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teamgrumman(at)yahoo.com
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 Posted: Sun May 29, 2011 8:49 pm Post subject: Jaguar Cowling installation questions Part 3 - engine thrust |
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Boris,
The scribe marks on the cowling are really close to the final alignment.
If I were to give you my old cowling and you installed it, I'm sure your engine would need further aligning.
That said, I think there is enough variation in the engine mounts and Lord mounts to just use them as a starting point. I have a new cowling coming for my plane. I plan on doing an initial fit with a trim to the scribe marks plus about .060 to .080 inches. That will allow me to clamp the cowling completely in place with the front of the cowling against, or nearly so, the aft spinner bulkhead. Then, I will add or subtract engine mount shims until I get it where I want it. Once the cowling and engine are in agreement, I will trim off the final amount and put in screw holes.
Bob Steward seems to think the engine should be high. That is, above the cowling. His reasoning is the mounts will sag. I don't agree. Based on testing with a cowling that gave just 1/4 inch between the alternator and the cowling, I can tell you the engine comes up A LOT during flight. With the engine slightly nose down, you can lift the engine at the spinner/prop and raise it easily 1/8 inch. Drag wise, keep the spinner below or at the cowling during flight.
I wouldn't over work the engine trust angle a lot. I've installed my cowling on at least a dozen planes and, with the exception of the plane I used for the initial fabrication, they all needed some adjusting to make fit. Some more than others.
Gary
From: b v <bvnj(at)yahoo.com>
To: teamgrumman(at)yahoo.com; Phil Kelsey <Phil(at)ReliantAir.com>; Dave Steward <dave(at)hondahaven.com>; n76lima(at)mindspring.com
Cc: Barry Schulte <flyadive(at)gmail.com>
Sent: Sun, May 29, 2011 7:28:00 PM
Subject: Jaguar Cowling installation questions Part 3 - engine thrust angle
Guys,
Please take a look. I wonder if you could please help me regarding the spacers on engine mounts.
I just bought a set of new Lord engine mounts. The old bottom ones were leaking and the spinner was sagging about 1/2 inch against the nose bowl rim. Now I have placed 1 spacer on each(as it was before) and torqued it per manual, 40 lb-feet. Before fitting the new cowl I tried the old one to check and found that engine is now hanging a little high against the nose bowl and a little to the right. Please take a look at the attached pictures.
My question is - should I try to add spacers to align the spinner to the old cowl before I fit the new cowl, and if you think I should, then why? In other words, why aligning to the old cowl would give me a better thrust angle then relying on the angle provided by the engine mount together with the set of new properly torqued Lord mounts?
Maybe I should try to measure the thrust angle?
Gary, I think you had a method of measuring up/down thrust angle. Could you please remind me how you did it and what is the angle to aim for?
I guess the left/right angle could be checked by measuring the distance from propeller tips to wings when prop is positioned horizontally. I guess one should try to make sure they are equal. Or not?
Thank you,
-Boris
P.S. By the way, you have to remove the nose strut boot before fitting the new cowl. You all probably know it, but if you don't want to cut it off, you have to remove the nose strut. I think the installation instructions don't mention this.
[quote][b]
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teamgrumman(at)yahoo.com
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| Posted: Tue May 31, 2011 12:57 pm Post subject: Jaguar Cowling installation questions Part 3 - engine thrust |
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Bob, you are always so wordy.
Gentlemen, gentlemen, let's not get your panties all in a bunch over this engine alignment.
Boris (or whoever is interested) get on the internet and find a digital level. Find one good to .5 degrees. Now, go out and measure the engine down thrust angle every AA5, AA5A, AA5B, AG5B you see. Measure at the canopy rails, and measure across the rocker boxes. You will likely find, as I have, that the down thrust angle varies between 1.5 and 7.5 degrees down. I had a new customer come in with 1 degree up but his engine was obviously wrong (WRT the cowling).
Bob, if the engine down thrust angle were that critical, we'd be given directions on how to keep safe.
Bob, if the factory set up the planes so precisely, explain how there can be so much deviation between planes regarding the number of shims required to make the engine in line with the cowling. Also explain how the space between the firewall and the spinner can vary between 39 1/2 inches to 40 inches and still meet type design.
Bob, 43.13 also says you can paint the back of the prop (the face) with black paint. Tain't so. The Sensenich TCDS specifically calls out Polane paint. Painting the prop with anything else makes the prop not in compliance with type design.
Bob, you wrote, "The method we used before Gary sent out his cowl was to align the spinner with the factory cowling," What makes you think the factory cowling was right?
Boris, the gap between the spinner and the cowling on all AA5x/AG5B airplanes is up to 1 inch. Most are around 3/4 inches. Mine is 3/16. With 3/4 of an inch gap, it really doesn't make a tinker's damn how square the engine is with the cowling. Who's going to notice? With 3/16 inch gap, you'll notice.
Bob, you wrote " leaving it perhaps 3/8" high with new mounts, as they sag with age, and in a few months they'd be allowing the spinner to align very closely with the nose bowl." I'm sure that is your experience. However, I'm having Travis send pictures of his spinner/cowling. I installed his engine in 2000 with new mounts, set up the way I set them, and it hasn't changed in 11 years.
Bob, I could argue with you and everyone else about the position of the engine in flight and while maneuvering. But, what's the point? Believe what you want. I designed the cowling to fit as closely as possible. During flight, there is about 1/4 inch between the cowling and the alternator. Alter the alignment from where I have it and all bets are off.
Boris, your best bet is to trim the cowling as I said, install it without any muffler or baffles on your engine, and then align the engine to the cowling.
From: b v <bvnj(at)yahoo.com>
To: teamgrumman(at)yahoo.com; Phil Kelsey <Phil(at)ReliantAir.com>; Dave Steward <dave(at)hondahaven.com>; n76lima(at)mindspring.com
Cc: Barry Schulte <flyadive(at)gmail.com>
Sent: Sun, May 29, 2011 7:28:00 PM
Subject: Jaguar Cowling installation questions Part 3 - engine thrust angle
Guys,
Please take a look. I wonder if you could please help me regarding the spacers on engine mounts.
I just bought a set of new Lord engine mounts. The old bottom ones were leaking and the spinner was sagging about 1/2 inch against the nose bowl rim. Now I have placed 1 spacer on each(as it was before) and torqued it per manual, 40 lb-feet. Before fitting the new cowl I tried the old one to check and found that engine is now hanging a little high against the nose bowl and a little to the right. Please take a look at the attached pictures.
My question is - should I try to add spacers to align the spinner to the old cowl before I fit the new cowl, and if you think I should, then why? In other words, why aligning to the old cowl would give me a better thrust angle then relying on the angle provided by the engine mount together with the set of new properly torqued Lord mounts?
Maybe I should try to measure the thrust angle?
Gary, I think you had a method of measuring up/down thrust angle. Could you please remind me how you did it and what is the angle to aim for?
I guess the left/right angle could be checked by measuring the distance from propeller tips to wings when prop is positioned horizontally. I guess one should try to make sure they are equal. Or not?
Thank you,
-Boris
P.S. By the way, you have to remove the nose strut boot before fitting the new cowl. You all probably know it, but if you don't want to cut it off, you have to remove the nose strut. I think the installation instructions don't mention this.
[quote][b]
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teamgrumman(at)yahoo.com
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| Posted: Wed Jun 01, 2011 9:43 am Post subject: Jaguar Cowling installation questions Part 3 - engine thrust |
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One other thing I want to add: Not all planes will require resetting the engine alignment to the cowling.
The plane from which I made the tooling had one shim per mount. My plane has 2 on the upper right. I have interchanged the two cowlings without needing to realign. I also put my cowling on a 73 Traveler to see what the interference problems might be with the airbox. That one lined up too with one shim in each location.
I tried off and on for 5 years to get some data regarding engine alignment. I knew it would be an issue because so many are so different. I have a total of 10 responses from 'the field' plus 20 or so that I have looked at. There is no one combination that always works.
Maybe Kevin can shed a little light on this and tell us what the drawings say about engine down thrust angle. "IF" the drawings say anything at all.
On another note, Bob correctly stated that engine alignment affects flying characteristics. I had a customer come in with the engine clearly offset to the left. He had had a new engine installed and the FBO just put a single shim on each mount. I asked him about the offset and he told me the FBO said that is the way the engine is supposed to be aligned to the airplane. I convinced him to install an additional shim on each left mount. This brought the engine in alignment with the cowling. After the annual, we went flying. The customer complained that he never had to use so much rudder to keep the ball centered and that it was because of the shims moving the engine over. I attempted to adjust out the rudder trim using the rudder trim tab to see if he found the difference acceptable. Bottom line was, he wanted the shims removed. That was in 2004. To this day, he's happy with the engine being offset with respect to the cowling.
In 1998, George Ismael from Rosemond, just North of Lancaster, had a new engine installed in his Tiger by an FBO in Mojave. They put the engine mounts in with the soft side toward the front on all mounts. His engine was about 3/8 inch above the cowling. I tried to convince him they'd installed the bottom mounts wrong but he was happy with that too.
From: Gary Vogt <teamgrumman(at)yahoo.com>
To: b v <bvnj(at)yahoo.com>; Teamgrumman List <teamgrumman-list(at)matronics.com>
Sent: Tue, May 31, 2011 1:51:59 PM
Subject: Re: Jaguar Cowling installation questions Part 3 - engine thrust angle
Bob, you are always so wordy.
Gentlemen, gentlemen, let's not get your panties all in a bunch over this engine alignment.
Boris (or whoever is interested) get on the internet and find a digital level. Find one good to .5 degrees. Now, go out and measure the engine down thrust angle every AA5, AA5A, AA5B, AG5B you see. Measure at the canopy rails, and measure across the rocker boxes. You will likely find, as I have, that the down thrust angle varies between 1.5 and 7.5 degrees down. I had a new customer come in with 1 degree up but his engine was obviously wrong (WRT the cowling).
Bob, if the engine down thrust angle were that critical, we'd be given directions on how to keep safe.
Bob, if the factory set up the planes so precisely, explain how there can be so much deviation between planes regarding the number of shims required to make the engine in line with the cowling. Also explain how the space between the firewall and the spinner can vary between 39 1/2 inches to 40 inches and still meet type design.
Bob, 43.13 also says you can paint the back of the prop (the face) with black paint. Tain't so. The Sensenich TCDS specifically calls out Polane paint. Painting the prop with anything else makes the prop not in compliance with type design.
Bob, you wrote, "The method we used before Gary sent out his cowl was to align the spinner with the factory cowling," What makes you think the factory cowling was right?
Boris, the gap between the spinner and the cowling on all AA5x/AG5B airplanes is up to 1 inch. Most are around 3/4 inches. Mine is 3/16. With 3/4 of an inch gap, it really doesn't make a tinker's damn how square the engine is with the cowling. Who's going to notice? With 3/16 inch gap, you'll notice.
Bob, you wrote " leaving it perhaps 3/8" high with new mounts, as they sag with age, and in a few months they'd be allowing the spinner to align very closely with the nose bowl." I'm sure that is your experience. However, I'm having Travis send pictures of his spinner/cowling. I installed his engine in 2000 with new mounts, set up the way I set them, and it hasn't changed in 11 years.
Bob, I could argue with you and everyone else about the position of the engine in flight and while maneuvering. But, what's the point? Believe what you want. I designed the cowling to fit as closely as possible. During flight, there is about 1/4 inch between the cowling and the alternator. Alter the alignment from where I have it and all bets are off.
Boris, your best bet is to trim the cowling as I said, install it without any muffler or baffles on your engine, and then align the engine to the cowling.
From: b v <bvnj(at)yahoo.com>
To: teamgrumman(at)yahoo.com; Phil Kelsey <Phil(at)ReliantAir.com>; Dave Steward <dave(at)hondahaven.com>; n76lima(at)mindspring.com
Cc: Barry Schulte <flyadive(at)gmail.com>
Sent: Sun, May 29, 2011 7:28:00 PM
Subject: Jaguar Cowling installation questions Part 3 - engine thrust angle
Guys,
Please take a look. I wonder if you could please help me regarding the spacers on engine mounts.
I just bought a set of new Lord engine mounts. The old bottom ones were leaking and the spinner was sagging about 1/2 inch against the nose bowl rim. Now I have placed 1 spacer on each(as it was before) and torqued it per manual, 40 lb-feet. Before fitting the new cowl I tried the old one to check and found that engine is now hanging a little high against the nose bowl and a little to the right. Please take a look at the attached pictures.
My question is - should I try to add spacers to align the spinner to the old cowl before I fit the new cowl, and if you think I should, then why? In other words, why aligning to the old cowl would give me a better thrust angle then relying on the angle provided by the engine mount together with the set of new properly torqued Lord mounts?
Maybe I should try to measure the thrust angle?
Gary, I think you had a method of measuring up/down thrust angle. Could you please remind me how you did it and what is the angle to aim for?
I guess the left/right angle could be checked by measuring the distance from propeller tips to wings when prop is positioned horizontally. I guess one should try to make sure they are equal. Or not?
Thank you,
-Boris
P.S. By the way, you have to remove the nose strut boot before fitting the new cowl. You all probably know it, but if you don't want to cut it off, you have to remove the nose strut. I think the installation instructions don't mention this.
[quote][b]
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