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Member postings for Robert Atkinson 2

Here is a list of all the postings Robert Atkinson 2 has made in our forums. Click on a thread name to jump to the thread.

Thread: Acetone
27/07/2019 21:46:14

Fatal Acetone accident safety video

27/07/2019 21:26:18

Yes, pure methanol burns with a flame that is invisible in daylight. There is a video taken form a helicopter out there of a crashed tanker truck be sprayed with water by firefighters, suddnely the firefighters fall over for no apparent reason. The video then switches to the thermal camera image which shows a huge fireball.
MEK and Toluene are other solvents with fire hazards. Thy can be ignited by static generated by cleaning with a cloth.

Robert G8RPI.

Thread: Guess the Chemical?
27/07/2019 18:32:26
Posted by SillyOldDuffer on 27/07/2019 18:09:50:
Posted by lfoggy on 27/07/2019 17:09:35:

Those are all generic warnings so could be almost anything.

Not quite, for example the Firefighting measures include: 'Suitable extinguishing media. Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.' So it burns, and can be put out by water. That eliminates all non-combustibles like Common Salt, but also Fats and Oils. The warning about alcohol resistant foam indicates this is an alcohol or something like an alcohol, perhaps a ketone.

Whatever it is it's relatively harmless. It's not Chlorine Trifluoride!


Sorry Dave see MSDS for salt from Fischer scientific similar firefighting (just plain foam though). I've never seen salt burn!

Robert G8RPI.


Edited By Robert Atkinson 2 on 27/07/2019 18:43:53

Thread: Acetone
27/07/2019 17:20:44

Ordering quanties of it can also get you on a security watch list.


Thread: Guess the Chemical?
27/07/2019 17:16:54

Could be anything. I've noticed that a lot of Safety Data Sheets tend to err to the "safe" side with all sorts of over the top precautions. Not really helpful. Amongst other thingss if you put lots of nonsense on a well esablished materail it "dilutes" th importance of the precautions and can cause them to be ignored on worse materials.
Once had a customer send a sample of liquid they wanted us to test on a disenser we made/ They sent the MSDS and the health and safety officer said it was too dangerous. The MSDS required gloves, face mask and respirator. It was labeled light mineral oil (liquid parraffin in UK). Strangely enough the safety officer was happy for us to use baby oil!!!

Robert G8RPI.

Thread: Three phase motor checks
26/07/2019 18:46:08

Hi Peter,
If you don't have test equipment like a megger there re other checks you can do to determine if it's the motor or the inverter. While it's likely to be the motor, there are inverter faults that will only trip an RCD with a load connected. A quick check would be to connect 3 incandescent lamps wired in "star" in place of of the motor. initialy just connect the 3 phases an leave tthe center star point unconnected. The lamps should come on when the drive output is on. The brightness hould vary with speed, lower speed, dimmer and higher speed brighter. A difference in brightness between the lamps indicates a inverter fault. If all looks OK conect the center point to the drive neutral. If its still OK it likely the motor is at fault.

Were are you located? Maybe some one near you can help.

Robert G8RPI.

Thread: Colchester Bantam 1600 3 phase supply
24/07/2019 13:39:14

Hi Rick,

Have you looked a the existing motor to see if it can be re-wired as Delta (lower voltage) for use on a mdern solid state drive? For the reasons described in the original thread above, buing a new single phase (2 Phase) motor is not a good solution. Ideally buy a new 3 pase motor designed for VFD use and a VFD or fit an VFD for your cirrent motor.

Robert G8RPI

Thread: Threads used on electrical brass fittings
19/07/2019 13:01:04

No real standard. As Jason says PG is not uncommon, mostly on industrial fixtures though. Brass holders commonly have 10mm x 1.5, 20mmx 1.5 or 1/2" x 26tpi which does not seem to fit your description. Quite possibly some odd pipe thread.

Robert G8RPI.

Thread: Angle grinders - Dangerous or not
18/07/2019 12:40:17

I would not recommend buying any mains powered item from any far eastern seller on ebay or the like even if they appear to be UK based. For anything critical I will only use reputable established suppliers and brands.
I have recently seen a spate of dodgy kit:

A laptop style power supply supplied with an LED face mask beauty treatment system that I refused to pat test at all. I cut the leads off and broke it open and even the completely not technical owner could see the internal construction was terrible.

A 5V DC plugtop style power supply that had a loose circuit board inside, un insulated mains connections and less than 0.5mm creapage / clearance between the mains live connection and the output 0V

A PC style power lead with a fuse-less imitation of a 13A plug and conductors of 4 thin strands of something copper coloured but very springy. probably steel but I didn't even check before cutting it into short lengths.

All lethal and / or capable of starting a fire.

Robert G8RPI.

Thread: Faulty LED
18/07/2019 12:06:34
Posted by Speedy Builder5 on 18/07/2019 07:48:02:

Side lights, brake lights are all driven by the supply voltage of the car, in your case 12volts. You have a connection problem, not a voltage problem. As others say, check the socket / pins on your bulb and especially, check the earting of the socket to the body of the car. If its an old car, this would be my first thing to investigate. On my 6 volt cars, all electrical equipment has its own earth wire.

BobH (Austin 7 and 2CV)

This is not always true for modern cars. Typically the lights are driven via electronic switches that measure the current and continuity of the filament for failure detection. LEDs mess this up. Some even use PWM (switching on and off very rapidly) to change the brightness. I've only seen this used on DRLs and originally fitted LED light though.

Robert G8RPI.

Edited By Robert Atkinson 2 on 18/07/2019 12:18:43

Thread: Angle grinders - Dangerous or not
18/07/2019 07:29:18

It's the video that's dangerous.

It implies that you can abuse an angle grinder and use it without a guard and nothing bad will happen.
Just about any tool with an exposed cutting edge is potentially lethal, if it's powered then it's worse. They all need to be treated with respect. I have a Dewalt battery powered vibrating multitool which is great for softer materials and you can touch the running blade without injury but even dropping it switched off it could cut an artery if it hit the wrong spot.

Another interesting point about this sort of video is that the makers are potentially opening themselves up to lawsuits, especially in the USA. You are responsible for advice you give people.

Robert G8RPI.

Edited By Robert Atkinson 2 on 18/07/2019 07:31:41

Thread: Faulty LED
18/07/2019 07:15:33

A bit more information would be useful:

1/ Make & model of vehicle

2/ Make & part number of lights and/or link to ebay listing.

3/ Why are you changing them, did the old ones work OK?

Note that unless the lights are from a reputable supplier with "E" markings they are almost certainly illegal for use on the road.

Robert G8RPI.

Thread: Power supply problems for CNC rotary table
16/07/2019 21:47:29

I can confirm that the correct power plug for Sherline / Mumford controller (at least the one Steve has) is a 2.5mm x 5mm coaxial DC power plug. Fairly standard part.

Robert G8RPI.

Thread: Single DRO for 2 machines
15/07/2019 19:39:56

No reason why you can't use two sets of encoders one one readout. Details depend on the type of encoder. An optical one or magnetic with electronicss in the readhead would be simplist. What DRO are you looking a geting? a link to the model would be good.
I've one this sort of switching before with no problem.

Robert G8RPI.

Thread: Myford ML7 tailstock bore, and threading the barrel to fit a chuck
15/07/2019 13:09:36

How about a ER32 collet chuck on the tailstock? They will grip a round or hexagonal bow end quite well. You could even make a split nylon sleeve with a hex centre hole if you needed to grip tight without marking. Possible an adaptor tube to slip over the outside of the tailstock barrel and carry the chuck to maintain the full bore clearance.

Robert G8RPI.

Thread: Lathe improvements?
15/07/2019 12:52:22

Hi Niels,

Nice machining but it must be said that your electrical installation is terrible. This type of connection is just asking for trouble. The power input including the weight of an extension lead is hanging off the conductors. Even worse the earth connection is taking most of the strain. if this come off, even without any other fault the filters in the drive will put your lathe metalwork at 1/2 supply above ground, i.e. 110V AC. Admittedly low current, but even a slight shock around moving machines can cause other injuries as you pull away.

The drive should be in an enclosed box with ventilation protected from swarf and coolant and the power input and motor connections by either proper power connectors or cable glands with strain relief. The enclosure should also incorporate a fuse and suitable EMI filters unless they are included in the drive. I assume this is just a trial set-up but it can electrocute you just as quickly as a final design. Reaching across the motor, pulley and gearing to reach the drive is not great either.

Robert G8RPI.

Thread: Any other bowmakers on here?
15/07/2019 07:36:52

Couple of comments,

Cost - SWIMBO's bow cost more than my last car (both used, car not as old as the bow)

On carbon fibre , to get the best performance (weight, stiffness / flexibility in different planes for starters) would you not have to layup the correct combination of fabric and direction of lay rather than just cutting out of a pre cured sheet?

Robert G8RPI.

Thread: Aircraft radio scanner
15/07/2019 07:24:54

Any transmitter or in theory even a receiver. The relevant legislation is the Wireless Telegraphy Act 2006. Chapter 4 section 36. **LINK**

"A person who has a wireless telegraphy station or wireless telegraphy

apparatus in his possession or under his control commits an offence if—

(a) he intends to use it in contravention of section 8; or

(b) he knows, or has reasonable cause to believe, that another person

intends to use it in contravention of that section."

Section 8 says" 8 Licences and exemptions

(1) It is unlawful—

(a) to establish or use a wireless telegraphy station, or

(b) to instal or use wireless telegraphy apparatus,

except under and in accordance with a licence (a “wireless telegraphy licence&rdquo

granted under this section by OFCOM."

In practice you are unlikely to be prosecuted for having a receiver.
Software Defined Receivers (SDR) have been mentioned a couple of times. While SDRs can be great, the simple cheap USB Stick ones intended for TV reception do have limitations. For a beginner they can be quite daunting to set up. They need a PC or possibly tablet and this can cause interference issues. There are drivers and various versions of software to install. I have a couple of SDR's including TV stick and a much more expensive ~£200 unit. They are great for what they are but neither offers the "out of the box" operation of a handheld scanner and the TV stick does not offer anything like the performance of a dedicated scanner on AM Airband.

Robert G8RPI

(I have Amateur, aircraft and marine transmitting licences)

14/07/2019 21:17:01

I should have said that the Whistler does not have 8.33kHz channel spacing. It's an American market model and they have not taken up 8.33kHz yet. SOD and Andrew are correct, you technically need a licence to transmit or receive airband but reception as a hobbyist is normally ignored. I have personally seen commercial aviation companies told off for 1/ having a ground radio that could be tuned to other than their licenced company frequency, 2/ playing the tower frequency as their telephone hold "music". It is now illegal to have a transmitter without a licence. This was changed so that they did not have to catch unlicenced operaors with their finger literally on the transmit button. Transmit wilfully and they will come after you. There was a case at Cambridge a couple of yer ago and the offender was cught and proscecuted.

One other thing is that there is less information being transmitted to airliners by voice as digital messaging is being usesd more and more. Google ACARS and CPDLC for more info.

Robert G8RPI

14/07/2019 16:06:44


I'd suggest the Uniden / Bearcat EZI-33 XLT at £60- £80. Lot's of suppliers in UK e.g.

One important feature is the availability of 8.33kHz channels. This is a fairly recent change so mny older receivers only tune to 12.5kHz channels. While not used a lot yet it's good for future proofing.
For home use a outdoor antenna will help a lot, You can make this yourself.

Robert G8RPI.

Edited By Robert Atkinson 2 on 14/07/2019 16:07:14

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