Big Wheels Keep on Turnin'

[flyguy]

Re: Big Wheels Keep on Turnin'

Left front, hmmmm, I have to check my front cylinder on that side, I figured that it would be the right front on mine after checking the propwash pattern. Interesting. Time for more measurement. Agree with you on the angle thing on the exit, but it probably isn't just one thing. As said, on mine, more measurement required.
DC

[Hank Jarrett]

Re: Big Wheels Keep on Turnin'

I'm watching the thread but so far you guys are suggesting all the things I would. I'm going to get some or the temperature crayons and do some checking when I get my plane flying again. We never noticed problems before, but then again, we weren't looking. Oil temps looked OK, but that is all we had.
Wish I could suggest something more. I'll keep thinking.
Hank

[VictorBravo]

Re: Big Wheels Keep on Turnin'

Thanks Hank, I'm embarrassed to say that I need all the brains on this as I can get. Everything I've tried for the last YEAR has been wrong or ineffective. I have a manometer that I will hook up o n the next flight, but I don't know how much delta P I'm looking for from the upper plenum to the lower plenum. My oil temps are running cold because of the better lower engine baffle I made... so if I close most of that off I should see a small improvement in CHT due to putting less oil cooling air through the lower plenum. But that's not likely to be a big improvement.

The next experiment is to put an "eyebrow" at the top of the cowl inlets to "scoop" more air into the cowl, but looking at the airplane today in the hangar it wouldn't seem to make a huge difference.

My instinct is to put louvers or gills in the sides of the lower cowl, but my instinct has been wrong several times now. I was ready to bet the house that opening up the bottom of the cowl on the English Wheel would have cured all my ills and it didn't.

You don't know anyone that wants to computer model and computer pressure/flow sim the front end of a Taylorcraft at a 12 degree AOA, by any chance...?

[crispy critter]

Re: Big Wheels Keep on Turnin'

Bill,
I told ya how to fix it,simple,cheap,and affective.

[Hank Jarrett]

Re: Big Wheels Keep on Turnin'

Kevin IS right that putting low octane auto gas in should reduce the waste heat the engine produces and it will show up in the heads first.
We could do a cooling flow study at NASA, but the cost would be more than converting your plane to electric.
Hank

[VictorBravo]

Re: Big Wheels Keep on Turnin'

Bill,
I told ya how to fix it,simple,cheap,and affective.

Even if you are 100% correct I can't use California car gas, because it has Ethanol in it. If I managed to find non-ethanol car gas someplace here near my airport it's one thing, but then finding it at some other airport I've never been at is another thing completely.

Again even if it worked 100% (you could easily be right) it would have an enormous negative effect on where I can fly and what I can do with my airplane.

It would be kinda like welding the tailwheel in a fixed position, where you're guaranteed to solve your groundlooping problem but then you have to only operate at an airport where the runway is pointed into the wind. Simple, yes. Effective, yes. Restrictive... yep!

Bill

[VictorBravo]

Re: Big Wheels Keep on Turnin'

We could do a cooling flow study at NASA, but the cost would be more than converting your plane to electric.
Hank

Electric ? Where do I sign?
(Anyone have a thousand miles or so of outdoor grade extension cord?)

Hank, other than straightforward delta P across the upper/lower plenum inside the cowl, where else would you suggest I try to get manometer readings outside the airplane that might be helpful? Pitot position at the cowl inlet and static at the outlet? Reverse pitot at the outlet? I'll be using either a Dwyer "magnahelic" diff. pressure gauge or a home-brew water manometer. Nothin too fancy... unfortunately I don't have a million little pressure transducers and a black box.

[Hank Jarrett]

Re: Big Wheels Keep on Turnin'

Bill, I think you are missing the point on the auto gas recommendation. The idea is to burn a couple of tanks full to see if that makes the problem go away. Then you have a better idea what the source of the problem is. When no-alcohol fuel isn't easily available it isn't a long term solution, but if it works you at least know some of the things that aren't causing the problem.
Hank

[crispy critter]

Re: Big Wheels Keep on Turnin'

Even if you are 100% correct I can't use California car gas, because it has Ethanol in it. If I managed to find non-ethanol car gas someplace here near my airport it's one thing, but then finding it at some other airport I've never been at is another thing completely.

Again even if it worked 100% (you could easily be right) it would have an enormous negative effect on where I can fly and what I can do with my airplane.

It would be kinda like welding the tailwheel in a fixed position, where you're guaranteed to solve your groundlooping problem but then you have to only operate at an airport where the runway is pointed into the wind. Simple, yes. Effective, yes. Restrictive... yep!

Bill

Bill,
We can't buy ethenol around here(thank god) but I have heard of people using it religisly in there airplanes(up to 5%) for years without any problems. You might want to find something to coat your cork fuel gauge that will protect it from the ethenol. Also,if you start asking a lot of A65 owners using 100LL you will find out they are pulling a cylinder every year or so(especially if they fly it often)....why do you think that is???? Between the high octane and high lead content it really is hell on those little 6:1 compression cylinders. You are going to run continue running high CHT's running 100LL. Something you might try to help you a little,and I think you have previously talked about this,is to cover about half the hole below the prop in the middle of the nose bowl. Air is not forced threw the cowl like most believe,it is sucked in from the back.All your cooling air even for the cylinders is drawn or sucked in,if you have a high volume coming threw the oil cooling baffle on the bottom of the engine then you might be taking flow or disturbing the flow through the cylinders.Also,any airplane is going to run hot CHT's when using a high AOA because because with the nose high the belly actually acts as an air block. NO cowl can draw air effectivly if you turn it out of it's slipstream.Think of it this way.Put a straw in your beer can and take a drink using your straw,next time try partially covering your straw with a piece of chewing gum and try taking another drink. This is the same thing that is happening when you are climbing at a high or maximum AOA. All this along with the 100LL is going to run high CHT's(the 100LL will do it all by itself). I have one more suggestion that might also help a little....have you ever thought about expirementing with different props????

[Larry Lyons]

Re: Big Wheels Keep on Turnin'

Gentlemen, as I know nothing about this I can only report what I know to be true. We have an early Cub with a C-65 on the field that has run auto gas with ethanol (exclusively) for years with no problems. He doesn't fly as much as he used too but we started her up this last summer after sitting unused for almost a year and it did not take that much hand propping to get her to fire off. Larry

[Gary Snell]

Re: Big Wheels Keep on Turnin'

Just did a quick scan through the thread. Not sure if these items were suggested: confirm timing set at 30-30, check for leaning due to poor condition of intake rubbers and confirm correct spark plugs installed. Also this link might offer some insight.

http://www.sacskyranch.com/eng23.htm

[flyguy]

Re: Big Wheels Keep on Turnin'

One of the things I notice about the new cars with "normal," that is, not high-performance engines, is that the factory recommends that you absolutely do not use high octane gas in them. Their statement is that the higher octane gas burns slower and will actually produce less horsepower and worse gas mileage in the lower compression and less agressively cammed and timed engines.
Seems that would be even more significant in the very low compression engines that we have.

Really appreciate your input on the 100LL Kevin. I hadn't thought it over before. I learn new and valuable things here on a regular basis.
Darryl

[crispy critter]

Re: Big Wheels Keep on Turnin'

We have several airplanes here(all but one is continetal powered)and it does not bother me at all if I fly on a long X-country to run 100LL,even if it is several tanks in a row on a coast to coast X-country. But when I'm home I run auto gas. My uncle has an old C-172 that my father and I used to own and we did the major on it our selves. We ran 100LL for the engine break in only(1st full tank).Since then it rarely see's any 100LL. It runs smoother,cooler,starts easier,and always has clean oil in it....at a 50 hour oil change the oil is just barely starting to get dirty and the oil filter is always clean as babyoil. In 650 hours smoh(completed in 1996) we have never pulled a single cylinder or had to replace a spark plug. Now,we have a C-170 with the same engine(had 300smoh when we bought it and always used 100LL).The engines get run exatly the same way but the C-170 makes a lot more X-countrys. Also my partner on the C-170 will NEVER use auto gas because he is too damn lazy to carry it with him and put it in himself(the spoils of having more money then you know what to do with),so he always flies to the nearest airport and tops off with 100LL.The engine is a little harder to start sometimes,doesn't run as smooth as the old 172. I have had to replace the spark plugs in it twice since we have owned it(once when we bought it and again last year).On top of that we have pulled a total of 4 cylinders for carbon problems and one burnt valve.We have owned this C-170 for 6 years and we have put right at 500 hours on it making about 800smoh.Using an oil filter system(same as on the C-172) the oil will turn black after about 10 hours. I change it ever 30 even with a filter because of how dirty it is.
It is not dangerous to run 100LL in your low compression engine and most problems happen slowly due to the excessive carbon build up from all the lead and the heat from the high octane. And as my uncles C-172 will show you is that even with an occasional X-country and 100LL you will never be able to tell a big difference in the engine performance or anything. But if you run consistant 100LL you will run hotter,dirty'er, and you will pay more in maintance and upkeep and have more cylinder and valve problems then you would running cheap ass car gas.

[Forrest Barber]

Re: Big Wheels Keep on Turnin'

50-50 or 60-40 with car gas , 100 Oct being 60 ; plus MMO works just fine. Watch out for alcohol but it will work if your cork is protected, OR metal . temps will be fine.
IF you have an unmodified baffle system with the lip on the bottom.

[VictorBravo]

Re: Big Wheels Keep on Turnin'

50-50 or 60-40 with car gas , 100 Oct being 60 ; plus MMO works just fine. Watch out for alcohol but it will work if your cork is protected, OR metal . temps will be fine.
IF you have an unmodified baffle system with the lip on the bottom.

Forrest, I would greatly appreciate knowing whatever you know/remember/archived on the original cooling system tests on the B models, BC models and F models. I'd really like to know what the pressure differentials and airflows were supposed to be, and what flight attitudes changed those pressures.

As you remember I built a whole new design set of baffles, then threw them away and repaired the old baffles. The airplane was flown for about 25 hours with the old baffles (repaired and re-sealed well, including installation of the "Reynolds Aviation STC"). Most of that time was with the "stock" lip on the bottom of the cowl. 4 probe CHT measurements were 425-450 within 30 seconds of taking off at full power. Yes, I had all of the inter-cylinder baffles in place.

I know that 450F is within the book limit on an A-65 cylinder but that is still way hotter than it should be for long engine lifespan.

Along the way I made a new front port side baffle to create a smoother curved "entry" into the #4 cylinder (because we postulated the air was stalled at the sharp corner of the stock baffle). Made a little difference, maybe 10 degrees on that cylinder.

At one time I had a move-able lip hinged to the back of the cowling and hooked up to the old parking brake control. Didn't solve the problem.

An engineer said to try removing the cowl grills because I have the cast grills with the horizontal bar, and it could be upsetting the flow into the cowl. So I removed them and it made a 15-20 degree difference. Now the temps were 430F after a 1000 foot climb.

As mentioned, I recently English Wheeled the lower cowl to make it hang down more, like the Lycoming cowlings but not near as big of a belly. That made almost no difference on a 60 mph IAS climb, but it made a 25 degree difference on a 70 mph climb (on one brief test in a crowded traffic pattern).

We have no Ethanol-free car gas here, and even if we did there is still a problem with the cooling system someplace that should be fixed. There's 400 HP Lycomings on corporate twins that don't run as hot as this little 65.

So please educate me about ow the stock closed cowl system is supposed to work, what makes it work or not work, and what did they find during testing... please!