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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: 3 phase - radio puzzle
30/07/2019 17:36:23
Posted by Ron Laden on 30/07/2019 15:13:35:

So it is sounding like I need a filter at the inlet but not knowing what type/spec of filter I need I would appreciate some guidance at what I should be looking for.



Hi Ron,

What is the full model number of your CUB VFD? With that information I can recommend a suitable EMI filter.

The manual can be downloaded here

Robert G8RPI.

30/07/2019 12:52:33

It is likely differential mode conducted interference from the VFD causing the issue. You should fit a suitable filter on the inlet. Most VFD instructions say one is required.
The current from differential interference flows in opposite directions on the two conductors.(Live and neutral). Where these are close together and physically balanced the fields cancel and no signal is radiated. This is likely the case near the VFD hence no interference near it. The house wiring on the other hand is less likely to be balanced especially lighting wiring. Un-balanced or separated conductors act as an antenna so when the currents reach the house wiring they radiate and cause interference.

All VFDs should be in a swarf and splash proof (at least IP34, preferably IP 45 or better) earthed metal box with appropriate mains switching, fuse, filter, ventilation or space for cooling and cable glands or connectors.

Robert G8RPI.

Thread: Anyone recognise this mains connector ?
30/07/2019 12:24:56

Google DIN 49 491 and see if a local supplier comes up.

EDIT Don't forget to give those pins a good clean before you plug you new connector in even for a trial.

Robert G8RPI.

Edited By Robert Atkinson 2 on 30/07/2019 12:33:27

Thread: Motor plate help needed
30/07/2019 07:34:10

This will run from an inverter but as old mart says you will need a dedicated feed. Not necessarily it's own consumer unit (CU) but certainly it own 25 or 32A circuit breaker in an existing CU and either 4mm2 (possibly 6mm2) twin and earth cable or if the workshop is outside 2.5mm steel wire armoured cable (possibly 4mm 2 if a long run) to a dedicated isolator and box for the inverter.
If you have other large electric loads like a cooker, shower, water heater etc that may be on at the same time you need to look at the supply capability. Many houses only have a 60 amp main fuse so a bit of heavy turning while SWMBO is showering while dinner cooks and the washing machine is on might exceed the capacity of the supply.

Robert G8RPI

Thread: Guess the Chemical?
29/07/2019 12:40:16

A weird one is "Smartwater" from Coke where they distil perfectly good British spring water and then add Calcium Chloride, Magnesium Chloride and Potassium Bicarbonate back in! For starts if you are going to distil it why use spring water rather than tap water?

Bizarrely (to me anyway) people buy the stuff. I guess they are the same people who pay 3 to 4 times as much for the same painkiller or other medication with a fancy name and packet as the generic version. I just checked Boots website Neurofen 200mg tablets 14p each, generic 3p each. Neurofen is more than 4.5 times the price).

29/07/2019 07:48:36

A bigger risk with distilled or DI water is mixing containers. Many years ago I worked for a small airline on an island and we did frequent compressor washes of the turboprop engines but were still having sulphidation issues on the blades. The washes used distilled water bought in large containers from a local supplier. Turned out that their main market was the motor trade and they were not fussy about cross contamination between battery acid and water.
I found out when asked to pick up an order from Boots as I was going into town. My little car was totally filled with 2l bottles of distilled water. When I found out what was going on I suggested an Elgastat deioniser. It took a bit of convincing (DI could strip ions from the blades but as we added a detergent to the wash this was moot) but they changed to DI and had no further issues. It also cured the high failure rate we were getting with the "wet" NICAD aircraft batteries.

Robert G8RPI.

Thread: "I'm calling about your accident" - how does this scam work?
29/07/2019 07:36:17

Typically they are fishing for you to make a personal injury claim, either genuine (you hadn't bothered), exaggerated or plain false. A number of UK police forces got told off a few years ago for providing accident data to this sort of company. They may also be fishing for details to make a fraudulent claim.
SWMBO say the other side of this a few years ago. She scraped the side of a parked car while avoiding a speeding "white van" overtaking a cyclist in a narrow street. No one around so took details of car. and photos (I came out to make sure she was OK), left a note, called the police and our insurers. Owner rang to thank us for leaving note (he had been hit before judging by the two other colours of paint transfer. Insurance paid for both cars to be repaired, all done. Over a year later she got a call form "the insurance company" about the accident, thought it was a scam so told them to write to her. Letter arrived saying that as we had admitted liability for the accident they were going to pay the injury claim. No real references. So called them and it turns out a personal injury claim had been made for her hitting a empty car. Rightly they would not provide details but we stated categorically that there was no one in the car, sent photos (from two phones) and the police reference number. A few weeks later we got a letter saying they had questioned the claim and the claimants solicitor had withdrawn the claim without comment. The insurance company thanked us for our help. I don't know if it was the car owner or a third party who maid the claim of if any action was taken against them.

If we had not bothered to tell the insurance company they would have got away with it.

Robert G8RPI.

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.

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