Welded/fabricated engine ‘castings’

[Mick BaileyParticipant @mickbailey28509]

<p style=”text-align: left;”>I started building a vacuum engine many years ago and constructed the main frame from welded steel plate. The welds were full thickness and then ground and radiused. The finished result was better than I hoped for, with just a few surface imperfection that wouldd be filled with JB Weld.</p>
At the time I used MMA but now have a MIG setup that would be an improvement. I suppose TIG would be even better.

It strikes me that this is an inexpensive method to use for a medium size model, but searching for pictures of examples made by others doesn’t turn up anything.

I was thinking of using this to make up the main bed, water jacked etc for a hit-miss engine. Has anyone here used this technique?

[JasonBModerator @jasonb]

I’ve been known to do a bit although my welding (stick) is not particularly good. 1/3rd scale Ruston Hornby. Smaller details like bosses on the feet and bearing housings were silver soldered on to single pieces of steel before welding and dressing. Final machining as a “casting” after all the hot work.

1/5th scale casting for IHC vertical

1/4 Scale welded version

Steam engine A frame and box bed. I had the main parts of the A frame laser cut then bent and welded them

Bed and crankcase welded again some detail soldered on and there is a bit of carbon arc brazing in there too. cylinder and hopper soldered.

[JasonBModerator @jasonb]

Hopefully this will take you to the album with the Ruston photos in it which shows the stages from pieces of plate to completed “casting”

There are a couple of published hit & miss engines that are mostly welded fabrications, the Finney which was in Model Engine Builder Magazine and the J & E which was and may still be about on the net.

J & E Plans

Reg Ignol’s site used to have several of his fabricated engines but the detailed images have not been archived so I won’t post a link

[Mick BaileyParticipant @mickbailey28509]

That’s impressive work and just the thing to rekindle my interest in continuing with this route. I wish now that I’d kept up my BOC oxygen rental for my oxy-propane setup. I think that Sifbronze would be even more straightforward than welding and is easier to create smooth fillets with a minimum of grinding/filing.  It’s the one thing that I really miss. However, as I now have a decent MIG setup I’ll settle for that, though recently I’ve been doing a lot more MMA and it’s a little easier to reach inside awkward spaces.

I did wonder though if there’s any need to stress relieve the fabrication. Perhaps if the major machining and shaping is performed prior to welding any distortion will be corrected upon final machining, assuming no major cuts or reshaping are needed.

Another thought is to cut out the parts with a plasma cutter and templates. My 30A unit works quite well up to 5mm, and with 3mm and below the cut only needs a superficial cleanup. It’s certainly quick and fairly accurate. What I like about a fabricated  construction is that it’s a rapid way to get the main superstructure built at a fairly low cost.

[JasonBModerator @jasonb]

I tend to think of fabrication as making your “pattern” from metal and sticking it together with weld/solder/epoxy rather than wood glue. You then skip the casting part of the process. So are left with a fabricated “casting” that can then have the critical surfaces and features machined.

I’ve not found the need to stress relieve anything I have made as the final machining operations after fabrication are only removing a small amount of material any movement is unlikely to happen. I’ll typically leave 1mm on a surface which is a lot less then you tend to have to remove from a casting which can be 3mm plush draft. But if you had the option to heat the whole welded fabrication then it would do no harm.

It is possible to braze with MIG and also tig with the right wire, maybe not quite the same method as building up a fillet with oxy but I would have thought a few runs of braze would build up a fillet that could then be blended and smoothed a lot easier than welding. Also less chance of geting it too hot and having the pool of braze drop on the floor.

Plasma and a linisher or sanding/grinding disc in an angle or air grinder would soon clean up the parts, weld is a bit more forgiving than silver solder if there is the odd small gap.

 

[JasonBModerator @jasonb]

Couple of old threads on HMEM that inspired me with the welded fabrications.

1/2 scale Advance Rumley

1886 benz

[Dave HalfordParticipant @davehalford22513]

One problem with mig welding is the result is harder than the parts though it does let you recover mistakes with a blob of of weld and a trip to the grinder.

These parts were 30a Plasma cut from 3mm steel

Assembled as a geared drum below. The small inner ring was welded in 4 places to the rear geared outer disc

The thin large ring was bolted and glued before gear cutting to give 5mm gear width

No distortion occurred.

If you follow good mig welding practise it will be fine. If you start at one end and just weld to the other things will move due to the shrinkage.

In full size (six foot dia) Burrell cast these, how they kept them flat I have no idea.

[Nick Clarke 3Participant @nickclarke3]

Not quite the same model but in volume 139 of ME the Late Don Young did a short series on fabricated locomotive cylinders.

[DiogenesParticipant @diogenes]

I believe Find Hansen fabricates all his models, i.e. I don’t think he uses any castings at all..

https://www.youtube.com/@boksermotor/videos?view=0&sort=dd&shelf_id=1

[noel shelleyParticipant @noelshelley55608]

Unless your MIG has ample power you may have welds that will look fine but have no strength, MMA if it looks bad it will be ! Minimum 180A and not a cheap one for this sort of work. BOC accounts the rental is by the month so may not be too bad, and if your used to brazing and still have the gear it might be worth going back to it. If you have oxygen then with a clean propane nozzle you can cut thick plate with ease, 1/2″ and 3/4″ are no trouble.  Noel.

[JasonBModerator @jasonb]

As I said my stick welding is not good but how strong does it need to be.?

My engines run without falling apart but I would not want to weld up anything on my cars.140A Machine Mart inverter jobbie.

[noel shelleyParticipant @noelshelley55608]

Both BOC with the Autolynx and Migatronic both saw fit to give 180A for either 0.6mm or 0.8mm wire for the repair of vehicle bodies, MOT welding. 3mm is fine and IF you know what your doing even 6mm but it requires more skill than some would realise.  For the OP I would say stay with MMA, You will need Argon for MIG or TIG. Gasless MIG I would not even consider. My £60 inverter for MMA is unbelievably good, almost as good as the £550 one, but the 375A MIG machine is best and only cost £25, the gas costs me more !

Jason, Your welds look passable and as you say they hold, that’s  all that matters. MIG can be very dangerous in unskilled hands, trust me, I know ! As for stresses, if the “casting” is not to big put it in a bonfire or living room grate and then leave buried in the ashes till cold. Noel.

[Grizzly bearParticipant @grizzlybear]

Jason,

Your fabrication is a work of art.

I’ve always admired them.

You are thinking outside of the box, or in your case, the casting.

Bear…..

[Mick BaileyParticipant @mickbailey28509]

My MMA machine is a 180A Peerless unit I bought new in Australia. It performs well with 2.5mm rutile electrodes. For MIG I use argon mix with a modified SIP migmate. The cylinder is rental-free but the gas still works out to be quite expensive. A plasma cutter repaced the oxy-propane setup which was mainly used for cutting sheet or thin plate.

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