welding small thin pieces?

[havoc]

I want to build a gauge 1 loc with bogies. Went to visit a real one, and those bogies are made from welding a lot of pieces together.

Now, my first tought was to make them by silver soldering all those pieces. But there are just to many of them, and some very small. So holding everything to gether becomes too hard. Also I fear that I'll need to solder in several steps, and I don't trust myself not unsoldering previous work.

Next tought was making an inox frame to hold everything together (a whole bogie or a single side), flux everything, put snip of silver solder at the joints and solder everything in one go by making an oven. But this seems just as hard!

Last idea was to weld the basic frame together. Then silver solder the other pieces on it. But can you weld a steel piece of 1mm thick to another of 2mm thick to form an I beam?

As illustration a pic of what it looks like 1:1:

[baggo]

Hi Havoc,

Unless you're very good at precision welding I think you will be struggling to weld components that small! Also the welding fillets will probably be much too large unless you are prepared to grind them all down afterwards.

There's no reason why you can't silver solder it all together using the step method with different melting point solders. Use a high melting point solder for the first operations, a lower for the second, and the lowest for adding the final details. If some of the smaller components are non structural and just cosmetic you could use soft solder for adding these. However you decide to doi it it's going to be a fiddly job!

John

[steamjohn248]

why not make a pattern and get someone to do some lost wax castings for you

[havoc]

Had a feeling this would be the outcome. No-one seems to like talking about welding this kind of small parts.

Casting might be a solution, but 1mm is narrow. And finding a foundry willing to do this might be even a greater challenge than weldeing! The club cannot even find a foundry willing to cast 200 wheels.

I'll try the brazing with a support structure. Unless there are other ideas...

[davidimurray]

Why not machine them from solid?

Cheers

Dave

[SteveW]

Havoc,

It occurs that with 1 & 2mm steel you are in the car body territory and either MIG or TIG welding. I know it can be done because a number of my old cars were given a new lease of life this way.

You may be able to hire/borrow the necessary MIG kit to stick your bits together. It's certainly worth a try if you are intent on welding. You may also need a Dremel to tart up as necessary.

The big problem with any form of welding is distortion. Local heating causes local expansion. You may need to preheat the whole job to approaching silver soldering temperatures to avoid it. So why not focus back on a silver soldering.

If you make a jig to hold all the bits then whack it all in one go. Try profiling bits with a couple of pegs and locate them in holes on the main substrate.

[havoc]

Machining would be an option, but lacking machinery to do so is another problem. Neither do I feel confident of machining everything away and let a 1mm side stand. Doesn't look easy.

If preheating to those temperatures is needed, then silver soldering seems to be the way to go. That jig looks more promising then. Maybe make the pieces fit like a jigsaw so they cannot move.

Okay, thanks for the input, I'll explore that way a bit deeper.

[steamjohn248]

You dont need to find a foundry to get lost wax done. Most decent art colleges teach lost wax as part of the course. My daughter (now a lecturer and far too grand) used to make a few bob on the side as a student doing the most amazing bits using this process. Also there are several people in the Model Engine supplies world who do this and advertise in M.E. 7 1/4" Soc Mag etc.

[havoc]

Well, there is a valve making company a bit further, maybe they could cast some things. It would be brass but that would be no problem for a gauge 1 model.

[ron]

Havoc, I've had a lot of experience using MIG welding for classic car restoration and my advice would be don't, it's too hot, leaves too big a weld and causes distortion problems, TIG might work but the kit is expensive and takes a lot more skill than MIG to master.
Ron

[Tel]

I agree Ron. Slotted & tabbed fabrication & silver solder would be the way to go

[jackrae]

This won't give you the answer you require because I cannot remember the guys name - but it might trigger someone else off.

Firstly making all the bits with slots and tabs is definitley the way to go since these will hold the parts in correct alignment until they are soldered. Problem is making the slots and tabs accurate enough to do their job.

At the recent Harrogate model exhibition there was a guy displaying laser cut boggie frames. What was particularly "exciting" was that he made maximum use of metal by cutting all the little fiddly bits in between the bigger ones. He also cut all the slots and tabs necessary to permit the fiddly bits to fit into the main ones so that they could be fully assembled then silver soldered in one go.

All he required was a drawing of the various bits showing what fitted where and he worked out where tabs/slots were required to permit fabrication.

When I'm back home this weekend I'll see if I can find his name, but by then some other reader may have already provided it for you.
regards
jack

[SteveW]

Jack, All,

What you're describing sounds like a water cutting process. There's a thread here somewhere from early January that explores the process at bit. It's great but not cheap.

There was a guy at Sandown MEX selling skelton Spitfire kits in brass all cut by water jet.

[jackrae]

No Steve,
It was definitely laser cut because I asked him if they'd been water cut. He said that water cutting was more expensive and laser produced a finer finish. You could just see a slight blueing at the cut edge where the heat of the laser had warmed the metal.

He had some assembled fabrications on display, some of them extremely complicated and they really looked the part.
Jack

[Tel]

Let's see if this works.

How to utilise a sheet of steel - Jan-Eric Nystrom's current project, the green are for laser cutting, yellow for water

[jackrae]

Hi Tel
Great image and just like I say at the show

Havoc
Have now managed to find the name of the guy exhibiting - no connection or commercial interest - just enthused by the service he offered - any design catered for, just send a drawing of what you're trying to do and he'll tart it up and provide a quote.
details as follows :

www.modelengineerslaser.co.uk
Malcolm J High
Miller House
Main Street
Hampole
Doncaster
DN6 7ET
01302-721611
regards
Jack

[baggo]

Although it may be more expensive I think water jet cutting has some advantages over laser. The main problem with laser cutting is hardening of the material along the edge of the cut due to the metal actually being melted rather than cut cleanly. Perhaps not a problem with thin materials but can make thick items such as coupling rods very difficult to clean up and finish due to the glass hard surface left by the cutting. There's also the possibility of distortion with laser cutting due to the local heating.

Not sure about the accuracy or finish of the cut with laser compared to water jet but one firm who specialise in water jet cutting quote a cutting tolerance of +/- 0.127mm over 2.5mtrs with a choice of 5 finishes.

If I ever get around to building the Black Five I think I will get a quote for water jet cut frames etc as I don't fancy cutting them by hand!

John

[havoc]

Thanks for all the info guys.

I followed the Nystrom thread on the "other" forum. Most informative.

Thanks for the address, I'll take a look there. Might be useful one day. But I guess he needs more than a pic of the thing...

To the drawing-board!

[chris vine]

Hi John (Baggo),

The only advantage of laser cutting for frames is that the finish left on the cut edges is more or less to scale!!

C

[Steve M. W]

Hi

We had Malcolm High to our club to give us a talk on laser cutting, you don’t need a drawing just a sketch and some dimensions he will do the rest including tab and slot. He will also do water jet cutting. if you are in the 7.25 Society he has an article in the latest mag.

Steve