Raygear Face Shield and Woodturning PPE

Discussion in 'Woodturning Health & Safety' started by Rob Wallace, Sep 5, 2014.

  1. Bill Boehme

    Bill Boehme Administrator Staff Member

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    As an engineer with a background in kinetic energy, it has been my experience from commenting on this several times in the past is that folks don't want to hear somebody saying that their favorite piece of safety gear doesn't provide the degree of protection that they would like to believe that it does. What seems so obvious to me may not necessarily seem that way to most people. Read the information that comes with the 3M Tekk Professional Faceshield and we discover that it also requires the user to wear safety goggles or glasses with side shields ... at least in an industrial environment. We also see that the type of protection it provides is against small high speed particles that have very low kinetic energy. From actual experience most of us would also say that it does an good job against flying bark chunks when we start roughing out a piece of log. There's something about the chunks of bark that most of us haven't considered -- at that stage of the turning process, we are probably running the lathe at a fairly slow speed. The kinetic energy contained in a moving object is the product of mass and velocity squared (in other words, KE = m · v[SUP]2[/SUP], in vector notation). Two examples in layman's terms:
    • Doubling the mass while keeping the velocity constant doubles the kinetic energy. This sounds intuitive to most of us.
    • Doubling the velocity while keeping the mass constant quadruples the kinetic energy. This is the part that may come as a surprise to most of us. Suppose that we start roughing out our split log at 300 RPM and pieces of bark, wood, bugs, and sap are impacting the faceshield and we are very happy that the faceshield is doing its job. Suppose that we get in a hurry and decide to crank the speed up to 600 RPM. Now everything flying at us has four times as much kinetic energy. We might feel like we got caught in a hailstorm. But, what if we got in a really big hurry and cranked the speed up to 1200 RPM? Well, now each chunk of bark and other stuff has sixteen times as much kinetic energy as when we were turning at 300 RPM. Those little pieces of bark are probably starting to hurt. Will it be enough to knock your faceshield cattywompus if not completely off? I'll let somebody else try it. Well, heck 1200 RPM isn't too fast ... suppose that we are hell bent for leather to finish this turning and crank the speed up to 2400 RPM? Good idea, while ducking for cover, I'll just mention that each chunk of bark now has sixty-four times as much energy as when turning at 300 RPM.

    Al mentioned getting hit [in the faceshield] by a one pound piece of wood:

    Stating the mass without mentioning velocity tells us nothing about the kinetic energy, but I would bet that even at slow velocity you are likely to get a broken nose and a nice purple bruise ... maybe even a mild concussion. Mass really does matter and, of course, velocity is the killer. If we assume that a typical piece of bark weigh about an ounce, then at 300 RPM, the piece of wood would have 16 times as much KE as the bark. At 600 RPM, the piece of wood would have sixty-four times the KE of bark at 300 RPM. At 1200 RPM, the one pound piece of wood would have 256 times as much KE as the piece of bark at 300 RPM. And, at the insane speed of 2400 RPM, the piece of wood would have 1024 times as much KE as the piece of bark at 300 RPM. Looking at big numbers doesn't give us something that we can wrap our head around (I'm speaking figuratively), but we ought to at least recognize that we're talking about lots of energy -- far in excess of what the faceshield can handle without collapsing into our face.

    I have heard some people speculate that a faceshield distributes the impact over a wider area -- maybe if our face were shaped like a faceshield -- since it isn't, our human "crumple zone" would be the nose, teeth, cheekbones, and cranium. Pieces that come flying off the lathe generally aren't nicely shaped and smooth like the things that we turn -- they are usually jagged and have sharp edges. I like Odie's solution, but in any case, our heads wind up absorbing the energy of an impact. The nice thing about Odie's solution is that it has some mass and stiff cushioning that has the effect of distributing the total energy over a longer period of time. By spreading the energy out over a longer time, it is equivalent to a lower impulse of energy.

    I was turning a very large mesquite bowl about 16 inches in diameter when a piece that weighed about 8 ounces suddenly flew off. I think that I had about a half second of warning -- not enough time to do anything if I had been standing in the wrong place. It hit the brick wall behind me, bounced off and hit my truck about twenty feet away, flew back and bounced off the wall behind me again, and finally came to rest wedged under one of the tires of my truck. The piece had a scary resemblance to an axe head and was at least as sharp.

    I think that Rob's warning was spot on. It is very obvious that the Raygear is a horrible idea. Is the thing really certified or are they just blowing smoke? I think the latter. If the price wasn't so absurd, I would buy one just to see if it is as bad as it appears to be. I don't believe that Rob really said anything about "regular" faceshields other than implying they are much better than the Raygear and I would have to agree with that. I think that it was probably my previous post about faceshields, in general, that might have influenced your interpretation of what Rob said. So, blame me for sidetracking the discussion, but I don't think that I will apologize for opening this can of worms.

    Obviously, a better solution would be something that doesn't require us to use our heads to absorb the energy of an impact. The best solution that I have seen is the cage that comes with Powermatic lathes and that nobody uses. Maybe it is not the optimal design for the type of turning that we do (I think that the cage was probably designed with spindle turning in mind), but I am sure that something more user friendly could be designed that is anchored to the lathe and fits between the spinning wood and turner.
     
  2. Betty Scarpino

    Betty Scarpino

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    We can see that the Raygear would not protect against much except maybe a sliver flying at it. Rob's warning is spot on, but by saying don't buy Raygear, what message does that send? What should a turner use to truly be safe? The AAW okays a variety of faceshield designs for use at their symposium by demonstrators, but do those regularly-used types actually offer sufficient protection? By only going after Raygear, is that tacit approval of all other brands of faceshields we turners regularly use?

    Betty Scarpino
     
  3. Mark Mandell

    Mark Mandell

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    Seems like AAW is due for some "disclaimer" noticing, Betty, to limit reliance of users on the "recommended" face shields used at Symposia
     
  4. odie

    odie

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    Betty.......

    Some of us assumed that Rob meant the common flip-up style face shields mounted to an adjustable headband are satisfactory. He has since corrected his meaning to state he only meant that the Raygear is not satisfactory without inferring anything else was.

    The discussion progressed, based on an incorrect assumption.

    BTW: I placed an order for a riot face shield, and will attempt to mount it to my faceshield's headband. At this point, I don't know if that will work out ok, or not. I'm assuming the riot faceshield will absorb more of a blow to the facial area than the original one supplied. I see it's a bit thicker and made of polycarbonate. This is the same material that motorcycle windshields are made from, and they will hold up well to road debris and rocks........we'll see how this experiment works out.

    How about Lynne Yamaguchi's presentation? Can we see that anywhere?

    ooc
     
    Last edited: Sep 8, 2014
  5. Bill Dalton

    Bill Dalton

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    Welp, since everyone hates the Raygear, I might as well say my 2 cents worth...I have two and use one of them when doing demos with SGs. While I never use it when doing "real" turning only teaching and demos. When I saw them at the Tampa Woodworking show, I thought they were cool, but didn't like the fact that the impact absorption area is the bridge of the nose and inside of the orbital areas. I asked the guy at the booth about this and he assured me they had been tested and would not cause broken bones. I don't believe that. But I also know that most guys (including myself) demonstrating don't use anything or those stupid plastic eye protectors, so in my opinion these are better than nothing. I use (prescription) safety glasses with I wear this shield and feel it gives me better protection then just my safety glasses and shows the viewer that I do take safety seriously. I use the Bionic when I'm turning at home and safety glasses and stay out of the line of fire...well most of the time. I like the riot helmet, but I can't see using one in my shop during the summer, I think my head would melt. Oh the second one I bought covers more of the forehead, it's not very comfortable to wear.
     
    Last edited: Sep 8, 2014
  6. Betty Scarpino

    Betty Scarpino

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    It is a serious matter when an AAW Board member publicly critiques a woodturning product, singling that specific one out from all the rest (which perhaps are equally non-protective). I happen to agree with Rob's opinion about the Raygear, but if the manufacturer chooses to object to this publicly posted negative critique by an official of the AAW, are the standards the AAW has in place adequate to withstand a negative responsive from Raygear?

    Send me an email if you want a copy of Lynne's article from the journal. editorscarpino@gmail.com I don't think Lynne's talk was recorded, but you could ask her for a copy of the paper -- she might be willing to share that -- it is more comprehensive than her article in the journal.

    Betty Scarpino
     
  7. Bill Boehme

    Bill Boehme Administrator Staff Member

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    ..... uh, don't buy Raygear? I just sort of took it at face value. I stopped searching for deeper meaning as soon as I got a passing grade in English Lit. :rolleyes: That's the way we engineers are, I suppose.

    Sergio posted a picture of protective body gear although I am not so sure that it was all that effective. Seriously, don't count on anything where we depend on our body to be the shock absorber -- we can only absorb so many shocks before we've reach our saturation point. I would favor having something else be the shock absorber -- something attached to the lathe or solid earth.

    The intentions are obviously good and anything, including the Raygear, would be better than nothing for the purposes of a demo although, if demonstrating, I would be hesitant to use what I consider to be the bottom feeder of personal protective gear. It might be adequate for the particular situation, but anything that an "expert" does in a demonstration will be mimicked by at least a few turners who are there to soak up information on the ways that the pros do things. I think for starters that the AAW needs to stress what degree of protection a faceshield does provide without making any presumptuous statements based on personal experience. The trouble with testing standards is trying to make them translate into real world situations. That is an impossible task, but the latest revision was aimed at making the test results somewhat more easily translatable into real world conditions applicable to industrial users.

    Is doing a product review anything other than an assessment of the suitability of that particular product? Are we talking about a comparison of two different products or a review of one?

    Somebody left the screen door open. :D

    The one thing to keep in mind is that the motorcycle windshield is attached to the motorcycle. Polycarbonate (AKA, Lucite[SUP]®[/SUP] or polymethyl methacrylate) is pretty tough stuff and can take a severe hit without breaking. If a really large object hits the windshield, you can probably "feel" the shock even in a large heavy motorcycle. Suppose for a moment that nobody had thought of mounting a windshield to the motorcycle frame and instead windshields were attached to the rider. Sounds silly, but ... just saying ... isn't that what we are doing?
     
    Last edited: Sep 8, 2014
  8. Mark Mandell

    Mark Mandell

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    It is one thing to post a public warning about the perceived deficiency of a particular product which was clearly Rob's intent from what he posted here and on WoodCentral's turning board. Nowhere (that I saw) was he endorsing any other face shield product. It is quite another to imply that he was somehow required to write a detailed analysis of every other product currently being marketed for the same use and then impute some sort of approval for any product he didn't post a warning about. Such a position is patently absurd. His warning was for a particular product that was being marketed in a way that would foster its use well beyond its design parameters presenting a clear and present danger to potential purchaser/users. The product in question might be useful to protect the face and eyes from splattering liquids, but marketing it as an impact protective device for woodturners was grossly negligent, and the vendor should have been called out on it immediately. If tool merchants won't take the care in how they present their wares, everyone of us needs to be willing to step up (or "in") to help protect the rest of us.

    Rob is being criticized for others assumptions for which he was not responsible under any set of facts. That is improper and truly counterproductive to open channels of communication.
     
  9. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I would be interested in seeing the Raygear test report. I am wondering if much of it was qualified by similarity, a situation where a design is sufficiently similar to an existing design that actual testing can be claimed to be unnecessary. It seems to me that splash protection is very suspect given the open louvered design. From a user's perspective, how comfortable is something that sits on the nose and ears as opposed to a headband? Claiming to exceed the requirements of the testing standards is BS because the standard sets minimum performance requirements with pass/fail criteria -- in order to pass, the performance has to be better than the threshold requirement. The end result would be that the faceshield is certified to carry the ANSI Z87+ marking that it meets the requirements. There is no such thing as exceeds the requirement and making such a statement implies nothing. Does the faceshield actually have the certification mark stamped on it? Or, are they just implying .....? I don't think that their certification could withstand a challenge.
     
  10. Betty Scarpino

    Betty Scarpino

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    Okay, fair enough ... I apologize if my assumptions were improper.


    Betty Scarpino
     
  11. Sergio Villa

    Sergio Villa

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    I still believe, as in my previous post have said and the sling shot of David demonstrated, that speed is the major factor in accidents. I also believe that excessive speed is not necessary with a good tool and a good hand: it is just a matter of going slower with the tool to have the same number of rotations for unit of time. Same when one uses a table or other saw: less teeth imply slower feed of the wood given the same speed of blade rotation.
    I also believe that deflection is a major factor in reducing the impact of a flying object unless impossible bunkers are used. That is why the shape of military helmets have been changed between first and second war. Polycarbonate is the strongest transparent material known. It is used in anti projectile windows.
    Having a grid in front of the face does absolutely nothing when a small sharp piece of wood flys in between the metal grid.
    Having the possibility of working comfortably has a safety advantage over cumbersome military type of shields.
    Demonstrators that show how fast they can make a cutting pass on a bowl, usually green, should be instructed not to do so. Also because usually a green rough out must be returned and that demonstration become useless. There is a difference between teaching and a narcissistic exhibition.
    In conclusion, the first safety is the active safety, followed the passive one.
    [SUB][/SUB]
     
    Last edited: Sep 8, 2014
  12. odie

    odie

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    I would think the polycarbonate shield would be better than the original, more flexible shield, regardless whether it's attached to the user. Besides that, it would seem that some of the impact would also be absorbed by the headband. I don't consider the polycarbonate riot shield a total solution......only a little better than a standard common faceshield.

    ooc
     
  13. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Essentially no energy absorbed in the headband except perhaps in the Bionic face shield which seems to have a more substantial suspension than other faceshields (actually the energy isn't absorbed in the headband -- it just get spread out over a longer period of time). The more flexible shield is also polycarbonate. The characteristic that makes polycarbonate tough is its ability to flex without breaking under high speed impact. Having a thick rigid shield may not be as good as having a thinner more flexible shield. An instantaneous transfer of energy from a rigid shield to the wearer can be severe, but if the total energy can be spread out over time with a flexible shield, the peak energy level could be substantially reduced.

    One problem area that I see with faceshields and supporting structure is that they do not have a rigid stop for the down position. They will pivot right into your face with almost no effort at all. Is the Bionic different in this respect?
     
  14. odie

    odie

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    I'm having a hard time agreeing with your opinion, Bill......

    I believe the headband is certainly going to take up some of the impact, and a less flexible shield will be better than one that bends easily....but, regardless, I'm doing some hands on experimenting with this. It's possible I won't be able to mount the riot shield, or some other problems with the conversion.....don't know at this point. It's not an expensive experiment, in any case.

    ooc
     
  15. Andy Chen

    Andy Chen

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    Bill,

    I am not going to argue on the point of different face shields here. I just wanted to point out a technical error in your post here as quoted.

    Polycarbonate (PC) is not aka Lucite or poly (methy methacrylate). If you want to use the trade name, PC is Lexan, invented almost simultaneously by Bayer and GE (but Lexan is registered by GE). Lucite is acrylic, originally developed by Dow Chemicals. Although they look the same, they differ in chemical structure as well as physical properties. Among other properties, PC has a greater refractive index than acrylic and is much more impact and scratch resistant and that is why modern eye glasses are made of PC (so are those 5-gal water jugs and your storm widows, for its strength, not RI). Because of its impact resistance, PC is used for face shields as well.
     
  16. dbonertz

    dbonertz

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    Question for the engineer types out there. At what speed would a 5lb. 10lb 20lb 40lb blanks take flight (fly up towards the face of a person standing at a lathe). When I rough turn I would not be telling the truth if I said that I have never had a blank come off the lathe (I am out of the line of fire when roughing). These blanks weigh in the neighbor hood of 20 to 40 pounds. I rough turn from 200rpm to maybe 700rpm depending on where I am in the process, blank true-ness and etc. I have never had a blank this size take flight meaning go up. They all just dropped off the lathe and roll off somewhere (this hasn't happened in a very long time now but when I was experimenting with holding methods). If a chunk comes off from say a ring check it may fly up but I think they are well under 5lb. I guess my point is a face shield may not stop a 40lb blank but they don't take flight anyway. The conversation of face shields should stay relevant to reality so we can decide which to where for safety otherwise this conversation is useless. All bets are off if the turner is turning at excessive speeds which again isn't relative to a face shield conversation - that is a safe speed conversation. A good face shield (like bionic) does its job for the designed purpose. Nothing more nothing less. One should be worn at all times for those designed purpose incidents.
     
  17. Mark Mandell

    Mark Mandell

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    Careful with that research, Odie. Only way you'll reach valuable conclusions is with a repeatable test routine that gives the same results from flying chunks of wood off a lathe. First rule I ever learned in Kendo: "Never offer your head as a target."

    Possible to contact the Mythbusters guys and borrow their crash-test dummy? Absent that, a store manikin might work. Either way, way better than dancing in the Kill Zone
     
  18. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Thanks for the correction! Andy. Lexan is what I meant, but obviously had a senior moment.
     
  19. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Or ...... see if the high speed test track at Hollaman AFB is available. For those who aren't familiar with it, the high speed test track is the world's longest rocket powered sled. We used it for bird strike studies against aircraft canopies and radomes. The nose section of the aircraft was mounted on the sled and while it was being rocketed down the track, a specially designed cannon at the other end of the track fired a partially thawed out Tyson chicken at the approaching canopy to simulate a strike with a large bird such as a such as a goose or heron or vulture. By the time that the two met, the chicken was fully thawed. If we could convince Odie that the rocket powered sled is like an amusement park ride .... (Just working on ideas for a repeatable test structure -- assuming we could convince Odie or anybody else to do that ride more than once).
     
  20. Bill Boehme

    Bill Boehme Administrator Staff Member

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    My opinion is that a blank that comes off the lathe is more or less balanced and other than continuing to spin will more likely be a hazard from landing on you foot or hitting you in the gizzard as it rattles around on the lathe before taking off rolling and bouncing around the shop. Forty pounds on the foot would be rather painful.

    The real problem with high speed flying projectiles comes from things coming apart on the lathe -- things like hidden flaws and loose knots. I also turn at fairly low speed. For me, 1000 RPM is really high speed turning. Most of my turning is probably no faster than about 600 RPM.
     

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