High Pressure Steam Table Engine

[Jo]

Why am I building this model engine? Terry last year enquired about a reasonably priced model he could build and I suggested the "Clarkson Steeple" Engine. When he brought his set of casting he sent me a PM suggesting that thought it would be a good idea if I made mine in tandem with his so that I could provide clues as to how not to do the bits on his engine. Terry has made an excellent start to his engine over here: https://www.modelenginemaker.com/index.php/topic,10540.0.html

So lets start with a bit of history of this model design:  in 1932 Mr R Wood exhibited his model of the "High Pressure Steam Table Engine" built in 1840 by Murdock Aitken & Co, Glasgow at the Model Engineer Show for which he was Awarded the "Borneo" Cup  . He made his model to a scale of 13/16" to a foot. I am not sure why he chose this scale  but he may have limited it to what he could turn on his lathe so he chose to scale the model accordingly.

One of the well known suppliers of sets of Locomotive Castings "Clarksons" was so impressed with his model that they purchased the rights and after a number of years set about marketing the casting set and this is where the confusion sets in: Clarkson in their catalogues called this a "Steeple Engine". Steeple engines normally have their heavy cylinders on the floor and their crankshafts above them which this doesn't

The castings for this engine is currently available from Blackgates in the UK for a very reasonable £220 but you will also need a few few pairs of bevel gears as well. As Blackgates are now the supplier of Clarkson model engine castings they have continued the Clarkson name of "Steeple Engine" but seem to think it is now to a scale of 1" to 1' 

I may regret this but I plan to make a 1:1 scale of Mr Wood's model engine  from the Clarkson castings, so I am calling it what Mr Wood called it a High Pressure Steam Table engine 

Jo

[Jo]

Clarkson have provided two different sets of drawings for this engine over the years. The later set is known to have bits missing and duplicates of bits  Blackgates do sell a set of drawings but I am not sure which set they supply. For myself I have parted out the later drawings then realised that a part was missing and then had to add it to my binder 

I found in a book a set of original engravings from which I think Mr Woods built his engine:

These show that the Clarkson drawings have a few more simplifications which may (or may not  ) be included in my build.

Here is the starting point:

Now what is really, really simple that even I can't get wrong  And  I think I am short of a casting.

Jo

[Kim]

So, are you missing the casting of the base?  I couldn't identify that one in your pictures.

This looks like it will be fun! I'm enjoying watching Terry's build too! Lookin forward to it Jo  

Kim

[Jasonb]

You are most likely right about the original builder basing his scale on what he could swing as the flywheel will only just fit within a Myford size gap.

Looks like the eccentric strap may have gone mossing or someone has cut the two bolting lugs off and left you a GM ring?

[Roger B]

There are a lot of new and interesting casting sets for engines appearing in the last few days  not my thing (I'm the strange kid playing on his own in the corner with fuel injection etc.) however I enjoy following the builds. Keep them coming     

[scc]

That little tin with the bevel gears in it is causing a bit of envy here     Looking forward to your build Jo.          Terry

[paul gough]

You are most likely right about the original builder basing his scale on what he could swing as the flywheel will only just fit within a Myford size gap.

Was 13/16" scale actually 20mm. Are any of the other original modellers sizes consistent with this 'metric', or is itjust a coincidence. Regards, Paul Gough.

[Jo]

Yes I also thought the eccentric strap was missing but that odd bronze ring has the correct casting number on it    I found something more suitable:



Off we go then  First up the base casting. I need to be able to hold it so I flattened the underside and made the "sticky out bit in the middle" so that it had square sides:



Now I can hold the casting so time to turn it over and find the centre. It seemed obvious to use the hole in the centre:



Then I checked with the sides and found the hole was off set 



Then I started playing try to calculate the missing hole dimensions  The distance out for the crankshaft bearing (29.4mm) is missing as is the distance for the mounting for the water pump (centre 43.15 mm). Before drilling all the holes for the tapping sizes:



The top of the casting was 4.8mm above the main flat area so first job was to take the tops off and then to cut the slots for the four columns:



Lastly milling the surface for the crankshaft bearing housing:



The main flat surface of the casting is still well over the 3.18mm but I am going to leave that for now and write on the casting that it still needs to be taken down. I will tackle this later once I have a suitable mounting arrangement 

Jo

[Twizseven]

Jo,

Really pleased to see you doing another build, complete with your ideas, improvements and suggestions to builders.  Will watch with interest.  I have been struggling to start anything over the last 12 months.

Keep looking at part done Redwing.  I want to get on with it.

Colin

[Jo]

Thank you Colin,

Yes a lot of people have found the challenges over the last couple of years with Covid has made them struggle with being able to focus on making models and sadly I am one of them 

The drawings for this one are a bit "lacking" in places 

Jo

[Admiral_dk]

Great to see you back in the Shop and up to your usual standard Jo - including the thought process 

Will follow you progress and hope to learn 

Per

[Jo]

Thanks Per 

From the base to the table is those four columns  The provided castings have less flutes on them than the original etchings that Mr Wood copied.

The first bit of fun was trying to work out all of the various bumps and lumps on the column and making it legible.  I the end I drew it out double size on paper:

I marked up the square section bits and then went back to look at the original etching again 

The central fluted area seems to have about 18 flutes and the flutes do not have dimples on the end  This means that is going to need to be a separate bit so the cutter can go passed the end of the taper.

On the drawing above you can see a red outline this is my intended shape for the central section. Initially I considered using steel but was concerned that might blunt what is going to be a rather small milling cutter. Aluminium is out due to corrosion when in contact with steel. My larger diameter brass stock would quickly become depleted if I raided it for 400mm of the stuff. Then I found a 7ft length of bronze hex  That must have been kicking around since a few years BD the amount of patina on it. Having cut 4 pieces of 100mm off of it, lets see how it turns:

A bit sticky but not too bad, just a long tedious job to do    Hence I am in for a coffee trying to get my enthusiasm up and eyeing up my cross stitch thinking how nice it would be to finish that off today  I could look out a means of cutting the taper 

Jo

[Jo]

I do not want to start anything taxing at this time of the day  So I have opted to look at preparing to cut that taper. So many books talk about offsetting your tailstock  This is how I propose to achieve the same:

I will be using a boring head mounted in a ER32 toolholder in the tailstock, to provide an offset centre, thus:

You may have noticed a second centre in the first photo. I am not sure if a pointy centre will be able to provide sufficient pull over without a bit of rubbing so I have also made a ball centre just in case.

The second challenge will be cutting the flues parallel to the taper which is important otherwise they will get shallower towards the thin end With a dividing head comes a tailstock. If you look at the larger one of these two you can see it can be offset to enable tapers, the little one I will be using doesn't 

All is not lost as I will be adding some packing under it to provide the required offset

I think I am ready to go in the morning 

Jo

[Mike Bondarczuk]

Hello Jo,

So glad to be able to follow another of your excellent build logs and fully agree with your sentiment about getting back into the saddle to machine again and I have yet to start due to gardening taking precedence.

Mike

[Jo]

Thank you Mike, please to see you are following along. Yes I agree the garden is very time consuming at this time of the year.

To begin the day all four columns were turned to fractionally over same diameter as the widest part of the taper:

The length of the centre section is within 0.05mm of each other so that should do 

The taper cutting set up is simple: Mount between centres, move the tool up to touch the outside diameter on the wide end, move to the other end and wind the tool out by 1.5mm, then move the boring head toward the tool by 1.5mm and check it touches. This should nearly set up the taper but a small adjustment will be needed as by moving over the tailstock end of the piece also moves the headstock end over so always check dimensions as the turning proceeds:

Initially I tried using the pointed centre on the boring head but it was not giving a good finish 

So I swapped it for the ball support:

Other than loosing one of my balls in the swarf  all went well. At the end of the day four tapered columns:

At this point I found I did not have in stock the intended size ball end cutter I hoped to use for the flutes  Time to finish off that cross stitch 

Jo