Author Topic: Marcher, a twin cylinder marine steam engine  (Read 4714 times)

Offline b.lindsey

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Re: Marcher, a twin cylinder marine steam engine
« Reply #15 on: August 28, 2018, 01:47:33 PM »
Lots of nice progress in just a few days Moxis!!  Very nice looking parts too.

Bill

Offline Moxis

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Re: Marcher, a twin cylinder marine steam engine
« Reply #16 on: August 28, 2018, 05:32:18 PM »
Thanks Bill. Pensioners have time  ;D

Offline Moxis

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Re: Marcher, a twin cylinder marine steam engine
« Reply #17 on: September 02, 2018, 02:36:38 PM »
Next thing to do were the bearing blocks. No castings were provided for these, so they had to be made either of brass or mild steel. I chose brass, because I had very nice 6x40 mm stock material which was just about right for this task.

First suitable 3 pieces were sawn from the stock, they were milled 5,5 mm thick using jig made of suitable pieces of angle iron. With the "jaws" of this jig it is possible to fasten the pieces into milling machine table, because jaws are thinner than the milled material.

Pieces were sawn into two with a slitting saw, soldered then together with soft solder, and holes for bearings drilled in the 4 jaw chuck. Spigots for oil cups were then turned, together with cutting M3 threads for them. And finally 2 mm holes for fastening bolts were drilled.

« Last Edit: September 02, 2018, 02:41:35 PM by Moxis »

Offline Moxis

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Re: Marcher, a twin cylinder marine steam engine
« Reply #18 on: September 05, 2018, 02:01:35 PM »
Next thing to do were the oil cups for bearing blocks and bearings itself. There was no drawing about the oil cup on the drawing sheet, but with 4,7 mm diameter and 5 mm height I couldn`t go very much wrong. Oil cups were equipped with M3 threaded studs, through which a 1 mm hole was drilled.

Bearings for crankshaft outer ends were made of OD 8 mm brass stock, turned according to measurements and reamed with 6 mm reamer. With it a nice sliding fit was achieved with crankshaft.
The middle bearing had to be made of two halves, so it was made soldering first two pieces of 6 mm flat brass together, then turned that in the four jaw chuck into measurements, and finally solder was melted to separate the two halves.

3 mm holes were drilled at bearings where the threaded studs of oil cups passed to prevent them from rotating.

Offline Baner

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Re: Marcher, a twin cylinder marine steam engine
« Reply #19 on: September 05, 2018, 02:38:42 PM »
Looking good Moxis. :ThumbsUp: :ThumbsUp:

Dave.

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Re: Marcher, a twin cylinder marine steam engine
« Reply #20 on: September 05, 2018, 06:48:33 PM »
That's a sweet, and rugged, little engine!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Moxis

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Re: Marcher, a twin cylinder marine steam engine
« Reply #21 on: September 07, 2018, 08:32:22 AM »
Thanks a lot both of you Daves  :cheers: for your interest into my build!

Lessons learned: When I tried to rotate the crankshaft in the bearings, it hardly moved. Even when I tried to fabricate the parts as accurately as possible. So there was no other way than to replace the 3 jaw in the lathe with a collet chuck and start to repair the shaft with very light cuts on the bearing areas with a sharp tool. And finally polish it with 800 grit emery paper. And voila, after a while`s work the crankshaft rotated like a dream.


Offline zeeprogrammer

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Re: Marcher, a twin cylinder marine steam engine
« Reply #22 on: September 07, 2018, 01:55:07 PM »
Congrats!  :ThumbsUp:
Looking like a beauty.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Zee-Another Thread Trasher.

Offline Kim

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Re: Marcher, a twin cylinder marine steam engine
« Reply #23 on: September 08, 2018, 01:28:27 AM »
Very pretty looking crank and bearings!  Glad you were able to get them fitted well.

I've always liked the look of these little marine twins!  Enjoying your build.  :popcorn:
Kim

Offline Moxis

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Re: Marcher, a twin cylinder marine steam engine
« Reply #24 on: September 09, 2018, 10:14:27 AM »
Thanks zeeprogrammer and Kim! I am very pleased that you like my build.

Next 4 pcs eccentric sheaves were turned of 16 mm mild steel bar. There is nothing special with these turnings but to drill the offset hole. Of course I could have made that in the 4 jaw chuck, but somewhere in Internet I had read that it is possible also in the 3 jaw chuck, to put a packing under one of the jaws. This method was quite new for me, so I decided to try that.
There are at least two formulas to calculate the thickness of the packing:

Simple formula:  Packing = offset x 1,5

More accurate formula:  Packing = 1,5 x offset x (1-(1/8x(offset/bar diameter)))

Calculating after the first formula, I got the thickness for packing 3,49 mm, and after the second one: 3,57 mm.

I selected 3,5 mm to be the compromize for me and made a brass piece of that thickness in the milling machine, put that under one jaw of the 3 jaw chuck and started turning. I think it succeeded quite well, resulting to the wanted offset of near 2,4 mm.

So now the eccentrics are made, but I have no idea, how they must be adjusted to get the timing right. There is nothing shown at the drawing. I wonder if some of you might be able to help me.

« Last Edit: September 09, 2018, 10:19:38 AM by Moxis »

Offline mechman48

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Re: Marcher, a twin cylinder marine steam engine
« Reply #25 on: September 09, 2018, 11:57:19 AM »
Very nice looking engine so far, will be following with interest   :ThumbsUp:

George.
George.

Offline propforward

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Re: Marcher, a twin cylinder marine steam engine
« Reply #26 on: September 09, 2018, 03:07:24 PM »
That is a cunning approach to making the offset hole - thanks for sharing that.
Stuart

Offline K.B.C

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Re: Marcher, a twin cylinder marine steam engine
« Reply #27 on: September 10, 2018, 09:03:33 PM »
Thanks zeeprogrammer and Kim! I am very pleased that you like my build.

Next 4 pcs eccentric sheaves were turned of 16 mm mild steel bar. There is nothing special with these turnings but to drill the offset hole. Of course I could have made that in the 4 jaw chuck, but somewhere in Internet I had read that it is possible also in the 3 jaw chuck, to put a packing under one of the jaws. This method was quite new for me, so I decided to try that.
There are at least two formulas to calculate the thickness of the packing:

Simple formula:  Packing = offset x 1,5

More accurate formula:  Packing = 1,5 x offset x (1-(1/8x(offset/bar diameter)))

Calculating after the first formula, I got the thickness for packing 3,49 mm, and after the second one: 3,57 mm.

I selected 3,5 mm to be the compromize for me and made a brass piece of that thickness in the milling machine, put that under one jaw of the 3 jaw chuck and started turning. I think it succeeded quite well, resulting to the wanted offset of near 2,4 mm.

So now the eccentrics are made, but I have no idea, how they must be adjusted to get the timing right. There is nothing shown at the drawing. I wonder if some of you might be able to help me.


Hi Moxis.

I too have recently machined a set of Marcher castings, it's a fine little engine with plenty of power and like you I came to a stop when timing the engine via the eccentrics.
I made bosses on all of the eccentrics with enough space to fit 1.5mm or 2 mm socket grub screws which allows each cylinder to be timed individually by the age old method of the valve just beginning to open a crack at T.D.C. in the way that you want the engine shaft to turn over, similarly at B.D.C.

There is enough room to make the bosses as if you look at the G.A. you will see that there is a space to allow the reverse gear drag link to clear the upright posts.

I made my engine to fit on a brass bed plate as I wanted it to sit well down in a Launch hull, I include a couple of pics showing the bosses on the main shaft. The pics are not very good but it shows the bosses on the eccentrics, this engine was started by an old friend with very shaky hands and I had to make new parts and buy a new cylinder casting, but all is well now.

Incidentally you have the eccentric fitted wrongly, the flanges should be one to the engine side and the other away from the engine.

I hope this helps George.
« Last Edit: September 10, 2018, 09:07:01 PM by K.B.C »
Your never too old to learn.

Offline Moxis

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Re: Marcher, a twin cylinder marine steam engine
« Reply #28 on: September 11, 2018, 06:01:51 AM »
Thanks a lot George and Stuart for your kind words and interest to my humble build!

And thanks George for your advice for eccentric adjusting. Somewhere in internet I have read that the eccentrics should be adjusted 90+ degrees ahead of the crank, but nobody seems to know, how much degrees the + should be. I think your approach is the best, to actually see when the inlet ports are opening, and set the bosses there.
I was also considering to make the baseplate from stock material to have it as thin as possible, but somehow I like that cast one with it's rugged outlook to suit better for this machine. It might however be too tall also for me when I will install it into my models hull, but we will see.
And thanks for your pictures, it is nice to see that somebody has really built a Marcher recently.

Offline Zephyrin

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Re: Marcher, a twin cylinder marine steam engine
« Reply #29 on: September 11, 2018, 07:48:42 AM »
Very nice looking parts, beautiful engine for your boat !
the way you have made the eccentrics is very efficient but probably not accurate enough ; the offset determines the travel of the slide valve on the steam ports, hence if it is not exactly as per the drawing, steam distribution will be affected, and maybe you will have to modify in accordance the valve dimensions (or the port sizes and spacing) to keep the performances of the engine at the top.