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Author Topic: Reed valve engine trouble  (Read 1822 times)

Jim Roselle

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Reed valve engine trouble
« on: September 10, 2013, 11:55:45 AM »
Having trouble with a bladder fed cox reedie. Flying with 18% nitro and a 4.75x3 prop. The Venturi is bored 3/16 all the way through and 7/32 to just past the spraybar, to maximize airflow past the spraybar.
Here's the setup:



I am launching at 20,400 rpm and it screams in straight and level but bogs down and coughs in maneuvers. I am thinking that it can't maintain the high rpm the big Venturi needs so it falls off the powerband. Here is video with the 4.74x3 prop. I wish I had shot video of the 5x3 as it was dramatically worse.


Comments, suggestions?

Thanks,
Jim
« Last Edit: September 10, 2013, 12:13:29 PM by Jim Roselle »
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Offline kenneth cook

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Re: Reed valve engine trouble
« Reply #1 on: September 10, 2013, 01:36:28 PM »
            Jim, it certainly is loading in the maneuvers. Did you try and launch a click richer? Seeing your using bladder, the venturi is really a non issue. It's not needed. So I would check to make sure the crank doesn't have castor varnish on it and also inside the case itself. If that is a Cox black trimmed down, and it's loading, either trim a additional 1/8" off or try a APC 5x3 which has narrow blades. Upping the nitro  may assist a little more but if the engine is overcompressed, sagging is going to result as well and addtional head shims may be required. I would absolutely check to see that your fuel tube isn't flopping in the maneuvers as this could be leaning the engine in the hard maneuvers. Ken
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Jim Roselle

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Re: Reed valve engine trouble
« Reply #2 on: September 10, 2013, 01:52:54 PM »
Quote from: kenneth cook on September 10, 2013, 01:36:28 PM
            Jim, it certainly is loading in the maneuvers. Did you try and launch a click richer? Seeing your using bladder, the venturi is really a non issue. It's not needed. So I would check to make sure the crank doesn't have castor varnish on it and also inside the case itself. If that is a Cox black trimmed down, and it's loading, either trim a additional 1/8" off or try a APC 5x3 which has narrow blades. Upping the nitro  may assist a little more but if the engine is overcompressed, sagging is going to result as well and addtional head shims may be required. I would absolutely check to see that your fuel tube isn't flopping in the maneuvers as this could be leaning the engine in the hard maneuvers. Ken
When I launch richer it just exacerbates the problem. I installed a new backplate that isn't as aggressively bored. It lost about 1000 rpm on the bench but I won't have a chance to test fly until tomorrow. It's the same type of backplate I was using on the engine before it started doing this so we'll see.

Jim
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Offline Dan Berry

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Re: Reed valve engine trouble
« Reply #3 on: September 10, 2013, 09:14:50 PM »
More nitro. 25-30%.
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Jim Roselle

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Re: Reed valve engine trouble
« Reply #4 on: September 11, 2013, 05:24:27 PM »
Rerouted the fuel line and it sorted things out. I think my next batch of fuel wil be higher nitro.
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Offline Ron Cribbs

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Re: Reed valve engine trouble
« Reply #5 on: September 11, 2013, 09:27:16 PM »
Good flying Jim, little rough on the landing though...

The 30% Powermaster is working well for me. They only ever have it by the gallon so buy a lot of Castor. I mixed mine in the quart can so as not to use up all my oil in one shot.
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Jim Roselle

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Re: Reed valve engine trouble
« Reply #6 on: September 11, 2013, 10:15:26 PM »
Quote from: Ron Cribbs on September 11, 2013, 09:27:16 PM
Good flying Jim, little rough on the landing though...

The 30% Powermaster is working well for me. They only ever have it by the gallon so buy a lot of Castor. I mixed mine in the quart can so as not to use up all my oil in one shot.
I have a place locally that has  the 30% for $25 so I'll be doing that after I go through the gallon of master basher I just bought. Yeah, rough landing the lines hung up on the handles set screw. Man I made vertical eight right before they got caught too!

Jim
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