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Bonza

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.

: Top bloke Aussie Jim, builder of this magnificent ‘Bonza’ hit and miss engine.

: Carbide tipped circular saw is fine for cutting aluminium

: Another carbide tipped blade used in a slitting saw arbor to cut out the frames

: Cutting out the main bearing mounting slots

: Frames on box base (later discarded)

: Cam bearing and cam follower

: Crankshaft ready for silver soldering

: Blocking out the conrod with a profiling tool

: Nearly completed cylinder

: Drilling the mounting holes in the cylinder

: Drilling the piston for the gudgeon pin

: Turning the ring grooves in the piston

: The govenor arm being milled from bar stock

: The flywheels were cut from the solid

: There is still a lot of machining from here to the finished flywheels

: Power-hacksaw makes short work of cutting a blank for the cylinder head

: Cylinder head set up for machining the spark plug hole

: A stainless button silver soldered to a silver steel stem makes a good valve

: The engine starts to take shape

: Cutting the hole for the hopper in the water jacket

: Baking the high temperature engine enamel in the barbecue

: The assembled water jacket fits neatly onto the cylinder

: Brass oil cups for the main bearings

: Rounding the edges of the new base plate with a carbide router bit

: Make it first draw it later. The changes mounting arrangements

: Underside showing the CDI and battery box.

: Brass tube contains the wiring to the Hall Effect device for the CDI

: Govenor side of the engine. Note the window in the Vapour Carburretor.

: Timing side of the completed engine

13 amp wobbler

Barrie Leete a staunch advocate of Compassion UK seen here during a recent visit to Uganda.

Now for something completely different !

Take a 13 amp (UK style) plug and a toilet seat and build yourself a nice little wobbler steam engine. This is what steam engine enthusiast and gadget man Barrie Leete did and finished up with a neat little single action oscillating ‘wobbler’ engine. Barrie came across the plans on John-Tom’s website.

Flushed with success here’s a step by step account in words and photographs from the man himself.

Here is my13 amp plug stationary steam engine. The wooden base is made from a wooden toilet seat. The pillar which holds the cylinder is made from the earth pin of an old 15 amp plug. The cylinder, valve assembly and the crank suppoort are pins from the 13 amp plug. The crank itself is what held the fuse clip.The piston rod and crank pin are made from 3mm stainless steel. The trickiest part of the build was the boring of the cylinder. I overcame the problem by making up a collett that would hold the plug pin perfectly central in my three jaw chuck. Well, that’s about it. What will my next project be ?

There must be plenty more engine bases left in that toilet seat Barrie ! (ed)

: View of completed engine from flywheel side.

: A view of the negative pin cylinder.

: Completed cylinder and steam feed assembly.

: Completed cylinder. It bored true but is not yet cleaned up.

: I made a collet to enable me to bore the cylinder in the three jaw lathe chuck.

: Close up of cylinder and collett in the three jaw chuck.

: Disaster ! Tried to bore the cylinder on the lathe but ran out of line.

: Earth pin showing the steam inlet and exhaust ports.

: Just as I said, the loo seat will make a nice base.

: Live pin before machining.

: I made a collet to enable me to bore the cylinder in the three jaw chuck.

: Cylinder in mini lathe ready for boring.

: This the negative pin, possibly the most difficult. The small 1mm hole is the steam port which will go into the top of the cylinder.

: New pin to be made into the cylinder.

: Part assembly showing the oscilating cylinder mounted on the base and steam feed assembly.

: Pillar mounted on base. It is made from an old 15 amp plug earth pin.

: Roughly assembled just about ready for a test.

: Side view of earth pin showing inlet side port which will have a brass tube fitted.

: Some of the parts. The flywheel ia an old 1oz. weight given to me from freecycle.

: Nearly a job done as I get to the bottom of things even if feeling a little flushed.

: View of finished engine from the cylinder end.

Argus Oscillator

The Argus double acting oscillating steam angine, a first project for newcomer to model engineering by Australian Pete Harding from Western Perth. Pete explains that there is still a little finishing and a base to make but it sure is looking good.

Australian, Peter Harding of West Perth, has been a regular visitor to this site for some time and has recently completed his first build – The Argus double acting oscillating engine designed by Edgar T Westbury. The plans are featured in The Best of Model Engineer, Volume 1 along with comprehensive built notes.

Pete showed great ingenuity in modifying his third attempt at making the cylinder rather than starting all over. Errors can happen all the time, even with experienced model engineers and it’s how we deal with them and the final result that really matters.

Anyway, here is the email Peter sent me recently

Having left a comment on the Opus P page a while ago you asked if I would send a picture of the Oscillator when finished. Please find attached.

As I stated in the comment this is my first project on my first lathe – last used one at high school a long time ago! The build has, needless to say, not been without error, but highly satisfying. I stuffed one cylinder up on trying to mill a flat for the valve plate – they sure fly well – and another on my first attempt of Silver Soldering. This engine uses the third cylinder made. Interestingly I reckon it took around 30 hours for the first cylinder and 3 hours for the third!

The only major mistake still left on the engine is the additional 1/16″ valve plate at the back of the 1/8″ one. I had already silver soldered the cylinder and valve plate together and it was only on final assembly that I realized that something was wrong – I could just see the edges of the inlet and exhaust holes when the cylinder was vertical. I had mis-read the plan and made the valve plate 3/8″ wide instead of 5/8″ ! Luckily there was just enough length in the crank pin to allow the adding of the 1/16th plate of the correct width without having to make a forth cylinder.

I still have some final polishing to do and final mounting on a plinth but thought you would like an early report. Please feel free to post with comments about errors – that how we learn.

How is the Opus P going by the way – are you getting closer to having it working. Once I have tidied my shed up a bit I will be starting the Suum Cuique, hopefully with less hassles than you’ve had with Opus P.

Peter Harding

Visitor’s mini-torch

Ken opted for the acrylic version of the mini-torch. One for his wife and one for himself.

A shining light from Wales

Regular site visitor and newcomer to model engineering Ken from North Wales has sent me this pic of two recently completed acrylic torches. By coincidence the designer of these novel and useful torches Ralph (aka Divided Head) also resides in this neck of the woods. Probably something to do with those long dark winters !

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