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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: wiring
15/06/2020 12:47:16

There are various versions of "SX2". For starters what motor type, brushed or brushless, does your mill have?

If you don't have athe skills to work it out for yourself, unless you can find someone who has fitted the exact same tacho to the exact same mill you would be better of using the hall and magnet supplied.

Robert G8RPI.

Thread: Generating force to cap beer bottle
14/06/2020 17:04:41

I missed Jed's post as it crossed with mine.
Windscreen wiper motors are reversible electrically but typicall the thrust bearings are only set up for one way running. This is not an issue if you were backing off after capping as ther is no load. However with a wiper motors crank output and a spring you don't have to reverse it, just let it run through a rotation on the parking switch. The spring beween wiper crank and capping lever will let it run pat after the cap is on and capping lever has stopped. The existing spring in the manual capper will lift the lever.
Get an older motor from a scrappy. Ask them which ones they arn't asked for. Those will be cheaper and reliable.

Robert G8RPI.

Thread: 3 Phase in a Model Engineers workshop
14/06/2020 09:11:06

If the isolator is tripping as you say " The isolator for the mill is a Telemecanique and is the one I used in Oxford. As it is the trip on this isolator that keeps tripping " and is the blue/grey bok on the wall (left side) I suspec that it is mis-wired. Many have a 240V coil and require a connection between one phase and neutral.

There are a few possibilities for mis-wiring. Common ones are:
Connecting coil beween phases insead of phase to neutral.
The phase the coil is connected to is not a true phase. This is less of a problem with the idler motor converter you have, but try connecting the contactor coil supply to a different phase. Note that the mis-wire could be in a number of locations.

There is also a posibility that the mill has failed electrically in storage. Possible causes are damp and rodent or insect activity. Do you have a multimeter and a insulation tester ("megger"? If so check the phase to pase resistance of the motor windings and phase to ground for motor and wiring.

Robert G8RPI.

p.s. I looked at Transwave's information on converters and was surprised how biased it was.

Thread: Generating force to cap beer bottle
13/06/2020 15:56:50

American "screw-top" beer bottlles are really "twist-off". They are still crown caps like traditional bottles and put on the same way. The difference is in the neck of the bottle.

Robert G8RPI.

13/06/2020 10:41:38

I'd go for off the shelf bottle cappping machine, windscreen wiper motor and a spring. Have a number of spring attachment points on the lever to change applied force.
You can even use the park switch on the motor to run a single cycle everytime you press a foot switch. Most will give a choice of speed too.

Robert G8RPI

Edited By Robert Atkinson 2 on 13/06/2020 10:42:31

Thread: Compressor inspection
10/06/2020 19:51:28

The 250 Bar/liter limit is not to do with how long it takes to empty, it's an energy limit. Less energy means less damage if it fails. Steam has no lower limit becaue of the additional heat energy and the possibility of superheated water being present which releases even more energy as it boils when the pressure is released. Google BLEVE (boling liquid expanding vapour explosion)

Robert G8RPI.

09/06/2020 22:12:45
Posted by mgnbuk on 09/06/2020 09:43:07:

Our compressed air installations at work have to be inspected annually - including a 50 litre Clarke portable compressor. There is a calculation - system volume x working pressure in Bar IIRC - and inspection is mandatory in a working environment if the calculation result exceeds a certain number. The 50 litre receiver 8 Bar Clarke compressor exceeded the number & had to be inspected.


Nigel B.

The regulations on pressure equipment at work apply when the product of pressure and volume exceeds 250 Bar Litres. So a 250litre receiver has to be inspected if it operates at more than 1 bar at 10 Bar (~150PSI) 25 litres an above have to be inspected.
There are a couple of notable exceptions, no test mandated below 1 Bar (gauge i.e differential to local ambient) regardless of volume and all steam equipment has to be inspected regardless of volume.

Robert G8RPI

Thread: How to glue plastics
07/06/2020 18:47:46

There is no point guessing what the plastic is you need to have a better idea. Looking at the photo I think Polyethylene is unlikely to be the material, it is too soft to make a ridid wheel lik the one shown. A couple of quick checks could be carried out on a sample (one of the remaining teeth would do). First is to try disolving it in an aggresive solvent like acetone (nail varnish remover if you don't have the pure kind). If it softens or dissolves it's unlikey to be PE, PVC or polypropylene and can for your application be glued with epoxy, just abrade the surfcae well.

If it does not dissolve try the tests here:

If the wheel runs on a shaft, whatever plastic it is, if you cut LH and RH grooves in the surface an epoxy would probably make a adequate mechanical joint regardless of surface adhesion. There is big surface area and the joint is in shear both of which are good for a bonded joint.

Robert G8RPI.

Thread: Knob required
04/06/2020 12:28:57

A picture and dimensions of the shaft it goes on would be useful. As Rod said, 1/4" is easy but a lot of industrial switches use odd shafts.

Robert G8RPI.

Thread: Single phase to 3 phase motor conversion.
04/06/2020 08:21:40
Posted by Rodney Markham on 03/06/2020 20:55:08:

Farnell part no. 2759872 is a 100uF 220vAC for £4.74 would that work?

Still confused that this is only in circuit when he Boost button is pressed



That capacitor is maginally rated on Voltage, 3 minutes on 220 V or 1 minute at 300V. UK mains is nearer 240V than 220V depending were you are. As Clive says they have very short life. Ideally the capacitor should be non polarised but these are larger and more expensive. The one you linked is effectiviely two 200uF polarised (electrolytic) capacitors conneted in series positive to negative.

A better choice wold be a film capacitor 100uF 450 V at £25

Better again would be two 60 uF 450 V at £17.50 each wired in parallel (more capacitiance, less current through each capacitior.

Best of allis wire for Delta, fit a VRD and weigh the transformer from the old converter in for scrap.

Robert G8RPI.

Edited By Robert Atkinson 2 on 04/06/2020 08:22:31

03/06/2020 18:42:02

Well that circuit applies 180 degrees to two phases (should be 120) and about 90 to the other. not an ideal situation.
The capacitor that reads in nF range is faulty. The 8uF are about right, tolerace is tpically +- 10% and normally under. Note that it's not just capacitance and basic voltage rating that matter when replacing. It must be rated for motor starting applications.

Robert G8RPI.

Thread: Surface Plate & Height Gauge recommendations
02/06/2020 13:15:36
Posted by Barrie Lever on 02/06/2020 12:39:26:


I keep looking for a CMM but no luck yet, will update if I am successful.


Work threw one in the skip last year - literally crying The Rennishaw touch probe was still attached but smashed up aginst the edge of the skip.

Thread: Arduino/Stepper Motor Dividing Head
02/06/2020 12:48:31

Part of the UI problem is related to the "Maker" approach to electronics where things are built from ready made modules like Arduinos, stepper drivers and serial LCD and switch modules. This makes it easy but limits variation and customisation. Unfortunatly it does not build understanding of the basic principals or skills. I've seen electronics magazine projects using breakout boards and screw terminals so you don't even have to solder.

The ME version would be making a loco from ready made bogies, boiler. cylinder and valve assemblies from different manufacturers. Better than nothing, but not good.

Robert G8RPI.

Thread: Soldering Iron
31/05/2020 16:20:59

What sort of "small jobs"?

If electical / electronic I'd recommend a temeperature controlled iron in the 30-50W power range.
My personal choice has been Weller for over 30 years. Always liked the TCP series where the temperature is set by a alloy pellet with the correct curie point at the end of the bit. I don't like the new two part tips though.

Problem is decent ones are expensive and a lot of the cheaper ones are cheap nd nasty.

Robert G8RPI.

Thread: Machine Tool Peripheral Hoists
31/05/2020 10:11:06

I do note that the standard SkyHook tool post mount has a dovetail to fit directly on a large quick change toolpost. It is the youtuber (Adam Booth) who has had it modified to go in the slot of the tool holder.. The Dovetail mount is probably OK on a big lathe, but the tool slot with two set screws is just not an acceptable design. There is just too much leaverage trying to roll it out. As a minimun an adjustable "foot" opposite the lug that goes in tool post to react rolling forces into the cross slide or mill bed woud be a worthwhile improvement.

Robert G8RPI

Thread: VFD speed control fault
29/05/2020 17:17:31

This is most likely to be a failed or failing electrolytic capacitior. Less likely is a resistor failure. I assume there is no circuit available for the internals of the VFD so a bit of detective work wil be required.
Before you do ANY work on the VFD, Uplug it and leave for a least 10 minutes before touching anything. Disconnect it completley before attempting to open it up. You will have trace the connections and components on the 10V terminal. Look for buldged or leaking electrolytic capacitors r verheated resistors.

You could use an external 10V supply but the failing supply could still be used internally. Worst case thi could result in an uncontrolled overspeed condition.

Where are you located?

Robert G8RPI.

Edited By Robert Atkinson 2 on 29/05/2020 17:17:47

Thread: Earthing Issue on new machine
29/05/2020 10:50:15

Hand held appliances with properly implemented Class 2 (double insulated) protection are safer than similar Class 1 (Earthed) appliances as an undetected insulation breakdown is less likely than an undetected earth conductor fault. A second breakdown of the basic insultion is required in either case to cause a hazardous condition.
For Class 2 items with exposed conductive parts like your drill there has to be a minimum amount of insulation between these and any live part. It is possible that your old drill was indeed a crossover product that incorporated the Class 2 levels of insulation but retained an earth connecton. A "belt and braces" approch.
Safest of all is the "110 Volt" (actually 55 V - 0 - 55 V) power tool system which give a maximum of 55 V to grorund and 110 V between terminals.

Robert G8RPI.

29/05/2020 08:14:20
Posted by Brian Morehen on 28/05/2020 17:59:20:

This is a interesting question , If your motor is not attached to you lathe IE Mounted as a seperate unit it is quite possible that the only connection to the lathe may be your drive belt, This willl not provide any earth connection very easy to over look? You can buy a Plug for 13amp socket which has its own built in protection together with a manual reset in the event of a power failure , If you are using 3 Phase then more important because off the extra voltage to get a Electrician to check and test with a Megger for a Insulation test of either 500 volt or 1000 volt , Your Life is worth more than this simple test .

Take Care and check your equipment is safe for all .

Once remeber asking someone where is your earth connection its that lead there in the bucket of earth.

Take care Bee M

If the lathe tool has NO electrical equipment, including switches, lights DRO's etc, mounted on it and the only connetion to the motor is an insulating belt there is no requirement for the Lathe to be earthed. It is still good practice though. It's the fault current path that matters. If the motor was mounted on the same metal stand as the lathe but not directly on the lathe then both the motor case AND the stand must be checked for earth continuity, but the lathe would not have to be. If bothe the motor and stand are earthed there is no series fault path to the lathe. In practice of course the lathe would almost certainly would also have some earth path to the stand due to it's mounting.
Plug top earth current protetive devices are usefull but a modern consumer unit "fuse box" with protection built in is best. A socket with built in RCD is better than a plug type. Exmples are

Note that there are two types of RCD socket, Active and Passive. You should use an Active type for machine tools etc as the trip on mains failure so act as an additional no-volt release preventing unexpected re-starting.

Passive types should be used for things like freezers that must re-start automatically.

Robert G8RPI.

Edited By Robert Atkinson 2 on 29/05/2020 08:14:45

29/05/2020 07:51:15

Hi Emgee,

1/ I knew what you ment, but "Class 1 PAT" is not clear.

2/ I sver said anything aout the supply (that does come under installation test) I described the means of connection. If the connecton to the supply has a plug it is considered "portable" as far asr PAT goes, if it hasn't got a plug it's fixed and PAT does not apply. Typically a physically fixed machine with plug would have longer times between inspections than something movable with a fixed connection rather than a plug (these are rare but not unknown).

28/05/2020 17:35:36

There is no such thing as a "Class 1 PAT" defined by regualtion. Indeed there is no such thing a defined PAT.

There are Class 1 APPLIANCES these are those with a protective earth.

Portable Appliance Testing is normally considered to cover any electrical applance which plugs in. This includes industrial plugs, not just 13A ones. Fixed equipment regarding electrical testing applies to the supply, not the mounting of the equipment. Thus a Mill that is bolted to the floor but has a CY cable and a Commando plug going ito the wall is "portable" but pistol drill wired to a switched fused outlet is not.

A 20A earth bond test on a piece of electronic equipment will NOT damage it unless the equipment is faulty or test is carried out incorrectly. I've done or witnessed dozens of these on "portable" equipment that contained lots of electronic including servo drives.

A insulation test on a piece of electronic equipment will not damage it as long as the equipment is not faulty and test is conducted properly including selection of appropriate test voltage. A "Hi-Pot" (high potential breakdown test) does have a good chance of damaging electronic equipment but they are not appropriate to routine in servce testing.

There is NO legal requirement to carry out PAT.

Robert G8RPI.

I said don't get me started on PAT angry 2 (especiallty not " PAT Testing" which is testing a test)


Edited By Robert Atkinson 2 on 28/05/2020 17:49:28

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