Author Topic: Murdoch-Aitken "Steeple" engine  (Read 1201 times)

Offline Jo

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Re: Murdoch-Aitken "Steeple" engine
« Reply #15 on: October 09, 2021, 12:06:15 PM »
I am not worried about the small stuff. It looks like they can all be done by through holes and bolts if you want (I will be studding)  :)

Jo
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Offline Jo

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Re: Murdoch-Aitken "Steeple" engine
« Reply #16 on: October 09, 2021, 04:12:45 PM »
I have just found a picture of the original model from 1932 (attached). Clarkson's purchased the rights to market the model  ;)

Jo
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Offline scc

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Re: Murdoch-Aitken "Steeple" engine
« Reply #17 on: October 11, 2021, 07:39:43 PM »
Thank you Jo for the spelling correction(s)               Well I have made a start by squaring up the bedplate casting to provide a datum.  As you can see in the second photo the endmiil decided to drop out of the collet :facepalm:  Never happened on barstock of course,  only on a one off casting.....JB required.    I drilled and tapped the four main holes and screwed on two bits of scrap to enable a good hold on the mill.  I don't think the whole top surface needed machining, just the column and bearing mounting  cutterpoints.  However I followed the drawing and brought it all down to thickness.  Jo, I agree with the through holes but I think I too will use studs. I'm undecided on the wedges as I will have to buy a dovetail cutter >:(
Jason,   the only hard stuff on this first casting was the edges of the flash which would not file off. needed a touch with the Dremel. 
Casting age is unknown but puchased last year.  The pair of upright crosshead guides are brand new,recently supplied by Blackgates following a broken pattern.       My drawing set is 1971/2                 Terry

Offline Jo

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Re: Murdoch-Aitken "Steeple" engine
« Reply #18 on: October 11, 2021, 09:38:25 PM »
Good start  :)

I cannot remember if I ever used a dovetail cutter on these  :thinking: It’s easy enough to make a cutter for the cotters/wedge slots ;)

Jo
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Offline Jasonb

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Re: Murdoch-Aitken "Steeple" engine
« Reply #19 on: October 12, 2021, 07:06:26 AM »
Yes a small flycutter type single point tool would do those undercuts for the wedges. Or as they are unlikely to really do anything you could make dummy wedges with a section of dovetail at the end and just parallel so it can be dropped into place.

Full size would only have machined the pads but sometimes if a model casting is a bit variable your method to do it all will tidy things up.

Offline scc

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Re: Murdoch-Aitken "Steeple" engine
« Reply #20 on: October 12, 2021, 08:22:01 PM »
Interesting to see the original casting set Jo. There are a couple of small differences to mine. It looks as though the main bearing caps used a different pattern, My set has a much smaller length of gunmetal for the bearings, and you have a set of bevel gears for the governer.  I was amazed to see how tall my main bearing castings are..it would do caps as well!
I admit gunmetel is a "new" material for me :-[.........anything I should know?             Terry

Offline Jasonb

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Re: Murdoch-Aitken "Steeple" engine
« Reply #21 on: October 12, 2021, 08:39:40 PM »
It's interesting that neither set of castings seem to be the correct shape to suit the drawings which show a profile like I have shown in green which is what is also shown on those images of the full size one and the 1932 model. Did Clarkson purchase the drawings and then make up their own simplified castings?

Gunmetal can be soft so take care when holding in teh chuck etc that you don't make finished surfaces but does depend on the actual alloy.

Offline Jo

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Re: Murdoch-Aitken "Steeple" engine
« Reply #22 on: October 12, 2021, 09:33:17 PM »
I was planning on making Jason’s day and making replacement main bearings  out of bar stock :-X The trick to getting the correct profile is to take a bigger piece of steel. Drill two holes the diameter of the half round profile at the correct centre distance, mill these to half width then silver solder in two pieces of rod.

As Jason has said some of the castings look like they were not originally castings and clarkson made patterns for them.

Mine also came without the gears but then I got lucky and I acquired that set with another partial set of clarkson castings that had gears with it and knew that they were not for that engine and got lucky  ;D

Jo
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Offline Craig DeShong

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Re: Murdoch-Aitken "Steeple" engine
« Reply #23 on: October 12, 2021, 09:47:36 PM »
The terminology “steeple” has me a bit confused.  My only reference is to a “steeple quad” engine that was installed in a steam driven tugboat.  Obviously this engine is quite different.


Trying to remember the specifics of the “steeple quad” I refer too; I believe it was a triple expansion engine with the cylinders stacked on top of each other, with the two low pressure cylinders occupying the base.

I was planning on researching this engine for a possible build, but I forgot all about it.  I’ll need to keep this idea in my back pocket.

Though the engine of this thread is obviously not the one I was thinking of, it certainly does look interesting.  I’ll need to follow along with this build.
« Last Edit: October 12, 2021, 09:57:51 PM by Craig DeShong »
Craig
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but rather it's the interesting folks you meet along the way.

Offline Jasonb

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Re: Murdoch-Aitken "Steeple" engine
« Reply #24 on: October 13, 2021, 07:18:57 AM »
Yes there is always scope to add your own touches as the castings if you wish which may have been "adjusted" to suit production methods or the original details were not present. Soldering up as Jo mentions is probably the easiest though you can cut the profile from a block of cast iron if you want to stick as close as possible to a casting set. Might even be possible to cut off the foot and use the castings you have got then join on a separate foot once the profile is cut with a couple of CSK screws from below with a tough of JBWeld.



Also possible to save metal by drilling half a hole down the side of the block rather than a hole and milling some away, trick is to clamp both bearings together so you end up with half a hole in each and drill goes straight down.



Cutting from solid, I used the DRO but two passes with a roundover cutter may also work.





Talking of feet on the bearings the note under the description says 5/32" packing and drawing shows 3/16. Should be whatever the thickness of your now machined casting is (3/16") if main foundation is to be the same height as outrigger foundation
« Last Edit: October 13, 2021, 07:23:25 AM by Jasonb »

Offline Jo

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Re: Murdoch-Aitken "Steeple" engine
« Reply #25 on: October 13, 2021, 07:42:22 AM »
The terminology “steeple” has me a bit confused.  My only reference is to a “steeple quad” engine that was installed in a steam driven tugboat.  Obviously this engine is quite different.

You are right Craig, this is a Table engine not a Steeple - which has the cylinder on the floor and all the mechanism above it. For some reason Clarksons called it their "Steeple" engine and the name stuck.

If you look at the original 1932 photo you will see it called a Table Engine  :).

Jo

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Offline Jo

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Re: Murdoch-Aitken "Steeple" engine
« Reply #26 on: October 13, 2021, 08:46:00 AM »
I might have found a missing bit  :noidea:. I cannot seem to find this bearing stand anywhere on the drawings.

Jo
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Offline Jasonb

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Re: Murdoch-Aitken "Steeple" engine
« Reply #27 on: October 13, 2021, 01:04:03 PM »
It's those dodgy metric drawings of yours :LittleDevil:

Also the source of the 14BA fixings ;)

Offline Jo

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Re: Murdoch-Aitken "Steeple" engine
« Reply #28 on: October 13, 2021, 01:36:12 PM »
I have got to the source of the problem: I have two different sets of Clarkson Drawings  :ShakeHead:. The original Blue prints show the bracket. The normally printed ones do not and they have duplicated some of the valve gear parts (slightly differently).

I also noted that the main bearing was taller on one set of drawings. I need to go through these with a fine  :wine1: and see if I can find any more variations.

Jo
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Offline scc

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Re: Murdoch-Aitken "Steeple" engine
« Reply #29 on: October 13, 2021, 09:55:40 PM »
Thanks folks for your inputs.   It looks as though some calculations will be needed to ensure it all fits together before cutting metal.    I wonder if Craig's "steeple" engine was one of these? a Willans   triple expansion stacked up and looking church steeple like. All three pistons fixed to a hollow piston rod and the piston valves within :o can rev   to 500rpm.  I don't think it would make a good model as all the moving bits are enclosed.               Photo from George Watkins book    "the stationary steam engine"               Terry