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 Post subject: Re: weights
PostPosted: Tue Feb 20, 2007 12:12 pm 
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Bill Greenwood wrote:
Glen, I don't operate the big boys, but the reason weight is factor is because it is such a determinate on performance. At heavy weights takeoff roll is longer, and climb to cruise level off takes longer. You may need more power at heavy weight to have the same level of safety like a go around. With higher power settings you may shorten the time til you can cruise. Jack Rouse feels the current gas is like lower octane or leaner; like so much of this info it is as much folklore as scientific fact, neither proven or disproven. I thought there was 130 or 145 gas Near the End of the war. Merlins in Spitfires had an ok to use a brief overboost on 145 to, I think 20 lbs or 80" which was 2050 hp, but really reduced engine life.



Hi Bill,

weight is a factor for the reasons you state. However, that has nothing to do with the performance of the engine; ie cooling. The aircooled engines use a lot of fuel on takeoff just for cooling purposes. If you aren't providing that fuel, you won't be getting the proper cooling. Also, don't know about you, but it doesn't matter what I weigh, the same amount of power will always be used for a go-around. There may have been higher octane fuel at the end of the war, but none of the engines were designed to operate on it like some of the post-WW2 engines. eg R-1820 -80 series in T-28's, S-2's, Hu-16's, Super DC3's etc.



See ya at NWOC.

Glenn

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 Post subject: Physics and Cooling
PostPosted: Tue Feb 20, 2007 12:51 pm 
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Glenn and B29 Flt Eng,
I am ready to abandon anything that is OWT, with right physics and chemistry. I am definitely on board with the excess fuel for engine cooling at take off power. But why all the converts to the lower power settings on take off, and the lower maintenance? I can see that if just one less cylinder is changed in a year, that is going to be looked at by an operator as sterling performance, and might be a fluke, but aren't several people doing this? The 91/98 octane stateside training explanation is a very good one for alternative minimum power settings, but doesn't this apply in the new formulation process, if 100 LL is more like 91/98 octane? Thanks to Randy H for reminding me, but aren't the more modern octane rating techniques actually making us run gasoline with lower octane ratings- what I mean is that older fuels naturally had a higher octane rating due to inaccuracy in the cracking process and octane calculation? Again, I am not the expert, only repeating what may be OWT, but am very curious about the chemistry/physics of the whole subject. So here are some follow up questions that may spur further discussion:

1. How does modern octane rating formulation and burn data on gasoline correlate with older octane rating formulation and older burn data?

2. How are you altering the actual chemistry/heat cycle of the engines (R2600 especially) by employing Alternative Minimum Power Settings (AMPS) when using modern 100LL?

3. How, considering the modern scarcity of running engines, would you be able to counterpoise these two methods of operation in order to lend credibility to either method?



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 Post subject: Re: Physics and Cooling
PostPosted: Tue Feb 20, 2007 2:25 pm 
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Forgotten Field wrote:
Glenn and B29 Flt Eng,
I am ready to abandon anything that is OWT, with right physics and chemistry. I am definitely on board with the excess fuel for engine cooling at take off power. But why all the converts to the lower power settings on take off, and the lower maintenance? I can see that if just one less cylinder is changed in a year, that is going to be looked at by an operator as sterling performance, and might be a fluke, but aren't several people doing this? The 91/98 octane stateside training explanation is a very good one for alternative minimum power settings, but doesn't this apply in the new formulation process, if 100 LL is more like 91/98 octane? Thanks to Randy H for reminding me, but aren't the more modern octane rating techniques actually making us run gasoline with lower octane ratings- what I mean is that older fuels naturally had a higher octane rating due to inaccuracy in the cracking process and octane calculation? Again, I am not the expert, only repeating what may be OWT, but am very curious about the chemistry/physics of the whole subject. So here are some follow up questions that may spur further discussion:

1. How does modern octane rating formulation and burn data on gasoline correlate with older octane rating formulation and older burn data?

2. How are you altering the actual chemistry/heat cycle of the engines (R2600 especially) by employing Alternative Minimum Power Settings (AMPS) when using modern 100LL?

3. How, considering the modern scarcity of running engines, would you be able to counterpoise these two methods of operation in order to lend credibility to either method?



[/code]


Have not seen any evidence of lower maintenance with reduced power takeoffs. Actually, I've seen more. And it is usually seen in cylinder changes as a result of hotter running cylinders. I know some out there swear the opposite. However, I know of one operator who has so many bad exhaust valves due to overheating, but still won't believe the data. Don't know why so many are ignoring all that has been written, by the manufaturers and documented in tests for the sake of OWT. 100LL is the SAME as 100/130. Get a hold of ASTM D910 and see for yourself. The method of measuring octane rating in avgas has not changed. 100 is still 100.

Ok, to answer your specific questions. 1) there is no difference. The fuel flow data in the manuals is pretty accurate. Was then, and is now. 2) lets use the R-2600-35 in a B-25. By using the 91/98 numbers you aren't getting the power enrichment the engine was designed to have for adequate cooling. As a result you will have higher CHT's on takeoff. Been proven time after time. Heat is a cylinders enemy, especially if it can not be removed as it was designed to. As far as I am concerned, the lower you keep the temps, the better. Gas is still cheaper than cylinders. <<older fuels naturally had a higher octane rating due to inaccuracy in the cracking process << you are assuming that the fuel ALWAYS came out with a higher than advetettised rating. Could have easily gone the other way too. 3) the manufacturers had all the high priced help to figure this out. The military and airlines flew them thousands and thousands of hours. If a better way exists I'm happy to review the data. But so far I haven't seen any. Why re-invent the wheel.

My 2-cents after 25 years of maintaing and flying these things.

Glenn

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 Post subject: Radial engine operation
PostPosted: Tue Feb 20, 2007 3:21 pm 
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As far as 100LL being "The same as 100 Octane",that may be true,however,it isn't going to meet the 130 Performance rating of 100/130.A few years ago,Neptune Aviation had a number of failures with their R-3350's.Most of them had to do with upper ring land failures,especially on the master rod cylinders.While trying to find a cause,they noticed that all of the affected airplanes had cycled through Moses Lake.Jeff Akridge at Columbia Pacific Aviation (the local FBO) hand carried fuel samples to a lab in Seattle,while Neptune did the same with fuel sumped from Tanker 05 at Moses Lake.The results of both tests indicated a rating equivalent to 108 Octane.That was better than I'd thought they would get,but it still isn't close to 130.

Several years ago,we were still able to get 100/130 in Montana.With the DC-7,once we'd cycled through a few fuel loads and ended up with straight 100/130,there was a noticable lowering of CHT's,especially at 10% lean cruise.With the direct fuel injected engines on the DC-7,we have dual CHT gauges with probes on each row of cylinders.This is to monitor and troubleshoot fuel distribution problems.The front and rear split in temps that is common using 100LL lessened cosiderably when using 100/130.We had similar results in the 1980's in Alaska with these airplanes when tankers were supplied with 115/145 and our standard fuel in the Lower 48 was 100/130.

There is also the topic concerning lead acting as a lubricant for the valve seats and guides.When auto fuel switched to unleaded,older engines suffered to various extents due to a similar problem.I still have a 1977 Dodge Ramcharger.The owner's manual warns to run at least one fuel load in ten of leaded fuel.Of couse,leaded auto fuel is no longer available,but you can buy "Lead Substitute Additives" at any Wal-Mart for cars.I haven't seen anything approved for aircraft engines.


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PostPosted: Tue Feb 20, 2007 3:35 pm 
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Larry Kraus wrote:
As far as 100LL being "The same as 100 Octane",that may be true,however,it isn't going to meet the 130 Performance rating of 100/130.A few years ago,Neptune Aviation had a number of failures with their R-3350's.Most of them had to do with upper ring land failures,especially on the master rod cylinders.While trying to find a cause,they noticed that all of the affected airplanes had cycled through Moses Lake.Jeff Akridge at Columbia Pacific Aviation (the local FBO) hand carried fuel samples to a lab in Seattle,while Neptune did the same with fuel sumped from Tanker 05 at Moses Lake.The results of both tests indicated a rating equivalent to 108 Octane.That was better than I'd thought they would get,but it still isn't close to 130.

Several years ago,we were still able to get 100/130 in Montana.With the DC-7,once we'd cycled through a few fuel loads and ended up with straight 100/130,there was a noticable lowering of CHT's,especially at 10% lean cruise.With the direct fuel injected engines on the DC-7,we have dual CHT gauges with probes on each row of cylinders.This is to monitor and troubleshoot fuel distribution problems.The front and rear split in temps that is common using 100LL lessened cosiderably when using 100/130.We had similar results in the 1980's in Alaska with these airplanes when tankers were supplied with 115/145 and our standard fuel in the Lower 48 was 100/130.

There is also the topic concerning lead acting as a lubricant for the valve seats and guides.When auto fuel switched to unleaded,older engines suffered to various extents due to a similar problem.I still have a 1977 Dodge Ramcharger.The owner's manual warns to run at least one fuel load in ten of leaded fuel.Of couse,leaded auto fuel is no longer available,but you can buy "Lead Substitute Additives" at any Wal-Mart for cars.I haven't seen anything approved for aircraft engines.


Hi Larry,

interesting, but I have to ask: was the lab measuring octane the auto way or per ASTM D910? If you look at this document, the specifications for aviation fuel, there is no difference between the old green fuel and the current blue fuel. I also understand that the 3350's in the Neptune's and the R-2800 CB-17's in the DC-7's were originally designed for 115/145. We didn't see any difference with the DC-3's we were operating when the change was made from green to blue, and I haven't seen any difference in the 2600's we operate either.

As far as lead as a lubricant...................lead only does only one thing: raises octane level. It is not a lubricant.

Glenn

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 Post subject:
PostPosted: Tue Feb 20, 2007 7:51 pm 
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I agree fully warbirddriver, that is what TEL does and doesn't do.

A not so scientific test my brother and I did. Using a VW aircooled engine, some years back.
Using 100 av gas and then the highest octane mo unleaded mo gas at the time. (As mentioned on this thread about the R3350 CHT being lower with the good old 100 vs the LL stuff.)
The CHT was appreciably lower with the av gas than the unleaded.
I don't remember the figures but I'm thinking close to 100 deg F.
Anyway I feel this is what TEL did the best, and lower temps will definatly help the valves. And besides with the lead scavengers and high temps would there be any lead left?


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PostPosted: Tue Feb 20, 2007 8:37 pm 
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warbirddriver wrote:
Larry Kraus wrote:
As far as 100LL being "The same as 100 Octane",that may be true,however,it isn't going to meet the 130 Performance rating of 100/130.A few years ago,Neptune Aviation had a number of failures with their R-3350's.Most of them had to do with upper ring land failures,especially on the master rod cylinders.While trying to find a cause,they noticed that all of the affected airplanes had cycled through Moses Lake.Jeff Akridge at Columbia Pacific Aviation (the local FBO) hand carried fuel samples to a lab in Seattle,while Neptune did the same with fuel sumped from Tanker 05 at Moses Lake.The results of both tests indicated a rating equivalent to 108 Octane.That was better than I'd thought they would get,but it still isn't close to 130.

Several years ago,we were still able to get 100/130 in Montana.With the DC-7,once we'd cycled through a few fuel loads and ended up with straight 100/130,there was a noticable lowering of CHT's,especially at 10% lean cruise.With the direct fuel injected engines on the DC-7,we have dual CHT gauges with probes on each row of cylinders.This is to monitor and troubleshoot fuel distribution problems.The front and rear split in temps that is common using 100LL lessened cosiderably when using 100/130.We had similar results in the 1980's in Alaska with these airplanes when tankers were supplied with 115/145 and our standard fuel in the Lower 48 was 100/130.

There is also the topic concerning lead acting as a lubricant for the valve seats and guides.When auto fuel switched to unleaded,older engines suffered to various extents due to a similar problem.I still have a 1977 Dodge Ramcharger.The owner's manual warns to run at least one fuel load in ten of leaded fuel.Of couse,leaded auto fuel is no longer available,but you can buy "Lead Substitute Additives" at any Wal-Mart for cars.I haven't seen anything approved for aircraft engines.


Hi Larry,

interesting, but I have to ask: was the lab measuring octane the auto way or per ASTM D910? If you look at this document, the specifications for aviation fuel, there is no difference between the old green fuel and the current blue fuel. I also understand that the 3350's in the Neptune's and the R-2800 CB-17's in the DC-7's were originally designed for 115/145. We didn't see any difference with the DC-3's we were operating when the change was made from green to blue, and I haven't seen any difference in the 2600's we operate either.

As far as lead as a lubricant...................lead only does only one thing: raises octane level. It is not a lubricant.

Glenn


Glenn,

With all due respect, lead was definitely a lubricant in addition to an octane booster. Mollecular lead deposits increased the life of valve seats, guides, and stems. Larry is absolutely correct. When the fuel changed in the general automotive market, there was considerable research done to come up with alternative materials that possessed better self lubricating properties for valve seats, stems, and guides. :)

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 Post subject: Octane/power
PostPosted: Tue Feb 20, 2007 9:54 pm 
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One thing about FIFI is it has direct fuel injection so it doesn't get the cooling effect of the rich mixture. The fuel is injected directly into the cylinder just above the spark plug. Talking with Pete Law (THE MAN in Reno racer fuel systems), once the engine is above about 65% BMEP, you don't get any more cooling from the fuel. Like someone said earlier, the less weight, the less time you spend at high power settings. During flights in FIFI at high outside air temps we would be running the CHT at red line until the first power reduction. Once that power was reduced to climb power you can almost see the CHT drop. Thats why we always drop the nose once we get airborne to let the airspeed build up. The less weight, the faster you accelerate. The higher the BMEP, the hotter the engine will get. If I remember correctly, R-2600s have a max manifold pressure (MAP) of 44", R-1820s, R1830s are about the same. The R-3350s in FIFI are rated at 49" (52" war emergency) with 100/130. The early R-3350s also had cast aluminum cylinder heads versus the post-war forged cylinder heads which had a higher tolerance for high BMEP due to better cooling fin design (about 70% ? better).


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 Post subject: Re: Physics and Cooling
PostPosted: Tue Feb 20, 2007 10:01 pm 
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Forgotten Field wrote:
aren't the more modern octane rating techniques actually making us run gasoline with lower octane ratings- what I mean is that older fuels naturally had a higher octane rating due to inaccuracy in the cracking process and octane calculation?


That's my understanding based on what my roomie said back in the day -- that in the past, the fuel was not refined as precisely and the octane ratings were not reflective of the actual content of the fuel.

Current fuels are refined more purely (probably the wrong word...but I'm not the petrol engineer!), and the octane rating more accurately represents the actual octane content of the fuel.

I guess my real point originally was to counter the comment that I hear quite regularly from warbird people about the "crappy" gas that's being produced today. While this may be true with respect to Mogas, the aviation fuel of today is much better than the avgas of decades ago.


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 Post subject:
PostPosted: Tue Feb 20, 2007 10:10 pm 
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Last edited by Former Member 2 on Sun Sep 23, 2007 11:58 am, edited 1 time in total.

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PostPosted: Wed Feb 21, 2007 10:00 am 
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<< lead was definitely a lubricant<<


sdennison......my engineer buddy that works for Shell say lead is definetly NOT a lubricant. If you have any data that show otherwise, I'd be happy to see it.

Glenn

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 Post subject: lead
PostPosted: Wed Feb 21, 2007 10:48 am 
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Glen, I think I have read or heard over the years from overhaulers that lead is beneficial to valve seats. Lubicant may be the wrong word. it could be a direct benefit, a cushioning, or indirect from preventing donation. It could also be mostly myth. As a casual observer, it seems like B-17s, etc. frequently have to change cylinders ?. Was this the same in military or airline service, and does sitting on the ground idling, which happens a lot at modern airports and big airshows affect engine cooling? Also most Merlins now run Phillips 25w-60, or at least Aeroshell A D; what kind of oil are radials using?

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 Post subject:
PostPosted: Wed Feb 21, 2007 9:41 pm 
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Bill, FIFI uses straight mineral oil, 60 weight. I'm guessing the military and the airlines had the same problem of jug changes. Since our pocket book wasn't paying for it we just didn't realize how often it happened. Just speculating.... My old Guard unit flew the last KC-97s (up to 1978), my wife was in the unit then and says they always had a jug or two to change in Goose Bay on the way to Europe.


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 Post subject:
PostPosted: Wed Feb 21, 2007 9:58 pm 
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We run Aeroshell 120W in all the radials except the C-45, it has a new left engine, will run mineral on it for about 50hrs, the T-6 and PT-17.
It is easier to get AD oil while on the road, ever try to get 4 or 5 gallons of mineral oil at a FBO ?

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 Post subject:
PostPosted: Wed Feb 21, 2007 10:39 pm 
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We order a drum of oil ahead of time at each stop (Shell part number 60006). We also installed a oil transfer system from a KC-97 in the aft bomb bay. With that system we can suck the oil from the drum and pump (electric) it to each engine as required. Very nice system. It sure beats using five gallon jugs and a funnel on top of the wing. We also removed the center fuel tank and installed a 140 gallon oil tank in its place to store extra oil (one of our pilots built it!). Each engine on FIFI has an 85 gallon oil tank. The largest oil burn I've seen is about 5 gallons an hour.


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