Oil Cooling Blast Tube

[6930]

I was looking at a friends 1946 140 and he has a blast tube which directs cooling air from the rear baffle plate to the oil screen housing. Checking the parts manual, it shows item 38-64, P/N 0450240 as applicable on 1948 140's, S/N 14365 and up and as item 37-26, P/N 0450240 for 1946 models.

Mine is a 1947 and instead of the blast tube to the oil screen housing it has air directed by a scat tube to the generator.

Is the blast tube something I should consider adding to my airplane? Perhaps in addition to (or in lieu of?) the generator scat tube? Hot summer days my oil temp gets up to around 215 Deg F.

Anybody know why it was included in the '46 and some '48 + models and up but not the '47's? Seems very strange that there should be this inconsistency. Or, maybe I am missing something?

Thanks in advance.

[6597]

For starters, check out Neal's article here...

viewtopic.php?f=10&t=99

[6930]

Thanks for the input. I’ll check it out.

[6643]

I don't know why the confusion in the parts catalog. I can't think of any reason all engines should not be equipped, unless there's confusion about having the Continental oil cooler installed.

Regardless, if you're seeing 215 degree oil temps then you should put one on. And yes, it reduces the indicated temperature of he oil by cooling the oil... All of the oil passes through the screen and the temperature probe is in the middle, so, if it lowers the gauge reading it's lowering the oil temperature, too.

The similar setup on the generator should be installed on all generators. Generators do not have an integral cooling fan like alternators do, so, without the tube there is no air circulation through the generator. Figure 14 in the C-series overhaul manual (Installation in the Aircraft) specifies "Minimum air pressure differential across generator - 1-1/2 inches of water."

[6930]

Hello John,

Thanks, once again, for the excellent information.

Before summer, I am going to add a scat tube for cooling the oil screen housing. To do this, I will have to add another hole and a flange for the second scat tube in the baffle wall. However, I am a bit concerned about having holes for both the air for the generator and air for the screen housing right behind number 2 cylinder. It seems that two holes might bypass too much air needed for cooling cylinder 2.

Instead, I am thinking of switching the generator tube to the left side behind cylinder 1 and take the oil cooling air off the right side behind cylinder 2 through the existing port.

What do you think of that?

Edit - I realized that I transposed the cylinder numbers in my post…brain fart.

Thanks!

[6597]

This is my set up. Behind cylinder #2 I have 1" scat going to previously the generator but now the rear bearings of the alternator. Behind #1 is the bent tubing going to the oil screen housing.

DSCN4209.JPG (119.42 KiB) Viewed 3749 times

[6930]

Excellent, thanks David! That's exactly what I am thinking of doing.

[6643]

Put the tube for the oil screen where it belongs (right side) and the one for the generator on the other side.

[6930]

Got it. Thanks again!

[lampak25]

Not wanting hi-jack this topic but it’s related to oil temps…mine are quite cold. Today, at -5F surface temp, oil temp was 115F at startup, 95 at take off and after 500 agl climb temp was at 112F. These temps where produced while both vents under the prop are taped over and additional tape on the bottom exit of the cowl by the breather ( only 6” inboard).

My big concern comes from descent to land. On final temps fall below 90F and this was after a 2 hour cruise. I understand raising oil temps in sub zero temps on a C85 is tough but when is oil temp too low?

Would covering up the oil sensor/screen blast tube be the wrong way to have a high oil temp reading.

My oil temp reading is coming from a CGR-30P