Today's Message Index:
----------------------
1. 07:06 AM - Re: I.E., Engine "THRUST" angle (FLYaDIVE)
2. 10:34 AM - Fw: Clytie's Ultrasound (Gary Vogt)
3. 10:34 AM - Re: Re: I.E., Engine "THRUST" angle (Gary Vogt)
4. 11:56 AM - Engine "THRUST" angle: Update (Gary Vogt)
5. 12:07 PM - Larry's plane. Finally finished. Except for the cowling. (Gary Vogt)
6. 05:38 PM - Engine "THRUST" angle (923te)
Message 1
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| Subject: | Re: I.E., Engine "THRUST" angle |
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
Message 2
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| Subject: | Fw: Clytie's Ultrasound |
----- Forwarded Message ----
From: Gary Vogt <teamgrumman@yahoo.com>
Sent: Thu, October 14, 2010 8:52:46 PM
Subject: Clytie's Ultrasound
Hi,
Here is Clytie's ultrasound. Thanks for your help.
Gary
Message 3
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| Subject: | Re: I.E., Engine "THRUST" angle |
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@att.net>
Sent: Sat, October 30, 2010 5:34:31 PM
Subject: TeamGrumman-List: Re: I.E., Engine "THRUST" angle
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.
http://picasaweb.google.com/N923TE/Jaguar#5533999455320704962
Your Fellow Grumman Enthusiast,
Ned
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=317535#317535
Message 4
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| Subject: | Engine "THRUST" angle: Update |
This is indeed good information. Thanks Ned. I've been asking for dimensions
for at least 4 years.
As stated, before I started the Jaguar cowling, I used 1 shim on each mount. I
picked one on each mount because I figured I could remove one and add one to
each if necessary. I used an AG5B cowling for the bottom half and fabricated
the top from foam. Not sure how Ned's cowling got so much down angle. Unless
the plane I used as a mock up was wrong.
The engine mounts, vibration isolators (shock mounts), and installations in
general must have a lot of tolerance stack-up. Otherwise, they'd all take the
same number of shims . . . always.
In your 'field alignment procedure,' you state that the proper alignment is to
the front of the nose bowl. I've seen cowlings forced out of alignment by 1/4
inch. How does one tell if the cowling is right?
Since I didn't have Ned's plane to do the initial fitting (he wanted it done in
a week), I pre-fitted the cowling to an AA5B that I first aligned to the cowling
on my plane. As it turns out, the cowling attachment nutplates on Ned's AG5B
are not in the same place as the nutplates on an AA5B. For some reason, they
have been changed. The result was that the holes I drilled into Ned's cowling
before he brought his plane were not aligned with the nutplates on Ned's plane.
Questions for Ned
(1) What were the shims count in your final set-up? I forget.
(2) What are they after the alignment?
(3) How did you align your engine? Really. Did you get another cowling and
install it then align the engine to that?
(4) If not, What was your procedure?
The 39.225 inches alignment dimension is fine for the stock cowling. What I
need is the dimension to the face of the crank flange.
It's curious to me what the final result will be. I did a search on engine
thrust angle.
"Down thrust is a way of reducing the need to retrim an airplane with power
changes. As you increase airspeed by adding power the stabilizer will pull
downward with a stronger force, and an airplane will climb. You can either add
more down elevator to reduce the climb or you can let the extra power pull the
nose down. There is an oft-overlooked benefit of downthrust. When added to an
airplane it also lowers the angle of attack that causes P-factor, thus reducing
the P-factor, and often eliminating the need for right thrust because the
P-factor has been neutralized in the cruise condition."
Ned had stated to me that his plane wanted to go to the (right? or was it left?)
when he got it. He said it didn't fly straight at any rate. My plane has no
trim tabs and flies straight with the same cowling. To me, that is interesting!
Does the prop have that much of an effect? Could it be the 3-blade prop?
The RV guys set zero thrust by first leveling the plane, then putting a level on
the rocker boxes or push rod tubes. I'm going to try that.
Remote control guys have a whole process they go through since they are on the
outside looking it.
Some planes have a lot of engine down thrust. See attached. The Corsair,
Grumman Wildcat and Hellcat all have a large down thrust.
I'm really curious which is faster on a Tiger.
Message 5
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| Subject: | Larry's plane. Finally finished. Except for the cowling. |
Clytie changed the tires on Larry's plane. I need to clean up the calipers and
brakes and get them installed. Someone had installed a flexible brake line
going to the caliper. Problem is, the way it's installed, there is a 4 inch
loop of hose sticking above the caliper. Now I know why the wheel fairings
weren't installed; they wouldn't fit.
Talked to Dave, the cowling should be done Wednesday or Thursday. This should
be fun.
Message 6
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| Subject: | Engine "THRUST" angle |
Gary said:
Not sure how Ned's cowling got so much down angle. Unless the plane I used
as a mock up was wrong.
Since I didn't have Ned's plane to do the initial fitting (he wanted it done
in a week),
Ned answers:
If the plane you use for mock ups has the engine aligned with the planes ori
ginal factory cowl then that plane should have it's engine in proper alignme
nt.
I would have liked to have the plane ready 4 1/2 weeks later in time to part
icipate in this years SARL racing which started April 17.
My plane came to your shop March 12 with the spinner down and to the right i
n reference to the original factory cowl. It left your shop six plus weeks l
ater with your cowl temporarily aligned with the spinner that was in the sam
e misaligned down to right position.
I say temporarily because when the screws are loosened on the side of my jag
cowl there is a lot of play so that one must continually hold the cowl in a
lignment with the spinner as the screws are tightened. The loose screw holes
have the result of having no way to know where "center" is and requires the
factory cowl to be reinstalled to check for proper engine alignment.
Gary said:
Ned had stated to me that his plane wanted to go to the (right? or was it le
ft?) when he got it. He said it didn't fly straight at any rate. My plane h
as no trim tabs and flies straight with the same cowling. To me, that is in
teresting! Does the prop have that much of an effect? Could it be the 3-bl
ade prop?
Questions for Ned
(1) What were the shims count in your final set-up? I forget.
(2) What are they after the alignment?
(3) How did you align your engine? Really. Did you get another cowling and
install it then align the engine to that?
(4) If not, What was your procedure?
Ned answer:
My plane pulled to the right with neutral trim tabs but flew straight with t
rim tabs adjusted counter.
Now with the engine aligned to the original factory cowl it flies straight w
ith neutral trim tabs
Yes I removed the Jag cowl and some baffles and reinstalled the factory cowl
and aligned the spinner to the nose bowl by simply tightening the upper lef
t mount to the proper torque. I found that bolt had no threads showing thru t
he nut and realized this occurred when the local A&P installed the short sta
ck power flow
I can't make out how many shims for sure are in there but I think only one p
er. It's just as it came from the factory
Your Fellow Grumman Enthusiast
Just a bit less enthused
Ned
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