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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: Customs payment is it a scam
22/09/2020 16:09:49

The correct way to report this (in the UK) is to simply forward the email to

Action Fraud no longer take reports on attempted phishing. They are only intereted if you have acually lost money or goods.

Robert G8RPI.

Thread: Cheap Oil for hardening
22/09/2020 14:02:41

Fuel in engine oil is a real problem. A particular case is modern diesels with particulate filters (DPF) some designs (Fiat, GM) inject diesel on the exhaust stroke to regenerate the DPF and some washes down the bore into the fuel. This can give a noticable increase in oil level.
A cheap oil with minmal additives would be good. The oil volume compared to metal mass will affect the temper. So will the oil temperature. Pre-heating the oil with hot scrap is sometimes done for critial parts.

Thread: Interference
22/09/2020 13:34:46

It just goes to show you can't be sure about interference without measurement. Unless a VFD/inverter explictly states it has built in filters it will need external filters to bring emissions within limits.

Robert G8RPI.

Thread: Creating negative pressure in flue?
21/09/2020 17:12:37

I concur with Dave.

Put the heater outside and run the hot water inside. If it's an air heater stll put it outside but get a carbon monoxide alarm as well. A relative of mine died from CO due to a modification to a heater. Not the way I wanted to inherit his watch making tools.

Robert G8RPI.

Thread: Problems reading from a 3.5" floppy disc
20/09/2020 22:31:33

+1 for head cleaner. Another common issue is dried up lubricant on the helical "lead scew" that drives the head. A tiny drop of light oil can sort that out.

Robert G8RPI.

Thread: Sievert blowtorch - regulators and hose failure devices
19/09/2020 14:33:12

The 305401 is also known as the HF3. It does incorporate a pressure reduction device. The limitaion is that it is not adjustable or well regulated (1.5- 4 Bar ). The fact hat it hs a POL fitting tells you it is not intended to be used with a regulator as regulators do not have POL output connectors. Sievert do sell HFs with adjustable regulators.

The HF-3 is sae to use as is. Most uses do not need the additional control of a regulator.

Robert G8RPI.

Thread: Marking out blueing or pens?
17/09/2020 12:07:53


You mentioned "cold blue". This is totally different. it is used to produce the protective bluing of steel used on guns etc. While you could mark out through tthis I won't help with your problem because it won't work on oily material. And of course it only works on ferrous metals.


Robert G8RPI

Edited By Robert Atkinson 2 on 17/09/2020 12:11:34

Thread: Loc Tite
15/09/2020 19:03:05

You could go to the source

Thread: A new [to me ] style of scam eMail
15/09/2020 18:56:35

his sort of thing should be forwarded to the authorities at Even if you have seen it before every report helps the authorites build a picture of what is going on.

Just forward the email with any attachments.

More info at

Robert G8RPI.

Thread: Strength of Beams
12/09/2020 22:33:54

I'm a bit late to this but a couple of points

on "Computers" I highly recommend the Film "Hidden Figures" Even SWMBO liked it.

Boring bars also require torsional stiffness. I beams have poor torsional stiffness.

Elliptical and teardrop tubes are used on aircraft in place or round for aerodynamic reasons not structural

When I worked for a acttual aircraft manufacturer (Norman Aeroplane Company, sheet metal in one end of the factory, aircraft out the other) in the mid 80's they still calculated stress, strain and strength manually (with calculators). No finite element analysis like Nastran. The critical structures like wings were then tested to ultimate (failure). The boss, Desmond Norman, would be very unhappy if the caluulaed and actual ultimate loads were out by more than a few percent.

Robert G8RPI.

Thread: capacitance in long cables
11/09/2020 23:41:54

Connecting any modern electronics directly to long lengths of cable is asking for failures. There are lots of possible causes but in this case a change in the earthing arrangments, intentional or otherwise, caused by removing and re-insalling is a possibility.
Adding capacitors to the ends of the message line has some advantages but will slow down the maximum communication rate. Adding zeners (6.2 V 1.3 W on message and 16V 5W on 12V would be a good starting point) will give protection with minimum effect on communication. Really the system need to be desigined for the environment incluging ground loops and common mode voltages. The ideal solution would be isolted DC-DC coverters powering the Arduinos and optical isolation on the message line. Care would also have to taken with the lamp drivers.

Using 1k at each end is a little odd. Ideally the pull-up/down resistors should match the impedance of the cable probably 100-300 ohms. There should be just two, one at each end of the cable. is it a one transmitter multiple receiver setup or does each signal transmit and receive?

Robert G8RPI.

Thread: Transwave converter
09/09/2020 07:53:18

+1 for motor being wired delta instead of star (220-240V instead of 380-415V).

You can't harm anything by trying it wired for star so tht is the next step.

Robert G8RPI.

Thread: DIY Rotary Quadrature Encoder
07/09/2020 17:27:34

One important point with this class of sensor is that the field sensng is ratometric between the sensors, not absolute. This means that changes to he total magnetic field do not affect operation. The relative positions of the sensors is accurately defined as they are all on a single piece of silicon.

Robert G8RPI.

Thread: What plastic for a mower deck
05/09/2020 23:05:47

To line the inside of a mower deck I would use high density polyethelene aka HDPE. Some flexibility, good impact and cut resistance. It can be shaped with the application of moderate heat (hot air gun paint stripper). Eben better it is available in small to medium sheets at reasonable cost in the form of kitchen cutting boards. Attach with countersunk fasteners and sikaflex.


Robert G8RPI

Edited By Robert Atkinson 2 on 05/09/2020 23:06:28

Thread: How to move a Colchester Student ?
05/09/2020 18:16:59

Just be carerful and make sure there are no body parts between machine and immovable objects, including any crane or lift. Think what could break or go wrong in advance and plant where it will end up. If it start to topple or run away DON'T try to save it, step back and save yourself. If using an engine crane I'd want it to be rated for at least twice what I'm lifting. Whacht out for reduced rating with jib extended. Even the professonals make mistakes. A builders merchant delivering to a neighbour dropped a load of blocks from his HIAB onto SWMBO's Focus. At least no one was hurt.

Robert G8RPI

Thread: How to test dc motor or board?
04/09/2020 08:28:40
Posted by Gerard O'Toole on 03/09/2020 14:50:31:

Another thing I noticed, the fuse is on the neutral wire rather than the live. Surely this is not correct?

Again a photograph is here:-




The fuse should be in the LIVE connection. Puttting it in the neutral is unsafe for two reasons.
/1 Most importanly but not obvious, if the fuse fails or is removed, even without a fault, it leaves the machine "dead" but with ll the circuits up to the fuse still live and waiting to shock or electrocute someone investigating.

2/ it does not protect against a short to ground inside the machine. This means the internal wiring or components could overheat or catch fire as they may not be rated to take the (more than) 13A the plug fuse will supply.

You should re-wire the fuse to the positive supply. What brand is the machine? bought direct from China or UK seller?

Robert G8RPI.

Edited By Robert Atkinson 2 on 04/09/2020 08:29:07

Thread: Coping with voltage spikes
31/08/2020 20:52:53


Tim's original 3mm LEDs had 470 ohm reistors giving a 15% overload at 14.2V
The 560 ohms on page 7 came from a random ebay image.

Robert G8RPI.

31/08/2020 12:53:18


I had missed that the regulator was 14.2 V. 13.8V is the traditional nominal voltage for a 12V lead acid battery automotive system. 14.2V is actually a bit high for a vintage car with low electrical load and conventional (as opposed to newer long life or stop / start) battery. This is offset by less frequent use if the batery is not charged when the car is not in use.

That said, 14.2 V and 20 mA gives 550 ohms for a series resistor so the next higher standard value - 560 ohms (that I suggested as a minimum for 13.8 V) is fine for 14.2V as is my suggested 680 ohms.

We are not talking precision electronics here. The LED forward voltage varies with temperature and forward current never mind form device to device. The difference between 13.8 V and 14.2 is only 3%. I doubt the regulator is that good and standard low cost resistors are only 5%.
(I can do precision when required, voltage measurement to 7.5 digits)

Robert G8RPI.

30/08/2020 18:40:17

You should never connect a LED to a voltage source without a series resistor or other means to limit the current.

The voltagge on the datasheet is so you can calculate the correct resistor value and work out how many you can use in series with a given supply voltage. Resistor value is (supply voltage - LED voltage) / desire operaing current.

Fo your 3.2V leds, to operate from 13.8 V at 20 mA you get 10.6 / 0.02 = 530 ohms. The next highest standard value is 560 ohms. 680 ohms would b a safer choice for a car applicaion.

Your experiment confirms that you can change the charateristics of LEDs without destroying them completly.

The original failures were almost cetainly due to eceeding the LED ratings, not broken connections.

Robert G8RPI.

Thread: Help with lathe valuation - First post, be gentle!
22/08/2020 13:52:45

UK selling prices on ebay are around £450 with outliers of £180 (not working) and £680 (complete "starter kit"

They are £685 VAT and delivery

£400 woud meet your below true value .

Robert G8RPI


Edited By Robert Atkinson 2 on 22/08/2020 14:02:01

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