Member postings for duncan webster

Hardening steel makes it stronger, but not stiffer. The two are often confused especially by journalists

My response was in answer to Nigel's suggestion which used solar water heaters. If you're starting with electricity, I wouldn't mess with water

Thanks for that. According to the chap I'm going with, the bus takes an circuitous route and so is slow, all eating into the limited time we gave at the exhibition, especially as some of it will be taken up by a boring talk by some old fogey (me)

Water has a far higher heat capacity than glass, by a factor of ~5 so just use a big tank of water. The only advantage of adding glass to the equation is it's heavier, so takes up less volume, but only by about factor 2.5 even for solid, less for crushed, so I think you'd be better of with just water. The potential advantage of electrical solar panel is you can get a higher temperature, so need less mass, like a storage heater.

Not all single phase motors have start capacitors, the one on my ML7 didn't.

Artificial intelligence is no match for human stupidity

Two of us going to MMEX Friday by train, arriving Leamington 11:15. Looks like we'll have to get a taxi as there is no courtesy bus, and the service busses are infrequent. If anyone is arriving at a similar time and wants to share with us send me a pm

Just had this pop up in my inbox, Windy has told us about it before, but there might be something in it

IMechE

Just had this pop up in my inbox, Windy has told us about it before, but there might be something in it

IMechE

I hadn't even looked at the actual stay diameter in KNH book. He actually recommends 6 or 5ba for 1/2" spacing, using 6ba and 120 psi gives 5286psi stress which is well over KNH, Aus and my figure. Even using 5ba we get 3977 psi, again above Aus and me.

so who are you going to believe, national standards (both UK and Aus) or KNH? I've no idea where KNH got his figures from.

Reading KNH again after many years, he quotes stay pitch for pressures of 100-120 psi, and then goes on to give a range for the required pitch. Perhaps this is meant to mean take the lower for 100 and the higher for 120, but he only quotes one figure for 16g, which makes no sense. In any case, if you plot the upper and lower figures for stay pitch against material thickness you get this

Bearing in mind that KNH only quotes to nearest 1/16" I'd call that fairly linear. I wouldn't expect to get close agreement with the Aus standard or my figure derived from UK standard.as KNH uses an acceptable working stress of 3125 psi, which is somewhat lower than UK or Aus

There is not and cannot be a relationship between tube plate thickness and barrel thickness. Require tube plate thickness is dependant on material properties, working pressure and stay (or tube) pitch.

I have given references to where formula for working out stay pitch can be found. There seems to be some reluctance to follow these up.

Purely by coincidence it was announced after tea that I had to go to IKEA to look at a bed for #1 son. Talk about the outer circle of hell! I am going to do my utmost never to go again, but if I am instructed by senior management I'll take the dog, it will be good exercise for him. At one point I threatened to just follow the fire exit signs, opening the fire doors along the way, but was talked out of it. They should realise that their ploy of making you go through the entire store actually puts people off. I'd willingly pay extra to a normal department store where I can go straight to the bit I want, and then leave. I thought the Trafford Centre was bad, but at least you can escape.

We have a high efficiency gas fire (balanced flue) in the room we use most. It claims 90% efficiency. Central heating goes on for a short time each day in really cold weather just to take the arctic chill off the rest of the house. I agree with SOD, if you put a jumper on 18C is plenty warm enough. I also wear my woolly hat, but then I'm bald on top so lacking insulation.

I use IKEA chopping boards when I want machineable flat plastic. They are about 8mm thick from memory. SWMBO actually like going there, I absolutely hate it. The way they try to make you go through the whole store is maddening.

Running significantly slow will reduce the effect of the cooling fan, watch out for overheating

I wouldn't use car batteries, they don't like deep discharge, Leisure batteries are the thing. As others have said, 1 300W solar panel won't give anything like that on an overcast winter's day, and it's only daylight for around 8 hours per day in midwinter.

This is just going round in circles. The Aus code and BS both have formulae which allow one to calculate the stay circle diameter for any thickness of flat plate once you've decided on a safe working stress. The Aus code has this for copper, and it is possible to derive one from the BS as I have done, coming to a figure remarkably similar to the Ausy one. If not confident of coming up with this stress, just buy the Aus code and have done with it.

Just because our boilers are smaller than big industrial ones doesn't make the calculations invalid. Some time ago I outlined a layout of tubes which would meet the Aussy code with 16g end plates, a couple of bits of copper about 3" diameter isn't going to break the bank.

Experiment is not required. The design codes are there. They are based on a mix of theory and experience gained in making and using many thousands if not millions of pressure vessels. They might need a bit of judgement to suit our particular needs, and this interpretation must then be checked, no-one is infallible.

Suitably qualified and experienced person