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  #1  
Old 10-17-2011, 08:25 AM
LettersFromFlyoverCountry's Avatar
LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
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Default Alternator blast tube

I really don't like the look of the alternator blast tube on the nose ramp on the baffle. In order to stay in place, the conduit (the plastic hose Van's sells as the blast tube), has to sit above the ramp. I also put some RTV around it to try to hold it in place. I just don't like the way it looks, and it doesn't strike me as promoting a particularly smooth air flow.

What would be better is a hose inlet like what's on the back of the baffling for the heater scat tubing, which would promote a nice smooth airflow into the tube (and a nicer appearance too), a screen to keep big junk out of the alternator area, and a more secure connection (via a clamp).

But I haven't found any anywhere that fit this conduit size. Has anybody? Or is there a better design out there I could use as an alternative?
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  #2  
Old 10-17-2011, 08:59 AM
jarvis jarvis is offline
 
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Default Bob...

If I understand correctly--you're wanting a 3/4" tube flange. Darrell Reiley was selling them--not sure sure if he still does. Bought a couple--beautiful workmanship.
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Last edited by jarvis : 10-17-2011 at 09:11 AM.
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  #3  
Old 10-17-2011, 09:19 AM
Paul K Paul K is offline
 
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Default 3/4 flange tube

I bought 4 from Darrell and only used 3. Have one left if you are interested.
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  #4  
Old 10-17-2011, 09:37 AM
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Rick6a Rick6a is offline
 
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Lightbulb

Quote:
.....is there a better design out there I could use as an alternative?
Bob,

An alternative method for attaching blast tube is to use scat tubing attached to an aluminum flange with a band clamp. It is arguable that a screen is really needed in this application. In any event, aluminum flanges are available in several diameters at Spruce:

http://www.aircraftspruce.com/catalo...uctflanges.php

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  #5  
Old 10-17-2011, 09:40 AM
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Dan Langhout Dan Langhout is offline
 
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Default Blast Tube

(Edit) Woops! Rick beat me to it!

Problem is, what Van's sells you as a blast tube is actually just a piece of nylon conduit - exactly the same as 3146K24 "Continuous-Flex Nylon Conduit and Fittings" from McMaster-Carr. I have bought this from both places and as far as I can tell, it's the same stuff.
It's ID is about 0.69" - too small for 3/4", a little big for 5/8".

I think I would be inclined to use the 1" version of these aluminum flanges from Aircraft Spruce with a piece of 1" scat tube.

FWIW
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  #6  
Old 10-17-2011, 09:59 AM
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LifeofReiley LifeofReiley is offline
 
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Default Location of flange

Just FYI here... without a small deflector mounted behind and bent over the flange mounted on the inlet ramp (depending on the flange location) you actually create a vacuum through the scat from the alternator pulling hot air through the alternator to the inlet ramp. This is not what you're looking for as the goal is to blast cool air to the voltage regulator area of the alternator.
You don't want to much volume of air as you can change pressures under the cowl pretty quick... 3/4" seems to work the best IMHO.
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  #7  
Old 10-17-2011, 10:58 AM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
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Default

Quote:
Originally Posted by Paul K View Post
I bought 4 from Darrell and only used 3. Have one left if you are interested.
I'm interested. Can you send me a PM with the deets? and thanks.
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  #8  
Old 10-18-2011, 10:44 AM
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NDrv8r NDrv8r is offline
 
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Default

Quote:
Originally Posted by LifeofReiley View Post
Just FYI here... without a small deflector mounted behind and bent over the flange mounted on the inlet ramp (depending on the flange location) you actually create a vacuum through the scat from the alternator pulling hot air through the alternator to the inlet ramp. This is not what you're looking for as the goal is to blast cool air to the voltage regulator area of the alternator.
You don't want to much volume of air as you can change pressures under the cowl pretty quick... 3/4" seems to work the best IMHO.
Interesting statement. I have almost the exact same configuration, and basing the flow from my heater (1.5" scat) , there is a lot of pressure in this area. In addition on the left side of the engine is the inlet to the snorkel. I do think I am not getting all the MP I should get, but that is another thread.

Obviously a vacuum is not good for a alternator blast tube, could you point out to me how you came to the conclusion there is not positive pressure between the top side of the inlet ramp to the bottom side where the alternator sits? If my set up is not right, I need to think about changing it.
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