Author Topic: 12-2 Air over Start  (Read 437 times)

multis6

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Re: 12-2 Air over Start
« Reply #15 on: August 05, 2019, 11:08:52 AM »
Well this is the 3ed time trying to get a reply out......
Bruce it sounds & looks like you have spent quite a bit of time and thought building your system. Well done & thanks for the pics.
It is interesting to see how individuals have taken the basic engine and adapted there own technologies to fit there needs.
Talk about basics...... I crank my 12-2 Metro 5 revolutions then stomp on a peddle to pull a string to swing the decompression lock out of the way, then on the 6th rev. I push it through the compression stroke and off it goes. So yes a more elegant starting method is due.
It looks like a bit more work with the Gast air motor (assist) will be the way to go for now.

multis6

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Re: 12-2 Air over Start
« Reply #16 on: August 05, 2019, 11:59:49 AM »
FYI:   Here is my 12-2 Metro with the Gast motor set and ready to be plumbed.

BruceM

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Re: 12-2 Air over Start
« Reply #17 on: August 05, 2019, 03:51:59 PM »
Nice photo of your 12-2. The massive size and weight of the 12-2 always blows me away. That's an engine!

That looks like a very large air motor that will be a challenge to feed enough air to.  You'll want a considerably smaller diameter roller, I think, under 3 inches diameter, with moderately soft rubber for good grip. 

Air motors are very different compared to electric in that they have no extra torque on starting or bogging down, HP is only reached at RPM and falls off below it to nil.  Stalled motors just sit there harmlessly hissing and have little torque.  This is good for my air router; if it hits a knot it just just stops instead of blowing out the wood.  Less ideal for my table saw or a starter motor trying to spin up.




dkmc

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Re: 12-2 Air over Start
« Reply #18 on: August 05, 2019, 04:14:23 PM »
Yes, nice looking setup. Maybe I'll get an in person tour of that engine room soon.

38ac

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Re: 12-2 Air over Start
« Reply #19 on: August 05, 2019, 09:14:19 PM »
I see you got one of the Metros twins with the camshaft drilled and assembled incorrectly  thus the number 1 cylinder has the exhaust and intake ports reversed. What are you planning to do with the number 2  intake since your exhaust piping crosses  in front of it?  You can put things the way they  should be with a correctly assembled camshaft. On a twiin the intake ports are the center two and the  exhausts  are the outside two.
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dkmc

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Re: 12-2 Air over Start
« Reply #20 on: August 05, 2019, 09:23:55 PM »
Mine's the same way Butch. But this is all new to me, so I'd be real appreciative for more details on this.
Here's an ignorant question.....what harm does it do to the engine with it set up as in Greg's picture?
« Last Edit: August 05, 2019, 10:04:32 PM by dkmc »

38ac

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Re: 12-2 Air over Start
« Reply #21 on: August 05, 2019, 11:18:40 PM »
None that I am aware of assuming they have the lobes installed so they are doing the correct thing as they are different.  Makes for some odd manifolding
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multis6

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Re: 12-2 Air over Start
« Reply #22 on: August 06, 2019, 11:31:04 AM »
Yes the intake on the one head is different than the original configuration ( I'll just extend the intake out a bit to accommodate an air filter.) but what's really WRONG is the cooling ports. They used the same head on both cylinders and the piping needed to be reduced in size due to the lack of room on the side of one of the heads, so the out flow is restricted to make the piping fit in to the space. There is no way that the engine would run on convection cooling, so I needed to install a coolant pump to push enough coolant through the engine to pull off the BTUs Not sure if it will actually cool sufficiently at full rated load. I have not hooked up an 8K load bank to or dino to make it work at max power for a period of time.

I see that McMaster has the rollers needed for the air motor that's a help now to find one that has a good grip. One draw back of the air start system is the size of the receivers (air tanks) needed to hold a starting charge. But its a one time expense in dose not need to be replaced every 6yrs like batteries. Just need to find the room for tanks.

38ac

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Re: 12-2 Air over Start
« Reply #23 on: August 06, 2019, 12:17:55 PM »
Your comment about the cooling ports confused me so I had to take a second look at the pic. Ahh, you have a direct injection engine with the side cooling ports in the head.
 First time I have actually seen a D.I. twin. India made a very compact elbow fitting for that. I have one in the shop,,somewhere,,,,
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veggie

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Re: 12-2 Air over Start
« Reply #24 on: August 07, 2019, 01:33:50 AM »
The Youtube link says 'video unavailable'

EDIT: This one works
https://www.youtube.com/watch?v=qbcbuygYJdM

Thanks dkmc ... I fixed the link

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dkmc

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Re: 12-2 Air over Start
« Reply #25 on: August 07, 2019, 02:34:14 AM »
First time I have actually seen a D.I. twin. India made a very compact elbow fitting for that. I have one in the shop,,somewhere,,,,

Butch, perhaps it's been discussed on here before, but can you explain why they are made in IDI and DI models?
Is there an advantage to either design?

[/quote]
Thanks dkmc ... I fixed the link
cheers!
[/quote]

You are very welcome Sir.

38ac

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Re: 12-2 Air over Start
« Reply #26 on: August 07, 2019, 12:24:30 PM »
No I cannot explain why with certainty. Personally I like the ignition crack ;) of the DI engines. They do start easier in cold weather. My old shop wasn't heated full time and one winter morning it was 0 F in there. I had a Metro 6/1 DI at the time and swung it over and it fired right off like summer time
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Fig

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Re: 12-2 Air over Start
« Reply #27 on: August 15, 2019, 03:36:45 PM »
We have some air friction motors like that at work. Ours have a small airbag that applies pressure to the motor so that the friction occurs. The bag deflated and the motor moves away from the friction point. Pretty simple process.

BruceM

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Re: 12-2 Air over Start
« Reply #28 on: August 15, 2019, 04:23:44 PM »
Air cylinders are  commonly used for engagement of the air starter motor; they are dirt cheap and force can be tailored via smallest pressure regulator or by selecting the right cylinder diameter.