Start Model Engineering

Opus Proximum - a vertical engine by Stan Bray published in a special issue ‘The Best of  Model Engineer’.

Fellow model engineer and regular visitor to my site Malcolm Tompkins was attracted to this vertical engine as his next project. The plans and build notes are published in ‘The Best of Model Engineer’ an Autumn 2009 special. Copies should still be available from W H Smith. The plans show construction in both metric and imperial measurements but don’t try to mix them - they won’t work !

Having decided that a vertical engine would also be a welcome addition to my line up of model engines I felt that upping the size by 50% would produce a more impressive result. At the same time both  Malcolm and I  felt that metric was the way to go with easier calculations and a better choice of fasteners.

The plans were enlarged to fit on A3 sheets. All the original dimensions were tipexed out and the new metric  dimensions, upped by 50%, were inserted and final A3 copies run off. I would hasten to point out that both Malcolm and I bought a copy of the magazine so there was no distribution of freebies !

A study of the article and plans did throw up one or two teasers. The most obvious being the photograph on page 29 which showed a completely different arrangement of the main bearings, crankshaft and connecting rod. I came to the conclusion that this was an error and will therefore be ignored in our build.  I also came across one or two other anomalies. For example the instructions on positioning holes for the cylinder (2) PCD - should have read (12). Similarly the valve chest was given as 16mm wide yet the cover was given as 15mm. Care is therefore required as we machine each piece to ensure that it corresponds with related components.

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

Machine cylinder and top cover ensuring alignment of bolt holes without the need for digital readout facility on rotary table. Note dimensions are for engine increased by 50% from plan.

The bolt circle programme referred to in the captioned photographs does require digital read out capability on ‘X’ and ‘Y’ axis. There is an alternative method of tackling the cylinder and cover best illustrated with this sketch and notes

1.     Square up a 50mm length of brass to 24mm square.

2.     Bob it in your lathe’s self centering 4 jaw chuck, face both ends then turn the first 5mm down to 24mm dia.

3.     Machine locating lip to 1.5mm deep.

4.     Transfer to R.T. spot the position of each of the eight bolt holes and drill 2mm to depth of 8mm.

5.     Transfer back to lathe, centre drill the 3mm piston rod hole and part off the cylinder head cover. This will now be aprox 3mm deep including lip. (f your parting cutter is wider than 2mm then increase the 5mm turning in point 2 as necessary.

6.     You may need to skim the top of your cylinder cover later on your mill to clean up and bring to required overall depth.

7.     Similarly I should take a fine facing cut off the top of the cylinder so everything is nice and square.

8.     You can now drill and bore your cylinder to 15mm (or a whisper under the size of your most appropriate reamer).

9.     Return back to R.T. and machine away two corners until the desired shape has been achieved.

Email me if you require further information or assistance with this procedure  john@start-model-engineering.co.uk

Moving on to the shaping of the cylinder. This was done utilising the rotary table on my milling machine. It would be possible to form the shape by careful hand filing or, alternatively, leaving the cylinder in its square shape.

The project was brought to a halt at this stage for adjustment of the dimensions on the plan.

Updated Friday 13th November

undaunted Stan Bray’s engine project continues

After having given the plans a good looking at I decided to proceed, amending the depth of the steam chest from 18mm down to 11mm (to be on the safe side increase to 12mm) which provides sufficient clearance for the valve movement.

One feature of particular concern was the process of making and attaching the two lugs either side of the cylinder, required to support the slide columns.  To improve the accuracy of fitting I machined a pin on each lug and a corresponding location hole on each side of the cylinder. This modification eased the process of accurately silver soldering the lugs into position.

“to err is human……”

Having completed the cylinder, steam chest and valve the good news is that I am happy that they will perform their function. However, the downside is that visually the alignment between cylinder and steam chest is not good. Attempts to correct have not really been successful and to rectify would involve several days work.

The next stage was to sort out the motion plate by machining the top mounting lugs for the cross head slide bars. The hole centres on the cylinder lugs are 30mm apart so this dimension is repeated for the top slide bar positions.

TLC   (in model engineering terms this means - take light cuts)

Now there should be a batch of photographs showing some detail work on the motion plate (milling slide bar lugs), soldering the base of the cylinder into position, etc. ( following my experience I urge you NOT to solder and go for a good snug press fit bonded with a thin covering of Loctite). Anyway as a result of a flat battery camera I didn’t get any pics but it was all relatively straightforward so you should have few problems (yes I know, famous last words !).

Today, with my battery recharged, my attention turned to making the eccentric strap. A tricky piece of machining on both the mill and the lathe. The secret, like most model engineering activities, is take your time and take light cuts - oh and measure a lot, then measure again.

The next stage was to sort out the motion plate by machining the top mounting lugs for the cross head slide bars. The hole centres on the cylinder lugs are 30mm apart so this dimension is repeated for the top slide bar positions.

We now get to the stage where there are a number of detail jobs to be completed. I confess to not having taken many photographs but if you have successfully reached this stage with your build then I don’t anticipate that you will have much problem in the finishing stages. However, should you require any guidance I am only an email away and more than happy to give you the benefit of my (limited) experience.

Apart from some cosmetic detail Opus P. is now completed but steadfastly refuses to show any signs of life. Examinations will continue but my suspicions lie with the porting arrangements.

I am concious of the fact that a number of people have been following the build of Stan Bray’s Opus Proximum and that they may be wondering why this thread has ground to a halt.

The truth of the matter is that so far, despite, my best efforts, Opus refuses to run. Not only will it not run there is absolutely no sign of life. My suspicions focus on the inlet and exit porting arrangements and I need to carry out some visual comparison tests against similar valve arrangements on one or two of my Elmer engines. Even before I attempted to put some air through my Opus P. the opening and closing of ports didn’t seem to be quite right. When air was connected up it appeared to run straight through and out of the exhaust regardless of the stage in the cycle. There is a slight change in note as the valve moves in the chest but there is clearly something basic that is not right.

As readers will know I did discover a number of anomalies with the plans for Opus P. and I am beginning to wonder if this string of errors includes the critical porting arrangement.
It may be a few days before I am able to continue further examination if meanwhile any readers have any thoughts or ideas I would be very interested to hear from you. Indeed I would be interested to hear from anyone building the Opus P. and to hear of their experiences.

My eZee Liv electric bike which provides me with almost effortless cycling and gives me an enjoyable break from the many hours couped up in my workshop

I think most will agree that model engineering is an ideal pastime for the mechanically minded during their retirement years.

To my mind though there is a real danger that you can become so absorbed in your hobby that you spend all your available time hidden away in the workshop. In my case my workshop is the domestic garage with hardly any natural light from which I ocassionally emerge blinking like a mole.

During the warmer days (remember those ?) I started to give myself  ‘days off’ so I could get outside and enjoy a break from whatever project was dominating my waking and sometimes, sleeping, hours.

I reluctantly packed in my passion for motorcycling a few years ago and in its place discovered the world of electric bikes.

Electric bikes are power assisted cycles using low voltage motors normally fitted unobstrusively into the front or rear hub and powered by specially developed high capacity rechargeable batteries. This takes much of the hard work out of pedal cycling, increasing enjoyment yet retaining the freedom of a conventional bike.  A good electric bike takes much of  the pain out of climbing hills and provided you put in a reasonable amount of effort you can climb hills of 1 in 10.

Further good news is that there are very few restrictions. Maximum allowable speed is 15 mph under British Law and riders must be at least 14 years old.  Apart from that you are as free as a conventional cyclist. You can legally use designated cycle lanes and the increasing network of cycle tracks that are sprouting up around the country.  I often pop into my local market town of Wetherby, a round trip of about 10 miles, most of which is along an old converted railway track. I have even been known to travel as far as York and back a round trip of 30 plus miles and no parking problems when I get there.

The gentle cycling is good exercise and the fresh air and sunshine is a good antidote to those prolonged sessions in the workshops.

If anyone is interested in learning more I would suggest you take a look at OnBike - electric bike specialists. An excellent range of the latest bikes backed up by an enthusiastic team of e-bike specialists.

Here’s how OnBike summarise the benefits of e-biking…….

Economy

Electric bicycles are incredibly frugal compared with motorbikes and cars.

On average, they cost less than 2p to recharge which is the equivalent of 1000mpg (20 times the mpg of a small car)

They are treated just like ordinary bicycles for legislative purposes so there’s no need to worry about Log Books, MOT, Road Tax, Insurance etc.

Most of the working non electrical parts are standard cycle parts so day to day servicing like tire or brake replacement will seem very cheap for people used to paying for car repairs.

Health and Hills

It is said that a conventional bike will keep you fitter. That, of course, depends how much, if at all, it is being used. Because riding an electric bike is such a pleasure even in hilly country, or into the wind, their owners tend to ride them much more often than conventional bikes. The motor provides up to half the effort, but regular use means more exercise for the rider.

If you want some strenuous exercise you can always switch the motor to a lower assistance ratio or turn it off completely.

Fun

They are incredibly good fun. If you have never ridden one before you will find you get all the pleasure and fresh air of a bicycle, without the hard work, and all the excitement of a moped or a scooter, without the fumes, mechanical complexity, noise and cost.

First time riders invariably come back with a big smile on their face and many have commented “It’s like riding a normal bike only with a big friendly hand giving you a push on the difficult bits”.

Perspiration may not be a serious issue when out for a leisurely ride, but it’s more important when cycling to work. An electric bike eliminates the problem and allows riders to wear their normal clothing and really enjoy the journey.

If you are or have been a regular cyclist but are beginning to find it a bit too much like hard work then you really must try an electric bike. Suddenly those trips that seemed a bit too long will have halved in distance and those hills that were a bit too steep will have miraculously flattened.

Green

Using an electric bike is the best way there is to break the car habit. The average car journey in Britain is 5 to 8 miles and every day people in Britain make millions of small journeys to work or the shops and back that could easily be non-polluting bike rides - during rush-hour, a bike is twice as fast as a car - great if you hate jams!

An electric bike is completely emission free can be made genuinely sustainable by purchasing electricity from a ‘green’ supplier, or generating it via a roof-mounted windmill or solar panel. This will enable the vehicles’ fossil fuel consumption to be zero.

OnBike