What did you do today? 2023

Bob's OK - all he's done is improve the bonding between his lathe and his workshop's common earth. The earth isn't parallel in the Air Force sense.

The Air Force had two or three, distribution systems in play. Generators on the aircraft, earthed to it's frame, which is safe for anyone inside the aircraft, but the airframe isn't connected to planet Earth. In the air the plane is completely isolated from Earth, and after landing the connection to Earth is indeterminate. Rubber wheels on a dry concrete apron are a good insulator.

A parallel earth problem occurs when an aircraft has its generators running and needs to sitch over to a ground supply without losing power. Very different to Bob's lathe! There are at least two distribution systems: the aircraft, a temporary mobile ground generator, and maybe a mains supply in a hanger being connected together. Each system has a different earth, making it essential to connect the wires up in the right order, and under no circumstances to assume that all the earths are at the same potential. Only after being bonded together are the earths safe, and there are a few ways of getting it wrong.

Another earth risk is from static electricity. Friction caused by travelling through air can charge an airframe up by many kilovolts, and a big aircraft body can store enough charge to deliver a nasty shock. The Hindenberg was a large dirigible with an Aluminised skin. Possibly it was destroyed by a static spark starting a fire or igniting a small Hydrogen leak. Once a fire started, the lift Hydrogen was stored in thin balloonets, with nothing to stop the whole lot igniting. It's suggested a static spark to earth occurred when a trailing rope at the rear hit the ground as the Hindenberg approached the landing mast.

Not unusual to get a small static shock getting in or out of a car. Petrol pumps are designed to discharge vehicle static before pumping petrol, but fires do occur, usually in hot dry countries.

A third possibility is natural. When two distant earths (miles apart) are connected by a wire, it's usual to find the two earths are at different voltages, with current flowing between. Usually small and not dangerous, but enough for telephone and telegraph systems to allow for it, and in rare circumstances, it upsets power distribution systems.

Connecting two different power distribution systems together is exciting. I worked with an ex-RN Engineer Commander who had disgraced himself by getting a ship-shore 3-phase connection wrong. He described the process thus:

• The ship's 3-phase system and dockside 3-phase are connected to a switch panel. Both systems are at the same voltage and nominal frequency, but the ship generator is either leading or lagging the shore side. Depending on what the ship is doing, could be megawatts involved.
• The two systems are connected phase to phase by lamps. These glow bright, glow dimly, or flash depending on how out-of- phase the two generators are.
• From memory, don't try this at home folks, the ship generator is speeded up or slowed down until the flash rate slows down, so the lights only glow dimly, if at all, at which point the big switch is quickly thrown to join the two systems. Has to be done quickly because the ship generator can over-shoot and get out-of-phase again
• It's impossible to get it absolutely right, but when the switch is thrown close-enough, the more powerful shore connection grabs the ship's generator and synchronises the two exactly. A mechanical and electrical jolt that has to kept as small as possible is caused.
• The two systems might run in parallel for some time, but more usual to disconnect the ship generator and let the ship run on shore power alone. Restarting the ship generator was the same procedure - running the generator up to speed, tweaking it for phase, and switching when the flashing stops

It went wrong! At the critical moment, he was interrupted and threw the switch too late. In his defence, my description is a simplification. Warships have multiple generators and their electrics are unusually complicated. Not simple.

Connecting two powerful out-of-phase systems caused a lot of damage. Shore-side fuses blew, the ship lost basic power at an embarrassing moment, fuses popped, all the wiring and switchgear had to be confirmed good, and a large generator had to be replaced. Serious stuff. A costly career ending mistake, and a warship off the active list whilst emergency repairs were done.

I wish I'd asked which ship it was. Perhaps one of Her Majesties older vessels. With hindsight, I'd have expected the switch-over to be automated. Relying on a distracted human being to judge flashing whilst twiddling a big generator feels unwise. On the other hand, flashing lights are delightfully cheap and simple. Maybe the manual system normally works well, and accidents are rare. Anyone done this sort of job?

Dave

If you see the full Hindenburg disaster newsreel - usually we see only the fire itself - it seems the leak was anything but "small".

It is pitching badly still some way away from the mooring-mast, with a lot of ballast water being discharged for'ard, suggesting developing loss of control; before the fire appeared.

The first, visible external flames are on the starboard side, near the stern. The spark, if that was the cause, would surely have been within the air-ship, not on the ground a hundred feet or more below a mass of hydrogen that would escape upwards. Since hydrogen is colourless, odourless and tasteless, it is feasible gas leaking astern would already have found its way to the bow without anyone realising, especially as the accommodation and control areas were mainly in the lowest sector, and below, the hull.

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I don't know what power-stations now use but I think synchronising the alternators to each other and to the National Grid used to involve a null-meter as indicator, far more accurate than trying to judge the glow of a lamp.

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There are anecdotes of people receiving shocks from static-electrical charges developed on traction-engines with rubber tyres, in dry conditions, by the flow of steam from the safety-valves.

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Returning to more homely matters, I rely on all my workshop machines and power-tools using the normal 13A supply earth. They all run from 13A plugs.

The electrics on the Harrison lathe and BCA jig-borer are physically separate from the machine bodies. The BCA has by a thick PVC plate adaptor to fit the modern motor to the original mounting; and the fasteners are two set of set-screws in tapped holes in the plastic. The lathe's motor and VFD are all on the wall above the machine.

When I worked on steam turbines we used to fit Woodward governors to those destined for generators. By some magic means these took care of synchronising both speed and phase. No idea how, we just provided a drive, the governor had a lever sticking out which connected to the balanced throttle valve. It is 50 years ago, so details have faded

Edited By duncan webster on 21/06/2023 15:46:51

I have a new (to me) push bike with a 5 speed Sturmey Archer hub gear (RX RD5). The lowest gear is a little too high for my poor old knees so I decided to change the rear sprocket from 20T to 22. The RX RD5 hub takes a gear with a 50mm centre hole and, guess what, you can't get that size in 50mm, just 35mm. So, to the workshop.

First I made a nest for a 22T gear with a 35 mm hole and turned out the middle until it was the diameter over the driving dogs:

Then transferred to the rotary table. A quick sketch in CAD showed that with a 4mm end mill I needed to cut for 102 degrees then jump over 18 degrees before cutting the next 102 degrees etc.

I printed a go/no go gauge because measuring the diameter was somewhat tricky

A bit of work with a file to bring the dogs to the correct profile and it worked

I can now climb the dual use bridge over the dual carriageway and get to a pub in the forest

Rod

After a successful bout of machine and accessory selling, I parted company with my lathe today. My goodness, the garage/workshop sure looks empty. I shan't be totally idle, though, I intend to concentrate my attention on CAD/CAM design and 3D printing the results.  I have a few ideas bouncing around inside my head. I only hope I can get them out.

Another batch of goodies coming up for sale in the not-too-distant future.

Just got to decide which side to place the 3D printer when it arrives.

John

Edited By John Hinkley on 22/06/2023 16:34:59

Not much doing but did get a new tool made as I had a insert sitting doing nothing but no tool holder. Photo not too good but gives an idea

My Austin Seven is now up on its axle skates, each with 4 heavy duty castors, and I can move it in any direction by myself. I can now start on replacing the hydraulic brake cylinders (Morris 1000), and draining the stale petrol from the fuel tank.

I got fed up with the lathe spindle slipping when I took a cut. It was ok when I could do a 25 thou cut but today it slipped at 15 thou. I bought a Brammer belt last year but life got in the way so I decided I’d do it today. I measured the old belt and removed the excess links. After trying it a couple of times and removing a few more links once it had settled in I was able to take a 100 thou cut. Not bad for an old Boxford lathe

Fitted a t-slotted extruded aluminium table, intended for building CNC routers l believe, as sub table to cover up 80+ years worth of 'arc of shame' on my pillar drill. Makes positioning of the vice very easy, and have just ordered some Bristol levers which will make it even easier.

We fitted Woodward governors to C Range Rolls Royce oil engines intended for genertor work.

For the sets intended to be paralleled, the "Master" set had a PSG isochronous governor fitted ,and the "slave" set / s had SG units , which allowed some "droop" to parallel.

On the PSG, the droop could be adjusted, in some cases so that the arm went beyond the centreline (Beyond Isochronous ) so that the speed fell as the load was reduced!

The larger D range engines used Regulators Europa governors, as I recall.

Paralleing "With an infinite bus" (The mains ) involved trying to adjust the incoming alternator set until the phase lamps ceased flashing, or only did so very slowly, so that the reverse current relay did not open.

Electronic governors were just coming in and solved many of the problems seen with mechanical or mechanical/hydraulic governors..

At Souithdown, Central Works, during the winter months, the fluorescent lights were powered by Gardmer 5LWs, removed from old buses, driving 6 pole Maudslay alternators, at 1,000 rpm.

Because of the low speed, governor forces were low, so someone had extended the governor lever to increase sensitivity. Too far! The sets were never stable and an ex matelot from the battery shop spent every afternoon trying keep the three sets in parallel.

I never saw a time when the three lamps were not flashing, so there must have been circulating currents..

Howard

Dropped a 75mm long, 50mm dia. finned cylinder, hogged out of a M/S billet onto the corner of an angle-iron workshop dolly as I was giving it a last clean-down. How we laughed..

just to prove I occasionally make something, the grate for my test boiler, ands the trivet arrangement it sits on. I thought I'd give a pinhole/Rosebud grate a go

Bottled up a substantial quantity of Sloe Port, and started the last batch of Sloe Gin from last year's haul... That should mature in time to do one final batch of Sloe Port before we get started on the Crabapple Gin which will finish in time for starting the Plum wine before this year's Sloe harvest...

I am less clear when or how we're going consume the sheer volume of port, gin and wine being produced, but we can work on that.

You do know, don't you, that you can always rely on help forthcoming on this forum...

Compressor enclosure: Noisy

I found a metal frame at 2ndhand shop big enough to fit my piston compressor perfectly with frame and enclose it to reduce the noise. Apart fom 20mm MDF sealed side covers, I might add rubber inside to absorb low frequency noise. I am pretty sure I get it noticeably quieter.
Also restoring a RongFU R-115 metal bandsaw which I will fit on top of this frame with heavy duty castors welded to it bottom, whole assembly can be moved around.
The bandsaw will set on top and be able to swing vertically as a unit out of the way, revealing a workspace on top of the compressor, made of 3x layers 20mm MDF & stainless plate on top, which will mainly be used with lathe. Fan will be added for air to compressor. Think of adding a ballance weight for swinging the bandsaw vertically as a unit(Not its own vertical swing option)....This will take a while.

I hope you will have filters on both the fan and compressor inlet. Putting a dust generator on a vacuum pump has it's disadvantages...

I like that space-saving idea of the compressor and saw sharing a trolley.

I would go a little further than filters though, and also find or make a dust-cover for the compressor and fan when they are not in use.

I've been pondering something similar combined with a static storage area and the overhead travelling-hoist for the smaller machines I have in my over-crowded workshop. I am part-way there having built a hefty, two-feet square bench with a 10mm thick steel plate top drilled and tapped to take each of the hand-shaper, bar-bender and vice, separately.

The whole compressor will be enclosed, with only open spaces in front, round holes(Hand can just go through it) to see guages, reach on/off switch and shut off leve air output. The panels are bolted to frame, bur can easily be removed if needed to work on compressor.
The intake has a filte(Like usual small), but I am going to extend it into a chamber with filter box(Will look at motorcycle types) to reduce intake noise as well, ..reached from the top. I agree with filter to intake fan, which will be positioned over compressor wheel-Rear side(Fan belt driven) which acts as cooling fan for compressor.
The fan will positive load the case with air(Compressor itself 1st choice), and through the filter the inside should stay way cleaner than before. I will see what happens to electric motor temp when finished.I only use it sporadical when needed.

Edited By Chris Mate on 26/06/2023 18:59:49

I completed an open-topped assembly-bench and ramp, with trailer-winch, for working on my steam-wagon without having to grovel on a ground that seems closer than it used to be but harder to descend to in a controlled fashion, but much further away when I try to get up again.

Last task on that this evening was securing the vehicle on the bench and sheeting it down.

Last task while it was still vaguely light was going into my late neighbour's overgrown garden to cut down some enormous weeds I did not want seeding over the wall (down prevailing wind) into mine and my other neighbour's. Their stems, some approaching an inch thick at the base below the first branches, and up to about six feet tall, were soft enough for secateurs. I am no botanist so I don't know what they are, but I hope they are not some notifiable species or armed with something yet to get me. Triffids, probably.

(Late neighbour - a man living alone, found fatally collapsed in the street elsewhere in the village, two or three months ago. He had partially cleared his garden but it is now a jungle and his relatives, although local, have done nothing with it. I don't think they've even finished clearing his belongings out, but I might be wrong. I've only seen them there once. His small front garden like mine, is mainly a shrubbery and I've taken it on myself to trim the bushes back to the wall, along with mine, when they start to overhang the pavement. )

Then indoors, brew, reply to a private seller on this very forum.

Beware….sounds like Hogweed. Nasty stuff. Even allowing for BBC hype!

https://www.bbc.co.uk/news/uk-england-london-66005465