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    Default Leather Vs. Plastic Vs. Kevlar Vs. Fiber Glass, The....

    Materials, not just helmets!

    Since things seem quiet around here we might as well get into this again, whith a twist.

    Lets not look at the helmets themselves since that brings in all sorts of things that dont realy have much bearing on the issue of the materials, things such as:

    - Tradition
    - Cool ness, some things Leather is Cool, or is it FOOL?
    - Prejudice against tupperware
    - personal preferance.

    Instead of the same old smack fest lets closely examine the actual materials which cover our rock filled heads, off the top of my rock pile they are:

    - Leather
    - Thermo Plastic
    - Fiber Glass
    - Kevlar Composite

    Lets examine the inherent characteristics of these materials. I kind of expect Kevlar Composite to be the top performance material, but they all have something to offer.

    Yippy, lets have fun!!!
    -Brotherhood: I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve.
    -Mistakes: It could be that the purpose of you life is to serve as a warning to others.

    -Adversity: That which does not kill me postpones the inevitable.

    -Despair: Its always darkest before it goes Pitch Black.

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    oh no LEATHERS BETTER!!! Good luck brother!

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    To get things started, From Bullard Website, they dont have Leather I guess. Oh, this also shoots down my Kevlar theory. I thought kevlar would be the winner since most other high performance helmets, IE GI/race car/etc..., are all Kevlar and such.

    -------------------------------------------------------------------

    Section 1 - Material Composition
    --------------------------------------------------------------------------------

    Thermoset Resins

    This material is the "glue" which is needed to hold glass fibers together in a composite helmet shell. Thermoset resins are a family of plastics that do not melt but chemically degrade at high temperatures. Thermoset resins are created by mixing two base materials just like epoxy glues. (Epoxy glues are thermoset resins). One of the ingredients is a catalyst when combined with the other agents and heat during molding, will solidify the mixture locking itself and the glass fibers into a rigid state. In compression molding applications, very little catalyst is used so that the liquid resin remains stable at room temperature; the heat and pressure of the molding operation initiates the chemical reaction to solidify the resin.

    High Performance Thermoplastics

    As a general rule, thermoplastic materials become softer and tougher as they get warmer, and harder and more brittle as the temperature goes down. Until relatively recently, it was possible to obtain either great heat resistance or great impact resistance, but not both in the same material.

    In recent years, new thermoplastic materials have been developed which successfully combine both heat resistance and impact resistance. Polycarbonate began this trend in the 1960s; more recent materials such as GE's Ultem (a special high impact grade developed by GE in cooperation with Bullard specifically for fire helmet applications) and Amoco's Radel now provide comparably high levels of impact resistance with heat resistance far exceeding that of polycarbonate. While the cost of these resins is very high, it is justified in certain demanding applications by their exceptional performance. As technology moves forward, these materials will continue to improve and expand in applications.

    Glass Fiber

    Thermoset resins by themselves have relatively little strength: the strength of a thermoset composite material comes primarily from the fibers of glass or other materials that are bonded together by the resin. There are three types of reinforcing fiber in common use today: Plastic materials (Kevlar, PBI) have very high strength and toughness but very low stiffness, and perform most efficiently when they are allowed to flex under load; in addition, they tend to be more affected by heat than other reinforcing fiber materials. Carbon fibers provide both strength and very high rigidity but are electrically conductive and therefore unsuitable for applications requiring high levels of electrical insulation. The third material family, glass fiber, provides the best combination of high strength, high stiffness, electrical insulation and cost of any reinforcing material in common use for fire helmet applications.

    The challenge in designing an effective composite material is getting the right mix of a good thermoset resin and high content of glass. The performance of the composite is a function of the structural strength and adhesive properties of the resin, the length of the glass fibers and the amount of glass reinforcement in the composite. By increasing the strength of the resin and/or the length of the glass fibers, it may be possible to reduce the content of glass without sacrificing performance. This may result in a product which is easier to mold and has a better surface appearance. The glass fiber is heavier than the resin so getting the right mix also creates the best potential for a lighter helmet shell. Most fire helmets today have a glass content of approximately 50%: preform molded shells tend to use a longer fiber length and a slightly lower glass content, while SMC shells use a higher content of shorter fibers.

    KEVLAR

    The following information is for clarification of questions concerning the use of Kevlar in fire helmet shells. Our justification is solely based upon NFPA standard performance criteria.


    Kevlar helmets are a member of the composite family. This means helmet shells constructed of fiberglass, kevlar and or other materials. All of these materials are held together by a resin. Without the resin as a common bond none of these materials will perform as needed in a helmet.


    The resin is the common denominator in all composite helmet shells. It also becomes the weakest link in performance qualities. This simply means that when you have reached the limits of the resins you have for all intents reached the limits of the helmet shell. Therefore, adding exotic materials such as kevlar to the matrix of a helmet shell only increases cost of the product and does nothing to enhance protection qualities of the helmet. Since protection is the true reason for wearing a fire helmet, Bullard is more concerned with providing the most useful, economical helmet possible which exceeds NFPA requirements.


    The NFPA Standard for Structural Firefighter Helmets is the only performance criteria by which all helmets are measured in the United States. To be compliant with this standard, a helmet must meet or exceed all performance tests stipulated in this document. This includes a certification by an independent third party. SGS US Testing, Inc has certified Bullard fire helmets meet and or exceed all the latest NFPA requirements.


    The purpose of the NFPA standard for fire helmets is to ensure that a minimum level of protection is met. The minimums set in this standard are so severe that they often translate into protection levels in excess of human survival. This is where you must ask the question, if the minimums are in excess of survival, why would you need to enhance their performance? To have a better looking corpse? Any helmet that meets the latest revision of the NFPA standard will outlive any firefighter wearing it.

    Molding Processes

    The most common processes for molding helmet shells are compression and injection. Compression molding is used for composite materials, and injection is used fir thermoplastics. Tooling costs and production rates are similar between these two processes, the composites being slightly slower and in some cases slightly less costly to tool.

    A number of other molding processes exist for composites, although most are not suited to either the high production volumes or the high service temperatures associated with fire helmets. These include 'Hand Layup' and Resin Transfer Molding (RTM). In both of these cases, the resin is cured at room temperature and without the application of pressure. Tooling costs are extremely low for these proceses: in many cases the tools themselves can be made of plastic materials. A number of practical problems result, however: the resin must be fully catalyzed, making it unstable once it has been mixed; even so, without heat and pressure, it can take up to ten times as long to solidify. More significantly, however, the low-pressure process produces a lower density finished part which may have pockets of trapped air, surface pinholes and lower heat resistance than a part produced by compression molding.

    Injection Molding

    Injection molding is used for thermoplastics. The molds comparable in cost and complexity to the most sophisticated composite/compression molds and require more sophisticated equipment for processing. However, the quality, consistency, and speed for manufacturing are greatly improved.

    Plastics used in injection molding processes come in small pellets, about the size of grains of rice. The material can be and often is pigmented with the final color of the end product. In this form, the plastic pellets are funneled into the molding machine screw. This screw looks like a giant drill bit that feeds the pellets in a tumbling action toward the steel mold. Heating elements are wrapped around the outside walls of the screw housing to heat and liquefy the plastic. As the now liquid plastic reaches the steel mold it pools at the front of the screw in the exact amount needed to fill the mold. The end of the screw becomes a ram, which injects this proportioned liquid through a small inlet hole called the sprue, and fills the mold cavity. The ram end of the screw creates a plug to hold the plastic in the mold until it solidifies. The mold separates and the finished part is ejected. The entire molding process of a single helmet shell as described takes about 1 minute.

    The injection-molding machine used to process the hybrid plastics in todays fire helmet shells requires capabilities of developing temperatures in excess of 700F and pressures up to 400 tons.

    The specialized thermoplastics used in these processes require very tight tolerances in moisture content, heat consistency and material composition to insure repeatable molding process. Any variance can create a product that looks good but may actually be useless.

    Compression Molding

    In appearance, a composite compression mold resembles a plastic injection mold. However a compression mold receives raw material by separating the two halves of the mold and hand placing the material in the mold and closing the mold on the material. Through compression, the material fills the mold cavity.

    Composite material used in compression molding comes in many forms. Common forms of Compression Molding include BMC, SMC, and Preform molding. The time required to produce a part by Compression Molding is typically about two minutes.

    BMC Molding

    Bulk Molding Compound (BMC) is a material made by mixing a thermoset resin and fiberglass in a manner much like an industrial grade bread dough mixer. This process and materials are commonly used for making products such as auto headlight housings.

    Preform Molding

    Preform composites are created by building a "nest" of glass fiber approximating the finished shape of the product and laying it in the mold cavity. A proportioned amount of thermoset resin is poured over this fiberglass nest and the mold closes to force the resin around all of the glass fibers filling the mold. The resin can be pigmented to match the finished part color. Many fire helmet shells are molded with this process.

    SMC Molding

    Sheet Molding Compound (SMC) is made by a process of laying a giant sheet of liquid resin and chopping glass fiber over this sheet. This process runs the mixture through a series of rollers squeezing the two materials together in preparation for use in a mold. These sheets are than cut into specific weighted amounts and laid into a mold. The mold closes and compresses this material filling the mold cavity. Several fire helmet shells are molded with this SMC process. The resin used in this process can also be pigmented with the finished part color.

    RTM Molding

    Resin Transfer Molding (RTM) is a process that uses a preform of glass fiber as above, but injects catalyzed resin into the mold after it has closed. The process takes place at room temperature, and there is no pressure involved beyond that created by the pump which injects the resin. Due to the low temperature and pressure, it can take up to twenty minutes to produce a part by resin Transfer Molding. The pressure is also often insufficient to force all of the air out of the mold, resulting in porous regions at the surface or in the interior of the part.
    -Brotherhood: I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve.
    -Mistakes: It could be that the purpose of you life is to serve as a warning to others.

    -Adversity: That which does not kill me postpones the inevitable.

    -Despair: Its always darkest before it goes Pitch Black.

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    Default More From Bullard

    Section 2 - Myths
    --------------------------------------------------------------------------------

    The most commonly asked question regarding fire helmet materials is which makes the 'best' helmet. Unfortunately, there is no simple answer to that question. The high heat resistance of modern thermoplastic materials has effectively eliminated what had previously been the primary advantage of thermoset composites, namely their inability to melt. The temperatures required to melt Ultem and Radel are so high as to cause chemical degradation of most thermoset resins. At the same time, these new materials exhibit the high quality of surface finish and the resilience and impact resistance that has long been associated with thermoplastics.

    Composite materials still offer benefits, however: their cross-linked molecular structure, in addition to preventing melting, also gives these materials an exceptional resistance to chemical attack, while their traditional inferiority in impact resistance is being increasingly offset by new developments in high strength resins and reinforcements.

    Many commonly held beliefs are the result of experience with products in the field. While certainly valid, these experiences in many cases have occurred decades ago and may not accurately represent the nature of modern materials and products. Below, you will find some of the more common beliefs as well as the "rest of the story".


    Composites

    True or False: Composite (fiberglass) helmets do not degrade under conditions that affect thermoplastic helmets.

    False: In fact, fiberglass will often degrade more rapidly under similar conditions. The thermoset resin, which holds the glass fibers together, degrades when exposed to extreme temperatures. Each exposure to high heat attacks and weakens the molecular structure of the resin. Lower temperatures can also degrade the resin but over a much longer period of time. Ultraviolet (UV) exposure from sunlight has a similar effect on these resins. An example of how this degradation takes place can be seen in corrugated fiberglass paneling used in deck roofs. Over time, the sun will bake the resin out of the fiberglass, leaving glass fibers exposed and degrading both the strength and appearance of the material. High heat exposures are acceleration of this type of degradation.

    True or False: Composites remain rigid when exposed to high heat conditions that soften thermoplastic materials.

    False: Even though they do not melt, thermoset resins used in composite do soften significantly at high temperatures such as those involved in structural firefighting service. In addition, unlike their plastic cousins, thermoset resins are not well suited to being repeatedly heated to the softening point and re-cooled. Each heat exposure weakens the resin from its original state. Thermoplastic materials, being made into products by a process of melting and re-cooling, are designed to accept this re-heating.

    Thermoplastics

    True or False: Thermoplastic helmets cannot stand up to the heat of normal firefighting activities.

    False: Manufacturers, such as General Electric (GE), have developed specialized high performance plastics that perform at temperatures exceeding 500 F (260 C). These new plastics offer the well-known durability that comes with plastic and endure heat as well as many composite materials.

    True or False: Thermoplastic helmets will not withstand chemical exposure.

    Partly False: The new breeds of plastics used today are extremely resistant to most chemicals. There are, however, some chemical solvents, which may be more harmful to thermoplastic helmet shells than to composites. The most chemical sensitive part of any fire helmet assembly is the faceshield or goggle lens. If you are experiencing a high rate of non-impact related cracking in faceshields or goggle lenses in service, you may be working in a chemical environment in which a composite shell would provide better service than a thermoplastic.

    Actual Firefighting Temperatures

    Ask 100 firefighters what temperatures they typically experience during actual firefighting and you will get 100 different answers. Most believe that they spend large periods of time in temperatures in excess of 350F. Although there are short periods of time when firefighting exposures exceed these temperatures, the majority of firefighting is done in temperatures less than 300F. In fact, a larger portion of time is in temperatures below 250F.

    Studies in controlled fire training exercises have demonstrated that firefighters, on their knees, will enter rooms that involve pallet fires with temperatures around 250 at approximately 4 above the floor. Heat stratifies and quickly escalates to temperatures from 500-1000F above the 6 level. Firefighters are trained to stay low to avoid exposure to these extreme and deadly heat levels. Unlike real fire exposures, firefighters in training exercises will often expose themselves to high levels of heat for long periods of time to experience the different characteristics of these fires. In real fire environments, firefighters are trained to change the environment and lower the heat exposure with use of agents such as water, foam and/or positive pressure ventilation. Introducing these agents into a fire environment has proven to reduce temperatures in seconds by 200-300F.

    Many components worn for protection have limited performance life when exposed to temperatures above 500F. NFPA Standards have established that these components must endure 500F for 5 minutes; however, it is understood that endurance does not mean that these components survive without sustaining damage. Their endurance is to insure that the firefighter is given that window of opportunity to escape. Equipment exposed to this level of heat and time will most often need to be retired from additional service.

    Product Life

    How long should a helmet last in the field: 3, 4, 5, 10 years? The answer is yes. Depending on the level of activity, exposures, and preventative maintenance, a helmet's life could be as short as one time use or as long as 10+ years. The primary issue is how well the helmet is maintained and what the helmet has been subjected to while in service.

    Any fire helmet that was involved in direct flame contact or that experienced an impact from a falling object should be removed from service. This could happen the first time the helmet was put into service. A helmet used by an active fire training officer with several months each year of live fire exposure could well reach its full and useful life in 1-2 years. The helmet would not be the only item that would exceed useful life in that time under those conditions. Coats and trousers would also be subject to retirement. Helmets in a rural volunteer department that did not see live fire but once or twice a year may easily last 10 years.
    -Brotherhood: I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve.
    -Mistakes: It could be that the purpose of you life is to serve as a warning to others.

    -Adversity: That which does not kill me postpones the inevitable.

    -Despair: Its always darkest before it goes Pitch Black.

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    I was suprised by the temp. range 350 degrees, but a few weeks ago we wnet into a flashover simulator after RIT training, and got it pretty hot. The inside of my turnouts were definetly getting close to burning my skin when I would move. I have made some structure fires and been that hot, but not too many, like was previously stated at a fire we cool the atmosphere when it gets that hot. We used two thermal imagers with temp guages on them and both of them read about 600 degrees, give or take. I was somewhat suprised by that, but now that I stop and think about it, it seems about right, that being the average temp at a structure fire when you're low. By the way I wore the BF 2 for 10 years and just bought my first leather. I love it.

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    The shell does three things:
    Shed water
    Presents an image
    Provides a mount point for googles.

    The bump cap/suspension under it protects your brain.
    IACOJ Canine Officer
    20/50

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    When's the last time you seen a cows a** injection molded or glued together? The first,the last,a lifetime investment. If it's good enough for the cow,it's good enough for me.Nuff said! Hehe T.C.

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    Originally posted by Rescue101
    When's the last time you seen a cows a** injection molded or glued together? The first,the last,a lifetime investment. If it's good enough for the cow,it's good enough for me.Nuff said! Hehe T.C.
    When was the last time you seen a cows a**?

    They have their own injection molding process, and I am not putting my head in anything that can make this.

    http://www.cowpieclocks.com/images/products/clock2.jpg

    http://www.cowpieclocks.com/index.html

    Nuff said.

    Leather is one of the reasons cows are killed everyday.
    -Brotherhood: I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve.
    -Mistakes: It could be that the purpose of you life is to serve as a warning to others.

    -Adversity: That which does not kill me postpones the inevitable.

    -Despair: Its always darkest before it goes Pitch Black.

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    Originally posted by Rescue101
    When's the last time you seen a cows a** injection molded or glued together? The first,the last,a lifetime investment. If it's good enough for the cow,it's good enough for me.Nuff said! Hehe T.C.
    I guess you have never seen artifical incemination of the bovine species.....Talk about INJECTION!!!! ...And if the leather was soooo good for the cow then why did they take it from her?......besides....I wouldn't wear a bucket of hot, steamy, wet cow crap on my head....You never know were that leather came from either...you could be wearing butcherd cattle labia upon that grape of yours....I would stick my head in a cows dereier either...."I'll take the butcher's word for it"....An another thing is that those damn helemts weight just as much as a cow too.....I think I would rather tie a rock to my head..
    I'll stick to my Ben 2....I know were the "plastic" came from....and it definetly wasn't from some mammals a** or labia....
    Last edited by VinnieB; 08-05-2004 at 02:14 PM.
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    Hehe,Good morning gentlemen!Unbeknownst to y'all I do know a wee bit about the bovine series.My wife runs a farm,and part of the process is the growing of FOOD,Y'all familiar with that process? Good!Now to the matter at hand. I prefer the Bull to do the hard work but yes we have been known to do it artifically. We raise beef,pork and chicken,and turkeys.Nothing like good range raised product,you know what went in and out.As far as the quality of the "end"product believe it or not with a bit of research,yes you can tell exactly which cow that came from.Not sure about mfgs outside of Cairns but that's where mine came from.Now about that plastic? I wonder where that came from?And to truly inspect leather,the "Tommy boy"method really isn't the best way,I'll judge my steak swinging thank you very much.But I'm glad you guys piped up,should make for an interesting discussion.T.C.

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    LOL!...It sure has been entertaining....As far as the plastic goes...I believe its from a powder resin...
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    Vinnie,Ya kinda missed my "point",you also might have noticed I mentioned that a leather is a lifetime investment.Buy it,take care of it and the helmet will literally serve and protect you for the length of your career. I'm not so sure about the other materials. T.C.
    Last edited by Rescue101; 08-05-2004 at 01:44 PM.

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    They have their own injection molding process,

    No, no...it's an extrusion process!
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    Originally posted by Rescue101
    Vinnie,Ya kinda missed my "point",you also might have noticed I mentioned that a leather is a lifetime investment.Buy it,take care of it and the helmet will literally serve and protect you for the length of your career. I'm not so sure about the other materials. T.C.


    No not really...I just saw an opportunity to crack a joke....

    Well I am not going to agree with you about the Take care of it theory too much....I hope you don't "clean" your brain bucket?.. ....and if you do STOP its bad luck!...My father was a NYC firefighter for 25 years...he had the same helmet for only 12 of the 25...then they went to the new HUGE leather helemts..then the Ben 2...his helemt like many NYC Ff from the "war years" is a mess....NO amount of care could have prevented them from getting destroyed...traded in his "new" leather for the Ben 2.my uncle is in the same boat...NYC Ff for 30 years...he went through MANY leather helmets!...and another uncle was a NYC Ff for only about 12 years until his death...he had gone through 2 leather helmets...And in a few months when I get on the job...I will be happy with what they give me...

    I have also seem MANY leathers get detroyed in the Flashover trainer..usually the paint comes off first then the thing warps....GRANTED the poly carb helmets are the WORST IMO....I have seen some guys come out of there with globs of goo on the grape...and in actual fire too....

    I have 3 type of buckets...a Ben2, Cairns Leather and Phoneix "Thing"...I own the Ben 2 and the leather was issused to me when I became a Chief...I did try to order a Ben 2 insted but they caught on to me ...the Phoniex "thing" is....WAS for Tech Rescue work....I still swear by the Ben 2...NO HUGE suspention system to deal with an it sits lower on my head...I like that the material itself is what make the helmet strong unlike other helmets....My department switched from the Cairns 1010 to Ben 2 about 5 years ago...we encountered MANY problems with the cairns 1010 and 880s...and no longer have them...not even as spares...only the Chiefs wear leather...to my unliking
    IACOJ Member

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    Well it will be interesting to see how the Ben 2's hold up.Understand that for a majority of us I believe my statement still stands.New York is rather a unique outfit,destroy leathers over time;yes they can.But not in all companies,and I'd hazard a guess that in the busy companies that really "bend the leather"I'm guessing that they also don't spend a lot of time maintaining them,they are too busy doing the job.A leather is only as good as it's care.I fully expect mine to last the rest of my career;if it doesn't I have a spare.The composites?Hehe,fortunately they're not too expensive.They will destroy those too.Used to say gear should look crusty too;I do hope you wash yours.Bad luck or no my helmet gets cleaned and touched up from time to time to protect the leather that protects me.I come from old school;but I'm perfectly equipped and trained to operate "new" school.In a lot of ways the old methods worked great but we operate at a higher level of efficency today because of the modern equipment.To each his own,but I've adjusted well to cow and when I finally pack it in it will look great on my mantle.T.C.

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    Default Helmets...

    When it comes to helmets, I wish more people would
    consider "function" vs. "tradition" or just jumping
    on any bandwagoon.

    Go for comfort, centered and sits low.

    Many Chiropractors and condemned leather based
    solely on weight. From the head aches, to back
    aches to damaging your cervical spine. It is
    NOT a matter of "toughing up", working out or
    being more of a man. These are the facts.

    PLEASE keep in mind, I HAVE WORN A LEATHER
    HELMET and am pretty good shape with a good
    back. (knock on wood). After a while, the
    extra weight was not worth the "cool
    effect." Most of the senior dogs in my dept.
    have dumpped the leathers as well.
    Last edited by CALFFBOU; 08-05-2004 at 07:54 PM.

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    It's a left coast vs east coast thing.My chiropractor says FF in general is no good for you never mind the helmet.Remember your GOVERNMENT has had a factor on the leathers weight,the early versions were about the same as your typical tuppyware.T.C.

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    What is "tactical tupperware" made from?

    Composite plastics and resins, which are petrochemicals, which are derived from oil, which is a fossil fuel and non-renewable.

    What are leather helmets made of?

    Leather! A renewable resource!

    I rest my case!
    ‎"The education of a firefighter and the continued education of a firefighter is what makes "real" firefighters. Continuous skill development is the core of progressive firefighting. We learn by doing and doing it again and again, both on the training ground and the fireground."
    Lt. Ray McCormack, FDNY

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    Originally posted by stretch13
    I was suprised by the temp. range 350 degrees, but a few weeks ago we wnet into a flashover simulator after RIT training, and got it pretty hot. The inside of my turnouts were definetly getting close to burning my skin when I would move. I have made some structure fires and been that hot, but not too many, like was previously stated at a fire we cool the atmosphere when it gets that hot. We used two thermal imagers with temp guages on them and both of them read about 600 degrees, give or take. I was somewhat suprised by that, but now that I stop and think about it, it seems about right, that being the average temp at a structure fire when you're low. By the way I wore the BF 2 for 10 years and just bought my first leather. I love it.
    A thermal imager's temperature indicator does NOT show the approximate air temperature. It estimates surface temperatures, and even those can be inaccurate (especially when looking at metals). For a longer explanation on how they work, read my Myths vs Reality articles in the Technology Zone on Firehouse.com.

    Jonathan Bastian
    My comments are sometimes educated, sometimes informed and sometimes just blowing smoke...but they are always mine and mine alone and do not reflect upon anyone else (especially my employer).

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    Originally posted by Dalmatian90
    The shell does three things:
    Shed water
    Presents an image
    Provides a mount point for googles.

    The bump cap/suspension under it protects your brain.
    Not quite...the shell is a critical part of the head protection. The impact caps increase the resistance to penetration and provide insulation for your brain.

    The shell also provides a point for identification (to other FDs or within our own FD).
    My comments are sometimes educated, sometimes informed and sometimes just blowing smoke...but they are always mine and mine alone and do not reflect upon anyone else (especially my employer).

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    without further getting into the material war, does the shape and design of the helmet play a factor in anything? ie, the traditional one has 6 ridges, while the metros have a slight raise along the midline of the helmet. does that mean it can deflect an impact better? or have any other info about how shape and design falls into protection factor.
    If my basic HazMat training has taught me nothing else, it's that if you see a glowing green monkey running away from something, follow that monkey!

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  22. #22
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    Originally posted by DrParasite
    without further getting into the material war, does the shape and design of the helmet play a factor in anything? ie, the traditional one has 6 ridges, while the metros have a slight raise along the midline of the helmet. does that mean it can deflect an impact better? or have any other info about how shape and design falls into protection factor.
    There is no testing evidence that sugggests a particular style (traditional, contemporary or West Coast) is more or less protective. I have seen test evidence that shows thermoplastics (Ultem) to be more impact resistant than composites (fiberglass/Kevlar). This extreme test, however, is not required by NFPA standards.
    Last edited by firemanjb; 08-11-2004 at 11:41 AM.
    My comments are sometimes educated, sometimes informed and sometimes just blowing smoke...but they are always mine and mine alone and do not reflect upon anyone else (especially my employer).

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    Originally posted by DrParasite
    without further getting into the material war, does the shape and design of the helmet play a factor in anything? ie, the traditional one has 6 ridges, while the metros have a slight raise along the midline of the helmet. does that mean it can deflect an impact better? or have any other info about how shape and design falls into protection factor.

    From this thread:

    http://cms.firehouse.com/forums2/sho...threadid=61511

    -------------------------------------------------------------------
    In the last century, the leather firefighter's helmet was common. The helmet's long rear brim and curled up side brims helped prevent water from running down the firefighter's neck and into his coat. The earliest leather helmets featured four combs, which are ridges of leather marking stitched seams. Theoretically, the more combs a helmet had, the stronger it was, so later helmets came equipped with eight, 12, or 16 combs.
    --------------------------------------------------------------------

    The "combs" the the ridge on many modern style helmets are for strenght.

    Think corregated tin, or ruffle potato chips!

    Shape has a great deal to do with impact/penetration protection. One has to look no further then to modern battle tanks to see that.

    When the armor is sloped it does 2 things for you. The sloping of the armor helps deflect the impact/pentration resulting in a richochet. The slope of the armor also increase the Line Of Sight (LOS) thickness. If the bullet hits a flat plate of armor it only has to penetrait the actual thicknes of the plate. If it hits sloped armor it has to penetrait the cross section of the plate.

    So, when you slope or curve the armor you can increase is LOS thickness.

    Modern style helmets are well curved as are traditional helmets to some extent.

    One thing that MBTs have to worry about are shot traps. IE places on the armor that can trap a cannon round and actualy channel it through the armor. IE between the turret and the hull.

    Traditional and modern style helmets have a shot trap of sorts, the brim. A falling piece of debre can hit the helmet where the brim meets the impact cap. This can trap all of the energy that the impact has and channel it into your bean.

    For maximum inpact/penetration proection you have to move toward the dreaded Euro style helmet, IE the F1, Fire Knight, F7 Pacific, or Rosenbaur HEROS helmets. The full head protection, the shape, and the suspension of those helmets realy does offer greater protection. Just physics.

    Blows will roll off of these helmet better since there is no brim to trap the engery of the impact/debre. They also cover more of the head and in particulary the base of the skull/top of the spinal comlum where a severe blow can realy mess you up.

    That is why you see race car drivers, motorcyclists, soldiers etc... all wearing a similar helmet design.

    So if maximum protection is what you are looking for then the Gallet F1 style helmet is probly the ideal design/shape.
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  24. #24
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    Rosenbaur HEROS helmet...and a bazooka???

    Anyway, the shell glows in the dark like you just got nuked, it cover the head well, and it interfaces with the SCBA facepiece.

    Probly pretty good protection.
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    -Mistakes: It could be that the purpose of you life is to serve as a warning to others.

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    The shape of things to come? Maybe.

    Pacific experimental helmet, integrated SCBA regulator, built in lights. Evenualy built in TIC.
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    -Brotherhood: I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve.
    -Mistakes: It could be that the purpose of you life is to serve as a warning to others.

    -Adversity: That which does not kill me postpones the inevitable.

    -Despair: Its always darkest before it goes Pitch Black.

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