The International Cessna^® 170 Association

Anybody had experience with a heat sink you can put on the oil filter? Available at Aircraft Spruce for about $40. They say it reduces oil temp by 20%.

voorheesh wrote:Anybody had experience with a heat sink you can put on the oil filter? Available at Aircraft Spruce for about $40. They say it reduces oil temp by 20%.

http://cessna170.org/phpBB2/viewtopic.p ... oil+filter

Thanks for posting that link, Miles. Most everything about the subject was said there, but I'd like to remind folks about something, as regards the idea of a "heat sink" on an oil filter.
Heat sinks work both ways...they'll also absorb heat.
In the typical 170 installation, the oil filter is in the low-pressure area of the cowl...downwind from: hot cylinders, hot exhaust pipes. In my own fertile mind... (Daffynition: Fertile: full of sh**.) .... I can easily imagine the heat sink absorbing all that engine/exhaust heat and imparting it to the oilfilter.
It'd be a good project to temporarily tape a digital temp probe in the area and see what inflight temps are there before attempting to see if a heat sink will work. IMHO

Maybe that's why Jasco wants cooling air for their alternators ducted in from a cooler area rather than sucking in all that hot air with a fan...

Miles

I have been following some of the posts regarding cooling tubes/hoses and it is my understanding that if the alternator has a cooling fan that it should not be necessary to have a cooling tube on the alternator. My "C" model has a section of SCAT hose from the back baffel running down to the top of the alternator--obviously for cooling. Maybe its not needed and I should direct that cooling air to some other place. What do you think? What else would benefit more?

Frank,

Is that cooling hose connected to the alternator, or does it just terminate in the vicinity? If the air in the accessory compartment is as hot as George theorizes, then even a hose from the back baffle blowing where the fan can pick up the air would be better than nothing. The air picked up at the back of the baffle hasn't yet done any engine cooling and is very near ambient temperature as evidenced by the fact that it is one source of cockpit ventilation.

Miles

Someone, maybe whomever did the alternator conversion, put a clamp attached to the alternator (top side) that accepts a 2" hose from the back baffel. I don't know anything else back there that would benefit from that air so I will most likely leave it focused on the alternator. One always has to wonder if this was a part of the stc or just someone's idea of needed to be done. There is nothing in the logs to indicate this other than the mention of the conversion. I forget the actual name of the conversion, but its the Ford alternator.

170C wrote:Someone, maybe whomever did the alternator conversion, put a clamp attached to the alternator (top side) that accepts a 2" hose from the back baffel. I don't know anything else back there that would benefit from that air so I will most likely leave it focused on the alternator. One always has to wonder if this was a part of the stc or just someone's idea of needed to be done. There is nothing in the logs to indicate this other than the mention of the conversion. I forget the actual name of the conversion, but its the Ford alternator.

I believe the Jasco alternator STC requires a cooling tube. The easiest route is a fitting attached to the rear baffling and a hose. I would attempt to describe the Rube Goldberg affair that the person who installed the alternator on my plane used, but I don't think I can find the words.
I installed a Ford alternator using the Barnstormers STC on another plane (not a 170) and it also required a cooling tube.

I'm still working on getting a field approval for the Ford 60 amp. alternator as the data on the 337 form for this conversion filed in 1985 was never approved.

The Cessna Service Kit, SK172-22M, that I'm using as a guide shows ducting from the right rear baffling going to the rear of the alternator. A cooler alternative is found in the '63-'74 C-172 IPC. I was able to locate an NOS shroud and so was planning on adding this to the field approval. But here's the problem. The alternator turns counter-clockwise thus pulling air in from the fan which is located toward the front of the alternator and blows that air toward the rear where it exits vent holes. The blast tube directs air in the opposite direction thereby -- it seems to me -- reducing the amount of airflow over the stator, rectifier, and rotor. In other words, the blast tube and the fan seem to be working against each other.

One step forward, two steps backward (insert pulling hair out emoji). Suggestions?

Gary,
Do you have a theory of how it worked in your picture labeled "Cooling Shroud, '63-'74 C-172 IPC"? Perhaps there is a left and a right hand fan.

John,
I don't know how -- or if -- this shroud worked on C-172s. I imagine the airflow through the alternator might change direction depending on phase of flight. Stopped on the ground the fan might produce more pressure than the duct. At idle in descent the higher relative pressure in the duct might "overpower" the fan.

Seems to me that it would be better to have the fan and the vent working together rather than against each other. Finding a fan that pulls the air from the rear of the alternator rather pushing it there would be great but I haven't found such a fan assembly. Another alternative would be to have a different shroud that would fit over the fan area of the alternator. Similar to these used on oil filters. Doubt there is room for something like that and an oil filter adapter. Alternatively, one could change the source of the shroud duct from the high pressure area over the engine to a low pressure area. It would be interesting to use a digital manometer to find the area of lowest pressure. I assume it would be right at the lower cowl lip. Or somehow tap into the extended exhaust tailpipes for a venturi effect. ... too much work. If the duct was routed to a low pressure area the alternator fan would be pulling in warmer air from the accessory case area.

At this point, I'll use the KISS principle and go without any ducting as Blueldr writes here. It can always be added later if needed. Do you have any ducting to the alternator on your IO-360?

Gary,
No ducting to the alternator on my engine and it has performed well for over 900 hours.

In your picture "SK172-22M" one would think the duct mounted near the back of the alternator is a mistake and should be locate towards the front at the fan end.

John,
Yes, I agree, it would make more sense to aim the duct at the fan area. Like this casting in a Continental (or Prestolite) 24V alternator.

n2582d wrote: ↑Sat Jul 13, 2024 4:36 am John,
Yes, I agree, it would make more sense to aim the duct at the fan area. Like this casting in a Continental (or Prestolite) 24V alternator.Cast Duct on Alternator.png

Most Cirrus use the alternator casting style Gary pictured. They are mounted on the right front of the case halves, gear driven off the crank. That duct port is pointed/inserted through the front baffling to the low pressure area under the baffling. Air is sucked in the fan through the venting and out the port helped by the lower pressure area. There is no ducting attached to any of them.

Gary, I have the Cessna Alternator Charing Systems Service/Parrts Manual dated 1 October 1965, Revised 15 July 1968…. and while most of the manual is devoted to belt-driven alternators…. the final Figure 68 depicts the gear-driven alternator…. and that fan does indeed “point” the direction your example does. (I was suspicious that an automotive fan may have been substituted….OR…that an alternator for a left-hand-rotation Engine …such as found on some counter-rotating multi-engine aircraft…. may be what you have obtained.

But Here is a pic of that Fig 68 which also calls for Fan PN: C6FF-10A310-B.
If the fan/rotation we are discussing is correct…it would seem that at some point in every flight the air in the alternator would STAGNATE as cowling pressure equated/opposed the fan.

It MAY also be that the illustration in the SK is in error….and the Blast Tube should be placed FORWARD of the Strap rather than Aft as-depicted. (Cessna has on more than One-occasion been known to improperly illustrate parts-assemblies.)