Jump to content

Dynamic Balance


Jerry Holway

Recommended Posts

Hello Alec,

 

you are totaly understanding right (although my bad english and very hard to explain).

 

i have tried it without any wire or anything that could move. just one battery, monitor and a camera. sometimes you think you can hear something (although all is fixed), but its very hard to verify.

 

So because we have a problem with the gimbal-fixation anyway (it is to fix with a screw, but there is a problem with the "gewinde" - thread?), we have to send it to sachtler for repair. so i think the best way will be to send the whole rig, so that they can check it.

 

i now have to go for rehearse for the sunday live-show. but it is only church, just slow. so there should be no problem B)

 

thanks

 

michael

Link to comment
Share on other sites

  • 2 weeks later...
  • Premium Members

What Alec said.

 

The only thing I can add is that some cameras in certain configurations make it wickedly difficult to keep even static balance. The old 2-piece Sony BetaCam ( pre-Beta SP days ) was particularly evil. I think it was the BVW-5 back? Very high specific c.g., especially with a brick battery on top. ( depending on the balance needs of the sled ).

 

Is it possible that the camera is too "high" in it's c.g. ?

 

Peter Abraham

New York

Link to comment
Share on other sites

  • Premium Members

One more thing that might be invisible but could influence balance is the wires inside the post. They might lean towards one side after you have tilted and don't come back to the middle, so you have to overcorrect to get them back.

specially with post that are extendable, this could happen, i think, as the wire assembly is often a lot longer then what you normally use.

 

A slight play/spacing in the gimbal fork will also introduce a shifting balance, when dutched.

A not-centered pan-bearing will also show off-balance when the rig is orientated differently.

Link to comment
Share on other sites

  • Premium Members

This sounds most likely, Rob. I'd forgotten about older gimbals that I had, that sometimes needed a tiny spring steel washer/shim to make them sit totally centered.

 

I've no idea what the tolerances are on the Artemis, having only touched it once or twice briefly at trade shows- and this isn't a cheap shot at another maker. It is just possible that some makers don't adhere to the wicked tight tolerances all around, and this might be a case in point.

 

Trust me, if this IS the problem, it will take a bit of fiddling around until one can get the small thin washers in the right combinations to make the gimbal sit totally centered in the outer yoke.

 

It's not a shimple thing to do. :D

Link to comment
Share on other sites

Hello,

 

after we have divided the whole rig and found nothing visible (the wire is very good inside, no chance for movement (i thought about this too)), we sent the rig to sachtler.

 

there they found out, that there was a non visible movement on the side-to-side modul. this only would happen in 1 to 1000 manufactured rigs. so we have the rig where the sled had this error AND the 1 of 1000 where the screw of the gimbal-fixing was broken. how we usualy say a "monday car" maybee we have an "monday-rig" ;)

 

but sachtler was very obliging in handling and very quick (sent the rig on wednesdey, they sent it back on fridiay).

 

hope now i will find my dynamic balance again :D

 

thanx

 

michael

 

btw.: has anyone a good idea of mounting video-cameras. because in the "normal" sony-plate there would be always a little chance for the camera of movement from side-to-side while tilting to the side. we always try to fix it with tape as good as possible.

Link to comment
Share on other sites

  • 6 months later...
  • Premium Members

Jerry,

Have you ever put any thought into a motorized battery adjustment to go along with the motorized top stage on the Ultra? Theoredically you could spin the rig and stand back with your two remotes and adjust while the rig is spinning to get perfect dynamic balance.

 

This would possibly throw off your static balance although my understanding of dynamic balance is that if the rig is not statically balanced you can't get dynamic balance.

 

Denny Kortze

Link to comment
Share on other sites

  • Premium Members
Jerry,

Have you ever put any thought into a motorized battery adjustment to go along with the motorized top stage on the Ultra? Theoredically you could spin the rig and stand back with your two remotes and adjust while the rig is spinning to get perfect dynamic balance.

 

This would possibly throw off your static balance although my understanding of dynamic balance is that if the rig is not statically balanced you can't get dynamic balance.

 

Denny Kortze

 

Denny -

 

At one time or another, I've thought about motorizing everything and anything that moves, pivots, slides, adjusts.... but I think I don't have the brain cells to keep track of it all (I so love the programmable "go-to" motors for just this reason...)

 

Regardless, Larry McConkey uses the remote to get closer and closer to dynamic balance, making it spin flat at a higher speed with the remote, then stopping and re-adjusting adjusting static, spinning again, adjusting static, etc. until it's in dynamic and static balance.

 

I think one is better off (rather than using 2 remotes) by using the dynamic balance spreadsheet in the "educational" mode and finding some close approximations for the battery position based on the some monitor positions and sled lengths ( or vice versa - finding monitor positions as you place the battery where you want it), setting some marks, and spin balancing from there, knowing you are very close to start.

 

In a few days, a new version of the dynamic balance spreadsheet and the instructions will be up on my site and Tiffen's - the template will be tailored to the Ultra2, but you can change the numbers to fit any sled. (I'll announce when it's up.)

 

Jerry

Link to comment
Share on other sites

  • Premium Members

A little notice, as promised.

 

The new dynamic balance spreadsheet and instructions are up on my site (www.jerryholway.com) and will soon be up on www.steadicam.com.

 

The spreadsheet formulas have not been changed, but the examples now reflect the Ultra2 components, and everything is a bit more clear.

 

The instructions have been reworked a bit more, and there's a new trick at the very end of the instructions...

 

Jerry

post-269-1177975291_thumb.jpg

Link to comment
Share on other sites

  • 5 years later...

i can see that this topic speaks about flexible rigs like ultra 1 and 2 where you can change the place of your rigs elements ..

my rig is the master elite, am not using the CRT monitor anymore .. and am using the (

CineMonitor

HD

Classic

) .

and am using a PAG batteries (old big ones ) ....

finding this rig so hard to DB .. but i know if am using a bit lighter monitor it would be better ..

last time i was flying the rig with ARRI ALEXA ... it was close to DB ..

am a newbie , the questions is :

_do i always have to put my rig to a perfect BD or being close is good ?

_i was doing a running shot with a slow drop time lik 3.5 sec ... i was loosing headroom but i maintained a good horizon ... is it good idea making a the drop time faster (as there isn't much panning involved in the shot , just a don juan running shot ) ?!

_adjusting fore and after to trim for a headroom will put the rig out of DB .. right ? as my rig is without a motorized stage ..

 

monty

Link to comment
Share on other sites

Hey Monty

 

Do I remember you from a workshop with me in England? Maybe 2008? I am pretty sure we would have covered this.

DB is a help not a goal in itself. It will make it easier for you to shoot however may be difficult in the sled/monitor combination you have. Lighter batteries like modern Li-Ion will help, extending the monitor mount and maybe putting a battery on the back of the monitor if you can.

 

It's personal preference but I would not change the drop time for that running shot especially if you don't have a problem with the horizon but do use the arm height and fore and aft trim to keep the headroom. Unless you are panning, good DB will make little difference.

 

Robin

  • Upvote 1
Link to comment
Share on other sites

  • 2 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...