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[kno3]

Dear all, I'd like some opinions on the Saito V4PR and suitable boilers.

I have one and after testing it it turned out that it likes to rev quite a lot, I'm estimating 3000 RPM. As soon as I get a suitable device I'll try to measure it.

Well, I'd like to use it in a fast boat. So I'd like to know which hull shape would be the most suitable, and if you could also recommend a small, lightweight yet high performance boiler for it?

[kiwimodeller]

Kno. I have had one for several years in a Windermere launch hull 44" long. I think it is a great little compact engine and of course being 4 cylinder it is very reliable as far as starting in either direction is concerned. It also has the advantage of being able to be reversed and throttled with the one servo. If my memory serves me correctly the factory info says it will rev to 4000 but I have a big prop on mine and it happily slogs away at quite low revs. I have a Cheddar 3" dia boiler setup which I feel is a bit small. If I bring the boiler up to 40PSI before launching the boat fair flies for a while but the boiler will not hold that pressure unless I throttle back fairly drastically. However the pressure settles at 20PSI and she will hold this all day and run well for 20 to 30 minutes. I do feel that either a bit longer or a more efficient boiler would be better. The usual direction of rotation is anticlockwise from memory but the factory info shows how to reset the valve timing so that it runs the other way but it does say that the efficiency is not as good. Revs in reverse is only about half what they are going forward. All in all I am sure you will be happy with it but I would not put it in a very big or very heavy hull. Let me know if you have any questions or if you need a copy of the factory info. Cheers, Ian.

[kno3]

Thanks for the info. I have the factory info.
I was thinking to put the engine into a light and fast type of hull. I have some Cheddar Puffins which I could use but I feel they are too heavy for a speedboat. That's why I would like to find a lightweight high performance boiler. any opinions about the steam production capacity of the different Saito boilers? They are much lighter, being made from brass.

[kiwimodeller]

The only time I tried a Saito boiler was with a T2 model engine and it did not seem to produce any more steam than a similar size copper boiler. I was not impressed with the Saito spirit burner and so I replaced the boiler and burner. I do have the feeling that the V4 could have quite a high consumption of steam if allowed to rev. I base this on early testing of mine with smaller props which allowed the engine to rev. It went very well but it was hard to keep pressure up. Perhaps it would be a good engine for a mono tube boiler as per Flash Two and the Vital Byte? If I was to put it in to another hull with a conventional boiler I would probably build a 7" x  3" or 6" x 4" boiler with a good ceramic burner. Cheers, Ian.

[HS93 (RIP)]

forget any Saito boiler's they will never maintain enough steam to run it without it being a bit of a hand grenade, the only boiler other than flash steam would be a MHB boiler they are all high performance high pressure very light boilers the one for the See Kadett is prob the one to go for, he does use light materials such as nickel steel for wrappers on some to keep weight down strength up. or ask mack steam to do a Proteus copy but that would not be light enough but would easy produce the steam.

peter

[kno3]

Thanks for the opinions. The Saito boilers I have are quite conventional in design and don't produce copious amounts of steam. Just like the many other centre flue boilers with some water tubes inside.
Regarding the MH&B boilers, I have asked the company but they only supply them with their kits, as they can't make enough to keep up with orders. So maybe if I find one second hand for sale...

I was thinking about flash steam too, but my concern is that it produces extremely hot steam, if I am not mistaken, which could be detrimental to normal model steam engines using rubber o-rings and such. What's the general opinion about this?

[Bernhard]

hi.............Take look on this  on

          http://www.youtube.com/watch?v=GM3eT3hKUXM&NR=1

[ooyah/2]

Kno3

I read with interest your desire to have a speed boat driven by steam using Mr Saito's engine.
I don't know much about this engine but if you say that it has rubber "O" rings in it and if so in my opinion it's not suitable for flash steam, as it's a piston valve engine it should be able to take a higher pressure and temperature than most engines but not the steam produced by a Flash Coil.

Speed with steam can't be bought with a cheque book and any boiler recommended other than a flash steam coil is a waste of money and also unless you have the know how to fire a Flash Coil, which can't be fired by gas, you will require a pressurised tank using either Paraffin or Petrol and then you have to hope that the engine will take the Flash steam, a more suitable engine would be thye Stuart Sun or if your boat could carry the weight , a Stuart  Cirius.
You can of course purchase a complete plant from say, one of the straight runners, but most of them make their own plant and don't generally sell, they are handed down to sons or passed around their club.
I would suggest that you stick to your existing steam plants and get them to work efficiently but if the urge to go down the Flash Steam road is so great, by all means go for it, I always quote from Mr Kirtley's article in the Model Engineer, FLASH STEAM IS NOT FOR THE FEINT HARTED

George.

[HS93 (RIP)]

Cheddar Models had a boat I think it was called the Arrow, at Cheddar meetings Ian hold would bring it out and blast it around the lake, it was a 40 something inch long and narrow with I think a hard chine hull it was powered by a striped down Proteus plant striped of all non essentials water pump I think base plate it was a open launch, that went very well darting around the lake for 15 min runs, but it depends on how fast you want, this was built with a lot of Mahogany so was not a ugly boat ill try and find some pictures, so your engine with something like the same boiler should do the same or faster. how fast do you want?

Peter

[kno3]

Thanks George and Peter.

I want it as fast as possible 
But of course I want to use this engine, as it is quite small, and not buy a Stuart Sun or a ready made flash steam plant.
So i guess flash boilers are not really suitable for this Saito.

I'm thinking a Yarrow boiler could be the answer, I understand that even in model sizes they are quite fast steamers and have a good output.

[gondolier88]

I'm thinking a Yarrow boiler could be the answer, I understand that even in model sizes they are quite fast steamers and have a good output.

If you don't mind either having a permanent feed arrangement or short but fast runs then a watertube could be the answer, whether you choose a Yarrow or not is upto you.

Greg

[ooyah/2]

Hi Kno3,
Hopefully Peter can find some info on the Cheddar Models set up which may be what you are looking for, it all depends on how fast you wish a boat to go,
 -20kph - 30 kph you will have to specialise if this is what you are after and to achieve these sort of speeds it would have to be Flash Steam
However the fastest steaming boiler that I have come across and not Flash Steam is a boiler designed by A.A RAYMAN called a SCOTT BOILER  and the drawings are still available from NEXUS Publishing and is used extensivly by the straight runners at BLACKHEATH MBC.,
With petrol or paraffin burner it will raise 150 psi of steam in less than 2 mins and the dimensions are 12' over the casing + 5" for the burner x 5" high x 2.5 " wide , I can't remember the weight.
Here is a pic of the boiler that I built with a copper fuel tank using Paraffin and pressurised to 60 psi by a bicycle pump, the boiler needs to have a constant water feed and this could be done with an electric driven water pump or if you could take a drive from the engine.

I don't think that the steam although super heated would damage your engine, I have seen pics of a straight runner using a 10V slide valve engine and the engine designed by A.A.RAYMAN  is made to suit this boiler and it is based on the 10 V slide valve engine.








A Yarrow boiler wouldn't be suitable as the fire box is too big and doesn't lend itself to being fired by petrol/ Paraffin burners.

I have tried most boilers and other than Flash Coils this SCOTT boiler is the best.








You don't say if you have any means of making this plant yourself if not you will have to have it made as they are not commercially available.
I hope that this is helpful to you and will help to make your mind up on the road that you take.

George.

.

[ooyah/2]

kno3,
I forgot to say that the best type of hull would be a Planing  Hull, one like the fast patrol boats.
George.

[kno3]

Very interesting, thanks. Well, I'm not set to break any speed records, but I thought that since I have this Saito V4PR engine that so easily spins to thousands of RPM it would be a shame not to put it to good use and build a boat that can rightfully called a speedboat. That's why I am looking for a suitable boiler.

I am not familiar with the Scott boiler. What does it look like inside? Do you have a picture or drawing?

I was thinking to use gas as fuel, which would work well with a Yarrow boiler too.

Regarding superheated steam, I think the Saito, as well as most other brass & bronze engines, can't take the extreme superheat produced by flash boilers (If I am correctly informed it should exceed 200°C).

[derekwarner]

kno3 ....try this link from Victor.......Derek   ......do a search in PD's for Scott boilers.....you will find approx 13 messages


http://www.paddleducks.co.uk/smf/index.php?topic=4292.msg26369#msg26369

[ooyah/2]

Hi Kno3,
Derek's link to the Scott boiler isn't the same as the one that I have shown you, the P.D. boiler is to the original boiler designed by Mr David Scott about 1900-1910. The boiler that I have shown is an update of this boiler and designed by A.A.Rayman , and is used mostly by the straight runners.
Steamboatphil has already posted pics of this boiler at your request, her is a copy. type in Steam springer and you will get the pics if they don't come up with this posting.
George.

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Re: Steam Springer
« Reply #19 on: August 21, 2008, 11:35:36 AM »
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Hi kno3
Sorry for the delay, new laptop, working and all such things getting in the way. Semi flash boiler, first thing, a flash boiler is really just a coil (often called a monotube boiler) which you throw a lot of heat at, as the water is pumped into the coil, it litraly flashes into steam, than as it passes along the coil it is superheated, this steam has a greater expansion than normal steam, and improves the performance of the engine. As the engine runs, its driving a water and fuel pump, faster the engine, the more it pumps, and so on. A semi flash boiler has coils under a plain boiler tube. This coils a really 1 1/2 turn loops (around 6 on a 7 in boiler). One side is short (water flows in) the other side ends just below the top of the boiler (steam is flashed out) Now unlike a pure flash boiler you are not using this steam, its being held for use in the boiler, which acts more like a steam resevoir. However as you use the steam any water pumped in is flashed into steam. Bit like bag-pipes vs trumpet, you use the direct air on a trumpet to make a sound, where as bag pipes you are filling a bag with air and indirectly using it to the create sound
And if all goes well, you should get a 4ft 6in boat doing 20mph +
Let me know if you need more info
Phil

[kno3]

Thanks, now I have found Phil's post (it's here: http://www.modelboatmayhem.co.uk/forum/index.php?topic=9779.msg116467#msg116467 ).
I didn't know that was a Scott/Rayman boiler. Looks like it should be easy enough to build.

[ooyah/2]

Hi Kno3,
Glad that you have found the thread, yes it's a reasonable easy boiler to make and is capable of high pressure, I have a copy of the boiler and it's construction in an old M.E. mag.
Will scan and e-mail it to you to see if you can read it.
Glad to be of help,
George.

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