Solder repairs to Mazak Triang/Hornby loco chassis

[threelink]

I have a damaged chassis for a 1970s Triang/Hornby Duchess. Previously I have repaired damaged chassis successfully with superglue or epoxy. On this one a solder repair would be preferable for reasons of electrical continuity but I do not know whether mazak will accept solder. The repair will necessitate the use of a miniature blow torch rather than a soldering iron and I am concerned at the risk of melting the mazak, causing further damage. Any advice or tips as to the best way forward will be gratefully received .

[Topcat2018]

I'm not an expert on this, but as I'm sure you know Mazak is an alloy of magnesium, aluminium and zinc with a small proportion of copper, so I don't know if it could be soldered successfully using tin/lead (I still use this as it's the best) or lead-free solder. I'm 74 and have been soldering since I was 14, and I haven't died of lead poisoning yet.

Whatever the case I think using a blowtorch on dodgy Mazak is risky.

My suggestion would be to drill a small hole in each half of the chassis, make the mechanical repair using epoxy then make the electrical connection by screwing small self-tapping screws into the two holes with a washer under each head. Wrap some wire around the screws under the washers before screwing fully home.

I would always use epoxy as it allows accurate positioning of the broken parts before the glue cures. With a broken chassis the break will usually have rough edges that will provide a good key. Epoxy does not have good peel strength on smooth surfaces.

[Rog RJ]

You don't want tin/lead solder in contact with mazak as it's believed that lead contamination is the cause of mazak rot.

Drilling and tapping would be the best option IMHO but a self tapping screw into a drilled hole should work.

[96RAF]

Don’t torch magnesium as it is impossible to put out once alight. It was the main ingredient for incendiary bombs and flares. You may get away with JB Weld, an American product for ‘welding’ anything metal but it has poor strength properties.

[threelink]

Thanks all for your comments. The problem is that a previous owner clearly had a problem with the pony truck retaining screw threads stripping. Rather than drilling and tapping for a slightly larger screw, a huge hole was drilled into the chassis block and the pony truck screw was set into a sea of epoxy in the hole. The screw forms part of the electrical circuit carrying power to the tender drive by way of the pony truck frame. The epoxy rendered the pony truck electrically dead and also made it impossible to remove the screw. This in turn made it impossible to remove the retaining plate holding in the driving wheels. Having removed all this mess (including all the epoxy) by brute force I am left with a chassis with a great hole in it, which I need to fill in a way that will allow insertion of a new pony truck retaining screw that will be electrically conductive. Soldering in a suitable nut seems the only way forward. The alternative is to use ordinary epoxy, leaving the pony truck electrically dead, and to route a wire from the chassis to the contact on the pony truck, but I would prefer not to go down this route if possible. The problem might be solved if I could find an electrically conductive epoxy. Such does exist but seemingly only in large quantities costing hundreds of pounds.

[ColinB]

Have you looked into threaded sleeves, I assume the hole is too big for a helicoil.

[Topcat2018]

@Threelink

I didn't realise from your original posting that you had a hole that needed filling, thought you had a broken chassis.

Try Amazon:

https://www.amazon.co.uk/Electrically-Conductive-Adhesive-Temperature-AA-DUCT/dp/B00EPYCIGQ

And similar listings on Amazon.

[ntpntpntp]

Brass rod to fill the hole as an interference fit, then you have something you can drill and tap to suit a screw.

[Going Spare]

If you have one of the early chassis with a metal wheel keeperplate, that also is extremely prone to disintegrating with rot and is irreplaceable.

[Topcat2018]

@ntpntpntp

If you try to force fit a brass rod into a chassis whose strength may already be compromised you may end up breaking the whole chassis in half. I've had a Duchess class chassis snap in half merely by taking it apart. It looked fine but it had Mazak rot.

[The son of Triangman]

Personally I would treat the chassis as scrap. It would be easier to simply replace. If it's the 1977 onwards version with the cast wheel retaining plate be careful as the plate can be fragile. The wheelsets simply drop out, so can be reused. If you can't get a replacement then tap the hole and fit a brass threaded bush into the chassis with a centre hole tapped out to 8ba. If it has mazak rot in that area, then it will fail again, check the hole area carefully, cracks in the paint are a sure sign the zinc pest/mazak rot is there.

[ColinB]

Which model is it, tender driven or loco driven with the old Triang motor. If it is tender driven I will look through my old bits to see if I have a chassis. I can't remember whether I sold them when I converted my Duchess to the later loco driven chassis.

[Going Spare]

The Duchess was Ringfield tender-driven until the introduction of Chinese loco-drive models with a can motor. The chassis block was common to all UK models and early Chinese tender-drive loco's.

[81F]

Just to let you know, I've tried to solder wires to 1970s and 80s metal chassis and it just wont work.

[Rana Temporia]

Where is it broken? I doubt you’d get enough heat into the metal using solder, brazing it together might work but it’s something I am unfamiliar with and if the chassis has broken through being brittle then you might cause more damage or have further breaks. Maybe better to look for a damaged loco with an intact chassis block. I think the wheels drop out of this chassis once a plastic plate is removed so no need for re-quartering.

I got a complete loco with damaged body for £5 not that long ago and the chassis for loco and tender now run around under a GBL streamlined duchess. I had to file the cylinders down quite a bit to get them to fit the body. The long term plan is to paint it BR green as a neverwazza.

[threelink]

Grateful thanks to all for your comments and suggestions. Happily 8the chassis is free from rot. The only problem is the large hole dug in it for the previous repair attempt. The chassis is so weakened that any attempt to force fit anything or to drill into it further is likely to damage it further. I have designed a fitment to enable reattachment of the pony truck. The difficulty is in securing it to the chassis. My first idea was to invert the chassis, stand the fitment in the hole and flood the hole with solder. It seems that this will not work. I shall continue to investigate the availability of electrically conductive epoxy because that should work. Once again,my thanks to all.

[Topcat2018]

@TH

Did you manage to find any suitable conductive epoxy on Amazon, as I suggested?

[threelink]

@Topcat

I found a number of possibilities but on reflection decided to go for the soft option using standard epoxy and route a wire from the chassis to the connector on the pony truck drawbar. The main reason was that the pony truck itself was also damaged and I doubted my ability to effect repairs to both chassis and pony truck in a manner that would preserve electrical continuity. Grateful to you for your input.

@CO.

Thank you for your offer. If you have a chassis available for purchase I would be interested because I have picked up a whitemetal streamlined duchess body and need a chassis for that. They are like buses; none for ages and then 2 come along.

@RT

I like the sound of your neverwazza.

Thanks to all contributors for your ideas and suggestions. I never cease to be amazed at the breadth of knowledge available on this site and by the generous willingness of contributors to share it.

[Rana Temporia]

Without seeing the chassis it’s a bit difficult to say but from memory this chassis was originally designed to take an X04 type motor which means there may be some holes available to use without excessive drilling. Is it possible to fill the hole with Chemical metal (I think this is non-conducting) rather than solder which should hold both parts of the chassis together permanently and using an available hole, tap it to 8BA if not already done and use a standard Tri-ang bolt to hold a wire in place at one end and similarly drill/tap at the other ensuring electrical continuity through the chassis. If you are anything like me you’ll have plenty of correct screws and brass eyes to make the wire and fit it.

The metal isn’t too difficult to drill, I did one by hand during an online meeting earlier this year. It helped me to concentrate which was a win-win!

[threelink]

Yes, RT, the chassis does have provision for an X03/4 even though the loco is tender driven. I do not want to weaken it further by more drilling in the area of the existing hole so shall invert it, stand the fitment I have made in the existing hole and flood it with epoxy. In effect this will leave a nut buried in the epoxy into which the pony truck securing screw will fit. A length of brass tube soldered to the nut will provide space for the spring that surrounds the securing screw and for the screw itself. A narrower diameter brass tube over the upper part of the screw thread will replicate the plain shank of the original screw. The pony truck will be electrically dead so I shall run a wire from the chassis to the connector on the truck. I might have to drill the chassis where there is more meat on it so as to screw on a tag for the wire but otherwise will not have to risk further damage to it. It's a joy to resurrect an otherwise dead loco, a joy which I think you also find.

[P-Henny]

Did you manage to find any suitable conductive epoxy on Amazon, as I suggested?

 

 

Just out of interest I looked on Amazon as I had never heard of conductive epoxy. Out of the small number of hits, I found one based upon Gold that was priced at £2,600 and another based on Silver at just over £1,000. The conductive epoxy might sound like a good idea but not really practicable at those prices. I also looked on ebay, and found prices still to be in excess of £50 but these were not Gold or Silver based in their ingredients.

[threelink]

@PH

Yes, it is expensive stuff, which was a factor in my decision to go for an alternative solution. There are conductive adhesives available at much lower cost but in very small amounts but I am not sure of their suitability for this particular repair - they are intended for pcb work. It's annoying because I distinctly remember many years ago having a tube of metallicised filler that would have done the job. I think it was sold under the "Plastic Padding" brand name but I have not seen it for decades. I have no idea what it comprised but it certainly set rock hard and it was definitely conductive. It probably had some noxious ingredient prohibited today.

[Topcat2018]

@TH

The link I gave you to Amazon takes you to a 2.5 g pack of silver conductive epoxy for £18.

When you are on the page, if you put in the search term "electrically conductive epoxy silver" it brings up several other inexpensive options if you sort by price, low to high.

[threelink]

Hi Topcat,

Yes, I saw the packs you mention but even at the figure of £18.00 for 2.5 g, the cost took the repair over budget - it is after all an old loco of no particular merit or rarity. I have a strictly enforced, self imposed average budget of £12.00 per loco (recently raised from £8.00). So far I have amassed over 100 without going over budget. Some are horrendous mongrels but all look well under a coat of paint, run quietly and smoothly, are controllable down to a crawl, are fitted with scale couplings and other detail and, in some cases, with finer wheelsets. Nowhere near the superb r-t-r models of today but perfectly acceptable to me and likely still to be running long after I am gone. The info you provided has been filed away for future reference in case I have a similar problem on a real collectors' item - they do crop up from time to time, even at £12.00 a throw. Thanks again for your input.

[Topcat2018]

Hi TH,

Didn't realise your budget was that tight - lol!