Lifebuoys in Valley Park and Access to River

Lifebuoy in the Valley Park, Kilcullen. © Eugene Brennan

I've just been thinking about these. There are three lifebuoys on the west bank of the river: one at the low section of river bank near the bridge, another further up opposite the canoe club building and the third is on a section of river bank that's high above water level, just before St. Brigid's Well.  There aren't exactly any points near the river to safely throw the lifebuoys without slipping. For the middle buoy, the slope is steep and slippery and there's just a small muddy patch near the water's edge. The grass here seems to be flattened, possibly from people making their way down to the edge to fish or to allow dogs to swim in the river. Or perhaps KCA have cut the grass for access. This section of the river as far as I understand it, up as far as the bend adjacent to St. Brigid's well is dangerous, deep and with strong currents, the location of the so called "Sally Hole", where the fast flow probably scours out the river bed.  For the lifebuoy up near St. Brigid's Well, which is on high ground, there's no access to the river. 

Would it be a good idea to have simple steps down to the water's edge, similar to the steps that were put in place near St. Brigid's between the upper and lower trails?  Maybe some gravel could be put into a cut out section of the river bank, although that would probably be washed away by floods. Or possibly concrete pads/a strip could be installed? Would that have unforeseen consequence and encourage people to congregate near the edge and start jumping into the river to swim, where it's dangerous?

A trail/boardwalk close to water level along the west bank of the river would be nice as a future project, similar to the river walk in Ballymore Eustace, and that would provide access. However we saw what happened to a similar structure on the Camphill Farm and Nature Trail.  Landslides I guess could be a potential problem though. Decades ago, there was a good view of the river from the region of the park up near St. Brigid's Well. That's now largely obscured by trees and other vegetation.

Responsibility for deployment and maintenance of lifebuoys is shared between local authorities and Water Safety Ireland. 

Lifebuoy near St Brigid's Well with no access to river. © Eugene Brennan

 

Access to river near middle lifebuoy. The slope is almost 45 degrees here. © Eugene Brennan

River Walk in Ballymore Eustace. © Eugene Brennan

Two Lifelines to Kilcullen

38 kV line that carries power to Kilcullen. © Eugene Brennan

Today was a busy day! First I had to scoff my dinner quickly (well half of it!) to be up at Dún Ailinne by 1:30 for the site tour. There was an open day today at which archaeologist Dr Susan Johnston of George Washington University gave us an update on what work had been done so far this summer. Dr Johnston has been investigating the neolithic and iron age ceremonial site since 2006, alongside a team of archaeology students. On the walk back, I snapped a picture of the pylon near the motorway bridge, that carries the power lines that supply electricity to Kilcullen. Those lines come from a substation adjacent to the turn for the Glen of Imaal on the N81. Electricity is transmitted at 38,000 volts or 38 kV from the Stratford substation in Wicklow, before being dropped to 10 kV for distribution by the transformers in the Kilcullen substation. What's interesting is that all the power for Kilcullen is supplied through three cables, probably not much thicker than a half or three quarter inch rope. In fact if the voltage was much higher, say a few million volts or so, those cables would only have to be the size of the wires on your phone charger. As you may remember from a previous article, Why are Voltages So High for Electricity Transmission?, one of the reasons for using such high voltages is to reduce current and hence power loss in cables. If we need to supply gas or water to a location, pipes have to be physically greater in diameter if we want to transport larger volume flow rates at the same pressure. That's because gas and water are actual stuff or matter. However energy isn't matter or a tangible quantity that takes up space and which one could hold in their hand. It's a property of matter. So it doesn't necessarily need a large conduit for transmission in the same way that water does. In fact in principle, superconductors the thickness of a human hair could supply the power demands of a city.

38 kV distribution line to Kilcullen. Map Data © OpenStreetMap | MapLibre | OpenStreetMap, Open Infrastructure Map 

After having the rest of my dinner, I headed off on a cycle trip to Ballymore to do the 5k loop. I took another snap here of the outflow from  the Ballymore Water Treatment Plant, which crosses the trail on the loop and also the river. I think this is the original feed that supplies water to the reservoir at Old Kilcullen. There's at least another main that heads northwards to Dublin. Over 10 years ago, the water mains were upgraded to the reservoir. The new lines operate at a higher pressure, so they can supply a higher flow rate, even though the diameter is smaller than the original line. In fact Kilcullen now actually receives most of its water from the River Barrow, water being pumped from the Srowland Water Treatment Plant near Ardscull to the reservoir at Old Kilcullen, where it's mixed with Liffey water.  The tank is so cavernous that lorries were being driven around inside it during construction, or so I'm told.

Water mains from Ballymore Water Treatment Plant. © Eugene Brennan

 

© Eugene Brennan

Gear Grinding

Lawn mower gearbox. © Eugene Brennan

Using diamond burrs to square the teeth of the freewheeling gears from the lawn mower gearbox. They were rounded with wear and slipping. A bit like being a dentist (They use a similar tool, but it's pneumatically or hydraulically driven rather than battery powered. My dentist showed me all the bits they use) Almost finished now. Crude, but worth a try to see if it'll work. The alternative is €55 for a new one. Still have to do a MacGyver job on the driveshaft bearing which has worn and come apart. I've got lots of ball bearings, but none the right size.

Two Repair Jobs Today: Replacement Wheel Bearings and New Bushing for the Secateurs

Wheel bearing replacement and new bushing for secateurs. © Eugene Brennan

I still have to put the mower gearbox back together after doing some dental work on the gears' teeth. Not sure whether it'll work, but it was worth a try. I got replacement bearings for the wheels yesterday from Amazon. One of the bearings on the back axle had corroded after five years from turning the mower on its side to hose it and remove caked-on grass. Water getting into the bearing rusted it away totally. Anyway I'm going to have to make some sort of protective shroud that'll slip onto the axle and act like an umbrella when hosing. The old bearing, or rather what was left of it, was really difficult to remove from its housing or "sheath" as it's called in the parts description. Bearings are usually put into housings using a bearing press and are a tight fit with a small tolerance. But this one had also rusted into place and so was stubborn and refused to come loose. Because the back of the sheath was tapered, I couldn't tap the back of the bearing to push it out. So I had to grind a narrow groove with a diamond burr, cracked the outer race (the thing the balls run around in) at this point with a chisel and then was able to use the corner of the chisel to get enough purchase to bend and snap a chunk off the race. That reduced the force on the sheath allowing me to prise the rest of the bearing race out. The new bearing was pressed into place in the jaws of a vice, taking care to do it evenly.

 

Worn secateurs

 

The pivot hole in one arm of the secateurs was worn, so the jaws didn't move parallel to each other when closing, affecting cutting of thicker branches. Rather than throw it out, I made a bushing ring from scrap tube of a suitable diameter which reduced the hole size to what it was originally, so the pivot bolt returned to being straight.

100 Years of the Shipping Forecast

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You may have heard Joe Duffy's segment earlier in the year on Liveline about the BBC Shipping Forecast. It's broadcast at 00:48 on BBC Radio 4, preceded by a short piece of light music, "Sailing By", before the station closes down at 1 am. On LW, the frequency then carries the BBC World Service. For some, the forecast is like a soothing mantra, the repetitive structure and intonation or melody of the words easing them off to sleep. The forecast is also broadcast later in the day at 05:20, 12:00 and 17:55, and provides detailed weather reports and forecasts  for the seas around the British Isles. In this documentary, from last January,  Kilcullen man Al Ryan who is a BBC presenter, amongst others, spoke about the shipping forecast. It celebrated its centenary in the early hours of this morning, 4th July, expertly read by Al, who always signs off with "oiche mhaith", before the national anthem is played and Radio 4 closes down.

The BBC World Service originally broadcast on shortwave in Europe, but transmissions on the SW bands ceased in 2008. It also broadcast to Britain on MW, but transmissions ceased in 2011 on 648 kHz due to budgetary constraints. It still broadcasts on 198 kHz LW when BBC Radio 4 closes down at 1:00 am. This was useful for anyone with a bedside radio having an LW band. I've been listening to it and Radio 4 on and off since the 80s. However with the amount of electronic gadgets in a house nowadays generating EMI, including chargers, burglar alarms and broadband modems, that has becoming increasingly difficult because of the interference. Radio 4 transmissions on the LW band were scheduled to end  because of increasing costs of maintaining the network, although the BBC didn't specify a date in this article from  2023. Transmission is energy intensive and parts for transmitters are becoming harder to come by. According to this article in The Guardian from 2011, only a small number of parts are still available for the transmitter. Also there's a shift from listening on radio to online and many radios no longer have an LW band. A transmitter in Worcestershire and two additional transmitters in Scotland are operated by a private company, Arqiva. According to a more recent article on the website Keep Longwave: 

"In personal correspondence seen by the Campaign to Keep Longwave, a BBC representative stated, ‘we have not made a firm decision as to when we will close the Radio 4 LW service’".

Linked content, courtesy the BBC. The BBC in no way endorses content on this blog.

 

Gadgets for Connecting to Old Hi-Fi Systems

Image courtesy Amazon.ie

This sort of gadget might be useful for those of you who have older hi-fi systems and want to stream music from your computer or mobile device. It's a Bluetooth receiver that has left and right, line-out outputs with RCA connectors for connecting to red and white line-in (sometimes called "Aux" ) connectors on audio equipment such as a hi-fi system. Cables are also available (or can be made up) to convert between line-out and DIN 41524, 5-pin connectors, sometimes used for auxiliary input on older equipment.

An alternative is to simply use a modern TV (which will have WIFi and Bluetooth connectivity) to generate the line-out signals for connecting to a hi-fi. Some modern TVs don't have red and white line-out connectors, just a digital optical output, however adaptors are available for converting this back to line-out for connecting to an older hi-fi system without optical input.

Hi-fis that only have phono inputs

My old Sony hi-fi from circa 1993 doesn't have twin line-in input connectors, just RCA phono connectors for the turntable. Although the connectors are physically the same as the RCA type used for line-in/line-out, phono inputs only accept low-level signals of a few millivolts (mV) generated by the cartridge on a turntable (the cartridge isn't powered and the signal isn't amplified). Apparently vinyl recordings use what's known as RIAA equalisation, low frequency sounds being attenuated during recording. The input pre-amp in a hi-fi or "stereo" that's connected to the phono input then does the reverse: cancelling the attenuation of low frequencies that was done during recording by boosting low frequencies on playback, resulting in an overall flat response. I won't explain why, but you can read more about it here.

Gadgets like this one are available that convert line level signals (from e.g. a TV) that are typically almost half a volt peak to the mV levels required by the turntable input. They also use a passive filter to attenuate low frequencies, simulating RIIAA equalisation.

Image courtesy Djbox.ie

I haven't personally used any of these converter adapters. Depending on what you pay for them, some are probably better quality than others and like like any intermediate system that converts and filters signals, noise and distortion will be added which degrades the final output. So sound quality won't likely be as good as when directly connecting line-out from a device to line-in of a hi-fi/amp.

Dunlavin Water Supply Rationalisation Project: Horizontal Directional Drilling

Patchs of tarmac on road, covering locations where mains water pipe was threaded underground. © Eugene Brennan

Just did a short cycle today because rain was imminent, and I could feel the drops as I headed further south: Nicholastown, Yellowbog, Gilltown, Kennycourt, Grangebeg, Boleybeg, Alliganstown, Broadleas, Ballymore, Coghlanstown, Harristown, Carnalway and back to Kilcullen, to name but a few townlands en route.
Anyway, I noticed David Walsh Civil Engineering Ltd, the contractors for the Dunlavin Water Supply Rationalisation Project seem to be using a tunnelling technique to lay the new water main from Brannockstown to Dunlavin. This is known as horizontal directional drilling. Rather than digging trenches and covering, a tunnel is bored underground, using a coring bit. The patches of new tarmac that occur at regular intervals along the road were the access points for the drilling apparatus and where pipe sections were threaded underground. I've asked DWCE whether any construction images are available and they said that "we will post a project update on Dunlavin in due course". 

 

"3760" marked on the road appears to be the distance in metres to Brannockstown. (I measured it on Google Maps).

Edit: The company confirmed this is the technique they are using.

 

© Eugene Brennan

© Eugene Brennan

 

Lawn Mower Woes, Safety Glasses and Spare Parts From Vehicles

Lawn mower float bowl. © Eugene Brennan

I usually wear safety glasses when cutting the grass bank outside the house. I don't in the garden, but outside there can frequently be accumulations of stuff since the last cut: rocks and stones and sometimes parts that come off vehicles. I've hit the handle of a bucket on one occasion, which flew out from under the front of the mower and became airborne. Today I found this pin. Not sure what it is, but it seems to have broken off a longer piece and has a wear mark as though something was rubbing it. It could easily have struck someone walking along the footpath, either from me hitting it with the blade or when it came off a vehicle. Anyway, I do a recce before cutting to check for such items and also dog poo. Hitting something hard like this usually puts a big dent in the blade. 

 

Mower Repair Frustration

 

I starting cutting grass this morning. Then I got delayed on a long phone call. I was going to paint the cappings of my gate pier this afternoon, but ended up attempting to resume grass cutting instead. But of course the mower wouldn't start. I predicted a fuel flow problem, took the float bowl off (It functions pretty much the same as a toilet cistern) and just as expected, dirty fuel with some black grime particles ran out of the bowl. This stuff comes from the filling station, because my Jerry can is sealed and dust doesn't go into it. I guess the tanks in filling stations aren't exactly pristine and corrode over time or coatings on the inside wear off. Or maybe the grime is in the fuel on delivery. Anyway, fixing something outdoors isn't a good idea, because parts usually get lost in grass or gravel, but I decided to do it in situ, rather than dragging the mower back to the workshop. I thought I had lost the sealing washer from the bowl on the driveway because I had heard something falling. I wasn't sure what I was looking for and I couldn't remember what the washer looked like, so I had to put a post on a lawn mower repair forum to enquire. It turned out it wasn't lost, but stuck to the underside of the bowl. After all that, I put everything back together and the mower started on first pull. Then I started it again outside the wall and it decided to backfire and snapped the starter rope. So that'll have to be fixed tomorrow. These farcical scenarios are regular occurrences, or a variation on the theme is "There's a hole in the bucket dear Liza" versions, where 5 minute jobs turn into day-long projects.

Float bowl. © Eugene Brennan

Carburetor jet. © Eugene Brennan

Float bowl float. © Eugene Brennan

Broken starter rope. © Eugene Brennan

 

Lucky I didn't hit this with the blade! © Eugene Brennan

CD vs Vinyl Debate

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In order to reproduce sound faithfully, the Nyquist-Shannon sampling theorem says that a sound can be perfectly reconstructed from its samples if the sampling rate is at least twice the highest frequency component of the signal. That's not the fundamental frequency of the sound, it's the highest frequency component of the signal when its spectrum is viewed in the frequency domain. The timbre or difference in tone colour between a pure tone and e.g. the sound from an organ, both with the same pitch and loudness, is that the organ sound has a fundamental frequency and higher harmonics (multiples of the fundamental frequency). The combination of, and amplitude of harmonics is one factor that makes the timbre of a musical note from a piano different from that of e.g. a flute or violin. The discussion in the forum at the link suggests that CD recordings should be better than analogue recordings on vinyl, considering that sampling is done at 44 kHz (twice the 22 kHz bandwidth allowed for audio signals). However there are other factors involved, and another forum member suggests that compression of the signal is involved when the pressing master is made from the original master, and production CDs suffer in sound quality due to this. Compression is necessary to reduce dynamic range (the difference between the loudness of loud and soft sounds) so that recordings can be listened to on earbuds rather than a hi-fi system, the latter having greater dynamic range capacity. This compression of dynamic range is distinct from the compression of the size of files to reduce the storage space required on media. That compression is variable and produces either lower quality/smaller file size or higher quality/larger file size recordings, typically in the MP3 (for audio) or MPEG (for video) file format. This is similar to the way bitmapped images are compressed into a JPEG image file. Unlike MP£ files, sound tracks on a normal CD aren't compressed and the data is in a raw format that can be read by the electronics.

A debate on the subject here. 

Tunnelling Work Continuing Near Railway Bridge at Moorhill

Water main at Moorhill, south of Brannockstown © Eugene Brennan

Pipe laying seems to have been completed on the Brannockstown to Dunlavin road as part of the Dunlavin Water Supply Rationalisation Project. The project involves construction of approximately 7 km of pipeline connecting Dunlavin to a new booster pumping station at the Brannockstown Pumping Station site. According to Uisce Éireann, the new supply is to:

 "Increase security and resilience of the drinking water supply to approx. 1,000 customers in the area."
 
A tunnelling technique was used to lay the new water main and this is known as horizontal directional drilling. Rather than digging trenches and covering, tunnels were bored under the road surface, using a coring bit. The patches of new tarmac visible at regular intervals along the road before it was resurfaced were the access points for the drilling apparatus and where pipe sections were threaded underground. The railway bridge at the turn for Boleybeg on the Dunlavin road would have been an obstacle and I noticed while cycling by this location a couple of weeks ago that tunnelling for pipe laying is now taking place in the land in front of houses. David Walsh Civil Engineering were the contractors awarded the project by Uisce Éireann.

See also: Dunlavin Water Supply Rationalisation Project.

© Eugene Brennan

Excavation Has Gone Nuclear: 24 g Shifted

Almost 24 g of material, excavated by ants. © Eugene Brennan

The ants have been excavating tunnels under the floor of my utility room for the last few years. This occurs during the summer. It would be a lot of hassle blocking up the holes because the tunnel entrance is behind a door jamb. Anyway, sorting this problem is low down on my ever-growing-longer list of chores. There was a huge amount of activity overnight, taking advantage of the dry weather. Construction has carried on into the daylight hours, which is unusual. Are there ant "weather forecasters" that give the go ahead for mass mobilisation of construction workers like what happened on D-Day? I weighed the material excavated in the last couple of days on my drug dealer scales (or so it was called by members of an electronic forum I'm a member of. Disclaimer: I'm not a drug dealer) and it's almost 24 g (one ounce = 28.35 g) . According to a BBC article, an ant weighs 1 to 5 mg. However they can also lift 20 to 50 times their own weight, depending on species. The material they were excavating under my floor was small soil/sand particles probably equalling the weight of an ant, so I guess lots of ant-hours of backwards and forward movement was required, rather than Herculean lifting skills.

Sand and  soil excavated by ants. © Eugene Brennan

Why Does a Hot Day Feel Hot?

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Did you know that it's not just high temperatures that makes us feel hot on sunny days in the summer? 

Normal skin temperature for an adult ranges between 33 °C and 37 °C. Our bodies are cooled naturally by perspiration that's released from pores in the skin. When sweat evaporates, it carries away heat from the body, reducing skin temperature. Capillaries in the surface layers of the skin also help with cooling by circulating blood, which also loses heat to the ambient air. Anything that interferes with this process changes the perception of how hot or cold it is at any one time. So higher humidity reduces the rate at which perspiration evaporates, making it feel clammy and warmer. A less humid day doesn't feel as warm, even though the temperature may be the same. Air movement also increases the rate of heat loss from the skin. So a windy day feels colder than a day when the air is still. The air blown out of a room fan feels cold. Fans don't actively cool air (air conditioners do) The air they circulate is at the same temperature as the air in the rest of a room. They simply remove air that has been in contact with skin and has absorbed heat from it. They do this continuously so new air is always moved into contact with the skin. Since this "new" air is at room temperature and not warmed, heat flows at a faster rate from skin. The reason for the greater rate of heat transfer is because heat flows from a region of hot temperature to one at a lower temperature. The greater the difference in temperature, the higher the rate of heat flux. And so this cools our bodies faster than natural cooling. Blowing on hot soup in a spoon does the same thing.

"Take Your Coat Off"

Attic cold tank. © Eugene Brennan

The insulation on the cold water tank in my attic is an ad hoc setup from 20 years ago or more. I just used leftover fibreglass insulation from doing the floor and shrink-wrapped it around the tank. I'm thinking of replacing it with a removable jacket that I can take off in the summer so the water insides absorbs ambient heat. Might lower the cost for heating water somewhat. At this time of the year, water from the mains is colder than the air temperature. However a heat exchanger would improve things. That would take heat from the attic and put it into the water. A heat exchanger uses fins for increasing surface area to maximise the rate of heat transfer. That's why radiators in vehicles and in your home are finned or have accordion-like metal corrugations. Similarly for the heatsinks on some electronic components such as power transistors and microprocessors. The ambient temperature in an attic that doesn't have the slope of the roof insulated can reach the mid-thirties on a sunny day in the summer. Unfortunately water, compared to other a liquids has a huge specific heat capacity. That means it takes a lot of heat to raise the temperature of a kilo of water by 1 deg Celsius. (4200 J⋅kg−1⋅K−1, expressed as "joules per kilogram per Kelvin. The joule is the SI unit of energy).

I remember in the 70s, water was always warm when it came out of the cold tap. I guess that was before the cavernous reservoir (which lorries were able to drive around in, I'm told) was constructed in the hill at Old Kilcullen. Before that, I think our water came from a reservoir on the elevated ground behind Dunlea's garage. The likely smaller volume of water in the tank and lower population in the town resulting in less water flowing from the tank probably gave it time to warm up.

Sewerage Network in the Town Centre

Image courtesy RPSGroup and © Kildare County Council

From the Draft Kilcullen Settlement Plan. The first number on pipes I think is diameter in mm, and the code that follows is the material: uPVC is unplasticised Polyvinyl Chloride, VC is vitreous clay, CO is concrete and CL is cast iron. Sewage flows through the sewerage network to the pumping station at the back of the Kilcullen Farm & Nature Trail. From there it's pumped to the Osberstown Sewage Treatment Plant.
A clay pipe seems to be visible in the bed of the river, south of the bridge. This is probably the original sewer from the southern part of the town to the old treatment plant in the woods across the river from the farm trail. (Maybe somebody more knowledgeable could confirm this?). Or possibly it's one of the overflows shown on the map? I'm not aware of any obvious outflow pipes above the waterline.

Re-Use Your Waste Oil

Waste oil. © Eugene Brennan

Did you know WD-40 isn't specifically a lubricant? Its primary function is as a penetrating oil, for freeing stuck bolts and similar. Waste engine oil is perfectly suitable for hedge cutter blades and garden shears., although probably not good for the environment. It's thicker than light machine oil and so stays longer in contact with metal surfaces, without being squeezed out. Lubrication is a Goldilocks process. The lubricating layer shouldn't be too thin, or surfaces will still rub together, increasing friction. If the layer is too thick, it results in viscous friction, which can cause energy loss and drag on fast moving parts in contact.

Can't Make Decent Tea Anymore

My grandmother's teapot. © Eugene Brennan

Once upon a time, it was possible to get nearly two cups of tea from a Barry's tea bag. Now it takes nearly two bags per cup. I remember learning in Inter Cert science that one of the attributes of hard water is that it's difficult to make tea with it. So that's the consequences of getting our water from the Barrow instead of from the Liffey, which has its source in the granite of the Wicklow Mountains. I don't think BRITA water filters or their clones remove lime from water. The lime also clouds shower doors and takes forever to clean with vinegar, the coating returning within a week. So I just gave up regular cleaning and only do it when the stalactites are ready to snap off.

TV Signal Problems

Sarah777 at English Wikipedia, Public domain, via Wikimedia Commons

If you get your Saorview signal from Kippure and are experiencing reduced signal strength and picture breakup, this may have been the reason: essential maintenance.
FM was mentioned, but TV programmes were also affected for a short period this evening.
The flashing beacons on the Kippure transmitter mast can be seen from several vantage points in the town at night: on New Abbey road and at the Riverside development. The mast itself can be made out on a clear day from the crossroads at the top of McGarry's Lane.

2rn is the trading name of the RTÉ Transmission Network, named after Ireland's first radio station 2RN, which started broadcasting in 1926.

Saorview and radio signals can be received in Kilcullen from Mount Leinster in Carlow, as an alternative to Kippure.

 

Edit, UHF digital TV transmissions are of course FM

More Boiler Woes

Cleaning the filter on the oil tank. © Eugene Brennan

I let the oil run out a couple of weeks ago while waiting for price to drop. Got a fill of oil and thought I'd just have to bleed the boiler, but no air and oil escaped from the bleed vent when unscrewed. Checked the filter at the tank and it's not blocked. So fine sludge has probably got through the screen mesh of the filter and perhaps blocked the pre-filter in the boiler. So hopefully the oil line won't have to be dug up, because it's under concrete, and the boiler service people can just clear the line with compressed air or flush it. Anyway it's more expense. Moral of the story, check your oil regularly. I always do, but just let it down a bit far while waiting for price to drop.

Bleeding air on the boiler. © Eugene Brennan

A Vintage Flyback Transformer

Teravolt at English Wikipedia, CC BY 3.0  via Wikimedia Commons.

These were used in TVs until cathode ray tubes (CRTs) were replaced by plasma and then LED displays. CRTs use an electron beam that traces out an image line by line on a glass screen, starting at the top left of the screen and working downwards. The path followed by the beam is just like how we read text on a page. A flyback transformer is used to produce a high voltage, in the order of tens of kilovolts, to accelerate the beam and make it strike a phosphor coating, the latter emitting light on impact. Only one point on the screen is illuminated at any one time, hence the bright spot at the centre of the screen when old TVs were powered down and the scanning coils were turned off. Persistence of vision and the 25 Hz scanning rate (50 Hz in total because of interlacing) give the impression that a complete image is displayed all at once.

Digby Bridge and OPW Work

Digby Bridge on the Grand Canal, north of Naas in Co. Kildare. © Eugene Brennan

My cycle today was along the canal from Naas to Digby Bridge between Sallins and Prosperous. Good to see that the OPW (or Waterways Ireland?) took on my suggestion to remove a dangerous board from the cover on the feed/overflow channel from the canal at the bridge. It was rotten at the ends and only supported by two steel joists and none in the middle, liable to collapse if anyone jumped on it. They used a steel plate and galvanised steel grating as a replacement. The wider boards seem to have been trimmed, although I didn't think this was necessary and an adjacent board to the one that was rotted could have been removed also, but I guess they knew what they were doing. I think this might be a temporary measure, maybe until all the timbers are replaced. The first few photos were from last September.

Rotting timber on edges of boards. © Eugene Brennan 

Rotting timber on edges of boards. © Eugene Brennan

Rotting timber on edges of boards. © Eugene Brennan

After remedial work, with grid and steel plate in place. 

© Eugene Brennan

© Eugene Brennan

© Eugene Brennan