James Coombes but not as you know him

[JasonBModerator @jasonb]

Having enjoyed the "reinvented" Stuart Real project last year and seeing Jo's current bulid I thought that their James Coombes could do with a similar treatment to bring him into the 21st century. So I set to with a copy of Andrew Smith's book which is the cheapest way to get a set of the drawings and redrew it in Alibre to use mostly barstock and to metric standards. Some of the main points I wanted to address were:

-Do away with the cast box bed and outrigger bearing support and mount the engine on a "stone" plinth

– The sole plate and table on the stuart are just bits of flat 3/16" plate so these to be made to look a lot more like castings and generally more appealing to the eye.

– Similar with the plain columns to be replaced by ones with classic bases and capitals

– Do away with the soldered conrod which may put people off and not easy to solder it up true

-Do away with the clumsy bolt together eccentric rod and replace with a single straight piece

– Add decorative bands to the cylinder as I was not going to timber clad this one and do something with the inlet as I don't like that going in via the valve chest cover. And while I'm at it get rid of the chunky exhaust flange.

= Generally add a bit more detail but not go as far as things like fluted columns, wedged and cottered straps etc otherwise I may as well just build a Waller Table Engine.

[JasonBModerator @jasonb]

[JasonBModerator @jasonb]

Starting with the sole plate and outrigger bearing base two pieces of 12mm plate were squared up on the manual mill to overall size. Then the soleplate was clamped to the CNC's bed with some packing below so that the four hole sthat will hold it to the base could be drilled and I also thinned down an area where the crankshaft clearance slot will be cut so that you don't see a thick edge around this hole as it would not have been cast full thickness.

I find mounting the clamp bars the wrong way round is a good way to lower their profile so you can get in closer without too much tool sticking out of the collet holder.

Using the four previously drilled holes the sole plate was screwed to my well used machining plate to have 1.5mm taken off most of it's thickness just leaving raised bosses under the screws and a raised rectangular pad for the bearing pedestal using a cutter with 1mm corner radius to leave a fillet for that cast look. I also cut out the clearance for the crank, drilled holes for screws to fix the columns and counterbored these to accurately locate spigots on the column ends.

Just to show you don't need a CNC to do these things the outrigger base was done on the manual mill, the counterbored holes with have thivk "washers" bonded in to create raised bosses for teh hold down bolts

The quickest way to get the decorative moulding around the edges was to hold the plate at a slight angle to replicate the draft angle and then a couple of deep passes of the side of a ball nose cutter produced the required profile unfortunately the photo was out of focus for that

Next four squares of steel were JB Welded into place and once set were milled down to an even 5mm high. These will form the bases of the columns.

The table was done in much the same way from 10mm material so I'll just post a couple of photos of the underside and then the top.

[JasonBModerator @jasonb]

The columns seemed the next logical item to make. Starting with four pieces of 12mm steel bar The ends were centre drilled, quite deeply at the bottom so that a ctr would still engage once it was drilled and tapped M5 for the CSK screws that will attach them to the bed and I also turned a short 8mm spigot to locate the columns in the bed. The tops were turned down to 4mm and threaded.

After that the embryo columns were mounted between ctrs with the tailstock one being held in my boring head so it could be set over for taper turning. The next couple of photos are a bit blurred but it's a similar method to what I used on the Real

**LINK**

Some round "washers" were parted off and then held on a simple arbor to round over each corner to give them a half round edge. Some plain edges square ones were also made to go at the tops of the columns.

After gluing the "washers" on with Araldite and allowing to cure they were held in the 3-jaw using the jaws as a stop and all faced down with the cross slide locked which ensures they will all be the same height.

On the Victoria and Real I more or less copied the Stuart design for the bearing pedestals but a third pair was going to be a bit boring so I decided to make these with square brasses and curved caps. Starting with the main pedestals two pieces of 10mm aluminium ware machined to overall size and then a pocket for the bearing milled centrally.

Followed by machining the sides to leave the feet, these were done in 17.9mm high x 2mm stepover passes using a 2-flute cutter designed for non-ferrous cutting. The last cut having the cutter lowered to the full 18mm depth to avoid any stepover marks on the foot.

The last couple of jobs were to drill and tap for the caps using an M3 spiral flute tap which lifts the swarf out of the blind hole and then two 4mm holes in the feet.

Two more bits of 10mm material were sized up for the caps, drilled and counterbored for some bosses to be bonded in, the central hole is for the oiler also counterbored for a threaded boss.

The underside was milled out 2mm deep (1mm overlap and 1mm gap) so that the cap would slip over the pedestal

A couple of holes were quickly drilled and tapped into a well used holding block and the CNC made quick work of roughing and then profiling the cap seamlessly blending the three arcs into one. but it can also be done on a rotary table without too much effort.

The bearings where soldered together, milled to size then drilled and reamed 12mm in the mill

Last job on these was to mill a 1mm deep groove all round just over 10mm wide to allow for the paint on the pedestals

Here is a shot of the assembled pedestal and the bosses have been bonded into the cap, I just need to add some fillets around them with body filler (bondo) and knock the corners off so they look like castings.

[Ramon WilsonParticipant @ramonwilson3]

Hello Jason

Nice to see another 'Jason build' but it does look vaguely familiar

Remember it from HMEM?

Good luck with yours – it looks like a real nice improvement on the original JC

Regards – Ramon

[JasonBModerator @jasonb]

I suppose it could be an upmarket James Coombes or a down market Waller . I did look back at your thread part way through drawing it up and was amazed how similar the bed "casting" is, flywheel won't be far off either.

As I said in the opening post

" Generally add a bit more detail but not go as far as things like fluted columns, wedged and cottered straps etc otherwise I may as well just build a Waller Table Engine."

[Ramon WilsonParticipant @ramonwilson3]

Ha, I missed that comment Jason – couldn't help but comment too though, they look so similar. The Waller was a third bigger of course and that flywheel rim was the first 'homer' the new Haas machining centre carved out from a flame cut ring. Coo! that was just over 25years ago

I'll look forwards to dipping in and out to see how it's progressing

[JasonBModerator @jasonb]

I was asked on another forum where I'm also posting this "It would be interesting to know how long it takes for the CNC to mill these pieces out of solid so we could compare it with machining castings"

F360 gives 44mins for the table and 107 for the sole plate.

In reality I would say add 10% or so to that to allow for some loss of rapids due to using the free version and tool changing. Still considerably faster that doing it by hand as you would require several setups on a rotary table to do the round bosses as solid or like the outrigger bond in pieces and then fillet with JB Weld.

I have got to the stage where I'm happy to leave the machine to get on with it so I can be doing other things while it is cutting which you can't do when using a manual machine so maybe only 20mins spent at the machine for each. Computer tells me how long each machining operation is going to take so I know when to go back and be ready to change a tool if I'm not actually working in that workshop while it is running.

There is also the initial machining to size and the moulded detail around the edges to add in which were done on the manual machine.

These were reasonably quick for their size, had they been more 3 dimensional with lots of vertically curving surfaces and draft angles then that would put the time up as the stepover between each pass needs to be smaller so runtimes increase. For example the soleplate for the next project which will be a long out of production Stuart engine is going to be just over 4hrs for a smaller engine, can you tell what it is yet?

If these were castings and we will assume they are soft and without major imperfections then it's just a case of fettling, finding a datum, milling top and bottom flat and drilling some holes which with a DRO is fairly straight forward.

However as castings are not available for these items do you want to compare total time including making the patterns and then machining them assuming you get the casting done elsewhere? We can discount design time as that would be the same for either

[JasonBModerator @jasonb]

I did most of the crank on the CNC – drilling, reaming and shaping. In this photo I have just completed the milling of a web between the two bosses which was done with a 4MM dia cutter with 1mm corner radius to leave a fillet for that cast look.

After machining it was loctited onto a 10mm spigot that had been turned on the end of the 12mm PGMS crankshaft and once set was faced off ensuring the face was at right angles to the axis of rotation.

Stuarts show a soldered construction for the tuning fork shaped conrod but I decided on a bolt together one similar to that used on the Waller table engine. I roughed out the stock on the manual mill and then thinned the ends and reamed the holes on that machine too.

Then over to the CNC where a scrap of aluminium was drilled and tapped so the job could be screwed to that for machining, I added a couple of spacers under the ends so that the work was meld down firmly.

This is it straight off the CNC, a little draw filing with emery wrapped around the file should clean it up nicely. Machining time was 24mins with most of that being the fine stepover used to do the sloping top surfaces and fillets where they meet the round bosses.

The short leg of the conrod that has the big end was turned from some 16mm dia stock, first doing the 4mm dia section before pulling out some more material for the half fish bellied rod.

This was then transferred to the spin indexer on the mill and the rectangular end formed

And while still held in the indexer the main hole was reamed for the bearing and two holes drilled for the dummy strap retaining bolts

Progress so far including the big end bearing and a couple of square headed bolts, again from round stock and the milling done with the spin indexer.

[JasonBModerator @jasonb]

The two long rods that pass up either side of the cylinder terminating at the little ends again started life as round stock rather than rectangular that Stuarts provide, like the shorter rod the ends were first reduced to 4mm and threaded then a small length reduced in diameter from the 12mm stock which will be the flange that bears against the cross piece.

Then with more stock drawn out of the collet and using tailstock support the rod was roughed down to 8mm diameter, this being the thickest part of what will be the fishbelly

It was then back over to the mill and indexer to form the rectangular end, drill dummy holes and ream for the bearings

Then once more back to the lathe to have the end 1/3rds turned to a taper with an insert that had a 0.8mm radius to leave a small fillet, hand blending of the three facets followed

After sawing off from the parent bar the little end was mounted on an arbor to be rounded over using the rotary table. I seldom use filing buttons for this type of job these days.

A couple of bearings were turned and reamed from Colphos, here I am checking the size which was a nice push fit, bearings will be loctited into place.

Four square head bolts for the dummy straps finish that part of the engine.

[JasonBModerator @jasonb]

The eccentric strap started life as two pieces cut from some 2 x 1/4" flat brass bar that were machined to their overall depth relative to the split line and then soft soldered together. Next they were machined to width over the joining lugs and a skim taken off each side to bring the blank to the desired 6mm thickness and finally a ctr drill was used to mark the ctr of the hole to be.

The ctr hole was clocked true in the 4-jaw using some parallels behind the work to make sure it was sitting flat and then then drilled then bored out to 26mm dia. A carbide grooving tool was then used to cut the groove that keeps the strap located on the eccentric

A top hat bush was quickly knocked up to clamp the strap to a tooling block so the outer profile could be cut on the CNC, You can see that I have also cut the recess for the eccentric rod and am using one of the rivit holes to stop the strap from rotating. I decided to use a couple of rivits to hold the strap on this time as the last two have been done with a csk screw.

After removal from the tooling plate it was back to the manual mill to drill for the bolts and add an oil hole, I also milled away part of the internal fillets on the upper bolting faces to leave flats for what will be square headed bolts to bear against so they won't rotate.

Some 30mm stock was then turned down to 28mm and then further reduced to 26mm leaving a location ridge in the middle, final sizing was done by test fitting the two halves of the strap until the lugs could be pinched together and the strap rotated with out binding or unwanted play.

I then offset the 30mm stub to the required throw and bored to a close fit on the crankshaft before reducing the two sides down, one for just 1mm to give some clearance and the other 6mm to allow for a grub screw to retain the eccentric. Holding in a 5C collet block by the longer side the CNC was used to cut the decorative weight reduction hole that you often see on full size engines. Roughed out in two 3mm deep adaptive cuts and then two full depth finishing passes with the 3mm cutter

That's a couple more bits ticked off the list

And complete with the 5mm x 1.5mm eccentric rod rivited into place

[JasonBModerator @jasonb]

One small job that was next to be crossed off the list was making the Acorn nuts for the top of the columns. I started with some free cutting round bar and milled to a hexagon using the 5C indexer. Then over to the lathe the shaped top was cut with the ball turner before parting off and then holding the other way up to drill and tap the nut.

I then tackled some of the valve gear starting with the levers that take the angled motion of the eccentric rod via a shaft to vertical movement that the valve requires. I actually made these links a while ago as they served to show a couple of different options for CNC machining that was being discussed in another thread at the time.

Starting with some 1/4" flat bar the holes for the three levers were spot drilled, then drilled with stub drills 0.2mm undersize and finally reamed.

The levers were then milled down to the required thickness, one at 5mm the other two at 6mm thick

I then used the witness marks from milling to line up the band saw to cut the individual parts from the bar

Over to the CNC and two holes were drilled and then manually tapped in a tooling block, this lines up the holes and sets one as datum which is easier than drilling manually and then having to locate the hole when the block is transferred to the mill.

I then ran two of the levers using an adaptive path to remove most of the material and then two contours of 0.2mm and then 0.1mm depth to finish the part this took 72seconds and as full depth cuts were used throughout the wear was spread along a reasonable length of flute. The last one I did as though the part were being cut from a larger sheet slowly ramping down to depth and then a contour to finish, this took 230seconds and almost all cutting was just with the end of the tool so wearing that short length more.

Stuarts show the levers with just straight edges but I went with a dog bone shape to add a bit more character as also stop them looking so bulky

The final op was to mill slots for the vertical rods in the thicker two levers, and a thinner slot (still to be done) in the 5mm thick one for the eccentric rod

Like the levers I gave the two blocks that support the cross shaft a bit more shape and as they looked a bit chunky also reduced the thickness between the round boss and the base. These were done from a bit of rectangular bar making use of the CNC again to get good transitions between the various radii. After this photo they were sawn off the bar, the base milled flat and then drilled and tapped M2.5 for fixing studs.

[JasonBModerator @jasonb]

Working up the engine the next parts of the valve train were the two vertical lifting links, I cut and milled some 6mm wide strips from 3mm sheet and after drilling & reaming the ends set to machining them between ctrs but did not get that far on the first one ” src=”https://www.modelenginemaker.com/Smileys/default/sad.gif” title=”Sad” />

Changing tactics I cut two pieces of EN1A round bar and did the turning first driving with one end in the chuck and the other end supported by the tailstock. A 0.8mm radius tip was used to leave a small fillet at the ends of the taper which was turned with the cross slide set over and then all blended into a fishbelly shape.

Then over to the mill to machine flats at the ends before drilling and reaming 3mm, the waste material at the ends was sawn off and then the rods rounded over in the same way as the conrod was done earler

Rather than be stuck with Stuarts half turn of the valve rod to make adjustments I decided to put a hole right through the yoke and retain the rod with a nut top & bottom that way I can get infinite adjustment of the valve nut's position simply by rotating the rod. Here I have part turned one side then with it held in teh indexer a square has been milled and cross drilled.

This shot shows a final bit of decorative turning being done, the ends have been reduced to 3mm and threaded and I have slipped a short length of rod over the threaded spigot so that I can use the tailstock for support without the need for a Ctr hole.

And this is the bits roughly assembled

A small offcut of bronze was milled down to the overall sizes of the valve and the upper porting reduced in size all round and I also chamfered the top corner sto allow a bit easier air flow

Whilst still in this position the slot for the rod was cut and then the one for the nut opening up the initial 2.5mm wide cut until the nut material was a free but snug fit in the slot

Finally a 2mm cutter used to form the cavity in it's underside

Not much to say about the nut except it was milled down to 6mm x 3mm section, milled to length and then drilled & tapped M2.5, guiding the tap to ensure the tapped hole was true and vertical.

[JasonBModerator @jasonb]

Working up the engine while waiting for the Cylinder casting the next part to make is the cylinder end cover which also serves as a mount for the two cross head guides. I wanted to do this from Cast iron and the most economical way was to start with a slice of iron bar

Held in the soft jaws it was cleaned up on the OD, faced and then a 25mm spigot turned to locate in the end of the cylinder, the piston rod hole was then drilled with a 4.8mm stub drill before reaming 5mm

Held the other way round again in the soft jaws it was faced to length before thinning down most of it to 4mm to leave a central boss which was counterbored 8mm dia for the gland and also a shallow recess turned around it for a bit of added interest and somewhere to stop the paint.

After roughly squaring up so it could easily be held in the vice jaws the ctr was located and various holes drilled – four for the guides, eight for the cylinder studs and 3 for the gland studs.

Finally using a couple of drill bit sin suitable holes the final 50mm square was machined and then a corner radius cutter used to add a small decorative moulding around the edge.

A start was then made on the cross head guides two pieces of overthickness (8mm) bar were milled to 12mm width, 6mm holes drilled each end so they could be held on a mandrel and rounded over using the rotary table. Here I and just roughing out the slots with a 6mm cutter to reduce some of the bulk so they don't take so long to bring up to soldering temperature.

The webs were done from 3mm sheet, rough sawn they were then clamped to the CNC and the oblong slots machined. I then used a couple of top hat bushes to hold the parts to a jig plate through this slot while the outer profile was cut. I also ran a chamfer mill around what will be the outer edges to make subsequent rounding over easier. I also designed the bottom of the guides with two feet rather than a solid base as the Stuart design looks a bit bulky in this area.

A couple of lengths of 8mm square were slotted to locate onto the webs and two round bosses cut for the tie bar at the top and that is all the parts ready to solder.

Here is one that has been soldered, I used a couple of short lengths of the slotted 8mm sq to hold the other end of the web at the correct central height

After a dip in the pickle I set the assembly up in the mill vice and took equal amounts off each side to bring the rough 8mm thickness down to the required 6mm. Then plunged the ends of the slot to 8mm dia with a 3-flute milling cutter

A 6mm cutter was then used to open up the slot to 8mm width and also machine the feet to the correct height relative to the slot. Top boss hole was also drilled relative to the slot.

Once out of the middle of the foot strip was sawn away and the two feet milled to length ready for a quick trial fit

[JasonBModerator @jasonb]

I had been debating for a while whether to use the usual 7" Stuart flywheel casting or to go with something a bit different. Having already machined five of these the prospect of another one did not really offer a challenge and with the casting costing just under £50GBP once tax and delivery had been added decided me to see what I could knock up. I like the look of the near 10" flywheel used on a couple of the Clarkson engines and a similar style is used on Anthony Mount's Waller Table Engine so I decided to do one like that at 200mm diameter.

I originally just ordered some 203mm x 12.7mm wall (8" x 1/2&quot tube for the rim but the wall was actually a bit thinner and by the time I had cleaned up the hot rolled surfaces things would have looked a bit skinny so I decided to use this as an outer rim that could be slipped over an inner one which had the added advantage of hiding the holes for the spokes.

I made a start by cleaning up the OD, facing the edge and boring out the inside on which I left a small 0.3mm step half way in so that I could locate the inner rim against that.

I then reversed the ring in the chuck and faced it back to a little over finished width

Not the nicest steel to machine, a CCGT insert seemed to work best but did not break the chips so ended up with long swarf.

Having a change from the big stuff I did the spokes next, six pieces of 10mm steel were sawn off, faced to the same length and after heavily ctr drilling both ends one was tapped M4m the other M5, the deep drilling still offering a surface for the ctr to locate in. A short length of each was reduced to 9mm diameter and then using tailstock support the central section was taper turned from 8mm to 7mm leaving "bosses" at the ends of 10mm and 9mm. Here I am half way through the taper turning.

The bub was bored undersize and then turned to a pleasing profile before being transferred to the spin indexer to have 10mm dia pockets plunge milled for the thick ends of the spokes and also drilled & tapped M4

Using some short lengths of M4 threaded rod the spokes could then be screwed into the hub and drawn into their pockets, quick assembly to see how things are looking

For the inner rim I used a 25mm long slice of 203 x 25 tube which meant even more swarf as that was the only size that would give what I wanted.

This had the stepped OD turned, bored out to size and faced, not easy to see but I have also rounded over the inner corner to a 5mm radius

To stop the swarf pile getting too large I decided to part off the bit I wanted but to save having the ring rolling across the workshop stopped the parting tool 0.5mm short of break through and finished with a hack saw. What is left will make another flywheel. The rough side was then faced and the corner rounded over

Test fit of the two part rim, just needed alight tap with a nylon hammer so will go together with loctite.

I then drilled six equally spaced 9mm holes around the inner rim to locate the smaller ends of the spokes and deeply countersunk then so I could use M5 socket CSK screws to "true" the wheel much like you do on a bike wheel.

In my excitement of putting it all together I forgot to take a photo but the setup was to hold the inner rim in the lathe chuck, poke the spokes through the holes from the inside out and then bring the hub into position by holding it with teh tailstock chuck. I could then apply a bit of JBWeld to the spoke ends,, screw them into the hub and then add the CSK screws to pull it all together. A section through the assembly may help to show that.

After Loctiting on the outer rim I once again set it up in on the lathe to skim the outer rim and finish bore the hub so all will run nice and true. After test running some fillets of bondo will be added around each boss to get the "cast look" I also opted for a taper gib key rather than Stuarts grub screw.

Trial fit

[Roderick JenkinsParticipant @roderickjenkins93242]

Watching and learning. Thanks.

Rod

[JasonBModerator @jasonb]

Thanks Rod

Well I thought that I should at least use one Stuart casting as it would not really be a version of the James Coombes so Santa gave me a cylinder casting to modify.

You quite often see the comment that todays Stuart castings are not as good as the old ones but from what I have used over the last few years they have all been fine, this was no exception. Small amount of thin flash and a bit of material where the iron was poured better to have that proud than over fettled and cutting into the surface

Couple of minutes with files and it cleaned up nice enough and ready to machine.

I used the method that I came up with on the Real to machine the cylinder to ensure the bore, piston rod end and port face are all square to each other. Firstly packing up the vice on the lathe cross slide and then further packing the casting in the vice using feeler gauges to get the ctr line of the bore to the required height. You can also see I have thin strips of aluminium between the jaws and the casting so I get a good grip on the cast surface,

When setting up ensure some of the piston rod end of the casting is protruding beyond the vice jaws. Finally use an edge finder in the tailstock to set the casting central to the lathe axis and lock the cross slide.

Machining starts with a between ctrs boring bar, three passes were enough to get to size in this case I went with 25mm on the metric version. So as mentioned in another theard it is possible to use old castings from imperial designs for metric engines, the stroke was also altered to 50mm rather than 2"

Next the top end of the cylinder can be flycut down to the final size.

Now WITHOUT removing the work from the vice transfer to the mill and the port face can be machined ensuring it is true to the surfaces machined on the lathe. I also used the facemill to clean up the two flat areas either side of the portface, their 0.8mm tip radius leaving a nice fillet in the internal corners. No sign of any hard spots either.

Changing to a 3-flute milling cutter the other edges of the port face were cleaned up. happy to say that the cast in ports were very crisp and even so needed no further work.

The last job while things are set up is to drill and tap the holes for the studs that retain the valve chest and it's cover. These did not end up getting used see next post.

The cylinder can then be held with the machined end facing down and the other end milled to bring the casting to final length and while it's like that may as well tap for the stud holes. the ports were a tiny bit off from ctr at the ends so the stud holes just ran into them but not a problem and would not have affected things with the smaller number of studs used on the Stuart design

[JasonBModerator @jasonb]

I'd been contemplating how to deal with the inlet and exhaust on this engine while waiting for the cylinder casting to arrive and once I had offered it up to the rough assembled engine decided on a plan of attack.

First I needed a valve chest so machined up a suitably sized rectangular block and while I was at it a thinner one for the chest cover. I located the ctr of where the valve rod would go on the mill and drilled a small ctr hole then set this to run true in the 4-jaw chuck. Then it was just a case of drilling 2.5mm for the valve rod, counterboring 5mm for the gland and turning a spigot to form a round neck as I wanted to use round rather than oval glands on this.

Part of my modified design was to make it look like the valve chest was an integral part of the cylinder casting which is quite common on full size it is just a lot of models have them separate to make it easier to machine the flat port face. So I drilled and counterbored each corner for M3 cap head screws to hold the chest to the cylinder and tapped the rest for studs. In the next photo I have mostly completed stitch drilling out the waste using a stub length, split point 6mm drill at 5mm stepover. As you can see the holes link together, don't wander and there is no reason to spot drill first

One more hole and the waste drops out without any hammering or sawing to link the holes

The cavity was then cleaned up with a 4mm cutter , try not to get carried away at the ends of the cut

With the vice stop in place it was easy to position the cover and drill to the same pattern, the recess was cut with a 4mm dia cutter with 1mm corner radius to 1mm deep

The standard exhaust position comes too close to the conrod if taken straight out and there is not much room to put a bend into the pipe so with the "solid" valve chest temporarily screwed into place a recess for a round boss could be positioned further from the cylinder ctr line to clear the conrod

After assembling the chest and a bit of rod with JBWeld and allowing to set the boss was milled back to length, M1.6 stud holes added for the exhaust pipe flange and then after tilting the casting an angled hole was drilled to meet the central port.

Even though I'm unlikely to use them I drilled and taped for drain cocks and spot face around the holes.

last job on the cylinder was to turn a couple of decorative bands which were then cut and JBWelded to the outside of the cylinder to add a bit of interest as I di not intend to fit wood cladding.

[JasonBModerator @jasonb]

Time to knock off a few odd remaining bits and then the building should be about done.

I made the cross head slippers about 50mm longer than the Stuart Drawings show to help with smooth running and added a half round cut out each end for decoration more than reducing the reciprocating weight using a couple of plugnes of a 6mm cutter

Rather than have integral spacing bosses I turned up two steel sleeves to fit between the pivot on the end of the piston rod and the back of the slippers

Then I took equal amounts of either side until the slippers were a nice running fit inside the guides

The last bit for the upper part of the engine was the spacer rod that holds the tops of the two guide "castings" apart, I added a bit more decoration to this as the plain rod on the drawing was not that special, again I am using a small hollow sleeve on the threaded end spigot so I can use tailstock support without the need to drill a ctr hole

The piston was faced and skimmed clean from some 1" stock, drilled 3mm deep x 4mm dia for the reduced end of the 5mm stainless steel piston rod and then tapped M4 the rest of the way through. After parting off it was held the other way round, faced to length and a recess cut to accomodate a lock nut.

Then holding by the rod in a collet and using tailstock support in as mall ctr drilled hole in the end of the rod the piston was turned to diameter, ring groove cut and I also added a small Vee shaped oil groove. Th episton won't be taken off the rod after this to ensure it stays as concentric as posssible.

I needed a couple of oil cups for the main bearings so some 1/4" brass had a 4mm spigot turned on the end which was then threaded M4 x 0.5 fine and then transferred to the spin indexer to cut a hexagon

A small round nosed tool was used to cut the nick of the cup just above th ehex flange and to also skim the body down to 6mm dia

A bit of file & then emery work soon had the bottom of the cup shaped ready to be parted off

With the part finished cup screwed into a threaded holder a 4mm ball nose cutter was used to cut the inside profile and then the oil hole drilled through 1.2mm

While the brass bar was out I made a simple form tool for some drain cock bodies by milling some 9mm dia silver steel to half thickness and then used a 6mm cutter to form a 2mm deep recess in the end. The edges either side were riled round and the tool use das it was to shape a couple of valves

The flange to the right was then machined to a hex just like the oil cups and the one on the right reduced to 4mm before parting off, As I'm not likely to run mine on steam I just added dummy handles that were taper turned from 2mm stainless and bent to shape before being Loctited into place.

Well thats about it next time we can see what it looks and runs like with a coat of paint.

[JasonBModerator @jasonb]

Well this post brings the build of my Version of the Stuart James Coombes to an end and it was at least twice the fun for half the price. I went with the same Ford Ivory that I used on the Real and painted a stone effect onto the base. Quite pleased with how it turned out and I'm glad I went with the different flywheel as the larger size and lighter spokes seem to suit the look.

[Roderick JenkinsParticipant @roderickjenkins93242]

Very nice!

Rod

[WearyParticipant @weary]

Very nice build construction 'article' with some excellent transferable 'how-to' tips.

Thanks

Phil

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