Stuart Beam model steam engine c. 1770s onwards - Rik Thistle - FINISHED - 1:12 (est)

[Rik Thistle]

Hi all,

 

This is a record of my Stuart Beam engine build. 

 

The suppled kit consists of cast iron castings, various sizes of brass and mild steel bar, fixings etc. It is available here - https://www.stuartmodels.com/product/stuart-beam-unmachined/

 

Rather than try to capture every step in the manufacture I'll concentrate on some of the more interesting/challenging aspects.

But firstly, a bit of background on 'beam engines'. They had been about for quite a while before James Watt came along with his 1776 patent to improve the efficiency of the engine which turned it in to a more practical and cost-effective way of supplying power to various industries ( https://en.wikipedia.org/wiki/Beam_engine )

 

Watt also designed the Beam engine's Watt Linkage which allowed the vertical motion of the piston rod end to connect to the beam end (which describes an arc).

One of the main applications of Beam engines was to pump water eg  help supply a town's population with water.  Quite a few Beam engines have survived to this day - a great example is the Rotative Beam Steam Engine At Crossness - https://www.youtube.com/watch?v=Zlp1aG1VJRI  These are very graceful but powerful, slow moving machines (typically 11 rpm). My model rotates slightly faster 😉

 

(And since no 'garage' collection is complete without a Beam engine, Jay Leno also has one ... https://www.youtube.com/watch?v=zoBWAE0win0ce )

 

Electric pumps eventually replaced these wonderful machines, since they required much less maintenance and less bodies to keep an eye on them (eg oiling all the metal to metal interfaces).

 

So, on to my build. As with the Stuart 10V I bought the booklet that covers the engine build - it was OK but perhaps not as useful as the 10V booklet. The cardboard box this time was much larger and heavier. The contents are shown below.

Above, there are two large sheets - Detail Drawing sheet for all the parts, plus a Build guide/Parts list/ Exploded diagram sheet. The actual parts arrive sealed on to two pieces of cardboard.

 

Below, doing a head count of the parts.

 

Below, six of the larger cast items. The very large base (Bedplate) turned out to be a tight fit on my milling machine, with just enough space left at the ends for clamping.

 

Below, the brief build instructions alongside the exploded view.

 

The Beam flywheel is 7" diameter, when finish machined - the 10V's flywheel was 3" diameter, so at times I did wonder if this time I needed a bigger workshop.

Well, that's a brief introduction to my Beam ... I'll follow up shortly with a post covering the machining of the base and maybe some other stuff if time allows.

 

Bye for now,

 

Richard

 

 

 

Edited December 8, 2023 by Rik Thistle

[Rik Thistle]

The first part to be machined was the engine's base, officially known as the 'Bedplate'.

 

Below, I cleaned up the Bedplate by filing off casting flash before presenting it to my SX2P mill.  The table of the mill measures 15 3/4" (400 mm) x 5 3/4" (145 mm) which meant it was 'just' large enough to hold the Bedplate. 

 

I think I used a 3 flute (diameter 8mm or 10mm?) carbide cutter for most of the machining on the Bedplate. Since cast iron can exhibit almost diamond hard surfaces if cooled too quickly, carbide tooling can sometimes be necessary .... High Speed Steel would blunt in a second.  I don't recall any hard spots on the Bedplate but generally you never know they are there till you hit them.

 

 

 

Below, clamping the Bedplate to the mill table. The four mounting lugs plus the underside of the Bedplate were skimmed level.

 

Below, and flipping the Bedplate over (onto it's now-flat-base, I machined the mounting pads for Linkage Bearings, Cylinder, Column and Flywheel Bearing. Whilst I had the Bedplate on the mill I also drilled and tapped the holes (not shown) in the pads.  As you can see, the clamps at both ends just fit on the length of the mill table.

 

Below, checking the height of one of the pads during the milling operation with a 2nd hand Moore & Wright 1" depth gauge and a 1-2-3 block. I bought the depth gauge of eBay in the Spring, and once it was cleaned up it was as good as new. Note: The assembly isn't sitting on a paper towel 😉 ... it's sitting on a 1/4" thick 'Surface Plate' made of float glass.

 

Below, the cast iron Cylinder Bottom Cover being machined on the mill. The Cover attaches the Cylinder to the Bedplate, and it did have some hard spots around the corners where it would have cooled quickest.

 

OK, that'll do me for today. It's been a while since I did any Posting on the Forum so I feel a bit rusty ...apologies for any glitches.

 

Regards,

 

Richard

 

 

 

 

 

 

 

Edited July 24, 2022 by Rik Thistle

[Egilman]

It's been a couple of decades since I've been in a machine shop My friend, brings back memories....

 

Modern Irons are a bit better in the quality department than the stuff they used back in the day, but yeah I can remember some stuff that broke everything that touched it... (except the diamond  dusted cutter)

 

I'm in, pulling up the comfy chair as I speak...

[Rik Thistle]

Hi all,

 

Thanks for the Likes .... and Egilman... yes, materials are continually improving although I suspect that Stuart Models, who came in to existence in the very late 1800s, may still be using using some of their original casting equipments and methods. OK, that's a slight exaggeration but Stuart do hold on to their practices for a long time, which probably isn't a bad thing.

 

Today I'll focus on aspects of the Cylinder, that part of the engine where the energy of the steam is turned in to work.

Below is the exploded diagram showing the Cylinder...Part (1) over on the right side.

As can be seen from above, the Cylinder has a Piston inside that moves up and down courtesy of the Valve (29) alternatively applying steam pressure to the Piston's (8) top and bottom surfaces.

 

The power chain is....  Piston Rod end> Beam end at the right> Beam end at the left> Connecting Rod> Crank> Crank Shaft> Output Pulley. The Flywheel (46) stores energy, and also helps smooth out the 'explosive' outputs from the steam entering the Cylinder ends.

 

Below, the cast Cylinder as it arrives in the box. Stuart Models give the cast parts a quick grind at their factory to remove the more obvious flash from the casting process. However, in this case the grinding went a bit too deep on the Valve face meaning there wasn't sufficient material left to meet the final dimensions. Stuart models happily replaced the part in a few days.

 

Below is the Detail drawing of the Cylinder. You can see on the rectangular front face there are ports marked A2 and B2 ...this is where the Valve lets the steam enter the Cylinder. The steam works it way to either end of the Cylinder (A1 and B1) where it emerges on to the piston face.

Above, there are three ports in the centre of the valve face outlined in dotted lines on the drawing.

From top to bottom -

- A2, feeds steam to Cylinder top,

- Exhaust port allows used steam to exit,

- B2, feeds steam to Cylinder bottom.

 

Below, there was a lot of black casting sand left in the Cylinder ater the part had been cast - enough to firmly block off the connections between A2/A1 and B2/B1. It took about 30 mins to wiggle it all out with some garden wire.

 

Below, the amount of sand removed. I was quite impressed by how much had crammed itself in there!

 

Below, machining the Cylinder in the mill. The Wixey digital angle gauge proved to be a useful tool throughout this project.

 

Below, machining the valve face smooth and flat. I later filed the three openings approximately to the sizes the drawing requested...I'm wondering now if I should have actually used a small diameter milling cutter to more accurately form those openings?...maybe, but from what I recall the openings weren't exactly in the positions the drawing showed.

 

Now taking the Cylinder to the lathe to do some boring work ie open out the hole that the Piston will side up and down in. I wasn't 100% sure whether to bore out this hole first on the lathe and use it as a reference before milling the cylinder faces, or the other way around ie mill or lathe work first? - I eventually decided on 'mill first'. With a bit of careful clocking on the lathe using the 4 jaw chuck I got the Cylinder positioned good enough for a concentric bore.

 

Below, finishing off the bore. It ended up about 10 thou" (0.25mm) undersize...enough spare material, should I later decide to do some honing on it.

 

Below, are the two end caps that seal off the Cylinder (Bottom cap left, top cap right). Not the easiest of things to hold in a lathe....fortunately Stuart leaves a casting shaft protruding for gripping in the lathe. These shafts should be turned to a smooth finish before being turned around and held in the lathe chuck jaws.

 

Setting up the Cap shafts for turning by using a drill chuck to hold the Cap square whilst the 4 Jaw was adjusted to grip the Cap. The already shiny perimeter of the Cap was done on a grinding wheel (to remove the hard cast outer layer) so is not that accurate, yet. It will be once the shaft is held in the 3 jaw chuck.

 

Finally, the Piston (mounted on the Piston Rod).... and it's 'Piston Ring' aka O RingWhen the O Ring was originally fitted to the Piston it sat about 40 thou (1mm) proud of the Piston, which was of no use.

 

I investigated alternative, small CSA O Rings and also tried some of the supplied Gland Packing material ...but no joy...none of them was going to give a reasonable piston seal/sliding action in the Cylinder. Note: The piston was already a sliding fit in the Cylinder so could probably have worked OK without any O ring. I eventually hit upon the idea of using Emery cloth to grind away about half of the O Ring till it was almost flush with the Piston. And after a few trial fits and a bit of lubricant this worked a treat 🙂

 

Well, that's it for today. Next up should be the Valve apparatus.

 

Regards,

 

Richard

Edited July 26, 2022 by Rik Thistle

[Egilman]

1 hour ago, Rik Thistle said:

I wasn't 100% sure whether to bore out this hole first on the lathe and use it as a reference before milling the cylinder faces, or the other way around ie mill or lathe work first?

My wise old toolmaker teacher advised me concentric cylinders first, then clean the flanges to assure your flanges are perpendicular to the bore... Less chance of mistakes that way... (and less work)

 

Not too many willing to show the steps to accurate one-off machining anymore but then again everything is done by computer nowadays... Nice work....

[Rik Thistle]

Egilman,

 

Agreed. But since these are castings with little or no regular sufaces to locate on to I went for the mill first, to give me a square face to grip on once it was in the lathe.

 

And since the batch size is only 'One Off' mating parts can be fettled to suit 😉

 

These engines are interesting and, usually, relaxing projects.

 

One of my favourite scratch builds is this one here .... https://www.modelenginemaker.com/index.php/topic,10250.0.html  It's a real tour de force requiring skill, perseverance and knowledge. Most of it was done on Sherline equipment ...the forum thread is over 140 pages long so that gives some idea of the complexity involved.

 

regards,

 

Richard

 

 

 

[Egilman]

2 hours ago, Rik Thistle said:

Egilman,

 

Agreed. But since these are castings with little or no regular sufaces to locate on to I went for the mill first, to give me a square face to grip on once it was in the lathe.

 

And since the batch size is only 'One Off' mating parts can be fettled to suit 😉

 

These engines are interesting and, usually, relaxing projects.

 

One of my favourite scratch builds is this one here .... https://www.modelenginemaker.com/index.php/topic,10250.0.html  It's a real tour de force requiring skill, perseverance and knowledge. Most of it was done on Sherline equipment ...the forum thread is over 140 pages long so that gives some idea of the complexity involved.

 

regards,

 

Richard

 

 

 

There are about a half a dozen ways of doing it some easier than others, the object being to get an accurate base surface to measure and machine from... And yeah you can "adjust" the machining to fit the casting that's the "art" part of it... Skill and experience

 

That is definitely an interesting build, a tour deForce in the art of machining.... Thanks for the link Rik... Those are about the size range of the SS Titanic engines... Massive beasts in real life...

 

What's being lost is the art of it though and that's the real shame...

Edited July 26, 2022 by Egilman

[Roger Pellett]

Wonderful!  Thanks for posting.  Lining everything up to be square and concentric while being stable enough to withstand loads from machining is expertise that few people have.  Seeing work like this people often say, “Wow, you’re good with your hands.”  They fail to understand the mental challenges involved.  This is first class workmanship.

 

Beam engines were used extensively here here in the USA for marine propulsion, particularly for passenger steamers on the Great Lakes, Eastern Rivers, and The East Coast.  These very large slow speed engines turned side paddle wheels.  Most used low pressure steam, less than 50psi, getting much of their motive power from the condenser vacuum.  His meant huge size;  cylinder diameters of 6ft were not uncommon.

 

Roger

[Rik Thistle]

Roger,

 

Thanks for that. The steamers on the Great Lakes are something that has recently appeared on my radar and is a fascinating subject. I need to read up on it. Six foot diameter is some size .... but no doubt designed to match the requirements.

 

A few months back I bought 'When Rails meet the Sea' by Michael Krieger ...not got round to reading it yet but looking forward to it. It focuses on the American port cities 1830-1960.

 

Richard

[wefalck]

Nice project, I will keep following it ...

 

Talking about building logs: I have been following this YouTube channel for a while. That lady(!) is currently building one of the bigger Stuart kits, with lots of good ideas for set-ups of awkward parts etc. - 

 

 

[Rik Thistle]

I have been following this YouTube channel for a while

 

Yes, I've been following Blondiehacks for a couple of years. She's very good at explaining things.

 

That current steam engine build of her's is quite large and needs a bigger lathe than I have. But it is fascinating to see it coming together.

 

Richard

[Roger Pellett]

Rik,

 

You probably already know this but the power produced by a reciprocating engine is proportional to PLAN where:

 

N= RPM

A= Piston Area

L= Piston Stroke

P= Mean Effective Pressure

 

L was limited by the depth of the ship’s hull and these large side paddlewheels were limited by how fast they could turn.  In early days boiler and piping design, and feedwater control problems limited operating pressure.  In the 1800’s the huge loss of life from boiler explosions resulted in the writing and establishment of the ASME Boiler design code.

 

The one variable that was not restricted was A, piston area, resulting in large diameters.

 

Roger

[Rik Thistle]

Roger,

 

Yes, I did know of the power equation but I'll admit I wouldn't have recalled it easily since it donkey's years since I used it ;-).

 

Fascinating that the diameter was the one variable that could be enlarged. I take it weight wasn't an issue and didn't affect the Centre of Gravity....I guess they placed the engine down the centre line.

 

I did see a picture of a railway engine boiler explosion the other month .... it was dramatic....the cylinder burst open and many, many lengths of narrow diameter piping all over the place, and sadly some lost of life.

 

I'm (so far) only running my steam engines on compressed air.... primarily because I don't want the risk of boiler explosion or fire near me (or anyone).

 

Richard

[Rik Thistle]

Hi all,

 

Today I'm going to focus on the three sets of main bearings in the Beam engine, seen below in the exploded view ie the Crankshaft bearings (37 - bottom left), Beam bearings (56 - top middle)  and the Watt linkage bearings (74 - middle right).

 

In the real world, the Crankshaft bearings support great weights and experience constant rotation, so need to be tough, accurately made and have low friction. The Beam and Watts linkage bearings don't experience the same weights and experience oscillating part-rotational motion, meaning their wear pattern will be different from the Crankshaft bearings.

 

The Crankshaft and beam bearings still need a lot of lubricating oil to prevent metal to metal contact and lower friction. And, I imagine, the oil also helps dissipate heat. I'm not sure if the Watts linkage bearings used oil reservoirs or relied on being made of a different material from the steel pivot shaft, say, Phosphor Bronze - more reading required and any advice welcome.

 

Firstly, the Crankshaft/Beam bearings, shown below. They arrive from Stuart models as two-part brass castings . Earlier versions from Stuart seem to have been one-part castings. There are a number of faces that need cleaning up on the mill and lathe and the Crankshaft hole needs boring.

 

Cleaning up one half of the mating Crankshaft/Beam bearing faces in the mill. Generally, I tried to machine the bearings in pairs to ensure they were dimensionally the same.  They were spaced apart in the vice to allow even vice clamping forces, and are sitting on a pair of parallels.

 

Below, the 'other side' of the bearing mating faces being milled. This time sitting on a single parallel that covered the gap in the base of the vice. It's always a puzzle as to what the optimum sequence of machining actions are eg the bearings underside had only been filed flat but my plan was to use the bored hole (later to be done on the lathe) as the datum for cleaning up the bearing feet.

 

Below, cleaning up the sides of the bearing feet, again in pairs.

 

And creating flats for the drilled and tapped holes that the oil reservoirs would screw in to.

 

The Crankshaft/Beam bearings now ready to have the two halves joined by bolts.

 

And here they are, ready to march off to the lathe. The bolts are 2BA (British Association)  - I later replaced them with similar 2BA bolts but with smaller hexagonal heads that were more in keeping with the scale of the model.

 

Below, positioning and gripping the bearings in the lathe's 4 jaw chuck was a bit tricky - there wasn't much to grip on, they needed to be axially correct for the Crankshaft/Beam bore and also had to be square to the chuck. The black thing is a threading attachment that happened to already be fitted to the tailstock and was called in to service to help achieve squareness of the part.

 

Cutting the first surface on the lathe. The Stuart models part list does say the bearings are made of brass, but these parts have more of a Phosphor Bronze'y look to them, in my mind?

 

I thought I'd photographed the boring of the bearings, but can't put my hands on the pics. I needed to buy a smaller boring bar than the one I had and that went fine. I used the (already made) Crank shaft as a gauge for the hole size.

 

Below, the bearings were, one by one, Loctite'd to the Crankshaft for gripping in the lathe to face off the far side of the bearings. To break the Loctite bond I dipped the assembly in Acetone for about 5 mins - that worked fine.

 

The four Crankshaft/Beam bearings sitting on the crankshaft ready for the next machining stage.

 

Back to the mill. I used the crankshaft bore as a datum for machining the feet of the bearing to the same distance to the centre of the bore. Fortunately the vice was able to grip the bodies of the bearing without too much issue...I think I had to pack out a couple of them with a bit of paper. The Crankshaft os supported on V blocks sitting on 1-2-3 blocks.

 

And now the Watts linkage bearings. They arrived as an extruded length of brass that needed drilling and cutting to width.

 

The Watts bearing material centred in the 4 jaw. That went fine. I then tentatively parted off the two bearings whilst still held in the lathe, again that was OK...it it had been Mild Steel rather than brass I may have considered a different method eg saw to length and clean the sawn face up on the mill.

 

Finally, a view of the bearings installed. The Crankshaft and Beam bearings proved to work fine - their shafts etc were already made, but the Watts linkage had to wait till their links were made. Also seen in this view are the machined Flywheel and partially-machined central support column, both of which I will add posts on in the near future.

 

Regards,

 

Richard

 

Edit: I forgot that the Valve Linkage bearings (83 -bottom right of exploded view) were also made alongside the Watts Linkage bearings. So there were 4 pairs of bearings made in total.

 

 

Edited July 28, 2022 by Rik Thistle

[wefalck]

By the colour of the material of the crankshat/beam bearings, I would also say that thei are bronze.

 

In full-size practice often Babbit-bearings were used: the housings of the bearings were carefully installed in place and then the shaft put into place, wedging it tight so that is does not move and does not touch the housings; in a next step the ring-space in the housing was filled with molten Babbit- white-metal. In this way, the bearing surfaces were all aligned without complicated boring and shimming operations.

 

 

[Rik Thistle]

...housing was filled with molten Babbit- white-metal....

 

I didn't know that...very interesting and a clever solution, thanks.

 

Richard

[wefalck]

In fact many railway steam-locomotives had such bearings. They need a lot of oil to keep them cool and are only suitable for relatively low speeds, as overheating could melt the metal   Again, this avoided complicated set-ups for boring and honing of multiple bearings.

 

I think they were also used on ships' propeller-shafts for the same alignment reasons. But I gather more often pock- or iron-wood bearings were used.

 

 

[thibaultron]

Your method of pouring the babbit material was also used for early car crank shaft and rod bearings, as well as on most early machine tools.

[Roger Pellett]

I understand that bearing (or shaft?) surfaces were often coated with Prussian Blue.  When assembled and the shaft rotated the mechanic could see high and low spots.  The bearing was then scraped with a bearing scraper to improve the fit.

 

Steamships with reciprocating machinery required Crewmen called Oilers.  Oilers would make the rounds and feel bearings; with the engines running!  A good Oiler could find a “hot bearing” that needed lubrication by feel.  

 

Roger

[Rik Thistle]

Roger,

 

surfaces were often coated with Prussian Blue

 

Yes, from what I've read recently there was quite a bit of fettling required to get a good rotating fit.

 

Once electric motors became available I can see why they quickly replaced steam engines in many applications ie less maintenance and manpower required and overall, cheaper to run. Follow the money, as usual.

 

I find steam engines fascinating and it is a shame they are no longer a part of our daily lives. However, nuclear power stations still heat water to produce steam so it could be argued that steam power is still very much with us.

 

Richard

 

[mtaylor]

51 minutes ago, Rik Thistle said:

I find steam engines fascinating and it is a shame they are no longer a part of our daily lives. However, nuclear power stations still heat water to produce steam so it could be argued that steam power is still very much with us.

Not just nuke plants.  Many coal fired plants are still in operation though many use turbines for converting the steam power to rotational power.

[Egilman]

7 hours ago, thibaultron said:

Your method of pouring the babbit material was also used for early car crank shaft and rod bearings, as well as on most early machine tools.

In the Movie "The Train" Burt Lancaster (1964) gives a good demonstration of re-lining a locomotive drive rod bearing through Babbit pouring.... 

Edited July 28, 2022 by Egilman

[Roger Pellett]

Many of the natural gas power plants that are replacing coal are Combined Cycle plants that use the very hot exhaust from gas turbines to generate steam in waste heat boilers to power steam turbines.  By generating electricity from both the high temperature  gas turbine and the lower temperature steam cycle these plants offer very high thermal efficiency.

 

Here in the US a number of coal fired plants have been converted to gas powered combined cycle plants.  The coal fired boiler is demolished and replaced with gas turbine/ waste heat boilers.  Much of the existing steam cycle piping and equipment is then used for the new plant.

 

Roger

[mtaylor]

3 hours ago, Roger Pellett said:

Many of the natural gas power plants that are replacing coal are Combined Cycle plants that use the very hot exhaust from gas turbines to generate steam in waste heat boilers to power steam turbines.  By generating electricity from both the high temperature  gas turbine and the lower temperature steam cycle these plants offer very high thermal efficiency.

 

Here in the US a number of coal fired plants have been converted to gas powered combined cycle plants.  The coal fired boiler is demolished and replaced with gas turbine/ waste heat boilers.  Much of the existing steam cycle piping and equipment is then used for the new plant.

 

Roger

Thanks for that, Roger.  I guess I'm behind the times at this point.

[wefalck]

Here in Europe, after Putin is turnig off our gas-supplies, we are firing up again old coal-fired power-stations that were kept on stand-by. Problem is that in many European countries coal-mining has been phased out, the only major European producer is Poland. Much of our needs now come from as far as South Africa and even Australia. Those guys running museum steam engines and the likes feel that in their pocket ...

 

Back to the topic of machining now!

 

Edited July 29, 2022 by wefalck

[Rik Thistle]

Hi all,

 

Today, a short post on the Watt linkages, and the Valve Chest linkages.

 

James Watt, regarding his linkage idea, wrote in 1784 ...

 

I have got a glimpse of a method of causing a piston rod to move up and down perpendicularly by only fixing it to a piece of iron upon the beam, without chains or perpendicular guides [...] and one of the most ingenious simple pieces of mechanics I have invented.  .... https://en.wikipedia.org/wiki/Watt's_linkage

 

There were  8 off Watt links to make, plus two off Valve chest links. The Links are used in pairs. 

 

The linkages are usually given a fishbelly profile. I suspect this is done for looks, but any advice on that welcome. The fishbelly (on models) is achieved by mounting each linkage between centres in the lathe which allows an elegant shape that tapers from the middle to each end.  I had a long thought about doing that but decided on a simpler process - use the mill to taper the links in one plane.

 

Here is the pair of valve links in the mill vice, aligned with a pair of 1/8" pins.

 

Below, to get a suitable taper angle I calculated that clamping the links at a 4.3 degrees slope was ideal. My Wixey digital angle gauge helped accurately set the angle.

 

Below, the 8 off Watt links get the fishbelly treatment, again held in line with 1/8" pins.

 

Reset the links and angle, and the other side is done.

 

All 8 off Watt links almost completed. The ends of some need a bit of trimming, but since they were all to have their ends rounded anyway a file took care of that.

 

The Valve Levers having slots cut in them.

 

And then the Lever grub screw holes tapped. I tend to use my flat bar tap wrenches for most tapping jobs. But small taps don't have a guide hole in their end - I recently acquired a Starrett T Bar tap wrench which has a guide hole in its end so ensures vertically tapped holes - I think I'll be using it a lot more in the future. The Sterrett also feels extremly well made - the only drawback is that the wrench's cross-bar is much higher than the flat-bar one so has a higher wobble factor (assuming it isn't supported by the guide hole).

 

One of the many 1/8" diameter pivot pins that the linkages use, being turned up in the lathe.

 

Now a couple of pics of the cast iron Valve Chest. It's very similar to the 10V chest. It required mostly milling work.

 

And a little 4 jaw chuck lathe work to round off the Valve rod dome - the tail of the valve rod always sits within the internal hole drilled in the dome.

 

Using the cast iron Valve Chest Cover to spot fixing holes through onto the Cylinder itself.

 

There are a number of brass glands required, for guiding steam in and out, and also for guiding the piston rod. For these Stuart supplies a length of brass extrusion that is turned to shape in the lathe, central hole drilled, parted off and then fixing holes added.

 

Finally, we see the Watt linkages hanging from their bearing points on the main beam and entablature arms- the arms were still hanging loose at this point. Also the two Valve links are in place, connected to their levers which in turn are worked by the eccentric sheave on the crankshaft.

 

Up next, in a day or two, should be the Flywheel 🙂

 

Regards,

 

Richard

 

 

 

 

 

 

[wefalck]

The machine begins to look like one  👍

 

The fishbelly-shape serves to stiffen the link against buckling, when longitudinal stress is applied, and to reduce the moving mass at the same time, compared to using the same width all along. Reducing these masses is important, as they have to be accelerated and then decelerated at each stroke. At this time engineers had only limited means to calculate the static stresses on such parts and basically no means to calculated the dynamic stresses. As you can often on say connecting rods in steam-locomotives, the interior has been thinned, leaving basically a bar on both sides with a sheet of metal spanned out between - effectivelly like a fishbelly girder-bridge. Such parts would have been moulded and cast.

 

A question: why did you turn the pivot-pins and did not use precision ground 1/8" rod and ream the holes to size?

 

And another observation: I tend to start-tap holes in the milling machine with head in the same position as for drilling the hole. This ensures verticality. I utilise the backlash on the vertical spindle, lowering the head to the bottom of dead move, advance the tap perhaps half a turn, then again taking out the backlash, and so forth. I usually do this only for a couple of threads, until the tap has securily grabbed, and finish off tapping away from the machine.

 

[Rik Thistle]

fishbelly-shape

Euler strut theory - I should have recalled that.

 

pivot-pins

Some of the pin material came as 1/8" stainless steel rod, so those I left alone, apart from adding threads on the end.  Not being ground stock the stainless, IIRC, was not 0.125" but closer to 0.123"... but good enough for this job.

Some of the other pins had stepped diameters ... the one shown in the pic with the 4 mm collet is 5/32" rod, with it's ends being turned down to 1/8"

I should have mentioned I not only drilled the holes but did also ream them to size.

 

tapping

Yes, I tried using that method also when I first got that mill (SX2P), but the head has a bad habit of suddenly dropping if the clamping is a bit off. I also use the smaller taps in a pin vice held slightly loosely in the drill chuck. The pin vice knurling gives enough purchase to hand turn the (small) tap.

 

Thanks for the inputs.

 

Richard

 

 

[Egilman]

2 hours ago, Rik Thistle said:

The pin vice knurling gives enough purchase to hand turn the (small) tap.

 

That's my technique as well for the really really tiny taps, I got tired of replacing them.... {chuckle} Hand tapping very fine stuff is an art in itself...

[Rik Thistle]

Hi all,

 

Today a short post about the Stuart Beam engine Flywheel manufacture. 

 

The flywheel stores energy from the engine and that helps smooth out the pulses from the cylinder, and also encourages the crankshaft to continue in the same rotational direction when TDC and BDC are reached.

 

The Stuart models cast iron flywheel arrives with a reasonable amount of casting artefacts and needs cleaning up before being mounted on the lathe. The lathe, a Sieg SC2, can accommodate a maximum diameter of 180mm ...the raw casting was larger than that. It's finished machined diameter is 177.8 mm (7"). After being cleaned up on the linishing belt there was about 0.5mm clearance from the bed of the lathe, which was fine.

 

For a finished flywheel to appear to run smoothly to the eye one should carefully file the inner face of the rim since that cannot be machined. I also spent a good bit of time on the linishing belt trying to clear off the hard outer perimeter of the casting...I got most of it off but there were still some patches that gave my Carbide tipped tool a few moments.

 

Below, the flywheel is mounted in approximate position on the faceplate, and away from the lathe to avoid a fight with gravity.

 

Final alignment of the flywheel on the lathe was greatly aided by my trusty die holder which fortunately had the same end diameter as the boss on the flywheel. The four clamps were equi-spaced and didn't create much, if any, of an imbalance at the turning speed.

 

Below, skimming the outer perimeter of the flywheel. Try as I may, I could never get the tool tip to cover the full width of the flywheel from one side - I resigned myself to having to finish that job by turning the flywheel over.

 

Below, after part turning the outer surface and cleaning up the wheel face, I bored out the hole (7/16") for the crank shaft. I did need to buy a smaller boring bar than the ones I already had. The white dot was a rough indicator for when the tool was through the flywheel. Once done the crankshaft was a good sliding fit. You can also see the step on the outer surface of the rim which was as far as I could sensibly go - to finish it off the flywheel was turned over and re-clamped.

 

Below, the finished wheel. It cleaned up nicely once I got the Emery cloth on it 🙂

 

The flywheel, and a few of the other rotating items are clamped to their axles by slotted-head grub screws. I don't feel this is entirely suitable for a number of reasons. The slotted head gets disfigured quickly (a socket key head is better), the axle gets marked (a flat needs to be added to the axle) and the grub screw can slip against the axle (again a flat will help prevent this). There are changes I plan to do.

 

Catch you all soon,

 

Richard