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crankcase construction

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Perko713/09/2020 05:04:55
351 forum posts
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OK, dumb question time smiley. I am looking at making an engine based on the ETW design for the diesel roller described in ME many years ago. Obviously castings for this would be about as common as the proverbial. I have read elsewhere many times about cylinder and valve assemblies for steam engines being fabricated from bars and plates and silver soldered together, so what would stop the same process being used for an IC engine? Either silver solder or weld, clean up and machine afterwards. Would seem to be a lot easier, faster and cheaper than machining from solid. Any pitfalls I'm missing?

JasonB13/09/2020 07:14:11
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Engineers Emporium sell the castings but if you want to make from scratch the DX engine is quite simple to fabricate being a very "boxey" shape and could be done a number of ways.

You could silver solder the cross pieces into a open box with it's divisions and then screw side plates on which would make for easier fabrication and assembly.

Or weld up sub assemblies and then silver solder together etc

In both cases but particularly the later I would fabricate a slightly oversize "casting" and then finish machine any faces and bore for a cast iron cylinder liner.

This is mostly welded  with a few bits like the bearing pockets silver soldered on

This one the steel base and open crank area were brazed with carbon arc and the cylinder jacket and hopper silver soldered

 

Edited By JasonB on 13/09/2020 07:49:56

clogs13/09/2020 07:25:20
578 forum posts
12 photos

slightly dif but on the same subject.....

I often looked thru the door of Crossley's Diesels in Manchester.....

huge engines and all crankcases were fabricated from plate.....

then I worked at a company that odered something similar to the above but a complicated hollow sphere

about 5m in diameter from cast steel....walls about 50-60mm thick..they were poured in Norway.....

Brian H13/09/2020 10:14:47
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The crankcases at Crossey Bros would almost certainly be for the 'Pielstick' engines. These were made at the Sandiacre works of Crossley Premier and moved to Manchester when the Sandiacre works were closed.

The fabricated design meant that the same components could be used for a range of engines " built by the mile and cut off by the yard".

Brian

Edited By Brian H on 13/09/2020 10:16:48

Perko713/09/2020 13:13:00
351 forum posts
24 photos

Thanks for those responses, nice work Jason.

I'm reasonably handy with a stick welder but don't have the gear for silver soldering larger objects. Thinking that fabricating with tabs and slots for accurate location, tack weld in position, then full weld, stress relieve, then machine working surfaces should provide a stable platform for further work. Have a friend who does wrought iron work, he has a suitable hearth to heat up largish bits like a completed crankcase to relieve welding stresses, but not for silver soldering.

Early days, probably won't be until next year that any metal is fabricated, but wanted to get an idea that it would be feasible. Will now start designing the bits.

Howard Lewis13/09/2020 14:31:05
3605 forum posts
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The original Paxman Valenta engines that powered the HSTs had fabricated crankcases. Eventually, the locos were re powered as the engines wore out.

It was not unusual for prototype engines to be fabricated, If the principle looked to be viable, patterns would be made for subsequent prototype castings. The Perkins Heritage group have several prototypes with fabricated cylinder blocks.

Howard

Neil A13/09/2020 22:47:54
70 forum posts

The tab and slot location system is very similar to the Steven's Patent for producing fabricated diesels engine crankcases introduced into Britain at the Olympia Exhibition of 1931. Here the firing loads are carried through the vertical plates from the cylinder head to the main bearings without loading any welds. Some of the submarine engines of that period were constructed in this way.

Fabricated crankcases are also easier to repair if one should suffer a mishap, more than can be said for an iron casting.

The only drawback to fabrication is that it requires more work to get it to the machining stage, with a casting, once you have a pattern, it is a fairly quick process to make more castings. Probably not much in it for a one off project.

The MOD used to favour fabricated steel crankcases for shock loading purposes in their ships, but I think that may no longer be the case as modern resilient mounts can now attenuate some of the load.

The original Paxman Ventura and Valenta engines were fabricated mostly from pre-machined steel plate, although the more complex shaped drive end gear housing was a steel casting, as were the main bearing plates. Later HST train engines were however, SG Iron castings.

Nothing wrong with a fabrication, just think, they don't cast submarines!

Neil

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