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Member postings for John Haine

Here is a list of all the postings John Haine has made in our forums. Click on a thread name to jump to the thread.

Thread: More beginner questions
01/06/2022 22:39:23

I noticed a couple of references to EN1A and Pb - but I don't think it was made clear that this is a free machining grade of STEEL.

Thread: UC100 with printer switch for two machines
01/06/2022 09:52:24

My mill is a Novamill which is basically similar except that I only bought the mechanical bit - fortunately! Actually connecting to the mill is quite easy once you get the right connector which is available. The documentation says the pins are all crimp but you can easily solder - the pins are separate with a little solder bucket, once you solder on the wire the pin is inserted into the connector body. Of if you have the cable of course you can use that, just cut off the connector at the controller end and separate the wires. All the connections are given on the Denfordata site.

Just using modern stepper drivers but the original motors will probably improve the machine quite a lot - I think the originals didn't use microstepping for example. But on my machine the motors still have some odd resonances which I can't tune out though it doesn't affect cutting. Better drivers and new motors would probably sort that, but as 2 of the motors are hidden in the column that isn't so easy.

01/06/2022 08:48:26

My experience with the uc100 is that it is smoother than the PP but not a lot. I need to upgrade the drivers on my lathe to get the benefit of faster stepping. What drivers do you have on the mill?

In 10 years using the PP I don't think I ever noticed lost steps.

The uc100 should allow lathe threading with Mach3 but I haven't yet tried it.

31/05/2022 16:32:12

Ah, no, I'll have a play. It's only an inconvenience really as I do the design work in my office and generate the g-code file then transfer it to the workshop PC. But sometimes it's nice to edit things in the shop. Thanks for the suggestion.

31/05/2022 14:53:01

CamBam works great on my Huawei laptop but on the mini PC it's just slow.w.w.w....

31/05/2022 09:43:10

OP says he has a UC100 already and wants to use this.

USB switches that work as required for this application (switching one USB host port between 2 USB devices) don't seem to be available, though it wouldn't be hard to make one. Unfortunately all UC100s have the same address so you can't plug 2 into 2 USB ports. That's why I ended up doing a manual changeover of the USB cables.

I found a cheap Dell Inspiron mini Win10 PC on ebay that works with my existing display and was a lot cheaper than a laptop for the workshop. Plenty of grunt for Mach3 though it struggles with CamBam.

There are a few parallel port switches on eBay for only a few squids.

30/05/2022 21:26:06

I used to work like this when using the parallel port on an xp machine so in principle it should be ok. It may depend on the drive capability of the uc100 and the cable length. I'm not sure how easy it is to get 25 way printer switches these days, by the time you've found one and the necessary cable it might be as cheap to buy another uc100. I've got one on the mill and another on the lathe, with manual changeover. It's a shame I gave away the switch and cables with the old pc but the new owner may have them spare if you want me to check?

Thread: Unusual Escapement
29/05/2022 11:03:16

**LINK**

Sorry Michael, your link got corrupted.

Edited By John Haine on 29/05/2022 11:03:54

28/05/2022 18:30:41

But we are talking about accelerations not uniform velocity. It's true that the earth is moving around the sun etc but these have negligible effects locally on something the size of the clock. In your thought experiment the suspension is oscillating above an initially stationary bob, and except when it's vertically above it it will exert a sideways force that will start it swinging. The suspension is local to the bob.

David, thanks for the confirmation! I'm planning a few days up north so will try to take in the museum. The only references to actual conical pendulum clocks I can find in HJ and the AHS journal are to ones by this French maker Farcot.

28/05/2022 12:41:11

Would it be Cliffe Hall, Keighley?

28/05/2022 12:23:52

By the way David, where is this clock, you said a "stately home", please?

28/05/2022 12:21:21
Posted by duncan webster on 27/05/2022 15:57:31:

The bob isn't stationary relative to the suspension point, it is swinging at its resonant frequency. The suspension point is moving relative to the rest of the world sinudoidally with the same amplitude but 180 degrees out of phase. Add the two together and the bob has no sideways motion relative to the rest of the world.

But "the rest of the world" - or the "fixed stars" - is what determines that the bob has mass, inertia, and momentum. If it's stationary relative to the these then when the suspension point moves it will exert a gravitational force on the bob (times the sine of the instantaneous angle) causing it to accelerate and start swinging at its resonant frequency with respect to "the rest of the world". You can make relative motions disappear by transforming to other reference frames for constant velocity but not when acceleration and gravity are concerned.

If the suspension point is a twin gimbal then the pendulum will have two resonant frequencies in orthogonal directions, rather like the "solar sidereal" clock I mentioned earlier. These will be very close together and it wouldn't be surprising if the pendulum swung in a slight ellipse as a result. I don't think this would be due to an "Foucault" effect, it's hard enough to show effects of the earth's rotation even with very long precision pendulums! But a fascinating lock - it seems to be the only example of a clock actually using a conical pendulum for timekeeping there is.

Also, at the end of the train there must be a wheel rotating at the speed of the pendulum driving the "pallet" - it's unlikely this will be dead true so there could easily be a varying drive torque every rotation. The short sequence showing the movement around 1:13 in aren't showing very even rotation either.

Edited By John Haine on 28/05/2022 12:23:15

Thread: Again - another whatsit
28/05/2022 10:01:38

I had something like that I bought at a market stall for the nice indicator which was a gadget for applying a small lift at one end of a beam for calibrating sensitive spirit levels.

Thread: Unusual Escapement
27/05/2022 14:15:37

**LINK**

https://en.wikipedia.org/wiki/Riefler_escapement

I still don't see this Duncan - if the bob is stationary relative to the suspension point but the latter is moving, the bob has momentum at least as it passes through the mid position, and therefore kinetic energy - where does that go for it to be stationary when it reaches an extreme?

Re simulations - the article I wrote for HSN described these as well as the analysis.

26/05/2022 21:23:36
Posted by duncan webster on 26/05/2022 13:42:04:

If we have a conventional pendulum swinging with an amplitude of say 1 inch either side of vertical, and then move the suspension point 1 inch either side at the resonant frequency but in anti-phase, the bob will stand still. ....

How can that be true? What happens to the stored energy in the bob?

The analysis of the conical pendulum assumes that forces are applied to the bob in the x and y directions, not to the suspension, but the results are essentially the same as the simulation which assumed that the suspension point moves.

26/05/2022 12:54:24

That's essentially true, but it is much easier to drive the pendulum at its "resonant" frequency. Yes, the pendulum is a "governor" but so is a conventional pendulum. In Bond's clock, and a related one made by Lord Kelvin, the but contacted the inside of a friction ring to brake it at the right radius for the required speed.

To Duncan's point, yes the string was offset from the motor shaft slightly, but once the system settles down the bob is rotating such that it is at the "opposite side" to the offset, so the effective suspension point is just below the drive.

26/05/2022 12:35:13

Horolophile's videos are very interesting - several escapements built from Lego plus other clocks working.

This conical pendulum is deeper than it looks. Back in the late noughties there was a lot of speculation about coupled pendulums. Observing that anti-phase coupled pendulums were less sensitive to horizontal ground vibration, the idea was that quadrature ones might be insensitive to vertical vibrations. It turns out that while two pendulums will easily synchronise in anti-phase it's impossible to make them do so in quadrature. A clockmaker called Colin Fergusson suggested that an alternative would be to have a conical pendulum, which in effect oscillates in two orthogonal planes in quadrature. He did an experiment with a bob on a string suspended from the shaft of a DC motor and observed a very pronounced "resonance" at a certain speed. This seemed to contradict the accepted theory of conical pendulums (as "explained" in one of the references cited above) which has nothing to say about resonance. When I was at school we covered conical pendulums on A-level physics and were told that they were not resonant like an ordinary pendulum.

It turns out this is quite wrong! As Colin observed, experimentally they are resonant! If you do simulations of them, or construct the equations, this is confirmed. They have a rather similar response to an ordinary pendulum, except that their "circular deviation" of rate with amplitude is the opposite sign. Also since the rate depends more strongly on amplitude the shape of their response curve is distorted, falling off more rapidly on the high-frequency side.

So the explanation of the clock in the first photos is that the radial arm applied a constant torque to the pendulum which accelerates it towards its resonant frequency. As it reaches that its amplitude, and therefore velocity, increase so it absorbs much more energy. Once the air resistance torque equals the driving torque the amplitude stabilises - just like a conventional pendulum.

Sadly it turns out that the conical pendulum is not insensitive to vertical motions. I wrote an article on this for Horological Science News, happy to share with anyone interested.

Of course the pendulum doesn't have to have the same period in the two planes, if the suspension is gimballed. Solar/sidereal clocks have been made with a single pendulum vibrating at different rates in the two planes with separate escapements driving separate trains and faces.

Bond's clock uses a conical pendulum governor that runs slightly faster than the main pendulum to drive a very clever escapement which is essentially completely "detached". There's a very nice description of it in Philip Woodward's My Own Right Time.

Thread: Best way to cut mild steel sheets
26/05/2022 09:29:37

Model Engineers Laser

Thread: My mobile has "gained" an extra synbol
25/05/2022 14:05:42

But once your phone was unlocked and you inserted an O2 SIM it had no connection whatever with Orange.

25/05/2022 14:04:51

Orange rebranded as EE which was then acquired by BT.

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