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Inverted OS .46 Floods

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Inverted OS .46 Floods

Old 07-10-2013, 12:52 PM
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Aug
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Default Inverted OS .46 Floods

I have a PC-9 with an inverted OS .46. The engine will not idle and the fuel gravity feeds out the carb. I can't relocate the tank any lower. Is there any other way around this problem? Thanks.

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Old 07-10-2013, 12:58 PM
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Scar
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Default RE: Inverted OS .46 Floods

Yes, a Cline regulator will allow you to operate without changing tank or engine position.

Good luck,
Dave Olson
Old 07-10-2013, 01:20 PM
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Jetdesign
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Default RE: Inverted OS .46 Floods

I don't see why you can't move the tank lower. In that picture it looks like the tank is toward the top of the plane since it's inverted. Can you cut away more of the 'firewall' and add support at the opposite side? What about a different shape (longer, lower) tank?
Old 07-11-2013, 05:59 AM
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JohnBuckner
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Default RE: Inverted OS .46 Floods

gaRCfield is quite right and the tank is too high to avoid syphoning and hydrolocks continually. It will never function properly with a conventional glow engine fuel system without a regulated/pump system such as Dave mentions. That's the bottom line and it does not matter if that's the way the manufacturer has set it up. Fact is a lot of product these days may not even have been properly flight tested and you cannot always count on the 'instructions'

Here are your options:

1. Use a smaller (shorter) tank so it does not protrude into the wing compartment I realize its the wing that is the reason you cannot lower the tank lower.

2. actually cut a channel into the top side of the wing that will allow you to lower the tank a little (this without cutting into the main spar or the leading edge spar. It sounds like a lot of work but its not really and I have done this successfully several times on pylon racing warbirds.

3. Go to a regulated/pump system. These may be rather expensive not sure or not sure of the current avalibilty of the Cline units.

4, Last options is to simply rotate the engine ninety degrees, This will raise the carb likely enough to stop the problem. A bit more work but costs nothing and you will have to make ample cutouts on the cowl. This last reason is what causes so many problems with new folks and it that complete unwillingness to make ample cutouts or holes for things such as needle valves (high and mid range) cooling air both in and out or simple letting a cylinder head protrude making easy glow access.

If you are interested in option #2 I will make some more photos of the wing cutouts on one of my ships and how its done. I don,t think I have any in my files highlighting that.


John

Old 07-11-2013, 06:22 AM
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Default RE: Inverted OS .46 Floods

I'm with you John on #4. Unless I am dying to hide my engine via the inverted choice, I always mount my engines sideways and never get the probs of running engines inverted where the tank is significantly higher. A club buddy was having probs running inverted just a couple weeks ago. He was using a GP mount which has the same bolt pattern inverted and sideways, so I suggested the easy fix to just turn the engine sideways. He had to reroute throttle linkage but he said it was easy, and of course had to cut new holes in the cowl. BUT he is one happy camper with the engine now...running reliably and flying a lot. Jon
Old 07-11-2013, 03:29 PM
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Aug
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Default RE: Inverted OS .46 Floods

Thank you for your advice. I did lower the tank and while I was at it I checked the clunk and all the lines. The stopper is tight. Everything was right but I'm still having trouble getting it to run without stalling at lower speeds. I and others have tried all kinds of settings for low speed and needle valve and I've changed the glow to a brand new one. Same thing. Here is a photo of the tank lowered. Should I try a new needle valve?

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Old 07-11-2013, 05:31 PM
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stick
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Default RE: Inverted OS .46 Floods

Did the lowering of the tank stop the fuel from siphoning? Are you using a plug with an idle bar?
Old 07-11-2013, 06:56 PM
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Aug
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Default RE: Inverted OS .46 Floods

Fuel still drips out although not as bad. I never use plugs with bars.
Old 07-11-2013, 07:04 PM
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Aug
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Default RE: Inverted OS .46 Floods

I will try a smaller tank. Good idea! If I still have problems I will have to give up on cosmetic flaws in the cowling and re-mount the engine on an angle. If the smaller tank works I'll update you. Can't thank you enough............ All of you guys!
Old 07-11-2013, 07:10 PM
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Aug
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Default RE: Inverted OS .46 Floods

I never knew about a cline regulator. Learned something. Thanks!

http://www.billsroom.com/pcfs/default.html
Old 07-12-2013, 04:39 AM
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Aug
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Default RE: Inverted OS .46 Floods

I tried to install a smaller tank but there is a second bulkhead nearer the firewall that still prevents it from sitting lower. If I can't get a Cline Regulator I'm going to have to mount the engine on an angle or sideways. Regrettably this is really going to mess up the cowling and I may even loose the cosmetic exhaust port. Too bad it really looked nice.
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Old 07-12-2013, 06:03 AM
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Default RE: Inverted OS .46 Floods

Aug you need to get over the cosmetic thing, "cosmetic flaws in the cowling" and the resultant angonizing over them has killed more nice airplanes than you can imagine that's a fact. Just rotate the engine a bit and be done with it, nobody cares about the dumb plastic exhaust pipe except you

Sure the cline pump would work but think about that 75 bucks, is that plastic pipe in the cowl worth that to you. This airplane is very poorly thought out for an inverted installation, for such an installation to be successful the airframe needs to have a sufficiently deep bodied fuselage immediately behind the firewall and that one does not.

Here are a few extra practices to observe when operating an inverted engine in airframes where it is practical:

1. Never fill the tank and leave the airplane sit in the sun. As the fuel heats up it will expand and can start a syphon or worse cause a hydro lock if the crankshaft of of a two stroke engine is in the wrong position.

2. With a two stroke glow engine always have an accessitble loop of the carburetor line outside the cowling and after fueling use a hemostat on this loop and do not remove until the point you are ready to start the engine.

3. At the point you are ready to start the engine without fail do not forget to manually turn the engine over with vigorus flips to check for hydro lock before ever touching it with an electric starter.

4. At anytime that hydrolock is detected always remove the plug Turn the engine over vigorously with no plug then using your ignitor attach it to the plug before reinstalling for around ten seconds to allow it to burn off the gunk.

5. When carrying the airplane when tanks are fueled or empty never carry it nose down always nose up. If you have a helper make sure they know that.

6. Even when the tank is emptied what can happen when the airplane is carried nose down is if the crankshaft of a two stroke engine is positioned just right and the engine mounting orientation is just right all the gunk of previous flights that remain in the muffler can and will drain right back into the cylinder head and next time you hit it with with a starter without checking, Well?


So Aug think about if the pretty little exhaust pipe on the cowl is worth the 75 bucks for a Kline pump or the need for all those extra operational steps I just outlined above.

John


Edit: I just added a photo that illustrates the use of hemostats for a full inverted installation that I outlined above in step #2. Notice the medical hemostats that lock have been clipped on that external loop of the ling that goes to the carburator so this airpane has been fueled and on the ready parked in shade. This little loop also serves as the best place to fuel from with a simple cut at this location and therefore only a two line system is required.

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Old 07-12-2013, 06:20 AM
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Default RE: Inverted OS .46 Floods

Years ago I bought a Cline regulator for a similar problem. Never got the plane running right with the cline. Additionally, the install requires drilling a hole in the engine back plate and installing a pressure fitting. Then after one discovers that the Cline doesn't work, that hole has to be plugged. And there must be room in the cowl to mount the regulator next to the carb.
Old 07-12-2013, 08:05 AM
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Aug
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Default RE: Inverted OS .46 Floods

Thanks for all the great tips John. My informal club situation does not allow me to pick brains at meetings like this in this forum. Very helpful and many thanks again.
Old 07-12-2013, 09:28 AM
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Default RE: Inverted OS .46 Floods

Thank you Aug and that is why most of the regulars are here and only wanting to share

That's interesting Airbusdrvr about the cline having never used one I had always wanted to give it a go sometime but just never got there maybe put it in the category of someday when I get one on a buyout or something

John
Old 07-12-2013, 09:48 AM
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Default RE: Inverted OS .46 Floods

Purchase an on-board glow unit.
Old 07-12-2013, 10:05 AM
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Default RE: Inverted OS .46 Floods

I say stay at it and dont re-orient your engine. I have a U-CAN-DO with inverted OS46 that runs just fine. It is a matter of getting your tank correct height. Just my opinion.

Chad
Old 07-12-2013, 10:32 AM
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Default RE: Inverted OS .46 Floods

I was having the same problem with the same model, but I am running a TT.46 in my PC9. I asked for help from some of the guys in my club and they told me to use my hemostats, or another set of locking pliers and close of the fuel line to the engine before fueling, once the plane is fueled, remove the pliers and start the engine. When I started taking this step, the engine ran great.
Indy Park Flyer
Old 07-12-2013, 12:52 PM
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Default RE: Inverted OS .46 Floods

I had a plane with an upright OS20, but the tank mount was very high and I used Indy's method.  I used one of those plastic fuel clips, but basically the same thing.  Once I started the engine it ran fine.  Also, instead of just using a "smaller" tank, you might look at a homemade tank out of something like a spice bottle.  Some of those are long and skinny and will fit where a standard tank won't.
Old 07-12-2013, 04:31 PM
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Default RE: Inverted OS .46 Floods

UVery difficult to 'flood' an inverted engine...the fuel just drips out of the carb, unless you actually choke the thing, and rotate the prop the fuel cannot get into the engine. So the problem then is just the fuel dripping out of the carb. Most upright engines don't do that, so the problem is simply the tank position. And yet the tank should be in the usual place...that is, centre line of the tank about the level of the needle valve, as always. Unless you get the tank in that position, then as suggested, to stop the fuel leaking out then simply close off the fuel line, or, close off the vent. Either way will prevent fuel leaving the tank. My problems with inverted engines has always been the idle...can't get my inverted engines to idle anything like upright...they always load up and put the fire out...so I just accept higher idle speeds for inverted engines...FWIW.
Evan, WB #12.
Old 07-12-2013, 05:26 PM
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Default RE: Inverted OS .46 Floods

+1 to the hemostat. I have 2 planes that have these applied before fueling and removed immediatly before starting.
Both will idle fine.
Old 07-12-2013, 06:31 PM
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Default RE: Inverted OS .46 Floods

Interesting why some one has not mentioned the Perry pump mounted above tank level works for me, and leave throttle open when aircraft not being used just in case.
Old 07-12-2013, 06:46 PM
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Default RE: Inverted OS .46 Floods

Aug,
Here's one more idea ...
Replace the "O" ring on the high speed needle. If this "O" ring dries up, or is damaged, your engine will never run or idle right. Plus, this could be the reason fuel leaks through the carb.
I have several planes with inverted OS engines. I never had the problem you describe.
Old 07-12-2013, 08:52 PM
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DISCUS54
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Default RE: Inverted OS .46 Floods

Inverted 2 strokes are notorious for the issues that you are experiencing. Hemos are good for in-between flights and storage as they will stop the siphoning but at some point you need to regulate fuel flow when you are ready to start the engine. You don't need to move the tank if you use a regulator or pump like the Cline (highly recommended), Iron Bay also makes one. These regulators are to give you a reliable idle and transition in any attitude (inverted, knife edge, ect.) and for that reason are quite popular with Slabs/Profile airplanes. As you are aware it is very difficult to keep a 2 stroke glow plug red hot with the inverted mount because all of the excess fuel gravity flows into the plug and then you have a wet plug. Wet plugs don't work and you waste a lot of time "changing" the wet one for a dry one. You can try plugs with idle bars and other crap stuck on them but that is treating the symptom and not the cause. If your stuck on the inverted mount for scale reasons you can install an on board glow driver that will "light" at a low setting and keep the plug hot. Nelson use to have a great one. The simplest and most cost effective is to simply mount the engine horizontally and that will solve most of your issues, you might still need the regulator if your tank is too far away or too high or low. You might also consider starting your engine with the airplane inverted on a stand and then once running turn it over...easily done with a 40 size airplane. Good luck.
Old 07-13-2013, 03:39 AM
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Default RE: Inverted OS .46 Floods

When the engine is running the tank is pressurized. Therefore more fuel is provided than what gravity can provide. So tank location is not the problem. The excess fuel that builds in the bottom of the case of an upright engine is just gathering in the head of the inverted engine. A higher idle or on board ignition are your best bet.

Please perform the simple test of inverting the plane and observe the idle characteristics. If the idle is fine then the problem is what I described above. If the idle is not fine then you have other problems.

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