Member postings for Martin Kyte

I to admit to only looking up the MS58. Depends a bit what you want it for. If it’s clock plates then you can always bush the pivot holes and run the barrel in ball races if you want better bearing surfaces. The only snag I could see is they state that the plates may need some finishing which suggests that the surface is not exactly mirror like.

regards Martin

The spec says it has similar composition to CZ120 and is a free cutting leaded brass. I would have no qualms about using it for clock plates or wheels.

regards Martin

Ah the old nature of reality question. Who knows what anything is ‘really’. All we have is what our senses and sensors tell us. Back to Plato and the cave. We get a little further with instrumentation in as far as building spectrometers allows us to agree what we mean by Yellow for example but still we cannot be sure that what I ‘see’ as yellow is the same as what you see. Past and Future are emergent from conscienceness but the equations don’t differentiate and can run both ways. All we can do is trust our instruments and leave the rest to the philosophers cos it ain’t physics.
regards Martin

Edited By Martin Kyte on 02/04/2023 09:31:38

Edited By Martin Kyte on 02/04/2023 09:32:43

It depends if you are trying to minimise the spring effect or use it to balance out other causes of period error.

Youngs modulus decreases with temperature so the restoring force of the suspension will also decrease with temperature. Shaped cheeks have been employed (notably by John Harrison) to create an additional control factor by shortening the effective length with increasing angular displacement and so balancing environmental changes with modified circular error.

Best if you realise and quantify at least in order of magnitude all the factors that effect the motion of the pendulum.

I have a friend who for years worked for one of the examination boards assessing the quality of the marking and adjudicating on disputes. He told me of one student when presented with a right angled triangle with two side lengths given and the other labelled x with the question find x, had drawn an arrow pointing to x with the words ‘here it is’. They awarded the marks to the student on the basis that he had answered the question which was badly written. I should have said find the value of x.

As to burr, flash and fash, these are descriptive terms and probably have been established by general use very likely with local variants although I suspect fash is a little odd. As mentioned it’s Scot’s dialect for fuss although I guess burrs can cause a lot of fuss. Not something I would worry about greatly. It’s not as if it’s the same as defining a tangent where tangent has a very specific meaning. Once the casting is fettled the flash is gone and I suspect there are a few more variations on fettled too.

regards Martin

Stop prevaricating and get on with the clock.

🙄

regards Martin

I have to admit to not noticing that you had fixed the chops I was assuming you had just made the bits. However you could make a simple punch and die set. Slot milled in a couple of bits of steel and a punch to suit with the whole thing pinned together to align. Much as you would do when punching holes in a spring steel suspension. It can be made of mild steel as it won’t get much use.

regards Martin

Punch a slot down the middle of the suspension strip. Wide is good as it’s more stable but losing a portion of the middle will reduce the spring rate and leave the chops as made.

regards Martin

Of course if you really want to get complex you could get an astrolabe.

Any thin clean oil will do. The colours develop just by heating to tempering heat and stopping at blue. The oil prevents the process from continuing by cooling the part and providing an oil film to protect the surface. The colour comes from the thin oxide layer developed on the surface when heated and is an optical phenomenon caused by interference which is why the colours change according to the thickness of the oxide layer.

Oil does however make the surface look blacker presumably by mopping up the blue photons somewhat.
regards Martin

Edited By Martin Kyte on 28/03/2023 12:33:34

Just looking at the image Dave so kindly provided if you draw a line from a corner to the midpoint of the opposite side for the three faces that should get you the angles of the 3 cuts you need. If you put a hacksaw cut down each line square to the face that would get you a saw guide. With a little inventiveness you should be able to clamp each piece of tube to the inside of the jig and trim the ends.
regards Martin

The whole thing could be done using only a straight edge with 2 marks to define the edge length, thus escaping the metric or imperial argument.

Start by making three pentagonal templates from sheet material, MDF is cheap. Assemble the structure so you have a common corner. This gives you the geometry and once you have all the tube cut to length so each piece fits on the outside of the jig you can then trim the ends so they join neatly when on the inside. If you cut the corner out you can use the jig to align the tubes for welding by placing them on the inside an tacking up.

It may be a more interesting shape to build from pentagons and hexagons. A friend and I did an observatory dome this way with fabricated panels in fibreglass.

regards Martin

**LINK**

The above link may be useful and there are references to viscosity too.

The graphs are in terms of relative humidity and temperature but I guess that’s because it’s a far easier thing to measure.
regards Martin

Hi Dave it’s absolute humidity that determines the density. Basically molecule counting. As a water molecule is less massive than an O2 or an N2. Using the ideal gas law with temperature and pressure constant for the same number of mixed molecules the density reduces. It also reduces with increasing temperature with increasing divergence at higher temperatures with different absolute humidities. Temperature variations seem to be the bigger factor in density than humidity.
regards Martin

Whilst I agree that the Government is less than generous regarding allowances and pensions in general, compared to say 50 years ago in the main pensioners are relatively comfortable regarding income. This is largely due to widespread workplace pensions in addition to state pension. Living on state pension alone is tough but fortunately there are relatively few who have to. I fear for the middle aged and younger population who don’t have the same access to reasonable pension schemes such as my age group did. (I am just shy of state pension age but in receipt of a good workplace pension) . Coupled with the clamour for people to dip into their pension pot early I fail to see how some people will cope. I am increasingly convinced that my generation has seen the best of things in pretty much all aspects of life and the next couple of generations down will and are finding things far tougher than we did or do.

regards Martin

Well if you increase the water molecule content of air it becomes less dense so buoyancy will decrease. How the viscosity changes is another question.

regards Martin

Don’t sweat it I jump to false conclusions all the time but then those who never dream up daft ideas never come up with anything new. The trick is identifying the daft idea with a spark of brilliance in it. Realising why a daft idea is daft is useful too. Viva le daft idea. (Nothing to do with Vauxhalls)

regards Martin

If the invertable pendulum has an effective length l equal to the distance between the pivots then is it not effectively identical to a pendulum of mass m at length l. Why then would you say that the centre of oscillation is at the pivot.?

Certainly the centre of mass isn’t.
Regards Martin

PS I thought the point of it was to make the measurement of l easy so as to measure local gravity.

Edited By Martin Kyte on 25/03/2023 12:46:39

Edited By Martin Kyte on 25/03/2023 12:48:52

I’m given to understand that the French railways were still setting or at least checking station clock into the 1970s. Certainly the clocks from large houses would be set by sundial in previous centuries and many longcase clocks had the equation of time mounted inside the door. Some sophisticated clocks had duel chapter rings and other mechanisms to make setting to sundial time easier.

regards Martin

It’s easy to start ‘chasing the theory’ on this one. What I mean is you think you need a perfectly massive and stable mounting for your lathe. Whilst stability is good for obvious reasons that once installed your lathe needs very little further attention to alignment and mass can help to damp out vibrations so as to limit chatter issues it can be far less important than you think. I once realised that my Super 7 had been in use for several months with the nuts on the mounting block studs loose without any loss of accuracy or performance.

The lathe bed is a fairly massive casting (OK not anything like as massive as much bigger lathes) but compared to a flimsy wooden bench the lathe is more likely to deform the bench than the other way round. Move to a very heavy steel structure and yes you can get the bench to twist the bed if it doesn’t provide neutral support to the lathe (hence the jacking screws to adjust the support for each ‘foot’.

Leaving aside the supplied cabinets from Myford which are perfectly adequate to the job the advice is to mount on a sturdy bench and I would add that mounting blocks with jacking screw adjustment is at least desirable if not downright necessary.

Obviously the bench must support the weight and further to that should be reasonably stable in as far as not changing shape too much or too quickly. Wood absorbs moisture from the air and swells or shrinks accordingly so if you make your bench of wood then a good varnish all over will limit this. Joints need to be glued as well as bolted or screwed (unless you are into mortise joints) and the intelligent use of cross braces will resist twist. A symmetrical design will ensure that any movement of one half of the bench is balanced with a similar movement from the other half. Mass may help with vibration but the lathe does most of the work in that respect.

The aim is to support the lathe without introducing any stresses into it so I would say then that a badly designed sturdy bench can be worse than a lightweight well designed bench.
To return to the OP. He says his stand is sturdy but not stable over the long term. I would suggest that an alternative to starting again with a new stand would be to address some of the issues with the existing stand. Painting to stop moisture absorption and the use of either cross bracing or sheet ply to fill the sides which have the same function and will stiffen up the structure.
I hope this helps.

regards Martin