Baffling the BME 110
 

For those that have experience on baffling engines in general, take a look at these pics.
Would it be enough ? or should I enlarge the cowl air inlets?
I reinforced the balsa sheeting by applying CF clothing, in addition, there is plenty of specie behind the engine mounting to allow air circulation through the piston fins. The cowl not shown here already fixed with a large opening.
This is a Hangar 9 Edge 33%, BME 110.

RE: Baffling the BME 110
 

The inlets on the cowl are plenty big enough. No issues there at all. The front baffle you have built is a very good start. There are two things that I would do to assure good cooling. One would be to construct and install an upper baffle, or top if you will, that extends over the engine from the forward baffle and angle it downward after clearing the head to get the air flowing the direction I wanted it to go, which is down and out. A big open area behind the baffle and in front of the firewall creates a lot of turbulence. In not being directed anywhere it's entering the front of the baffle and slamming into the firewall, creating a big "roil" in there and not going out as quickly as it should. The other thing I would do is assure that I had a large exit area for the hot air to exit. That area can be reduced some whith the addition of an air dam at the bottom of the cowl, forward of the opening but they can be a pain to do at times.

Dick Hanson posted a picture in this forum a couple of weeks back that well depicted an upper baffle and the way it would direct air. It would not have to be done as well as his but something along similar lines would make the good start you already have into an excellent finished product.

RE: Baffling the BME 110
 

Looks good to me, and better than what I have done on my plane. The only other thing you "might" do would be to slightly block the top to not let the air run over the cylinders, but through.

RE: Baffling the BME 110
 

The baffle for my BME 110 completely surrounds the engine and an additional piece of wood behind the engine conforms with the top of the cowl to ensure all the air going into the cowl is forced between the fins. The following link has a picture of the baffling Chip Hyde uses on his Ultimate.

http://www.scaleaerobatics.com/gallery.aspx

RE: Baffling the BME 110
 

Silversurfer/RTK

Thanks for the reply, I kind of see what you mean, just let me make sure that I got it right, would it be like a sort of "giant ventury "effect by accomodating the baffling plates inside the cowl like this:

RE: Baffling the BME 110
 

I can see where I may have been confusing. Delete your lines at the inlet side. Picture a wall at a downward angle from the top of the engine/cowl downwards toward the rear of the engine. Doesn't need to be full as in an arc, but enough to start the moving and direct the air down and out from the back side of the engine.-----\ Best I could do, with the angle at the lupper eft being against the top rear of the engine and the bottom right of the angle relative to the lower rear of the engine. Figure the bottom of the firewall to be at the same place or close to it. Dashed lines are just above the top of the cylinder heads.

RE: Baffling the BME 110
 

I made a power point drawing of what SS was trying to say, but it will not upload. Sometimes first attempts are failures.

RE: Baffling the BME 110
 

I think you forgot the new lines;)

RE: Baffling the BME 110
 

:D Dang, I hate these damn computers when they refuse to do what I tell them

RE: Baffling the BME 110
 

You did not tell it in a way it understood. The computer is mentally retarded and only understands the one and only way it was taught. Anything else will be rejected because it is too dumb to understand. Remember your Dads' empoyees? Same thing;)

RE: Baffling the BME 110
 

Oh well, I think the RCU server needs to be reseted or perhaps my ISP vpn. The text is OK, some pictures that should be part of the HTML file, are not uploaded, I just got [x]. Same thing if I log onto a different PC.

I will check the RTK PP later or tomorrow.

Anyhow, I believe I know what you guys mean.

RE: Baffling the BME 110
 

To get the best cooling, it should look like this. Both RTK and Silversurfer already pointed that out.
\The air exit is just as, or even more important than the air entry, which needs not be very large. To create a low pressure zone at the air exit point is most important. Air guiding around the fins is important too.

RE: Baffling the BME 110
 

pe reivers

I go it, make sens.
Ops, something else, the rear baffling plates are easy to built and install on split cowl, mine is a single piece cowl, perhaps still doable, however as far as I can picture inserting and removing the single piece cowl might be a little bit tricky. I'll see what I can do in my shop. I may be back with more questions by then.

Thanks amigos !

RE: Baffling the BME 110
 

Pe's picture drawing shows my actual setup .

A couple of other things -- the uppermost line should be in contact with entire top of cowling - use sponge rubber or light bendable 1/64 plywood
Also--don't visualize the airflow as "blowing " thru the cowl -- it is actually just following the easiest path to a low pressure point In the case of a EXTRA or the EDGE -at a lower aft hole.
If you have other holes up front in the cowl -the air will bypass the intended flow
In some cases overly long in cowl exhaust pipe slots will flow more easily than the intend path thru the engine

If I were doing a YAK (and there is no chance of that ) --I would open all the louvers at rear of cowl all around - and make straight parallel paths over top and lower engine--with engine shoved as far forward as possible .
My upcoming Cassut --will simply flow thru the cheek cowls. straight back n out.
I looke at the pics of Chips bipe - strange --that is not how Dave Johnson told me the setup used looked
On the four banger - there was a cross flow dam as well as inlet flow direction plates.

RE: Baffling the BME 110
 

Dick.

I looked at the same pics of Chips plane you did and was quite curious why it had been arranged that way. Perhaps there was something I failed to see, but simply splitting the cylinders as it appeared would not be beneficial.

RE: Baffling the BME 110
 

That was my initial impression also and I didn't understand how it worked. On closer examination this appears to be a very good setup. The baffle surrounding the cylinder heads is attached to the front and sides of the cowl so there are no air leaks. The plate behind the cylinders is conformed to the top of the cowl. All the air entering through the cowl intakes is forced through the fins from top to bottom, none of the air is allowed to exit the cowl without first cooling the engine. An allowance should be made for cool air to enter the carb below the baffle.

Chip used this setup during the last TOC and I copied it for my airplanes. I never had any engine overheat problems during the hot Vegas summers.

RE: Baffling the BME 110
 

The inlet air follows a path down thru the fins - yes - I remember that
As I remember tho -- there was a center vertical piece to divide each side
I was Line Chief at last TOC

RE: Baffling the BME 110
 

No need to. Look at the horizontal white line just behind the spark plug which closes off any by-pass possibility. This makes it easy to mount the baffles fixed to the fuselage without all the cowl fitting. The top between baffle and cowl is now free to provide fresh air for the carb.

RE: Baffling the BME 110
 

How do you guys get all this baffling inside the cowl and have it so the cowl goes on the plane.
I haven't see how to get tangent surfaces to stick and to know how long to make the baffle so that you can get the cowl on.

RE: Baffling the BME 110
 

It's a lot of time, trial and error. That's why making them out of cardboard first is a good way to start. Attaching as much of one or the other baffle to the aircraft structure helps a lot with the cowl on/off sequence. It can all be quite a p.i.t.a., but sitting there looking at things for awhile often comes up with a workable solution. Being perfect is not a requirement, just getting close goes a long way to improving the cooling situation.

RE: Baffling the BME 110
 

just add the pieces that will work and dont add anything that wont.
Have a cold beer - lean back -close yer eyes and think of smoke coming into the front of the cowl - then imagine how you would add a little vacuum at rear of the cowl to pull the smoke thru the engine fins .
Re member-------
The air pressure in the cowl must always be lower than the pressure outside the cowl
If'n not ----- then there is no airflow.

RE: Baffling the BME 110
 

Good Lord, Dick[X(] we agree on something!!:D

RE: Baffling the BME 110
 

Breaking new ground here;)

RE: Baffling the BME 110
 

This was the exact thread that I was looking for... so thanks guys for the great input.. I am in the process of baffling my Edge 540, and searching for some guidance.

RE: Baffling the BME 110
 

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RE: Baffling the BME 110
 

I like the cold beer best, then let all good ideas slip back into oblivion.
I just worked out a Yak with a customer. Some very simple disk attached to the firewall, and some sticky window foam in the cowl did the trick. A cardboard template was cut out in 5 minutes, and it sported both the baffle, and bent back tabs acted as the air guide jacket alongside the fins. Had we made it out of coroplast, we would have needed nothing else.

RE: Baffling the BME 110
 

Round cowl engines are the easiest, especially if the cowl is truly round. Remind me to get back to you on that last (ancient?) pm. I keep getting busy with something or forgetting. CRS syndrome I suppose;)

RE: Baffling the BME 110
 

Baffling seems only ussefull for twin opposite engines, am I wrong?
Maybe my monocylinder GF45i inverted engine could take advantage of this engineering, any pic or comments about it?
Now I´m in gasser it would be great a handy "bibble" on engines cooling tech, any link or web site?

RE: Baffling the BME 110
 

No specific sites that I'm aware of. Some of the engine distributors have a blurb here and there about baffleing. DoD (down on the deck) would be the most likely to having anything specific that would be educational on the subject but I haven't gone looking. I'm certain that someone will be quick to clarify anything that's specifically available at any given site. Just hang tight for a few minutes and it should be forthcoming.

Most singles are left hanging out in the wind, clear of the cowl, to a great extent. The more of the engine outside the cowl the less the benefit. It never hurts to direct the air to the location that needs to be cooled, but with an exposed single the methods needed to create a low pressure area can be extremely awkward. Basically, it amost of the gead on a single is outside the cowl I would not be much concerned about cooling air. If the cylinder is mostly inside the cowl then cooling air entry and exit should be looked into a bit more.

RE: Baffling the BME 110
 

Innitially what I spected to do was follow the rule exit air area should be at least 4 times the fresh air intake area. My Christen Eagle´s cowling is big enough.
I got interested baffling not only by the engine but keep the warm air far from the ignition box and other plastic hardware surrounding the engine ;)
I´ll look a little on the DoD web for a while...

RE: Baffling the BME 110
 

The baffles in Chip Hydes plane follow full scale practice of a high pressure plenum.

RE: Baffling the BME 110
 

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Still learning to upload photo

RE: Baffling the BME 110
 

OK, I think I understand the principle and what is to be accomplished.
I decided to lean my engine for max power.
I now have it set to rip my 26x10 propeller.
It has never done that before.
When I land, the engine is a lot hotter than it has been in the previous 800 flights or so.
I will have to look at installing cardboard to the inlet to see how it looks.
I have relied on the exhaust pipes to create the negative pressure.
It may be wise to put damns in the outlet opening to generate more negative pressure.

This is a dumb question but which of the baffles offer better flow.
1) Top directing air down
2) Bottom directing air to the center of the engine jugs
3) Side to direct the air to the cylinder top.

What is the interaction of the three.
Thanks

RE: Baffling the BME 110
 

They way I would do it is similar to the picture Dick Hansen posted somewhere here recently.
Bottom to jugs, side to caps and top to make it flow down the backside of the cylinders and out.
Use lip on bottom of cowl to create a low pressure zone for better draw.

RE: Baffling the BME 110
 

On the BME the caps dissipate a lot of heat so they must be in the airflow. This is straight from Keith.

Making a pressure plenum gives the best airflow with the least resistance. I have several links in my other computer to the why and how of engine baffles including model and full scale but it crashed and I haven't had time to recover the files.

RE: Baffling the BME 110
 

skypilot--If you ever recover those files post the links, I would like to read them and I imagine everyone else too.

RE: Baffling the BME 110
 

I was going to say the same thing.
I see guys with baffles in there planes but I have tried to glue balsa in a cowl and it didn't seam to work to well. Could not get it to stay long enough to glass it.

RE: Baffling the BME 110
 

0-200 engines as installed in C-150 are baffled similar to the Chip Hyde example but in addition have sheet aluminum wrapped around and spring clipped to the cylinder. These have an ~2 inch wide seam, on the centerline of the cylinder, for air inlet and exit. The purpose of this is to force air through the cooling fins for a much longer cooling path than just the !QUOT!edge!QUOT! effect next to the baffle. this results in a more even cooling around the circumference of the cylinder.

When I first this I was appalled, there was no way there was enough airflow around the cylinders to handle the cooling. Rational thought then took hold and I realized the guys that designed the baffling knew what they were doing.

More even cooling around the total circumference would help to promote ring seal at running temperature probably not a huge consideration.

I do not advocate doing this to our aircraft unless a thorough test setup is contemplated with proper temperature monitoring.

RE: Baffling the BME 110
 

You have to contain the inlet air - the flow intensity will depend on outlet low pressure setup.
the setup I used here - is held to motor box with four #2 skt head screws -comes off in a minute -but has never unintentionally loosened
If you want to glue stuff into cowl - use clear silicone rubber on cleaned glass surface - make little angles in any plates at their bases to provide good support. epoxy or goo can cause dimpling which will show on outside of cowl.

RE: Baffling the BME 110
 

Hi Dick,

That is very much how I did my OS 160FX with an additional horizontal shelf glued to the cowl to direct the air to the center of the cylinder and the port side was blocked and partitioned off. After reading a few articles I found that it is better to have a larger Plenum above the cylinders. I suppose it really doesn't matter that much in our engines and your baffles are better than most people would ever make.


I found one good link to full scale, still can't find the one where the guy was machining model engine heads.
http://www.avweb.com/news/savvyaviator/188945-1.html

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