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Pressure Fitting

Old 06-06-2008, 09:27 AM
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Default Pressure Fitting

Approximately 20 years ago I had a G-51 Ring and S-61 ringed engine on separate planes. The pressure fittings were installed at the plant but when a pipe fell from a plane in flight I ordered a couple of replacements. Pressure fittings were in the boxes with the new pipe but not installed. My first attempt promptly twisted off with very slight pressure. I robbed the fitting from the other replacement pipe and gingerly installed it on the pipe. Only used the plane a few times after that and then sold everything and left the hobby until this year.

This year I purchased a new G-75 ring in a LHS because it still had "Made in Italy" on it and I learned they have moved production to China now. And, the fitting was missing from the box. Everything else was included so I had my LHS order me a couple of fittings. Rummaging around in the garage I found that replacement pipe from 20 yrs ago but it was for the 40-51 size engines and wouldn't you know it - the broken fitting was the only one in the box.

While waiting for the new fittings to arrive I went to a different LHS to see if they carried any in stock. The gent wasn't sure of the thread so he pulled one from a new engine to check. The second he went to screw it back in to the pipe it twisted off. Almost no pressure was needed. I felt bad that happened because he was trying to assist me.

Picked up my new fittings Wednesday and installed one last night in my new engine. Used blue loctite and the newer fibre washer that came with them. Hand tightened as much as I could and then ever so slightly turned with a small wrench. To me its not in snug enough but I'm afraid to apply any pressure for fear of stripping it apart.

Why isn't one installed at the factory?

Why hasn't a more sturdy fitting (Stainless Steel) been provided?

Surely others have encountered this.

Genuinely wish to know the why's as well as the best way to securely install one without fear of breaking it or having it work loose.

Regards,

Clay
Old 06-09-2008, 10:15 AM
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Default RE: Pressure Fitting

Fittings aren't installed at the factory because they're not always needed.

The brass fittings supplied have done very well for several decades, so there's really no reason to change.
Old 06-09-2008, 11:23 AM
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Default RE: Pressure Fitting

So far the one I just installed so gingerly seems to be working although its clearly a weak link in my estimation. I certainly hope you're right Bax.

Fired the new engine up Saturday for the first time and it ran very smoothly at 8600rpm on first tank 3 turns out. Second tank saw 9600rpm and 4th tank was giving 10800rpm. Prop is a 12X7 APC.

The factory glow plug wouldn't sustain the engine when I removed the glow starter on the 2nd tank so I installed a Fox plug and she's still going. The mid-12000's I've found you recommend for the G75 seems a long way off but hope this puppy just gets stronger.

BTW, my best idle seems to be at 3900ish rpm. Is this something that will improve with a few more tanks?

Regards,

Clay
Old 06-10-2008, 09:35 AM
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Default RE: Pressure Fitting

Once it's well-broken-in, you should be able to easily get a low-speed setting below 2,700 RPM. We can usually get below 2,500.
Old 06-14-2008, 04:30 PM
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Default RE: Pressure Fitting

Starting to grow more confident in it now Bax. Was able to get 2380 idle on the stand and 11,400 peak (properly leaned). Not sure how long it would hold that low of an idle but long enough for most stuff. With only a half gallon thru it I'd think it'll improve in all respects with some more run time.

Thanks,

Clay

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