Big Wheels Keep on Turnin'

[crispy critter]

Re: Big Wheels Keep on Turnin'

Kevin it's not running lean, the climb RPM is about 2000 or 2100 max, and my baffles are sealed up tighter than 90% of all the T-crafts in the world. Running 100LL, and plugs were fairly normal.

Wish me luck...[/QUOTE]

Bill,
You say you are running 100LL and you are not having any plug problems between oil changes.You are also in the warmer Ca climate,correct? If this is the case it sounds to me like you ARE running it too lean. I have never seen an A65 on anything that will go 25 hours without trying to foul a plug or two unless it's running very hard on a cross country and then you still carbon foul one occasionally. Try running it just a half turn richer and see if it changes anything. After that I want you to try something else....run a TWO full tanks of auto gas through it. Not that high priced 93 octane crap,I mean the cheapest lowest octane auto gas you can find(86 or 87 octane). Give me an honest run at it,don't mix it with 100LL,don't put a lead additive in it. Run it down low then top it off with low octane auto gas,fly that tank out and fill it one more time. If your CHT hasn't dropped at least 10-20 degrees at the end of the second tank I'll send ya $100!!! Don't use anything with ethenol.
I honestly think where you are flying in dry climate(maybe higher elevations),running 100LL, and not fouling plugs or having any problem with them then I believe you are running it too lean. As for the auto gas...Look this one up,these engines were designed to run on 70-80 octane unleaded gas!!!!! Also,todays Low Lead gas has 2-4 times the lead content that was used in the old av-gas years ago. All that lead is hard on your little A65 and the octane is cooking her too. I know I will get a lot of non-believers when they read this but it is true.

[high time cub]

Re: Big Wheels Keep on Turnin'

Don't know zippo about building cabins or houses... but... don't it make more sense to build most all of the cabin in your backyard and then have the pieces trucked in to wherever your property is? You can run all your wiring and what not, put all the hardware and stuff in, leaving quick-connects for water, power and whatever else.

Again I don't know much about this stuff, but it sure sounds a lot easier than figuring it all out standing on a mountaintop somewhere with coyotes howling in the background.

Heck, couldn't you buy a used mobile home, rehab the interior and set it up just the way you want it at home... and just have the thing taken out to your property in one trip?

I always had the daydream of having a mobile home trailer helicoptered in to the flat top of one of those vertical wall spires in Arizona and Utah, and clear about 500 feet of brush for a STOL strip

Gee Bill,

With just a little annealing and some english wheel work, you could go from this..... http://www.dougsvintagetrailers.com/1935_united

To this.....http://www.rocioromero.com/LVSeries/LVM.htm

Jim

[flyguy]

Re: Big Wheels Keep on Turnin'

Kevin,
Don't thing we are going to find any ethanol-free car gas in Calif. Sure wish I could.

Everyone,
Request: I would like a picture/drawing/anything on the "baffle" that goes (under?) the engine on the Continentals. I don't have one and my oil temperature is always weird. Like too hot in summer and too cold in winter. A 20 degree drop in temp will cool it down 30 degrees, seems like; and it doesn't get very cool here. Is there any info here or can someone post a picture? Original like, not a later modified or such. Thanks.
Darryl

[dewhitaker]

Re: Big Wheels Keep on Turnin'

Here are some pictures of the crankcase baffle. I believe a previous owner at some point did some cutting on it for whatever reason, but you get the idea. These pictures were taken to show my new installation of pushrod tubes.

[VictorBravo]

Re: Big Wheels Keep on Turnin'

I was looking at your under engine baffle and it has a sharp edge

However this should affect the oil temp and not so much the CHT unless your oil temp is running hat also.

Oil temps are low now, thanks to that baffle. The sharp edge would possibly cause a separation in free stream, but in that application I think it's working fine because it is in a closed duct. There's nowhere for the separated air to go, it still is forced through that channel under the case. Obviously it would be a lot harder to build that baffle with a radius, but in this case the baffle worked wonders for the oil temp... like 30-40 degrees.

As far as the car gas, I know nothing about it so I cannot argue with you. But the reality is that I have to solve this problem using avgas, regardless of whether the problem would be better or worse using other gas. After I finish !(#%^ working today, the test flight will show the result.

[tawadc95]

Re: Big Wheels Keep on Turnin'

my plugs tend to do the same as what it sounds like Bill's do.
nice tan color and maybe one or two small lead deposits on a couple of plugs,and that is between annuals.
I run it at full throttle full time because the oil consumption goes up if I throttle back.
if I run at 2300 it burns a qt every 16 hours...at full throttle I don't know how long it takes to burn a full qt but I assume 50 hrs since it is down a half qt when I change it at 25.
I tend to think it is not just how you run them but how often they are run just my gut talking there and comparisons amongst friends engines

[flyguy]

Re: Big Wheels Keep on Turnin'

David, thanks for the pix. That is about what I thought it would be. Now I understand the shape of the inlet on the front bowl.

RE: the 5 percent ethanol car gas we have here. I know an old timer owner that has been running several planes on it for years. Never had any kind of problem according to him.
Two reasons I don't use it. Insurance company could use it as an out if they knew. It will slowly eat away at the epoxy coating on my gas gauge float.
Ethanol can be really nasty stuff for some materials, but I don't think there is anything else left on my plane that it would affect.
DC

[crispy critter]

Re: Big Wheels Keep on Turnin'

Oil temps are low now, thanks to that baffle. The sharp edge would possibly cause a separation in free stream, but in that application I think it's working fine because it is in a closed duct. There's nowhere for the separated air to go, it still is forced through that channel under the case. Obviously it would be a lot harder to build that baffle with a radius, but in this case the baffle worked wonders for the oil temp... like 30-40 degrees.

As far as the car gas, I know nothing about it so I cannot argue with you. But the reality is that I have to solve this problem using avgas, regardless of whether the problem would be better or worse using other gas. After I finish !(#%^ working today, the test flight will show the result.

Bill,
The 100LL might be your problem all together. Anyone else running straight 100LL all the time that has a CHT in thier A65 t-craft?

[dewhitaker]

Re: Big Wheels Keep on Turnin'

Hey flyguy, I should have posted a side profile also. Here you go....

[flyguy]

Re: Big Wheels Keep on Turnin'

Nice shot of the side. Thanks, that is a very helpful photo. Sure doesn't look like there is much room for the air to flow under the case. Maybe more space than it looks like?

Kevin, I have an 85 and I got high temps originally the same as Bill, that is, the two rear cylinders, say 400 to 450F., and then the hottest one went down when I opened up the clearance on the rear baffle on that side. (made it match the other side.)
Both hot cylinders go down some more when I block off about 3/4 of the air inlet in the lower center of the nose cowl, as I have said here before. That is running 100LL.
DC

[VictorBravo]

Re: Big Wheels Keep on Turnin'

Test flight today, brief but valid. Lower cowl stretched and installed on spacer, no other mods since last flight.

First takeoff and climb at 58-62 mph indicated, hot cyl. (#1) temperature 430F by the time I climbed to pattern altitude (1000AGL) . (This is the same temperature as the last couple of flights after I removed the cast aluminum cowling grill to remove all obstacles in the airpath. Removing the grills dropped the temps 10-15 degrees from the previous 440-455 F on the gauge after a full throttle climb to 1000AGL to 430F. Unlike the stamped grills, the cast grills have a horizontal bar blocking 15-20% of the area)

Performed touch and go.

Second climb was at 72-74 mph IAS, cyl temp on hot cyl was 405F at 1000AGL.

Spent lunch afterward talking to our EAA chapter's local aero engineer. The only reason we could surmise that the increase in cowl air exit would NOT have a dramatic effect on CHT was the possibility that the forward upper nose cowl (above the top of the inlet) was acting like an airfoil at the high AOA (at 58-60 mph), and generating a localized low pressure area that was trying to pull air out the front of the cowl instead of push it into the inlet.

Reducing the AOA to climb at 72 mph might have reduced this effect by putting more of the air inlet in the maximum local pressure (like a giant pitot tube).

However I have no intention of having to climb at 70+ to keep the CHT reasonable. That means the airplane is flying me instead of me flying it. Not on my watch. with money and time I could perform a lot of tests, instrumentation and video recordings that would be of great value, but I don't have that kind of money to invest.

The final two experiments are now on the table for me to think about:

1. Put a small scoop on the top of the cowl inlets to make sure the upward flow trying to get over and around the cowling actually is scooped into the cowling. This would prove or disprove the high AOA explanation and provide a solution. However, the distance between the trailing root edge of the prop and the front of the nose cowling is one pinky finger width, so there ain't much room to grab much of that air.

2. Cut louvers or gills on the sides of the cowl to let more air out. After today's test flight I'm no longer sure the problem is the exit, because I opened it up enough so it should have shown a significant improvement. This will only be done if experiment 1. above does not work.

If none of these things work I am at the point of surrender, which will also definitely result in my losing respect and loyalty to the Taylorcraft design. I cannot believe the cowling design is so bad and wrong on an airplane that was so well designed otherwise.

If anyone has a nose bowl that is ugly and patched up for a very cheap price, I would like to buy it and use it for experiments to solve this problem. No I do NOT need a nice pristine nose bowl, I want a beat up one I can hack up and modify with a clear conscience..

If anyone has the scientific numbers and results of the testing on the closed cowl, the manometer readings, the results of tuft testing or oil pattern testing or anything that will explain how and why the cowl was designed the way it was... I'd sure like to see it. This has long surpassed a flight safety and engine longevity issue for me, it's now a contest of wills between me, s/n 2387, and whoever the engineer is that designed and certified this cowling a hundred years ago. If I lose this contest, I'm afraid I will be a very sore loser.

[crispy critter]

Re: Big Wheels Keep on Turnin'

Dammit Bill,put some car gas in it(86-87 oct) and give it at least two tanks worth!!!! There's gotta be someplace in Ca where you can find auto gas without ethonal or at least 5% or less. Try a bulk plant or something. "IF YOU USE IT,THEY WILL COOL DOWN!!!! Maybe not a lot at first but after a half tank or so you will start to see a big difference. Back when I was learning to fly our old Cessna 170 always ran hot in the summer,oil temp right at the red and CHT was worse. Switching to auto gas at that time brought the CHT down about 50 degrees which brought the oil temp down slightly as well. Then we extended the lip at the back of the lower cowling making it stick down an extra 1 and 1/2 inch. This brought the oil temp down about 10-15 degrees and helped cool the CHT another 10-20 degrees. In the end our CHT went from about 450-470 on the hottest to about 380-400.....and all we did was switched to auto gas and put a little lip extention on the bottom of the cowl. Also,in the 600 hours before switching to auto gas Dad had to pull at least one cylinder each year(sometimes 2 cyls) because of carbon problems. After switching to auto gas the engine ran another 800 hours problem free without pulling a single cylinder for any reason! Try that using 100LL .

[Ron Coleman]

Re: Big Wheels Keep on Turnin'

Kevin..
Bill is doing what he wants to do. He already knows that the cylinders make heat, not the cowling, but he has formulated a problem and a solution. That is where the fun is>

RonC

[flyguy]

Re: Big Wheels Keep on Turnin'

Bill as you and I have discussed before, everything that I see points to the air that gets back to cool the rear cylinders is already at an elevated temperature from passing over the front and top of the front cylinder fins.
One sure fix is to get some unheated air to the backside of the rear cylinders. I have some ideas how to do that, but they are pretty drastic and perhaps ugly.

I'm still thinking, as one possibility, of a "insulated" duct over the top along side of the crankcase. Even better would be two flat ducts along the top of the cowling that would take cool air from above the nose bowl back to the rear cylinders and also provide clearance for tall spark plugs.

I'm going to work on doing some more measurements on mine as soon as it is flying again. Come to think of it, that would be a good project to get measuring equipment for, and set up while waiting for struts. Think I might start by ordering me a good sized roll of copper-constantin thermocouple wire and a matching generic meter.
Darryl

[VictorBravo]

Re: Big Wheels Keep on Turnin'

Bill as you and I have discussed before everything that I see points to the air that gets back to cool the rear cylinders is already at an elevated temperature from passing over the front and top of the front cylinder fins.

Naw, I actually disagree with that being the big cause of the problems. On my airplane the hot cylinders are 1 and 4, meaning right rear and left front. I also do not agree that the air temp is elevated that much just from passing by the front cylinder. I am convinced it is a "mass flow thru the system" issue.

We're dealing with a very slow airspeed on climb (65 or less for most of us), which means we have very little "Q" or dynamic ram air pressure to power the whole system.

The bottom of the airplane is sensing higher local air pressure in a climb... you might have a significant fraction of that "Q" acting on the bottom of the boot cowl at high AOA, which would be moving towards an adverse pressure gradient. Then you might have some of the 65 miles an hour taken away from the front by virtue of it flowing upward and over the top of the cowl. By the time you're done, you might only have 2/3 or half of the pressure differential than you would have in level flight at the same speed.

If Hank (or any other experienced aero engineer) would care to jump in on this discussion I'd be overjoyed to hear what his experiences and training might offer in the way of explanations and solutions.