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Master Series Socket Block fauilure

socket block Master series vest vest modification

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#1 Geoff Owen

Geoff Owen


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Posted 11 May 2014 - 01:37 AM

From Geoff Owen,


Hi forum Steadicamers,

I haven’t done much posting on the site, so forgive any of my shortfalls. Perhaps it's worth putting this post into the general discussion as well, moderators please advise on this.


Last year I had an equipment failure that I thought I should share with everyone just in-case the same happens to one of you, or better still,  you can avoid it happening at all.


Perhaps this topic has been covered in the past and I’m simply unaware of it. But unless you have had the failure that I describe below you won‘t even think to look through the archives for it, at least I didn’t. So it serves as a reminder for us to check for the fault.


This particular failure was on my Master Series Vest, the Socket block assembly, specifically the “Lock-off Bolt” that secures the whole assembly to the Spar of the Vest. This single ¼ inch bolt snapped in the middle of a “cross-over” manoeuvre and consequently the rig hit the floor. This happened around “take 20”.


After inspection, I think I've worked out the reason for the failure. The Stainless Steel block that the “Lock-off Bolt” screws into had become bent. This allowed the bolt to be bent back and forth to the point of failure from fatigue. This particular set-up required 3 cross-over’s in a 15 second take, so the bolt got bent 6 times every 15 seconds, so after 20 takes the bolt had been bent at least 120 times, in my mind it’s no wonder that it snapped.


Also to clarify that this vest was made about 1996, so it’s 18 years old and the bolt that snapped was the original Lock-off bolt as is the stainless steel block. So I’m not blaming poor workmanship or sub-standard components, to get 18 years of service without breaking is great, this is simply a point of maintenance that users of old vests should be aware, if you use one of these old vests it’s worth checking before a failure possibly happens to you too.


How many of us who use these Master Series Vests, perhaps other vests have the same design, are depending on just a single ¼ inch bolt holding up our Rigs and cameras and are in potential danger of fatigue and failure. I’m un-educated in the methods that are employed on the newer vests from all the manufacturers today, but if any of manufacturers methods use a single bolt to lock the rig to the operator, then serious thought should be put in to ensure that it doesn’t fail.   


I have seen that some Master Series Vest wearers have made modifications in this area but I’m not sure if these modifications have been done simply because the Socket Block Assembly kept slipping down the spar and so they have put in a screw to keep it in place. The Socket Block slipping on the Vest Spar may be due to the Stainless Steel Block being bent, mine never slipped but I did have to tighten the lock-off considerably to stop it from slipping, so you too may be only a cross-over or two away from disaster.


My solution was to have an engineer straighten the Stainless Steel Block and tap threaded holes into the top and bottom of this block. Drilling two matching holes through the main front plate of the assembly. So now I have two ¼ inch bolts that connect the assembly to the vest, (see photos). The height adjustment lock-off now works better then ever before. However, there is a drawback with this modification, it’s more time consuming if you want to disenguage the Socket Block to change operating sides.


I hope that this posting helps just one operator to not suffer an embarrassing and expensive situation.


Geoff Owen

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#2 joe mcnally

joe mcnally

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Posted 11 May 2014 - 03:47 AM

Thank you Geoff

very informative post.

I've had problems in the past with the two little countersunk screws that hold the wedge guide in place. they have bent meaning the front plate slips it at least gives you a little warning things are not right . Ill check the area you mention right now and even consider the modification soon. BTW I always understood the wedge was titanium ?

All best and thanks for sharing


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