Well today I managed to get back out to the workshop for a couple of hours. Since the cylinder liners have now been made it was time to start on the other cylinder fittings, namely the 16 valve liners (yes I am building 2 engines).
Having looked at the plans several times and referred to Edgar T Westbury's article published in Model Engineer (April 1947!) it seemed to me that since the guide must have the valve bore exactly central and to size, it would be better to use the 4 jaw chuck to make them.
I then considered the machining process to make the valve guides and due to their shape the best way forward would be to produce phosphor bronze blanks. These would then be inserted into a special collet (yet to be made) which would allow me to produce all the blanks in one go (see photo of the first trial blank).
The blanks could then be inserted into the collet, which would be set to run true in the 4 jaw chuck. Then the very small 3/32nd” central hole can be drilled and reamed before finally boring the ¼” diameter inset which needs a special HSS tool ground to shape, allowing the bottom radius to be turned.
Whether this is the best way to make the valve guides I am not sure, and if you know a better way then let me know before I start the job in earnest. Edgar’s article is very skimpy on making the valve guides and this worries me in case there is an easier way to proceed.......A second question arises in my mind in relation to Edgar’s design. Again I will have to do further research since I cannot see why he would have produced the guide with such a small diameter bottom end. It is only 5/32” in diameter and the valve stem is 3/32” in diameter. Making it larger would have the benefit of allowing a larger diameter valve stem, although that may have an influence on the inlet and exhaust volumes......
I may have missed a very good reason for his design being so, so I decided to put further work to one side on the valve guides until I know more and push ahead instead with the 2 flywheels.
- Turning the phosphor bronze valve guide blank
Valve guide on the Block casting
About Mike Freeman
Hello, my name is Mike Freeman and I am a retired Chief Fire Officer from the United Kingdom with a keen interest in model engineering, silver caddy spoons and sea fishing. I live in the pretty fishing port of Brixham, South Devon, in the United Kingdom.
I am a sufferer of degenerative osteoarthritis, which impacts on the amount of time I can spend in the workshop, and is the reason why you will see seats and a stool in some of the photo's. I have only recently added the above sentence after a discussion with one of my Doctor's from the excellent pain clinic, based in Torbay. This does affect concentration one of the reasons why I double then re-double my measurements and set ups.
Before completing nearly 30 years of public service I and my wife Sandy, owned and ran, a small restaurant in Okehampton Devon. Prior to marriage I worked for my father in his various businesses, in the early days these were garages, which he bought in a run down state, then built them up before moving on, to start again.
I took every opportunity in those early days, to work in his workshop's
learning 'on the job' rather than as an apprentice. This, I suspect, is the reason why my building various model's in the early days, turned into model engineering, when funds allowed the required equipment to be bought.
My workshop comprises one half of a detached double garage. It has a
stud wall separating the two halves and unusually perhaps, its own
shower/toilet/washbasin compartment! (the true reason for buying the
bungalow - don't tell the wife!!!)
It is fully insulated with a ceiling and fluorescent lighting supplementing the one window. Several double electrical sockets are dotted around in
relevant positions.
Equipment consists of 2 lathes (1 Myford ML 10 and 1 Chinese variable
speed motor with etched glass DRO's), 1 milling machine (RF25 far East) floor standing pillar drill, Proxxon bandsaw, Warco bandsaw, 6" wire brush and polishing mop motor, 6" coarse and fine grinder, Proxxon mini drill, various benches and an engineers vice. I have just acquired a third lathe, a Myford ML7 which I am at present evaluating so I can decide which of the Myford's I will keep.
I have only just bought the Chinese lathe and had it fitted with DRO's prior to delivery. And what a bonus they are! So good in fact that I decided to buy another set for the Milling machine. Whilst my engineering experience can only be described as limited, I find the use of DRO's has affected my accuracy levels which have improved tremendously (although that's not saying much!) and would recommend their fitting to any model engineer.
Prior to retirement I built for my son's 17th birthday a Locost car. This
was a tremendous project and a great feeling when it passed its test. The book it was based on suggests it can be built for £250. Ours was nothing special in the sense of all new parts but still cost about £900 to build!
After studying the plans last night I found the answer to my own question regarding the diameter of the lower part of the valve guide. The reason it is so small is because of the need for the valve spring to fit over the small end.
Problem solved so I now need to get on with making 16!