skywagon8a
MEMBER
SE Mass MA6
Another thing. The pivot on the valve appears to be in the wrong relationship to the overboard hole. Is there another photo which shows a bigger picture?
PA-12 cabin heater box and other firewall forward jobs :)
- Thread starter Philly5G
- Start date
According to the Parts catalogue the lower hole/tube on the heater box should actually connect to a hole/connector on the upper part of the shroud and support the heater box. Also, when the cabin heat knob is pulled out (for on) the flap in the heater box is pulled up allowing the airflow from the lower hole/tube into the cabin, this all points to the lower hole/tube being the hot air and the other hole/tube being unwarmed fresh air. My understanding is that ram air is piped into the heat shroud from one of the vent holes on the lower cowl and it's this flow that pressurises the warm air into the cabin.
In this photo the heater box is actually connected to the heat shroud by the smaller scat hose, so although it's not the parts catalogue spec, it's still supplying the hot air? So this seems to be the correct config?
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? It's in the same place as on my heater box, see the pic above where it's just resting on the heat shroud where the Parts Catalogue says it should be. In both photo cases the heater control cable comes out on the port side of the heater box and this aligns with the valve arm.
Steve, where does the Scat hose from the front right baffle connect to? According to the Parts Catalogue, this hose should connect to the heat shroud to provide the pressure for the Cabin Heat. My PA-12 doesn't have an inlet on the front baffles, so to get some pressure for the cabin heater I'd need to use one of the lower cowling inlets OR modify the baffles. But also, my aircraft has the carb heat air ram air hose and connectors on the left rear baffle, rather than the right!! :roll:
Starting work on redoing the baffles today by wrestling off the old felt and making a cardboard template to fill the gaping gaps on the back baffle 
Also noticed there are baffles all the way from front to back horizontally underneath the cylinders on both sides, which I'm deducing are non standard as the pics in this link seem to prove https://www.knots2u.net/piper-pa-18-150-complete-engine-baffle-set/, as are the cowl hole bottom vents which join up with the under cylinder baffles....... Has anybody seen a similar arrangement? :roll: I already knew I'd be making new front baffles as I need to add the forward air intake for the cabin heater ram air feed, but the underneath baffles are a new discovery!!!
Also noticed there are baffles all the way from front to back horizontally underneath the cylinders on both sides, which I'm deducing are non standard as the pics in this link seem to prove https://www.knots2u.net/piper-pa-18-150-complete-engine-baffle-set/, as are the cowl hole bottom vents which join up with the under cylinder baffles....... Has anybody seen a similar arrangement? :roll: I already knew I'd be making new front baffles as I need to add the forward air intake for the cabin heater ram air feed, but the underneath baffles are a new discovery!!!
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mike mcs repair
Registered User
chugiak AK
can't say i seen baffles that far under cylinders... kinda useless looking..
Yes, it looks like the baffle layout has been modified in an attempt to channel the air along the bottom of the cylinders, as I've just realised the inter cylinder baffles are missing :roll:
Steve Pierce
BENEFACTOR
Graham, TX
Common to the O-235 installation on the PA12, PA16 and PA22-108.
WOW!!!! Thanks Steve!! So it IS a standard layout!!!! WOW and thanks again!! The aircraft was operating in professional aerial photography in Portugal before my ownership, which is a VERY hot climate and I've certainly never noticed anything untoward in temps when operating in UK, CHT stabilising at 180, so the cooling is obviously working ok in that config, would you suggest staying with this config? My real question in addition is that I need to add the intake for the cabin heater ram air and was considering making a "standard" ramped cowl/front baffle with the scat intake in that, but given this news what would you recommend?
Steve Pierce
BENEFACTOR
Graham, TX
The PA12 I took pictures of went home on Saturday. I will have to see if I have any more pictures of the install. One hose goes to an intake scoop on the bottom cowl. The other is to the heat muff on the Sutton exhaust.
I don't think the original baffles are the best design but the O-235 is a low compression engine that normally doesn't even have an oil cooler. Operated one well past 2600 hours at which it wore out the rings and started using oil. Still had compressions in the 70s and inside of the engine looked great.
I don't think the original baffles are the best design but the O-235 is a low compression engine that normally doesn't even have an oil cooler. Operated one well past 2600 hours at which it wore out the rings and started using oil. Still had compressions in the 70s and inside of the engine looked great.
Thanks Steve, the connections to the heater box itself are indeed the fresh air from the cowl and the heater one from the heat shroud, it's the pressurisation one from the front cowl baffle to the "inlet" hole on the heater shroud on the cabin heater side that I'm trying to accomodate. In your (excellent) photos I can see the front baffle air inlet in picture 4 and the scat hose snaking back under the engine, presumably to the heat shroud and it's getting this intake on my currently flat front baffles that I'm trying to figure. Maybe i should add a duct or something to the flat plate?
flybynite
FOUNDER
Eagan, Minnesota
Late to the party, as usual.
Original O-235 baffles, exhaust and muffler/heat box pics
On picture 1, the long scat tube goes to the muffler, left intake on the top for the carb heat. The scat tube shown attached to the muffler pic goes to the airbox for heated carb air.
On picture 3, the large scat tube goes to the intake on the heat box for fresh cabin air, the small scat tube is blast air for the generator.
There is another air intake that attaches to the heat muff just above the exhaust tube in the last picture.
Wayne
Original O-235 baffles, exhaust and muffler/heat box pics
On picture 1, the long scat tube goes to the muffler, left intake on the top for the carb heat. The scat tube shown attached to the muffler pic goes to the airbox for heated carb air.
On picture 3, the large scat tube goes to the intake on the heat box for fresh cabin air, the small scat tube is blast air for the generator.
There is another air intake that attaches to the heat muff just above the exhaust tube in the last picture.
Wayne
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Steve Pierce
BENEFACTOR
Graham, TX
Lycoming install drawing.
I’ve pretty much finished the fabrication of a new centre panel for the back baffle and can 100% agree with an earlier baffle post which mentioned how time consuming this is [emoji849]
Steve, in your photos there looks to be some mastic sealant or something between the bottom of the rear baffle and the engine, is this normal practice and what actually is the sealant used?
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Steve Pierce
BENEFACTOR
Graham, TX
I use RTV to seal all the gaps that air can escape. I want all the air going through the cooling fins.
Thanks Steve, is there a particular brand you use? I've done some initial research and there's a lot to choose from. Does the RTV weld itself on to the engine and bulkheads etc, or can it be peeled off? Cheers P
Steve Pierce
BENEFACTOR
Graham, TX
Thanks Steve, they look like single tube products and used with those heavy duty type metal plunger things?
Steve Pierce
BENEFACTOR
Graham, TX
Yes but it comes in squeeze tubes as well.
Thought I was doing really well today, tracked down a set of used baffles, intercylinder and outer baffles and painted and installed the inter cylinder ones and felt I was pretty much there
But then had a chat with a couple of Cub drivers in the club house and they said they also had a v shaped baffle on the upper cylinder fins too?!!! I don’t see this in the parts catalogue? Do other people use this?!!
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But then had a chat with a couple of Cub drivers in the club house and they said they also had a v shaped baffle on the upper cylinder fins too?!!! I don’t see this in the parts catalogue? Do other people use this?!!
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skywagon8a
MEMBER
SE Mass MA6
These pictures look correct.Thought I was doing really well today, tracked down a set of used baffles, intercylinder and outer baffles and painted and installed the inter cylinder ones and felt I was pretty much there
View attachment 47173
View attachment 47174
But then had a chat with a couple of Cub drivers in the club house and they said they also had a v shaped baffle on the upper cylinder fins too?!!! I don’t see this in the parts catalogue? Do other people use this?!!
THANK YOU skywagon8a!!! This is what the O235 parts catalogue shows, hence thinking I was there!! This is becoming a real struggle to be honest, I just wanted to tidy up the baffles when adding the new engine, but it's become a LOT more than that!! My original plan was just to replace the felt with rubber and repaint them, I now find myself becoming an aerodynamicist specialising in contained airflow!!
This sketch may help explain where I am:
The top sketch shows the baffles as they were, with the back and side baffles pretty easy and self explanatory, I've remade the top centre section of the rear baffle as it was full of holes and not stopping the airflow in any way. The front "baffle" was just a flat piece of metal from the bottom of the cowl opening to just past the mid point of the cylinders.
I've remade the front baffle as in the 2nd sketch to redirect the airflow to the middle of cylinders 1 and 2 and up into the plenum chamber and also fitted the lycoming intercylinder baffles as per parts catalog and photos above.
The 3rd sketch is a combination of my chat with the other Cub guys I met yesterday and also after reading the EAA guide on "how to baffle your Lycoming" and it shows a curved baffle in front of cylinders 1&2 which is linked to the inter cylinder baffle and the rear baffle and although it doesn't show this, the Cub Drivers said they had an additional inter cylinder baffle under the cylinder heads. I've checked the PA-12 parts catalogue and I see that Univair part #U10923-000 looks like the part?
I can see why the front curved baffle might/would be needed, as otherwise there's no cooling air to the bottom of cylinders 1&2 as the ramp cowl baffle is throwing the air up into the plenum and i don't see how this is being directed under the front cylinders, other than the intercylinder baffles?? But this isn't shown in any of the baffles kits, Lycoming or Piper parts catalogues?!!
Any definitive steers on this will be very gratefully received 8)
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skywagon8a
MEMBER
SE Mass MA6
Phil, You are replacing an original model engine with another original model engine. Remember when Piper originally certified this airplane/engine combination they did cooling flight tests. The engine would have had thermocouples on all cylinders and likely in more than one location on each cylinder. As well as other locations on the engine. When Piper finalized the baffle design, it met the cooling parameters and then the CAA (now FAA) certified the PA-12. Unless you or someone here can document a deficiency to Piper's baffle design, I would just repair or duplicate the original. Not following the original would place you in the position of having to run cooling tests to verify that you caused no harm by making the alterations.
A lot of the comments here come from people who changed their engines from the original to something else.
A lot of the comments here come from people who changed their engines from the original to something else.
Thanks sw8a. My buddy also has a PA-12 with an O235-C1 and he has the ramped cowl baffle and also the outer cylinder intercylinder baffle.
Mine has/had the straight through baffle as I described, both of us have adequate cooling.
I need the ramp baffle so I can duct off fresh air so I can fit the cabin heater (which came with my aircraft but uninstalled) if I didn’t,
I’d just refit my original front baffles.
Can you, or anyone else please tell me if the flat plate ramp baffle, the inter cylinder baffles and the back and side baffles are all that’s needed to make the ramp baffles layout work?
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skywagon8a
MEMBER
SE Mass MA6
I don't have access to a stock PA-12, so can't help you further.
You really need to put a 4 cylinder EGT/CHT in to know what is going on. Each plane/engine is different. I spent a few years fine tuning the baffling on my cub and it has really paid off in lowered CHT'S. Without proper instrumentation you don't know what you don't know. When you do get it done you will see a lot of people put RTV on the front baffle by the cylinder. No not let that RTV between the fins.
DENNY
DENNY
Interestingly the Univair PA-12 parts catalogue shows the ramp flat blade front baffles.
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Believe it or not I spent time this morning researching 4 channel CHT/EGTs
The aircraft came with a CHT gauge that wasn’t reading, I got a replacement sender and installed it on #4 and it always climbed to and remained at 180 C, which I was happy with and now I’m in a world of uncertainty and worry [emoji6]
Which front baffles type do you have? and do you have the wrap around baffle on #1 and #2?
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My front baffles are flat to the barrel of the cylinder with ramps at the heads #1 is about 1/2 inch taller at head than #2. At 2400 RPM level flight 2,3,4 are within 10 degrees of each other with # 1 being 10-15 degrees cooler. In full throttle climb #2 and #1 CHT's climb while sometimes #3 and 4 will even drop. You really need to see all 4 to know what is going on. A single EGT/CHT is kind of like tits on a boar hog, they got them but they don't do much good. I had the stock front baffle and use aluminized tape on the front cylinders over a few years adjusting as need for front/rear/side to side temp control. I fly from -30 to +90 degrees so it took a few years to figure out right hight with tape then I made my ramps a bit shorter. Most don't go to all that effort simply use stock baffle and add tape to head as needed. I will see if I can find a pic to post.
DENNY
DENNY
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