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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: Parvalux motor
04/07/2020 13:36:26
Posted by Ian Parkin on 04/07/2020 13:25:10:

Or this style

Personally I would not touch that with a barge pole (unless it was certified as insulating )

Clearly not compliant with regulations, it does not even have a part number. I would be concerned about it' safety.

Robert G8RPI.

04/07/2020 13:26:01

Most, if not all Parvalux "DC" motors are brushed "universal" motors. This means they will run fine on AC, You just need a 24 V transformer (a dual 12V will do too).
A SMPS is overkill and may not actually work depending on the size of the motor and the design of the SMPS. Many do not like the inrush current of a DC motor with a heavy load. I'm not sure how Ian determined a 5A requirement.

Robert G8RPI

Thread: ISO Container for Workshop
01/07/2020 19:39:34

Three comments
The proper military workshop and special purpose "containers" are built from scratch with insulated wall panels. Nice but can be expensive

You can get "one trip" used containers fairly cheaply as many countries export more than they import. I know if a plasterboard plant in Nevada re-opened and are shipping mot of their output to the far east at minimal costs s otherwise the ships would be in ballast.

If you get refriderated contaner the first thing to do is add at least some fixed ventillation as they are airtight to the point you could suffocate nd fumes etc can't escape.

Robert G8RPI.

Thread: Overview of fitting variable frequency drive (VFD) to a Myford ML7
30/06/2020 20:33:47

This is just based on review of the material on the Newton-Tesla website, but their ML7 Super7 prewired kits look quite good. They appear to have the inverter in a proper enclosure which is a safety requirement and not met by just buing an inverter, Chinese or otherwise. It also comes properly set up for the motor. Unless you are reasonbly skille with electrical systems I'd strongly recommend buying a pre-made unit like their AV750.
Manny home inverter installations are at best non-compliant with regulations or just plain dangerous, Even Newton Tesla' pre wired packages are not compliant unless they are properly installed in an enclosure with strain reliefs etc. An inverter, motor and box of bits from ebay may have a lower ticket price, but even aside from safety, the time spent selecting parts and buliding it up soon adds up. Even our non-work time costs, either in time taken from other aspects of the hobby or family and friends.

Robert G8RPI.

Thread: ISO Container for Workshop
30/06/2020 07:29:30

I second Bo'sun's Comments. Plain ISO containers will literally generate their own climate including "rain" from condensation. You need to at least line it with wood and preferably insulation. A 20ft or two will be easier to handle and be moore practical, The extra end wall area means you waste less space for accesses. Fully stuffing a 40ft or 2x20ft gives the same volume, but if you have to alllow access to the contents 2x20ft work a lot better.

Robert G8RPI.

Thread: Ultrasonics and citric acid
29/06/2020 20:05:20

Ed's suggeston is good and standard practice for cleaning small items in a ultrasonic cleaner. A glass laboratory beaker works well. Use hot water in the taank and cleaner, citric acid in this case in the beaker. Ideally float the beaker with a collar of closed cell foam. A thin (cheap) pressed stainless steel cat's food bowl works well too.

For non-ferrous alloys a dilute solution of ammonia with a drop of washng up liquid works well.

Robert G8RPI.

Thread: Stroboscopic effect
29/06/2020 12:40:15
Posted by Michael Gilligan on 29/06/2020 11:06:43:
Posted by Robert Atkinson 2 on 29/06/2020 10:58:59:

When I designed LED lighting for microscopes, I Used PWM control because of the efficency, but then filtered it to produce DC through the LED. Basically a switchmode current source with optical and current feedback.


Good approach, Robert yes

... but I’m sure you don’t need me to tell you that.


Thanks Michael,

It was part of this patent

But we kept some information back

Robert G8RPI.

29/06/2020 10:58:59

When I designed LED lighting for microscopes, I Used PWM control because of the efficency, but then filtered it to produce DC through the LED. Basically a switchmode current source with optical and current feedback. It was for quanttive fluoresence so hd to e controlled intensity. I've also used white LEDs as strobes, thay turn off slot faster than a conventional xenon flash lamp.

Robert G8RPI

29/06/2020 06:50:20

Going back on topic, I like others, would nor recommend using a stroboscope to "freeze" the lathe or workpiece.
On inadverent strobing, It is impossible to make generic statements about LED lights as there are too many variables in the electronics that drive them. If they are driven from DC with just a series resistor or analoge constant current source they are fine, but this is now uncommon as it is not efficent. running a lower powered 12V AC/DC MR16 lamps run from a prroper 12V DC supply (NOT a LED power supply unless you are sure it's smoothed DC output), you will probably avoid stroboscopic effects but you might get one that has electronic control rather thn simple resistors.

Robert G8RPI.

29/06/2020 06:26:01

Those Philips LED replacements arre NOT road legal,
The advert you linked to clearly shows the package with a cross through ECE R37 and a "not for use on public roads" warning. The listing also says they are not approved.
There are two interelated reasons for this, technical and apprpval. Technically, as you said, LEDs have competely different optical charatristics to a halogen filament. They are typiclly much larger area and each "chip" has at most a 170 degree emission cone, not the 360 sphere of a filament. The headlights optics are designed for halogen filaments not an LED. You can make a LED replacement that will produce an acceptable beam pattern for a particular lamp design, but it will not work in all lights. The Philips LEDs are probably very good and make an MOT passing beam in your car, but note the MOT just checks for gross alignment errors, not compliance with the full approval requirements.
That takes us to the regulatory part. All mandatory exterior lights on a car (except the reversing light) have to be E marked to show they meet the regulatory requirements. This includes the replaceable "bulbs" which have to meet exact specifications. There is NO specification for LED replacements. So even if you do build the perfect LED replacement the regulatons don't allow )it. Note that none of the cars with LED exerior lights have replacable "bulbs". The whole light is approved and you have to change the whole thing if it goes wrong (you can have up to 30% of individual leds fail before it's an MOT fail). You can get LED replacement sealled beam units as the are a complete lamp.

So basically your car is no longer road leagal. Did you tell your insurance company? If you have an accident they could refuse to pay out (they have to pay the 3rd party claim, but can recover it from you) if they notice. Even worse is if the other driver says you dazzled them.

Robert G8RPI.

Edited By Robert Atkinson 2 on 29/06/2020 06:36:31

Thread: Shaft Steel Material Selection
27/06/2020 14:22:48
Posted by John MC on 27/06/2020 11:49:26:
Posted by Robert Atkinson 2 on 27/06/2020 10:08:42:

John MC beat me to it, use 0.5" id 0,75 OD inner races:


Seems an expensive way of doing it, taper lock bushes. Slightly larger O/D bearings with inner races to suit. May need to bore the I/D of the inner race, tipped tools will manage that. Use inner races longer than the bearing so the oil seals have a hard surface to bear on.


Depends how you value your time and if ou are willing to irreversably modify the housing. Taper locks are not the only way to use a smaller shaft. new pulleys are an option.

27/06/2020 10:08:42

John MC beat me to it, use 0.5" id 0,75 OD inner races:

on a 0.5" shaft with 0.5" x 0.75" taper sleeve bushes on the pullerys e.g.

Loctite will hold the sleeves (ot turn down a 0.75" shaft to 0.5" at the ends) and you willl have room for proper seals so a semi-liquid geease e.g. CV joint grease can be used..

Robert G8RPI.

Thread: Inserted cross slide feed nuts
24/06/2020 10:21:25

The edge of the casting adjacent to the bush at the 10:00 to 11:00 position looks like it is proud of the surface like the start of a thread being pushed out. This might mean it is threaded. As this is a spare I'd suggest a semi-destructive investigation. If you have a mill start to cut away the end of the bush at it's thickest point. Use an end mill bigger than the thickness of the bush but less than half th diameter. It should be obvious if there is a thread as ou will hit cast iron. A drill or even slitting at an angle with a hacksaw blade (with the height reduced by grinding) would also do.
When removing by whatever method, applicatin of heat will help a lot. A paint stripping type hot air gun is a useful heat source and safer than an open flame.

Robert G8RPI.

Thread: Change to the Code of Conduct
23/06/2020 20:52:16

The Co-Op and the like will normally at least have a sample tested and act on reported issues. Additionally they will use supplies that meet their requirements for quality control etc and the items will have been tesed before leaving the manufacturer.
The issue in the particular case is that the item with the bad earth had a design / production fault so clearly adequate checks or QA had nott been carried out. Additionally there has been no mention of any recall or other recovery action.
The importer has to ensure the items they sell are safe, how the do that is up to them. If they want to trust the manufacturer that is up to them but they are responsible if it all goes wrong. For whatever reason (greed, ignorance and lazyness are common) some importers do not fulfil their obligations. It is then a game of chance, just hope it's not you or someone you know who looses.

There is a similar issue with other hobby magazines. This Months Radcom had a front cover picture and review of a piece of test equipment and funnily enough a shortform catalogue from one of th UK stockists.

Robert G8RPI.

23/06/2020 18:26:12

The thread about a pooryl earthed machine, suppled by UK dealer who advertises on the forum that was deleted also came to my mind. Davd mentioned it and Neil repled " The other thread was pulled as statements were made of dubious legality. For example it was stated as fact that a supplier was negligent because they didn't unbox and inspect every product before sale. "

Without going into the details of that case, it is irrefutably the case that an importer IS responsible for the safety of the items they import. They need to take adequate steps to insure that. Many importers do actually check every item or samples from each batch. In the particular case I was surprised that the suppler has not issued any recall on the product as the problem was clearly a design or manufacturing process issue, not a random failure.

Again in general terms, not specfic to that case, importers should remember that if a non -compliant product (for whatever reason), causes a death, the owners /senior management can face manslaughter charges. It is up to the courts to decide if relying on a foregin companies quality control and testing was reasonable (it obviously wasn't adequate or there would be no case).

What did happen to ARC adverts.

Robert G8RPI.

21/06/2020 11:08:01

As suspected that is the main power module. I expect that the capacitior failure is secondary to a failure of the power module.
The unit is probably beyond economic repair. The issue is that other parts have probably been damaged and there is a high probability that if you don't find and replace all of them the new parts you did fit will be destroyed first time you turn it on.

Robert G8RPI.

21/06/2020 09:30:07

As Joe says this type of failure of a ceramic capacitor is unusual. The capacitors are connected to the end pin of a 7 pin through hole component on the otherside of the circuit board. I suspect this is the main bridge output device, bot it could be a terminal block.
What is the component on the otherside of the board? Photo nd any part numbers would be useful.

Whay is the history of th fault? e.g bang during normal operation? overload? Bang on switch on?

It could be lighning surge damage, has anyther equipment failed?

Robert G8RPI.

Thread: Reciprocating mass instead of flywheel?
16/06/2020 13:11:24

That is still a flywheel, all be it a very out of balance one. It's rotating not reciprocating. Hopper has most of the story with the energy required. the big isse is that a recoprocating mas stops. I horizontal all the inertial energy is wasted stopping it again. If vetical there is only potenial energy which can only be recovered on the way down.

in either case nergy is only stored for hlf the stroke.

Any egnge with a crankshaft has a flywheel - the crank. They only need a extra flywheel if the crank isn't big enough.

Robert G8RPI

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.

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