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Member postings for Dave Martin

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

Thread: Quick release hook
15/11/2018 21:52:59


It might be worth looking at the design of the hooks used on the falls for ship's lifeboats, as they are remotely-releasable whilst on-load.


Thread: G-gem gib or g-golf -gib?
10/10/2018 09:07:45
Posted by Frances IoM on 08/10/2018 14:03:39:
except on IoM where in previous centuries could written as Killey - derives from Manx for servant (think of Scots Ghillie)

Frances, agree re Manx folk being comfortable with Gill Gill !

Re your suggestions on the Killey surname:

For those not from or familiar with the Isle of Man, It is not pronounced “Kill ee” like Kelly. Killey is pronounced “Kill” followed by a short “y” as in yacht or you; some older Manx folk pronounced a longer “y” so it sounded like “Kill yer”.

In terms of its derivation, Killey, like most of the Manx surnames that start with C, K or Q, have their roots in the “son of” Mac prefix; in the case of Killey the root patronymic suggested (AW Moore and JJ Kneen) is Gale, Gell, Gill, Kill or Kelly.


Thread: The size and shape of drill holes
06/09/2018 10:15:59
Posted by pgk pgk on 04/09/2018 08:07:27:

I had need to set some firm but removable pins into my current project. ......If I drill the hole with a bit labelled 5.5mm then overdrill with the same 6.0mm drill bit then i end up with a hole where the 6.0mm silver steel is too tight. - as in it goes in with a gentle tap but is a bugger to pull out........

Actually - that sounds you're drilling it perfectly and the dowels are fitting perfectly! Sounds to me like you're getting a vacuum lock. Solution: (i) if the workpiece will stand it, a tiny vent hole all the way through; (ii) a tiny hole through the dowel pin; or (iii) use a removable pin with either a vent flat or a spiral groove (have a look, for example, at the range of removable dowel pins in the MSC/J&L catalogue).


Thread: Let's hear it for British manufacturing!
06/08/2018 21:17:15
Posted by Bill Phinn on 06/08/2018 20:42:53:
Posted by Dave Martin on 06/08/2018 18:24:37:
Posted by Bill Phinn on 06/08/2018 14:46:33: .....Roger Smith the watchmaker merits a shout-out.

Bill - I'm delighted to see Roger Smith's team mentioned here, but his watches aren't make in Britain, or Great Britain, or in the UK...they are made here in the Isle of Man !

Yes, that's right.

And now I'm going to have to repay your good-humoured pedantry and point out that I used the word "British" throughout my posts, and that the IOM is incontrovertibly part of the British Isles.

Cheers Bill,

Yes, geologically in the 'British Isles' archipelago, but not British. We are, give-or-take a little for scale, as much a part of Britain as Canada or Australia are. We have our own legislature; we have our own currency; we have a Manx passport and we're not entitled to a British one unless one parent/grandparent born in UK. Those from the IOM aren't even entitled to NHS assistance (other than A&E) if they fall ill in the UK.

Because of our situation as you say in the British Isles, we do have a number of convenience treaties with the adjacent islands such as what is now being described as a Customs Union in wider British context, so goods, services and people can pass without hindrance.

Dave, a proud Manxman! (not so much pedantry as pride in my homeland!)

Edited By Dave Martin on 06/08/2018 21:25:30

06/08/2018 18:24:37
Posted by Bill Phinn on 06/08/2018 14:46:33: .....Roger Smith the watchmaker merits a shout-out.

Bill - I'm delighted to see Roger Smith's team mentioned here, but his watches aren't make in Britain, or Great Britain, or in the UK - they are made here in the Isle of Man !

Thread: The colour of threshing machines.
04/08/2018 21:19:05
Posted by larry phelan 1 on 04/08/2018 19:22:50:

All the combines around my way are painted yellow,never seen a red one yet.

New Holland = yellow, but MF, Intl Harvester, Laverda = all red; Fiat = red or orange; Claas = green & white, some John Deere = green.

04/08/2018 21:04:46
Posted by Robert Butler on 04/08/2018 19:56:24:

.... flat belts with serious metal joiners. ...

Known as Crocodile clips (not to be confused with the feeble things used to join electrickery circuits!)

Thread: Hello from the Isle of Man
09/07/2018 15:51:36

Fastyr mie yessir!

Dave (Andreas)

Thread: Wiring an NVR switch
16/06/2018 19:09:07

Dave (SOD) - its the adjustment for 'Full Load Motor Amps"


Thread: PID Controller - MEW 269 - wrong connector
16/06/2018 18:37:00

and here are two RS data sheets that list the contact materials used for different types of thermocouple

from which:


  All THERMOCOUPLE connectors use true thermocouple alloys for optimum accuracy, Except for Type R, S & B which use compensating alloys.

  Thermocouple Pins

  Type /  ‘+’ Positive Pin  /  ‘-‘ Negative Pin

  J  /  Iron  /  Copper Nickel

  K  /  Nickel Chromium  /  Nickel Alloy

  T  /  Copper /  Copper Nickel

  E  /  Nickel Chromium  /  Copper Nickel

  N  /  Nickel - Chromium - Silicon  /  Nickel Silicon

  R  /  Copper  /  Copper Alloy

  S  /  Copper  /  Copper Alloy

(Edit: - table format disappeared so separate columns with /  - crossposted with MichaelG at the same time!)

Edited By Dave Martin on 16/06/2018 18:42:37

16/06/2018 18:24:28
Posted by Muzzer on 16/06/2018 18:09:37:

.....If you look at the "proper" thermocouple connectors, you my be otherwise puzzled to discover that both contacts are made of the same material and plating, despite the thermocouple itself being composed of different metals. ....

Sorry Muzzer, but not so. That's why, even in the same form factor, you have a range of connectors which are appropriate for E, J. K etc. - they use appropriate connection pins or plating. e.g.:

(Edit: corrected link)

Edited By Dave Martin on 16/06/2018 18:27:19

16/06/2018 10:05:37

You're right Nige, it will work, but not as well. The thermocouple effect - in which the genuine signal is very small - arises from dis-similar metals at a different temperature to the 'reference junction'. Every change of material, such as using the wrong wire, introduces at least one extra thermocouple which will bring an error. Using connectors, there will be several changes of material, and with plated pins, there may be a number of transitions. Wrong wire and wrong connector errors can introduce errors of maybe up to 10 degrees or more; and they won't be just fixed errors - each transition is a separate thermocouple, so depending on ambient and temperature inside the enclosure, the errors won't even be fixed.

15/06/2018 23:16:56

Sorry Neil, but I think it does matter, I haven't time to dig out my Physics/ElecEng degree text books to calculate it though.

The article talks about "affordable precision" and "with great accuracy" - but then spoils it.

Proper thermocouple connectors are probably no more expensive than the XLR connector used. No excuse not to use them.

Also, re-reading the article, it describes using "thin gauge stranded wire for the thermocouple connections" - it should be the appropriate thermocouple material wires that are used to extend the thermocouple appropriately, not generic copper wire for both cores.

15/06/2018 21:40:07

An interesting article, but anyone considering building something similar should note that the author has used an XLR connector for the thermocouple instead of a proper thermocouple connector that should have been used.

Thread: sherry shelf life.
07/05/2018 11:05:13
Posted by richardandtracy on 06/05/2018 22:08:38:

......The one that goes off (solid) is Baileys Irish Cream. Given up on it as we don't drink it fast enough. .....

Golly, that takes me back to my student days. End of Autumn term, a house/course-mate and I had a lab report to submit before going home for Christmas, so we finished it late at night. There was a just-opened bottle of Baileys, which we decided would have gone off by the time we got back in January; after we disposed of that bottle, for some reason we decided the other bottle - even though un-opened - might suffer (loneliness?) - so that was seen off as well. When our lab reports were returned, they were marked "marvellous prose style but light on factual content".

Thread: 1ph to 3ph Electrics
01/05/2018 13:15:39
Posted by STK2008 on 01/05/2018 11:55:25:

....shall look up Walter Midgeley.

Just to make it easier to find if you're searching on-line, I've no connection but their name is Walker Midgley

Thread: Polishing mops
28/04/2018 09:18:44
Posted by Daniel on 28/04/2018 07:21:49:

Hello All,

Browsing through RDG's site, I see that they offer polishing/buffing mops in either white or yellow.

The product description makes no difference between the two.

Does anyone know if there is a difference ?...

Daniel, although the underlying material and dimensions are the same, there is a subtle distinction in the description in the advertisement. They describe the yellow ones as "Impregnated and especially stiff. For preliminary...." and the white ones as " soft ....For high shine polishing ....Adapts to the workpiece contour. "

Re Michael's comment about using colour-coding to distinguish between grades of polishing compound, you would almost certainly use different grades with the these two wheels. I actually use more grades, and more wheel types including sisal to start sometimes, so I use a 'sharpie' to mark each wheel as to what compound I use it with.

I have no connection with any vendor, I personally buy mine from the range sold by Caswell UK, they also have a useful guide to buffing and polishing, including wheels and compounds.

Edited By Dave Martin on 28/04/2018 09:28:06

Thread: "Reforming" VFD Capacitors
22/03/2018 22:24:44

What happens when a capacitor vents and then ....

Admittedly a somewhat larger capacitor than any likely to be used in a home-workshop VFD – have a look at the debris spread Fig. 3 on page 13 of the report.

Edited By Dave Martin on 22/03/2018 22:25:38

Thread: What did you do Today 2018
11/03/2018 11:03:20
Posted by Andrew Johnston on 10/03/2018 21:40:13:

...Finally I've hand ground a form tool and set the Britan up to make the rounded head on the "rivet" bolts previously machined:


I'll mull them over for a while before doing the whole batch. Not least because I'm otherwise occupied tomorrow as afternoon tug pilot.


Andrew - just out of interest, when you come to use these, how will the bolt be held whilst you tighten the nut?

Thread: Aluminium extrusions
07/03/2018 11:00:48


Depending on how many you need, and the finish required, it might be worth considering using standard rectangular material and then machining the bevel, much as you might on wood using a spindle molder. There are off-the-shelf metal bevelling machines – the one in this link only goes to 14 degrees but I’m sure something similar could be found to do a shallower bevel.

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