Onewheeler
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Posts posted by Onewheeler
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It should work, my only reservation would be that it's not clear how it would like a modified square wave input. A PSW invertor should be OK. At 1 kW you'll need a heat sink, but not a big one.
Let us know how you get on! It might be a useful means of running a domestic macerator toilet from an invertor.
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A happy discovery: the tiller arm is a snug fit over the spout of the washbasin taps, enabling me to wield the biggest spanner on the scaled-up tap to change its washer.
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4 hours ago, Scholar Gypsy said:
Does this suggest that your skin tank (or heat exchanger if you have one) is a bit undersized? I understood that the pressurization was to reduce local boiling near hotpsots in the engine, not to enable the coolant leaving the engine to be much hotter than the thermostat rating?
Yes, it probably is, but at our normal speeds the temperature seldom goes into a region that gives me concern. Pushing against a river in flood needs a careful eye on the temperature gauge though!
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4 hours ago, Tony Brooks said:
I do not see any need for thermal relief valve - if that means it vents the cylinder if it overheats.
Many boats have thermostatic mixing valves fitted and unless you have a solid fuel stove the water transferring heat into the calorifier is controlled by the engine or central heating thermostat. This is why some marine engines with fresh water cooling may have a thermostat around 66C. Many boilers also have a safety cutout overheat thermostat.
The engine thermostat does not control the coolant temperature if the thermal output from the engine is too high for it to control. My engine regularly goes way above the engine thermostat temperature as most of my cruising is at 8 - 10 km/h. I'm not in the market for a thermo/pressure relief valve, but where the engine coolant could exceed 100 C without raising an alarm it could be argued that there is a case for a combined parameter valve to protect the occupants from secondary side boiling. An engine temperature warning set at an accurate level under 100 C would be more useful: I am not convinced of the accuracy of the one on our engine although it should be under 100 C. The pressure cap on the primary coolant is, according to the manual, 13 psi, which with antifreeze added could enable it to reach 124C before relieving. It therefore does not give significant protection to anything but the engine.
Open to argument over whether a thermo/pressure relief valve improves safety...
Martin/
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22 minutes ago, Tony Brooks said:
I don't fully understand what you are saying but ordinary "boat type" PRVs are available from 1 bar or less.
We are discussing combined thermal and pressure relief valves. I've never seen one in a chandlers, or a DIY shed come to that. Lowest pressure available on a quick search is 4 bar, most are 7 bar or more.
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1 hour ago, Mike the Boilerman said:
No it's direct feed, known in the world of building as 'unvented', the same as a boat calorifier.
I.E. no open vent pipe on the outlet discharging over a header tank.
OK! I've never come across one before but it does seem a good idea. A quick search shows nothing available at under 4 bar, which is a bit high for many calorifiers. How many boats actually have one fitted? One could tee-off a separate PRV at a lower pressure rating.
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42 minutes ago, Mike the Boilerman said:
On a household system there will be two PRVs. One in the cold water supply to the calorifier, and another connected directly into the calorifier. The second is actually a "temperature and pressure regulator", and also opens if the temperature in the calorifier rises above 90 degrees C.
Is that not for direct feed systems only, or am I behind the times? (It would not be unusual!)
Are the plastic containers indicative of where the leaks are coming from? It looks from the slightly fuzzy photo as if there is a bead of water on the tee-fitting above the white container.
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I have similar, it works fine. Mine has an external shunt. Only minor grumble is that with low loads which should be within the resolution of the current metering it doesn't register. Planning to investigate further this week. It's fascinating to watch the Webasto consumption changing through its cycle.
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1 hour ago, WotEver said:
Of course, if you buy the popular (and comparatively cheap) Airlink IT then it comes with a surge limiter built in.
https://airlinktransformers.com/product/boating-transformer-bt3231
Eek! I only paid a few tens of quids for my 1 kVA isolating tfmr. One doesn't see those prices on Ebay any more!
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36 minutes ago, nicknorman said:
Anyway, I presume you are plugging the IT into the shore bollard first, then plugging the IT into the boat or otherwise switching on the boat's supply (e.g. at the consumer unit) - if there is no load on the transformer output then obviously the peak current will be minimised.
Not obvious at all. If you happen to make the connection at zero degrees phase the current into the transformer will be maximum. The minimal load usually connected is of minor significance.
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10 minutes ago, AndrewIC said:
You can get varistors intended to go in series with the primary for this purpose. Ametherm MS35 5R025, for example. They run pretty hot though.
NTC thermistor would be a cheap and nasty solution, and might do the job (assuming that 5 ohm is sufficient to avoid tripping the marina's MCB, which it might not, as it's rated at only 6A and seems quite sensitive. It's a class B so moves fairly fast. Last time I looked 6A type C MCBs were as rare and expensive as unicorn bits, even if the marina would let me put one in.)
As I've got all of the bits I'll probably assemble something like figure 1 in this: http://www.edn.com/design/analog/4349191/Time-delay-relay-reduces-inrush-current
I'd wondered what other people use, if anything.
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I wonder if anyone has installed a soft-start on their shore power line. If I randomly connect on the wrong part of the mains phase the isolation transformer trips the shore-side MCB, which is a nuisance. I'm thinking along the lines of a big resistor at a few tens of ohms with a shorting relay and a simple time delay circuit to let the transformer field build up.
Martin/
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1 hour ago, system 4-50 said:
I would very much like to have a better way of measuring tank levels. My current WEM sensors are too coarse, about 12 uneven steps from empty to full. Obviously finer detection is a waste of time unless you add computer powered averaging to eliminate wave effects in the tank. I'm sticking with the idea of steps plus a flowmeter (inbound) at present but the flowmeter is coarse as well.
I've got a RS 181-1340 1 psi sensor waiting to be played with. 1 psi range, but it needs an op-amp interface to the Arduino as the output level only spans 30 mV.
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Had started to use a pressure sensor + Arduino for monitoring the water tank level, but the sensor wasn't stable enough. Have a better quality sensor which will be developed sometime. (Unless I just use a sight tube!) Main problem is finding a sensor with sufficiently low pressure range, but they are available (the new one has a span of 100 mBar I think)
I also considered using an Arduino as a rudder indicator on our shared barge, but ended up using op-amps and an analogue meter: mainly because a digital display would be too hard to read in bright sunshine.
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On 06/11/2017 at 15:07, ditchcrawler said:
Not been for a couple of years but we never paid, just moored to the bottom of the lawn, walked up booked a table and stayed overnight. Mooring fee was never mentioned No mention of fees here ether http://troutinn.co.uk/boat-fish/ or am I at the wrong place.
That looks like it. It is / was free if you are dining. A nice spot although I thought the restaurant unexceptional considering their prices. It is a handy mooring as it's difficult for quite a long way above and below.
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Lovely moorings at Lechlade between the lock and the bridge, about £4 a night with discount for a week. Several pubs in town, one with microbrewery.
The Maybush was closed last time we passed, it may be open now.
Tadpole Bridge was £25 a night last time unless you had booked a mooring to dine, although I blagged a free stop once by drinking a lot of the pub's beer.
Kelmscott worth a stop for the Manor, open Weds and Sat I think. There's often a discount on entry from Travelzoo. Nice pub nearby.
Martin/
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2 hours ago, Onewheeler said:
A lot of the moorings near Oxford even if signposted are unfeasibly shallow.
I should have said on the canal.
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Worth looking at the small ads on the DBA web site (barges.org) Such things do pop up occasionally, or you could place a wanted ad...
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Be aware that pretty much all of the Thames moorings near Oxford are officially 24 h, other than East Street where the second day is a fiver (and the third fifty). Outside Oxford the moorings opposite the Rock of Gibraltar don't have an explicit limit (I think the sign has been nicked) and there's an hourly service into town (it takes an hour though). The pub has space for a couple of boats and is very boat friendly. They might object if you outstay your welcome.
You'd probably be OK above Iffley Lock once past the lock moorings and the pub, although it's a good walk into town (but pleasant if you go up the river rather than Cowley Road). There's usually space. Otherwise amongst the trees upstream of Sheepwash Channel should be OK, it's nice and quiet there. Officially 24 h but as the signs are well hidden you can reasonably plead ignorance. A machete is often useful on the Thames.
A lot of the moorings near Oxford even if signposted are unfeasibly shallow.
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1 hour ago, David Schweizer said:
We rarely ever had to go down the weed hatch on Helvetia, despite her having a deep daught. And that was probably the reason, we could have fittted a 27" prop with a couple of inches clearance top and bottom, but having a "modern" high revving engine, we only needed a 17" prop, consequently most stuff that would jam on a shallow boat just bounced through, banging the uxter plate on it's way through. Most modern shallow draughted boats only have a couple of inches clearance so a lot of the floating debris will jam, requiring the weed hatch to be opened.
I think you're right David. We have a good 15 cm clearance, if not more (I must measure it). I believe the original owner of our boat tried fitting a chuggy chug engine driving a hydraulic motor, possibly at low rpm with a big prop, and it was less than successful.
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1 hour ago, Dave_P said:
I find this fairly amazing. When you say Birmingham, do you mean just the Mainline, or have you experienced the fun of the Walsall Canal, the Dudley no.2, the Tame Valley etc? If I go a couple of hours on those without picking something up, I feel pretty pleased.
We've done quite a lot of them over the years, including a ot of the loops. Dudley canals were memorable as the water was gin-clear at the time and the bottom a solid mass of plastic.
A lot seems to depend on hull design at the back end: we've been in the company of boats where someone seems to be always down the hatch. A quick burst in astern gear seems to clear our prop.
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2 hours ago, Alan de Enfield said:
Removal of the hatch and checking of the prop should be part of your daily 'checks'
I've opened mine three times in twenty years. Once in anger (fishing rod bag around the prop), twice to check prop dimensions. Have been in all sorts of dodgy places (like Birmingham).
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If you don't want to make one, the Amperor device would meet your spec for driving 12v LEDs. https://www.amazon.co.uk/Amperor-LCD-Volt-Stabiliser-Regulator/dp/B000ZLRXG8
May be cheaper elsewhere.
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41 minutes ago, mross said:
It appears to me to be one, long spiral. If you cut the coil it will go 'piyong!'
You could try connecting one of the white wires to the middle of the spring, if you can solder.
Half the resistance, twice the current...
A trick I have used in the past is put put a big diode (suitably rated and heatsinked) in series with the mains feed. That might not work if the MCB on the shore supply is tripping.
Soft Starter - one for the elecrical bods
in Boat Equipment
Posted
Looking at the spec sheet you might just get away without one, but my preference would be to fit one. Either find a handy piece of *flat* steel to mount it on, or buy a heatsink from RS or wherever. If the heatsink is bigger in area than the device it should have a low enough thermal resistance for your application (unless you then wrap it up i foam!) You might find a CPU heatsink that could be adapted.