Trying to determine the Safe properties of Face Guards

[IanHathaway]

Trying to determine the "Safe" properties of Face Guards

I work in a sports science laboratory and I've been set the task of trying to create a simple and inexpensive test to determine which face guards are safe when two field hockey players clash heads (one wearing a face guard the other unprotected). You have to excuse me if my question has a simple answer or if my terminology is a little out, its been many years since I've had to use physics in anger.

Here is the state of play so far:

• 
  I have or can get data relating to injurys and what pressures can cause bone/facial damage. I am therefore looking to express a safety rateing based on pressure levels in combination with the hardness of material and shape of face guard. The last two items I can already determine but I'm struggling with the pressure part.
  I can assess the pressure exerted using a pressure sensitive photo film easily enough but this method is not ideal because it is very expensive and only gives results for one or two points on each face guard.
  A simpler and much cheaper method is to drop the face guard into clay and measure the depth of penetration. I know the kinetic energy at the point of impact and I can work out the impact force but I'm not sure how to convert this into a pressure value. I know this should be easy as pressure has a direct relationship between force and impact area but due to the shape of each face guard its not so easy working out what the impact area is.

Any suggestions would be most appreciated.

 

[Andy Resnick]

I'm a little confused- are you looking at the face guard *independently* from the rest of the helmet?

 

[IanHathaway]

Yes in a way. The face guards are actually separate items that do not come attached to a helmet, in effect just a mask. They are not designed to protect the wearers head just their face. There are already methods for checking the protection given to the wearer from ball or stick strikes but not the protection given to other unprotected players in a collision.

 

[Andy Resnick]

I see- it's similar to a baseball umpire's mask. You may have some luck seeing how those are evaluated:

http://umpattire.blogspot.com/2009/03/what-we-know-about-mask-safety-is.html

http://www.nocsae.org/standards/pdfs/Standards%20%2711/ND035-11m11%20-%20Mfr%27d%20Hockey%20Face%20Protect%20perf%20std.pdf

I guess some umpires are actually starting to wear hockey gear...

 

[IanHathaway]

Thanks Andy, we already test to similar standards but these are for the wearer of the face guard as opposed to the effects the face guard has on an unprotected player.

The mask shown above is actually designed for a cricket wicket keeper but is being used by field hockey players to protect them from ball and stick impacts. It is a trend that has been growing over the last 4-5 years and the International Hockey Federation has asked us to look into it.

In field hockey there are things called penalty corners where the players are rushing at each other. As the ball is flying at a high velocity some players choose to wear face protection and others don't, its only for a few minutes of the game but its at this time when clashes of heads are most likely. The IHF want to make sure that the face protection that they sanction does not present a danger to players who elect not to use it.

 

[sophiecentaur]

Sounds like an SUV with bull bars versus a mini convertible. Quite a serious issue but it's either up to the players attitude or the rules to be changed.

 

[IanHathaway]

Quite a serious issue but it's either up to the players attitude or the rules to be changed.

That is what the IHF is trying to do, impose a ban on certain face guards but to do that they need a simple test that can be applied by manufacturers and the sports governing bodies that says which face guards are safe and which are not. The test needs to be backed up by a scientific study, which is what I'm doing, rather than just a "feeling" that some face guards are safe and some are not. I'm here because I'm struggling with the final part of the study ... cheers all.

 

[netgypsy]

There are pressure sensors you can stick to the guard I would think. I know they use them on horses to figure out how much pressure is exerted on the back of the horse by different saddles and pads and riders. They obviously have to "talk" to something but it's probably pretty small. Two sources you might consider - Consumer Reports who does all sorts of testing and Myth Busters TV show that runs all sorts of strange experiments. I would think either would have done something similar in the past so you can get some ideas from them as to how they have approached it. Let us know what you finally use. Very interesting problem.

 

[mrspeedybob]

Make 2 heads out of ballistics gel. Equip 1 with a face guard and 1 without. Smash them together at a speed and angle typical of a hockey collision and asses the damage to the unprotected head.

 

[IanHathaway]

Make 2 heads out of ballistics gel. Equip 1 with a face guard and 1 without. Smash them together at a speed and angle typical of a hockey collision and asses the damage to the unprotected head.

Needs to be a quick, simple and cheap test unfortunately

 

[Andy Resnick]

It's such a strange problem- the danger safety equipment poses to *other* players. Wouldn't it depend on where contact occurs? A face guard smashing into someone's face is going to cause different problems than a face-to-shoulder impact, for example...

 

[sophiecentaur]

There exist 'The British Standard Finger' and 'The British Standard Eye socket' (and possibly others) that are used when deciding on the risk of trapping bits of you or poking bits of you in equipment that's being assessed. There are also recommendations about padding on steering wheels and other car parts. I'm sure that it would be easy enough to apply the automotive work to this problem. It concerns bodies and could involve similar speeds of impact.

Have you thought of ROSPA as a source of info?

I guess that a simple rule to apply could be that you need the same cushioning on the outside as on the inside - i.e. no bull bars.

 

[IanHathaway]

Just to clarify:

The test is not needed to show that the face guards are safe for the wearer, this is already covered by other standards, but that they are safe for other unprotected players in the event of a collision. They only want to look at face guard to head contact but that contact will be from varying angles. They are not interested in contact with other parts of the body, people tend to recover from cracked ribs, broken collar bones better than they do from smashed eye sockets, blows to the temple and crushed wind pipes.

This is a new test required by the sports governing body that will determine the laws of the game regarding which face guards will be suitable for national and international competitions around the world. It needs to be cheap and simple so that manufacturers and others can carry it out without having to purchase expensive equipment. It needs to be clear and concise so that there is a definative yes / no answer without any grey areas.

The test has three parts, the first is an assessment of the shape (no pointy bits or sharp edges), the second is to check the materials used to make sure they are not to hard or brittle, the third is way of teting the applied pressure and will use an impact into clay. The first two checks are easy and will include dimension checks, hardness scales, impact tests etc. The test using clay has already been approved but the sports governing body want to be able to justify it to the manufacturers and players with hard scientific evidence that certain types of face guards are acceptable and others aren't.

I'm looking for a way of converting the figures I have into something that can be compared to medical statistics that shows the various pressures required to damage certain parts of the head, neck and face.

Cheers All

 

[netgypsy]

Like the idea of padding the outside of the facemask.

You could run a test with ballistics gel yourself and repeat it precisely using some kind of very consistent putty. There should be information already from the automotive industry, Consumers Report and the sports industry indicating how much indentation it takes to do physical damage to that part of the face using ballistics gel and it should be public. By calibrating your putty with the ballistics gel you would have at least some reasonable indication of just how dangerous the masks are to an unmasked player. This way the first test might be a bit pricey unless you can get sponsorship but the followups wouldn't be.

Let us know what you end up doing. This is very interesting.