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‘Johnboy’ Stirling Engine – part 6

John — Tue, 15 May 2012 15:45:37 +0000

The Completed Engine Running

Click here to view the embedded video.

And there is the finished (or at least completed) engine. It should now run. And here it is with the chamber sealed up with tape and running. But it is running more slowly than I would like. It should do better than that; about 60rpm on recently boiled water. The problem is that the crankshaft bearings are squeezed up a bit too tight. They need a small amount of endplay to stop them from binding. The solution is to make a new crank disk Item 7 or flywheel centre Item 9. But in fact, I am not happy with the join between these items being in the middle of the crankshaft. So change of design and make new crank disk and new flywheel centre.

A New Bearing Group

First turning the outside to diameter, then the flywheel mount and check for fit. Then the bearing mount with its built-in washer, and check for fit. Then spot drill, drill the 6mm hole for the crank disk and drill through 3.2mm. Lastly, the flywheel centre is parted off, reversed in the chuck and bored for the cap screw. The crank disk is turned to diameter followed by the bearing mount with the built-in washer and the bearing checked for fit. When the spigot for the flywheel centre has been turned, the bearing assembly can be checked for fit, including the all-important end play that was missing before. All that remains now is to drill and tap the crank disk, part it off and drill for the crank pin.

The Modified Engine Running More Freely

Click here to view the embedded video.

And the complete engine doesn’t look any different, but the reduced friction lets it run faster.

‘Johnboy’ Stirling Engine – part 5

John — Tue, 15 May 2012 15:45:19 +0000

The Flywheel

The flywheel is held in the 3 jaw chuck and faced, drilled to depth and bored. This is the smaller diameter bore which is the deep one. I had previously checked that the chuck could fit in this bore and expand to hold the flywheel so the outside diameter could be turned when the flywheel is reversed. The flywheel is only drilled to the depth of the bore at this stage. It will be drilled through later. With the flywheel reversed and held on the inside of the bore, the outside is turned to diameter, the flywheel is faced to width, drilled to the depth of the bore and bored. Photos 790 – 805 And lastly, the flywheel is drilled through and bored to fit the flywheel centre which can then be glued in place with Loctite 603.

Finishing the Vertical Plate

The vertical plate that was previously marked out is now cut roughly to shape with the hacksaw and then shaped on the disk sander with the aid of the guide cut from the bearing block. And the engine is nearly finished. Only needing the balance weights.

Counterweights and Balancing

Photos 835,840 The piston counterweight Item 14 is just turned from brass rod and drilled. Just move it along the rod until it balances the piston. The only catch is to ensure that it does not foul the ball chain. A 6mm length of 3.2mm brass tube is crimped to the end of the ball chain (just sort of pein it over by tapping with a pair of pliers). And then just pinch the tube in a bit and push it onto the displacer stem. Balancing the displacer is a pain. There is no way to do it except to start with a balance weight that is just too heavy and to keep putting it back in the lathe and cutting bits off until it balances. It doesn’t have to be exact so if you cut off a little too much, just leave it.

‘Johnboy’ Stirling Engine – Part 4

John — Tue, 15 May 2012 15:44:10 +0000

The Glass Cylinder Liner

Now it is time to cut the glass syringe to make the cylinder liner. I used a diamond wheel in an air grinder with the syringe held very gently in the lathe (and with suitable protection for the lathe). It takes a long time and must be done gently. The diamond wheel heats the glass quite a bit and I later learned that applying water with a small brush will cause the glass to break (fairly) cleanly. It can then be cleaned up on a diamond lapping plate. Not knowing this at the time, I had to cut almost all the way through and then to clean up the edge with the face of the wheel before using the diamond lapping plate. The cylinder was then set in the cylinder block with silicone sealer to allow a little room for differential expansion.

The Piston

The piston is turned from aluminium bar, checked for size, spot drilled and counterbored. Photos 660 – 680 The piston is then transferred to the mill/drill for cross-drilling before going back to the lathe to be parted off from the bar stock. The piston fits nicely in the cylinder.

The Displacer Assembly

The displacer core is simply turned and checked for size with the CD that will form the displacer disk. But it is not parted off yet because it can be used as a mandrel for turning the displacer disk to size. The displacer disk is held on the mandrel using the core that was used to centre the bearing block pressed up with the live centre. My indexable parting tool has a sort of vee shape that holds the disk in the centre of the tool while it is being turned to size. The size in this case is about 4mm smaller in diameter than the inside diameter of the acrylic cylinder. Putting the displacer disk together with the core and stem completes the displacer assembly.

The Acrylic Cylinder

Once the displacer assembly is fitted to the engine, its stroke can be measured. We need about 2mm clearance from the plates at the top and bottom of the stroke so the width of the acrylic cylinder can be measured, remembering to account for the rebate on the top and bottom plates. And then it is back to the mill with the kitchen canister pressed up to the slitting saw to cut off the cylinder. Once again being very careful and holding on very tightly. And here is the engine sitting on its cylinder.

‘Johnboy’ Stirling Engine – Part 3

John — Tue, 15 May 2012 15:43:49 +0000

The Wheel Assembly

We can’t use Bogs’ method to hold the wheel on the lathe because it has to have a large hole drilled where the centre would hold it. Instead, it was held on the rotary table together with a piece of scrap for use as a mandrel and both were drilled together. The larger holes in the wheel were first drilled tapping size through into the mandrel and then drilled to their correct size. Then the holes were tapped and the wheel blank bolted to the mandrel. It certainly wasn’t going to move with four screws in it. With the wheel indexed in the 4 jaw chuck, the outside of the wheel was turned to diameter, the groove in the rim cut with the parting tool turned to 45 degrees and the hole drilled in the centre. Then after a check was made to ensure that the groove was deep enough for the ball chain, the wheel was removed from the mandrel.

That’s enough of the 4 jaw chuck for the present. The wheel centre was turned from bar stock held in the 3 jaw chuck and checked for diameter and length using the wheel. The excess length was then trimmed off and the hole drilled through after which the rest of the centre was turned to diameter with the parting tool and then parted off. This little washer has two functions: it stops the bearing from rubbing, and its thickness can be varied if required to ensure that the wheel lines up with displacer stem. It is conveniently turned from the same stock as the wheel centre since that stock is already in the chuck. I just used the parting tool to form the little projection. Drilling through before parting off (like I did) always leaves a flash. I have since learned that it is better to part off almost all the way and then to drill through to break it off. This leaves minimal flash.

The spacer is simply turned, drilled and parted off and that completes the wheel assembly. Photo 515 Here we see the bearings, the spacer and the washer fitted to the vertical plate. The wheel centre slides over the bearings and is glued to the front bearing (only) with a tiny bit of Loctite being careful not to get any in the bearing itself. The wheel is glued to the wheel centre with Loctite. Now is the time to check that the ball chain is lined up with the hole and to adjust the size of the washer (by making another one) if necessary.

The Pushrod Assembly

The pushrod pivot is first cross-drilled before being turned and drilled on the lathe and then parted off. I used the parting tool for all the lathe work. The pushrod is made from 2.4mm brass rod with pieces of 3.2mm brass tube either soldered or glued in place. It is then cross-drilled for the crankpin and the little end pins. In my case, these pins were taken from a needle roller bearing and were 1.65mm diameter so I drilled 1.7mm. An alternative is to cut pins from the shank of (preferably broken) 1.6mm drills which is quite soft and easily cut. The holes should be drilled to suit.

I tinned the ends of the pushrod and the displacer rod and sweated them to the pushrod pivot with a hot air gun to avoid the inevitable solder marks associated with the use of a soldering iron. It is important to ensure that the holes in the pushrod line up with the bearing hole in the pivot since any difference will cause friction. If the 3.2mm brass tube has been glued to the rod with Loctite, it might be necessary to use a heatsink to avoid destroying the joint when the assembly is heated. Alternatively, you might try using Loctite to attach the rods to the pivot – I have not tried this. The pushrod bearing is turned from silver steel (because that is what I had), checked for size, drilled and tapped. The wheel assembly and pushrod assembly can now be added to the engine.

‘Johnboy’ Stirling Engine – Part 2

John — Tue, 15 May 2012 15:43:24 +0000

The Crank Disk

The outside diameter of the crank disk was next turned from a length of bar in the 4 jaw chuck (again, just because the 4 jaw was in situ). Then the bearing mount was turned leaving the small built-in washer to stop the outside of the bearing from rubbing on the disk. And, of course, the bearing was tried to ensure that it fitted. Then it remains to drill the 6mm hole, drill for the M3 thread, part it off and tap M3

The Flywheel Centre

The outside diameter of the flywheel centre is next turned to size followed by the section on which the flywheel will sit, and then the bearing mount. Again, there is a small built-in washer to stop the bearing from rubbing. The spigot for the crank disk is turned to fit the hole in the crank disk and then it is possible to check the assembly to ensure that the bearings and spacer fit between the crank disk and flywheel centre. Then the flywheel centre can be spotted, drilled through and parted off. And we have a bearing group to add to the engine. Here is the engine with the bearing group fitted.

A New Vertical Plate

The misaligned holes in the vertical plate were annoying me so I decided to make another one. This time, instead of marking it out, I used the indexing facility on the mill/drill (dunno why I didn’t do that before). The plate was squared and dimensioned, the mounting holes drilled and countersunk, and the hole drilled for the start of the bore. Two clamps were not enough. When I started to bore the hole, the plate moved. So it had to be indexed again and more clamps added. With the new setup, the hole was bored, the bearing mount tested in the hole and the new plate fitted to the engine. And this time, the bearing mount fits much better.

For some reason, it now seemed like a good time to mark out the new vertical plate. Note the use of the guide cut from the bearing block. Back to the top and bottom plates. The first task is to cut the rim from the kitchen canister to get an accurate measurement of the diameter and the thickness. This was done by holding the canister to a slitting saw in the milling machine. I have not found an alternative to this process which feels very awkward as the saw tries to whisk the canister out of my hands and/or to weld itself to the plastic. The canister has to be held very tightly with both hands at all times.

The Top and Bottom Plates

Once the dimensions are obtained, the top and bottom plates are stuck together with double sided sticky tape and a rough outline drawn on them (mainly to check that they are big enough). After the edges of the plates are roughed out with the hacksaw and disk sander, they are held on the chuck using Bogs’ method and turned to the outside diameter.

John (Bogstandard) Moore showed that plates like these can be simply held by the friction of masking tape on the chuck jaws and the plates, with the plates being pressed against the chuck with a revolving centre. As long as light cuts are taken, even with the interrupted cuts on this job, the tape does provide enough drive. A problem arose when I attempted to cut the rebate in the plates. By this time, the plates had become quite hot due all the work on the circumference. In retrospect, I should have realised this and given them time to cool down. Instead, I pressed on and the double sided sticky tape let go and allowed the plates to slip. Rather than mess about, I pulled them apart and attached each one separately to the chuck using Bogs’ method and turned the rebate on them. And ended up with two plates that fitted nicely on the canister.

‘Johnboy’ Stirling Engine – Part 1

John — Sun, 13 May 2012 13:47:12 +0000

The Finished Engine

‘Johnboy’ is a Stirling Engine designed and built by ‘Aussie’ Jim to run from the heat of a cup of coffee (or any other heat source at about that temperature).

This particular engine evolved from similar designs to suit Jim’s concept of a good looking engine.

'Aussie' Jim (Greethead), a regular visitor to the UK

Jim has not only agreed to debut this truly impressive example of a Stirling engine on this site but also make freely available his CAD drawings in PDF format for you to download.

To me, one of the big attractions of this engine is that it is fully house trained. You can run it indoors simply by standing it on a beaker of hot coffee to impress your family and friends.

Jim has also produced the following series of photos and build notes to help you on your way. So make a start by downloading the PDF plans right here.

Johnboy Drawing Pack V2

…. and now it’s over to the man himself who will take you through his build step by step. Thanks Jim.

Cutting Out the Flat Plates

Getting started

The acrylic cylinder is cut from a kitchen canister which must be purchased before construction commences. The canister should have a diameter about 100mm and a section that is reasonably parallel for about 25mm. The diameter of the canister affects the size of the Top Plate (Item 2), the Bottom Plate (Item 1), the Displacer Disk (Item 2) and, of course, the Acrylic Cylinder (Item 3). Once the diameter of the canister is known, the flat plates can be roughed out.

Drilling the Top Plate

The flat plates can be cut on a circular saw. The saw shown uses a carbide tipped blade designed for cutting metal but for aluminium, any carbide tipped blade with a reasonable number of teeth can be used.

Once the plates have been cut out, the holes in the top plate can be drilled and countersunk. We will leave the rest of the plate until later.

The Vertical Plate

Turning now to the vertical plate, it is first squared up in the milling machine before being marked out.

Then it is back to the mill/drill for the holes to be drilled and countersunk. Using the holes already drilled, that plate was secured to a piece of MDF and indexed in the four jaw chuck to have the hole bored for the bearing mount. I have used this method on a number of occasions but I have a feeling that the work is able to move slightly because the screws move in the MDF.

The Cylinder Block

The cylinder block is made from 25×25 aluminium bar which just needs to be squared off and cut to length. With the 4 jaw chuck still in the lathe, it was convenient to use it for this purpose. Back to the mill/drill to drill the mounting holes for the vertical plate.

The cylinder on this engine will be cut from a glass syringe to minimise friction. I have successfully used an aluminium piston in a hole bored directly in the cylinder block but since I had part of a syringe left over from a previous project, it seemed like a good idea to use it. For preference, the piston diameter should be about 14mm; the force on the piston being proportional to its area, a smaller piston will produce less power.

The hole for the glass cylinder liner can now be bored and checked for size using the syringe itself in this case (not shown). The remaining holes in the cylinder block can now be drilled and tapped and the other plates attached to it.

The Bearing Block

The bearing block can now be turned to size, spotted, drilled and bored to accept the bearing. The 4 jaw chuck has been used in this case simply because it was on the lathe. It is convenient at this stage to turn the end to fit the vertical plate and then part off a short length to use a gauge or guide when shaping the top section of the vertical plate on the disk sander (it’s easy that way and does a reasonably good job).

Then we turn another section to fit the vertical plate and part it off. And that is the bearing block (almost) complete.

Next up is Item 6 Spacer which is a simple turning and boring task. And the bearings and spacer should now fit in the bearing block. It is important that the mounting holes for the bearing block be located across the diameter. So the first task it to turn a plug to fit in the hole in the bearing block. Then the bearing can be centred on the mill/drill, the mounting holes drilled and then tapped. And then the bearing block can be added to the engine. At this stage, I was not happy with the way the bearing block fitted the vertical plate. I had to relieve the holes in the vertical plate to get it to fit. Considering the way the bearing block was made, I suspect that the holes in the vertical plate are not quite across the diameter. If I get enthusiastic, I will make another vertical plate.

Glowing balls

John — Mon, 09 Apr 2012 10:03:08 +0000

Ralph's Glowing Ball - ain't that pretty ?

Ralph (aka Dividedhead) who brought you the amazing LED mini torch/keyfob followed by his ‘Glow in The Dark’ keyfobs has now taken the ultimate step forward with the introduction of his Glowing Ball !

This combines both LED and GID technology and doesn’t it look good ? (You can check out how to make Ralph’s LED torch and GID keyfob in earlier posts). You can either make your own ball turning tool and I will try and persuade Ralph to show you how he made his or you can buy one here.

Now over to the Land of my Fathers where Ralph will show you how to make your very own glowing ball.

“The idea arose from an e-mail conversation with John Somers where he suggested I made a self illuminating mini disco ball.

I got the wrong idea and went off with this below, whereas John meant fibre optics etc.

Anywho, whilst I thought John’s idea was too hard for my current capabilities I could in my mind machine my version. so…….”

A quick repair

John — Mon, 09 Apr 2012 08:17:19 +0000

There’s no doubt that it is very satisfying to be able to carry out little repair jobs for other people. Recently a friend told me about his early Stuart Turner steam engine he had had from being a young boy. After failing to run after standing idle for many years it had been stripped down and the parts fortunately saved in a jam jar.

The problem turned out to be nothing more than a corroded connecting rod. As this was a double oscillating engine the con rod runs through the bottom cylinder cover. Standing condensate in the cylinder had eaten away the con rod to the point where there was insufficient seal for the engine to run. I suspect that the situation was compounded by the deterioation of the cylinder cover gaskets.

Some of you may wonder why the opportunity wasn’t taken to polish up this little engine. Well, personally, I prefer the genuine aged patina of brass and fortunately so does the owner.

Emptying the jam jar revealed all the components for a very nice double acting oscillating Stuart Turner steam engine including the corroded connecting rod which had brought about its demise.

A new piece of 2.5mm rod proved to be a perfect air tight fit in the cylinder cover and was threaded both ends by hand turning in the lathe.

The contact faces between the engine pillar and cylinder were cleaned up on fine grade emery resting on a sheet of plate glass.

New gaskets were cut from 0.25mm PTFE sheet which I find to be an ideal material both to work with and also to provide an efficient seal.

The engine was reassembled and after a couple of flicks of the flywheel away she went running as sweetly as ever before being returned to her grateful owner.

Click here to view the embedded video.

Elmer’s Wobbler, a Turkish Delight

John — Sat, 24 Mar 2012 13:08:19 +0000

My name is Unal Kazak,

I am not an engineer, but on the other side of the walk. I studied monumental sculpture and design.

My interest to the metal workshop and model engineering is just a hobby, for I like engines and mechanics. I design small mechanical robots and for that I keep needing hard to come by or complicated machined parts. So, I quite often found myself ordering materials and begging from local metal shops to be custom-made. Of course they drag their feet to do it, even though I pay satisfactory for them. My parts from the projects were tiny and required complicated and uncommon machining. Often after coming home I would need to correct them by filing and re drilling etc.

Eventually I decided to produce them all myself, after throwing away much needed part was machined carelessly and ruined of course. I ordered my first mini lathe simply out of curiosity to see if I could make some of the easy parts myself. So, talked to my wife and occupied one of the rooms 0n the first floor to turn into a workshop. I already had some of the essential tools. But the new lathe was something else. (It was like bringing a full grown tiger to your back yard as a pet, for kids to play with). It had its own space, special tools, noise and the chip’ lings to go with it. “It” was no joking matter, but, very friendly. Soon enough we all get used to it. After messing up several cutters and plenty of work pieces, we now get along fine.

I still kept taking some parts to local metal shops to be milled. Than as you guessed, here comes the Mill, a band saw and a bench grinder to go by. Having these two machines side by side in 3X3m room and all the other tools, benches, vices, I had no excuse to go to the industrial parts of the town to waste anymore time and money. Now, I only go there to buy some raw materials for turning and milling.

I had been watching quite a while for model and steam engines but had no courage to start. I was also browsing some model engineering sites on the internet, but they were all advanced and I couldn’t bring myself even to ask them a question, than I saw this site… And I decided to write to John Somers. I am glad I did it. He was very helpful, inspiring and encouraging kindly pointing me in the right direction… and what came out of it? Well, here it is, my first engine;

Elmer’s #25 Wobbler. I still have to polish and perfect it. I admit it was a thrilling challenge and experience.

“Thanks for the support, John.”

Unal Kazak,

Mersin/TURKEY

Elmer’s #25 Wobbler

The adventure begins ! I was extremely focussed and careful. I used very sharp cutters and constantly watched RPM and feed speeds. I measured twice and measured once more before cutting. I tried to follow all the rules and played by the book. I even wore safety glasses over my close up glasses which in the past I often ignored.

Wear yours too. You know there is saying that “Wear your safety glasses! Even, if it saves one of your eyes, for one time.., it is worth it…”

……..and now, the completed wobbler

Elmer's #25 Wobbler engine recently completed by Unal Kazak from Turkey.

Congratulations to Unal for the excellent workmanship in completing Elmer’s #25 Wobbler.

Also a big thank you to Unal for taking the time to record each stage in the build project. I know from my own experience that when you become intensely involved in the build taking photographs can be an intrusion.

Bogs’s Paddleduck

John — Thu, 02 Feb 2012 16:41:24 +0000

Ian from New Zealand with not one but two completed 'Paddleducks'

Ian from New Zealand is clearly no beginner in the world of model engineering, as you can see from these beautifully presented model steam engines. The two ‘Paddleduck’ twin cylinder slide valve engines were designed and developed by our own Bogs (aka John Moore) for marine use.

An important feature is that they are self starting in the sense that they will start running when steam is applied without the need to ‘spin’ the flywheel which is the case with many model steam engines. With model boats it is a very desirable feature to be able to start and control engine speed by radio control.

Not only are these engines well respected throughout the world of model boats they are an interesting challenge to model engineers who may have achieved some basic experience in machining metal. During the course of the build I can guarantee you will develop new skills and learn to improvise in situations where you may not always have the ideal tooling to hand.

FREE PLANS AND MANUAL TO DOWNLOAD

The plans for the ‘Paddleduck’ engines are available to download free of charge by courtesy of Bogs and also of Rob who hosts the plans and is the man behind www.machinistblog.com.

Not only can you download the plans there is also a build manual written and illustrated by Bogs which in my view is one of the finest publications ever produced for the model engineer. Visitors to Robs excellent site will find much to interest them.

There is no doubt that if this manual had been ‘officially’ published it would have been a ‘best seller’. But Bogs being the generous guy he is doesn’t seek any financial reward for passing on his skills and experience.

The build manual runs to over 100 pages and clearly takes a while to print out but believe me it’s well worth the effort. Even if you don’t build the ‘Paddleduck’ there is so much information and inspirational ideas presented in Bogs’ inimitable entertaining style that it is a great source of help and advice whatever you are building. So print it out and have it spiral bound at your local stationers as a permanent source of reference.

Download free plans and manual at www.machinistblog.com

Glow in the dark keyfob

John — Mon, 02 Jan 2012 10:46:20 +0000

Shiny key rings that glow in the dark. Lovely little presents for family and friends.

The brass keyfob cage, an enjoyable machining operation on your lathe and mill.

One of the most popular items on this site is the feature on making a small brass keyring torchby Ralph aka Divided Head. Now Ralph (who likes shiny things) is back from deepest darkest Walesland with another bright project to lighten up the winter months. This is a nice easy project though it is designed for model engineers who have both lathe and mill. Whilst too late for Christmas this latest offering from Ralph makes an ideal little gift and offers light relief to those battling with a larger on going project.

Top Tips when using the RT from the man himself

Do support the free end of the workpiece whilst machining on the rotary table.

Do remember to cross drill the tip to take the split ring.

Do cut the furthest away sections first.

Do move your support beneath the workpiece along as you go.

Do deburr after each machining operation.

Now you are going to need some supplies so you could try these for starters

Acrylic Tube

http://clearplastictube.co.uk/index.php?route=product/product&path=35_68&product_id=270

Glow In The Dark Powder

http://www.ebay.co.uk/itm/Glow-Dark-Powder-4-colours-total-40gs-/250836771133?pt=UK_Crafts_DrawingSupplies_EH&hash=item3a6709613d

My first attempt at Ralph's 'Glow in the Dark' keyfob. Having made one I think I will work to some sort of plan for future efforts.

John (site editor), has a go at making one of Ralph’s GID Keyfobs

Well I just had to have a try and thought I would try dispensing with the rotary table by using hex brass bar. Not everyone has a RT and even if they have it can be a bit of a chore setting it all up.

Even so it did take me rather longer than the hour to an hour and a half to produce my first keyfob. I am not entirely pleased with the appearance or the proportions of my first attempt but having made one the next should be a little easier. I will do myself a ‘crap-o-cad’ to work out the essential measurements with the aim of getting a more compact design.

As I only completed my first attempt this morning I am now waiting for it to get dark to see if they really do work !

Micro DRO mod

John — Tue, 01 Nov 2011 13:11:23 +0000

Regular site visitor Mike Holdoway was taken with the idea of the Micro DRO and has come up with a useful modification that extends the length of the probe.

After removing the small flat on the end of the probe, Mike drilled a 1mm hole longitudinally to a depth of 1/4″. A 1″ length of a broken 1 mm drill was then Araldited into the hole so that it protruded 3/4″. This was then enclosed in ‘chemical metal’ (Plastic Padding) which, when set, was ground to blend with the cross section of the probe with a Dremel tool.

The increased length of the probe (which is extremely strong) easily accommodated the external compression spring allowing the full length of the DRO to be used – 1.033″ although Mike suggests a limit of 1″.

In the end Mike opted for the ‘push/pull’ motion of a magnetic tip.

I must say that I find these Micro DROs brilliant in use particularly when setting the final cuts on a turning operation where precision is paramount.

Mk lll micro DRO

John — Tue, 30 Aug 2011 16:29:01 +0000

Made from an inexpensive digital tyre depth gauge available on eBay this portable DRO shown in position to measure the travel of the cross slide on a mini lathe.

The Mk lll mini DRO is an evolution of a brilliant idea from Rob in Australia. Up to now setting up a digital read out system has been an expensive and labour intensive undertaking with questionable reliability. This little gizmo can be put together in around one hour at a cost of less than £10. It snaps into position thanks to the powerful rare earth magnets (neodymium) when required and can be removed just as easily.

I regard this DRO as ideal for use on the lathe to accurately measure travel of the cross slide and carriage. We can all get within a few millimetres when turning or boring but its that last few mm or thousands of an inch that gives us either the ‘spot on’ size we are looking for or relegates the workpiece to the scrap bin. No doubt with imagination this unit can be used equally effectively on the mill.

In Mk l and Mk ll versions a spring was an important element in the operation of this little unit. However in an Eureka moment my friend, also from down under, Aussie Jim, suggested scrapping the spring and using a small magnet on the tip of the probe.

Brilliant ! The following is a step by step guide to making your own DRO unit.

Mk ll version of Micro DRO

John — Sun, 21 Aug 2011 14:29:39 +0000

Tension version of Micro DRO in position measuring travel of cross slide

One criticism of the earlier version of my Micro DRO is the reduced length of travel resulting from the space required for the compression spring on the probe.

This effectively reduces travel by something like one third. The way round this is to use some form of tension spring or even elastic to ‘push’ rather than ‘pull’ the probe out.

A while back I bought a selection box of coil springs and this contained a number of unusually slim tension springs of just the right length. If anyone is stuck in obtaining a suitable spring email me and on receipt of a SAE I will send one on.

BTW those who may be curious about rare earth magnets according to Wikipedia Rare-earth magnets are strong permanent magnets made from alloys of rare earth elements. Developed in the 1970s and 80s, rare-earth magnets are the strongest type of permanent magnets made and have significant performance advantages over ferrite or alnico magnets.

There now, you learn something everyday !

Micro DRO for less than £10

John — Mon, 08 Aug 2011 21:40:29 +0000

Reading carriage travel - range is 0 - 13 mm

A digital read out unit that will improve your machining accuracy for less than £10

I can’t claim to have come up with this neat idea and credit where credit is due. I came across this tutorial via MadModder forum at users.tpg.com.au/agnet/micro.html and it really is worth passing on to you.

The idea is based on a digital tyre tread depth indicator currently available for just £4.99 on eBay. With a few simple modifications the unit will attach to your lathe as and when required to measure cross slide travel and carriage travel to an accuracy of 0.01mm. The unit can also be switched to imperial mode. It also has potential to measure travel on your milling machine.

You will also require some 10mm x 2mm earth magnets and I bought 10 for less than £4.00, again on eBay.

So how does it work ? I hear you ask. Well, lets suppose you are turning down an aluminium round, perhaps to make a 10mm diameter piston where precision is essential. You have turned it down to around 11mm and getting close to the finished size. Right so here is what you do.

1 Using a normal digital caliper you have determined that you have turned down to say 11.10mm.

2 Deduct the finished size of 10mm from the 11.10mm and you will see that you need to reduce the diameter by a further 1.10.

3 This equates to 0.55mm radius.

4 Position your Micro DRO so that the probe is just starting to be depressed and zero the readout.

5 Wind in your cross slide until the reading is 0.55mm and take your final cut.

It really is that simple.

Upshur 4 stroke – 1

John — Sat, 18 Jun 2011 19:23:59 +0000

The Upshur Vertical Single 4 stroke engine with 3/4" bore x 7/8" stroke. Air cooled, overhead valve with wet sump lubrication.

With a successful conclusion to the building of ‘Debbie’, Jan Ridders Simple Two Stroke, the choice of the next project wasn’t too difficult. It had to be a four stroke complete with cams and valves. Once again I am just hoping I haven’t bitten off more than I can chew. Still as Bogs says ‘If you don’t try it, you will never know if you can do it’.

With ambition running way ahead of ability I had ordered a set of plans three years ago from the daughter of the designer Dick Upshur who sadly passed away in 2006. These plans are still available from Helen Whitcher for $20 plus $3 postage. The build of this engine was the subject of a series of articles which appeared in the Strictly I.C. magazine – issues 63,64,65 & 66.

Having already made a start on the crankcase, which is fabricated from six plates to form a box like structure, I came across a series of excellent posts on HMEM from Dave of Kent which included an alternative method of machining the crankcase out of the solid. Apart from a more robust construction it also neatly avoids the tricky to fabricate and securely position cam gear cover which can be seen on the side of the crankcase. As this is a wet sump engine the problem of keeping the crankcase oiltight is no longer an issue apart from a good seal on the back plate of course.

Having satisfied myself on good parallel running of crankshaft and camshaft my attention turned to sorting out the crankcase innards. First on the list was the conrod – a couple of hours work I thought, two days later I had it knocked into shape, not perfect but deemed ‘fit for purpose’.

4 jaw set up

John — Sat, 04 Jun 2011 13:49:26 +0000

With the aid of a dial indicator setting up your 4 jaw is a straightforward procedure.

The easy way to set up your independent 4 jaw chuck

Without a logical system setting up a 4 jaw chuck can seem like a nightmare. Hopefully this short tutorial will give you the gist of a simple and methodical procedure that once practiced will enable you to set up your 4 jaw chuck in a matter of minutes and with an accuracy within one thou of an inch.

I must apologise for the poor clarity of the pics but I was struggling to get a clear image of the dial reading despite trying a variety of camera and lighting settings. I even removed the glass dial cover from the dial indicator to avoid reflections.

The secret of success

Whilst the method relies on the accuracy of a dial indicator it is still important to get as close as you can with the centering procedure by eye before you bring the DI into play.

Click on pics for a larger image

Upshur 4 stroke – 2

John — Sat, 28 May 2011 22:11:33 +0000

One of the joys of model engineering is that you don’t normally have to spend a fortune on materials. If some machining operation goes belly up you can always chuck it in the scrap box and have another go without it breaking the bank. However when you have to modify an expensive bought in part you can’t afford to adopt quite the same cavalier attitude.

This was the case for the spur gears purchased from a supplier in Australia which transmit the drive from the crankshaft to the camshaft of the Upshur engine. It’s vital that these gears mesh true, in other words any wobble could result in poor running. Also when I considered the need to silver solder the stainless steel gears I became distinctly apprehensive and was more than happy to entrust the job to Bogs.

Bogs and I felt that the whole procedure could be of interest so it’s over to Bogs for a step by step account of the work involved.

Remember to see a larger image, click on picture

Upshur 4 stroke – 3

John — Tue, 17 May 2011 11:14:28 +0000

A periodical assembly of parts completed to date helps to ensure that the build is on track, especially important where deviation has been made from the original plan.

Next on my list was fabrication of the camshaft. What appeared a simple little turning job on the lathe turned out to be a two day marathon and then I had to resort to finishing the cams by hand in the vice (or vise if you happen to live t’other side of the pond).

Bogs’ modified gear wheel was positioned on the shaft and secured with a keyway cut with a modified blade from my hand held power jig saw (thicker than your conventional hack saw blade). A 1.5mm pin was inserted into the shaft to serve as a key. Again I must thank Bogs for this neat idea.

Cam followers and guides were turned up and slotted into position. The smaller 30 tooth gear wheel was added to the crankshaft and on assembly I was rewarded with a smooth running ‘bottom end’.

I was not looking forward to the next job on my list – the production and fitting of piston rings. As it turned out my fears were ungrounded. I simply followed the instructions to the letter and all turned out well.

With increasing optimism I took the plunge and ordered the RCEXL ignition unit at a cost of around £50 including a neat two way switch for plug in battery charger and a CM-6 spark plug. I bought mine on line from Apache Aviation and have been very satisfied with both the products and service.

When building an internal combustion engine one of the considerations is where to hide all the electrickery bits. When I built my ‘Debbie’ 2 stroke I even obtained quotes to have something made by a cabinet maker but the cost was prohibitive.I finished up making the base myself but it was a job I didn’t enjoy and the result fell short of my hopes. Now I am building the Upshur vertical single I was faced with the same problem. Browsing around fleabay for inspiration I eventually came across pet caskets – you know, the sort of thing you would buy to preserve the ashes of sadly departed Tiddles the cat. For a modest £10 inc shipping you have a neat wooden plinth. Throw away the lid (or keep it for a steam engine base) and replace with an aluminium plate and you have a perfect base for your latest pride and joy. A search on eBay will reveal all sorts of caskets in varying sizes, finishes and prices suitable for adaption into engine bases.

Remember to see a larger image, click on picture

Upshur 4 stroke – 4

John — Wed, 04 May 2011 12:42:21 +0000

A neat digital tachometer also serves as an ignition 'on' indicator to preserve battery life.

Whilst work has progressed since my last post (as shown below with my pic/captions) I have encountered a number of problems which will require a certain amount of backtracking and the machining of new parts. These problems serve to illustrate the need for high standards of accuracy in the making of model 4 stroke engines. Those guys building multi cylinder engines have my undying respect.

To all intents and purposes I had finished the engine build and thought I would see some signs of life with a temporary hook up to the vapour carb on my ‘Debbie’ Simple Two Stroke. This was a severe case of over optimism and investigation revealed a number of fundamental faults that will need rectification.

1. Lack of compression due to leaky inlet and exhaust valve seats.

2. Poor alignment of the crankshaft resulting in the destruction of main bearings.

3. Shoulder of big end bearing carrier making contact with the camshaft.

I intend to have a few days break from this project before tackling the above issues so anyone following this build please bear with me.