Budd Engineering

"Laser Measurement System (LMS)"

by Bob Pastorello

This is a review of a truly remarkable, innovative, and superior product used to align, measure, and troubleshoot control travel setups on aerobatic airplanes....

This Christmas, I decided to assemble the Laser Measurement System manufactured and marketed by Budd Engineering and now, Falcon Hobbies.

The LMS consists of the aluminum parts to make a very versatile, and very "user friendly" mechanical setup.  It permits easy adjustment, and very accurate adjustment of the mechanical "zero" of the scale.  The legs are independently adjustable using three plastic footed 1/4-20 adjusters.  I attached a bubble level so I'd know things were square.  I also rested a 4 oz lead weight on the base leg to provide some stability (Jerry references doing this in the very detailed, and accurate instructions for assembly and use that he provides) so things wouldn't move around while I played with it. This is really a SOLID platform, and shows a lot of forethought in the design and manufacture.  Particularly how the vertical upright with the scale interlocks with the front support foot.  Can't wobble, yet is easy to assemble.

Also included, besides the great aluminum pieces, is the heart of the system.  This is essentially a laser "pointer", although it has a 1mm dot size.  You ain't gonna find that on your make-your-own system.  The sharpness of focus, and consistency of intensity and shape further show that Jerry did his homework on this...and the quality of this laser is a significant portion of the overall expense of the unit...it would HAVE to be.  The Laser is solidly attached to a shrink-tubing coated clip (very much like a modified money-clip), so it won't mar your control surfaces.  It didn't scratch the Monokote on my Viper surfaces at all!!!         The other parts are the "intensity" switch which permits a brighter "daylight" setting for outdoor use and the battery connector.  I hooked it up to an OLD 4.8v NiCad, and it worked just dandy.  Plenty of light for the time I needed to use it.

You may be wondering by now, so what?  How does it work?  Well, here's my interpretation after using it.

1. Assemble the parts.
2. Clip the laser on the control surface.
3. Set the scale the correct distance from hinge line, and adjust it so the zero on the scale is where the laser dot lands, controls neutral.
4. Move the stick.  Full one way, then the other, and you will see the laser dot land on the EXACT location where the servo is moving the control.  Period.  (The scale is set up so that each division on it is .2 degrees.  And the dot is smaller than the distance between divisions by at LEAST 50%....you can get this as accurate as your AR self wants to be!!!)
5. Adjust the control travels, clevises, cable tensions, etc. as needed so everything is perfect.
6. Go fly an airplane that will be different than before using this device.

This shows the zero dot of the laser.  Very visible, even in my brightly lit workshop.	This is a close up of the scale, and how the divisions are arranged.

The benefits of this system are remarkable.  I'm not one of those super-duper, "feel a click" sort of fliers.  By a LONG shot.  But - I can easily identify when there is a trim problem.  Measuring the control travels on elevator halves and ailerons are the most important post-building adjustments that affect the flight performance of your aerobat.

I have to say - on my Viper - which flew very well, and which I had setup using the best measuring I could do on my bench...had a slightly weird rolling thing going on on hard pulls, and hard pushes.  I'm sure you've guessed what I'm going to tell you next...

The elevators were not aligned perfectly.  Although close, the travels were not the same side to side.  Using the LMS, I was able to make adjustments to my pull-pull setup that corrected ALL of these various issues.  How did I know?  Because I was able to leave the LMS setup, laser attached, while I made adjustments to things.  So it was VERY easy to verify exactly what was going on.  Here are a few of the things I corrected;

• Center alignment of elevator halves.  By using the LMS, and a known flat reference point, I was able to check, and adjust, the "neutral" of the elevator halves.
• Travel was asymmetric.  The left elevator had less down than it needed to match the right.  Since I use pull-pull, I adjusted the control takeoff by one turn for "more down"...it worked!
• Overall, there was a .5 degree mismatch of "up", so I adjusted that using my "Trace Rate" in the JR trans, THEN, mechanically adjusted the elevator that was giving MORE than I needed.  Easy...
• Finally, there was a tracking problem...not much of one...but enough...so adjusting cable tension on ONE elevator half fixed that.
• Rudder - had a centering problem.  Kinda thought I did, but the LMS let me SEE it.  About .4 degrees overshoot from left movements.  THAT ended up being cable tension on the RIGHT cable.  Fixed.  Done.
• Rudder had asymmetric travels, too.  Adjusted THAT with the control takeoff point, since the ATV and Trace Rate were correct for my "electrical" servo movements. ( I use LOTS of ATV, so I can get the best resolution with trims)

Overall, I have to say that it has been a LONG, LONG time since I've used a device that so accurately gave me the complete picture.  And it was easier.  Since I left everything hooked up while I was doing the tweakings, the whole process  - both elevators, and the rudder, only took about an hour.

What's the advantage of this?   I **KNOW** any flying issues are NOT control travel related.  And for me, that means I know to look elsewhere when things don't hold shape in the sequences....

Contact jerry@buddengineering.com or visit his website at www.buddengineering.com  or call him at 661-722-5669.  Be sure to tell him you read about the Laser Measurement System here!!!

    And - feel free to contact me for any additional info - but I have to warn you....it will sound like a commercial.  What a superb device!!!

Contact me - rcaerobob@cox.net 

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