RE: tower hobbies .46 engines  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> RE: tower hobbies .46 engines
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RE: tower hobbies .46 engines - 5/3/2008 5:16:23 AM   
Kermy7803



Posts: 49
Joined: 8/6/2003
From: Tehachapi, CA, USA
Status: offline 		I lied Apparently, I didn't check all my nipples..lol Looks like my muffler nipple was loose!! I guess I got to busy checking everything else I didn't check that one.

After cleaning the engine, and making sure no debris was anywhere to be found. I started my engine, and just so happened to have the same fuel, and amount that was in it from yesterday when it died.

Got it tuned running good, and did the nose up / nose down treatment.... Big ol'e air bubble on nose down... Engine died as it has been. So, I took the tank out checked it for leaks, clunker etc... put it back in and when I went to put on the vent line to the muff. nipple it turned?!?!? Then I felt like a dumb A$$....

Although, I haven't run it since.. I have a feeling that maybe part of the cause, if not all of it. So, I think you were kinda right. When I was full of fuel it ran fine for a bit. Once it got to about half, and I did a nose dive my fuel pressure couldn't make up the difference because of a loose nipple....

That sound about right? lol



I'll give it shot in the AM hopefully (mother nature cooperating) and see what happens.. At least now I know everything is nice, tight, and clean!!!




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RE: tower hobbies .46 engines - 5/3/2008 7:09:01 AM   
opjose



Posts: 5354
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		Yup that sounds like you found the problem.



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RE: tower hobbies .46 engines - 5/10/2008 9:12:23 PM   
Kermy7803



Posts: 49
Joined: 8/6/2003
From: Tehachapi, CA, USA
Status: offline 		Still got issues?!? Everything is tight and clean. I am still getting an air bubble in the line on nose down... Driving me nuts?? I noticed at one point that, my tank would slide back and forth in the saddle as you did a nose up / down test.. Thought it was pinching the muffler line off... I managed to get it to stay. But it still gets an air bubble. It's acting like it is not getting enough pressure, at about 1/2 tank. But I can't figure out why. No holes or leaks I can detect, tank and clunker are working as they should...

Would putting steel wool in the muffler to act as a baffle increase pressure?? Looking for ideas.




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       Post #: 53

RE: tower hobbies .46 engines - 5/11/2008 5:39:20 AM   
opjose



Posts: 5354
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		The presense of air in the line, does not reflect a need for more pressure or the lack of pressure.

It indicates that the clunk or ( or tubing ) is letting in air.

With a FULL tank, you should not get air on a nose down test even at high angles..

At 1/2 tank, the clunk stays in the back, and it should be on the bottom of the tank. That means that if you angle the plane over 35+ degrees nose down you could start to uncover the clunk causing air to appear.

With only 1/3 tank of fuel this will happen at an even shallower angle.... say 20+ degrees.

Make sure that the clunk can travel relatively freely up and down, and side to side.

It would be nice if the clunk could also travel forward to stay with the fuel, but of course that could cause it to stick at the front, causing bigger problems.

Some people resort to putting in a short length of brass tubing so that you have an arrangement like this...

BTubing Stopper BTubing Silicon Tubing - BTubingSilicon TubingClunk

So you have your normal brass tubing going through the stopper, inside the tank you have a short piece of silicon tubing, to which is attached a piece of brass tubing, that will travel up and down but of course not bend, followed by a short piece of silicon tubing to which the clunk is attached.

The idea is to permit the clunk to move up/down and sideways but prohibiting forward movement within the tank.


I haven't done this myself.


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RE: tower hobbies .46 engines - 5/11/2008 6:56:30 AM   
DarZeelon



Posts: 6928
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: offline
quote:

ORIGINAL: opjose

The presence of air in the line, does not reflect a need for more pressure or the lack of pressure.

It indicates that the clunk or ( or tubing ) is letting in air.

With a FULL tank, you should not get air on a nose down test even at high angles..

At 1/2 tank, the clunk stays in the back, and it should be on the bottom of the tank. That means that if you angle the plane over 35º nose down you could start to uncover the clunk causing air to appear.

With only 1/3 tank of fuel this will happen at an even shallower angle.... say 20º+.

Make sure that the clunk can travel relatively freely up and down, and side to side.

It would be nice if the clunk could also travel forward to stay with the fuel, but of course that could cause it to stick at the front, causing bigger problems.

Some people resort to putting in a short length of brass tubing so that you have an arrangement like this...

BTubing Stopper BTubing Silicon Tubing - BTubingSilicon TubingClunk

So you have your normal brass tubing going through the stopper, inside the tank you have a short piece of silicon tubing, to which is attached a piece of brass tubing, that will travel up and down but of course not bend, followed by a short piece of silicon tubing to which the clunk is attached.

The idea is to permit the clunk to move up/down and sideways but prohibiting forward movement within the tank.


I haven't done this myself.



All true, Jose.


With the cost constraints most modelers have, the best solution would be a bladder-type tank...

This type of tank has a bladder full of fuel (only a small bubble of air, if any at all), within a 'normal' tank, which is pressurized by the exhaust. There is never any exhaust gas, or air, within the fuel's immediate vicinity.

The engine is impervious to picking up bubbles inside the tank and is even immune to airframe vibration, since there is no chance for any so-called 'fuel foaming' to ever happen.


If more of us will buy these bladder tanks, their price will become reduced, probably to the same level as a normal clunk-tank, since the bladder tank needs no clunk as such to work. The selection will also become greater than it is today.



Of course, this has nothing in particular to do with the Tower Hobbies .46 engine, but it is worth saying, since it can make flying more impervious to user setup errors.
The user will still need to place the tank at the same level as the venturi and as close as possible to the engine, however.

As long as some glow engines are not replaced by electrics, it still has some importance...



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       Post #: 55

RE: tower hobbies .46 engines - 5/11/2008 2:37:38 PM   
Ken6PPC


 

Posts: 623
Joined: 6/20/2006
From: Hamilton, OH, USA
Status: offline 		Dar, who markets bladder tanks, other than Jett?

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RE: tower hobbies .46 engines - 5/11/2008 3:42:57 PM   
Jezmo



Posts: 749
Joined: 6/26/2006
From: Spring, TX, USA
Status: offline 		A company called Tettra makes them also. Try this link.

http://www.darrolcady.com/Tettra_Tanks/tettra_tanks.html

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RE: tower hobbies .46 engines - 5/11/2008 4:31:48 PM   
DarZeelon



Posts: 6928
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: offline 		Ken,


I know for a fact Tettra make fuel tanks up to 20 oz.
Those in my LHS show two volumes; as a normal tank and as a bladder tank.

The larger tanks do not include the bladder, which must be obtained separately...

Unfortunately, Darrol Cady offers only minute sizes and even Dave Shadel only offers such tanks up to 6 oz.


They sell for $14 to over $18; three to four times the price of normal tanks.
And none offer the 8+ oz. size required for a .46 engine... Since nearly all the fuel is usable in all attitudes, however, maybe you don't need a much larger tank.


Edit: Looking into Central Hobbies, I found these tanks.



< Message edited by DarZeelon -- 5/11/2008 4:42:41 PM >

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RE: tower hobbies .46 engines - 5/11/2008 5:29:57 PM   
Ken6PPC


 

Posts: 623
Joined: 6/20/2006
From: Hamilton, OH, USA
Status: offline 		Thanks, Jezmo and Dar!

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