|
Here in Dave Nelson`s own words, How the STRONG VELOCITY PITCH TRIM came about.
"Here's the article. I've submitted it to the Central States newsletter as well (Terry
Schubert):
Adaptation of Strong Pitch Trim system to my Velocity!
Working with Alex Strong, I have installed
a totally new (and very nice)pitch trim system in my Std-RG Velocity.
I was driven to do this due to the following sequence of events.... I started with the “per
plans” pitch trim system (with the servo on top of the canard driving the composite spring, which was attached to the
elevator tourque tube). This worked OK,but I was never really keen on the overall installation.
When I did a significant panel upgrade, I no longer had the space required behind the radio stack
to keep the standard pitch trim spring configuration.
To make things fit, I inverted the spring... Which seemed like it should work...
But in fact was
very marginal.
The problem was that I didn’t have enough trim authority - in particular pitch up authority
at low speeds (i.e., an
ILS approach with a passenger required continuous back pressure on the stick... Not good!).
So, I searched for a solution.
Several neighbors are building Cozy MKIVs and are installing the pitch trim system designed
and sold by Alex Strong.
In researching that solution, I found that this system is the most popular pitch trim system out there
for Longezes and Cozys. It is well engineered, has a solid performance track record in the field, and is priced attractively.
Finding
a location for the standard Strong pitch trim system in my Velocity, however, became problematic. There is not enough
space in my installation to mount it on the fuselage side (as is recommended in Cozys
and Longs). It’s also
too long to fit within the center section console in my aircraft. After much effort, I determined it just wasn’t
going to work
and I contacted Alex.
Alex was GREAT to work with. He quickly understood my dilemma, and together
we began to brainstorm solutions.
What we came up with was a modified Strong pitch trim system, mounted per the drawing (essentially,
it mounts in the center section console between a hard point at the rear and the bottom of the control stick). Movement
is accommodated via a rod end attach point from the rear of the servo to the hard point. Clearance is
provided from
the speed brake servo by offsetting the mounting point of the
pitch trim servo slightly. Clearance of the “nose”
of the servo spring assembly and the center section console is enough to provide full aileron travel.
If you’re
having trouble with the per-plans installation, if you just don’t want to sacrifice space behind the radio stack, or
if you’re just
uncomfortable with the composite spring setup, you might want to take a look at this system.
Feel free to write or call with questions."
Dave
|
| CONTROL STICK TO PITCH TRIM ADAPTER. |
|
| MOTOR MOUNT |
|
| SPRING & SHUTTLE DETAIL ( SPRING COVER NOT SHOWN FOR CLARITY ) |
|
| Shuttle & Tube supporting 180# |
How the Strong VELOCITY Pitch Trim works
Power is supplied by a 12VDC motor through a planetary gearbox with an output of 150 RPM and adjustable to
a max of 44 inch pounds of torque.
Rotary motion is translated to linear action by a 5/16”-24 lead screw press fitted to the motor shaft
and secured with a roll pin. The lead screw is threaded in to an MSD(lubricant) filled nylon nut which is pressed into the
over ride tube.
An MSD nylon shuttle is located between matched springs within the tube. The other end of the tube is sealed
with a nylon plug. Both ends of the tube are rolled for security bolted and safety wired..
A control stick adapter is fitted to the shuttle and bolted in place.A common bolt secures the Pitch Trim
to the control stick and the elevator torque tube.
In flight after you set the trim you can over ride the set trim by simply pushing or pulling the control
stick. When you release the control stick the set trim will be restored.
An elevator trim indicator was thought to be neccessary when I designed the original Pitch Trim for the EZs.
However since the elevator is visible from the cockpit and you only have to set the Trim for take off, then you only trim
to remove pressure from the control stick the idea was not incorporated.
PILOT REPORTS
"I finally have news to report. April. 9/04
I've been flying for about the last 1 1/2 to 2 weeks - about 3 hours so far. And,
so far the pitch trim system has been flawless! Exactly what I've been hoping for. My only hold up in providing
you data has been that I still haven't had the opportunity to shoot any approaches - which in my mind is the definative test
of a pitch trim system. The spring tension seems just right - plenty of authority in both directions, even at low speeds
(which is where I've always suffered). There appears to be plenty of travel (i.e., full trim authority is available
at high speeds as well as low). I'd like to put a big fat guy in the front to check out forward CG trim authority, but
based on the flying I've done with medium weight guys I don't think there will be any trouble.
Once I've shot a few approaches, I'll write up a full documentation of the installation for you
to use as you wish. If it turns out good enough, I'll send a copy to Terry Schubert (Central States) and to the Velocity
Views newsletter. So - I'll be in touch. But, at this point, I'm feeling awfully good about this system!"
Dave
Oct. 5/04
Dave wrote,
"This system has been working GREAT for me! After extensive testing
followed by approximately 50 hours of flight
time, I’m completely
satisfied. The system allows excellent pitch authority in both the fore
and aft directions,
and operationally allows excellent trim preciseness."
Dave
"Yes, I've been flying mine for about a year and a half (maybe 150 hours), >> and I love it. It
gives me good pitch control and freed up the space > where >> the old pitch trim spring was (for my installation
anyway). You can > contact >> me directly if you want more info." July 17, 2005"Dave Nelson" davenali@charter.net
Check out Brett Ferrells website Chap.12.1 Elevators detailing his installation of the Strong Pitch Trim (With
photos)
FAQ
Q- When you move the control stick fore & aft there appears to be a lifting motion, will these cause the
shuttle to pop out?
A- If the motor mount was mounted regidly to the keel this could be a problem. However the motor is attached
to a Rod end and is free to move with the action of the stick. The only weight that is exerted is the weight of the Pitch
Trim tube. This assembly has been tested to support 180# with no indication of any distortion or tendency to pop out. See
picture of this test in photo section.
PRICE & OPTIONS:
Complete STRONG VELOCITY PITCH TRIM
$ 280.00 ( USD) Post paid within the USA & its territories. This is the modified
unit which has a mounting dim. of 13.5 inches.
If you have 21 inches clear aft of the control stick you may be able to use the Standard model $230.00 (USD)
Click here for PWM Speed Control.
Reversing Relay if Pitch Trim is activated by Hat SWitches.
$35.00 with Trim purchase.
$40.00 if sold separately.
Panel Switch alternative to Hat Switch.
$25.00 with Trim Purchase.
$30.00 if sold separately.
We accept, Cash, checks, Money orders and CC through PAYPAL;
Make payment to;
Alex Strong
Po Box 1316
Yermo, CA.
92398-1316
E-Mail me!
Phone # (760) 447-2602
|
