventures of an RSU Virgin

Postby Enigma » Thu Feb 22, 2018 2:05 pm

After cogitating overnight on my 'jumping' act, I re-visited the bin this morning and extracted the sorry bent and twisted remains. Full of remorse and embarassment I delicately tried to straighten the cadaver as I had a midnight revelation that perhaps I could re-engineer it into a freelance industrial brake van. One of the ends was beyond redemption but I did manage to flatten out the worst of the abuse. However, whilst doing this I discovered (again!) that several of the RSU applied strapping overlays were coming adrift all to easily, one in fact only seemed to be held on by the sticky remains of the flux! At the time of original fixing they all seemed to be securely attached so why would this be?

I have removed the badly distorted balcony making it a single ended van, used one of the intended 'internal' ends as an external one (please don't tell anyone) and re-assembled the parts using my conventional iron. I'm still not certain about any external 'decoration'. One thought is to apply some outside framing using Evergreen rectangular sections attached with 5 min epoxy or similar. I'm not averse to using different materials to obtain the result I want.

I will persevere with the RSU, taking into account all the helpful tips people here have posted and will keep you posted on my efforts in due course!

User avatar
David B
Posts: 1247
Joined: Sun Jul 20, 2008 5:30 pm

Re: The Adventures of an RSU Virgin

Postby David B » Thu Feb 22, 2018 2:35 pm

Enigma wrote: . . . I discovered (again!) that several of the RSU applied strapping overlays were coming adrift all to easily, one in fact only seemed to be held on by the sticky remains of the flux! At the time of original fixing they all seemed to be securely attached so why would this be?


It could be for a variety of reasons, Paul - the metal was not clean enough; insufficient solder; insufficient heat (not long enough with your foot on the gas). These are three which come immediately to mind.

This has happened to me in the past. I cleaned up the parts, paid particular attention to the all-important "cleanliness when soldering" and re-did the job. Sometimes, I have just been too mean with the tinning - it does need to be a little more than one molecule thick

User avatar
steve howe
Posts: 610
Joined: Sun Feb 01, 2009 10:16 pm

Re: The Adventures of an RSU Virgin

Postby steve howe » Thu Feb 22, 2018 8:27 pm

Thanks for taking the time to write all that David, very useful, its what the Forum's for :thumb

Just one query arising: is the probe applied from the front ie. on the overlay, or the rear (substructure)? I wonder if with thin overlays (the ones on the 517 seem to be about 5thou) it might mark the surface?

Steve

User avatar
David B
Posts: 1247
Joined: Sun Jul 20, 2008 5:30 pm

Re: The Adventures of an RSU Virgin

Postby David B » Thu Feb 22, 2018 8:38 pm

I prefer to apply the probe from the 'hidden' side if I can but this is not always possible or just plain awkward. It is not really something that is that important unless you have the voltage wound up. Most work, I have found, can be done at 2v but then I have not used a metal plate which can take a lot of heat, in which case you might need to bump it up a bit. Sometimes, you get a black mark or a reddening of the brass, very occasionally a scorch mark. Keep the probe tip clean. Jol mentioned elsewhere keeping some card available to wipe the tip on.

Marks I have found to come off with a scratch brush or similar and even if they don't disappear completely, get covered with paint and don't show. As recommended, try it out on some scrap first.

User avatar
TonyMont
Posts: 98
Joined: Mon Jul 28, 2008 2:19 pm

Re: The Adventures of an RSU Virgin

Postby TonyMont » Fri Feb 23, 2018 12:48 pm

Hi,
I have not used my RSU extensively but did find burn marks to be a problem, on asking about this at a demonstration I was told to apply the probe at an angle to increase its surface area, which helps, also a third layer of clean brass or nickel silver placed on top of the joint can eliminate the problem.
Regards, Tony.

User avatar
David B
Posts: 1247
Joined: Sun Jul 20, 2008 5:30 pm

Re: The Adventures of an RSU Virgin

Postby David B » Fri Feb 23, 2018 1:54 pm

TonyMont wrote:I have not used my RSU extensively but did find burn marks to be a problem,


This suggests you might have been using too high voltage. Getting the right voltage is down to experience, so start low. If the voltage is too high, then you are quite likely to burn, melt, even evaporate a part. Starting on a low voltage, you may find nothing happens, so go up another step and try again.

User avatar
steve howe
Posts: 610
Joined: Sun Feb 01, 2009 10:16 pm

Mystery RSU

Postby steve howe » Wed Feb 28, 2018 3:07 pm

Can anyone help me identify this RSU please? it came my way a while back with other items from a late friend and I've just (in the light of this thread) dug it out to have a play. I thought it might be an early London Road Models version, but a search on Google images reveals nothing similar. I haven't tried it out yet as I need to get a new carbon probe, the probe handset supplied has a collett and a brass inner bush with what looks like a 3mm diameter hole.

RSU.JPG
mystery RSU


Steve

User avatar
Jol Wilkinson
Posts: 806
Joined: Mon Jul 21, 2008 7:39 pm

Re: The Adventures of an RSU Virgin

Postby Jol Wilkinson » Wed Feb 28, 2018 5:41 pm

Steve,

it isn't a LRM unit, nor does it look like any of the usual ones, except!

The original Exactoscale unit was, IIRC, supplied as a bare transformer. DIY options included a case. The probe also looks like the Exactoscale type which had a modified co-ax plug as the carbon road holder, so could it be one of those?

Jol

User avatar
Guy Rixon
Posts: 709
Joined: Sun Mar 27, 2011 6:40 pm

Re: The Adventures of an RSU Virgin

Postby Guy Rixon » Wed Feb 28, 2018 7:03 pm

Yes, it's an Exactoscale unit. I had one in service for a while. Very high power w.r.t to other types, so much so that it melted the soldered connection in its probe. That's when I retired it in favour of an MMS unit. I still have it in the loft and should dig it out and refurbish. It's probably OK if one ignores the thermonuclear output and uses the other two.

PS: the three red sockets on the front are for low. medium and high outputs, although "conventional", "tactical" and "strategic" better captures their nature. The low output might be on the left and the high on the right, but these things are user assembled and that order assumes an owner whose preferred writing-system system goes from left to right.

The toggle switch gives lower and higher output for each of the three sockets, so there are six settings of which the lower four are probably the only useful ones for fine work.

The problem with the probe is not the coax connector, but the brass ring inside the probe handle. The positive lead is soldered to the ring and the carbon is supposed to be a tight enough fit in the ring that it makes good contact. If the carbon is a bit undersized, then it makes poor contact and most of the voltage is dropped across the carbon-brass joint. The heating can be enough to melt the soldered connection to the brass ring; also to remove your finger prints if you don't let go quickly. If I were to have another go, I think I would drill the probe handle and the ring and install a set screw so that the carbon was firmly pressed against the ring.

User avatar
steve howe
Posts: 610
Joined: Sun Feb 01, 2009 10:16 pm

Re: The Adventures of an RSU Virgin

Postby steve howe » Wed Feb 28, 2018 8:25 pm

That's really useful, thanks Guy. I'll have a go at modifying the brass insert. Might need a bit of practice if the thing still works!

Steve


Return to “Tools and Techniques”

Who is online

Users browsing this forum: No registered users and 1 guest