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: VFD Cable Supplier Recommendations|
Twisted pairs are not suitable for reducing interference on 3 pahse circuits like VFD to motor. For twisted cable to be effective the signal on the conductors should be balanced. For two core thai is easy to understand the fields from the conductor carrying current out are cancelled by the fields caused by the current coming back. You can see this with a compass, a few feet of wire and a AA cell. lay the wire in a big loop with the compass 1/4 way along the wire. Connect the cell for a second (yes a short circuit) and the compass will deflect. Now bring the last 1/4 of the wire and lay it close to the fist part without moving the first wire or compass. Connect the battery for a second and the compass deflection will be much less. Twist the two wires together as they pass the compass and there will be no deflection.
As others have mentioned a length of 2.5 mm 4 core SY cable (i also use TLC for short lengths ) https://www.tlc-direct.co.uk/Products/MF2dot5slash4.html Is perfectly adequate for your application.
|Thread: Replacing a 24V AC machine lamp|
No problem getting G6.35 24V AC LED lamps
Random amazon example
No idea if it is a good seller just an example of a lamp.
|Thread: Thoriated tungsten electrodes|
As a private individual you now need a Explosives Precursors & Poisons (EPP) licence to possses Mercury. This applies even if you already had it. There are exaemptions for when it is part of something else e.g. fluorescent lamps.
Mercury is of course both a EP and a P.
|Thread: A TOPICAL point, FANS.|
WD 40 is flammable. Don't spray it on the brushes when the motor is running!
|Thread: Battery fire in electric cars after a collision|
One big difference with batteries compared to petrol, diesel, LPG CNG or even hydrogen it is hard to remove the energy source after accident damage. The fluid fuels can be drained, vented or even deliberatly bunt off. If the casing is damaged in a crash they tend to be self emptying. All thesw leave a safe wreck for disposal.
The battery packs do have an isolator that is used for servicing / rescue and will also protect against shorts external to the battery pack. On my Plug In Hybrid (Outlander) this is a plug on the top of the underfloor battery pack and is accessed through the rear passenger footwell. It does however need tools to operate it. I carry the required tool in my glove box so in the event of any incident I can isolate it myself.
|Thread: Thoriated tungsten electrodes|
A couple of facts:
|Thread: Grinding and cutoff discs for angle grinders|
+1 for Nicholas Wheelers comment
Cheap off-brand grinders tend to be heavy, noisey and poorly balanced (both handling and vibration). For anything other than very occasional, rough work the investment in a branded tool will be repaid with easier use, better performance and less noise.
|Thread: Failed Miller Transportation|
Lucky it didn't fall through the soft side of the lorry and hit another vehicle.
|Thread: Vickers Bl 8 inch Howitzer cannon of 1917|
Not directly related but the pictures of obturators reminded me of this accident report:
|Thread: Nostalgic moment|
Yes it did a couple of times. We spalled the concrete in one of the ground running bays with the re-heat . Though the bay was rated for the Phantom which used the same engines (RR Spey 202) the car was closer to the ground.
Yes The HA was 1983.
My first "car" was a Bedford HA van. Bought in 1883 for £50 and did most of my learing in it. As bought it had a habit of going into reverse instead of first. A mate and I dropped the gearbox and found the thin wall tube suporting the gear selector was bent at one end. I forget the exact deatils but a replacement was turned up from a bit of aerospace ggrade structural steel tube at a local company as a favour. Aftter it was all back together the Haynes manual arrived and apparently we should have taken the engine out rather than just unding the mounts and pushing it forward. We didn't hve a engine crane or similar. I drove it from Bristol to Northern Ireland fand back on holiday. Unfortunatly the person I sold too crashed it while under the infuence.
|Thread: HOW FAST - ANEMOMETER CALIBRATION ?|
Yes this, but do at least two runs in opposite directions to average out the effect of wind. Don't try to calibrate to any unit at this point just measure the "raw" frequency from the sensor with a frequency counter, digital tachometer readout or similar. Ideally do a range of speeds and plot the results in a graph to see how linear it is. Ideally the graph should be a straight line.
|Thread: Barograph 'stiction'|
Swarf's comment on a buzzer is spot on. Many aircraft altimeters (basically aneroid barometers) have internal buzzers to overcome stiction. Altimeters have very good bearings but stiction is still an issue.
|Thread: METAL DUST & VFDs|
The medium specified in the IP5x test is talcum powder. This is non conductive. To test with anything else would not be compliant with the standard.
I have looked at several cheap VFD and their claims for compliance generally were dubious.
P.S. Part of my day job is witnessing compliance testing and reviewing other peoples tests. I also sit on a committee that defines a environmental test that includes dustproofness.
Edited By Robert Atkinson 2 on 04/05/2022 13:08:33
The IP 5x test uses nonconductive dust (talcum powder) so is not adequte to protect electrical equipmnt against conductive dust.
Yes you can get fully protected VFDs, at a cost. Most model engineers on here seem to use the cheap far eastern VFDs. On many of those wven the basic IP20 is dubious
Just a note, IP54 only provides protection against limited amounts of dust. It is not generally adequate for electronics in a machine shop.
Any VFD should be in an enclosure.
Would need data on VFD to be specific on size.
|Thread: Domestic Chemistry|
Mixing vinegar and bicarbonate of soda while visually impressive does not make a good cleaner. Try them on their own next time. Mixing them basically makes water and CO2 with possibly a tiny amount of sodium nitrate (lye) but it's insignificant.
|Thread: Determining/measuring sub-micron displacement|
How about a sine bar on a surface plate and slip gauges or a micrometer head? Effectively a leaver of known length. The probe on top surface just past the center of the low end roller and gages under the other end. Possibly put the low roller in a V block to stop it moving.
otherwise stick a mirror on it and set up a laser interferometer. Not as hard as it sounds. Needs a helium neon laser, couple of mirror a beam splitter (microscope slide cover slip) bit of ground glass and a magnifier to see and count the fringes.
|Thread: Liquid Plus Gas|
A 50:50 mix of acetone and automatic transmission fluid has a good reputation.
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