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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: My mobile has "gained" an extra synbol
25/05/2022 11:46:39

It's a voicemail left on the VM server in O2's network, not on the phone. On O2 you access voicemail by dialling 901.

Thread: Strange Miniature Bearing
24/05/2022 16:50:05

Aha! Peter you triggered my memory, it was on a Eureka clock brought along to an AHS meetup.

24/05/2022 12:51:24

I have seen that pattern of bearing mentioned somewhere with a horological connection, but can't remember where. I must say that I'd be inclined to replace them with conventional small unshielded ball races, or ceramic ball ones, with the grease washed out (not ultrasonically cleaned). Someone in Australia did extensive measurements of friction of standard ball races and found they compared favourably even with jewelled bearings. Seems to me to be no advantage in only having balls below the pin, the ones above won't be carrying any load so in effect "won't be there".

Thread: Miniature metric spanners
24/05/2022 10:21:01

I checked the set I have from MEL and the smallest is ~2.5mm a/f

Thread: Looks a lot like plastic
24/05/2022 07:14:07

Maybe derlin is heatproof?

Thread: Miniature metric spanners
24/05/2022 07:10:38

MEL have a standard set from which you separate the individual spanners. They are generic sizes and hopefully you can find one that fits the nut in question. I'm not sure what the smallest size is, can check. I have an excellent local tool shop that stocks a wide range but I'm not sure how small, but if you're in range of West Suffolk they are - don't sell online yet.

Thread: aluminium sticking to end mill
23/05/2022 14:40:14

On the CNC I tend to use 5000+ rpm even with 6mm cutters on 6061 Ali. I believe that cutting action basically involves the metal softening at the tool edge, if run fast it gets softer and has a chance to flow off before sticking. This is using 2 or 3 flute mills, preferably the ones made for aluminium. I don't use coolant but do have an air jet to clear the chips away.

Thread: Issue 249 Arduino Controller Indexer
23/05/2022 07:10:59
Posted by duncan webster on 22/05/2022 21:07:46:

Is it that the quoted voltage is what you need to pass the current? The dual voltage might reflect unipolar or bipolar configuration

Well as an example the motor data sheet I have on my desk (admittedly a NEMA14 type) gives a winding resistance of 6.8 ohms/phase and max current 0.8 A. At 12 V the winding current would be 1.8A, double that at 24.

Provided that this is just a stepper motor the OP is talking about and doesn't have an integrated driver, the quoted voltages are just spurious information.

22/05/2022 22:00:49

All decent modern motors will be bipolar since bipolar drives are now ubiquitous.

22/05/2022 12:04:54

I assume that the motors you mention don't have an integrated driver? Could you provide a link to the details?

Stepper mjotors as such don't really have a "working voltage". Modern stepper drivers actually supply a regulated constant current to the stepper using a switched-mode technique where they apply the supply voltage direct to the stepper windings for a short period then switch it off and let the current flow through a diode, with an on/off ratio set to get the required current. The currents in the windings are then modulated to get the required stepping/microstepping. If you could look at the voltage on the actual winding it would vary between the supply voltage when "on" and zero when "off" though with a very spiky waveform. The average might be only a few volts, but the supply could be much greater. The higher the supply voltage the better the motor works, provided the current doesn't get too big and cause it to overheat.

The 24/48V (assuming the motors don't have an integrated driver) is therefore fairly meaningless for a normal stepper motor, but it would be a normal sort of supply voltage range for a modern stepper driver. If your stepper works on 12V that's probably fine for a dividing head which shouldn't need much torque or high speed. I run my Ward divider from 20V, or the same mechanics+stepper from 24V for rotary/linear feed on my big mill; and about 40V using it on the CNC mill.

I hope this helps.

Thread: Cowells Milling/ Z axis design
17/05/2022 08:45:05

Steve, the clue is in the name, thrust bearing. What direction do the forces act when you operate the screw?

Thread: Tyres
13/05/2022 11:21:23
Posted by Circlip on 13/05/2022 10:36:46:

My 'cheap' Romanian Renault has a light on the dash telling me to 'Check tyre pressure' . Don't know how it can sense this, standard wheel nuts so there must be an inertial gravitational balance system built into the dashboard???? Yet another waste of electronic gizmo programming on modern cars.

Regards Ian.

They compare rotational speed between tyres on the same axle as measured by the antilock brake sensors. A/k/a wheel ticks. Since the sensors are there anyway it's just software.

Thread: 3 phase query - for a charity project in Africa
13/05/2022 11:10:53

I assume that being Africa it's usually rather hot? Solar gain and chimneys would seem to be the obvious solution.

Google solar dehydrator.

Edited By John Haine on 13/05/2022 11:12:47

Edited By John Haine on 13/05/2022 11:13:54

Thread: Re-boring Grind Wheels
13/05/2022 07:35:19

I suspect that the risks of damaging the wheel integrity and weakening it are too high to even attempt it, to be frank. I don't think they are that expensive, I'd suggest just buying some good quality replacements with bushes if necessary.

Thread: Barograph 'stiction'
12/05/2022 13:51:58

I think you mean "balance wheels" (sorry, inner pedant at work!). It might help just to dismantle, clean and oil the bearings.

Thread: Anyone know what these are called?
11/05/2022 19:14:31

He learned a bit from Roger Penrose.

11/05/2022 19:14:10

He learned a bit fro Roger Penrose.

Thread: Gallium
08/05/2022 17:50:28

Gallium Arsenide, an allow of Ga and As, is a III-V semiconductor and widely used in microwave and electro-optic devices. Your mobile phone probably has some in it. Gallium Nitride also a key material in microwave devices and increasingly in power devices for applications such as EVs. A most important element.

Thread: Thread gears for Warco GH-1322 lathe.
05/05/2022 15:39:41

Electronic leadscrew?

Thread: help wiring a 3 ph coolant motor
05/05/2022 12:01:17

If you have a winding backwards relative to the other two the motor will not run properly. Call the ends of the windings on the star point n1 for the nth winding and the other n2. Then wire 12 to 21, 22 to 31, 32 to 11. If the motor runs backwards reverse two of the mains connections.

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