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Member postings for Toby

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

Thread: Motor speed control on AC motor?
30/01/2018 14:06:15
Posted by KWIL on 30/01/2018 12:39:29:

I have a 13A socket permanently wired to the output and a flying input lead with plug which addresses the safety aspect.

as long as the supplying socket polarity is ok.

I always run mine via an isolating transformer but that is more so I can safety connect up test equipment to the device under test.

30/01/2018 14:03:03

The other problem with a Variac is the cost, especially if you need a big one. Expect to pay between £500 and £1000 for a new 10A Variac.

Dave

cheaper than you think: **LINK**

Not my choice for motor control though.

Thread: what is this metal?
26/01/2018 16:17:50

First, no the FIL was not in the nuclear business. He was a toolmaker.

I do know someone who is and I asked him if he could take it into work and get it checked. The answer was not printable

It doesn't oxidise, the scraping in that picture was done before christmas. It is also fairly soft - when scraped with a knife it feels as soft as copper although I haven't tried properly cutting it. I am pretty sure the colour is the base metal, not any form of plating.

It also looks like it has been cut from a longer rod, both ends sawn and the dark covering in the pictures is I think just general dirt from sitting in a box of rubbish for quite a few years.

So far I am liking Rod's suggestion. I gather copper tungsten is used for welding electrodes so that would fit with where the FIL worked.

Shame, I was trying to convince myself it was 18ct Gold although I knew that was a bit unlikely

26/01/2018 09:48:08

Recently I was clearing out a the garage of my father in law. Amongst the junk I came across a small bar of metal that felt a lot heavier than I would expect for the size.

On closer inspection it scrapes back to a light copper colour but appears to be denser than copper.

Dimensions are 6.4mm diameter and 48.25mm long. Weight is 22g on my kitchen scales. I calculate that as 14g/cm3.

So unless I have got me sums wrong it is denser than lead (11g/cm3) but the only stuff denser than lead that I can think of that is coppery coloured is gold but that is much denser at 19g/cm3.

Has anyone got any bright ideas or ways I could better identify it?

https://www.dropbox.com/s/k62nu1pf4t4gsws/20180126_093459.jpg?dl=0

Edited By Toby on 26/01/2018 09:49:26

Edited By Toby on 26/01/2018 09:49:43

Thread: Tool Holders for Dickson Clone
04/04/2017 09:03:54

A heads up for anyone tempted to buy dickson toolholders cheap on ebay from india.

I just bought a couple for my boxford from "globaltools2016" because UK suppliers appeared to be out of stock. They don't have a chance of fitting without significant modification.

My post is an original Boxford badged one and (from the look of them) I have a mix of original holders plus later clones which all fit fine so I am pretty sure it isn't the post. However the globaltools2016 ones need a significant amount removing from the Vs to fit.

I also agree with the comments about the difficulty of making them accurately, having milled the Vs deeper I am going to have to resort to hand finishing to get them to fit without rocking.

Thread: Aircraft recognition problem
28/03/2017 12:59:10

well, in 2010 you could have bought a part share of one at White Waltham, so they do exist in the UK.

**LINK**

I would not have described it has having parallel trailing and leading edges though.

27/03/2017 10:30:35

high or low wing? and what do you mean by wingtip bulges?

A Druine Turbulent is small and has parallel leading and trailing edges on the wing and tail.

**LINK**

Thread: Dremel 3000 slow speed problems from new
26/03/2017 10:45:33
Posted by Neil Wyatt on 26/03/2017 10:34:09:

Is it possible that some which stop working need new brushes?

Neil

Quite likely but I don't think mine did. I can't remember the details but I do know what when I took it apart the whole thing looked so cheaply made (and didn't run well from new anyway) that I wasn't much interested in fixing it.

I am hoping the more expensive dremels are still of decent quality but I am afraid the 3000 spoiled the brand for me.

26/03/2017 10:08:32
Posted by Neil Lickfold on 26/03/2017 07:18:03:

I had a Dremel 3000, it was junk.

......

my experience as well

mine was replaced (when it stopped working) with a Proxxon which is in a decent league. Quiet, smooth and (so far) reliable......

Thread: Armoured cable - what size would you reccomend
21/03/2017 19:38:04
Posted by Nathan Sharpe on 21/03/2017 19:18:55:

I was taught that SWA armour was to be used as an equipotential bonding conductor and should be connected to the circuit protective earth. The Reg's still state this. On periodic inspection testing the continuity of Bonding, Circuit Protective Earth and Phase Conductors is carried out on individual cores/wire armour to make sure that all potential current paths are proved to be ,A) continuous, and B) meet minimum insulation resistance requirements. This will show up any existing and any potential faults with the cable if the IR is less 1.5megohm. The Reg's state that while a circuit showing IR of 1.5 megohm is acceptable further investigation should be undertaken to find any latent faults within the circuit. Nathan.

Sorry, but the regs do not state that

The armour *can* be used for bonding but only if it is sized correctly for the bonding, again, it is down to the individual circuit design. It certainly does not have to be used for bonding but as a minimum it should be properly terminated and earthed at the supply end as for any exposed conductive part. Of course the first job is to determine whether bonding is needed or not

21/03/2017 19:07:08
Posted by duncan webster on 21/03/2017 18:29:34:

I'm about to show my total ignorance here! If burying a pipe (should that be duct?) cant you just use 4 or 6mm twin and earth (not armoured) inside the duct?

duct or conduit

To be clear we you should not put T&E (or any other "mains" cable) in the same conduit as signal cables like ethernet etc. If you want both you need two conduits.

Yes, you can use T&E but...........

1) T&E is strictly speaking only approved for "dry or damp" conditions, not submersion in water. If there is any chance your duct could fill up with water then using T&E is suspect. That said, I have never seen T&E degrade due to sitting in water.

2) The ducting really should ideally be good enough to provide mechanical protection, so a typical 20mm plastic conduit isn't really up to the job. Plus it will be a bit small to pull any reasonably sized cable through.

3) Taking 2 into account SWA is almost certainly cheaper than T&E plus decent ducting.

That said, ducting is a good idea if you ever think you might need to replace the cable. Just make sure it is large enough as there is nothing worse than trying to pull a stiff cable through ducting that is too small for it!

Thread: Motor modification for VFD
21/03/2017 13:29:24

fwiw, the motor on my Meddings drill is 0.75HP and is rated at 1.7A FLA for 440V star and 3A FLA for 240V delta. Running it as delta from an inverter (with about 240V out) and the inverter (a yaskawa) reads 1.7A no load and around 1.8A when drilling a 1" hole through steel. So it never gets anywhere near its 3A FLA.

So yes, 5A means there is something wrong.......

(btw the inverter I use is a Yaskawa J1000 (0.75kw/0.4kW)

Edited By Toby on 21/03/2017 13:30:34

Thread: Armoured cable - what size would you reccomend
21/03/2017 13:09:30
Posted by Martin 100 on 20/03/2017 21:49:59:
Posted by Mark Rand on 20/03/2017 19:46:46:

The wiring regs call for a maximum 2% voltage drop on a circuit at its maximum load. So use that for the calculations.

It used to be 4% in the 16th Edition of BS7671, but the 17th edition (2008) altered that to 3% for lighting circuits and 5% for 'other uses'

Bear in mind you not only need to consider the votage drop but the earth loop impedence and the electrical protection for the cable (MCB /RCCD/RCBO) to ensure suitably fast clearance of any credible fault. Also the export of an earth from the main premises may not always be advisible, and you may need to leave the armouring isolated at the remote end and use a local earth spike.

This is a brief overview

**LINK**

You really need someone with specific knowledge of your existing installation particularly the earthing method in order to design something that meets the requirements of BS7671 and to test the final installation and thus ensure an adequate level of safety.

Edited By Martin 100 on 20/03/2017 21:50:53

imho the best advice so far, especially the bit about needing specific knowledge of the existing installation. You are only guessing if you don't know what the existing earthing arrangements are and have measured the Ze and Ipf.

Posted by Bazyle on 20/03/2017 23:34:26:

While you are digging the trench bung in a plastic pipe to carry a phone line, Ethernet, doorbell, and most important burglar alarm wires. Ok I know we are all wireless for everything now but you might find some of those don't work at the distance with electrical motor noise etc.

 

Also excellent advice, although I did just this about 5 years ago and still have an empty pipe running under my lawn. I really must get around to using it....... ;(

Thread: Milling - What am I doing wrong
03/03/2017 17:58:06

If the diagram is the top view of the piece surly the one that is tapering up is the one that is NOT climb milling (ie the "bottom" one?

Stephen: surely if the workpiece was bowing that much you would see it? There looks to be a few mm taper on the cut but the bottom of the workpiece is still flat on the table?

Just curious btw, I don't even own a mill!

03/03/2017 17:52:06

quill or z-axis not locked well enough?

Thread: Anybody know what these are ?
03/03/2017 16:32:23
Posted by Howard Lewis on 03/03/2017 15:12:01:

With regard to bolt stretch, the most efficient use of a fastener is to tighten it to JUST put the material into yield. We used to tighten W Range 1/2 UNF bolts so that they took on a permanent extension of about a couple of thou. By this time, the load in the bolt was circa 9 tons. And we found that the bolt could be retightened in this way 6 times or more, so we advised 4 times in the field, before replacement was necessary.

The machine monitored angular rotation vs torque for each spindle. When the previous angle/torque relationship began to increase, it sensed yield and stopped rotating

To see the machine tighten 32 bolts from finger tight into yield, in barely 7 seconds , was quite impressive.

Lots of vehicle manufacturers now tighten the important fasteners into yield.

Howard

Edited By Howard Lewis on 03/03/2017 15:14:04

That is interesting. I always though that if you tightened a bolt to yield you needed to replace it if it was ever undone. It sounds like you are saying this is not always the case?

Toby

Thread: Voltage drop
24/02/2017 10:41:15

and if you want to know the ratings of different cables a quick google search found this:

**LINK**

The voltage drop in those tables is per Amps per meter but that is basically the same as Ohms per meter if you want to use ohms law and relate it to Clive and Muzzer's posts.

Thread: Replacing Flourescent Tubes with LED tubes
22/02/2017 19:55:49
Posted by Hacksaw on 22/02/2017 19:23:07:

Question. Those 12v domestic downlighters type , (like the one for showers ,and kitchens (they look like a 240v GU10 but with 2 skinny pins )that run from transformers in the ceiling void ...I guess they wont work using a car battery ? I know the incandesent ones will but the new LED ones ? 12v AC?

I don't know about all but at least some work on DC.

eg this one: **LINK**

specifies 10 to 30V dc

22/02/2017 18:07:15

I reckon most here will have tubes that are over 10 years old but we think they are "fairly new".

In reality they will have degraded and not be giving out anywhere near the light they used to. Coupled with dirty covers, no reflectors and gray ceilings (and, dare I say it, failing eyesight....) we decide they are no good.

In 10 years time we will all be complaining that these "new" LED lights are not all they were cracked up to be when fitted and be looking for something that is better.

Don't get me wrong, if fitting new lights I would seriously consider LED but if it is just improving an old setup then perhaps a good clean, a new tube at about £2 and a fresh coat of paint on the ceiling might just do it?

Which reminds me, my workshop lighting is very dingy, perhaps I need to put my money where my mouth is

Edited By Toby on 22/02/2017 18:07:48

22/02/2017 11:08:55
Posted by Gordon Tarling 1 on 22/02/2017 10:25:47:

I am slowly replacing the HF fluorescents in my workshop with LED tubes by converting the existing fittings. Although the spec of the LED tubes shows a lower lumen output than the fluorescents, I find that the LEDs actually seem brighter and give a little more light. This is probably down to the fact that the LED tubes only radiate their light downward, whilst fluorescents radiate in 360 degrees. My advise would be to check lumen outputs of the tubes you're considering very carefully. then try just one and see what you think. BTW, the tubes I'm using are Ledlite 5ft, 24W Cool White, 4000k, 3230 lumens.

Edited By Gordon Tarling 1 on 22/02/2017 10:29:21

excellent advice and I agree, things like whether the fittings have reflectors make a big difference to fluorescent (hence me suggesting painting the ceiling white.......).

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