Miranda by Basil Harley running on steam problems

[VicE]

Hi to all at Puddleducks.

I am new to to quality steam boats as my experience only extends to restoring a Bowman Snipe.

But now I have managed to acquire a very high quality Miranda steam launch complete with the original design Oscillating twin engine.  The original builder tolled me that the engine run fine on air but was problematic on steam, this appears ot be the case.  I have checked out the build and it seems inline with the plans and it runs on my small air brush compressor but NOT steam.  In searching the net I can only find examples of this engine running on air, and some comments (not good) about the engine.

So has any one out there got this nice little engine running on steam and have you made any modification from the original design.

Many thanks fir help, vic   

[Hankwilliams]

Hi Vic,

if the engine runs with compressed air, but not under steam - this can`t be caused by an construction error. When you try to run your engine with steam - is there stiff operation of cylinder and piston? I presume it is. There must be an interrelation between the heat of steam and the extension of metal of cylinder and piston. Therefore I presume, the necessary clearance between cylinder and piston must be too less. How much is air and steam pressure?

Another more simple reason could be very wet steam with much water in it. If the cylinder are full of condensed water no movement is possible, but the water should be thrusted out after some turnings.

So I conclude the probability of too less clearance. This should be not too difficult to alter with polishing the pistons by a lathe.

Thomas

[derekwarner_decoy]

Hullo Vic........

The comments from Thomas are certainly in the right direction & are good starting points...[heat expansion or hydraulic lock]

Oscillators [usually] have a stud, spring & nut holding the cylinders against the valve faces, if the engine will turn over on air, try loosening the cylinder retaining nuts a little when under steam

Is the engine home built?.......does the plant include a lubricator?...why not upload a few images

The link below may be of value to read as others have experienced issues with the steam plants in the Miranda

 https://www.bing.com/ck/a?!&&p=813e453ffb259275JmltdHM9MTY2Mjg1NDQwMCZpZ3VpZD0xYTRmYWU1MS05Yzk0LTZiNDUtMjQyOS1iZmFjOWRhNjZhNmImaW5zaWQ9NTE2Ng&ptn=3&hsh=3&fclid=1a4fae51-9c94-6b45-2429-bfac9da66a6b&u=a1aHR0cHM6Ly93d3cuanNibW9kZWxyZXN0b3JhdGlvbnMuY29tL21pcmFuZGEtc3RlYW0tcGxhbnQv&ntb=1

Derek

[VicE]

Hi Derek and Thomas

Many thanks for your comments, I need to do a little more checking that the valve block port line up.
I don't think the cylinder clearance is the problem, but will check the dimensions, originally the pistons just had an oil groove, but I have packed them with PTFE which did help the low pressure air operation.
I will try to get some pressure values for the air run but the steam was tested at 30-40psi.

I did find one small manufacturing error which was the spring pin which load the valve faces was out of line and as the cylinders rock the seal was broken. So for my testing I simply used a rubber band to form a face seal and has very low friction, this may be my problem.  With steam the seal face pressure should be much higher ?.

I do check the the steam is not water logged before test and there is lubrication.

I will upload some picture and get some more testing done.

Thanks all vic

[VicE]

Hi Derek and Thomas

I have spent several hours checking the engine build and unfortunately found some errors.  The pistons and cylinder are good but the center valve block looked like the the drill wanders and the ports are missed timed.  I made a small adjustment to the ports and now on air the engine run quiet well in both directions.

I also have it running on steam but there is a great deal of loss from the port/cylinder I don't know if that is normal on oscillating engines, the net result is the boiler pressure drops very quickly from 40 psi.

I think the firing is inadequate, may be that is the problem and I should install a Bix burner, it was my long term plan.

Enclosed some pics
   

[Hankwilliams]

Hi Vic,

boat and engine are really looking good. As you write - it seems, that the center valve block is the reason for the loss. It should be not too difficult, to make a new valve block. You will need a drilling machine with pillar and work very exact. A professionell mechanician also will do it - the boat is worth to do this improvement. Maybe, the firing isn`t very strong, but I don`t think this is the only reason.

Thomas

[derekwarner_decoy]

Vic...the engine from what we see appears to be demountable, there are the obvious tell tale signs of hand filing on machined surfaces, which really or shouldn't be necessary

From this and the symptoms of excessive bypass from the valve faces could conclude hand filing of these mating faces, which can be difficiult to achieve a reasonable flatness so to provide sealing surfaces lubricated by wet steal & steam oil

As Thomas suggests, a professional mechanic [machinist with a milling machine], so if the engine is demountable the machinist would be able to mill the surfaces to be true, horizontal, vertical and flat [in a perfect world, these mating surfaces may be scraped post milling]

One point here is when an additional lick is taken off these faces may cause an alignment issue with the cranks to big ends at the crankshaft webs

Derek

[VicE]

Has anyone tried EVT

http://www.panyo.com/oscillators/

I have been thinking over the last few days, all the ports are close for a large part of the cycle this may help.

I have under cut the mating to to reduce the friction, at the moment I am not in contact with an engineering group with good equipment and I just have a pillar drill so will continue with the existing valve block.

It is my intention to correct the port errors and implant EVT with 2mm End Mills.

Will report the outcome

[Eddy Matthews]

Has anyone tried EVT

No, but I did try an ECG earlier in the year when I had a heart attack!

Regards
Eddy

[derekwarner_decoy]

Vic

I previously mentioned the need for accuracy, trueness & squareness etc, so to attain these for model applications, jigs, alignment pins, a milling machine and a dial indicator should suffice

x, y & z digitals could certainly be useful, however not absolutely necessary

I read how EVT was used in the alignment of the largest Radio telescope dish in Australia [for the Americans], however not sure hou you would apply these processes to your engine alignment reclamation

As always, I would be pleased to read not just your results, but also the steps, from concept to the progression

Have you concluded about the possible alignment issue with the cranks to big ends at the crankshaft webs?

Is this threaded pintal the item/s you will reclaim with the 2 diameter endmill?

Derek     

[jefran]

Looking at the 2 pictures of the engine I wonder if the valve block is actually proud of the centre portion of the plate it sits on.  If the block has moved, or worn, so that the face is even a tiny bit behind the web of the plate then the cylinder port will be lifted away from the block and leakage will follow.

[antopia]

Vic, here is my take
remove cylinders and apply thick steam oil replace and try  on steam i think you have 2 areas to look at
1 there is no clearance on the cylinder port face to the port,there by the heat will make the cylinder movement cause more drag
2 normally the cylinders are spring loaded but yours is static so thereby you could either have too much pressure or
to little. most oscillators have either a spring on the rear of the port face as a single, or a piece of spring steel too push the cylinders onto the
port face with a  twin.
hopefully this makes sense


regards
Steven