Cruisair/Franklin baffling

Dan Cullman

Dan Cullman

New member
OK. Here's my new topic to chew on.........the cooling baffling on the Franklin installation in the 14-13 series Bellanca. I think the various airframe manufacturers were still trying to figure out how to cool the horizontally opposed aircraft engine, as late as 1960. I have seen so many early baffling setups by most of the manufacturers, including Bellanca, that were poorly designed and inefficient. I have to hand it to the 'homebuilt' industry to show the rest of us how to cool an aircooled engine with a modest amount of air. OK, it's out. What are your ideas and thoughts? I'll expound more, later. Dan
 
Dan,
I looked at serial number 200 a few years back to buy, it had up draft cooling I believe that is where they got the idea to use that on the early 14-19's it had a really pretty nose bowl with no eyebrows. Last I knew any thing of it Randy Smith of Lake Dallas owned the plane. I am not sure how well the cowling and baffleing cooled the engine I do know it didn't carry through to the 14-19-2....Greg
 
Greg brought up a topic that I wasn't including in this posting because the Cruisair didn't use updraft cooling. However, since the 14-19 used it, I feel it is a worthy topic. Quite a few post-war aircraft employed updraft cooling. Swift, Navion, Funk and the original Bellanca Cruisemaster come to mind. Later aircraft like the Piper Navajo and AeroCommander followed. Most installations led to some interesting cowlings, but suffered in efficiency. Cooling air entered at the bottom of the cowl, went upward through the cylinder fins and then reversed direction to exit out the bottom of the cowling. A lot of wasted energy, changing direction. The only application that seemed right to me were the latest of the recip AeroCommanders that had the cooling air exit the top of the nacelle. Even the cowl flaps were up top. OK, we are open for more discussion on the original post or updraft cooling-----------your choice. Dan
 
I have to make a correction. The 14-19 didn't use updraft cooling. It might as well have. The cooling air entered the lower cowl 'smile,' met a flat plate and was forced upward and over the top of the cylinders to become downdraft cooling. Cool cowling, but not efficient. Dan
 
Dan, since the Franklin engines have been STCd into Swifts,Cessna,s Piper Apaches, and are in the original TCs, for Maul and I believe the Socata Rally, is there any information floating around about better cooling in one of those? I do recall Mike Grimes saying that his 220 Franklin powered Cruisair ran nice and cool,but he also said it had a newer and better oil cooler.On the flip side of the coin Kent Tarver said the 180 Franklin powered Cruisair that he owned years ago ran hotter than a pistol. I dont know if any 180 (Debs Aero STC) powered Cruisairs are still in flying status but I believe you used to fly one. Was there any cooling problems with yours? Too bad we couldnt donate a Cruisair to the LoPresti, group,they would get the speeds up.___ Grant.
 
I flew a Franklin 180 hp/ contant speed prop modified Stinson on floats as a missionary pilot in Peru, as well as a Frank 220 hp Maule on wheels. In the jungle heat our main problem was oil cooling......resulting in the oil pressure falling into the yellow arc......resulting in pilot stress. If you are going to do any big Franklin mods hunt down the biggest cooler you can find & figure out how to get lots of air through it. Planebones
 
I have some background here. My Cruisair has Debs STC, S/N 011. I think only a couple more were sold after mine. Originally, I used the Heat Exchangers oil cooler that came with the 150. The oil ran very hot. I called Franklin - yes they were still in business in Syracuse. I still have the letter I got back from them. They doubted that the old cooler was adequate and said to use nothing less than 50 SAE oil. They also mentioned that the high limit for oil temperature was 235F, out of the oil cooler. At this time, my Dad had a 220 Franklin Maule, which I got to fly on occasion. The Maule didn't seem to have the same temp problems as my Bellanca. So, I replaced the whole air induction system between the carb and the nose bowl to replicate what the Maule had - paying close attention to sealing air leaks. I also replaced the brass cooler with an aluminum Harrison the same size as on the Maule. I got a field approval for the mod. This helped quite a bit on the temperature. Also, you must realize that the last digit on those old 3 in 1 gauges' oil temp is 100C, which is far below the oil limit. The indicating needle will go far beyond that 100C marking. I can see the needle pointing to the 5psi mark on the fuel pressure gauge on a very hot day. I equate this to 110-112C - about as hot as I can take. We haven't addressed cylinder temperatures, yet. In the next day or so, I'll mention what I did to maintain the 'cool.'
 
Yes indeed, Dan, engine cooling engineering was mighty pitiful on my 14-19 though it was no worse I suppose compared to its contemporaries such as the updraft cooling on the Navion and the reverse airflow problems on early Bonanzas. I can understand why they'd think that the key point was the size of the intake area...didn't that work quite well for the predecessors of the horizontally opposed engines? The notion that the point of the exercise was to achieve leak free air pressure within the cowl, and a sizable, smooth exit area for the air came later I believe. Not sure it was the homebuilders who came up with it though. Didn't the -2 use the latter day method? To my understanding it worked so well in fact that they dumped the cowl flap, even though there is a place marked out on the -2 panel for a cowl flap control.

To keep my 14-19's bright, friendly smile, I relied on people far wiser than I, such as Russell and his mechanic friend Rob Regan. It was Rob who told me about the reverse airflow potential of the standard 14-19 cowl flap. It's just a piece of metal. Rob put "fences" around it so that it made a seal with the cowl when deployed. Russell went crazy on the baffling, making sure there was something akin to a sealed area around the cylinders. It works pretty well, though it probably runs just a bit hotter than many people would prefer. It stays below 400 degrees though which is a huge improvement.

Nonetheless I lean by CHT rather that EGT as the former will approach 400 degrees just prior to the latter reaching its peak.

Jonathan
 
JB. brought up a couple ideas about cowl flaps on the -2 Cruisemaster. The first few -2s had all metal doors and cowling-including the nose bowl. There was a provision for the cowlflap in the lower cowl and the actuating mechanism at the instrument panel. Did the later airplanes have this? I don't think so. Tell me. I think expediency dictated the fixed cowl during certification trials with the new engine. I really think a cleaner cowl that required a cowlflap would help the airplane. Dan
 
OK. Back to the original topic. Franklin baffling. GMB employed state of the art cooling technology to the 14-13 series. This was poor to middling at best. There were too many air leaks in the system; especially in the back baffle. The stock baffle was spaced about 3/8" in back of the rear cylinders. This needs to touch the rear cylinder fins. The front baffling needs to completely seal the engine from the nosebowl. I found that intercylinder baffles for both the heads and barrels, that were never installed in any Bellanca installation were a great help. One or more participants have had critical remarks about the 'eyebrows' on the 14-12/14-13 series. This one item I will credit to the genius of GMB. It works and it is simple. Additional air is admitted at low airspeed/high angles of attack-less is admitted at low angles of attack and higher airspeed. I think this is smarter than Stinson's custom grill system. The eyebrows are part of what makes a Bellanca 'a Bellanca.' What do you think? My next topic has to do with the AC/AN plumbing issue that was brought to the surface in that last issue of 'BC Contact.' Do some homework and do your part. If you deal with a 1930-1950 airplane, you could be involved. Dan
 
My Cruisair has a cowl flap. I have even had to use it...maybe three or four times in the last 18 yrs, only because my CHT on #3 and #4 were getting up to 350 deg F on hot N. Cal. days during climb out. I know that I have a large margin beyond 350, but since I have the flap, why burden the engine? Larry
 
My 14-19-2 sn 4046 has no provisions for cowl flaps. It was completed in December 1957. Registration shows it as the first 1958 airplane.
 
Ditto Dan, I have no provision for cowl flap on my -2 s/n 4090. There is a guy on the field here with a Navion B geared 435 that the shop who did the last annual will not sign off the engine, due to excessive heat, red line temps. He bugs me once in a while but I'm old enough to know when to say NO. I find this subject of yours very very interesting. Thanks for the info. Lynn the crate :D
 
Lynn, I'd have to look at your friend's Navion to offer anything. As I said earlier, updraft cooling is an uphill battle. The Navion guys have always had a good club. Maybe a change in cowling and or an IO 470/520 conversion is in order. Larry, you are being very conservative. The limit on Franklin cylinders is 390F. I don't bother with anything 'til I see 375 or380. Dan
 
Wow Dan, I've never been called conservative before...don't do that or JB won't talk to me anymore. I agree that I am taking it easy on the engine. According to the TCDS for the engine, the max permissible temp for Well Type Head Thermocouple is 445 deg F. Where did you find the 390 number? lhl
 
Dan, what are intercylinder baffles ? I dont see anything like that on my engine or on any of my projects? I also dont see them in my overhaul manual. Do they help in cooling and where might they be available?-----Grant.
 
The 390F figure comes right out of my 6A-335 operator/overhaul manual. Maybe that's one reason this engine has a 2000 hr TBO. I'd abide by this figure on the 150/165, as well - doable with a baffling O/H. Remember, you pull the guides and liner out at 600F. I think you could stand a little higher temp on the pre-war steel barrels with shrunk on heads. Dan
 
Grant, check out any Lycoming built in the last 50 years, and under the cylinder pairs you'll find what I'm talking about. I've made intercylinder baffles for every horizontally opposed engine I operate. My C85 in the 120, all the Franklins, too. As I said, as far as I know they were never supplied in the 6A or 6A4 series. You get to locally fabricate. Dan
 
To show how important cooling airflow cahracterstisc can be, there is an old study that involved towing a 14-13-2 to altitude and glide testing it under many conditions. As I remember, the single biggest boost to flight efficency was to plug the cooling intakes! The conclusion was that the cooling air was so mishandled inside that the slow-moving air at the exit acted like a barn door. I did some brief research, and it looks to me that the new homebuilts and kits worry a lot about HOW the in-flow is slowed down before going thru the cooling fins, and how it is re-accelerated before exiting the cowl.
 
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