Vickers Inverted Engine

[JasonBModerator @jasonb]

One of the collectors on The Stuart Models FB page posted an image of his new addition a few months ago and I thought it would make a good model.

No idea if it is based on any specific full size engine or was ever offered as plans or castings but the cylinder and valve chest do have the look of Stevens Model Dockyard about them so it may have been built using one of their sets of cylinder castings. I’ve named it after the guy who now owns it.

As it was on the Stuart Group and there was some interest from others who may want to build it I thought I should at least include one Stuart casting. The proportions are not quite right to use both a 7″ flywheel and their 2″ x 1″ cylinder as this engine has a larger cylinder so I drew it around the flywheel as that would probably be the harder part for people to make. First job was to put an image into Alibre and once scaled to suit the flywheel pull a few dimensions off it. This image also shows it stood against an early Stuat No10 for an idea of size, mine will be smaller. I’ve changed a couple of bits I did not like the look of but it is basically the same.

Over a couple of evenings the various parts were drawn up and assembled, had to spend quite awhile playing with conrod length and cross head guide spacing to make sure the two did not clash but I’m quite happy with the way it looks. I will probably make my own flywheel but the image is with a Stuart one. All metric as is now my norm.

I made a start on the four panels for the base. The usual practice would be to bend up half round beading and fix around the openings. However 1mm radius beading is not available although not hard to make your own and it also has a tendancy to curl up when you want to to lay flat around a curve. Also the beading was set back only 0.5mm from the edge of the openings. After a bit of thought I came up with a cunning plan. Rather than use half round beading I thought I would try milling a 2mm wide x 1mm deep slot and simply solder some 2mm dia brass wire into the slot.

The four plates were sized on the manual mill and then over to the Cuts Nice Curves machine to do the slots and cut out the arched hole.

I use 4 or 5 tabs to retain the waste material rather than risk it coming loose and damaging the cutter or work, they are only 0.75mm high at the peaks so easily sawn through and tidied up with a file.

After straightening a length of the 2mm brass wire I filed one end to 45deg for the miter joint, clamped that end into the slot and it was then easy to push the wire down into the slot with one hand as the other guided it around the arch and back down the other side. Marke and miter the end then just a straight length for the bottom.

A bit of flux and some soft solder fixed it all together then a quick cleanup of the small amount of excess solder and they are ready for the “key stones”

 

[Nigel Graham 2Participant @nigelgraham2]

A fine project!

I have beaded an edge by slotting small-diameter tube, simply by filing it until it broke through.

It would be good to see the original restored. Does it owner intend that?

[derek hall 1Participant @derekhall1]

As always, great work Jason!

I have no experience in CAD, but it certainly is a great way to tweak a design to make sure all bits are going to fit before spending hours iron fighting, only to find some major discrepancy where the carefully made component becomes scrap…

[JasonBModerator @jasonb]

Thanks.

 

He is likely to just give it a sympathetic clean rather than the full bling restore. It runs quite nicely so does not really need any major repair.

Quick capture of the parts moving about, you can see the rod gets quite close to the bottom of the guide bars. There are a few small parts that I have not detailed yet but enough to get going. Oneday Nigel this could be your wagon.

[DiogenesParticipant @diogenes]

It’s a really nice engine – do you think the ‘architecture’ and detailing has that ‘Great Exhibition’ look about it?

It has grandeur and presence.

[JasonBModerator @jasonb]

Certainly does, The owner thinks it is from about 1850 though I suppose it could have been modeled later than that but in the style.

[Craig BrownParticipant @craigbrown60096]

Very decorative, I like it alot. No doubt will turn out lovely! Look forward to seeing it progress

[JasonBModerator @jasonb]

Thanks

I used up a few scraps of brass for the keystones, first milling to overall size then with a small vice set at 5 degrees milled the two tapering sides. After that a rebate was cut so they slipped over the brass panel, there position was marked on the panel and the bit of beading underneath cut away before soldering into place.

I know they say measure twice and cut once but I measured the 14mm square steel that I had bought for the corner posts 4 times and each was 10mm too short 😢 So I cut up some cast iron and milled it to 14mm square then faced to length ond drilled it lengthways in the 4-jaw.

I milled the lengthways 3mm slots for the panels to go into then tilted the vice 0.75deg to cut the tapering sides and lastly the bead around the top was reduced by 0.5mm all round so it protruded the same 1mm from the face that the base does.

I still need to knock off all the external corners so they look more like castings but a trial fit shows it all goes together OK.

I made a start on the bottom plate. After milling to overall size the holes to attach the corner posts were drilled and a slot cut all round for the panels to just drop into.

[StevePParticipant @stevepye68246]

Lovely work Jason .

While I procrastinate about what to do, you’ve completed the part.

The steps used to producing your 3D cad model ,are those the steps used to create your fabrications ,

or do you look a the finished cad model and then decide how to make it?

Steve p

 

[JasonBModerator @jasonb]

Steve, right from the start I am thinking of how I will make the engine. That will often be when I first see an image or old drawing right through the 3D modeling process.

What actually ends up on the computer can vary a bit, if we take what I have shown so far then some parts were modeled as the individual parts such as the base plate, and corner posts. But for the panels I modeled the completed sub-assembly of plate, beads and keystone as one part.

This is due to the fact I have it in my head how I will make the fabrications and depending on their complexity may just work with that or go back and split the part down into the individual items. The the case of the end plates as I intended to CNC cut the aperture and slot I went back up the tree of features and altered the sketch of the protruding half round bead to a rectangular slot and then exported a STEP file. What went down to the workshop was just a note on the overall sizes I needed to machine the plates to and a quick hand sketch of the keystones with a couple of dimensions and a USB stick with the STEP file on it.

For the engines that get published then I will go back and do drawings for the parts that make up the fabrication as builders won’t know what was in my head and as most published ones have been aimed towards the newcomers I think it is better to give them as much info as possible.

[StevePParticipant @stevepye68246]

Thank you Jason for your explanation.

You have considerable skill  in breaking down an intricate part into simpler building blocks for an assembly.

Having retired recently from nearly 50 years in engineering,  learning new to me techniques is what I love about engineering

,you never stop learning.

Steve p

 

 

[JasonBModerator @jasonb]

I’m not one to let a bit of cold weather keep me out of the workshop so a bit more progress to report.

Turning the base plate over I used a 3-Flute aluminium specific cutter to rough out theedge  profile then a 6mm ball nose cutter again intended for alumining to form the concave part of the moulded edge. After that I changed to a TCT rounding over router bit to produce the concave lower part and quirks. All cut very cleanly, this is without any burr removal, just a brush and wipe over.

After squaring up a piece of 3/8 aluminium for the top of the base I cut a similar slot and holes but threaded this time in the underside like I did for the base which will locate the tops of the panels and take long studs that pass through the columns and base to hold everything together. I also drilled and counterbored for some M4 cap heads which will hold the columns and bearing pedestals in place and finally stitch drilled out some of the waste material.

As I’ve not used the CNC much on the last couple of engines that I have completed I decided to use that to do the work from above which consisted of:
– A facing cut all over with a 25mm 2-insert cutter to reduce the 3/8″ stock down to the 8.5mm thickness that I wanted
– multiple full depth contour cut to finish the large central cut out 4mm 3-flute ali cutter
– Adaptive to remove the material around the 4 column bases leaving 0.3mm for finishing with a 6mm 3-flut ali cutter
– Horizontal to finish the lowered areas with a 4-flute 6mm cutter with 1mm radius corner to leave a fillet around the column bases
– Adaptive to rough out the eccentric clearance slot with a 4mm 3-flut ali cutter
– Same cutter to finish contour that slot
– Same cutter again to do the 8mm dia x 2mm deep counter bores to positively locate the column ends.

Finish is better than it looks as the light has made the tool marks look like they are rough but you can’t feel anything.

Then back to the manual mill armed with a flycutter and freehand ground HSS bit to do the flat Ovolo moulding around the top edge, not the best photo.

Then a cove cut to the underside with a wood router corebox bit.

I’ve made a start on the columns, just turning the bottom spigots and drilling and tapping the screw hole in the bottom.

The milled finish looks as it is in this photo without the light reflecting on the machining marks.

[Ian PParticipant @ianp]

As usual impressive work Jason. I have a couple of questions,

1, When did you start metalworking? (I recall seeing some of your wood creations on the old forum)

2, What is ‘inverted’ about the current engine project?

Ian P

[JasonBModerator @jasonb]

Metal work at secondary school for 5 years ending with a Grade A O level in Engineering Theory & Practice. No other engineering background. Also Got Grade A woodwork, Technical Drawings and Building construction drawing.

Got into RC buggies at around 14, then a RC helicopeter at 15 so Dad bought me a Unimat as some bits needed making on the heli. Mostly used it for repairs/upgrades on the RC stuff and must have got a Stuart 10V kit at 19 or 20 so late 80s which I built on the U3. Went onto a Stuart Beam and an Emcomat 8.6 was needed.

After that started on the Minnie around 1990 but worked on and mostly off over about 16yrs to make that. Started the Fowler in 2007 and have been doing a lot more since then.

 

Early engines tended to have the heavy cylinder at the bottom so as this one has the cylinder at the top it is referred to as inverted.

[JasonBModerator @jasonb]

Next job working my way up the engine were the columns. As with other engines to save materials I opted to machine spigots at either end to locate the bases and capitals which were machined separately. I could then hold the 12mm diameter steel by the bottom spigot and with a boring head offset in the tailstock the taper and mouldings could be turned.

The bases and 2 part capitals were fairly straightforward with a mix of form tools and files to create the mouldings on the end of a bar before parting off and repeating the process. The squares were cut from the waste material out of the base end plate arches.

After glueing the bits together with epoxy and allowing a day to set the columns were all machined to one setting ensuring they all came out the same overall length.

An old aluminium casting was machined up to 7mm thick and to the overall sizes on the manual mill before transferring to the CNC. I used that to form the four raised bosses for the column nuts, to bore the large 39mm dia hole and also drill the other various 3, 4 and 5mm holes.

Then back to the manual mill to cut the coved detail to the underside of the edges

A 7mm hex was milled onto the end of a piece of 8mm dia round and then a form tool from a previous job was repurposed to form the acorn nuts which were then sawn off, faced and tapped M4.

Starting to look more like an engine.

[JasonBModerator @jasonb]

I was in two minds whether to fabricate the cylinder from Brass and Bronze using silver solder to hold it together or to JB Weld fewer pieces of cast iron. In the end the cast iron option was the one I went for.

A piece of 50mm bar was roughed out externally, faced and then bored to 30mm diameter.

I then used a parting and grooving tool to set out the position and depth of the various diameters that would become the flanges and decorative beads.

Further cuts with this tool removed most of the waste material and also cut the 1mm x 1mm step either side of the beads.

I then made a form tool from silver steel to form the 2mm radius beads around the cylinder.

A round nose tool took care of the stepped fillets at each end to complete the turning.

With the cylinder held horizontally a flat was machined to locate the central port face and also two blocks that would form the steam passages to each end of the cylinder which you can see sitting in place.

The inner face of these blocks and that of the port plock were milled out to form the passages and some further work done on the port block to form the undercuts and the exhaust boss. These were all then bonded into the slot with JB Weld and given 48hrs to set.

The port face could then be skimmed flat, the ports milled with a 2mm dia cutter and the stud holes drilled and tapped.

Each end had it’s pattern of holes drilled and tapped and a notch was milled to link the passages to the cylinder.

[DiogenesParticipant @diogenes]

..it all looks so easy.. ..nice beads..

[Ches Green UKParticipant @chesgreenuk]

Jason,

Fantastic work –  so many skills at play.

You should open a Hobby College!

Ches

[DalboyParticipant @dalboy]

I like the way you milled the steam passages before soldering together, save drilling them from the end and en having to plug the holes

[JasonBModerator @jasonb]

Thanks for the comments.

With the cylinder complete the various bits that fit to it were next.

The lower cover is fairly straightforward turning, it is a bit thicker than your usual cylinder cover as there is an 8mm thick boss on the bottom which locates in the large hole in the entablature.

The top side just has the usual shallow spigot to locate the cylinder and was reamed 5mm for the piston rod

Some holes finish that part off, the two tapped holes in the thicker section are to take the crosshead rod guides

A quick modification of my cylinder beading tool by freehand grinding one edge to 45 eyeballed degrees allowed it to be used to form the 4mm balls on the ends of the 5mm guide rods.

The top cover is rather busy with a lot of fine moulded detail to the “cast” part

The main turning was done on the lathe but rather than fiddle about with small form tools to turn the detail I used the rotary table to rotate the cover while I used various milling cutters to form the shapes including a 6mm dia bull m=nose cutter with 1mm convex corner and a 1.5mm radius corner rounding cutter.

The valve chest and it’s cover are much the same as any other just being rectangular bits of cast iron with some holes drilled in them.

A couple of minutes each on the CNC had the elliptical boss and gland shaped on the end of the chest and a decorative recess in the cover.

[DiogenesParticipant @diogenes]

What do you make of the entablature on the prototype – d’you think it originally had a cover over the cylinder?

[JasonBModerator @jasonb]

The edge of the entablature looks a bit out of place being so plain compared with the more decorative base, I added some detail around it to tie things together a bit more. The only thing I have not been able to work out is what the two studs in the edge of the entablature were for?

As for the cylinder I don’t think it had any metal or wood cladding as there are no signs of fixing holes for any banding. Also the top flange of the cylinder is the same diameter as the cover where as it is usual to have the cover larger so it covers the end of any cladding. At the bottom as the cylinder flange is larger than the top flange that would also have made it hard to fit cladding as there is nothing for it to bear against.

The cylinder is also painted green like several other parts of the engine and you may not have painted something out of sight.

[DiogenesParticipant @diogenes]

Yes, it was those two studs (and the slabby sides) which made me ask the question – but you are right, the cylinder looks like it was meant to be seen – it’s all very nicely done right down to the fillets on the nut flanges.

Maybe the studs supported a kind of cornice or ‘trim strip’ to cover the gap for the valve rod..

Thanks very much for the extra pics 👍

[Nigel Graham 2Participant @nigelgraham2]

Lovely work!

…

Re setting over the vice to mill a shallow taper ( as you described a wee way back up-thread):

I used a slightly different approach a few days ago for the 1:100 taper on a gib-headed key blade about 1.5″ long.

On the steel bar stock, I marked a line close to the end, and another 300mmm from that. I clamped the bar to a long angle-plate, with the inner mark on the edge of a parallel, and the end mark raised on a 3mm diameter drill shank on a second parallel.

A key taper to lock in a parallel keyway is not critical within the last 0.001″ or so, as an adjustable slide gib would need. BSI says 1:100; an ancient text-book advised the range 1:96 (1/8″ : 1 ft) to 1:104. So the method is accurate enough for purpose and avoids setting and re-setting a vice.

The same book also gave the key’s head proportions: this little component will show on the finished (when…?) project so has to look vaguely right as well as work.

….

Incidentally the “angle-plate” used is actually a length of thick-walled aluminium angle machined all over, once a high-precision machine part, and with a rebate on one face just deep enough to locate against the Tee-slot wall.

[JasonBModerator @jasonb]

I do gib head keys in a similar way, just pack up one end of  a parallel or even a ruler. 1/16″ drill bit over 6″ for imperial 1:96 or 1.5mm drill bit over 150mm if doing a metric 1:100 key. I also make my own broach guides with a matching taper so I get full contact.

This was for a wedge and cotter so a bit steeper.

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