Member postings for SillyOldDuffer

Welcome to the forum, Sean.

I built mine from this version.

Have fun!

Dave

If that's correct, installing 3-phase should be relatively easy. Problem is it's guesswork. Unfortunately only the supplier knows what work needs doing, and how much it will cost the customer. Possibly they are quoting high because they don't want the work - fair bit of bother for them, and very little profit in it when the customer is obviously only going to buy tiny amounts of power.

Supplier reluctance to provide 3-phase to low power users is one reason VFDs exist.

Why suppliers are reluctant or helpful is unknown; quotes vary wildly. I suspect it's down to how easy or difficult it is for the supplier, maybe plus external factors like how the cost of new infrastructure is shared between customers. Domestic single-phase installations might be subsidised by the government whilst 3-phase isn't. A single small customer in a remote location might be charged much more than a big customer on an industrial estate, simply because large consumers are a fast return compared with the little guy. Dunno.

Dave

The carbon-fibre rod I used had very good temperature performance even though it reacted strongly to humidity. My guess is the longitudinal carbon fibres fix the length, and it doesn't change much with temperature. However, the flexibility of the rod depends on the resin, which is sensitive to humidity. My rod was very thin and being used as a suspension spring with a lightweight bob, which likely exacerbated the humidity problem. Now I'm using a conventional pendulum, humidity has no effect, but temperature matters.

Dave

We've all assumed that Tony wants to print engineering objects,

And he isn't a fantasy fan:

Almost all 3D-CAD software will do the crank thingy. Not many CAD packages are strong on arty stuff, for which other software is better. Model railway layouts should be full of miniature figures, kiosks, seats, weighing-machines, clocks, lamps, and trolleys

The 3D driver of this engine needs re-printing - he and the locomotive are on different scales:

Dave

Who will make the glorious last post on the old forum?

Dave

Trouble with ignoring issues is they often matter! Easy to break an ankle in a rabbit hole!

Tony asked for the 'most user friendly CAD program'. First problem is all CAD programs are hard work - none of them are friendly. Second problem is what individuals find intuitive varies enormously, and we've no idea what Tony's mind-set or previous experience is. Previous experience in 2D draughtsmanship, or a different 3D CAD package can be killers because they require unlearning, which is extremely difficult. Expect learning CAD, any CAD, to be a significant challenge and persist.

I recommend choosing one and sticking with it. Switching is liable to confuse and muddle learning.

Dave

I'm suffering from first night nerves! Problem is a large number of bugs and functional issues were identified, and although believed fixed, circumstances conspired to prevent them being retested before launch.

The risk something important is still broken is higher than I care for, but I'm a nervous bunny. Fellow IT-professionals will know how Ass got into Assurance!

Option A: it will be alright on the night.

Option B: if it can go wrong it will.

Be OK provided members all sacrifice their first born...

Dave

Connecting 'steep' and 'curve' in terms of gradient hadn't occurred to me! I took it in the sense of 'this bill is a bit steep', meaning too much, or excessive.

As no-one knows how many words the English language has it's not surprising we don't know where they all came from, let alone agree on what they mean.

Anyone else noticed 'gotten' is creeping back into British English? Supplanted here a few hundred years by the simpler 'got', and apart from 'forgotten', abandoned by the mother tongue. Stayed current in North America though, and now we've gotten it back...

Dave

I've noticed 'twang' too. Likely it occurs in all pendula, but isn't noticed unless the apparatus can measure period at high-resolution.

I suspect many pendulum noise phenomena tend to cancel out over many beat. Noise only starts to become an issue when a clock keeps better than seconds, and is only obvious when microseconds are clocked.

I think the most likely cause of 'twang' is the rod flexing. An impulse applied at the top travels down a long lever to move the bob, which has inertia. The rod must bend, and I'd expect it to oscillate. Moving through air must also vibrate it slightly. Not much, but detectably.

If the rod was a violin string, what frequencies would it vibrate at? (Violin notes are far from pure - they twang too.)

Dave

The new dawn is imminent! Strap in and prepare for launch. Please read Darren's first post.

Dave

Famous last words!!!

A photo would be good.

Dave

Clogs has a complicated problem!

Easiest and best answer is to cough up and pay to have a proper three-phase supply installed. Apart from the cost! Quotes vary enormously. I believe it's because the customer is billed for any and all extra infrastructure needed. Lucky folk are connected to a handy pole outside their front door for a few hundreds. Others trigger requirements for lots of new cabling, trenches dug across busy main roads, poles erected, and maybe a few transformers have to be upgraded too.

Big digital converters capable of running a mix of 'n' different machines exist, but not cheap. They're aimed at industrial users not hobbyists. Maybe prices have dropped and someone has experience?

One per machine VFDs are small, simple, cheap, and efficient but fitting 10 of them is a big job. Could be the right answer though.

The obvious answer is a rotary converter big enough to manage the largest machine. Not grossly expensive to buy, but take up a lot of space, and are noisy and inefficient. Drawing big power from a rotary for any length of time soon makes the alternatives look attractive. However rotary inefficiency may not be a problem for occasional hobby use, and they do what they do without fuss.

A big static converter might be OK too. I don't care for them because the phases aren't equally spaced, so some motors won't run, whilst others only perform after the switches are fiddled with. Whether all 10 motors in a workshop will run off a static converter without shenanigans is a risk. They're also inefficient and capacitors don't last forever! Cheap and cheerful: if a static does the job, you've won.

Dave

I vote metric too.

BA might be more aesthetically pleasing because the heads and nuts are a little smaller, but apart from that go for cheapness and high-availability. In the most of the world that means metric.

Dave

Would have commented at the time except I missed this interesting post. I'm fretting about barometric pressure because it's almost certain my approach to compensating for pressure change is wrong. Long story and I'm still working on it, but I was educated by this description found on physics.stackexchange:

• Atmospheric pressure : The effect of the surrounding air on a moving pendulum is complex and requires fluid mechanics to calculate precisely, but for most purposes its influence on the period can be accounted for by three effects.

By Archimedes' principle the effective weight of the bob is reduced by the buoyancy of the air it displaces, while the mass (inertia) remains the same, reducing the pendulum's acceleration during its swing and increasing the period. This depends on the air pressure and the density of the pendulum, but not its shape.

The pendulum carries an amount of air with it as it swings, and the mass of this air increases the inertia of the pendulum, again reducing the acceleration and increasing the period. This depends on both its density and shape.

Viscous air resistance slows the pendulum's velocity. This has a negligible effect on the period, but dissipates energy, reducing the amplitude. This reduces the pendulum's Q factor, requiring a stronger drive force from the clock's mechanism to keep it moving, which causes increased disturbance to the period.

I'd assumed a simple linear relationship when it's complicated and non-linear! No wonder my clock doesn't work as intended.

I haven't quite given up on compensating mathematically for changing air pressure, but running the pendulum in a vacuum is the easiest way of fixing the problem. My mind goes blank when I tackle the maths, and I'm already struggling with a paper John Haine sent me!

Dave

Dave

Depends on where you live. Not many near me in Somerset.

Worse, I've never found one prepared to sell off-cuts, let alone give metal away! I put it down to improved business efficiency and the high value of scrap. No harm in asking though.

Scrapyards were friendly places in my youth and it was normal to scavenge and make offers for car parts and other goodies. Not now - KEEP OUT signs, razor wire, and angry dogs. None of my local scrappies sell anything to the public. Might just be me, but I suspect model engineers who can get hold of cheap scrap metal are probably a minority?

Dave

Edited By SillyOldDuffer on 30/09/2023 13:15:56

Good advice is to buy the biggest lathe you can accommodate! Big lathes can do small work, but small lathes can't do big work.

Second-hand versus new boils down to your personal appetite for risk. Condition is king when buying second-hand - it is far more important than make or model. A worn out Dean Smith and Grace stored outside for 5 years and then dropped is no longer a DSG - it's scrap! So I would want to see a second-hand lathe cut metal before buying one, and understand what's needed to move and instal it. Also not smart to buy a second-hand imperial lathe for a metric-only workshop!

The advantage of buying new from a UK supplier is consumer protection applies, which protects your wallet in the event a lemon arrives, and the thing is delivered to your door by the seller.

New, I think, is better for inexperienced purchasers who want to plug in and go. Second-hand is better for experienced purchasers or those ready to deal with historical problems : not all second-hand equipment is 'pre-loved'. A booby trap with ex industrial equipment is the cost of spares. The lathes are sold cheap because CNC made them redundant; but spares are still full-price. Eye-watering! That said, CNC caused many ex-industrial and educational machines to be dumped in good condition - much better than hobbyists could afford in yesteryear.

Dave

Edited By SillyOldDuffer on 30/09/2023 10:27:19

Mine was entirely made from 5" x ¼" Aluminium flat bar - base, top and flywheel. I found plate easier to slice to size than round bar - 5" round stock is too big for my band-saw and challenging to part off on the lathe.

An electric jigsaw cuts ¼" Aluminium no bother, and it could have been hand sawn. I sawed squares, converted them to octagons, and rounded off on the lathe. The base-plate was superglued to a mandrel, but top plate and flywheel can both be gripped through centre holes. The spokes were milled - easy with a rotary table.

Bought some Brass a few months ago and still haven't got over the shock! Ouch.

Aluminium is considerably cheaper than Brass and my engine runs well with an Aluminium flywheel. I've an idea the plan specifies Aluminium. Could be because the engine's power output is extremely low and a Brass flywheel might be too heavy for it.

Dave

Hate to recommend anything without seeing the motor, but my guess is the housing and shaft are held firmly together by the bearing: These are often a tough press-fit onto both shaft and housing.

I'd make or perhaps buy something like a harmonic balance puller, the example below being about £15 from Machine Mart:

The bolts go through the spider into the 4 holes in the motor case near the bearing. Then the black bolt is tightened against the end of the shaft. Tightening puts an enormous pull on the housing and it and/or the bearing should shift.

I take no responsibility if the motor breaks! As this is tough love the bearing may have to be replaced. A press or large dead-blow hammer may be needed to refit it.

Might be cheaper and easier just to replace the motor. Symptoms suggest the centrifugal switch is malfunctioning, which could be anything between an easy fix or a hopeless search for an unobtainium spare part/ At minimum I'd assume it will cost new bearings.

Dave

Well, fellow humans, did we watch the nine towels example carefully and then engage brain. Or did we jump to the conclusion that ChatGPT was wrong, because 'obviously' an AI must be more stupid than us?

I suggest that ChatIPT gives the correct answer for the correct reason. It does not assume, as might a foolish human, that a washing line must be capable of supporting 9 towels at the same time. The length of the line is not specified: all that is known for sure is that the line will take 3 towels. Assuming otherwise is unjustified.

This is my sock drier:

If this drier takes 2 hours to dry 18 socks, then how long does it take to dry 54? The answer is 6 hours, as ChatGPT said. Note the red towel behind: the line it's hung from isn't long enough for 9 of them.

Of course, a really smart human will have noticed my drier only holds 17 socks because one of the pegs is missing. So it will take 8 hours to dry 54 socks.

We live in interesting times! Not intelligent to dismiss ChatGPT and Co. because they're not instantly superior today. Worry about how smart AI will in 30 years time, when most of us will be very stupid indeed; that is dead.

Dave

Edited By SillyOldDuffer on 27/09/2023 11:02:38

Good question.

I think this is a case of asking too much of the mill and cutters. Maybe also the Aluminium is soft and gummy, tearing rather than cutting, causing the motor to work extra hard.

Hole-saws are best for thinnish sheet metal rather than going deep, because swarf builds up in the slot, and having to drive lots of teeth puts a heavy demand on the motor.

Taking the cut slowly (lowish feed-rate) with plenty of paraffin or WD-40 and frequently stopping to clear swarf might help. About 500 rpm by my rule of thumb, but experiment with faster and slower. The mill's motor probably delivers more power and torque at higher rpm, but what suits the motor may not suit the saw.

So I'd change technique. Instead of trying to saw a large hole in one go, I'd twist-drill as big as I can - 13mm because I'm too mean to buy a Blacksmith's Drill.

Then bore the 15mm hole out to whatever size is needed with a boring bar. For this a boring head is needed:

Though they cost a few bob, boring heads are a valuable accessory. Boring does both deep and wide holes. As there's only one cutter, which can be adjusted to take very find cuts, it doesn't overload the motor. The holes are also considerably more accurate and straighter than anything done with drill or hole-saw. Main disadvantage is the time taken. If you want to make big holes quickly, a large powerful machine is needed to drive the cutter. Otherwise we have to slow down!

Jason's method is a good compromise: chain drilling lots of small holes removes metal quickly and then the boring bar only has to tidy up, which doesn't take long. The mill works inside it's comfort zone throughout, and swarf collecting and mincing in the slot isn't a problem.

Dave