MtB

Have a guess....! :)

The widebeam on the 48 hour moorings here hasn't moved since November last year, so £50 of diesel is working out just fine for them.

Is this the Johnson pump you are suggesting? https://www.midlandchandlers.co.uk/products/johnson-compact-water-circulating-pump-12v-15lpm-16mm-10-24501-03#

Not sure what Lidl having lemons in stock has to do with living afloat, either!

Spoken like a true retired or jobless boater! There is no way I could hold down my job without a vehicle.

In addition, the actual motive force produced by a little 15mm 12Vdc will be hundreds if not thousands of times bigger than the motive force of natural convection. No matter how clunky it might look.

This is a good point. When internal combustion engines came along the most natrual thing to do would have been to experiment with ways to fit them into horse boats. Not design and build a whole new motor boat from the keelson up! So the first motorised 'butties' where probably horse boats right back when engines were first invented...

However, noticing the thread title I see the OP wants 12Vdc.... There might be the odd circulator about with 3/4"BSP threads.

Me!!

Yes this will look clumsy and inappropriate but does it work?! 'Not liking the idea' of it is not a good reason to change it in my personal opinion (and opinion is all it is). More practically, I don't think I've even seen a 12Vdc pump with connections larger than 1/2"BSP. Pumping fluids takes ENERGY and replacing a low energy pump that works with a bigger one that also works sounds a daft idea to me. We here seem to be assuming you want a 12Vdc pump though. If you actually want a 230Vac pump then pretty much any central heating circulating pump will do. You can fit them with 22mm or 28mm isolator valves but beware, they typically draw about 50W all the time they are running.

Someone with a short-and-thin boat might!

My guess would be it took off in the mid 70s when butties/horse boats were two a penny and no-one knew what to do with them. First was probably in the 60s.

Use a tape measure? It looks to me like about 1200mm x 600mm, which would be about 120W. Pretty sure my 100W panels are about 1000mmx 600mm (without measuring them!)

It looks on careful inspection to be made of wood rather than steel, and that mounting bracket looks dead flimsy so the whole thing must have little strength. My money is on it being one of a pair, or three even, with the other(s) fitting into similar bracket(s) for bunting up to decorate the boat for rallies, events etc.

That's unfortunate. It's a bit like a pub here. Conversation wanders off topic easily, and just as easily returns. IanD and I were just messing about with one such diversion, about how the Sharrow prop is another novel method of propulsion and the photo shows it appears to share some of the features of a Mobius Strip. Your contributions here are greatly appreciated.

I was only thinking earlier that it hasn't rained today so far, so stand by for low wter level warnings and a hosepipe ban. In fact did the hosepipe ban from last year ever get lifted?

Well it would wouldn't it, as a Mobius wosname only HAS one side!

I think that should be re-named the "Mobius Propeller".

I suspect it all gets quite expensive compared to a stern tube and a propeller and you know what cheapskates most boaters are. I also have my doubts about how it copes with ingestion of a duvet or a sari or the chunks of rotting tree trunk that lurk in the mud.

Yes a land-locked plot 10m x 80m with no access other than from the water's edge, it appears. £120k for that seems awfully optimistic!

Thanks to you both. The film demonstrates why these cone drives are so difficult to describe in words! So currently it looks to me as though the closest device to a Hotchkiss cone drive that most people are familiar with, would be a centrifugal pump. Higher pressure water at the perimeter of the cone gets directed back into the river or canal, pushing the boat along.

Quite possibly will, actually! Most water pumps cut in and out around 2 Bar and a Bar is 15psi approx. So 2 Bar is 30psi and the upper bound for the pressure switch to turn off could easily be approaching 35psi. https://www.force4.co.uk/item/Jabsco/Par-Max-3-Water-Pressure-Pump-40PSI/2A0H Edit to add: I now notice the OP specifically states he has a 25psi pump!

Quite so. And insurance companies would not insist on a survey if it was of no value to them. To assert they require surveys because someone at the insurance company has a mate who is a surveyor (jobs for the boys) is simply risible. They may not decide to sue any individual surveyor but insisting on seeing surveys of old boats before insuring them will, on a statistical basis, reduce the probability of a claim on any one policy, thereby making the whole business strategy more profitable.

I'm probably being thick but despite this and other threads on Hotchkiss cones, I still can't quite figure out the nature of them and how they work. None of the diagrams or written descriptions seem to get to the core of what they do to generate a motive force. Do the cones move or are they stationary? Is there still a propeller involved? Inside the cones perhaps? Or a spiral like an Archimedes screw perhaps? What IS the mechanism by which they shift water and move the boat? Thanks for any illumination!