Magneto cooling

Dan Cullman

Dan Cullman

New member
Another thing of interest that I've had on my mind is magneto cooling. Magnetos, for the most part, sit behind the baffling on most airplanes. Those of us with the O-470 in a Cruisemaster know this is not always true. Somewhere in my archives---------Bendix stuff, says that '...the maximum operating temperature of the magneto is 200F.' Couldn't find it today, but I will. Anyway, It doesn't take much imagination to see that this limitation could be exceeded in many ways. I first came across this with Eisemann mags in my 14-13 back in 1970. Think about it for a while and I'll expound a bit later. Dan
 
OK, Not much thought on this topic. Many manufacturers run blast tubes from the back baffling to affected areas. Generally, 3/4-1" aluminum tubing is used. My favorite installation is in the Cessna 170 series. A blast tube is used to blow air on the oil temperature housing. Hmmmmmmm. Anyway, I use a blast tube to direct cooling air on the magnetos in my horizontally opposed installations to keep temperatures within reason.
 
I thought all planes with rear mount mags had blast cooling. When I rework the baffaling on my cruiseair with the lyc 180 I also put a tube on the fuel pump. Can't hurt. :lol: :lol:
 
Dan, The only blast tube I recall seeing on Franklin powered Cruisairs is to the generator. Do you have any pic's of one going to the mags? Thanks! Larry
 
I saved a bunch of Stinson baffeling that was in pretty bad shape just to get the blast tubes off of. I don't know what I did with them now. I will look for them is anyone is interested. I agree with Dan any help cooling accessories will surely make them last longer....Greg
 
Very few manufacturers provided for magneto cooling. Bellanca did not. I have added blast tubes to most of my aircraft. These can be as simple as the 90 degree corners cut from old lawnchairs or purpose bent tubing from your shop-usually 3/4 or 1inch size. The easiest installation is to have a tightly fitting grommet in the upper end of the blast tube installed in the back baffling. Larry....my digital camera is TU. I'll send a snapshot if you want. NN your address. Randy, the blast tube to the fuel pump is a good idea. I think Piper did that on some of their later models.
 
I would guess that the blast tubes could originate in the aft baffling, but how are they "attached" to the mags? My address is 2135 McMillan st. Eugene, OR 97405. Thanks Dan!
 
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