Where to get 4" flanges

RV7Guy · #1 08-04-2005, 12:08 PM

Hi all,

I'm going to remote mount my oil cooler and need 4" flanges. I searched ACS, Van's and a couple of others, any ideas? I haven't checked the aviation aisles at Home Depot and Walmart yet.

Darwin N. Barrie
*%&_g Baffling

Build9A · #2 08-04-2005, 12:34 PM

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

Looks like they have 4X4X1/4.

gmcjetpilot · #3 08-04-2005, 05:19 PM

I did not think you where talking about angles. I see that Spruce only goes to 3" on the duct flanges. Hummmmm

You could make your own? In fact buy just bolting on a flange to the baffle where you cut a 4" hole is not super good. The radi on the flange is too tight. A nice 1" radius would be nice. One word: Fiberglass

You could incorporate a "bell mouth" that extends into the plenum (upper engine area) to smooth out the airflow? May be overkill but it can't hurt and will produce less drag.

Have fun, repost if you find the larger dia. Cheers George

RV7Guy · #4 08-05-2005, 09:57 AM

Hi George,

You are correct, I am looking for the round flanges. I guess I'm going to be breaking out the foam, fiberglass and epoxy soon.

Darwin N. Barrie
P19

az_gila · #5 08-05-2005, 10:39 AM

Wonders of Google.....:^)

Try this out....

http://www.grow-light.com/cgi-bin/store.pl?item=430

or a smaller one....

http://www.grow-light.com/cgi-bin/store.pl?item=429

Apparently the hydroponic indoor gardening folks use 4 inch and 6 inch ducting for their airflow needs.

This might do what you want if you don't like fiberglas...:^)

...gil in Tucson

RV7Guy · #6 08-05-2005, 02:12 PM

Hi Gil,

Thanks for the contact. I ordered two after confirming they are metal. The picture looks like they could be plastic.

DArwin

OneTwoSierra · #7 08-08-2005, 01:03 PM

I have an RV-9A with 160 hp with remote mounted oil cooler and my buddy has an rv6 with 180 and a remote mounted cooler and we both use 3 inch round flanged fittings and 3 inch scat tube. i see oil temps right at 200-204 in the heat of texas summers. My buddy has already build a cockpit controllable door over his to keep his temps up in the winter. 3 inches has been plenty for us.

RV7Guy · #8 08-08-2005, 04:23 PM

The 4" tubing was recommended by Pacific oil coolers because of our extreme AZ heat. I'm confident 3" is adequate in most places in the US but here I'd rather have the 4" and not need it than having 3" wishing I had 4.

I'll shoot some photos when it is done.

Darwin N. Barrie
Chandler AZ

gmcjetpilot · #9 08-08-2005, 06:24 PM

If you forget all the engineering the area of the oil cooler face SW 8432R is about 27 in-sq and the 4" duct is about 25 in-sq. Hummmm A 3" duct area is only about 14 in-sq. With out any rocket science you might guess the closer the area of the duct to the area of the cooler face the better. (of course I ignored the "solid" part of the cooler face, fins and passages.)

A SW 8432R can flow or use well in excess of 40 LB/MIN or 530 CFM of air. At a certain point the heat rejection will not increase as much with a significant increase in air. The SW is very efficent up to 40-50 LB/MIN. The issue is can the duct system provide this amount of air or does it need to?

It is interesting that the 4" DUCT flange above is discribed as for use with a 265 CFM blower, in a ventilation / vent Fan application. No doubt the 265 CFM is not a limit of the duct but the blower and the pressure is can provide.

The amount of flow thru out the oil cooler "system" is a function of the pressure or force to push the air thru the duct and cooler. The size or cross section of the duct and the restriction of the cooler itself will determine how much air flow you get for a given pressure.

At 175mph you have about +14 in-H2O of total pressure available. How much of this free airstream dynamic pressure (the pressure of the air from the plane's forward velocity) is available depends on the efficency of the design up to the duct or cooler in the back of the baffle. It will be less than 14 in-H2O. There is no 100% pressure recovery.

The SW 8432R has (or needs) a 10 in-H2O pressure drop to achieve a 40 LB/MIN flow (about 530 CFM). 40 LB/MIN is at the upper end of the coolers max or optimal air flow to achieve the coolers max rated cooling. (Oil flow thru the cooler is a factor but we will ignore that.)

The smaller the ducts cross section the more pressure is required to achieve the flow.

If you want to run a SW 8432R at max flow, it will be easier with a bigger duct. Can a 3" work. Well yes obvioiusly it can work. However there is only so much pressure available the way we mount our coolers (in the back of the baffle) and so 3" will flow less than 4" (no rocket science here). What is likely happening is you are limited and will not flow enough air to reach the coolers full potential, but this may be good enough for smaller engines in cooler climates. Good enough is good enough. It is like having a 5-speed transmission and only using may be 3 or 4 of the 5 gears, but some day you may want that extra gear.

The comment of +200F is very good OT in the summer for a O320, but a IO360 (200HP) would burn up with that cooler set up. Engines and OAT make a big difference. Also you really would love to see 190F if possible. Remember what ever you read on your OT gage is 25F hotter in the valve area. Any OT over say 220F-225F (real valve OT not indicated OT) is getting hot. Yes you may be over cooled in the winter but such is the life of aircooled engines. Block the oil cooler. I found I had to disconnect the the duct from the cooler and block the baffle to get OT warm enough in the winter. Also how you fly affects the OT. Some fly at heavy wts., high altitudes or climb for long periods will need more than anothers, who cruises around at 3,000MSL.

Bottom line 3" works and may be the bare min, but 4" will work better and be more efficent. If 3" works 3" works , but I would plan for hot hot temp operations. I also said before more than once buy a Stewart Warner Oil cooler. If you have a O-320 may be the others will be adiquate? Believe me I am a cheap and would buy a less expensive oil cooler if I could, but the others just don't work as well in the real world, 4" duct or not.

(Side Note: Be careful looking at vendor data and how great one cooler is over another. Some require more pressure or more flow or both to achieve the heat rejection a SW can. The venders present the data that shows their cooler rejects more heat, but they are at unrealistic flows and pressures (for a plane installation).

Cheers George

rv6ejguy · #10 08-08-2005, 11:16 PM

A 3 inch duct will flow over 700 SCFM at 180 mph and SL, 4 inch, over 1300, suggesting that a 3 inch duct, properly routed and kept short will easily feed this heat exchanger with the required mass flow. Even with a 24 inch piece of SCAT hose feeding the cooler, you' likely have in excess of 550-600 SCFM available at the cooler. Perhaps of more concern is the delta P across the cooler, it's pretty easy within an RV cowling to have several inches of H2O back pressure at high speeds. This reduces Delta P and mass flow through the cooler. Exits are just as important as inlets.

It's interesting to note that the RV10 has less exit area per cubic inch of engine displacement than other RVs but has a series of louvers added on the bottom of the exit duct to increase exit area. Does anyone know if these were added due to insufficient cooling on the prototype during testing?