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Arm Trunnions


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#1 RayLam

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Posted 30 August 2006 - 10:25 PM

Hi,

I am rebuilding my 3A arm and need to replace the arm trunnions(along with other parts). Can anybody tell me who makes them and where would I be able to get some.

Any lead is appreciated.

Ray Lam
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#2 RobVanGelder

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Posted 30 August 2006 - 11:46 PM

Rebuilding yourself? It can be done, if you are very handy with tools and a lathe (spelling?) and other machinery or have access to them.
I did it once with my own 3A arm, replaced all bearings and put fixed axis in it instead of the original trunions.
But is is not easy, a mistake can cost you a dogbone, etc.
Looking back at it, I did not have much to loose at that time and there were no other companies that but CP that could do it for a reasonable price, but nowadays there are companies really catering to this.

Having said that, if you really want to do it yourself, find the bearings ( the typeno. is printed on them) and find also the hardened steel axis rods that fit them, they come in standard length (3" I think) and fit nicely in the arms. They connect the both sides this way, making it much more sturdy and reducing the twist under load,
which damages the original trunions. All you need to make is metal caps instead of the original trunions to keep these rods in place.
The old bearings can be pushed out with appropriate equipment when you heat up the aluminium dogbone, the same for replacing with new bearings.

Success!
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#3 RonBaldwin

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Posted 31 August 2006 - 08:24 AM

Rig Engineering makes stainless ones that go all the way through the bones for support.
http://www.steadyrig.com
Trunnions and the more accesible bearings can easily be replaced one at a time. As Rob Stated, be careful.

Ron B
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#4 Juan M.Ramos SOC

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Posted 31 August 2006 - 04:04 PM

call Robert Luna,he is making new 3A arms and he has everything for rebuild your arm.

310-6214763
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#5 RayLam

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Posted 31 August 2006 - 10:58 PM

Hi,

Thank you for your advise guys.
Ron, I do have experience stripping the arm, replacing bearings and cleaning it every once in a while. It actually isn't all that hard. I do agree that you have to have the right tools and access to a machine shop. it makes a big difference after you give it a good lube job.
I can get all bearings from the local hardware store but not the trunnions. Are they special parts made by Tiffen (they look the same as the trunnions in the Master arm). "Rig Engineering" doesn't really want to sell just parts for the arm.

Are there more leads ?

Ray Lam
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#6 RonBaldwin

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Posted 01 September 2006 - 06:05 PM

good luck with the rebuild. You are correct, buying the bearings at a local shop will save you lots of money. They can get the ones in the gimbal too. I didn't know Bob Luna was making them, cool. I'm sure he will have the right parts. Rig Engineering makes them out of stainless steel for corrosion protection, and they are the same ones -- I was under the impression from Hugo at Rig that they re-newed the 3-A arm patent to manufacture the silver spring arms.

Ron B
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#7 Alec Jarnagin SOC

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Posted 01 September 2006 - 10:16 PM

Robert Luna does excellent work and is a very good fella (as are the guys at Rig Engineering). I bet he will sell you anything you need.

I believe all the patents on the 3a arm are expired and there is no way to renew them which is why it has been open season for some time.
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#8 RonBaldwin

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Posted 02 September 2006 - 01:42 AM

I was just repeating what I was told by Rig Eng. Mr Luna rebuilt my 3a arm many times and always did an excellent job -- I didn't know he was making complete arms now, I thought Rig was the only one doing it from scratch. I'd love to see one of Rob's arms.

RB
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