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Author Topic: Pipe Engine Set up's  (Read 701 times)

Offline Gary Anderson

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Pipe Engine Set up's
« on: March 01, 2012, 10:25:28 AM »
Hi guys,
I've been running pipe type engines for a few year's and have a few questions. First I noticed that some run their pipe set up using a pressure system and others don't. I was told not to pressure the tank?? There is a couple that is running pipe at our field and they have their tanks on pressure and they seem to do well, not sure what engines they're using. I love running my OS 40 FSR she is a real sweet heart. I'm also running a OS 40 VF and a OS 46 VF and I notice a slight change in R's when heading into the wind on windy days. I don't notice that change when I'm running the Brett Version Ro Jett 61. Is there pro's and cons running a pipe engine on a pressure system?? If I set her up on a pressure system will the R's change???

Another subject, I notice most guys burp their engine before they set them up to run for a flight. I never burp my engines and they seem to do just fine. After I start my engines I screw around checking tac setting, move all my junk outside of the flying area, so I feel the engine has had enough time to clear out anything that could have been in her?? Also I notice none of the big boys use a starter to start their engines??? Why not use a starter, most of the time mine start on the first flip, if not the trusty starter is ready to be used. How come the big boys don't use a starter. I've watch many flipping their engines for several minutes before she'll take hold and run. Why not use a starter, what is the pro's and con's with a starter. If the engine turns over easy bye hand I don't believe the starter is going to hurt her???
I appreciate your input.
Gary
« Last Edit: March 01, 2012, 03:41:25 PM by Gary Anderson »
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Offline Steve Helmick

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Re: Pipe Engine Set up's
« Reply #1 on: March 01, 2012, 03:23:12 PM »
Gary, you'll find that some guys don't like muffler pressure, and some do. I suspect the same applies to pipe pressure. It's not that it can't work well, but those who don't like muffler pressure are not going to like pipe pressure. To be honest, I have seen a G.51 on muffler pressure have the muffler gasket (a bad idea) blow out, and the engine went seriously lean for the rest of the flight. I like muffler pressure, but decided that probably gaskets were a bad idea. A constant, consistent leak is not a big deal, but any change in the leak during flight is very bad.  I've yet to have a problem caused by muffler pressure, and I like it, tho I was predisposed not to, under the theory of "simplicate and add consistency".

One thing I noticed about Bruce Perry's first ***JESTER*** was that he had the uniflow vent pointing straight down. I asked why, and he said to prevent the rich/lean cycle due to the wind, and I believe he got that tip from Randy Smith. It seems to me like it would tend to siphon, but it doesn't. No idea why not. Some guys put the uniflow vent inside the cowl, or have the vent in the backplate cavity. Whatever works for you is the thing to do, IMO.  That said, I'm a newbie to pipes, but have not used pipe pressure, or seen any reason to. However, I do have trouble getting both engines wet enough (.46VF and PA .51) for reliably good starting.  :-[ Steve 
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Offline Bill Little

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Re: Pipe Engine Set up's
« Reply #2 on: March 01, 2012, 03:29:18 PM »
Hi Steve,

We always burp the engine prior to the first flight.  Just fill up the venturi and flip.  We use a syringe to prime.

BIG Bear
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Offline Balsa Butcher

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Re: Pipe Engine Set up's
« Reply #3 on: March 01, 2012, 04:36:50 PM »
Engines vary...some like muffler pressure, some don't. Easiest thing is to try it both ways. I usually end up with just uniflow pressure. Ro-Jetts seem to vary very little in the wind so I don't use it on mine.  Starter? We ain't got no starter! We don't need no starter! We don't have to use any stinkin' starter! (with apologies to Alfonso Bedoya and the film "The Treasure of the Sierra Madre.)  8)
« Last Edit: March 01, 2012, 07:16:26 PM by Pete Cunha »
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Offline Ted Fancher

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Re: Pipe Engine Set up's
« Reply #4 on: March 03, 2012, 10:12:27 AM »
There is nothing "magic" about hooking up a line between the pipe/muffler and the fuel tank.  What doing so does is to make the pressure source to the tank [more] constant.  This may or may not be helpful and it is wise to run your powertrain both ways to learn the effects of doing so.  The modest difference may make it worthwhile to go one way or the other under specific circumstances.  The one thing you can be reasonably sure of is the need to adjust the needle valve when switching from one to the other, particularly with mufflers since most expansion types tend to provide greater pressure than atmospheric.  Depending on where the pressure tap is located in a pipe the pressure effects will be different and thus care must be taken to adjust the needle carefully.  If tapped in a narrow or expanding part of the pipe [higher velocity/lower pressure] the pressure may be lower than atmospheric requiring a richer setting, but if in the widest part of the pipe (lowest velocity/highest pressure) the pressure may be higher and require a leaner needle.

Think of pressure/non pressure as a tuning device rather than a "given" positive or negative.  Much like using uniflo or non uniflo for specific conditions.  Switching a uniflo to non-uniflo will result in a bit more oomph toward the end of a pattern which may be beneficial under adverse conditions whereas uniflo will result in a constant run from beginning to end thus not providing a bit of boost for the verticals and above 45 stuff at the end of the pattern.  No problem in stunt heaven but in calm or gusty air the non-uniflo set-up might make a small difference that could save the day for you.  Again, the needle setting may be slightly different so you want to experiment with both during a practice session so you know how your powertrain will react and what small adjustment might be necessary to your needle setting prior to launch.

One caveat re uni/non-uni.  If, as I do, your uniflo vent inside the tank is not centered vertically you may get a different lap time inverted versus upright when you switch between one and the other type of system.  When testing the two types be sure to pay attention to that distinction--if any.  If significant, you might choose to forgo changing from one to the other as being more of a negative than a positive.  Gotta test it and pay attention!

Ted Fancher
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Offline Gary Anderson

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Re: Pipe Engine Set up's
« Reply #5 on: March 05, 2012, 01:01:36 PM »
Hi Ted,
Thank you for your input, I have two different set ups for pressure. One has a fitting in the flange of the header pipe and the other has a fitting located in the fat part of the carbon pipe. It will be interesting to see if it makes a differents running the two different set ups. I've had such good luck running my pipe engines without pressure but its like ya say, don't know for sure until ya screw it up. The OS's seem to be very senitive on windy days, ya can hear when she entering the wind. My Ro Jett 61 Brett Version doesn't seem to change, just always a sweet heart. I've been using clunk tanks with my pipe engines and they seem to like them, so I'm not going to change tanks.

A little different subject, I have a Super Tigre 51 reworked by Mr. Bowman and the only way she like to run is on a pressure tank set up. The Tigre seems to love the little short tongue muffler and is doing a great job pulling my Legacy around. The engine is running a nice wet 2 cycle to a leaner two cycle and sounds very cool. Like Pete said each engine likes different things. To me pipe engine set up is the best of the two worlds.
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Gary Anderson

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