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Syncronized motor control options

Discussion in 'Scenery, Props, and Rigging' started by danTt, Oct 31, 2016.

  1. BillConnerFASTC

    BillConnerFASTC Well-Known Member Premium Member

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    I just did a google search on "chain motor overhead lifting" and it doesn't really confirm that chain motors are fine for overhead lifting - implying movement over people. from CM FAQ:
    " Can a CM Lodestar be used to hang loads over people's heads?
    It is preferred that the load always be tied off (dead hung) with auxiliary chains or cable before access to the area beneath the load is permitted. As an alternative, the system may be designed such that malfunction or failure of one hoist's load bearing components does not cause load loss and/or overloading of any other hoist in the system. Note that in such a system, hoist performance and function must be monitored visually or with the use of load cells.
    However, both the CM Lodestar D8+ and CM Lodestar BGV-C1 feature a 10:1 design factor that allows them to be used for suspending loads above people without a secondary support."

    A lot of cracks there.

    PLASA here : http://www.plasa.org/nrag/load_suspension.pdf doesn't make it all so clear and limitless as your statement. In any case, your statement should be more qualified like: "A limited number of really special chain motors are sometimes acceptable for overhead lifting." At least the current literature from CM acknowledges the requirement for alloy chain, something they use to resist. http://blog.cmworks.com/understanding-the-difference-between-chain-grades-and-how-theyre-used/

    I am not so concerned the use of these by really qualified people, but the problem is - especially with the unqualified "chain motors are fine for overhead lifting" attitude, is that less than really qualified people will try it. We saw it with indoor pyro. Pyro use to not be permitted indoors then some folks - most of whom who happen to benefit form the sale and use of pyro - got a standard approved and accepted. Well, then even common john and jane doe decided if they read the standard they could do it too. And then we have 100 dead in Rhode Island.

    Its the attitude that injures and kills. There needs to be a very high bar to jump to be allowed to use chain motors for overhead lifting, with a lot of safeguards and very deep pockets behind the work so when it does go fubar, the victims are compensated.

    David - I'm not saying you shouldn't do it - but you are making it sound too easy for any high school teacher (or student) that frequents CB as well as many other unqualified individuals to believe they can do it too, and that's not safe.
     
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  2. David Bond

    David Bond Member

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    I agree and disagree, respectfully.

    I concur we need to be careful with how accessible potentially dangerous equipment (and partial information) is to unqualified or inexperienced users , especially students, but I didn't say chain hoist lifting operations were easy or without risk. To the contrary I stated that it needed to be done "properly" implying that this is not as simple as it may sound and that a further understanding is required. Hopefully this would help push your point home to the less-experienced reader; that there is a right way and a wrong way.
    The Kinesys chain hoist control systems are designed to increase safety, assist experienced professionals and electronically prevent unqualified users from making potentially dangerous errors. This completely supports the notion of improved safety and risk reduction. I don't think my attitude is one which promotes unsafe practices whatsoever. Righting off chain hoists as unsuitable to all newbies is misleading as they will see them at events and performances which surely is a mixed message and rather confusing.
    If anyone read my post and assumes that, based on that post alone (or really only a part thereof that you responded to), I have a lax attitude towards safety and it is all the training they need to have a go at multi-hoist lifts then that is the strongest argument for more regulations. I agree with you that we need to be proactive and responsible as professionals, but I don't agree that I made it sound overly simple to the point of putting lives at risk. I was arguing the point you made about chain hoists, versus winches, not being robust enough or suitable for overhead lifting and that, IMHO, is untrue. Given the number of chain hoists in operation around the world in entertainment applications, I would say they are a widely accepted means of safe lifting. The fact that there are standards and legal regulations for their design and use is a fundamental acknowledgement of this.

    On the matter of the regulations, you mentioned BGV D8, BGV D8+ and BGV C1 directives, which are not mandatory standards in the US, but we do work to these standards as required in other markets. They help people quantify what is acceptable and safe and this acknowledges chain hoists as suitable. This directive includes the controls as an integral part of the system safety. The design factor of the hoist is only a part of the directive. Other elements such as encoder reading and load cells to avoid failures as well as a specified level of E-Stop safety integrity (SIL) are all important factors. A hoist designed to be "BGV C1" , be it winch or chain hoist, cannot be "certified" on it's own and must have a suitable control system and data acquisition components to conform. More on this below for those who want further information. The ANSI standards also acknowledges chain hoists as suitable in ANSI E1.6-1 – 2012 Entertainment Technology – Powered Hoist Systems, which also includes wire rope drum winches.

    With all due respect Bill, chain hoists are suitable for overhead lifting but what that statement doesn't mean is that you don't have to read the manual or learn about their proper use. Kinesys makes winches too and don't misunderstand me, they are the right tool for some jobs.

    There are many chain hoists on the market, most of which offer BGV D8+ and C1 levels of conformity, but you mentioned CM which is a very popular and respected brand in our industry. These hoists meet strict guidelines and are proven to be robust and dependable. From the CM manual: "Each Entertainment-Lodestar Electric Hoist is built in accordance with the specifications contained herein and at the time of manufacture complied with our interpretation of applicable sections of the *American Society of Mechanical Engineers Code B30.16 “Overhead Hoists”, the National Electrical Code (ANSI/NFPA 70), the Occupational Safety and Health Act, British Health Safety Executives, TUV and CE Directive." ...*American Society of Mechanical Engineers Code B30.16 “Overhead Hoists”.

    From the Kinesys DigiHoist brochure: "Achieving BS7906-1:2001 (British Standard) and D8+ (SQ P2:2010) Compliance with the DigiHoist System.
    The DigiHoist controller may be used as part of a BS7906-1:2001 Category A system, for lifting and suspension of
    loads above people, and as part of a D8+(SQ P2:2010)system, for suspension of loads above people without the
    need of a secondary suspension. In order to achieve full conformity with the above codes of practice the following
    conditions must be respected:

    Category A and D8+ Systems
    D8+ Hoist must be compliant with DIN 56950:201 SQ P2-2010.This must include but is not necessarily limit the following:
    • Double brakes
    • Brakes must act directly to stop the load
    of statically indeterminate loads
    • Top and bottom limits are recommended
    • End of travel stops
    Safety Factor 10:1

    Category A
    Hoist must be compliant with BS7905-1:2001 and
    BS7906-1:2005 Category A.
    This must include but is not necessarily limited to the
    following:
    • Double brakes
    • Brakes must act directly to stop the load
    • Top, bottom and ultimate limits
    • End of travel stops
    • Chain container must be no more than 50% full when
    the hook is fully retracted
    Safety Factor 8:1
     
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  3. icewolf08

    icewolf08 CBMod CB Mods

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    As mentioned, TAIT does now own FTSI, and we do offer both fixed speed and variable speed synchronized chain hoists. The product is called NavHoist and they are accurate to tenths of an inch and meet certifications for overhead lifting. NavHoists are one of our major products and can be found in venues like The MET and Radio City, Disney Parks, and on almost every tour we send out. Most commonly, we sell half ton and one ton units, but if you need it, we can make them bigger.

    Of course the caveat is that to get the real control power of NavHoist, you need to run them with our Navigator control software.
     
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  4. MikeJ

    MikeJ Well-Known Member

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    @David Bond, Thanks for the info. Kinesys makes some pretty cool stuff. And don't mind @BillConnerFASTC, he usually has pretty good advice, but a lot of the top posters here have extremely fragile egos. They seem to be the big fish in this tiny pond of theater students, and feel the need to tear down any new poster, and prove that they are smarter than you.
    YEP....Googling something...that qualifies you as an expert on this forum.
     
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  5. Fountain Of Euph

    Fountain Of Euph Active Member

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    No, @BillConnerFASTC is an expert based on his experience, education and certifications, and his 2600 posts on this forum back that up. He is a consult by trade, and is under no obligation to give out his professional opinions, which he makes good money from giving to his clients, to strangers, for free, on the internet. If this is a ego trip, its a very strange and potentially costly one...

    I am student, but also a actively working professional who is here to learn from MANY MANY much more experienced professionals across the world. This is not a small pond, but a vast ocean...

    What we have here is a case of two professionals disagreeing on the safest way to go about a situation. Both have valid opinions based on there occupations and experience. Personally I have rigged chain motors for rigging over the stage under the supervision of a certified rigger, and I have found them less than stellar. This being said, my expertise is in lighting/audio/staging, and not as a rigger, and so I would take the information on this thread, filter it based on my experiences and my knowledge of the posters, and make a informed decision based on that.
     
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  6. BillConnerFASTC

    BillConnerFASTC Well-Known Member Premium Member

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    I was looking for the documents produced by the chain motor manufacturers which when I last checked a few years ago stated - in very fine print - do not use for overhead lifting. CM was last one I checked and I was curious if they had changed their instructions.

    Readers can review the profiles of the posters and check the credentials and decide for themseleves who is credible, and even contact them directly, at least the ones like me who are not anonymous.
     
  7. danTt

    danTt Well-Known Member

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    It's always interesting to me to look at the amount of items we use on a daily basis that state "Do not use for overhead lifting"--and many motors are part of this. From my research recently, I believe the magic standards to look at (and these are all european standards, I don't believe there is a US one yet), Hoists that meet the "BGV-D8" standard (which is most standard run of the mill chain motors) are not designed for lifting above people. It is expected that you will reinforce them with a secondary pick (steel to the grid maybe?) if you are going to use them in a way that will involve supporting a load above people.

    The BGV-D8+ standard makes motor requirements a bit stricter, and allows for suspension of static loads above people. It requires a double brake and places restrictions on the clutch and brake positiion and raises the "safety factor".

    For the suspension of moving loads above people, hoists are supposed to be designed to meet "BGV-C1" standards. This again raises the requirements on design factor, requires loadcell monitoring, limits, and the introduction of an "E-Stop" into the system.

    Now, something I've seen discussed in detail (and never to a definite conclusion) is what exactly "overhead lifting" is defined as. A single point lift is agreed to be overhead lifting if people are under it--but what if the system is designed in such a way that the failure of one motor does not cause the system to fail catastrophically? Is there then an appropriate amount of redundancy built into the system to allow using it without a steel backup? Is the redundancy of motors an acceptable secondary backup? That seems to be a point of debate still.

    Again, most of this comes from my recent dive into all of this information, and may or may not be entirely accurate. It's quite difficult to find definitive answers when it comes to rigging--because no one wants the responsibility when things go wrong of having provided information that led to an error. Of course, the result of this is that we instead have every theatre in the country reinventing their own rigging standards, but hopefully that starts changing.
     
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  8. BillConnerFASTC

    BillConnerFASTC Well-Known Member Premium Member

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    I feel overhead lifting is fairly clear, and while it might be possible in a court of law to convince jurors to something other than the obvious and literal meaning, it seems risky. I know that some view trim chains on a batten as not overhead lifting, because if multiple points, but the chain manufactures say it is in their opinion. So I guess you have to decide for yourself. Since I work forself and am financially liable for my actions, unlike an employee whose employer is ultimately liable, I'm probably more conservative in my choices and recommendations.

    Frankly, if the manufacturer says don't use their product in a certain way, I won't recommend contravening that.
     
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  9. MikeJ

    MikeJ Well-Known Member

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    That's fine. I understand completely people not wanting under qualified persons to get in over their heads, especially where safety is concerned. But, disputing industry standards, and calling out people who are obviously experts as "unqualified" and jumping to the unfounded conclusion that other users have a dangerous "attitude" towards rigging safety, is quite unprofessional, and does not help anyone.

    Maybe some people don't realize that posts often read as demeaning and arrogant, but a lot of posts on this forum are, and it turns people off.

    I'll leave this alone now. But if you feel like people are not using this forum as much anymore, and industry professionals and manufacturers stay away, it's because of threads like this.
     
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  10. David Bond

    David Bond Member

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    I think @danTt and @BillConnerFASTC are correct to question things when safety is involved and this forum is a great way to do so. I don't take things too personally and hope I didn't come across that way. If I was doing or saying something that was wrong I would appreciate someone informing me of it. Intelligent discussion is positive and required for us to keep our industry moving forward and avoid injuries. If the dialog stays informative and doesn't judge unfairly, "on with the show" I say and I feel lucky to have the means to respond/contribute. Hopefully anyone who reads this takes away the notion that it isn't as simple as just buying the machinery (chain hoist or winch), there are safe products available on the market, you need to do your homework, consult professionals and all of this is achievable and quite common.
     
  11. BillConnerFASTC

    BillConnerFASTC Well-Known Member Premium Member

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    I agree David. I worry about people with good intentions but too little or no actual experience feeling that they can do stuff that should be left to people with experience. Like the ETCP certifications, people talk about the exam, but I still maintain the real value is the documented experience requirement. The apprentice/journeyman system is still the best means of passing along knowledge and gaining experience. It just seems like before you fly a truss on chain motors you ought to have seen a few rigged and operating, not just try it on your own for the first time.
     
  12. David Bond

    David Bond Member

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    Yes @BillConnerFASTC , I concur. When I was in the UK I was on the National Rigging Advisory Board for the Nation Rigging Certificate program (PLASA's equivalent to the ETCP program) and that program requires practical exams as a major part of the certification. The big difference there is shorter distances and economical access to training/exam centres and assessors.
    Even with an NRC certification, a newly certified rigger is not necessarily equally proficient or knowledgeable as a world-class head rigger with years on the job.
    A driver's licence doesn't make you a pro race car driver and you are statistically more likely to have an accident within the first year or so of passing your test. Typically, a "learner's permit" requires supervision before you can drive solo. I feel practical experience and education are both prerequisites to working unsupervised in the field we operate in. Aptitude and basic math/physics knowledge also plays a huge part. Luckily there are lots of experienced pros willing to share knowledge and guide newcomers in our industry, as well as weed out those who are a danger to themselves and others. Some slip through the proverbial net of course and we should all try to limit this as much as possible.
     
  13. David Bond

    David Bond Member

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    There are ANSI standards to refer to for the US but they are not regulations as in some other countries...just to confuse the issue! : )
     
  14. BillConnerFASTC

    BillConnerFASTC Well-Known Member Premium Member

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    I sometimes wish the pros didn't make it look do easy as it seems to mislead the novice into thinking it is easy and that they can do it.
     
  15. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    How's everyone's "fragile egos" today @David Bond?
    Tooodleoo!
    Ron Hebbard.
     
    Last edited: Dec 9, 2016
  16. David Bond

    David Bond Member

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    All good here Ron. thanks for checking up on me. :)
     

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