Elmer’s #32 « Start Model Engineering

Elmer’s #32

The basic frame for Elmers #32 vertical engine now completed and awaiting a visit to the paint shop.

I am the first to admit that of late activity in the workshop has been almost non existent apart from a brief excursion into making acrylic torches and pens which some might argue is not proper model engineering.

My last major project was the Opus Proximus vertical engine the plans for which appeared in Model Engineer. Despite considerable effort on my part it still doesn’t run and has been deposited in my non-runner gallery which fortunately doesn’t include too many abandoned projects.

Anyway, onwards and upwards and after lengthy procrastination I have started building Elmer’s #32 Open Column vertical engine which is a similar engine to the Opus Proximus but one which I feel more confident will perform as Elmer planned. I have decided to build this 50% larger than plan. I made a similar decision when I built Elmer’s #33 Mill Engine and that turned out to be one of the best running engines I have ever built. It is no more difficult to build than building to size but it does allow you to add extra detail such as split bearing holders and more bolts in the steam chest – looks so much more authentic. It clearly costs more for materials but compared with the number of hours involved this is fairly insignificant.

I ordered the basic materials from M-Machine in Darlington, you will find a link to their website under Resources on this site. As I find cutting thick plate metals an irksome task M-Machine cut the baseplate and platform to finished size.

Incidentally they cut rather than guillotine which can leave a slightly deformed or rounded edge.

: Before machining commenced the plans were converted from imperial to metric and all dimensions increased by 50%. This should provide a good ‘meaty’ model for little extra work.

: The main pieces of brass and aluminium required for the build. M-Machine of Darlington cut the aluminium plate to size and required minimal finishing.

: With a dial test indicator (DTI) it is important to make sure that the base plate is squared up and level on the mill table before machining the concave profile around the edge.

: Note the two 12mm dia. stops on the milling table to ensure the base plate is squared up correctly. It only takes a few minutes to make these stops but it simplifies the setting up of workpieces on the table.

: Machining of baseplate completed. The next stage will be to drill and tap the holes for the pillars and cylinder base plate and prepare the top platform which has cut-outs to be dealt with.

: A quick coat of etching primer is one way of providing a good surface for your marking out and unlike felt tip pen, which I often use, won’t be washed away with WD40 during machining.

: All edges are squared up and cleaned off holding the workpiece in a machine vice clamped on its side. This ensures nice square edges.

: To speed up the removal of metal I resort to chain drilling and then finish off with a milling cutter to smooth edges up to the edge of the scribed area.

: The base plate and platform have been drilled, tapped and cleaned up and are ready for assembly into the engine frame.

: The pillars are tapped M6 at the base and threaded M6 to hold the platform. Domed nuts will be sourced for the final assembly.

: The bearing blocks are machined, drilled and tapped as an identical pair to ensure correct alignment and smooth running.

: Although I plan to add some detail to the bearing blocks it is reassuring to find that the crankshaft runs freely in the bearings – so far so good !

: Time and care spent on setting up the bearing blocks on the rotary table for the machining of the arched profile is well rewarded.

: Temporary location marks on the edge of the rotary table is a great aid to accuracy whilst machining of the arch. Remember to avoid climb milling.

: A small diamond cutting disc was used to create the illusion of split bearing holders. M6 domed cap nuts provide a neat finishing touch.

Elmers#32 part two

The frame or chassis for Elmer’s Open Column engine was whisked away for a professional paint job at a nearby paint shop. It was powder coated in satin black to provide a good durable finish and care was taken to mask off threaded holes and ball race holders. It cost less and gave a much better finish than if I had done it myself with car spray enamels.

Whilst it was away I fabricated the eccentric strap and the two movement support arms. I became so immersed in machining that progress photographs were forgotten – sorry about that. My first attempt at making the eccentric strap was consigned to the scrap box but I was reasonably satisfied with my second effort.

Today I have made a start on the heart of the engine – the cylinder block. There is a big investment in both material and time so I am proceeding with extreme caution. Here is how this mornings workshop activity has proceeded.

: Radiusing the arm ends using a simple jig set up on the milling machine.

: Milling the arms as a matched pair ensures identical dimensions for both components.

: After a quick polish the finished arms will be ready for assembly onto the engine chassis.

: The tape measure provides an indication of the size of Elmer’s enlarged engine. Note that the chassis has been powder coated for a good durable finish.

: The eccentric strap with added detailing provides the illusion of a split bearing.

: The lump of brass for the cylinder block is brought effortlessly down to size in the bandsaw whilst I have my morning coffee. A temporary jig using an old machine vice was required.

: After facing each end in the 4 jaw chuck the block is transferred to the mill for drilling and milling operations. My DRO system removes the need for marking out though I employ both methods as a belt and braces precaution.

: As I am building 50% up on plan size I am increasing the number of steam chest holding down studs from four to six for appearances sake. Here I am starting the threads by hand to ensure correct vertical alignment.

: The block is offset in the independant 4 jaw chuck using a dial test indicator (DTI) and the bore drilled in stages up to 10mm

: I then switched to the boring bar to increase the bore up to 12mm to provide the necessary clearance to attack the hole with my new indexable internal lathe cutting tool.

: I reckon that the indexable tool is more rigid than the boring bar and produces a more accurate and smooth finish throughout the length of the bore.

: Before removing the cylinder block from the four jaw chuck the outer edge is turned to plan as it shares the same centre as the bore.

Elmers #32 part three

Those who have fitted digital read outs for 'X' and 'Y' movement on their milling table can locate the precise position of each bolt hole on the cylinder covers

Well I have to say that after boring something like 20 cylinders since I started in model engineering this latest attempt is by far the best in terms of machining accuracy and surface finish. I put this down to the use of my new boring bar purchased from RDG Tools and used with automatic feed. I finished up with a super smooth bore of 19.50mm – at both ends ! – now there’s a novelty. I believe reaming will be unnecessary and maybe just a little gentle lapping will give me a very serviceable finish.

The next task was to drill the inlet passageways which feed steam (or air) to either end of the bore. It’s no problem tilting the column of my mill to the specified angle of 16.5 degrees but it’s a major undertaking resetting it afterwards (although I have fitted a laser positioning device which alledgedly makes repositioning a doddle).

Instead, I opt for using a Clarke 2.5″ tilting vice purchased from Machine Mart for £15. Not the greatest precision instrument you will come across but it does the job. This combined with the clineometer app on my iPod and the required angle is soon sorted. Take great care at this critical stage as it is only too easy to get the airway out of position. When slot drilling the air inlets on the cylinder face I would suggest going a little deeper (from 4.75 to 6mm) which will increase the chance of your airway connecting up with the inlet.

For the cylinder cover bolt holes I followed the plan for the bottom cover with 6 bolt holes but for the top cover I increased the number to 8 which, in my view, looks more authentic in my larger sized interpretation of Elmer’s engine.

You may find this free bolt circle calculator of assistance during this next stage.

remember, you can click on each photograph for an enlarged image

: The cylinder block is held in a tilting vice and is spot drilled for the start of the airway.

: Aim for a spot drilled point like this to ease entry of the drill bit for the airway proper.

: Set up the required angle for drilling the airways. Here I am using a handy app for my iPod

: Once the air passages are drilled the surplus material is milled off the cylinder block. This area will eventually be covered by lagging.

: The square outboard head was machined from aluminium round after turning the cylinder bore locating lip. Centre drill a location datum point before parting off.

: The cylinder base plate or end cover seen prior to drilling for the six hold down bolts and machining into the required square format.

: Using a piece of on-line software the co-ordinates for the six bolt holes were established working from the central datum point. A digital read out system ensures accuracy.

: Offsetting the first bolt hole by 30 degrees will ensure that none of the bolt holes will interfere with the air inlet position.

: The first straight edge is milled before rotating 180 degrees to square off the opposite edge. When the two sides are formed the piece is positioned flat to mill the remaining two sides.

: Cylinder block with outboard head is trial fitted to the engine chassis and alignment carefully checked.

: The cylinder top cover is drilled and tapped to take the gland nut. The blue tape is a marker to guide depth of thread.

: The cylinder top cover, drilled and tapped, is turned down to size.

: A close fit is essential between the top cover and the cylinder for correct alignment.

: The top cover is temporarily superglued to the cylinder and the centre finder used to locate the central datum point. (Application of heat will free the superglue when required)

: Following the bolt hole co-ordinates each of the eight holes are centre drilled and drilled to 2.25mm to a depth of 11mm. The holes in the cylinder are then tapped M3.

: Each hole is now drilled to M3 clearance for the depth of cover. The number of bolt holes was increased from 6 to 8 for appearance sake.

: M3 bolts with two washers and nut are ‘Loctited’ into position then the threads cut off flush with the nut using a diamond wheel on a Dremel type tool.

: With one of the two washers removed and the nuts inverted it just remains to clean up the thread ends with a small needle file.

: The piston blank is mounted onto the piston rod for final turning to size to ensure concentricity.

It occurs to me that my descriptions may not be too clear to some. If anyone would like me to expand on any points on this, or any other posting, just drop me an email at john(spam)@start-model-engineering.co.uk removing ‘you know which bit’ from my email addy. Please remember I am not an experienced model engineer and my methods may not be the correct way of doing things.

Elmer’s #32 part four

The 'heart' of Elmers vertical open column engine is nearing completion. Note the addition of bolt-on inlet and exhaust manifolds and additional bolts on steam chest cover.

This stage is concerned with the fabrication of the steam chest and air control valve. Built according to plan (enlarged by 50% from Elmer’s original). The only deviations relate to added detail in the form of six, in place of four, hold down bolts on the steam chest. The two additional bolts are dummies simply attached to the cover but, in my view, improves the overall appearance. The other modification is the addition of inlet and exhaust manifolds which again add a little authentic detail.

A further point worth commenting on is the fabrication of the valve rod which was made in two pieces – rod and attachment clevis. Easier to produce in two pieces and also provides some adjustment should this be required during the final setting up.

Now that the ‘heart’ of the engine has been completed the remaining work concerns the fabrication of the running gear – linkages, crank and flywheel. Doesn’t sound too much but will inevitably take longer than I think. Domestic issues will mean there will be a break of several days before production re-commences.

: A brass blank is carefully set up in the independant 4 jaw chuck with the aid of the DTI (dial test indicator). This is a procedure that does become a little easier with practice.

: The end sections of the steam chest are turned down to size. A central hole is then drilled for the valve rod and the entry end drilled and tapped for the gland nut.

: After marking out the cut-away area for the steam chest four corner holes are drilled just within the scribed lines. Clearance holes for the hold down bolts are also drilled at this stage.

: Working in a clockwise direction to avoid climb milling the bulk of the material is removed and light final cuts are taken up to the scribed line.

: A suitable piece of brass flat was flycut down to the required thickness for the valve plate. A mirror finish on this piece is highly desirable.

: A good level of precision should be aimed for when drilling the air (steam) holes on the valve plate. The plate will be cut from the main piece of stock when machining is completed.

: I like the appearance of inlet and exhaust manifolds and these are turned from round stock.

: Manifold clearance bolt holes are drilled then surplus material is removed using an end mill cutter.

: The valve rod was made in two pieces (clevis and rod) for ease of construction and is shown here with valve attached.

: Shaping the underside of the valve with a 2mm slot drill. I made three before I was satisfied – hopefully my care will be rewarded !

: Assembly of the steam chest and valve components. PTFE gaskets are fitted to all joint surfaces. Note four hold down bolts – the other two are dummies fixed to the cover only.

Elmer’s #32 part five

Detail view of linkage showing connection of piston rod, connecting rod to guide arms. A touch of Loctite on the screw threads should hold everything nicely in place on assembly.

With the cylinder and steam chest completed the next stage was the fabrication of linkages, eccentric and flywheel. Most of these items are relatively straightforward though it pays dividends to take your time and make each component as precise as possible. It’s tempting to rush the final stages but to me this is a mistake. Hurried workmanship now can so easily result in hours of frustration when your engine refuses to run.

One problem with Elmer’s plans is the quality, or lack of, of the pictures featured in the build notes. At first I had a struggle trying to sort out the detail of the linkage relating to the connection of piston rod and connecting rod. I think I have resolved the dilemma and the picture on the right shows my final result. I hope this is of some help to those of you following this build. I was also unsure on Elmers method of retaining the connecting links to the arms and you will see my solution in the gallery of build pictures.

By the way, with building my engine 50% up on Elmer’s plans I had to source a 4.5″ flywheel. Surfing the net took me to martins models I can highly recommend these top quality flywheels, beautifully cast with an excellent selection of styles and sizes. At the moment the $20 flywheels come into the country without attracting customs and excise duty which currently applies on items exceeding £18.00 in value.

So with a glimmer of light at the end of the tunnel I set about the final stages of completing Elmers #32

: Studs were made for both guide arms from 3mm stainless and threaded M3 at both ends. After silver soldering the centre piece was cut away.

: As I din’t have a convenient piece of 50mm dia. brass the crank wheel was fabricated from aluminium plate and rough cut by hacksaw.

: The ‘Flinstone’ styled wheel was clamped up in an arbour and turned down to size. Note ‘rough cut’ index cutter in toolholder.

: Over to the mill for shaping the crankwheel. A large diameter end mill provided the profile I needed.

: Switching from horizontal to vertical was the best way of arriving at the final shape for the crankwheel.

: After cleaning up the spokes with a hand file the flywheel was set up in the three jaw for final finishing.

: A drill bit holds everything in place during trial assembly of linkage. This is the pic that is hard to decipher from Elmer’s build notes.

: Trial set up of crankwheel and flywheel on crankshaft. Everything checked for smooth free running.

: Testing the motion of the running gear. Care and accurate maching will have paid you dividends when you arrive at this stage.

: Any slight stiffness in the running gear will disappear during the running in process. More serious binding needs to be sorted before proceeding.

: My final machining job was the eccentric. You need a 4 jaw independant chuck for this – simply follow Elmer’s build notes.

: The completed eccentric turned from mild steel bar – the final piece in the jigsaw.

: An overhead view of the crankshaft, flywheel and linkage down to the cylinder and steam chest.

It was at this stage in the proceedings that I couldn’t resist putting some air through the engine to see if there were any signs of life and I am pleased to report that after just a few minor adjustments my new creation burst into life !

Elmers #32 part six

So here we are, another model to add to my small collection. For visual effect I have added insulation lagging to the engine cylinder in the form of strip hardwood procured from my local model shop. The engine runs well on very little air supplied in this case by my ‘fridge pump based silent compressor. As with all new engines both the volume and pressure of air or steam drops significantly with an hour or so of running in.

All in all a very satisfying engine, particularly so at the increased size. Elmer’s original plans are available here for download free of charge. Unless you fancy having a go at making your own, attractive top quality cast flywheels are available from Martin Models.

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