Member postings for Peter Cook 6

If you have access to a 3D printer, printing a pulley for temporary use works well. That said the "temporary" set I made for my Watchmakers lathe back gear is still in use some three years later!

For starters try downloading some stuff you find useful from Thingverse or one of the similar websites. You can at least try out the printer and make something. The learning curve for any 3D cad program is pretty steep if you have not used them before.

I personally use MoI 3D modelling, its far from free, but it is the one that I find most intuitive and quickest to use to knock up objects I want to print and as a design tool for things I want to make.

I don't have a mech eng/drawing office background, so I find the majority of the CAD programmes that use that paradigm don't fit my way of thinking. MoI does, although even that has a steep learning curve.

There are several free versions of CAD software ( MoI has a 3(?) month free trial). I would suggest downloading a few and trying them out - see which one works best for you.

Quick internet search found this

Residual current protection in variable-speed drives - CIRCUTOR

it's advertising, but suggests that the EMI filters in invertors feed small currents to earth in suppressing the high frequencies.

Sounds like individually the invertors don't have enough leakage to trip the RCD, but when on together the sum total is big enough to so do.

13tpi would be a very weird choice for a leadscrew. It would give 0.07692" per rev of the handle, requiring some heavy math for accurate cuts.

I would guess (as John H suggests) its metric and 2mm pitch - which is 12.7 tpi.

I bought a couple of IKEA "Helmer" drawer units. Bit like the Bisley ones, but a fair bit more affordable (£45 for a six drawer unit).

They are a bit flimsier than the proper Bisley ones, but were cheaper new than my local surplus place was asking for ex office ones.

The Post Office's Postcode finder Postcode Finder - Find an address | Royal Mail Group Ltd gives the nearest address as

74B North Street

Downend

BRISTOL

BS16 5SF

Andy, I bought one of these Brushed DC motors from this supplier a few years ago for use on my Taig lathe. There are some details of the installation here

Taig V2

The supplier is in the UK and a nice guy. He told me these are/were spares for a vibration plate they sell/sold but have never been needed. Mine came with a sophisticated PWM driver board ( and a remote control!) which he no longer seems to sell. I have tried mine with one of the controllers he now supplies, but the one I had ( not from him but looks identical) made the motor noisy - The controller has 100hz spikes on the output which the motor turned into noise.

With a decent controller it was a nice motor. Good torque down to about 400rpm. However it is fairly big and got in the way on the lathe - so I swapped it out for a brushless motor which is quite a bit shorted and lighter.

I would suspect that the growers/packers grade their pears into very tight weight categories, and then supply to the supermarkets based on specific requirements (size number, price). E.g. Waitrose sell Braeburn apples in two different packs. One contains five smaller apples, and one contains four larger ones.

It would be interesting to know the variance between the individual pears in Michael's pack.

Michael, I am not an expert but my understanding is that GSM mobiles (as part of the GSM standard) - when making an emergency call (112 or 999) are programmed to contact the nearest (strongest ?) cell tower (using 2G) without using network authentication, and such calls are routed by whichever tower the phone has contacted, to the nearest 999 handling centre.

You get the Emergency calls only message if the phone can contact a cell tower, but can't authenticate with your mobile operator. A mobile phone without a SIM card can still make such calls. If there is absolutely no coverage from any tower - you still can't contact the Emergency service.

My 2d's worth.

Bill, you can use a normal landline phone with your existing broadband, all you need is an ATA ( Analogue Phone Adapter) and a contract with a suitable VOIP provider. Although I have a conventional landline, I also have an ATA and contracts with a couple of PAYG VOIP outfits. I use it either when the landline is otherwise occupied, or the rare occasions I want to call abroad - the VOIP providers are VERY cheap.

Dave - I suspect you may be disappointed. My understanding of the BT plan for the switch off is that they will not be rolling out Fibre to the premises everywhere in the 2025 timescales. For places with decently fast FTTC, i.e. fibre to the cabinet and copper from there to the house, they will simply replace your router with one that has a built in ATA (as above), and ask you to plug the landline into the back of it. Then they will transition your number to the Digital Voice VOIP service.

Out here in the sticks (we do have decent FTTC), each time I discuss an upgrade with BT they say I will have to convert to digital voice as part of the deal through the above path. Several people in the village have done so and are (as far as I know) happy with the outcome.

The biggest downside is that unless you install a UPS, if the power goes out you loose the landline, although with the ubiquity of DECT phones these days - which die when the power goes -= I suspect most people don't really notice.

Very interesting Michael especially the calibration process - I must download the Arduino code and see what it does about the intertia of the motor.

I have been using a brushless geared motor like this

to drive the leadscrew on my little Taig lathe. It's 12v, 7watts, 60rpm rated at 15kg.cm of torque and about £25 from Ali express. The gearbox is 131.5:1 reduction. It has forward and reverse control, speed control via PWM input, and outputs 6 pulses per rev of the motor (787.5 pulses/rev of the output shaft) on a signal line - all at 5v logic levels.

It has worked very well, and my little Arduino controller used the pulses to measure leadscrew speed. Some time ago I decided to try and count the motor pulses as a way of determining carriage position with a view to implementing an auto stop. It worked OK, but I could not get the stop at a chosen zero. It consistently overshot (by up to 0.15mm) but repeatably so, and I assumed I had a code error.

It took a long time before the realisation dawned that there was enough inertial energy in the little rotor (@ 7000+ rpm) to drive the load of the carriage - through the gearbox and leadscrew for several ( up to 10) revolutions of the motor once the power was cut.

By computing and allowing for the overrun based on the speed of the motor, I can now get it to stop the carriage repeatably within 0.01mm.

Measure the pitch (distance between crests) over as many turns of the thread as you can. Simple division will give you a good idea. UNF at 1.058 mm pitch should be easily distinguished from the 1.25 of M8. but not M8 Fine which is almost the same.

The alternative is to screw the nut that came with it on as far as it will go. Measure the distance from the nut to the end of the thread. Unscrew the nut a few full turns, and measure the distance again. Math will again give you the pitch.

Edited By Peter Cook 6 on 18/08/2023 14:05:57

Could be 5/16 UNC or UNF. Spec diameter for both is is 7.938, so 7.79 would be understandable.

UNC is 18tpi 1.411mm pitch, UNF is 24tpi 1.058 mm pitch vs M8 Coarse at 20.3tpi (1.25mm) or Fine 24.5tpi 1mm pitch.

Given that several vendors sell the same motor with a drill chuck option, and 5/16-24 UNF is a standard drill chuck mount, that would be my best guess.

Correction of UNF pitch - M8 Fine might fit - both have 60 degree flank angles.

Edited By Peter Cook 6 on 18/08/2023 14:04:47

Nice example of the latter form here

Robert-Houdin Triple Mystery Clock - Jacques Nève (horloger.net)

And a typical example of the former.

Lot - A Mysterious Circulator Mystery Clock by E. Dent & Co. Ltd., London otherwise known as the Chronological Equilibrium, c.1975, (martelmaidesauctions.com)

Edited By Peter Cook 6 on 18/08/2023 11:18:08

How happy is the daughter - with the resulting dust and chips all over the dining table!

I find the Repair Shop a fascinating case study. I really enjoy the programme, but often wonder how many of the "treasured items" would get restored if the owners were faced with the commercial costs of doing so.

Dave W I think luxury car main agents labour rates are, in the main, over the top. But on the other hand they cover a lot of overheads. My Merc main dealer provides a "free" loan car while mine is being serviced - and I am happy to pay their inflated rates for the convenience and service offered.

Simon I must confess reason c) is my main motivator! however the. skills are lacking in many people. I know people locally who "call a man" when they want a picture hanging!

Edited By Peter Cook 6 on 10/08/2023 21:10:59

But isn't it our fault for expecting the best possible material lifestyle for the lowest possible cost.

How many people have price as the principle decision point when buying "stuff". So to sell the highest possible volume, the manufacturers build down to a price. So products are designed to be manufactured efficiently rather than designed to be repaired.

Add to that the labour costs of service engineers. I would be surprised if you got much change out of £60/hour once you add in the cost of the van/workshop, tools and business overheads (call centre, billing systems, the time consumed looking at jobs that don't materialise, and any return calls) and of course the VAT.

Put those two together and it becomes very difficult for the average person to justify paying for for or five hours labour to dismantle, repair and reassemble a gadget that can be replaced for <£500 but which then has higher efficiency and a warranty.

I fixed our old (25 year old Bosch) washer a couple of years ago. £50 of bearings and seals plus four or five hours work. Would I have had someone else do it at £60/hour plus parts i.e. £350. Another example is clock repair. These days if you want a mechanical clock fixed by someone competent it will cost you £300 for a simple time only clock and north of £1000 for a three train carriage clock. One reason I bought a lathe and started doing my own!

20+ years ago cheap stuff was poor quality. These days with modern CAM and robotic assembly the quality of even cheap is pretty good. So who is to blame "them" for doing away with heritage skills or us for not being willing to pay for them.

How many here buy their suits from Saville Row? Who would buy a new Myford rather than a Warco WM 290V at half the price. Who would go to a bespoke cabinet maker rather than IKEA.

If the market doesn't value and won't pay for something, it goes obsolete!

If you go this route be careful of the springs. I would suggest for a first attempt, if you can find a time only weight driven clock it would possibly be a better starting point.

I suspect the tensile strength of the filament will be the last thing to give way. The most likely issue you will face is delamination of the layers created during printing.

Careful design of the layer structure would help, e.g. if all the print layers were radial - but I don't know any way to get a slicer to do that. You may need to hand craft the code.

I have successfully made pulleys in PLA, but they were for low speed (<200 rpm ) use.

Sorry, me being a bit thick tonight.

I presume that the distance marked as 38mm on the jig is not the distance between centres of the two holes (which it is for the 30mm dimension), but is actually 38mm plus half the diameter of the dowel pin between centres.

If not then the first hole is going to be 38mm minus half the diameter of the pin and that would not correspond to the drawing?

Or am I missing something!