Premium Members Eric Fletcher S.O.C. Posted May 16, 2011 Premium Members Report Share Posted May 16, 2011 Bottom line is that the vertical bob is friction, call it isoelastic if you want but it's still friction. I know of several operators who have changed to a PRO arm in the last few years due to bob issues.... Quote Link to comment Share on other sites More sharing options...
Premium Members RonBaldwin Posted May 16, 2011 Premium Members Report Share Posted May 16, 2011 Mmm. Stiction. I tried a G70 arm once and did not experience this, but it wasn't a slow move and I had dialed out most of the iso-elasticity like you did so it felt similar to my pro arm. I have heard of several having this bouncing issue. Some could dial it out, others couldn't. Quote Link to comment Share on other sites More sharing options...
Premium Members Matteo Quagliano Posted May 16, 2011 Premium Members Report Share Posted May 16, 2011 so now my question is. does other ISO arm, like the master mentioned in the thread, behave the same? Thanks Erik for replying Quote Link to comment Share on other sites More sharing options...
Premium Members Eric Fletcher S.O.C. Posted May 16, 2011 Premium Members Report Share Posted May 16, 2011 so now my question is. does other ISO arm, like the master mentioned in the thread, behave the same? Thanks Erik for replying Yes Isoelasticy is a combo of Friction and Stiction Quote Link to comment Share on other sites More sharing options...
Premium Members Jerry Holway Posted May 17, 2011 Premium Members Report Share Posted May 17, 2011 Yes Isoelasticy is a combo of Friction and Stiction No, sorry, that is not the definition isoelasticity. Isoelasticity is a word coined by Garrett to describe how well the arm's SPRINGS behave in lifting a load over the arm's boom range. An isoelastic arm is one that does not take much more effort to boom up or down, and consequentl;y is less reactrive to vertical changes by the operator - walking or stepping up on a curve. A less or non-isoelastic arm is one that takes a lot of effort to boom up or down from its float point, and consequently it seeks its float point strongly and is more reactive to vertical changes. Friction and stiction are separate (but very important) issues, often confused with isoelasticity, because 1) the original Master Series arms had bad bearings and were fricitonal. The combination of iso and friction made it easy for the arm to stay up or down, but it was not a good thing, and CP went through two changes in trunions and bearings before they got the friction and stiction down to an acceptable level. The first Flyer arms were so friction-free that a couple of more frictional bearings were added to stop the floppiness, so a perfectly friction free arm (especially when it is iso) is not the best thing either. The G-series arms have controlled isoelasticity - either for user preference or because the geometry of the arm changes as lift is increased - a consequence of using a single spring over a such a wide range of lift. The PRO arm remains very isoelastic over its large range of lift by changing out the springs - a different design approach that works very well. The PRO am also has very little friction and stiction. Good things, and a good arm. If a G-series or any other arm develops friction, it will show up as a vertical bounce. Because the arm does seek its float point very strongly, it takes more effort to overcome the stiction/friction, and the bounce is more pronounced. Turning down the iso helps (as suggested above) but the real cure is cleaning or replacing the sticky bearings. Jerry Quote Link to comment Share on other sites More sharing options...
Premium Members Eric Fletcher S.O.C. Posted May 17, 2011 Premium Members Report Share Posted May 17, 2011 If a G-series or any other arm develops friction, it will show up as a vertical bounce. Because the arm does seek its float point very strongly, it takes more effort to overcome the stiction/friction, and the bounce is more pronounced. Turning down the iso helps (as suggested above) but the real cure is cleaning or replacing the sticky bearings. Not certain you want to open this can of worms Jerry. You want zero friction in any spring dampened system, any friction, stiction or hysteresis will will require a higher spring rate (and subsequent natural frequency) then you need in order to damp out the payloads natural frequency. That higher rate WILL be seen as bob when you have a motion that does not provided enough energy to overcome the excessive spring rate and friction/stiction/hysteresis Quote Link to comment Share on other sites More sharing options...
Premium Members Matteo Quagliano Posted July 19, 2011 Premium Members Report Share Posted July 19, 2011 dont' want to open any kind of can of worms but I would like to expose my new thoughts. finally I found THE way (for me) to solve my problem with this arm. I put some WD40 on the arm and this helped a lot but the real improvement comes from a little change in the vest that caused a great change in my operating. I just put the front rail of the socket block in front of the pad instead of behind it. Chris Fawcett suggested me this and it really changed completely my operating in very slow walks. don't know if it's dangerous to have the weight outside but at least now I can have the socket block where I like it to be, way under the allowed position in the previous configuration, giving less amplification to my movement. Don't know why LX vest is build like this... quite strange since this mod can give a great improvement in the associated (G50) arm behavior (don't ask me why technically I just can feel it) thoughts? maqu Quote Link to comment Share on other sites More sharing options...
Premium Members Fabrizio Sciarra SOC ACO Posted July 19, 2011 Premium Members Report Share Posted July 19, 2011 Isn't WD40 way too aggressive to be sprayed onto an arm? Quote Link to comment Share on other sites More sharing options...
Premium Members Matteo Quagliano Posted July 19, 2011 Premium Members Report Share Posted July 19, 2011 I hope not... what would you use? I was suggested like tthat, do you think it can create any problems on the arm? Quote Link to comment Share on other sites More sharing options...
Premium Members Sebastien Audinelle Posted July 19, 2011 Premium Members Report Share Posted July 19, 2011 I hope not... what would you use? I was suggested like tthat, do you think it can create any problems on the arm? Matteo, Check page 24 of the Steadicam Archer Manual. http://www.steadicam.com/images/content/ArcherManual%20Oct%2021.pdf Quote Link to comment Share on other sites More sharing options...
Premium Members chris fawcett Posted July 19, 2011 Premium Members Report Share Posted July 19, 2011 Don't know why LX vest is build like this... quite strange since this mod can give a great improvement in the associated (G50) arm behavior (don't ask me why technically I just can feel it) thoughts? maqu Hi Matteo, I can feel comfy to mount the arm lower, for sure, but it limits your upper boom range. The closer the block would be to your shoulder, the closer it would mimic your biological arm range, but it gets in the way when it's higher. However, as long as you can get the lens where you need it, you can mount the block wherever you want on the spar. WD40 dries up and becomes gummy. Don't worry, you haven't damaged your arm. It might just need cleaning some time in the future. Any dust that gets in will stick to the residue. Watch out for sand! Wipe off the excess with a cloth and some Q tips (that might not be an international word—the sticks you clean your ears with) now, and it will probably be fine. All the best, Chris Quote Link to comment Share on other sites More sharing options...
Premium Members Matteo Quagliano Posted July 20, 2011 Premium Members Report Share Posted July 20, 2011 Hi Chris, thanks for reassuring me. I did what you suggest on the arm, as for now it behaves really better then before but I guess soon I'll have to clean it all. Which way should I follow in doing this? As for the spar (now finally I know the english name, thanks) you're right for the boom range but since the arm's great range and the easiness in keeping it where you like the less high I can get is greatly counterbalanced by the incredible better performance the arm can reach having the socket so down close to my jewels. May be it's just me but now the bobbling is way more controllable then before, almost gone. (to be honest I have to add that the last job done was 50fps... what a pleasure seeing back your shots at that pace... wwwwoooowwww everyone said on the set... and me too... a commercial all in low mode on lady legs... great the tool you gave me to get lower and have the gimble upside down) my best maqu Quote Link to comment Share on other sites More sharing options...
Premium Members Fabrizio Sciarra SOC ACO Posted July 20, 2011 Premium Members Report Share Posted July 20, 2011 I hope not... what would you use? I was suggested like tthat, do you think it can create any problems on the arm? If I were in your shoes I would clean the arm ASAP to avoid or limit damage. Even in the Archer manual is clearly specified NOT to use WD40 at any time. Quote Link to comment Share on other sites More sharing options...
Premium Members chris fawcett Posted July 20, 2011 Premium Members Report Share Posted July 20, 2011 Maybe Fabrizio is right, but I'd be inclined just to wait and see. Probably no big deal. Anyone else? Quote Link to comment Share on other sites More sharing options...
Premium Members Matteo Quagliano Posted July 20, 2011 Premium Members Report Share Posted July 20, 2011 not at all, instead the arm works great now. and I've already worked in all the worst conditions (sea, sand, wind and salt). how would you clean it when due? thanks maqu Quote Link to comment Share on other sites More sharing options...
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