Author Topic: air starter  (Read 3126 times)

mikenash

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air starter
« on: February 13, 2017, 04:46:47 AM »
Guys, I'd really like one of the big slow engines like the 4YHR units or similar - all the old side-shaft units, really.  But I don't fancy my chances of finding one . . . .

I really like the way they're designed to run 24/7

I have been watching a bunch of videos on them - and it looks as if maybe the air starter assemblies are an early casualty when they are decommissioned and then abandoned?

I guess there's some kind of cam assembly that "times" air into the cylinder a couple of degrees after TDC on the power stroke or some such?  But, watching videos, it seemed to me maybe some folks just had a manual valve and were watching the strokes and just giving it a "puff" of air at a couple of hundred PSIs on each power stroke until it picked up running speed . . .

Is that what I have been seeing or have I misinterpreted that?

Those big old slow machines with their external bearings and external lube systems and big rotating governors have a fascination all of their own IMHO

I really like the way the mains and big-ends and piston-and-rod are just "there" to lube or work on etc etc

Cheers

gusbratz

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Re: air starter
« Reply #1 on: February 13, 2017, 03:46:20 PM »
i dont know any thing about that engine but i have worked on large IR VGseries gas engines with air starters. they have an air starter valve on each cyl head that mounts just like a diesel injector. it has a 1" 100# air main line conected to it. it also has a small piston in the top that has a 5/16"  piece of tubing connected to it. when pressure is sensed on the pilot tube it opens the pilot piston thus firing the air starter. as long as there is pressure on that small tube the air starter remains open. down on the timeing gears of the enging  there was a mag on one side and an air starter disttributor on the other. the air starter distributor  had a plate inside it with holes in it and bits of 5/16 tubeing comeing off the back going to all the air starters on all 12 cyl's. it was a nightmare to try and fix air leaks on or remove to work on other parts of the engine. it sat there and spun whenever the engine was running but the plate with the holes in it was only pushed in when the air pressure was on it so it didn't really wear. i also remembe 2 big 3 way valves below it. 1 for gas and 1 for the air starters. so starting an engine with out flooding it tended to be a bit of skill as you rolled the engine over then turned on the gas and let off the air and away it went. also there is only so much compressed air in the tank so you had a  couple of shots and then we all stood around for 20 min while the station air built back up if she didn't go.

gusbratz

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Re: air starter
« Reply #2 on: February 13, 2017, 03:55:06 PM »
the more i think about it the main problem with ours was wet station air. we would start an engine and the water would get into the  pilot piston and rust it up. then the engine would run for  6 or 8 months at until it needed something. we would shut it down do whatever then try to start it and half would not open. sometimes beating them with a hammer freed them up. then once the engine stated they would then stick  open and all the fireing pressure from the engine would be blowing up into them. they would strart smoking and the paint would blister off them. the best solution for all this was to plumb all the air lines so they slope away and down from the air starters so the  condensed water would run way from the air starter after a start cycle.

mikenash

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Re: air starter
« Reply #3 on: February 13, 2017, 11:07:48 PM »
Gotcha.  Yep, wet air is always a problem

Often you'll find the air plumbing has a "downleg" with a valve to be left open and allow it to drain at the lowest point - or an autodrainer; but then people forget, and the autodrainer fails, and . . .

cheers

glort

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Re: air starter
« Reply #4 on: February 13, 2017, 11:54:42 PM »
For an air starter timing, Just use a solenoid and trigger the thing off a magnet on the flywheel with a hall effect sensor to time when to inject the air.
I think you would need some sort of self closing injector or otherwise the space the air feed took up would reduce compression.

Jake65mm

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Re: air starter
« Reply #5 on: February 15, 2017, 04:53:49 PM »
There is two types of air start systems on Ruston hornsby engines, but let me start from the beginning. Twin flywheel Rustons are considered more for agricultural/ farm use and single flywheel versions are industrial, the air systems are different on each. Look up Ruston grain elevator engine Mark CR/ 3XHR Mark CY/4YHR and you will see the air start valve on the head with a lever. That is the manually timed verision, also note on the side shaft side of those engine next to the governor the have a face machined into the casting but is not used on the twin flywheel model. On to the single flywheel industrial version ,one those there will be a cam bolted to the sideshaft that actuates an air valve mounted to the casting I refered to in the last sentence , from that valve there is a steel crossover line to the head and there is a check valve where it injects to the combustion chamber.

This a video of my single flywheel industrial engine with the cam timed air injection after I reset the timing.
   https://www.youtube.com/watch?v=VK8-9ofwM4M

Jake65mm

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Re: air starter
« Reply #6 on: February 15, 2017, 04:55:23 PM »
In this video you can see the mounting face I was talking about.
https://www.youtube.com/watch?v=ECNcxpDrPv4&t=29s

mikenash

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Re: air starter
« Reply #7 on: February 15, 2017, 06:14:28 PM »
In this video you can see the mounting face I was talking about.
https://www.youtube.com/watch?v=ECNcxpDrPv4&t=29s

Hey Jake, thanks.  A manual option as well as an auto-timed.  That makes sense

Interesting detail the single/twin flywheel being industrial - vs - agricultural.

Thanks