I would imagine these engines will be grossly overpriced, as is all MHB kit. Looking at their twin cylinder engine, it is exactly the same, it looks like they have just extended the bed and made a bigger cylinder block, most of the other parts will be common to both engines, spewed out by a CNC machine, probably under subcontract to an outside firm. I do not like the un supported crossheads, they don't look the part at all, and imagine if the engine had to do any proper work for any length of time the glands would soon be worn and leaking steam. far better to have a trunk guide as in TVR's or Stuart Double tens, or 'slipper' type guides as in Stuart launch engine. I think Stephenson's valve gear looks much better than the Maudsly gear, which is, at the end of the day, basically a camshaft with eccentrics instead of cams. If they are configured as a triple expansion engine, a simpling valve arrangement would be needed to get the engine running as TE's are difficult to self start. Well, thats my twopenneth there are probably those who disagree, but to each his own, They are, as far as I am concerned, the 'bling' of the model steam world.
Sorry for the lack of proper quote, the button didn't want to work for some reason!
Firstly, MHB is not overpriced, it is what kit of this quality costs to make and make a profit on top, other manufacturers make lots of models of a good quality and make their margins, just. MHB make a few high-end pieces, that will never lose value, and if looked after are investments in themselves.
If they have extended the bed of the twin and and added a third cylinder they are copying marine steam engine construction methods from the last 150 years, and I'm not really entirely sure what your problem with them doing so is?
I agree, cross-heads do look 'right', and perform their job admirably if made properly, but have can you substantiate your claims with proof that the glands designs and materials they have chosen won't stand the test of time? There are millions of hydraulic applications out there that use the piston and gland as guides only that don't leak a drop at much much higher pressures than our engines work at.
Stephenson's gear is unsophisticated, noisy, inefficient as it wears and requires the friction of four eccentrics to drive it (edit- in a TE, of course, there would be 6 eccentrics), plus loss of energy through the natural errors in the arcs of the die-block. Due to these errors the majority of Stephenson's geared engines have glands that pass water, even in small amounts, this water goes onto the valve gear and fights any lubrication, adding to wear issues. Gear driven valve gears have none of the above, and will give hundreds, if not thousands, of hours of reliable steaming with nothing more than a bit of oil on the gears. On the other hand, through a little thought, MB could have got around the problem of water ingress into the eccentrics from the valve rod glands, but have chosen not to.
Lets see if anyone on this forum gets one and sticks it in a boat.
Where's Kusuchi when you need him....
Greg
Colour changed, as Blue is reserved for the moderating team
Ken