Mini Stove > Cabin job.

[ProDave]

4 minutes ago, saveasteading said:

Why not now? Then I can answer to say I think it would be good fun, but not efficient or much use to you.

(payback 50 years?)

That's it, it needs to be made at almost zero cost out of stuff I have already.    But no point designing it yet, I don't want ot to be built on @Onoff timescales.

[saveasteading]

19 minutes ago, ProDave said:

stuff I have already.

I took the working motor out a broken Aldi strimmer yesterday, because I could.

Should I drop it in?

Could power a set of fairy lights, and your burn would look magical at night.

 

It would be fun though.

 

It seems that a motor to create electricity is not well suited to small-scale water power because of the speed (lots of gearing needed).

Yet water mills work well. I assume this is a torque thing, and I never really understood torque.

[SteamyTea]

On 15/04/2022 at 19:17, saveasteading said:

I assume this is a torque thing, and I never really understood torque.

It is easy.

Force at a Distance, hence Nm. Remember that acceleration is a change in speed or direction.

 

Another way to look at is is as a change in power.  Taking an automotive analogy, for any given amount of power, on a dead level road, with constant weather conditions, you may find that when the motor delivers 20 kW, the car will do say 40 km/h, at 30 kW, 50 km/h and at 40 kW, 55 km/h.

Torque is the motors ability to accelerate the car.

The reason it can seem confusing is because we tend to use RPM, when we really need to use Radians/second as that is a natural ratio.

https://www.engineeringtoolbox.com/work-torque-d_1377.html

 

Or just use the below fudge, it is good enough.

Torque (N.m) = 9.5488 x Power (kW) / Speed (RPM)

Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488

Edited April 17, 2022 by SteamyTea

[joe90]

I remember Dick Strawbridge built a water wheel years ago in his Cornish house, used a alternator but needed a 80:1 gearbox to get the revs, luckily he found one. I would have thought an 80:1 via a chain set would loose less power 🤷‍♂️?  (I wish I had running water at mine.)

Edited April 17, 2022 by joe90

[Onoff]

On 15/04/2022 at 19:17, saveasteading said:

and I never really understood torque.

 

Look at a set of spanners, they're all different lengths.

 

I believe this comes from years back. The idea being the average man, putting the average force "F" on that particular spanner, puts the correct 'ish torque on that particular sized nut. Length of spanner "D" being the variable. As said above Torque = Force X Distance.

[saveasteading]

6 hours ago, SteamyTea said:

Force at a Distance, hence Nm

Spanners, yes, but why does a diesel engine have more torque than a petrol engine, please?

 

Re the length of spanner thing.

In erecting steel buildings there was a strict rule from our suppler not to use torque spanners, but to use 'turn of the nut'.....'after full resistance is achieved, apply a half turn'.

The supplier gave up on this reluctantly, eventually and agreed to the use of torque wrenches.

I think the issue was that torque wrenches were over-sized for the nut (as described by OnOff above) and generally turned up to 11.

It was something I hadn't really thought of (and neither had most of the industry) that a bolt could be overtight and fail, or just tight enough and hold up a huge building.

Then once there was a recall by the bolt manufacturer....change all 40mm bolts at the haunch of an erected and operational warehouse.   what fun that was. 

 

[Onoff]

9 minutes ago, saveasteading said:

Then once there was a recall by the bolt manufacturer....change all 40mm bolts at the haunch of an erected and operational warehouse.   what fun that was. 

 

 

 

Been there done that, well on a similar vein. Instructed to change all the fixings because of believed hydrogen embrittlement. Without a crane we had to cut the old ones (pointing down) out. New ones were fitted pointing up. Couldn't use a grinder because of the roof finish so had to use a sabre saw. Got started and the manufacturer decided we didn't have to change the bolts in fact. 

[SteamyTea]

52 minutes ago, saveasteading said:

why does a diesel engine

A very good question.

An ICE is a spark ignition engine.  Fuel/air goes in, gets compressed, and at the right time, ignited by the spark.  Now the fun starts.  The temperature rises extremely fast, closely followed by the pressure, THEN the piston starts to move.  There is a slight bit of combustion happening as the piston moves down the bore (flame front and all that, why Wankles are hopeless on fuel economy), but basically the temperature and pressure rises at the very start of the stroke, then rapidly decreases.

Diesels on the other hand, limit the initial amount of fuel that is injected, this is ignited purely by the temperature of the compressed air.  As the piston moved down the stroke, more fuel is injected, keeping the flame front alive, this keeps the temperature and pressure high for a greater amount of time.

It also means that when the crank is 30° either side of 90° from TDC, on the ignition cycle, combustion is still happening, this is the crank position that allows most dynamic torque to be produced.  Diesels are often referred to as 3 stage combustion.

There are also differences in air delivery pressure and temperature, bore/stroke ratio, gearing etc.

 

Gasoline engine

 

Diesel Engine

 

Edited April 17, 2022 by SteamyTea

[dpmiller]

Diesels run un-throttled and have a much higher compression ratio, too...

[saveasteading]

4 hours ago, Onoff said:

we didn't have to change the bolts in fact. 

 

How strange you had the same issue.

Although it was a pain, we did get paid for it.

 

Another building had the same batch, but it was a sports hall and all the bolts were by now concealed by an inner lining of boarding.

I told them this was difficult and perhaps to check the tolerances of the bolts in our situation. No. ( I think their insurer had issued a blanket instruction)

Then I told them the cost of closing the facility, stripping the walls and replacing , on top of the bolt replacement.

Apparently there was enough spare capacity in the bolts that it was ok after all.

 

Good though, that the bolt supplier was so thorough, and it does provide total confidence in the product.

 

Bolts facing down! Naughty.

 

[saveasteading]

3 hours ago, dpmiller said:

Diesels run un-throttled and have a much higher compression ratio, too...

Glad to hear it. What does that mean (as simple as you like).

[saveasteading]

3 hours ago, SteamyTea said:

A very good question.

After that impeccable answer, I will have more questions about the way the world works.

None for now, but this sort of thing.

 

Why do my led bulbs glow when the switch is off , and flies circle lights that are off?

How is it that a self-build project can cost half of that run by 'professionals'. (I know this one actually.)

Why do 2-way lights not short and fuse?

Why do materials and goods here cost the same in £ as Europe pays in Euros?

 

 

 

 

 

 

 

 

[Onoff]

13 minutes ago, saveasteading said:

Bolts facing down! Naughty.

 

 

Not at all if there's a chance the thing on the roof can still stay in place if the nut falls off. Better a nut drops from height than a bfo bolt.

[SteamyTea]

33 minutes ago, saveasteading said:

3 hours ago, dpmiller said:

Diesels run un-throttled and have a much higher compression ratio, too...

Glad to hear it. What does that mean (as simple as you like)

Diesels are lean burn engines. The power output is varied by making the mixture of air and fuel either fuel heavy (more power) or fuel light (less power). Petrol engines have the same air/fuel ratio across the whole power band (stoichiometric).

You may have noticed that when some diesels pull away, or accelerate heavily, they smoke. This is unburnt (wasted) fuel. No extra power is produced at the smoke limit.

 

There is a fine balance, for all combustion, on the air/fuel ratio to get maximum power at any given moment. This has got more complicated with the introduction of turbo charging. This has the same effect of putting in a larger normally aspetated engine i.e. you get more fuel to burn in more air.

Turboing has the advantage that it is also scavenging energy that is usually wasted from the exhaust, and you can have a better bore and stroke ratio i.e. reducing the total surface area to reduce heat losses.

The compression ratio has two functions. The higher it is, the more air is heated up, this aids combustion in a diesel. But go too far and you get pre ignition. This is when the compressed air is hot enough to ignite the fuel, before the piston has reached the top (TDC). Fuel in both types of engines is actually present before TDC, this is to allow for a few milliseconds that it takes for combustion to start.

To get around this pre ignition problem, fuels have ignition retardants added, octane and cetane are the rating numbers for gasoline and diesel respectively. Low numbers burn faster. This is why old American cars had large engines, their fuel was at a lower octane rating (this does not mean lower energy density or quality), so lower compression and lower power. But also lower emissions of CO2 and NOX.

It is the higher compression ratio of diesels that has caused the NOX problem that VW cheated on. By reducing turbo boost, and running the engine cooler while being tested, less NOX is produced, there is less power, but they does not show up during a static tests.

Ideally an engines power is measured as Specific Brake Power. All this means is how much power comes out for the amount of fuel put in. It leads to some interesting numbers for large engines, which are generally more thermally efficient at part load.

 

Tried now and it is getting dark, time to head home from the very end, almost, of the country.

 

[saveasteading]

4 hours ago, Onoff said:

if the nut falls off

Neither the nut nor the bolt should fall off.

 

But if the bolt is fitted from below then it is obvious by visual inspection that there is a missing fixing.

Not so easy to see if the bolt is popping through from above, with no nut. 

Fitting the bolt from above is easier of course, thus more likely for a nut to be omitted.

A subtle benefit but worthwhile.

[Gus Potter]

23 hours ago, SteamyTea said:

Diesels are lean burn engines.

Steamy.

 

Just a quick note to say thanks for your great posts, really enjoyable reading, learnt a lot from them so thanks.

 

Also thanks to everyone else that has chipped in.. it's a long list but thanks all from me.

[SteamyTea]

4 minutes ago, Gus Potter said:

Just a quick note to say thanks for your great posts, really enjoyable reading, learnt a lot from them so thanks

Just goes to show that I did not totally waste my time studying automotive engineering.

[Gus Potter]

Just now, SteamyTea said:

Just goes to show that I did not totally waste my time studying automotive engineering.

Definitly not. For me the cross fertilisation between different disciplines is inspiring.

 

Thanks again.

[SteamyTea]

11 hours ago, Gus Potter said:

For me the cross fertilisation between different disciplines is inspiring.

This has been an ongoing debate in education.

Some educationalists think that courses should be developed to a more specialised areas i.e. Forensic Science, Renewable Energy, while others think a more general education is better i.e. mathematics, Physics.

This gets much harder with the arts and humanities i.e. painting or sculpting, early learning or phycology.

As part of my post grad in education, I had to observe a lesson in the art department, it was in textiles.  I pointed out that it was really engineering and technology, but the 4 students thought it as art and craft (incidentally I had 30 IT students when I was observed, and only 26 working PCs, that is a challenge, peer learning comes to ones rescue in that situation).

 

My view is that with the sciences the first year should be the basics, second year students split off into interest groups i.e. chemistry, software, botany.  Then the final year should be projects.

Take my first degree, we had I think, 6 or 7 subjects (we turned down vehicle electronics, but it was over 40 years ago), second degree I think it was 18 subjects in all, including my favourite, environmental economics (I can put a price on nature, it is easy with proper surveys), and philosophy (which at the time I thought was nonsense, but looking back, was useful, should have been in the first year). 

 

 

Everyone should be taught Thermodynamics, Laws of Motion, the SI units, Laws of Indices and Algebra, along with English (or whatever language in your country).

International Sign Language would be useful at primary school for a few years, it is the closest we have to a universal language (I am a BSL user, though out of practice now).

 

There should be a 'how to deal with OFSTEAD inspectors' as part of the PGCE, it is all that college managers seem to care about.  I have seen really good lecturers go to pieces and leave because of an over promoted, useless colleague, has been put in charge of internal inspections and totally missed the point of education.

[zoothorn]

Hi chaps, hope y'all had a good easter.
 

I'll go through the water wheel info/ replies/ natter later.. interesting ( mention of Dick strawbridge & my ears are alerted).

 

Buying my flue sections today. Thanks PeterW for roof collar suggestion- buying today. Tricky to get compatibility of sections. A battle!

 

Thanks, zoot.

 

 

 

 

 

 

 

 

Edited April 19, 2022 by zoothorn

[joe90]

18 minutes ago, zoothorn said:

adding cowell from same place is another £50

Why not just add a flat plate above the pipe (to stop rain ) pop riveted on straps both sides 🤷‍♂️ Not as nice looking but cheap!

 

or https://www.ebay.co.uk/itm/401747290406?

Edited April 19, 2022 by joe90

[zoothorn]

Just now, joe90 said:

Why not just add a flat plate above the pipe (to stop rain ) pop riveted on straps both sides 🤷‍♂️ Not as nice looking but cheap!

Hi J. That's a damn good idea! Im thinking maybe go sensible/ lump it & buy the £50 cowell now. I miscalculated & its £200 all bits.. not £250. Im exhausted with calls & www searching.
 

The issue's been getting the 4 bits compatible. Plus very few places actually sell 4" single AND twin. So you cannot take chance of 1 from here, next bit from there. It seems.
 

And adding your idea to twin wall top... might not be so simple. If it was single.. I'd go with your idea.

 

Jeepers this has been a trial. Hoping the actual install will not be. Thx zoot

 

 

 

 

 

 

[zoothorn]

Im needing clarity here in fact.

If I have 4" twin wall top section, the cowl, one would assume, would go on the outside. Not tucked into the inside. Anyone know if this is correct?
 

Now I know I have -one- metal locking band " spare " ( both my adaptor, & my twin bit come with one locking band each, & the adaptor > single flue area push fit... so I have one band spare. I think). So I can use this to clamp a cowl to my twin wall top -IF- that is, the cowl fits over the outside.

 

If the outside diameter of my 4" twin wall, is 150mm ( known to be )... do I therefore, simply need a 5" cowl?

 

If this is so ebay ones £16. And I could save £34.

 

Any ideas?

 

 

[joe90]

18 minutes ago, zoothorn said:

And adding your idea to twin wall top... might not be so simple. If it was single.. I'd go with your idea.

You said the twin wall was 150mm outside diameter and the one I linked too is also 150mm ???? What’s complicated (at less than half the price 🤷‍♂️

[zoothorn]

Just now, joe90 said:

You said the twin wall was 150mm outside diameter and the one I linked too is also 150mm ???? What’s complicated (at less than half the price 🤷‍♂️

Because apparently I need a 4" cowl, according to the company ( info of which I cannot make immediate sense of )... plus... the product info says "our xyz bits are only compatible with each other" on each bit bookmarked to buy.

 

But I might just simply need a 5" cowl. Because the outside ( 4" twin wall flue ) diameter is 5"  And so the company is wrong, & im right. That just cannot be likely.

 

zh