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Member postings for Martin W

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

Thread: Fulfilled by Amazon
17/07/2021 19:02:12

RCDs work by detecting any differential current between Live and Neutral and when this exceeds a preset level the unit activates and disconnects the mains supply within a specified time. Therefore if one touches a live wire and their body completes a return path i.e. damp shoes and wet grass then the unit will trip if the current exceeds the specified maximum which is nominally 300mA. This provides protection for the user irrespective of whether the system is two wire or 3 wire.

There is a popular misconception that these units work by measuring current flowing in the earth wire. Earth wire current is not measured by RCD units, in fact the earth connection totally bypasses the active circuitry of an RCD.

 

edit: Last para

Edited By Martin W on 17/07/2021 19:09:31

Thread: Map Scale mystery
30/06/2021 14:28:04

Michael

Is that 34min 30sec east or west of the Greenwich Meridian as was. devil

Martin W

Thread: Surface finish when turning.
27/06/2021 01:10:00

All the gibs tightened/snugged up, half nuts clean and locking firmly, gear train driving the lead screw clean with no swarf/muck in the gears? Can't think of anything else other than obvious problems like tool chatter/spring, spindle bearings, belts etc.

Thread: How Elgin made Jewels for Chronometers
23/06/2021 11:02:13

Thanks for that Michael, no wonder that jeweled chronometers were so expensive to produce in those days with so much manual input required just to produce the bearings let alone the rest of the instrument. All I can say is thank goodness we don't live in the same world today. What with naked flames, exposed moving parts on machines, toxic/corrosive chemicals, and no PPE modern day HSE would have had a fit.

That said it is always interesting to look back to see how things were done, especially in times of need. Workshops with banks of lathes and their operators are now a thing of the past with cnc machines each producing more output and to a far higher standard than those workshops, progress yes I think so. You only have to look at modern car engines that run for over 200,000 miles and other than having a regular service never needing to be worked on.

Thanks again Michael for another interesting look at the world.

Martin W

Thread: Flintlock pistol plans
19/06/2021 10:15:44

OOPS

Sorry for my digression from topic Bob but the memory flashback reminded me of the fun we had as kids. That said I am glad you were entertained by the diversion.

Mick B1 that just raises a lot more memories, but nuff said for now.

Martin W

19/06/2021 00:39:21

Noel

Probably a blessing that I wasn't aware of the existence of rocket rook scarers when I was younger as my digit count might not be the same as it is now, a full set.

Martin W

18/06/2021 17:08:09

Buffer

That takes me back 50-60 years to the wilds of Wiltshire and bangers, bird scarers, on a rope. They certainly had a lot more thrutch than any legal firework you could get your hands on. Different times with different rules but we had a lot more fun it would seem and didn't harm anybody except maybe ourselves occasionally.

Thanks for the memory.

Martin

17/06/2021 15:44:20

Michael

Had a look at the drawings in the wheellock article you linked and the dimensions looked a little clumsy, 3 decimal places. Did a quick metric conversion of several of these measurements and they have all turned out to be extremely close to sensible metric dimensions. It looks as if this was originally drawn in metric and then converted to imperial for the article.

That said it looks interesting so thanks for that.

Martin W

Thread: A bit more upcycling.
13/06/2021 00:49:00

Great, I think it is brilliant.

Cheers Martin.

Thread: Ideas on how to make a nylon Stiffnut 'less stiff'
06/06/2021 02:01:25

How about using a plain nut with a low strength and slow acting/setting thread retainer such as Loctite; other thread locking fluids are available. This way you get the best of both worlds with a nut that can be tightened with minimum force and after 24hrs or so a nut that will be more secure than a bodged nyloc nut, probably better than a non bodged nut.

If this is a fit once installation and you don't plan to remove the nut then use a medium or high strength thread retainer. Horses for courses as they say smiley.

Hope this helps.

Martin W

Thread: The worst 'upcycling' tragedy ever?
24/05/2021 14:10:45

Martin - Now that I like so much better than the parts being recycled into mass of baked bean cans. However I think that the perpatrator of the subject recycled unit should have it chained to his leg as an example of how not to do something.

Martin W

Thread: Help with Electrics on a Bow Bending Iron
16/05/2021 19:20:21

I would have thought that the risk is minimum as all the terminal blocks that can be seen in the photo are marked 'N' and the live wires appear to be terminated in screened finger proof enclosures. It only becomes dangerous if some muppet wires up the mains three pin plug incorrectly.

Many of us live with and use bog standard toasters where the live mains is easily accessed with metal objects i.e. cutlery, skewers, etc. all of which are readily to hand and make tempting tools, especially for little hands, for prodding/poking the internal workings of said item. How many of us actually think that when these devices are working that parts of the bare metal element are actually at mains live potential and relatively easy to access.

Just a thought

Martin

Thread: elmers engines plans
07/05/2021 01:11:09

It's a thread definition/specification for UNC type threads much as we have Whitworth, BSF, BA etc thread definitions. If you want details then google #5-40 threads and you can get the actual diameter and pitch for each number.

Martin

Thread: Covid, DNA and Fred
25/04/2021 16:09:57

Thanks Martin it's good to remember these unsung pioneers in whatever field they achieve fame.

Martin

Thread: JD Metals
25/04/2021 09:54:24

Although a very low volume user of metals I will not buy any metal unless the seller gives the basic specification for that product. Motto 'If they can't be bothered to supply this data then don't purchase' no ifs or buts.

Martin

edit: re-worded

Edited By Martin W on 25/04/2021 09:56:48

Thread: Spy Pixels in Emails
17/02/2021 10:17:02

Found this article on the BBC news site earlier. It's worth a read if only to see who is looking at your data and responses.

Martin W

Edited By Martin W on 17/02/2021 10:19:43

Thread: Venturi calibration
31/01/2021 18:19:29

Clive

I don't know how large the venturi is but is there any merit in attaching it to a vehicle, out of the vehicle's local airstream, and measuring the vacuum produced at a number of fixed speeds. A simple manometer could be used to measure the vacuum at the different speeds and then using the same manometer the reading of vacuum measured at each speed could be reproduced and applied to the indicator unit. The actual value of the vacuum won't necessarily be known as this method will only produce relative displacement levels for each speed point, unless of course you choose to calibrate the manometer.

Just a thought

Martin

PS

Assistant will be required to monitor the manometer.

Edited By Martin W on 31/01/2021 18:22:04

Thread: So Much For CE Labels!
25/01/2021 10:22:26

It's not unusual to find 'fully plastic' earth pins on double insulated products as their only purpose is to open the gate on UK style 13A sockets and clear plastic on 13A plugs have been around for quite some time though they are not my style.

Martin

Thread: Some quite astonishing ‘metal bashing’
18/01/2021 23:36:36

Michael

That is absolutely brilliant, the way that the plates are formed and laid out look like the muscles of the real beast; then there's the head which takes it to another level.

Thanks for sharing it.

Martin

Thread: Chester DB8
07/01/2021 16:09:55

If the DB8VS has the same arrangement as the DB7VS then the pulleys are plain V section and don't have teeth. The only reason for using a toothed V belt would appear to be to give it the extra flexibility to accommodate the motor drive pulley diameter. If so then the number of teeth per unit length is irrelevant.

Martin

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