Lister Engines > Listeroid Engines

12-2 Air over Start

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multis6:
 I have a Metro 12-2. that has become heaver to start each passing year (or I'm getting older).  Has any one set up there machine to start with air over the top of the piston to roll it over and get it started?
I have done a search but have not sorted through the 1000+ postings offered. 

38ac:
Not that I am aware of. All of the starters I have seen spin the flywheels. If your 12/2 is as I should be with change over valves adding air start will require some extensive changes to the cylinder head. If you have the 8/1 or 16/2 type heads with the plug you could go in through it. Be aware that starting an engine that way requires a large volume of air quickly so line and valve sizes must be sized accordingly.  But that brings another issue into play. Whatever passages you have between the valve and combustion chamber will serve to lower the compression in that cylinder. System s like you wish will have a one way valve very close to the cylinder for that reason.
What you propose is a lot of work and engineering to get around spinning the flywheels via electric or air motor with friction drive but to each his own ;D

BruceM:
I concur.

To do an air over starter, an intake valve in the changeover plug would be needed, as well as an electronic actuator and a very high volume solenoid valve to turn on/off the air, along with cam position sensor so that the valve timing could be managed for multiple rotations.  It would be technically challenging, and a cool retro-engineering project.

The far more practical and well proven approach is a starter motor with rubber friction drive, or a conventional auto starter motor on gear ring on generator.

I use a Gast 4AM motor with rubber roller friction drive, with a small air cylinder to press the motor/roller against the flywheel.  Some others have gone this route. This is practical for me since compressing air is a major job of my Listeroid. I also use air cylinders for an exhaust valve lifter and rack closer; my Listeroid is remote/autostart.

For most, an electric starter motor with rubber roller drive or gear ring drive on the generator would be the simplest and most effective.  It's well proven and low risk.

multis6:
Thank you for your input guys, I have a Gast 1550 air motor on my engine right now but the contact wheel is too large and it will not turn over the engine. I need to get a smaller and softer wheel to get the ratio correct.
 
I have worked with a 1 megawatt genset that had a 8 cylinder tug boat engine on it with an air start system.
It was the neatest thing to see it start. Flip the switch and the unit would crank over then fire up, with in 10 seconds it was producing power. As you said BruceM "It would be technically challenging, and a cool retro-engineering project." It is interesting to ruminate over the possibility of doing such a project.

Bruce the system that you have set up sounds interesting, Do you have any pics. that you could share to see how you have it set up? What size engine are you starting?

BruceM:
It was posted here in 2007, just before I completed the Picaxe based remote start/monitoring controller. Alas, you can't see the roller as it's facing the wall. It's about 2.25" diameter, 2" wide. That's a small oiler in the air line right at the motor.  The Gast 4AM motor does a good starting job on the 6/1 Listeroid even with unloaded air compressor but must have decompression.  The 12/2 is likely too big for it.  Someone tried a 6AM motor on a 12/2 and then switched to electric- the 6AM is a massive air eater, and plumbing for that much airflow from a tank will be a challenge. 

Pressure loss in the line significantly affects even the 4AM motor, which must have 1/2 hose supply, high flow solenoid, and short 1/2 exhaust to a 3/4 pipe tractor muffler (low back pressure).  The motor only sees the difference between input and exhaust pressures...a real eye opener when gauges are put on each next to the motor inlet/outlet under power. 

I'm not familiar with your Gast serial number.  Their standard product is in various family sizes, 1AM, 3AM, 4AM, 6AM.  They also made contract units of oddball models.  I use the 1, 3 and 4 AMs, I don't have the air supply for the 6AM.

McMaster.com has rubber rollers.  I used one with a 1 inch bore that fit a 1" OD shaft coupler and a fairly soft rubber for good flywheel grip.  Still using the original roller 12 years and 3K engine hours later.  A few starts daily for 20 minute runs when I'm working in the shop, for filling the 500 gallon air tank.  If I forget it shuts itself down after 10 minutes of no power or air load.  A pressure transducer and circuit can see the pulses of air pumping...and when the air unloader pilot valve has turned it off.

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