Marcher /twin cyl marine steam engine

[Paul Smitherman 2Participant @paulsmitherman2]

Can any one point me in the correct direction for timing the eccentrics for this engine in its piston valve configuration ,as have constructed same opting for 7/16" bore's BUT the designer gives NO indication of just how to time the eccentrics ,Think I have managed to work it out that at TDC THe accentric should be 90 degrees in advance of the TDC OF PISTON , Can any one confim or denigh this for correct setting Regards Paul S

[Paul Smitherman 2Participant @paulsmitherman2]

Twin cyl steam engine By J P Bertinant

[JasonBModerator @jasonb]

It is usual for the valve to lead the crank by 90deg plus approx another 30degreed so the thickest bit of the eccentric would want to be at 4 o'clock when the crank is at TDC .

You can reduce the angle to about 10deg if running on air but 30 works for both as a good starting point.

here is one I did earlier though running anticlockwise as viewed so max throw of eccentric is at 12 o'clock where the allen key is and the crank at 4 o'clock but same setting as eccentric is 90 +30 ahead of the crank

Edited By JasonB on 17/08/2022 13:05:17

[Paul Smitherman 2Participant @paulsmitherman2]

Many Thanks Jason thats re assuring as am in the right area just not enough / With that setting is the engine avble to reverse .ie;- inside outside admission on this small marine engine there is a steam reversing valve where in becomes out and vise versa

[JasonBModerator @jasonb]

Ah, if you are using an air valve for reversing then you will probably to have go with no lead so just set the biggest throw of the eccentric at 90degrees to it's crank as you said in the first place. I was thinking of the slide valve version which you can't change air direction.

Need to go and play with a piston valve engine to check that.

Edited By JasonB on 17/08/2022 15:52:12

[JasonBModerator @jasonb]

As you were, I just tried it on my Gamages replica which has approx 30 & 90 so when the air is feed to the central inlet (inside admission) and it will only run in one direction. Feed air into the two exhausts (outside admission) and it will only run in the opposite way. Short video uploading.

[JasonBModerator @jasonb]

Rough and ready video as it was a bit of a job holding the two tubes, flicking the flywheel and holding the phone.

Starts off with air going to the two outer ports and engine runs anticlockwise.

I then change to air into the middle port and engines runs clockwise, try to flick it anticlockwise a couple of times but just wants to start going clockwise.

This is what you would want in a RC boat so that the servo moving the air diverter will give fwd & rev, being a twin cylinder you will get self starting.

This shows the max eccentric throw at the top and although hard to see the crank pin is at 4 o'clock.

Looking from the opposite end 4 o'clock becomes 8 o'clock but still that 30 & 90 diference to 12 o'clock

[Paul Smitherman 2Participant @paulsmitherman2]

Many T hanks Jason for time & trouble in replying. So eccentric (max throw ) needs to be approx 110degrees in advance of TDC of piston , think another problem for Marcher is to much friction at the moment (Need running with electric motor) to bed all in , Then neeed to construct boat to fit her in possibly MIRANDA If i can increase size by approx 10-15 % just a little more involved than the IOM boats I usually construct , Many thanks Paul S

[JasonBModerator @jasonb]

yes 110-120degrees.

I'm not a fan of "motoring" a model, better to build it up adding one piece at a time and dealing with any tight spots as they show up rather than wearing it in.

[Paul Smitherman 2Participant @paulsmitherman2]

Many Thanks Jason for time and trouble in replying ,Much appreciated ,Just add I am not a fan of using air for running as it is to hard (NO EXPANSION ) apart from inital puff but we all have our preferances. !!! Many T hanks again Jason . Regards Paul S

[HopperParticipant @hopper]

Posted by Paul Smitherman 2 on 18/08/2022 09:10:03:

Many Thanks Jason for time and trouble in replying ,Much appreciated ,Just add I am not a fan of using air for running as it is to hard (NO EXPANSION ) apart from inital puff but we all have our preferances. !!! Many T hanks again Jason . Regards Paul S

I have found little model engines run quite nicely on just 3 or 4 PSI of air from a cheap regulator on the compressor.

[JasonBModerator @jasonb]

But you will need a long hose if it's destined for a model boat

[HopperParticipant @hopper]

Posted by JasonB on 18/08/2022 10:06:12:

But you will need a long hose if it's destined for a model boat

True dat. Or a big model LNG gas tanker ship charged up with air!

[Paul Smitherman 2Participant @paulsmitherman2]

This is exactly the reasion i don't post on forums as every one "just guesses" what they think you have posted without actualy reading the post, Did I NOT say Iam not a fan of using air for running ITS TO HARD NO EXPANSION ANY HOW WE ARE TALKING "STEAM ENGINES" NOT PNEUMATIC ENGINES The engine incorporates a boiler feed water replacement pump for said boiler Small copper boiler about 3 bar litre fired with propane ," next question" and just make sure you have read exactly what is written , Paul S

[Author]

Posts