The Steamboating Forum

My understanding was that Stuart 6A's always had simple slide valves. However, I recently viewed a Stuart 6A which was described as a Stuart 6A-2 with balanced valves. Can anyone say if this was a Stuart Turner modification or more likely to be the particular engine builder's idea? Also does anybody have experience of this set-up and any advantage or problems encountered with it?
Thanks for all help.

I have no direct experience w/ the 6A, but I do know some people that have had problems w/ the HP valve rod.

Here's a video of one running: https://www.youtube.com/watch?v=6mFeS_C6O98

Either reducing the forces placed on the valve rod via balancing, or increasing the size of the rod would help.

- Bart

Uno, owned and operated by Steph Hilton and home ported here where I live, has broken the H.P. valve rod twice. Now the engine has a new larger diameter rod. We'll see. The next step, of course, is to go for a balanced valve at least on the H.P cylinder.

I the proud (well maybe proud) owner of a Stuart 6A2. I'm told (and this may not be correct) that the **2 bit was adopted by a number of engine builders, supposedly Anthony Beever in my case. The other substantial difference is columns etc. which make the engine a bit taller and reduce the obliquity. Mine also has roller bearings, but I think they were installed by an owner rather than the original builder.

Balanced slides or conventional slides better? Standard thinking is that balanced ones would be better, but with working pressures below 150 psi (where my safety valve is set, and many others of course) it really isn't a big deal. You also MUST be careful with engine warming and getting rid of any condensate, where conventional slides would just lift off to relieve the pressure. The main problem with mine though is that they fail occasionally into an odd state which means the engine completely stops working, especially when using the reverser for manoeuvering, and this has happened to others with the same engine and valves. I haven't yet had the covers off to try and work out what's happening, but it seems likely that something undesired is happening as a result of the more complex balanced valves. The problem sorts itself if the HP valve chest drain and cylinder drains, are opened for a while.

The previous owner of my boat claimed that there was never any water droplet carry-over from the boiler, but I'm not so sure, and am suspicious that the HP valve chest is collecting water while running under some conditions. The main steam feed runs the length of the top drum inside the boiler casing, and must act as a steam drier, but when the burner is turned down to avoid blowing off before stopping, it clearly won't do much drying, and that might just provoke the valve gear into getting upset. Investigating the valve problem is the next thing on my list, having now experienced it several times.

When in a good mood, the engine runs and reverses very nicely indeed, and pushes the 19', 2 ton boat VERY quietly along at 6 mph (sat nav measured) with 80 psi in the boiler. When it suddenly fails when trying to dock, it's a PITA.

Not on the subject of 6As, but how do you find it having roller bearings, what type are fitted and how are they kept from getting and water in them?
Daniel

RGSP wrote: Mine also has roller bearings, but I think they were installed by an owner rather than the original builder.

RGSP,
Thank you for your reply. It was just the kind of detailed info on the pluses and (possible) minuses of the balanced valve system I was looking for. I also was not aware that the '6A-2' had extended columns. Are there any other tweaks I should be aware of?

I take it from your answer that you are using liquid fuel and assume that this is paraffin? If so, do you have any problem locating it in sufficient quantity?

Best Regards,
OS

Old Steamer wrote:RGSP,
Thank you for your reply. It was just the kind of detailed info on the pluses and (possible) minuses of the balanced valve system I was looking for. I also was not aware that the '6A-2' had extended columns. Are there any other tweaks I should be aware of?

I take it from your answer that you are using liquid fuel and assume that this is paraffin? If so, do you have any problem locating it in sufficient quantity?

Best Regards,
OS

As I don't have a 6A2 specification, I'm not sure all of them do have extended columns: mine does though. Mine also has a full simpling valve rather than an impulse one - it works, but it's a hefty, sticky thing relying on a large conical, rotating plug with steam passages cut into it, and usually needs two hands to turn it. Anyway, when all is well, reversing is very good in compound mode without disturbing it.

Having not had the engine all that long, I don't know how well the roller bearings will stand up to the rigours of a wet steamy atmosphere. However, the bearings are lubricated from a multi-way pressure feed, and the "works" are invariably oily rather than wet, so I live in hope

Yes I do indeed burn paraffin - grade C1 (lamp and heater) paraffin in fact. It's very widely available in 20 litre plastic containers, which my local hardware store sells at £28. Expensive, but the boat uses about 1 litre per mile, so in terms of the total cost of running a steamboat it isn't that bad. It's also available in 205 litre (45 gallon) drums at about £230 one off, reducing quite a lot for more than one.

The previous owner of the boat tried standard central heating grade kerosene, and it bunged the (vapourising) burner up, mainly as a result of the bio-fuel component as insisted on by the EU. He was running it recently on standard EU Kerosene + 20% petrol, which is claimed to avoid the clotting/char problem. A pressure-jet burner would almost certainly be fine anyway.

Having subsequently tested several burners with various fuels, out of the boat, and in the middle of my concrete farm-yard, I would strongly advise against using the above mixture. I was suspicious about it, and therefore wore a face-mask and anti-flash gear when testing, and boy did I need it! The fuel was fine until one of the jets went out for maybe 20 seconds and then re-lit: even straight paraffin would have flashed a bit after that, but this was seriously nasty, and would have caused major injuries if it had happened in the boat.

Burner testing was really because one of the burners I bought with the boat had failed catastrophically a few weeks before, and I wanted to test it and the others before refitting and using any of them in the boat. The failure was because the 1/2" plug in the end of the main vapour distribution tube was only soldered in (not screwed) and blew out, turning a nice, reasonably well-behaved, burner into a substantial flame thrower - quite honestly a bit frightening. The plug was brazed in, not soft soldered, but the braze had only wetted a very narrow ring about 0.5mm wide, visible from outside, and failed with a bang. When I started investigating, the other end of the same tube was sealed with something like car exhaust repair "gun gum", and leaked enough for a large candle flame. There WAS a screwed brass plug hidden under the black gunk, which had obviously been applied to stop a pin-hole leak and didn't work, but I only found that by drilling out and destroying it, and ended up inserting a mild steel plug and welding it into place, which seems fine.

The seller of the boat had a good reputation, but it's definitely a case of "buyer beware".

Quote: "As I don't have a 6A2 specification, I'm not sure all of them do have extended columns: mine does though."

From what I've read, that is a good thing. The standard column height on the 6A is very short. Which causes excessive loading on the crosshead guides (increased connecting rod angle).

Quote: "I don't know how well the roller bearings will stand up to the rigours of a wet steamy atmosphere. "

Are they roller or ball bearings? Sealed ball bearings hold up very well in that application. It's the most reliable aspect of a steam engine if they are being used.

-Ron

My Strath Steam "Warrego" has ordinary single row sealed ball bearings on the mains and large diameter small cross section ones on the the eccentrics. They have given zero trouble over years of hard use.

DetroiTug wrote:Quote: "As I don't have a 6A2 specification, I'm not sure all of them do have extended columns: mine does though."

From what I've read, that is a good thing. The standard column height on the 6A is very short. Which causes excessive loading on the crosshead guides (increased connecting rod angle).

Quote: "I don't know how well the roller bearings will stand up to the rigours of a wet steamy atmosphere. "

Are they roller or ball bearings? Sealed ball bearings hold up very well in that application. It's the most reliable aspect of a steam engine if they are being used.

-Ron

I haven't had them apart to check Ron, but I was told they're mostly needle rollers. The eccentrics are plain, both for the valve gear and the feed pump, as are all the small bearings needed for the reversing gear.