adjusting Master arm
Posted 21 March 2004 - 03:01 PM
Please give me your comments.
Posted 21 March 2004 - 06:45 PM
Posted 22 March 2004 - 03:20 AM
Posted 22 March 2004 - 11:43 AM
I'm know there are others here that could tell ya the history of Mr. Luna... I personally do not know his history, but I think he worked for CP (please correct me if this is wrong) But I think it boils down to that he is the man when it comes to arms
Robert Luna 323-938-5659
I too will be calling him soon.
Hope this helps
Posted 22 March 2004 - 09:33 PM
If you look at the front end of both arm sections (nearest the camera, and nearest the elbow for the lower section) where the start of the spring / cable assembly starts there is I believe a 1/4" allen key bolt right at the head of the spring. This bolt is roughly 2"-4" long, and is how the tension is ultimately released by a PROFESSIONAL TECHNICIAN when taking your arm apart.
I am far from a professional arm technician, and this is not an adjustment you want to tinker with often and certainly not in the field. It was explained to me that by releasing some of that Pre-set/coarse tension, you essentially give a little life back to the spring b/c it is not being set at it's absolutely maximum all the time.
I released about 3/4 inch of bolt (maybe 10 turns on the allen) and could easily still fly full 35mm set up, Panavision Primos, with say 3 motors, and a Kino ballast & kino tube on mattbox. I found that this release in the coarse tension gave the arm a little more feel and touch. It definately made a difference, especially when lighter loads were concerned.
But beware. As you will see, when turning the allen key you have to hold the spring so that the cables don't twist. This is quite easy when you are releasing the tension, b/c the spring naturally wants to contract (get shorter). The issue is if you want to add FULL power back to the arm it is very difficult to hold the spring while you screw the bolt back in, to make the spring come back to the bolt head. The bolt doesn't actually move, the spring travels up and down the bolt. I think the thing to use is a strap wrench to wrap around the head of the spring.
But I never had to do this (add the tension back). I think the only scenario I can imagine is if you might fly BL 4's. Thank god I haven't had to do that in about 7 yrs!!
But again, check w/ Rob Luna. He is the one who indeed headed up the arm dept. @ CP for many years.
Posted 23 March 2004 - 12:06 PM
Posted 24 March 2004 - 03:41 PM
Posted 29 March 2004 - 05:43 PM
I think it's highly unlikely that relaxing the springs when the arm is not in use will have any effect on spring life.
In the unloaded (or up) position, the springs are barely loaded; hardly stretched, especially compared to the maximum stretch, or down position.
If an extension spring does not "take a set" from OVER extension, then it will perform near constantly for ever. (Try over-extending a small and cheap extension spring from a pen. When it is over-stretched, it will instantly fail to perform.)
In normal use, the arms we use can't overstretch the springs- because the stretch is limited by the geometry of the arms and not by the load - unless, of course, something goes terribly wrong.
Other factors that affect spring life are shock loading, rapid recycling, and high temperatures, none of which are encountered in normal Steadicam operating.
"De-tuning" a Master Series/Ultra arm will affect how it behaves. Theoretically, it works "best" at the maximum spring tension, just as Model I, II, or III type arms also work best at their maximum spring tensions. Relaxing or detuning any of these arms takes it out of the "ideal" and makes for a more centered and harder ride.
With older arms and lighter-than-maximum weight cameras, it takes a lot more effort from the operator to boom all the way up or all the way down, and more damping to keep the camera exactly at one height as one walks along, steps off a curb, etc.
What Will suggests with the Master/Ultra arm, however, is a slight de-tuning that has very little effect on that arm's "ideal" performance with only a slight loss in ultimate lift capacity.
It can be really useful to "de tune" the section of the arm closest to your body, as this section has widely varying loads depending on the angle of the second section, and it also lifts more or less depending on the angle of your body. Making this section more "centered" by detuning will help to keep it from locking up or down. (Better posture will have a similar effect...).
AGAIN the WARNING: if you de-tune, be sure the wires to the springs don't get crossed, otherwise it's an expensive mess.
Last note: in adjusting the MS/Ultra arms, adjust the forearm (closest to gimbal) section first so that it carries the load both above and below horizontal. Then adjust the other section so that it follows or tracks the forearm section as you boom all the way up and down. As a test: once you get it right, lean back or worse, forward, and see what happens as you boom up and down.
Posted 29 March 2004 - 08:57 PM
Experiment...be aware of how each section booms. Like Jerry pointed out adjust the front section then the back section as a 'slave' to the front. Be aware of your posture and how that affects the angles, and boom action.
Posted 26 July 2004 - 10:17 PM
Great arm, just great. Felt like............ my Flyer arm.