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Member postings for Mark Rand

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

Thread: An Uninvited Guest!
26/10/2021 16:03:14

Probably need a greater rate of cut and a better chip breaker if the swarf is coming off like that.

Thread: Sewage dumping
24/10/2021 10:30:26

The issue tends not to be a systematic one, but is often caused by surface water that is discharged into foul drains. This shouldn't happen, but does in older properties that did not have separate storm and foul drains and also happens with illegal/incorrect newer building work.

The foul water flow should be pretty much independent of the weather but if surface water is allowed into the sewers, then the treatment plants get overloaded in stormy weather.

This opinion is worth almost as much as it cost. blush

Thread: Vice
22/10/2021 10:05:28

Noah Webster ought to be suffering many torments for the butchery he did to our wonderful, mongrel, language.

Thread: Load reactors for VFDs
17/10/2021 20:02:55

If you dig into the sine wave filter link I posted, you'll find a page for chassis mount (non-enclosed) filters, which has a handy table of the inductance and capacitance that they use for various line currents:-

**LINK**

That seems to give a resonant frequency of about 3kHz, which is reasonable for a >4kHz VFD switching frequency.

16/10/2021 19:29:34

Couple of points:-

  1. The motor won't generate spikes due to leakage reactance or anything else.
  2. adding series reactance won't increase spikes.
  3. Adding parallel capacitors to VFD output in contra-indicated.

Other than that, a sine wave filter (series reactor followed by parallel capacitors will reduce any whining from the motor and reduce any spikes. I use one on the output of the inverter that feeds my workshop.

Thread: SKY abandoning their satellite customers
12/10/2021 20:04:09

Virgin/Telewest didn't instal fibre in the street for their 'fibre Internet' it's co-ax cable in the street, with a fibre feed to the cabinet.

Oddly enough, my BT supplied 'fibre to the cabinet' (as opposed to 'fibre to the premises' is fibre as far as the converter on top of the telegraph pole directly outside the house!

Thread: GDPR
12/10/2021 19:53:14

Quote from the article:_

" "Anyone else in the world would have that say. Just because we're footballers and we're in the public domain that gets overlooked. "

But that's just it. The information is in the public domain...

Thread: Hardinge HLV H
23/09/2021 20:26:43

It's very easy to turn the hardinge nose taper to make chuck back plates. I've made a faceplate with an integral mount and two chuck backplates. The 3 and 4 jaw chucks I got with my HLV were in a very poor condition, although I managed to get some soft jaws and a new scroll from Rotagrip.

Thread: What do you think of this con
21/09/2021 20:41:42

Tell us what you really think! laugh

Thread: Disc drive - Anything useful inside ?
20/09/2021 20:35:20

The magnets can be useful, the motors often not, it can be a lot of work to get the bearings out without damage.

You need a lot more than one drive, but you make them into useful raw material:-

alloy.jpg

Thread: J&S 540 Smoking
18/09/2021 22:40:18

It can be almost impossible to detect a shorted turn with a resistance meter. If you have a meter that measures current, then measuring the current to the motor on each of the three phases is more likely to detect a winding fault. Ok, it'll need three goes at disconnection-meter connection-reconnection, but it will show if there is a poorly phase on the motor.

Before you start this, is the grinder being fed from a good balanced three phase supply or a static or rotary converter? If the latter two, are the phase voltages reasonably balanced or is the generated leg much higher than it should be?

Thread: Back to Imperial
18/09/2021 21:07:36

When working on steam turbine performance tests in the '80s, I tended to think in terms of psi and °C when I wanted to visualise things. I still do.

All of my machines are basically imperial, but the milling machine has a DRO and the lathe has dual metric/imperial dials. I work in whatever units fit the job, the materials or the tools to hand in most cases.

 

PS:- putting the crown stamp on pint, half pint and 1/3 pint glasses always made more sense than the CE mark. It's a singularly British/UK concept, although the Australian pint is very close. It never featured as common usage in any other EU country.

 

Having said that, the fact that David Bl***y Frost is having it reintroduced makes me want to retain the CE mark due to the mess that he and his mates made of the negotiations to part from our friends across the channel.

Bah! Humbug! Mostly down a 750ml bottle of Green Jack Baltic Trader Stout. cheeky

Edited By Mark Rand on 18/09/2021 21:33:10

Thread: Leadscrews and other features of Asian milling machines
16/09/2021 19:41:22

I'd draw issue with a couple of the points others have been made:-

  1. Scraping should be done on all mating surfaces if at all, not just half of them. Scraping is for precision alignment not just oil control or cosmetics. Flaking will normally only be to half the surfaces and should only be done to the surfaces which aren't visible i.e. not subject to grit falling on them. This is done for oil control and (on the wrong surfaces) for cosmetic reasons.
  2. The most important things about the feed screws are how much backlash there is, how much variation from the best to the worst parts of the travel and are there arrangements for adjusting the backlash. this is important when climb milling.

Bear in mind that a top speed of 1750rpm is not optimal for cutters less than 5mm in steel or 25mm in aluminium. Still works, just not optimal.

Thread: What to drive a J & S with ?
10/09/2021 21:06:18

The one I run my shed with (3ph J&S1400, Hardinge HLV, Beaver mill, BCA Mk111, and Wolf grinder) is 240 in 415 out sourced from drives direct. it's a normal VFD modified by them to have a voltage doubler instead of the normal rectifier inside.

My previous setup was a superannuated Danfoss VLT 5000 series drive that i was given for a tenner.

Both ran/run any of the machines without modification. I can't really run more than two or three machines at a time without help from her indoors, but that many aren't a problem...

Thread: They see you coming
09/09/2021 19:33:58

For 35 years I've used a firm who only do MOTs. I am completely confident in their assessments because they have no relationship with any repair company. The only time I had cause to raise my eyebrows was when a young lad they's nod had for long pointed out that my (GRP) Renault Espace door was rusting through from the inside. It wasn't, the GRP was delaminating. laugh

Thread: A stark reminder to leisure cyclists !
05/09/2021 20:32:22

Have you never seen a Bugatti Veyron trade or a Rolls Royce Phantom pickup?

cheeky

05/09/2021 14:59:17

Anyone know the speed limit for a car towing a trailer or caravan on a motorway?

If you said 70, then you need to re-learn the rules...

Thread: internet cable
04/09/2021 09:35:35

^^^ Cat 5e can handle a bandwidth of 100MHz to a distance of 105 metres and a data rate of 2Gb/s. (part of the magic that allows more than one bit of data for every change in voltage, it isn't just on and off. Gigabit uses all four pairs, 10 and 100 use only two pairs)

 

There's no need for Cat 6 unless you intend to run 10Gb/s and that won't be to standard unless the sockets were replaced with correctly installed Cat 6 hardware. As Michael points out.

Edited By Mark Rand on 04/09/2021 09:38:57

Thread: Is the EV industry in too much of a hurry ?
01/09/2021 10:10:43

Having been in a petrol Ford Orion (escort with a boot) that caught fire, I can say that when an ICE vehicle gets burning, the fire brigade can't do mutch with it.

Thread: Is there any benefit to copper plating before nickel plating?
30/08/2021 20:46:49

Get thee behind me satan, and push!

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