Member postings for Jim Cahill

I can offer access to very good workshop facilities in return for assistance on a number of ongoing non commercial projects. (Based on a farm in Ireland.)

The tutorial example with the hole through the centre of the Earth seems to have caused some comment. The simplistic analysis results in a harmonic oscillation of a body which is dropped into a hole through the Earth's axis of rotation.

All sorts of things are ignored, probably because it can only ever be a thought experiment. The analysis uses energy considerations and examines the Potential and Kinetic energies of the object at the surface and compares those to the Potential and Kinetic energies at the centre.

The simplistic Energy analysis leads to the conclusion that the object will oscillate from end to end of the hole.

A competent A Level Physics pupil should find it fairly straightforward to demonstrate that the motion most certainly cannot be Simple Harmonic. Having carried out that analysis it can also be shown that the “University approved solution” could scarcely have been further from reality.

I was fully aware that going underground used the Mass above to balance the attraction of the remaining mass of the Earth. I had only been considering above earth weightlessness, and should have restricted my comments accordingly.

As I recall, there were about 50 of us in that Physics year when the tutorial question was posed. We all bought into the argument and accepted the conclusion. We would not have been the first, or only group of students to be presented with that tutorial problem. The fact that the solution persisted is a fine example of the propagation of ignorance by Academia. I certainly walked right into it. Mea Culpa!

Thanks for these.

Time is like money. - It's difficult to find enough of it.

Space is what gets filled with junk. It is difficult to locate, especially if one is carrying something heavy.

The Chicago Museum is indeed excellent. The example quoted illustrates why Mathematics, and careful, repeatable experiments, form the foundation of Physics and Engineering.

The Researchgate articecle is cut down. The complete book is available from Open Library part of the Internet Archive, and also on our own website swarfology.com.

The book introduction summarises the issue. Einstein used the example of a person in a lift to illustrate that one does not feel constant velocity, but feels acceleration. I am sure Einstein was well aware of the limits of his example. Unfortunately not everyone who studied his little book on Relativity was able to appreciate those limitations.

Designers of flight simulators are well aware that the human body is most sensitive to changes in acceleration and is not so sensitive to steady acceleration. That is why simulators use jerky movements accompanied by visual cues to fool the passenger. The rams are allowed to relax slowly, which requires slight accelerations to which the passenger is insensitive.

We feel acceleration through our feet or other part of the body which is in contact with the applied force. Gravity acts throughout the body. Therein lies the distinction which the book hopes to illustrate.

You're right Could this be a sign?

In between abusing pieces of steel and other materials I digressed into writing this book which is available free of charge in pdf form.

I have been communicating with a university student in the Cardiff area who would has no experience of mechanical engineering but would like to know more about it. I have been in touch with the Cardiff MES and they have been very helpful.

However, I wondered if there was anyone in the Cardiff area who would be prepared to meet this student and give a personal introduction to the methods employed in toolmaking and model engineering. If things work out the student would effectively become a kind of apprentice.

Jim Cahill

I just noticed there is a Raglan 5" for sale. I has a variator for speed control. I can thoroughly recommend the Raglan. You should be quids in if you sell your Myford.

I had a Trileva ML7 many years ago and found the attachment a complete nuisance. I took two of the belts off and fitted an electronic speed control. I used the one active lever as a clutch. Thereafter it was a super lathe within its limitations. To this day I have never figured out why the previous owner hadn't put the cost of the trileva attachment towards a Super 7 instead.

Hello Sean,

In one of his books, Geo. H. Thomas goes to some length to explain why he believes 4 flute cutters (Known as End Mills in the UK) are inclined to break as they emerge from cutting a channel.

Headroom is always a problem. I have the luxury of a good sized horizontal mill as well as the Astra, but even there I have sometimes turned the vertical head on its side with the job mounted vertically in order to have enough space. One of the good features of the Cincinnati is that it has controls at the side as well as at the front. That allows me to take the head off altogether and mount the tool directly in the horizontal arbor. This latter arrangement provides more power to the cutter, increases rigidity, and allows me to watch progress. I have done the same thing with the Astra, but watching the cut is not so easy.

Thanks for the info C.J.

The speed control is really a necessity for horizontal milling of steel. I recently finished fitting a triple pulley set to the Astra. It was from a cheap pillar drill. The previous owner of my machine had fitted a washing machine motor with a home made basic variable speed capability. The motor did not produce sufficient torque with the pulley arrangement he had. The additional reduction and choice of ranges provided by the new pulley set has made a world of difference. I can now actually remove metal with the Astra.

I was using the Astra before lunch for drilling some holes in a Quorn component. I had overlooked the holes prior to assembly which made the job a bit tight, but I got away with it.

Jim

Moore's "Law" may have held because it is not in the Interests of the computer industry to run too fast.

When Mobile phones first came out, Motorola Gurus predicted phenomenal demand and built 3 factories in Scotland to meet the projected demand. The factories were expected to work 3 shifts. Only one factory was ever used and peaked at 2 shifts.

People accept change slowly and eventually grow tired of continual upgrading.

Hello Thor,

Thanks for the links. Neil F's page is informative. His is a later model than mine, but the drive arrangements are likely to be similar.

All the best.

Jim Cahill

I have an Astra L4 Milling machine. The previous owner fitted a variable speed motor because the original drive arrangement was apparently unserviceable and incomplete. I would like to get my hands on a photograph or technical manual showing the original arrangement.

Hello Alfie,

Welcome to the forum. I'm fairly new to it myself. Unlike you I don't have a lot of time to spend browsing. Anywa y, the Internet service is poor in this area. I know what a bad back is, but I was lucky and was introduced to a chiropractor, so it's pretty much history now. We have a farm in Ireland which is hard work any way you look at it. Maybe we should talk. my website is heronmeadows.com.

All the best

Jim Cahill

Hello Harry,

If the budget drill press served your needs for a reasonable time, perhaps another similar one will serve too. If the play is in the spindle itself, it might just need new bearings or bushes.

If the play is in the body, you might like to machine the body itself and make an insert. All good fun things to be doing while looking for a new one.

Jim Cahill

heronmeadows.com

My sons learned to use machine tools etc when they were very young. When they were old enough to look for an apprenticeship they went for a couple of interviews. They didn't want to be servants to the clean automated boxed in CNC production units they were shown. So they set up on their own and have done very well for themselves so far. They have variety in their work, they travel around, they set their own prices. They have control.

Why should anyone want to enslave themselves to the production world? There are still some excellent opportunities as technicians in the University Sector, and I wish I had been able to spend my life in that world. The pay is not the best, but the flexibility and creative opportunity can be tremendous.

If manufacturers want creative people, they ought to provide a creative environment. I'm sure some of them do that already, but I imagine they will remain few while accountants rule the world.

I have offered the opportunity of student placements many times, but so far nobody has shown interest in a voluntary position.

Horses and water.

In my experience, a good second hand industrial quality machine will always give greater satisfaction than a new machine aimed at the amateur market. Three phase is no longer an issue with inverters readily available.

Most of all, don't be fooled by "Features". Quality machines let the user produce good work without grief.

But then, I'm a dinosaur.

Jim