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flyadive(at)gmail.com
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 Posted: Sun Oct 31, 2010 6:06 am Post subject: I.E., Engine "THRUST" angle |
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Hello Gary:
GREAT QUESTION!
And you picked out the discrepancies to making a General Statement of Zero Thrust.
I'm sure you have heard the statement 'set your engine to Zero - Zero', VERY difficult to do.
I took the time when installing my engine to the first Zero but the second was WAY TOO VARIABLE.
First ZERO - Side Thrust. I did that by putting the prop on the engine and placing it Horizontally. Then MEASURE from the tip of the prop to a 'fairly known' place on the wings leading edge. Use a Stall Strip, an End of a wing Panel or the end of the wing.
The end of the wing ADDS more errors to the equation. When you get the measurements from both prop blades equal you are - Should be Zero Side Thrust.
Second ZERO - Down Thrust. I gave up on that one. WAY too many variables. There was no point I could measure or do a Bubble Level on to prove that one out. I just LUCKED OUT... I set it and when the cowling and nose bowl went on the UP - DOWN spacing LQQK'd good.
AHHhhhhhhh Just had an idea on how to set ZERO Down Thrust.
1 - Bubble level from the canopy rails Forward & Aft.
2 - Bolt on a 'Machinist's Knee (90 Angle Used for measuring) to the prop flange.
3 - And then take a bubble reading Forward & Aft off the Machinist's knee.
Not easy, as the engine must be in place right from the start with the first bubble reading.
Easy to theorizer hard to do.
Barry
[quote][b]
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teamgrumman(at)yahoo.com
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| Posted: Sun Oct 31, 2010 9:34 am Post subject: I.E., Engine "THRUST" angle |
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Finally, someone comes up with some good engine mount dimensions. I've only been asking about the distance to the spinner for 4 years. Now, Let's see what I can do with it.
From: discover <923te(at)att.net>
To: teamgrumman-list(at)matronics.com
Sent: Sat, October 30, 2010 5:34:31 PM
Subject: Re: I.E., Engine "THRUST" angle
--> TeamGrumman-List message posted by: "discover" <923te(at)att.net (923te(at)att.net)>
As I understand it:
At the factory the engine mount is installed on the engine while the engine is on a stand before being mounted to the airframe. Typically one shim / washer is installed on each of the 4 mounts.
Initially, the engine mount is received from the mount maker and set on a granite surface that is certified within certain limits to be 'flat'. Certified, calibrated height gauges are used to measure the height of components of the mount from the flat surface and it is determined that the mount conforms within a certain tolerance to the drawings. All the mounts are to be the same within that close tolerance.
At station 10 the engine / mount assembly is installed on the airframe. As I understand it, Station 10 determines / ensures the proper alignment of the engine. Station 5 determines / ensures proper alignment of the cowl to the engine that has already been proven to be in correct alignment at station 10.
Field procedure for the verification of the proper alignment of the engine is to align the back of the spinner to the front of the nose bowl. Adjustments are made by shimming the engine to the nose bowl. The cowling nose bowl is the determining factor for alignment of the engine after the airplane leaves the factory, this is what I was trying to communicate to Gary recently and why I ask him repeatedly to adjust my engine to fit the original cowling before he installed the Jaguar cowling.
This alignment is made at the factory to be within .020" of center between the two. With 1 shim in each mount the front of the nose bowl on the cowling should be at station 10.775 i.e. 39.225" from the firewall (50- 10.775 = 39.225)
When Gary and I were discussing the misalignment of his Jaguar cowl on my Tiger I probably misspoke about zero thrust. I was talking in the context of the relationship between the nose bowl and the spinner where as above the difference in alignment is required to be less than .020 when the plane leaves station 5 at the factory.
As I understand it, the thrust angle of the engine is 0 in the vertical plane and 2 deg right in the horizontal plane.
If one were to build 4 jigs for the engine mount in place of the 4 rubber isolation mounts and such jigs would hold "dowel rods" and those dowels were extended forward they would intersect at a focal point. This focal point would be 28.72" forward of the firewall and be .032" left from butt line zero and sit .23" above the Waterline i.e. Wl +45.230. The waterline is spec'd to 3 decimal places so this position specification has 3 digit accuracy.
If one were to look at the backbone of the engine (as I understand this it is the seam at the back of the engine) and compare this with a hole in the tab on the engine mount where the ground strap is attached one should see these two points in alignment. These two aligned points are offset .085" left of the butt line.
If one were to bisect the distance between the upper engine mounts, center to center of bolt and extend that point parallel with the longitudinal axis/ water line/ butt line, into the firewall one would measure a 1.316" offset left of the butt line.
These figures were given me during a telecon with someone who knows this stuff and I believe them to reflect accurately, however take them at your own risk as I cannot guarantee that I understood properly or heard accurateley.
Now, if I can get back to the hangar to start the extensive fiberglass work required to "repair" and "refit" the Jaguar cowl to the correct position then I may someday give you some good flight test data on the really cool looking Jaguar cowl.....
Fit of Jaguar AFTER aligning engine with factory cowl:
http://picasaweb.google.com/N923TE/Jaguar#5533998216035740578
http://picasaweb.google.com/N923TE/Jaguar#5533998217466856546
Fit of Jaguar both before and after engine alignment:
http://picasaweb.google.com/N923TE/Jaguar#5533998217210050226
http://picasaweb.google.com/N923TE/Jaguar#5533998221583687538
A hole in the baffle that needs to be made larger. Large enough to access the engine mount nut with a tool.
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