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#1 JD Hartman

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Posted 13 January 2008 - 04:23 PM

Can anyone explain why I find a variety materials used for the "friction disc" or magic washer (Matthews term), used between the fixed and the rotating sides of a grip head? In some rentals grip heads, it's aluminum or fibre. In Avenger heads, the disc is made of a rubber like material, probably neoprene. Aluminum is the material Matthews uses, but what about Norms, American Grip, MSE, Hollywood Scene Dock, Mole-Richardson? Is one material a better choice over another? I have to replace the disc in a pile of grip arms I bought and want to make the correct raw material choice.
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#2 David Rakoczy

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Posted 13 January 2008 - 07:19 PM

[quote name='JD Hartman' date='Jan 13 2008, 03:23 PM' post='213008']
Is one material a better choice over another?

Available Lighting (a New Orleans Rental House) uses a small set of bearings... that, well, brother... you can lightly finger tighten a 4x4 into a horizontal position. They work AMAZING. This make it very very easy to walk up to the Stand and loosen it to retrieve the Flag. Effortless... The problem is is that if your Crew is not familiar with these they can easily DAMAGE them by over tightening.

I have been meaning to set up all my Stands with these 'bearings' and will contact them this week and find what they are using.

Will let you know asap.
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#3 robert duke

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Posted 14 January 2008 - 12:13 AM

The Fiber discs seem to do better for than the aluminum, cork, and the rubber. I some of each and have been switching them to fiber as I can. I can't explain the differing materials just that it is how they come.

The bearings are awsome, but fragile. My rental gear is used by a lot of no to low budgets so I refuse to use them as they will only come back damaged.
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#4 David Rakoczy

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Posted 14 January 2008 - 10:20 AM

[quote name='robert duke' date='Jan 13 2008, 11:13 PM' post='213044']
....as they will only come back damaged.


For rental, absolutely. You are right. For personal use they are amazing... like magic! I believe they are called 'tension bearings'.

Robert, do you have a lead on those? I want to order a set for my C Stands.
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#5 robert duke

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Posted 14 January 2008 - 10:27 AM

I can make a phone call to a best boy who has them on his truck (LA grips in Shreveport). I dont know directly off hand.
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#6 David Rakoczy

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Posted 14 January 2008 - 11:21 AM

[quote name='robert duke' date='Jan 14 2008, 09:27 AM' post='213082']
I can make a phone call to a best boy who has them on his truck (LA grips in Shreveport). I dont know directly off hand.


Found them. They are called 'Thrust Bearings'. You place one on each Knuckle on the Tightening Side between the Knuckle and Washer.... and man that does MAGIC! A light tightening will hold fantastic!

I ordered a bunch for my C-Stands... they are $1.35 each (about).

Here is where you can get them:

Motion Industries
504-733-5400

Thrust Bearings by Timkin # NTA-613 (for C Stands)

Order some extras so when a monster of a Grip who is unfamiliar with these, CRANKS it and crushes the Bearing, you can quickly swap it out and demonstrate how effortless securing a Flag etc... is (with Thrust Bearings).

Edited by David Rakoczy, 14 January 2008 - 11:23 AM.

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#7 JD Hartman

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Posted 14 January 2008 - 03:33 PM

With a 1000lb load rating, I don't think anyone is going to be able to damage a thrust bearing assembly by overtightening. The threads in the cast handle will probably fail before the bearing does. Without an outer shield, they will eventually fail due to contaimination.
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#8 robert duke

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Posted 14 January 2008 - 04:28 PM

It is really easy to damage thrust bearings. They are not meant for this usage so the 1000lb rating does not apply. There is a bearing race that can be crushed.
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#9 David Rakoczy

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Posted 14 January 2008 - 04:59 PM

It is really easy to damage thrust bearings. They are not meant for this usage so the 1000lb rating does not apply. There is a bearing race that can be crushed.


Robert is correct.. I wasted a set the first time I (unnecessarily) CRANKED a C Stand that had them (out of habit) . The Truck Driver threw a new one on, showed me how to use it properly and BAM... they worked great from then on. They work AMAZING!
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#10 JD Hartman

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Posted 14 January 2008 - 05:35 PM

It is really easy to damage thrust bearings. They are not meant for this usage so the 1000lb rating does not apply. There is a bearing race that can be crushed.


Sorry, I don't understand your statement. Radial bearing support a load that is perpendicular to the axis of rotation, thrust bearing support loads parallel with axis of rotation. Isn't this is the case with a grip head? The handle is applying a compressive force to the two halves? The bearing is reducing the friction between the fixed and movable portions. How is a human going to apply more than 1000lbs of compressive force, deform or brinnel the rollers or thrust washer?
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#11 David Rakoczy

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Posted 14 January 2008 - 05:55 PM

Sorry, I don't understand your statement. Radial bearing support a load that is perpendicular to the axis of rotation, thrust bearing support loads parallel with axis of rotation. Isn't this is the case with a grip head? The handle is applying a compressive force to the two halves? The bearing is reducing the friction between the fixed and movable portions. How is a human going to apply more than 1000lbs of compressive force, deform or brinnel the rollers or thrust washer?



mmmm... I am not a scientist or mechanical engineer.

All I know is they cost a little over a buck a piece... and one on each Gobo does wonders! I used them... fell in love with them... and ordered a bag full for my personal C-Stands.

Try them yourself... using them is believing.

I am amazed I never saw these used this way in my 22 plus years in Hollywood.

Edited by David Rakoczy, 14 January 2008 - 05:56 PM.

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#12 JD Hartman

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Posted 14 January 2008 - 06:14 PM

I'm not disagreeing with you Dave. The fact that I've found them on Matthews and Avenger heads confirms their usefulnes. I just don't understand or agree with the statement made that they are not meant for this application. I would like to see them enclosed by an floating outer shell to keep contaminants out of the races. But the alternative is cheap enough, just replace them when they get stiff.
l have to gather up all the examples I can find and bring them into a bearing house for some "Over the counter advice". I'll post my findings.
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Glidecam

Metropolis Post

rebotnix Technologies

The Slider

Broadcast Solutions Inc

Gamma Ray Digital Inc

Paralinx LLC

Opal

CineTape

Technodolly

CineLab

Ritter Battery

Tai Audio

Aerial Filmworks

Visual Products

Wooden Camera