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 [...]]]>

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

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 [...]]]>

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 !

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 [...]]]> 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.

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 [...]]]>

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.

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 [...]]]>

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 !

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 [...]]]>

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.

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 [...]]]>

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’.

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 [...]]]>

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

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 [...]]]>

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.

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 [...]]]>

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.

Go on. Admit it – you’ve always hankered after building an internal combustion engine. Well I reckon with two or three of Elmer’s engines under your belt, ideally including one of the more demanding slide valve [...]]]>

Jan Ridders Two Stroke Engine for all you petrol heads !

Click here to view the embedded video.

Go on. Admit it – you’ve always hankered after building an internal combustion engine. Well I reckon with two or three of Elmer’s engines under your belt, ideally including one of the more demanding slide valve engines, you can.

Take a look at Jan Ridders ‘Simple Two Stroke Engine’ – no tricky valve arrangements to machine, no high precision crankshafts to fabricate and no fragile piston rings to cut. Mind you, you will have to brush up on your silver soldering technique. But, worry not, you’ll find a useful and practical guide to silver soldering right here

Jan first produced the design for this engine back in 2004 but the even better news is that this year he simplified his design bringing it within the scope of beginners like me and you. I hope I have not bitten off more than I can chew  as I have now started to build Jan’s engine. You will find much information and a link to free plans on Jan’s site

The plans are beautifully produced and a credit to Jan’s engineering cad cam skills. I downloaded a set and had the printed sheets wire bound and hard backed to withstand the rigours of workshop abuse. A list of materials was produced and should you run into any difficulties in sourcing specialist stock such as thin wall brass pipe for example try M-Machine Metals.  If you are not in the UK then I can’t be of much help. Sorry.

Whilst it is not my intention to produce a step by step tutorial I shall be covering some aspects of the build where I feel my experiences in overcoming certain difficulties may be of some assistance to fellow builders. I made a start by building the engine base plate and crankshaft bearing supports. I always like to get the base out of the way but this turned out to be no easy task. Compared with Elmer’s engines this engine base is big. The length of the baseplate is longer than the travel on my mill so a certain amount of improvisation in work holding was called for. The following photographs provide some indication of the first tentative steps in this project.

As always, you can view these pictures in greater detail by clicking on each image.

Despite having an absorbing build under way the highlight of my week has been a visit from George, my nine year old grandson. Together we turned an acrylic pen and George was able to try his [...]]]>

Nine year old grandson George tries his hand at turning under my watchful eye.

Calling all Grandads !

Despite having an absorbing build under way the highlight of my week has been a visit from George, my nine year old grandson. Together we turned an acrylic pen and George was able to try his hand at turning on the lathe. He showed great interest and a surprising level of understanding in lathe operation. Hopefully a seed was sewn and he’ll be back for more. One thing’s for sure he was as proud as punch with his afternoon’s effort.

So come on all you Grandads out there – get those young grandkids into the workshop. It’ll do ‘em more good and give them greater satisfaction than any amount of computer games.

Update on Jan’s simple two stroke

Now for an update on this weeks progress on Jan Ridder’s simple two stroke. The flywheel was finished off by adding holes tapped M5 to take the three retaining grub screws at 120 degree spacing around the hub using the RT set in a vertical position. Three holes were also prepared to take the cam wheel, the profile for which was machined on the RT. An afternoons trip to the shops procured two or three micro swith candidates from Maplin. These can be wired either ‘push to make’ or ‘push to break’ – the latter being the option we require for our contact breaker. A simple bracket was quickly ‘knocked up’ from ‘L’ section aluminium with allowance made to adjust the position of the micro switch in relation to the cam wheel. Whilst on the ignition topic I decided to order a spark plug rather than make my own, mainly for cosmetic purposes you understand ! Turns out that I shall need a 10mm metric FINE so unless i can do a ‘borrow’ from a friend an order will be whisked off.

A start was made on the engine cylinder using a lump of Meehanite which, according to Bogs, is a quality form of cast iron. Initial problems in opening up the bore were resolved with a quick call to my mentor who advised me to slow down the drill to a miserly 100 rpm only rising to a very modest 150 rpm when using the boring bar.

Bogs also came up with a solution to starting up the engine when completed. I had my misgivings about the rope and pulley method and favoured the possible use of my vari-speed electric hand drill to put in the effort. More of this later.

Today being Sunday, and concious of the noise normally emitting from my workshop I decided to work on the electrics. A simple rotary switch enables me to switch the internally mounted battery to ‘Ignition’ or to ‘Charge’. Using Jan’s wiring diagram I now have a healthy fat blue spark at the plug.

Click on images for larger view

As a result of a flood of emails, well just one to be honest, I have put together a few notes on how I tackled setting up the electrics on my two stroke. Let me say from the start my knowledge of the [...]]]>

Wiring as seen from the underside of the engine baseplate

Electrickery

As a result of a flood of emails, well just one to be honest, I have put together a few notes on how I tackled setting up the electrics on my two stroke. Let me say from the start my knowledge of the workings of all things electrical is severely limited. So trained and experienced electricians should look away now.

Working from Jan’s schematic these are the bits that I gathered together.

A 12V coil. The small type commonly found on classic motorcyles is ideal. I chose a 12V version rather than 6V only because I already had a serviceable 12V 2.2amp battery that had been used in an alarm standby system which would fit conveniently into the base of my engine. BTW I noticed during a visit to Maplin that they stock this type of battery.

From the same supplier of the coil (try ebay) I also picked up a condenser an essential component that acts like a tiny storage battery that charges and discharges rapidly. This I mounted on the underside of the engine base plate to provide good earthing.

A contact breaker in the form of a micro switch (Maplin ref GW73Q) complete with roller which is actuated by the cam wheel. This was mounted in position to bring the roller in contact with the cam wheel. Provision for ride height adjustment was allowed for when making the simple L shaped bracket. Important, when connecting up choose the higher of the two blade terminals and the blade terminal under the unit. This will give you a ‘push to break’ arrangement which is the required setup.

Whilst Jan provides details on how to make your own spark plug I opted to buy one ready made (Ref CM-6, Google Apache Aviation). You will also need an M10 x 1 tap, it will cost you more than the spark plug ! – buy just one, a 2nd which as you probably know has some taper and full width thread so is adequate for cutting the spark plug hole in the aluminium cylinder head.

You can carry out a bench test by connecting up all the components, observing the polarity of coil and battery. The spark plug body should be earthed by laying it on the engine base plate. If you have wired everything up correctly you will be rewarded with a healthy blue spark at the plug when you depress the micro switch either by hand or by rotating the cam wheel.

Flushed with success  I decided that I wanted some means of switching the ignition circuit on and off plus the facility of plugging in a battery charger. The simple answer is to fit a double pole double throw switch giving ON-OFF-ON. I made life a little more complicated for myself by opting for a two pole 6 way rotary switch (Maplin ref FF74R) to give the same result plus the glitz of ‘circuit live’ 12V LEDs. Wiring was very much a case of trial and error using a basic multi meter. (I wonder if Maplin will send me a Turkey at Christmas ? – no maybe not !).

To sum up, wiring up the basic ignition circuit is not difficult and providing you follow Jan’s schematic should present no problems. The switching, battery charging arrangement is very much optional. If anyone would like clarification on any of the above send me an email to john(spam)@start-model-engineering.co.uk.

Cooling fins

Now back to the engine proper. One job that I was viewing with some trepidation was the machining of cooling fins on the cast iron cylinder. Fortunately Bogs saw the potential problems and came to my rescue even before I asked for it ! I will attempt to pass on to you the key points in tackling this job. It is worth the effort in getting it right as, without wishing to fill you with alarm, a cock up at this stage will live to haunt you.

Whilst a standard 2mm wide parting tool may be OK I had the benefit of a ‘chip breaker’ cutting tool presented to me. The photograph shows the profile of the cutter which may be of sufficient guidance to enable you to grind up your own tool. Whatever cutter you opt for I would suggest you carry out one or two trial runs on a piece of scrap before starting on your cylinder.

The first thing is to ensure that your cutting tool is mounted with the cutting tip dead on the centre line, not a nadge above or below but spot on !

Next use a clock to make sure that the blade is square on to the centreline of the lathe. As the cutter does not have any side relief failure to do this will almost certainly cause jamming as you cut progresses deeper into the cylinder.

For maximum rigidity I would advise using your independant 4 jaw chuck. I have used mine quite a lot recently and setting up to run true does become much easier with experience. Make sure the jaws are tightened up really well. Tighten them progressively in opposites and to preserve your centering.

When the saddle is in the required position lock it down and make sure all gibs are tweaked up – there should be no slop anywhere in the setup.

Wind back the top slide away from the chuck (you don’t want to be running out of reach after you have cut your first groove).

Check how far your top slide travels for each revolution of the handwheel – mine gives 1mm of travel for each revolution which makes calculations nice and simple. After cutting my first groove 4 turns of the handwheel moves the cutter into position for the next one. Carry out a similar exercise for your cross slide – make a note of where the position of the handwheel should be when you have reached your 6mm depth of cut.

Lathe speed for your cast iron cylinder should be somewhere between 100 and 150 rpm. As Bogs says, don’t play with it, just give it a nice steady cut to keep it cutting. As soon as you stop that is when materials rub and form a hard skin and can make it difficult to get cutting again.

So near and yet so far. This is the stage I am at with ‘Debbie’, Jan Ridders Simple Two Stroke. Despite many days experimenting with fuel and ignition adjustments, remaking of components and every effort to eliminate any possible air leaks ‘Debbie’ steadfastly refuses to pick up her skirt and run. By the way, [...]]]>

So near and yet so far. This is the stage I am at with ‘Debbie’, Jan Ridders Simple Two Stroke. Despite many days experimenting with fuel and ignition adjustments, remaking of components and every effort to eliminate any possible air leaks ‘Debbie’ steadfastly refuses to pick up her skirt and run. By the way, the tall pipe protruding from the fuel tank is a temporary affair and was used in experimentation of the air inlet.

Building an IC (internal combustion) engine, whilst calling for similar machining techniques to the construction of a model steam engine, has given me a sharp lesson in the need for greater machining accuracy. I would strongly urge beginners to serve their apprenticeship with the construction of a number of steam engines before moving on into the more exacting world of IC engines.

Having built a dozen or so steam engines I felt I might just have sufficient experience to tackle a simple two stroke – just how difficult can it be ? I opted for Jan Ridders ‘Debbie’, a simple two stroke to a design where Jan has removed as many of the difficult bits as possible. There is an easy to construct vapour carburettor and those tricky to make piston rings have been dispensed with altogether.

I guess it took me around four or five weeks to complete the build working on average three or four hours per day – not that I was in any hurry. It would be nice to say that after adding a drop of unleaded ‘Debbie’ sprang into life – no such luck !

It is now two months later, during which time when there were many days when it was just too cold to venture into the workshop, and still ‘Debbie’ refuses to run for longer than a few seconds. The following are steps taken in my quest to get ‘Debbie’ into the ranks of runners.

Piston/cylinder bore. This is the heart of the engine and calls for a sliding fit where the cylinder internal bore is no more than 0.05mm (that’s 500ths of a millimetre !) greater than the diameter of the piston. I had several attempts at achieving this level of accuracy before I was satisfied. It was during this process that I learnt the correct way to use an adjustable reamer. I felt the need to dismantle mine to remove sticky storage wax and the way it worked became apparent on disassembly.

Ignition. Another key aspect of the build. Initially I opted for a battery, coil and contact breaker setup. This worked fine but it soon became apparent that the micro switch contact breaker had a very short life expectancy and I got through half a dozen of these during my efforts to get ‘Debbie’ to run. Having lost faith in micro switches I wondered if a change to electronic ignition might not be the answer to my problems. £60 later I had a more reliable set up but regretfully this was not the answer to ‘Debbie’s’ problems. One bonus of the switch to CDI ignition is that with the coil and larger battery dispensed with, a shallower base is now practical and this, in my opinion, results in a more pleasing overall look to the engine.

Ball valve. This is the device fitted between the carb and engine to restrict fuel vapour to flow in one direction only. According to Jan the malfunction of this valve is frequently the cause of poor or non running of the engine. I have lost count of the days spent focusing on this component in my bid to get ‘Debbie’ underway. Following a suggestion from my mentor Bogs I modified the design to a square edge ball seat rather than a taper and this certainly improved the sealing properties. A light tap with a hammer on the ball helps to form a good seal. Discard the ball after tapping and replace with a new one.

Fuel. Jan suggests using either unleaded petrol or Colemans camping stove fuel. He recommends Colemans for improved running characteristics and less odorous exhaust fumes when run indoors. It was during my many hours of adjustments to the ball valve that I discovered that there was a definite relationship between the fuel level in the carb and the willingness of ‘Debbie’ to fire up. The other feature I noticed was that to get ‘Debbie’ to fire the air valve on the carb had to be almost fully closed giving a very rich mixture. Then the penny dropped ! Air was clearly being sucked into the inlet system somewhere after the carb, thereby weakening the mixture. Close examination revealed that the seal around the piston rod appeared to be the prime suspect. I also discovered that the level of fuel in the tank directly affected the engine’s willingness to fire. I know I am not alone in having problems getting this engine to run and I am beginning to think that the piston rod seal must be high on the list of potential problem areas.

Despite all the problems I think this is a superb engine to add to my collection and this makes me all the more determined to overcome my present difficulties. I am most impressed with Jan’s take on two stroke engine design and I feel my difficulties are due more to my construction than to Jan’s design.

If Crocodile Dundee built an engine he’d build a Bonza which is exactly what my friend Aussie Jim has done. This is Jim’s first large engine and it’s an absolute beaut !

It is based on a design of the same name by John Williams as [...]]]>

Now that’s what you call an engine !

If Crocodile Dundee built an engine he’d build a Bonza which is exactly what my friend Aussie Jim has done. This is Jim’s first large engine and it’s an absolute beaut !

It is based on a design of the same name by John Williams as published in Australian Model Engineering Sep 2009 – Aug 2010. Changes, in addition to a few cosmetic ones, include the use of an RCEXL CD ignition and substitution of Jan Ridders’ Vapour Carburettor for the original.

As Jim explains – It is called a “Hit & Miss” engine because of the way its speed is controlled. When the speed rises too high, the governor holds the exhaust valve open so it does not fire (a “miss”). When the speed drops again, the valve is released so the engine fires (a “hit”).

Jim has kindly put together some notes and photographs taken during his build.

Remember – if you want to see a larger pic just click on the image.

Create your own shape and choose the colour for your LED and make one or two for your friends

There are two famous people in Wales and they both play billiards. The first is a chap called Terry something-or-other and he is [...]]]>

Polish up your turning skills with this novel brass torch

Create your own shape and choose the colour for your LED and make one or two for your friends

There are two famous people in Wales and they both play billiards. The first is a chap called Terry something-or-other and he is renowned for his ability to send even the most ardent insomniac into a deep and blissful sleep on a Sunday afternoon.

The other chap is called Ralph. He’s also known as ‘Divided Head’ – I am not too sure why but I suspect it may have something to do with an incident involving an up and over garage door.

Recently Ralph caused outrage amongst certain old school model engineers when he revealed his lathe mounted mop polisher.

Any road up Ralph has unselfishly agreed to disclose his method of making little brass torches. I am ignoring the fact that my local petrol station is currently offering an impressive looking multi bulb LED torch for a mere £2.50. Ralph’s torches are truly little gems and make lovely gifts for family and friends. Not only that but they are fun to make and provide an opportunity to hone your turning skills and demonstrate your creative talents.

So, without further ado lets get the boys on the baize.

Ralph has produced this excellent series of 4 videos with step by step build notes to guide you through the construction but before you sit back and enjoy here is a cut away sketch showing the various components.

A cut away sketch showing the components and assembly

Video 1

1/ Cut length of 1/2″ hex or 9/16″ round brass bar to be finished to 25mm length. Round bar at 1/2″ will show thread cut on outside and can be hard to get rid of. That’s if it doesn’t tear through the side ! 9/16″ bar allows a quick lateral turning with the cap blank screwed tight so it mates perfectly.(before the cap is cut and shaped!) Hex shows thread slightly but a light draw filing or lapping sorts this.

2/Face off both ends.
3/Centre drill.
4/Using 5mm drill, drill through bar.(assuming you have purchased 5mm blue, red, white or green LED?… else a 3mm or 8mm led could be used, depending on power requirements?)

5/Using 10.5mm drill (prepared for brass if possible.) make a 16mm deep hole for the innards of the torch. Tap the body with a M12x1.5 thread (I always bottom the tap out.)
Cut a recess for the O ring (see video/Crap-O-cad) Just removing the thread should give sufficient space for the main O ring to sit. ( Run the tap back through to chase/clean up thread. remove thread burrs.)

6/ Remove the main body and place to one side. take another length of bar at least long enough to get a parting tool into once it has been cross drilled….see video1. Turn down to 12mm dia and at least 9mm length.

7/Cut M12x1.5 thread onto remaining turned section.

8/Using parting tool cut recess into turned section at base. (approx 1-1.5mm deep depending on the ‘O’ ring you have selected for the seal)

(you could do parts 7 and 8 in reverse order … It wouldn’t alter the outcome)

9/Test fit main body. If a hex bar is used and you want it to line up perfectly then a bit of fine skimming work on the main body length will probably be needed (unless you’re lucky)
(The pattern is usually a little off when fully tight, a bit of draw filing or flatting of each of the sides once the torch is completed will true up the pattern enough to fool most eyes.
If your not too fussed… Like in the video, then leave it!
The torch when off will be where you set it… lined up if you want it that way, and when it’s on it’ll be where ever it is…. Up to you what you want it to finish like.

Video 2

10/ Cut a length of thin plastic (packaging like you get paint brushes/batteries etc in is good for this, thin but stiff when cut into a strip. Thickness of plastic must be assessed as slight thickness variations could prevent the batteries from being easily inserted and removed !
I pull the plastic hard over a thin round bar, causing it to curve and hold that shape. Trim the plastic to length and depth.
Depth of plastic shown is in drawing. It is the height of the two cells stacked. It has to prevent the outer body of the battery/cells from touching the inner of the torch body. Insert the plastic when ready, check for overlap or not enough coverage.
Trim small slices until you get it just touching when fitted.

11/ Check LED polarity, easy way, touch the leads onto the poles of one of the cells (if you’re using the 3V ones specified) alternatively you could use a meter or search for data on the web to identify the Cathode and Anode.

12/ Cut a disc of plastic rod 1.5-2mm thick 10.3mm dia and drill a 1mm hole 2mm off centre for the LED negative leg. The negative leg is then passed through the hole and cut to allow 3-4mm to protrude. This is then folded across the centre of the disc. (see video)

13/ Bend the positive leg flat horizontally to the opposite side of the disc. Bend the leg up around the edge of the disc (keeping it tight to the disc) Cut the leg to length, level with the top of the disc (any higher and it might short circuit the cells!…. See video)

14/ Insert the completed LED assembly into the main body of the torch and push the led home. This may need a bit of a shove…. Try not to damage the LED or it’s legs!

15/Insert the insulator strip.

16/ Insert 2x cr927 lithium cell battery’s negative end first and keeping the torch pointing downwards screw the threaded section into the body till the LED illuminates..

17/ The LED will illuminate before the cap is all the way home. Check with a vernier or similar, the gap left between the cap and body sections.
(This is all done because there are always variables, from slightly less or greater depths when drilling to LED legs and exact insulator disc depths….. This is a very adjustable design)

Video 3
18/ Re-chuck the tail cap blank and remove all but 0.2mm of the length measured. Turn down the threaded section to allow a 8mm dia and 1-2mm deep stub to be formed.

19/ At his point remove the work from the lathe and fit it as per 16 and 17, remove just enough for the light to turn on as the cap and body edges meet. Remove with VERY fine cuts (even emery) the amount needed to get the light to turn on just as the cap and body edges meet.

20/ Dependant on your O ring size make the recess Using a parting tool or 1-1.5mm thick tool (specially made for another job?). Cut a recess into the face of the cap (see video) wide enough to take your O ring and deep enough to allow it to stand a hairs width over the centre stub.

21/Once satisfied that the O ring is to the correct height. Glue it into position, superglue is ideal.

22/Cross drill a hole through the bar, approx 8mm from the mating face of the tail cap (thread end) this is for the split ring. (I use 2.5mm see video/drawing)

23/Part off the cap, (or hack saw) allowing for the correct length to be achieved when making the eye on the cap (I allow 4mm over the top of the cross drilled hole).

24/Screw the tail cap on to the main body and using the body as an arbour to hold the cap in the lathe. Turn it down to a shape of your liking. (See video, freehand shaping is your own and original every time !) Use a small bar in the split ring hole to undo it after this process, it will have tightened.

Video 4
25/ Turn the torch around and turn your desired concave dish design (being careful not to hit the led!… you could remove all the inners if you wish) You could have the LED protruding? Just be careful not to remove so much material that the LED sticks out and could become scuffed easily, a little scratching effects the light output greatly!
I styled some with stepped cuts and rings. But I am sure your own design desires will lead you to a finish of your choice.

26/ At this point I draw file or flat the hex body. (see video) I gave a nice turned finish on the round ones and polished some of them to remove imperfections.

27/ Add a split ring, brass coated ones can be purchased very cheaply from a key cutters/hardware store. Takes some doing not to scratch the cap when fitting the split rings though! (I use a round pointed barto open the ring to 4mm and then to hold the ring open as I pass the ring through the cap. Then transfer it to the end as it comes around so that it doesn’t scratch as it snaps shut.) Once the ring is on it’s pretty easy to turn on and off…. Might require a smear of petroleum jelly?

Little cheats….

If the grip between the body and main O ring on the cap is weak when turned off ( Off – should be no more than one flat, or on the round torches less than a ¼ turn anti clockwise) and it needs to be tighter to prevent the parts from separating.
Then you can cheat with a very narrow strip of black insulation tape under the main O ring.
It must be exact length. An overlap will alter the depth considerably.
They MUST be slightly stiff to turn, as this stops you losing the body of the torch off the cap as it rattles around on your keys or in your pocket.

If you take too much off the tail cap and it doesn’t reach the cells.(when screwed in to make the ON contact.)
You can re-make the LED disc/insulator a bit thicker…. This will raise the LED leg (be careful not to damage the legs removing and re-bending them) and raise the batteries…. Be sure to check that the insulator sleeve depth, it should be fine. But check it all the same.
(you can make the discs in small increments till you get one that’s right if need be)

Parts list:

Brass bar – 13mm or ½” hexagonal for the torch shown in the video or 14mm or 9 1/6″ round. Minimum length required 50mm (25mm body and then the cap from the off cut….. I try to use as longer bar as possible to make the cap on though for safety and ease of machining)

LEDs available in a range of colours and 3,5 and 8mm sizes

LED – 5mm very high brightness type …. 32000mcd for white….(clear focused casing)
There are many, many types of LED, colours and intensities…. From past experience always go for clear narrow focus, 15degrees or there abouts works well for most applications and as for the mcd rating…. The higher the brighter is the way it’s supposed to go But it’s a mine field if you go looking for the best for the buck!
You shouldn’t pay more than a couple of quid for 5-10 posted from China/Hong Kong via e- blag….. I certainly wouldn’t get ‘em from the high street retailers here in the UK…. Rip off!
Rubber O ring – to fit collar of cap 10mm internal 1.2mm dia material (you can alter dimensions of cut to suit your O ring.

Rubber O ring – to fit contact point of cap 3-4mm internal 1.2mm dia material
(Again O rings can be found to fit your cuts and cuts made to fit your O rings )

Nylon or equivalent impact resistant plastic bar @10.3mm min’ dia’.

Thin stiff plastic strip to be cut to size (depth of 2 cells and enough length to seal outer wall of torch from cells.)

½” Brass coloured split ring