Robin2

The way I calculate it is as follows (my earler calcs were wrong by a factor of 1/2 ) 2000 rpm = 33.3 rps circumference of circle of radius 1m = 2x3.142 = 6.28m M/s = 209.26 Nm/s = 17787 = 17.8 kW = 23.8 hp Max Hp at 3000 rpm (assuming the same torque) would be 35.7 Because fuel consumption rises more sharply than speed mainly due to propeller inefficiency the consumption per mile will be lower at lower speeds. A car gets a firm grip on the ground and only suffers from increased air resistance as it goes faster.

Did you test the exact same fridge with nothing changed but the motor? If not, what you are saying is that low voltage fridges are better made - and would thus give a lower manufacturer's average annual kWh consumption figure. Your original comment was a criticism of those manufacturer figures. Ar you now saying that the manufacturers of 12v fridges publish more accurate annual consumption figures? Maybe they do!

I pressed "post" when I meant to press "preview" and then had to edit in public That's only true if you know WHY you would put a load in one direction or the other. I am waiting for someone to propose a convincing explanation of what the brackets and rings were designed for - perhaps someone has a very old photo showing them in use?

Well don't fight over it - that will just push the price up

Something wrong with the maths here. If the maximum torque is at 2000 rpm and there is 18hp at 2000 rpm then there can't be more that 27hp at 3000 rpm. Also (I hope my maths is right) 85Nm of torque at 2000 rpm = 8.9kW or 11.9 hp.

The only difference between a 230v and 12/24v fridge is the inverter loss which has nothing to do with the manufacturer's estimate of annual energy consumption.

So... After all that there seems to be a consensus that these brackets are the wrong way up and this is the correct way but there is still no rational explanation for either type. C'mon historians --- help

No problem!

This is actually 320 watt-hours over a 24 hour period, or an average consumption of 13.3 watts. I agree with Gibbo's comment about the unreality of the manufacturer's figures - though mine does not seem to be as bad as 50% worse. By the way are you using a fancy editor to create your posts or do you just enjoy the masochism of putting different font codes etc on each line?

If you look at the rudder on a butty you will understand the problem. The normal rudder on a modern powered narrowboat is far too small to have any useful effect without the flow of water from the propeller. The rudder is useless when reversing because the water flow into the propeller is spread over a large area and is not focused on the rudder.

Vibration has little to do with efficiency. It depends on how well the designers balanced the engine. With anything less than 6 cylinders there is going to be a lot of vibration and you are quite right to say that it is worst at certain engine speeds and smoothest at others. If the designers bothered I would expect them to try to minimize vibration at the speed the engine would usually operate - probably closer to full power than maximum torque. However they may in practice be more concerned to minimize vibration at maximum rpm so the engine does not break in the warranty period. None of this is relevant for a boat unless the boat builder also carefully (or accidentally) matched the gearbox and propeller to obtain a suitable cruising speed at the smoothest engine rpm. What cruising speed should he choose? In practice it could well be that when the engine is at its most efficient point the boat goes too fast and wastes power, even though the engine is creating it efficiently. Alternatively if the gearbox and propeller are carefully matched for cruising the engine may not be able to attain full power and the boat would be underpowered on rivers. The short answer is that the slower a boat goes the more mpg you get. You need to balance fuel against frustration.

Jeez ... all I meant was that my mistake was not unreasonable. I knew from the first glance that they are not actually suitable for lifting - but they might have been poor copies of brackets that were intended for lifting. The pictures from the old boat suggest that the SH version is just a fanciful ornament. And (referring to other comments) I'm still not convinced that the downward facing brackets were simply intended for convenience when mooring. That usage would not require them to be angled downwards, or to be as strong. It could well be that they were designed for another purpose but were used as convenient mooring points.

MPG measures the efficiency of the complete package taking account of power losses in the transmission, tyres etc and the effect of air resistance. The huge improvements that have been achieved are partly because they started from a very low base. The relationship between 2 litres and 163 bhp says nothing about efficiency. Car engines are not designed to run continuously at their maximum power whereas the Beta and Isuzu etc diesel engines are - which is why their rated power outputs are much lower. I would not expect much difference between the BMW and Beta engines in terms of specific fuel consumption - grams/kW-hr. If BMW have figured out a significantly better way the others will quickly copy them. Most of them use Bosch injection equipment anyway. I previously had a workshop manual for a Yanmar engine and I was amazed at the fine tolerances to which it was manufactured. I'm sure the Beta (Kubota?) and Isuzu engines are as good. ETA why is it only after posting that you spot the typos?

Gibbo selected a small piece out of this. Let me focus on a different piece. The bit I have highlighted implies that the fridge consumes 336 watts. I'm sure you know this is far too much. Fridges are more likely in the 50 to 100 watt area while they are running and they only average maybe one third of that. Now if the above mentioned 1.4 amps is at 12v (rather than 240) it gives an average of 17 watts or about 50 watts when running if it runs for 20 minutes every hour. On this basis I assumed that all of the amp-hour figures that Julynian quoted were at 12 volts, not 240v.

I moored near Sainsbury's for several days earlier this year without any trouble. I didn't try the area near Tesco's as that's a bit closer to the pubs. Tesco's is probably a little closer to the SVR but there's not much in it. Enjoy the trains.

There seems to be circular logic here... If you have an unlimited budget (for diesel, solar panels or batteries) you can blissfully ignore the watts and amps. If you want to get value for money they are unavoidable.

Efficiencies above 35% will be difficult to realize in practice. From reading the reference in the wiki article the higher efficiencies were in bigger engines. I think the low fuel consumption figure at the top of the article refers to a slow speed diesel in a large ship or power station. Also bear in mind that engines are most efficient at a particular RPM and in boats and road vehicles it is unlikely that the engine will be working at exactly the right speed. For the Isuzu 3LB engine the specific fuel consumption varies between about 250 and 285 grams/kW-hr. That is an efficiency range of about 33% to 29%. In a boat the greatest inefficiency is the propeller - even the best propeller - because it must slip in the water to create thrust - unlike a wheel which is in firm contact with the ground.

If you have space for more solar panels you might get more watt-hours for your £ by buying an extra panel rather than an mppt controller. And that would not prevent you from buying the mppt controller later. The economics require careful calculation unless investment funds are unlimited. I have 3x80w panels that I got recently and I have no space for more - or I'm not willing to give up space for coal and bicycle. I am thinking carefully about mppt in my own perverse way.

Thats why I said "pretend" in post#4 I'm not convinced. I can't see them being more convenient than a bollard at the bow or stern. To be useful at short notice they would need to have a rope through them all the time and the rope would get in the way. From that point of view an attachment on the roof and a rope on the roof would be better. Also I don't believe the working boats were managed so badly as to need anything done "quickly". They look like the sort of connections you would need if you wanted to tie down the whole narrowboat e.g. as deck cargo on a bigger boat - but I don't imagine that was done very often

Based on similar data these are the average daily amp-hr figures (at 12v) for each month for a 400 panel (assuming my spreadsheet is ok). J 21.4 F 42.0 M 72.3 A 118.7 M 157.3 J 160.0 J 162.0 A 131.0 S 93.0 O 52.7 N 26.1 D 15.3 For planning purposes I believe these should be significantly reduced to allow for such things as being in a sub-average year, being moored in shade some of the time, birdsh*t on the panels etc etc.

I know, but that was not the point I was making. I had hoped to explain that the panels would not produce 400w in full sunshine unless the controller properly matches them to the batteries. I think Julynian understands the need to derate the maximum output (from 400w or from 260w) to allow for the UK weather.

I feel justified in my original supposition that the SH ones were for lifting. I'm still not clear what the back end rings (as shown in the photo) were for. From the angle they're at they are clearly meant for a downward and outward load - such as fixing the boat to a mooring ring onshore. But doesn't the boat have cleats or bollards at the stern? And why would they design the mooring point so high up on the boat if it was meant to connect to something low down?

I did mention this in post#5

Do what you want ....... it's your money. If you're in the habit of spending large amounts of money on items which you yourself are not experienced in evaluating and it doesn't affect your ability to sleep at night, raise fears regarding your own safety or that of your family and friends or put a question in your head regarding how easy it will be to sell on afterwards then why break the habit of a lifetime? In what way is your comment related to mine? If not, why make the link?

I presume when you mentioned 27amps in your first post you meant 27 amps at 12v, not 27 amps at 230v. You are using your terminology incorrectly - which may be adding to the confusion. Something that consumes 1 amp will consume 24 amp-hours in a day. One does not say "amps per hour" as that is meaningless. The correct expression would be "amp-hours per hour" but of course that is just "amps". I believe it won't work to average the power consumption of your washing machine over several days. You need to do separate calculations for the days when you use the machine and the days you don't because the washing machine will seriously deplete your battery on the day it operates and if that is followed by several dull days you may found your battery SOC much lower than you bargained for. You should be careful in interpreting the watts from your solar panels. What is the nominal voltage of the panels - lets assume its 20v to make the maths simple. That equates to 20 amps for 400 watts. If you have an mppt controller that should, in theory (but I have no practical experience yet) equate to 31 amps at 13v into your batteries. And I would assume at least a 10% efficiency loss from those figures. If you don't have an mppt controller you will only get 20amps into your batteries (at 13v) or 260 watts.