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Soldering a tender

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Phil H103/12/2019 21:09:01
311 forum posts
31 photos

I am trying to select the best tools and techniques to complete the brass body of a 'Betty' 3 1/2" gauge, locomotive tender.

The sheet brass body sections have already been assembled in accordance with the instruction manual. Note that the manual and drawings show 1/4" x 1/4" brass angle attached to the inside of the body using 1/16" diameter snap head rivets. The rivets have their heads on the inside and countersinks on the outside plate. A large number of countersunk screws are used for the top plates and to hold the body to the sole plate. This means that the current tank work is already quite strong but will probably leak like a sieve.

The manual goes on to suggest the use of a soldering iron rather than a torch to seal up the tank. It states that a torch will probably buckle the nice flat brass platework but my guess is that LBSC probably had an old traditional flame heated soldering iron in mind.

So, this is quite tricky because the sections or angle and the rivets can not be tinned i.e., they are already fitted and I would prefer to have a go at solder rather than some kind of epoxy or petrol tank sealant.

Anybody out there done this successfully with an iron and are there any good tips?


Phil H

Buffer04/12/2019 08:45:36
165 forum posts
46 photos

Phil I have just finished soldering up my 5 inch tender. The best advice I can give is to clean all the joint areas, I use a blue garyflex block from cousins. The flux I use is fluxite in the green tin. I think the fumes from this might corrode machinery so keep the door open and maybe cover any machine etc. Get an old small brush so you can spread it easily along the joints and I don't think you can use too much. The most important thing I found after warping the sole plate with a gas torch was to use a lead based solder as it melts about 50 degrees lower than the non lead variety. You can buy it from rs components about 1.2mm diameter and about 250 gram roll. You will need a business account to buy it or find someone in a company to get it for you. The lower melting point makes a huge difference in the amount of heat required and the chances of warping. The second thing I did was use an electric hot air gun to pre warm the tender paying particular attention to the bit I was about to solder. Heating the inside of the corner and the outside. I found it made the heating from the soldering iron much quicker and easier and it also helped in making the solder flow nicely. I used a very large soldering iron of over 100 watt. Hopefully if you get the joints clean fluxed and hot enough you should have no problems. One last thing I did was prop the body at 45 degrees with the corner I am about to solder at the bottom and level. This way the solder doesn't all run down to the sole plate but stays on the angle along its length.

hope this is all clear if not just ask and I will send pictures or explain more.


John Baguley04/12/2019 09:09:25
467 forum posts
50 photos

When I've soldered tanks etc. I've used one of the lower melting point solders from Carrs such as the 143ºC stuff. You can get them with a melting point down to 70ºC. They are available from Phoenix Paints amongst others. Not cheap though but you don't need a lot if the joints are close fitting. Some of the solders used to contain Cadmium which made them flow very easily but don't know if they still do?

I've always used a needle flame torch for heating with no problems but you do have to be careful not to overheat the metal and distort it. Using a low melt solder definitely helps with that.


Phil H104/12/2019 09:33:49
311 forum posts
31 photos

Rich/ John,

Thanks very much for taking the time to answer and thanks for the tips.

I notice that low temperature lead solder still seems to be available on-line. I'll have a go at ordering some and I'll also take a look at Phoenix.

I like the heat gun tip to pre warm the metalwork. I would imagine that reduces the risk of distortion significantly and it might help the soldering iron? I will enlist a willing volunteer to use the heater whilst I use the iron. It will be a good training scheme for when I need two propane torches on the boiler.

One of my main concerns was getting a soldering iron with sufficient power to do the job but I also notice that there are some 100W + irons available on-line.

Pictures will follow.


Phil H

Simon Collier04/12/2019 10:41:49
359 forum posts
56 photos

I did not have a happy time trying to solder up my tender kit. I used tin/ lead solder and Bakers fluid flux. I borrowed a 300 watt iron but did not have much joy with it and mostly used flame. I learned to clamp brass square bar to the plates to prevent warping upon heating. It leaked like a sieve and just days ago, I used petrol tank sealant to seal it. Thankfully this worked and completely sealed the tank.

Phil H104/12/2019 13:37:39
311 forum posts
31 photos


Thanks for that - I was thinking about asking people about their experience with the laser cut parts for some other future project. I do have a central heating, butane style torch that I could use but I would like to try the iron first. If an iron has worked on a 5" gauge tender - it will surely work on a 3 1/2" engine.

Also, I can always fall back to the petrol tank sealant or I was thinking of the higher quality bathroom type silicon sealants if the soldering doesn't work.

The current plate work strips down to the sides, top and sole plate - so there is a good chance I can thoroughly clean the parts before trying to solder them.

Phil H

Buffer04/12/2019 14:26:01
165 forum posts
46 photos

Phil If you can get your joints apart I would tin them first. get them nice and shiny then flux solder and wipe the solder away when its still hot and runny. You will then have a nice thin solder coating on both sides of the joint. You want to wipe the excess off so your joints go back together nicely. You should get no distortion as long as the volunteer keeps the hot air moving and then just blasts the bit your doing as you do it.  When youve done it I will show you a great tool for cleaning up the joints on the outside.  

Off topic a bit but I used oxy acetylene on my boiler after it had been pre heated with gas torches. Again this was no problem and works very well if you have the use of this kit.



Edited By Richard brown 1 on 04/12/2019 14:32:30

Phil H104/12/2019 15:16:42
311 forum posts
31 photos


I can separate the top from the sides and the soleplate from the sides but the brass angle is attached to the sides with 100+ 1/16" rivets. I might get them apart but it would make a hell of a mess. I'll take and post some pictures.

The boiler..... I like the idea of oxy propane but I will try using two decent propane torches first. I've seen a thread on one of the other sites where a chap has very recently made a 5" gauge Britannia boiler with 2 propane torches. He had to resort to oxy propane for a couple of leaks. I think I will also see what my local club can offer when it comes to the boiler.

Phil H

Buffer04/12/2019 16:01:21
165 forum posts
46 photos

Phil if you can get it off the sole plate thats great news as you should have no problem to get some emery or a garyflex along the entire length of the edge of the angle and the sides and get all the edges really cleaned up. Your then half way there.

RMA04/12/2019 16:01:48
245 forum posts
4 photos
Posted by Richard brown 1 on 04/12/2019 14:26:01:

When youve done it I will show you a great tool for cleaning up the joints on the outside.


Edited By Richard brown 1 on 04/12/2019 14:32:30

Would it be possible to post the details for all to see. Thanks

Brian Baker 104/12/2019 17:00:22
129 forum posts
24 photos

Greetings Phil, would it not be worth using epoxy to make them water tight. I have done this several times & it works well. Just get the brass as clean as you can with say a small wire brush in a Dremel, and paint it on. the brass catalyses the reaction, and it needs to be kept warm. Avoid the rapid set epoxy, it's strength is lower than the long time set material

Boat chandlers sell a suitable product.


Brian Baker

Phil H104/12/2019 18:53:50
311 forum posts
31 photos


The pictures as promised.

This is the tender as I received it. You can see that it is virtually complete (90% ish) but has a few minor issues such as the rust on the frames and the body of the tank work needs to be sealed - possibly with solder - hence this post.no4.jpg

Phil H104/12/2019 19:15:07
311 forum posts
31 photos

A few more pictures of the platework showing the internal riveted angles, the sole plate with a huge number of countersunk holes and the removable top section. The platework has been put together quite nicely in my opinion. It just needs a little bit of tidying. Note that any soldering will need to be done with care to prevent loss of the already soldered half round beading.

I will experiment with the removable top to see how it goes. It might not be so clear from the pictures but the pump access hole surround is a little bit twisted. I know that I am being a bit pedantic because you can hardly notice the twist but I think trying to straighten it out will be a good starting exercise.tender 1 - copy.jpgtender 2 - copy.jpgtender 3 - copy.jpgtender 4 - copy.jpgtender 5 - copy.jpg

tender 6 - copy.jpg

Phil H104/12/2019 19:24:46
311 forum posts
31 photos


I assume the epoxy from the boat chandlers is a special brass product? I ask because I think I have seen other posts about the lack of adhesion between brass and various other products e.g., glues/ paint etc?

As you will note from the pictures, the existing structure should be very strong with all the rivets and countersunk screws so I don't have a closed mind to clever products that will probably save time and energy. I guess I just like the idea of the metal solder option.

Phil H

Buffer04/12/2019 21:05:43
165 forum posts
46 photos

Here is is the little tool i use to clean up after soldering. Its a little mini scraper made from a piece of 12mm wide x1.5mm thick carbide scraper blade silver soldered to a steel rod. A flat edge is put on it just like any other scraper with a diamond wheel and then run it along the joints. It works very well on flat and in corners. The solder comes off as easy as anything in nice little curls and as it's so small it leaves very clean corner joints. img_5750.jpgimg_5758.jpg

Phil H106/12/2019 13:59:43
311 forum posts
31 photos

Richard, nice scraper. I might grind up an old screw driver or a piece of HSS to do the same job.

Latest - if anybody is interested?.....;

I decided to leave the access hole to the emergency pump alone. After cleaning with emery cloth etc, the existing soldered joint is quite nice so I levelled the top of the hole surround with a file and polished the plate. It now looks quite nice.

I did try some lead solder (180 degC stuff) on the front plate of the tender tank using a DIY, central heating type flame torch on a small flame. The good news is that my technique to clean the rivet heads and angle using emery and a Dremel went well because the solder formed nice fillets. The bad news is that even with very careful heating, the plate did distort significantly. Luckily, this particular plate is only about 61/2" wide X 3" and it was quite easy to straighten it back out using wood and a few taps from a mallet.

So, for my next trial, I will ditch the small torch, buy some lower temperature solder and a big soldering iron and try again. I was lucky with the front plate. If I distort the tender sides, I doubt if I will be able to retrieve them.

Phil H

Stuart Smith 506/12/2019 15:57:32
116 forum posts
25 photos


have you tried a mini blowtorch like this one: Mini blowtorch

I don't know if it would work, but I used one to solder the brass body for my 16mm scale loco. Obviously a lot smaller, but it might be ok for what you want to do.


Phil H106/12/2019 22:24:25
311 forum posts
31 photos


i have considered a micro torch but going back to previous posts, Richard has recently built a 5" gauge tender using a hot air gun and a soldering iron - so I will have a got at that method first. I do like the look of the micro torch though.

Phil H

Buffer07/12/2019 07:36:36
165 forum posts
46 photos

Phil I used a dremel micro torch and I have distorted sheet with that. I think they just have too much heat concentrated on two small an area. I am sure the trick to avoid warping is to get the whole lot upto a decent temperature. One guy in our club even put his in the kitchen oven to get it all warmed up evenly and it worked. Regards Rich

Brian Baker 107/12/2019 08:09:14
129 forum posts
24 photos

Greetings Phil, no, the epoxy is mostly used for repairs to wooden & GRP boats, and chandlers are the easiest places to find it. I have never tried Araldite for the job, but I am sure the normal stuff will work OK, except you will need a few tubes.

I have used it on several tanks, but you need to clean & rough up the surface first, I used medium emery paper, dead smooth makes it harder for the epoxy to stick. I think I have seen a grade of epoxy especially for metal, but the material I use comes straight from my boat repair stock.

If you fancy solder, then do it, and when it starts to leak, after a while, use the epoxy to seal it, that's how I started using it on an A3 tender.



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