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Member postings for SillyOldDuffer

Here is a list of all the postings SillyOldDuffer has made in our forums. Click on a thread name to jump to the thread.

Thread: Interesting??
20/05/2019 21:07:05
Posted by Phil Whitley on 20/05/2019 20:07:54:

The steam engine was invented , built and used in many forms without any knowledge of thermodynamics, in fact the science of thermodynamics was based on the study of working steam engines. The electric motor was invented by Michael Faraday, who was a well trained book binder who was employed by Sir Humphry Davy to write up and bind his notes. Science and scientists have a very poor record of invention of anything in common use today. It is the people who constantly test the laws of physics and experiment that make the breakthroughs, those who stick within the orthodxy of science discover nothing.

A very unfair criticism of science because the goal of science is understanding, not inventing! It's other people, like engineers, who exploit scientific understanding by inventing new things or improving old ones.

Dave

Thread: stamford show vandals
20/05/2019 20:32:45
Posted by Mikelkie on 20/05/2019 19:10:24:
Posted by Harry Wilkes on 19/05/2019 15:25:46:.
...

... in my opinion the problem lies with the human rights bullshit, ...

Specifically which of the Articles of the Universal Declaration of Human Rights do you object to? They seem harmless enough to me.

Inverting a few articles might give a better sense of what they're about, for example:

  • No one has the right to life, liberty and security of person.
  • Everyone shall be held in slavery or servitude; slavery and the slave trade shall be allowed in all their forms.
  • Everyone shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment.

No doubt Human Rights are imperfect but I submit we are better off with them than without.

Dave

Thread: Loco hand pump casting from Reeves
20/05/2019 18:59:43
Posted by Richard brown 1 on 20/05/2019 18:28:15:

Dave

That's thinking outside the box, well my one anyway. It never occurred to me that they could be like this.

Shame its not just one pump though obviously twice the work.

Thanks for taking the time to draw this up.

Have you shot any more machines yet?wink

Rich

Nurse has ordered me to stop shooting machines. Apparently it's very naughty.

You wouldn't have to fit both pumps I suppose? I guess the Black 5 is a big engine and Reeves recommend two pumps to make sure you can get enough water into it in an emergency. I see from their website that some engines get one pump casting while others get two. Interesting that NealeB's engine only got one casting - maybe you've got the souped up version!

Hats off to both of you. I don't have the skills or the patience to build a engine, much though I see the attraction. Must be fantastic to drive a loco you built yourself.

Dave

Thread: Larger VFD/Motors
20/05/2019 18:44:54
Posted by Mike Poole on 20/05/2019 18:09:29:

It would be interesting to see how the charging waveform alters with the output frequency for the load

Mike

Wish you'd suggested that earlier Mike - I need another current transformer to test VFD output frequency as well as input current. Never occurred to me to buy two.

Although I'm sure I've looked at the VFD output waveform before. Can't remember how I did it - certainly not a direct connection. As I recall each phase looks roughly like 50Hz overall but the sinusoid is built up from hundreds of fast pulses about 10kHz - I'm sure I wrote it down, but where's the notebook?

Dave

20/05/2019 18:32:55
Posted by Carl Farrington on 20/05/2019 16:04:56:

Hmm. Very interesting - great work Dave.

What are your thoughts on not using a fuse at all though, and using a 25A Type-B MCB instead?

I don't know Carl, what I've done is mix owning an oscilloscope with basic electric theory. Being old fashioned I know a bit about fuses, but correct use of Circuit Breakers for this purpose takes me out of my depth. I'm pretty confident about fuses because they respond to heat. But I've no idea what effect that spiky waveform would have on the working of a circuit breaker. They could be ideally suited or the pulses might confuse them. Perhaps a real electrician can explain what the grown-ups do?

If it were me, being financially challenged, I wouldn't use the recommended fast blow fuse because of the cost. Instead I'd use an ordinary 13A fuse (safe and legal) and accept it might need to be replaced every so often. I think I can tell the difference between a fuse that pops infrequently for an expected reason, and a fuse that goes bang due to a fault.

Dave

Thread: Loco hand pump casting from Reeves
20/05/2019 18:09:00

Reckon it means mount the pumps back to back:

pumps.jpg

The spacers are used to fit the connecting links (oops called it coupler in my drawing) into the slot cut in the other piston, necessary because there's only one rod to take the pump handle. Moving the pump handle backwards and forwards would cause one pump to blow while the other sucked.

Presumably fitted in the tender.

Dave

Thread: Larger VFD/Motors
20/05/2019 16:00:02

Connected my lathe to the oscilloscope with somewhat unexpected results.

Firstly, there is only a short spike at power on, VFD only, the motor is switched off. startspike.jpg

The spike is about 19A but it is very short. The current waveform immediately becomes a sine wave for several cycles over which the current gradually falls. Then short peaks, of about 0.6A, appear at the top of each cycle, although the waveform remains sinusoidal.

vfdonly.jpg

Switching the motor on makes the current peaks much larger. This is the motor running at 2500 rpm, with change gears, gearbox and drive shaft engaged, but the motor is otherwise unloaded.

vfdmotor.jpg

This view show the current waveform to be dominated by sharp spikes, of about 9.6A each, and lasting about 2.4mS. As 50Hz UK mains takes 20mS to deliver a full cycle, the VFD only takes cuurent for about 10% of the available time. Presumably this is recharging the capacitors.

My VFD takes most current in sharp bursts at supply voltage peak. It does not spread demand for power across the supply waveform, nor does it soften the blow with any zero-crossing cleverness. The fuse is subjected to current spikes, not a gentle rise and fall. With the motor at 2500rpm the average current (measured with a wattmeter) is 3.1A but it is actually drawn from the mains in 9.6A pulses

Unfortunately I can't cut metal with the lathe and work the oscilloscope at the same time to see what a heavy load does to the current. Do the pulses get bigger or longer in duration or both? Don't know.

However, from the point of view of the 13A fuse:

  • It has to survive a 19A pulse when the lathe is switched on.
  • The fuse is subjected to a pulse load, not one smoothly proportional to mains voltage.
  • When the lathe is consuming 3.1A on average it is actually taking power in 9.6A slices of about 2.4mS
  • Unproven but, if the 3:1 peak to average is maintained, then the 6A average needed to drive a 1.5kW motor, is peaking at over 18A twice per cycle.
  • Although the 13A fuse doesn't blow because it has time to cool, it must be stressed by this duty.

Going back to the original question, a 20A fast blow fuse looks like a better choice for 18A peaks than an ordinary 13A fuse. Although the 13A fuse might fail relatively early due to this mistreatment, it's not unsafe or unreliable. But pulse stressing an ordinary 13A fuse would be more problematical with a bigger motor, say 2.5kW: I think that's why the makers recommend high amperage fast blow fuses - a more appropriate balance of safety and reliability given all those sharp spikes.

My VFD is inexpensive. I suppose better electronics in a more sophisticated unit might load the mains less aggressively.

Dave

Thread: stamford show vandals
20/05/2019 14:33:54

Is it possible those in favour of severe punishments have more in common with these youths than they might care to admit? Bunch of stupid lads cause pain by wrecking an exhibition, and we have grown-up forum members wanting to inflict: a fall down stairs, the stocks, 100 lashes, castration, being not allowed to live, bread and water, being whipped with red-hot barbed wire, the birch, and denial of Human Rights. (Human Rights protect citizens from the State; think disappearances, torture, arrest without trial and genocide. They are not to be dismissed lightly.)

I'd be all for brutal punishments if they worked. But they don't. Apparently Stalin had about 70 officials shot after a railway accident. Well they won't do that again.

Part of the problem with lashing out is it ignores motive, which includes the possibility of mental illness. National Audit Office report on British prisons:

'Rates of self-inflicted deaths and self-harm in prison have risen significantly in the last five years, suggesting that mental health and well-being in prison has declined. Self-harm rose by 73% between 2012 and 2016. In 2016 there were 40,161 incidents of self-harm in prisons, the equivalent of one incident for every two prisoners. While in 2016 there were 120 self-inflicted deaths in prison, almost twice the number in 2012, and the highest year on record. Government needs to address the rising rates of suicide and self harm in prisons as a matter of urgency.

In 2016, the Prisons and Probation Ombudsman found that 70% of prisoners who had committed suicide between 2012 and 2014 had mental health needs.'

It is a fantasy that Prison is an easy ride. They do allow criminals to network and exchange skills.

Only severe punishment will correct the distorted mindset of draconian forum members. You are all sentenced to read nothing but the Guardian for one year and strictly forbidden to read the Daily Mail ever again...

To be clear, I have no sympathy with the perpetrators. I don't know anything about them. It's the job of the courts to assess the facts and decide their future, not inflamed public opinion.

Dave

Thread: HSS or CS taps and dies
20/05/2019 13:42:46

The main benefit of HSS over CS is that it retains its edge almost up to red-heat. Thus HSS makes it possible to cut metal fast hot with a powerful machine. You can get equally good results out of CS by keeping it cool, and it's especially good for hand tools. But another advantage of HSS is that it's tougher - less brittle - than Carbon Steel, and should last longer in a busy workshop.

As you've found not all steels are equal. I've found very cheap taps and dies work well on soft metals like aluminium or dead mild steel. When sharp they do OK on brass, but they are easily blunted by mild steel or indeed any hint of heavy work. They tend to snap like carrots if you don't cut absolutely straight.

With one exception, I've had reasonable service out of moderately priced rather than very cheap sets. My requirements being genteel, I mostly use CS taps and dies, buying replacements from Tracy Tool's inexpensive range. Probably HSS isn't worth the extra cost for me because I don't do much threading and I avoid work hardening metals like bronze, stainless steel and unknown scrap. I usually make sure rods are a shade below theoretical diameter, and drill tapping holes slightly too big: this reduces the strain on taps and dies considerably without making threads significantly weaker.

Not been disappointed with anything from Tracy Tools, but there's a reason high-end taps and dies are eye-wateringly expensive.

Are you the type who likes tools to last forever? I tend to see them as disposable, which isn't to everyone's taste!

Dave

Thread: Antique Steam Engine from Doorknob
20/05/2019 11:54:39

Now there's no evidence of a coaxial crank I've gone off the idea in favour of this suggestion:

eccentricpos.jpg

The missing 'needle eccentric' connected via the notch and behind the crank to a lever mounted in that mysterious hole.

The needle might have been ornamental, adding to the interest of the engine with more movement. Inside the engine is a dual valve that controls when steam is admitted to push the piston whilst at the same time allowing the other side to exhaust. The engine won't run without a properly timed valve. If the engine runs without the needle, the real valve gear must be inside. Might be helpful - an ornamental needle waggling a fake lever is easily replaced.

I'd be very wary of stripping it down. I wonder is a friendly vet would x-ray it for you?

Difficult to value, it's an attractive antique with engine collector appeal. I've seen much more basic model engines with £800 price tags.

Given what you've found about Richard Westerman, I think he made this item for display in his shop and at exhibitions. It shows he was skilled, imaginative and capable of attractive work in miniature. That chuffing away would have made him more interesting and memorable than other clock-makers - good advertising.

Dave

Thread: Steam Engine Number One
20/05/2019 09:44:19

I hesitate to offer advice Iain because you and I might as well be twins. I think soldering is one of those jobs were everything has to line up just so.

The purpose of flux is to prevent the base metal from oxidising. It mainly contains a chemical that reacts with the oxide, but also makes a temporary layer to keep air out, and it helps transfer heat into the joint. All these effects are time-limited, and any dirt is bad news.

You might be taking too long heating the job up to solder temperature - by the time the job is hot enough, the flux has absorbed all the oxygen it can, and is leaking air. The surface oxidises just before you apply the solder and spoils the joint.

With my smallish torch I've found it helpful to contain the heat better by adding a side and partial roof to the hearth. With an open hearth, as shown in your photos, a lot of heat escapes. I think a big torch makes it much easier to get joints to temperature simply because it has the oompph necessary to work quickly even when the hearth leaks heat badly.

I suspect my other issue is generally poking about and dithering whilst waiting to misjudge the temperature. Watching a chap at an exhibition, I was struck by the smooth speed at which he worked - perhaps three times faster than me, and far more confident.

Dave

Thread: Hobbymat MD200
19/05/2019 22:35:22
Posted by Haggerleases on 19/05/2019 20:53:56:

Hmm. Lacking a dedicated workshop (rented house) I can imagine hefting the thing around a fair bit, so it would need to be portable. Perhaps I'd be better with a smaller machine for the time being, doing smaller projects, and upgrade to a bigger machine and the much wanted locomotive later on. I have a lot to learn anyway before destroying pricey castings...

It seems they don't make the size of lathe I'm after. The ability to machine castings is vital to most of the projects I have in mind. Then again, I like clocks too....

Part of the attraction is the machine itself, the tool being the thing, that's why I'm attracted to the older machinery. The Chinese gear is very functional, but not at all beautiful (to me).

I don't want to rush the purchase, but then again I'm keen to get started.

A mini-lathe is an easy two-person lift and the maximum I would move without mechanical help. I'm on the weedy side and well past my best-before date. A fit or younger man could manage on his own and the lathes are light enough to plonk on an average table. They don't need to be bolted down, and are fairly quiet.

I regret the amount of time I dithered before buying a lathe. I wish I'd just bought a mini-lathe rather than dancing around the Chinese vs second-hand debate. Condition is everything with second-hand lathes unless you want a doer-upper and at the time I didn't have the skills needed to tell good from bad. Now I know more, I'd give an older lathe a careful inspection and want to see it cutting metal before buying it.

Back in the day buying a lathe was often a lifetime purchase. I don't see my workshop that way; all my tools are disposable. Not everyone is comfortable with that and I respect their reasons. Horses for courses.

Enjoy,

Dave

Thread: Electrics for a battery locomotive
19/05/2019 21:50:23
Posted by Tim Ellis on 19/05/2019 18:14:45:

Hi Dave,

Many thanks for the reply, I'll look into this tonight. Can I ask how you calculated the right fuse? Its just I'll probably build a second in time and would like to understand every little aspect.

Many thanks, Tim

Hi Tim,

It's from the equation Watts = Volts x Amps

Thus:

Amps = Watts divided by Volts

The specification of the TE952 says it can dissipate 250W and you have a 12V, battery so

Amps = 250 /12, rounded down to the nearest standard size = 20A.

I suggested 30A if you're brave because the TE952 can certainly withstand short bursts of higher current, so rounding up to 30A isn't foolhardy. An accidentally shorted battery could deliver several hundred amps - enough to melt the wires - so you want to size the fuse to deal with normal operation, about 20 to 30A, and to pop quickly if more than that is drawn due to a fault.

sadcastings website doesn't give any clues about the motor ratings, bit anti-social possibly it's tucked away on the plans! But judging from the price and photos, 10 amps each looks reasonable, and 20A total would be compatible with the controller.

Dave

Thread: Hobbymat MD200
19/05/2019 20:19:49
Posted by Haggerleases on 19/05/2019 19:12:27:

The Hobbymat looks a nice bit of kit, but the mini lathes seem to win every time on specs. Hmmm it's not easy making that first plunge.

Nothing wrong with the Hobbymat for what it is, though a serious enthusiast might go up-market with a Cowells. The Cowell's is a very nice machine indeed, but based on what you've said you're interested in, it's too small. Andy mentions his WM180, whist not better made or more accurate than a mini-lathe, it is bigger. Difficult to describe why larger lathes make life easier, but they do! And sooner or later you will probably want to cut threads.

I learned a lot from my mini-lathe and don't regret buying it. It got me hooked and I had loads of fun with it. But now I have a bigger machine I'd not go back...

Dave

Thread: The Chocolate Fireguard as designed by Mercedes Benz
19/05/2019 20:01:59

The switch to electric might have advantages. At the moment we all have to report to a garage forecourt to buy carefully metered fuel stored expensively underground in tanks that have to be regularly replaced, and refilled by fleets of tankers that expensively trundle around the roads getting in my way, going on strike, or getting stuck in snow. Not to mention crude being bought from some distinctly dodgy countries and then shipped half-way round the world. The garage, taking up rather a lot of expensive land, has to be manned for safety reasons and make a profit.

To buy diesel and petrol the customer has to make special trips to the pumps and pay a lot of overheads. Electric recharging does away with several inconveniences. Recharge points can be scattered more or less anywhere convenient, they don't have to be clustered together. They don't need to be supervised, and they don't need to be refilled. You can even refuel at home. And because it doesn't burn fuel, your car won't need to be docked regulartly to have its oil, plugs and filters changed.

Apart from the batteries...

Dave

Thread: Thread Pitch Info.
19/05/2019 19:20:25

Hmm,

  1. Chronos sell Morse Taper Chuck Adaptors for Rotary Tables 3 MT with With Boxford Thread (1 1/2 x 8 TPI) suitable for Vertex and Soba tables.
  2. lathes.co.uk's Boxford entry includes: 'The main dimensions of the original South Bend spindle, with its 1.5" x 8 t.p.i. nose, were unchanged, and indeed stayed the same on the ordinary V-belt drive Boxfords until the end of production. An interesting note in the Company's records states that: From Serial 1360 all machines have an 8 t.p.i. Whitworth form spindle nose - a reference to the fact that the first batch must have had an exact copy of the South Bend fitting with its American 60° thread angle (the Whitworth is 55°.

So Alan might have an attachment to fit the South Bend 60° thread, or the similar 55° Whitworth. How confusing!

Occurs to me the quickest solution might be to replace the MT3 Boxford adaptor currently in the Vertex with an off-the-shelf MT3 ER32 collet chuck. Not, of course, if Alan is using this as a learning opportunity! Why is nothing ever simple?

Dave

Thread: Hobbymat MD200
19/05/2019 18:00:16

Um, not sure the Hobbymat is a good choice for loco building. It lacks screw-cutting, and as you've spotted, has a high minimum spindle speed. It also has a small motor (120W) and only weighs 24kg. Compare with a mini-lathe which will have a 400 to 600W motor and weigh about 40kg.

The HobbyMat looks to be good for small railway modelling / clock making type fine work - anything where the small size and high spindle speeds are an advantage. Whatever it's other virtues, like that desirable 'very quiet running' I think it's too small for you.

Best advice I ever got on the forum: buy the biggest lathe you can manage. The exception is when you only do tiny turning.

Dave

Thread: Electrics for a battery locomotive
19/05/2019 17:37:39

Do you know what the motor ratings are Tim?

The controller is rated for 250 Watts at 12V, so it would be protected by a 20A fuse or circuit breaker like this example. 30A would be OK if you are a little braver. But if the motors are rated less than 125 Watts each, then the fuse or breaker should be reduced to Total Motor Watts divided by 12.

Dave

Thread: Thread Pitch Info.
19/05/2019 16:14:02

Confirm my 20th edition agrees with Jeff's 1.3647" which is a smaller hole than the German 35.1mm ( 1.382" ).

This is probably due to a different view about how tight the fit should be. Matching internal and external threads made to exactly the same dimensions would be impractically tight, prone to jam, and made worse by tiny manufacturing errors or dirt. Thread specifications allow for this, which is why the internal and external dimensions of threads don't quite match.

If the internal thread hole is bored a little oversize accidentally or deliberately, the two parts will screw together more easily, less metal is cut, but the join will be slightly weaker. Make the starting hole much too big, and the fit becomes inaccurate and seriously weak. If you do a trial run, I'd go with the German suggestion and see if it's 'good enough'. Cutting the thread into the tighter American hole will be more work and - perhaps - not much benefit.

Ordinary commercial nuts and bolts are a distinctly loose fit.

Dave

Edit: pesky smileys.

Edited By SillyOldDuffer on 19/05/2019 16:14:42

19/05/2019 15:33:23

Alan,

This German site might help. It gives dimensions for the 8-UN series, all of which are 8TPI, and might well be what you've got. Machinery's Handbook describes 8-UN as 'a uniform pitch series for large diameters. Although originally intended for high-pressure-joint bolts and nuts it is now widely used as a substitute for the Coarse-Thread Series for diameters larger than 1 inch." It's a valid Unified size, just not bog-standard.

For 1½" 8TPI the German table suggests a 35.1mm tap drill, which is about right for cutting an 8tpi internal thread to a depth of 0.06766" (Source: Machinery's)

When tackling confusing threads, I usually do a trial run on an Aluminium test piece first. Checking the result against the other thread will show if you've got the dimensions about right or need to think again.

The Unified spec says the internal thread should be truncated (flat) at the bottom rather than cut to the full sharp depth of 0.10825". It should also be rounded at the top. Beyond blunting the sharp top of external threads with a fine file I don't worry too much about either detail. If male and female mate I'm happy.

Making a new thread, I usually cut to a little less than theoretical, test for fit, and then take a succession of smaller cuts until the thread engages smoothly.

The annoying this about this sort of job is I usually mess up the first attempt in a muck sweat of time wasting anxiety, then make a poor second attempt that fits. If I go to the trouble of making a third, it will be made in half the time, be closer to size and have a much better finish. Make four and it becomes almost trivially easy to churn out good results...

Dave

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