What did you do today (2015)

[MuzzerParticipant @muzzer]

Posted by Bazyle on 08/11/2015 17:52:04:

Still used in some big installations like a winter Olympic toboggan run right through some small town recently. Locals a bit worried about what will happen when it leaks.

Edited By Bazyle on 08/11/2015 17:55:19

See for yourself. Still used quite widely it seems. Surprised they don't have gas detectors and evacuation plans, particularly given how popular ice sports are in North America as a family activity.Imagine if this had happened during a busy hockey game….

[Neil WyattModerator @neilwyatt]

I think I mentioned earlier that the best change you can make to any older house is to cure the draughts. Be ruthless – even after years I am still finding draughts in our 1937 semi!

As for gas fridges, all three camper vans we have had have had gas/12V./240V fridges! They just have three different ways of heating a small loop of pipe, no compressor so very simple and reliable (once you have the damn thing alight!)

Neil

[AjohnwParticipant @ajohnw51620]

Ours was built in 1911 and way too many draughts to even think about doing anything about it. Anyway a certain regular amount of fresh air is desirable in my view.

John

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[“Bill Hancox”Participant @billhancox]

I watched a few videos on lathe work today. Having watched numerous productions over the years, I was amazed that I finally observed a lathe operator thoroughly cleaning off his chuck jaws before he inserted his work. Although I always do this myself, this was the first time I witnessed it on a video.

Bill

[Mick HenshallParticipant @mickhenshall99321]

I'm having a good day-whilst rehanging my front room curtains managed to knock me 32" smart tv over and trash the screen, also broke a topslide casting where it bolts to cross slide on my shaper, I have a leak in the roof of outside store and I can't find the source, and I just cleared the living room ready to decorate I think I'going to quit while I'm ahead (sound of cans being opened)

Mick

[NJHParticipant @njh]

Mick

Go back to bed and try again tomorrow!

Norman

[Ian S CParticipant @iansc]

My Sister and Brother in law had a fridge on their boat that could be run on LPG or 230V AC or 12/24 V DC. years ago we had a fridge that ran on either kerosene/paraffin, or 230V AC.

As far as heating goes, for me it's a toss up between Air con, or a pellet fire, both require an input from the power company, the pellet fire has a small motor that drives the worm to feed the fuel pellets to the grate, and an element to ignite the fuel to start up. Just thinking.

Ian S C

[BazyleParticipant @bazyle]

Be wary of pellet stoves. If the pellets are substandard, old, or cheap and break up in the auger it jams and burns out he motor. Not so bad for an engineer but dents the fuel price advantage, if any, wrt other sources.

[Jon GibbsParticipant @jongibbs59756]

For those unfamiliar with these things, the gas fridge is another area where Einstein contributed to progress…

**LINK**

We've had various caravans over recent years which used ammonia cycle fridges, but our latest VW campervan has a really efficient 12V compressor fridge.

Jon

[MuzzerParticipant @muzzer]

Posted by Neil Wyatt on 08/11/2015 21:34:03:

I think I mentioned earlier that the best change you can make to any older house is to cure the draughts. Be ruthless – even after years I am still finding draughts in our 1937 semi!

Of course, current UK building regulations (part F) mandate a minimum permeability for new builds, to ensure a degree of circulation, particularly with the advent of sealed double glazed windows. Admittedly that isn't necessarily the same as draft exclusion but ultimately limits the reduction in air movement (deliberately so).

In contrast, the Mercans and Canadians take a different approach with their building "codes". They seem to target the "100% sealed house" and home inspectors will actually test houses to ensure a minimum standard is met. They mount a large calibrated fan in one of the outer doorways and measure the leakage against a (modest!) pressure head.

Funny how the different building standards bodies have ended up implementing quite different philosophies.

[Mick HenshallParticipant @mickhenshall99321]

Good advice Norman ZZZzzzz!!! Hic

Mick

[Michael GilliganParticipant @michaelgilligan61133]

Glad to see several responses regarding absorption refrigerators, but; going back to my earlier speculation … does anyone know if the principle could be scaled to make a silent-running Heat Pump ?

MichaelG.

[JAParticipant @ja]

Posted by Michael Gilligan on 09/11/2015 14:18:54:

Glad to see several responses regarding absorption refrigerators, but; going back to my earlier speculation … does anyone know if the principle could be scaled to make a silent-running Heat Pump ?

MichaelG.

I see no reason why it should not be possible. After all it is the same thermodynamic cycle.

JA

[Gordon WParticipant @gordonw]

You could run a heat pump from a stirling engine- there are all sorts of combinations possible, some in production, I havn't time to read it all.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JA on 09/11/2015 14:26:37:

Posted by Michael Gilligan on 09/11/2015 14:18:54:

Glad to see several responses regarding absorption refrigerators, but; going back to my earlier speculation … does anyone know if the principle could be scaled to make a silent-running Heat Pump ?

MichaelG.

I see no reason why it should not be possible. After all it is the same thermodynamic cycle.

JA

.

Mmmm …

That was my starting point; and the very low noise-pollution seems attractive.

So I guess the real question must be:

Why don't 'they' do it ?

MichaelG.

[MuzzerParticipant @muzzer]

Never really understood how absorption refrigerators worked but there's a dummy's guide here for people like me. Seems that there needs to be another liquid present for the gas to be absorbed in (the clue's in the name I suppose).

No idea of the theoretical answer to MichaelG's question but presumably the lack of any examples in the wild indicates some practical limit eg the required temperature difference. Most of the examples seem to use hot heat sources like flames and exhausts whereas ground and air source heat pumps operate with relatively limited temperature differences. Perhaps a solar heat source would work but the mirror array would need to be pretty large to focus the sun passively throughout the day – without requiring any moving parts.

[KWILParticipant @kwil]

Once used a Sterling Cycle engine to cool down (ie as a heat pump) an IR detector (in a very low vacuum) to a ridiculously low temperature. When you switched off the electric input, it often ran on as the cold end warmed up.

[Neil WyattModerator @neilwyatt]

> Of course, current UK building regulations (part F) mandate a minimum permeability for new builds, to ensure a degree of circulation, particularly with the advent of sealed double glazed windows. Admittedly that isn't necessarily the same as draft exclusion but ultimately limits the reduction in air movement (deliberately so).

My understanding is that the permitted permeability rates equate to something like one mousehole…

Neil

[Frances IoMParticipant @francesiom58905]

Michael G : seen the Peltier units used in small dehumidifiers (tho water extraction seem small thus think the actual Peltier component must be quite small) however suspect much of the noise is due to the fan to move considerable amount of air over the external and this would be considerably worse if the cooling unit had only a small surface area

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Frances IoM on 09/11/2015 22:06:24:
Michael G : seen the Peltier units used in small dehumidifiers

.

Thanks, Francis … but Peltier units are not what I had in mind.

MichaelG.

[Ian S CParticipant @iansc]

I think it was Coleman the made a small fridge with a Stirling cryocooler, don't know it they are still available.

On completing a small unpressurised Ross Yoke ALPHA type hot air engine, I powered it up with another of my motors of similar power, and after a 20 minute run the hot cap was frosty white, and the thermometer was at -20*C, driving it with a more powerful motor would no doubt reduce the temperature more.

If you deside to build a Stirling Engine to run as a cryocooler, the weight of parts is not so important, nor is friction, in other words it should be built some what more robustly with a heavier crankshaft, con rod etc.  Even a fairly small one, unpressurised would be best powered by something like a 1/4hp electric motor.  Good cooling is very necessary. This would be for a motor the size of my Ross Yoke motor, 20 mm stroke, 35 mm bore.  after driving the motor I noticed that the 1/4" dia crankshaft was bent, and the flywheel wobbled quite badly, it did straighten to a little wobble,  a 3/8"/10 mm would be a minimum size.  Conclusion, it wouldn't cool a fridge the size of a shoe box.

Ian S C

Edited By Ian S C on 10/11/2015 10:33:04

[Bob RodgersonParticipant @bobrodgerson97362]

Today, I got this thing running. It was reluctant to start because the carburettor is not the correct one for the engine and also the spark plug is not quite long enough reach. I like to run engines I restore because it can throw up the odd problem that you won't find without running.

This one showed the pressure relief valve piston to be leaking so I will have to take a look at it and maybe make a new one with Teflon seals. Also the exhaust valve spring is almost coil bound, probably because when I made a new rocker arm I got the distance between pivot point and push rod cup slightly too long thus giving a little more travel than the original one, however the engine is low compression so there is no danger of the extra travel causing collision with the piston. I might grind about 3/32" off the spring just to be sure. Sorry about the repeat bit.

Edited By Bob Rodgerson on 10/11/2015 17:13:35

Edited By Bob Rodgerson on 10/11/2015 17:14:52

[duncan webster 1Participant @duncanwebster1]

I spent about 2 hours trying to find the fault in some Arduino softawre, and eventually found it was a hardware problem, blown transistor. Don't you just hate electronics, at least if something mechanical breaks it's obvious

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by Ian S C on 10/11/2015 10:13:59:

I think it was Coleman the made a small fridge with a Stirling cryocooler, don't know it they are still available.

Somebody seems to be making them for integration into units like this **LINK**

I bought a few for some metallurgical research in a former life – they go down to -90C in lab air. They're helium pressurised and, as KWIL implies, I believe they were developed for cooling IR detectors in satellites.

Rod

[John HaineParticipant @johnhaine32865]

One of the best bits of engineering I have ever seen was a unit the size of one of those "table-top" pump thermos flasks they serve coffee in, which was a superconducting filter to use in cellular base stations. The superconducting bit was in a small square box at one end with 4 coax connectors; the rest of the unit was a single stage pressurised helium oscillatory Stirling Cycle refrigerator. It was driven using a voice coil to the "piston", excited by 60 Hz AC. The voice coil (in a loudspeaker-like magnet" compressed the gas whilst the resonant oscillatory displacer lightly coupled to it to vibrate in quadrature. The result was a temperature low enough to achieve superconductivity in the thin film filter resonators. I'm familar in my day job with RF filters and how they work, but the refrigerator just blew my socks off! A real bit of yankee know-how.

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