A Concern About Plastic Cribbing Tests

[rmoore]

I found what I consider to be a significant fact in the crush testing data published by Turtle Plastics, a plastic cribbing manufacturer, regarding their own product. They essentially placed a 4x4 plastic block in a press and crushed down on it. They advertise that their plastic cribbing withstood 50,000 lbs of crush without any deformation.

Later in this same document, they describe another cribbing test with much different results. They placed two cribbing pieces parallel with
a third plastic crib perpendicular across the top of this first layer of blocks. Sort of like the beginning piece when building the second layer of a box crib.

They placed the load onto the center of the top cross block. In this
test, they report 1" of deflection and stopped the test with only 2,390 pounds of force applied.

That's not 25 tons like they state in the first part of the report! That is what I consider significant bending of a piece of cribbing with a little over ONE TON of weight. I'm not too impressed with that performance.

You can review this same report and make your own conclusions. Go to http://www.turtleplastics.com/ and follow the links for "Fire Dept". When that page loads, near the very bottom, you'll see a running message. Click on that to get the pdf file of the report.

[lutan1]

I'd expect that sort of deflection Ron when cribbing is used in this fashion.

Rescuers should be loading cribbing on the areas that are supported by each other, in this case that it sounds like you're describing, on the outside, not the middle.

If we're going to load the middle, then we should be building either a 3x3 or 4x4 crib...

[Resq14]

If the points of contact with the cribbing aren't inline, then I'd expect the same deflection, as Lutan already said.

Of course, I still don't like plastic cribbing.

[MetalMedic]

Ok, what would happen if we put the same load on the same location of a 4x4 wood cribbing set up the same way? Of course I am worried when they publish a test that is conducted in what appears to be an improper manner.

[EEResQ]

"A Concern About Plastic Cribbing Test"

OK, after reviewing Turtle Plastic's published test results on their "Dura-Crib" product I agree that when comparing only the first and last test, the results are remarkably different. However, on the back page of Turtle Plastics product literature the results of four test are included. Each test while similar, was conducted to challenge the "material" in a different way. The fourth test, the one where a two pieces of cribbing were placed parallel to each other with a third piece on top (like the start of the second layer of a box crib) resulted in deflection of the single piece of cribbing by 1 inch when 2,390 pounds of force was applied via a 3 inch steel plate at center of the crib block. This fourth test showed "flexibility" of this material without cracking. This test was never intended to be read as a test of the "overall strength of the material." That number was found in the results of the first text: 0.22 inch of deflection with slight deformation and no cracking at 50,000 pounds of force applied through a steel plate along the full length of the crib block.

In essence, about six years ago the manufacturer had a third party lab conduct these test to see what the material was capable of. Today, we as rescuers are concerned with the performance of the end product as we would use it in real world situations.

We should be asking:

* When using this cribbing how does a properly constructed box crib hold up under varying loads?

* How does the same box crib hold up if the load suddenly shifts?

* How much stronger is this box crib if I utilize three crib blocks per course versus two per layer?

* Is this cribbing made of material that is susceptible to drying out, cracking or shattering?

* Does this cribbing material absorb fluids, fuels or chemicals which could interact with one another or me?

From personal experience as a +15 year distributor of rescue equipment, an instructor and an emergency responder, I have found that today's plastic cribbing (produced by several manufacturers) performs well in all these areas. Additionally, in a telephone conversation with Tom Bradley-Norton, President of Turtle Plastics, Inc., Tom agrees that their published test results were not intended to answer the questions raised here; they were merely intended as performance test of the material used. However, Turtle is in the process of developing test that will provide answers to our questions. I certainly look forward to these test results as well as to the published test results from the other three manufacturers of plastic cribbing.

Let's be safe out there!

[Rescue101]

I've had the pleasure of talking with Tom at the BRR classes held in Concord NH.This gentleman is keenly interested in improving his product line as it pertains to rescue ops.We've given him some suggestions which you will find incorporated in their current product line which allow "tipping"(angled blocks)so you can build a proper crib on a slanted load.While I'm sure this helps the Mfg. bottom line,it is our safety and ease of system operation that were foremost thoughts on his mind.T.C.

[Resq14]

Re: "A Concern About Plastic Cribbing Test"

Originally posted by EEResQ
This fourth test showed "flexibility" of this material without cracking. This test was never intended to be read as a test of the "overall strength of the material." That number was found in the results of the first text: 0.22 inch of deflection with slight deformation and no cracking at 50,000 pounds of force applied through a steel plate along the full length of the crib block.

Apples-to-apples....

The 25 tons that you say is the "overall strength of the material" is being applied over the full length of the cribbing, correct?

How often do we would build an ENTIRE box crib that ensures the total weight is being distributed equally along the ENTIRE load supporting surface areas of each piece? The fact is, even when you build box cribs with 3 blocks per layer, you are not anywhere near full contact between blocks. Someone on here has mentioned measuring strength in PSI, and I think that's a good idea. Then we can compare 1 square inch of plastic to 1 square inch of different wood and any other materials.

However, like has already been stated, roughly 4,000lbs shared between 2 top blocks of a crib would produce 1" of deflection. We don't have breaking point information.

Their test of cribbing that reflects what I consider closest to real world box crib use: "With the cribbing lying flat, a 3-inch steel plate was placed on the cribbing to simulate the contact area of another piece of cribbing. The compression was stopped when there was a deflection of 0.75 inch. The force in pounds averaged 13,350 pounds at which point there was slight deformation and again no cracking."

Regardless, the 50,000lbs does seem misleading after reviewing the ad.

EEResQ should mention that he is a distributor for Turtle Plastics, btw.

[EEResQ]

The fact that I own an emergency equipment distribution company is openly stated in both my personal profile and in my departmental affiliation on record for anyone to read here on Firehouse.com. There's nothing sinister here for you to attempt to make an issue of; but I'm certain that you will.

Yes, in the course of my business I handle Turtle's cribbing products, as well as plastic cribbing manufactured by ResQ Tek / Zumro ResQ. They are just a couple of the dozens of manufacturers that I represent in the emergency services marketplace. (Haven't you noticed that up to this point, I've intentionally avoided referencing any one of the four manufacturers of this product?) However, as has been my policy for over 15 years now, I REFUSE TO HANDLE ANY PRODUCT that I have not personnally reviewed and tested from an "END USER'S" perspective. It is from this "user's" perspective that I can approach these manufacturers with my unbiased opinions of their products.

When I tested Turtle's first generation of plastic cribbing in 97' and '98, I was not convinced that it was a product that I would have recommended to go on a rescue unit. However, their step chocks did perform adequately. In stead of tearing them down, I gave them my honest opinion of their product's performance and offered suggestions for improvement. What I soon found out was that Turtle was listening to many of us in the emergency services field, and over the next three years Turtle continued to expand and improve their products.

Begining in 2000 and into 2001, I was asked to try their new Lincoln Log "locking" cribbing. Over a nine month period, we used this style of plastic cribbing along side of PT wood cribbing in almost every conceivable situation. With few exceptions, both worked great. As no product is perfect in all situations we did not find it all that earth shattering that in some situations wood worked better, and in others "locking" plastic cribbing worked better.

From a purely product performance perspective, we found only three negatives with the early Lincoln Log cribbing:

1. Lack of uniform spacing of the knotches on the "prototype" manually cut crib blocks provided.

2. Reduced lift height resulting from the knotches in the 4 x 4 Lincoln Log type crib blocks.

3. The wedges they provided where cut to wide and at to steep an angle to be effective.

These issues were brought to Turtle's attention and changes were made in their finished product. The only negative that remained unresolved was the reduced lift heigth. After much trial and error, we found that by carrying the correct number of crib blocks for the anticipated event (passenger vehicle MVA's, truck or bus MVA's; ect.) we could optimize the crib load required on various rescue units and overcome this negative.

* 38 crib blocks, 4 wedges and 2 standard step chocks was found to work well in most "light rescue" situations.

* 52 crib blocks, 8 wedges and 4 step chocks became our standard rescue package.

As the rescue unit's size and available space on a unit increases, the crib load can always be expanded in consideration of the rescue organization's mission.

Now, with uniform "molded" Lincoln Logs we set out to make them fail under static loads and under loads that shifted. I freely admit, these were not "laboratory test." However, they were "real world" applications of the product. Like lifting a junked coal mine truck that had and estimated loaded weight of +50,000 pounds (the bed was full of old diesel engine blocks!) and supporting the load on box cribs constructed out of lincoln logs and the newly redesigned wedges. The box cribs not only held under the load, as they were being erected one of the fighfighters reached around for more cribbing and accidently hit his box crib with a block hard enough to have dislodged a level. The "interlocking" aspect of this cribbing proved its' value as he did not have to reposition any of the crib blocks; they remained intact as he postioned the next level. The new wedges held in place as well. The cross cut wedges now exactly fit into the lincoln log's knotches. As they are cut from 3.5" x 3.5" HDPE stock, the wedge face is rough enough to bite under the load.

For the first shifting load we used a CASE 580M Backhoe / Loader (operating weight: 16500 lbs.). We built three box cribs: one of lumberyard PT 4 x 4's, the second of lumberyard PT 6 x 6's, and the third of standard 3.625" x 3.25" Lincoln Logs. (Sorry, no red maple was available.) Each box crib was constructed to the same height and had three crib blocks per level with a "solid top layer" to act as a lifting surface. The equipment operator lowered the loader bucket to the ground and then placed the hoe bucket on top of each box crib. Lifting the construction vehicle completely off the ground, he then shifted the backhoe boom left and right until the respective box crib failed. The results are quite remarkable! A few weeks later we repeated this with a DEERE 410G 4WD Backhoe / Loader (operating weight: 18,600 lbs.) with the same results.

This is not, and has never been, an advertisement for anything!

Wood cribbing (both hard and soft wood) is better in many rescue applications while plastic "interlocking" cribbing performs better in others.

My original goal was, and has always been, to promote the use of CRIBBING whenever the situation calls for it.

What started all this was when someone posted a scarcastic reply to "an unplanned advantage of plastic interlocking cribbing:" Departments who made the financial committment to purchase this product were observed to be training with it more, and thus were deploying it more often! I'm certain that if that same department were to invest in a shipment of RED MAPLE hardwood cribbing, the results would be similar.

Either way, is this such a bad result?


BTW: Is there anyone out there who doesn't read a member's profile to get a feel for why they may hold a particular position on a subject?

[Resq14]

I think it is important for people to know that you sell Turtle Plastic's product, as well as the others. The webteam has previously stated that you don't have to be advertising to violate this part of their guidelines.

Originally posted by webteam
Attention Forum Posters

We are going to ask, and add to our terms of service, a clarification to the existing rules:

"Representatives or associates of manufactuers will not be permitted to post messages that directly relate to their products or competitors."

Not only have several manufactuers recently posted messages, others have assumed 'false identities' in essense to promote their product or site.

http://cms.firehouse.com/forums2/showthread.php?s=&threadid=30678&perpage=15&pagenumber=2

All I like to see is that reps be open and fully disclose any relationships they might have with a product or company.

One correction though, you are advertising in the fire department station listings.

http://cms.firehouse.com/dept/Independence2KY

Please recall that in another thread you implied that departments who use wood do so because they don't adapt to new technology, and that progressive departments use plastic. Once again, I'm merely trying to point out that there may be a reason(s) OTHER than tradition that people continue to use wood. Do I care what your department chooses to do? Absolutely not! It's your call.

***********************
***********************

I value the information that you have shared in this last post. The real world information IS useful. I don't doubt what you're telling us. I'll just repeat that I'd like to see some standardized way of indicating performance in controlled conditions so that the consumer isn't relying on "war stories" to make an educated purchasing decision.

Stength in PSI, flexibility, coeffecients of friction, effect of age, exposure to elements, etc. should be furnished by the manufacturer and confirmed by independant testing.

AGAIN, I know there are many departments having success with plastic cribbing. I'm just sharing my thoughts, opinions, and experience.

Tony

[EEResQ]

Please, Try To Get YOUR Facts Straight; Thank You.

Originally posted by Resq14

..."I think it is important for people to know that you sell Turtle Plastic's product, as well as the others.

Tony

FYI: AND FOR THE RECORD


On 11-14-2003, in my first posted reply on the topic of plastic cribbing, I stated:

"From personal experience as a +15 year distributor of rescue equipment, an instructor and an emergency responder, I have found that today's plastic cribbing (produced by several manufacturers)...", prior to voicing "my opinion" on this product.

Why then, do you continue to leave this FACT out when you attempt to disparage me everytime you post a reply? Are you incapable of engaging in an open discussion without attempting to discredit persons who hold an opinion that differs from your own?
FYI: These are HYPOTHETICAL questions and they don't require an answer. Similar to the questions at the end of another post where YOU assumed that I was implying a law suit. What a laugh! Law suit; over an Internet forum posting?

Now, about what YOU say I have said. I freely admit to being somewhat esoteric at times. However, these are your words Sir, not mine. Example: ..."I believe you had implied troglodytes and other neanderthals used wood,....
(BTW: "Neanderthals" should have been capitalized. I demand respect for my race Sir!)

While I admit to using a little "toung-in-cheek" humor, AT NO TIME have I implied, or used the words that YOU have posted.

Please, let's agree to just stick to the thread and not turn words around or add words that were not there to begin with. I'll agree to refrain from aplying any humor that may be misunderstood.

Everyone would then benefit the free exchange of thoughts and opinions on the topic.

[Resq14]

Re: Please, Try To Get YOUR Facts Straight; Thank You.

Originally posted by EEResQ
From personal experience as a +15 year distributor of rescue equipment

Forgive me, but I didn't realize that distributor of rescue equipment meant Turtle Plastics cribbing. I should have assumed this.

"All commercial related representatives or associates MUST identify themselves as such within EACH post"
-DIRECT FROM THE FH.COM FORUMS TERMS OF SERVICE.

YOU ARE A DISTRIBUTOR FOR TURTLE PLASTIC'S CRIBBING.

YOU ARE COMMENTING ON THE VIRTUES OF PLASTIC CRIBBING.

ARE YOU ADVERTISING IN THIS SPECIFIC FORUM? QUESTIONABLE.

ARE YOU STILL VIOLATING THE RULES, REGARDLESS? YES.

I did not make up the quote from webteam, but I sure do agree with them. And since others have been called on the exact same behavior, it is only fair that you should be also.

I'm ignoring you so people don't have to keep reading my replies to your prodding. I've read and written enough. At least everyone can now read your posts with the knowledge that you are a distributor for the products on which you are commenting here, and webteam can do as they feel appropriate.

[EEResQ]

Response.

What is it that so upsets you?

When I first looked into affiliating with Firehouse.com, I communicated with the folks in charge of member registration. Upon filling out my "PROFILE" I appropriately listed my occupation: "Emergency Equipment Distributor." This information is just one mouse click away from forum readers.

Once in the MEMBER ZONE, I found that Firehouse.com had added a category to the pull-down window under "Department Affiliation" titled: "FIRE EQUIPMENT / APPARATUS DISTRIBUTOR". That's exactly what I am, so I checked it and filled out the form accordingly. My business information appears where it does because that is how the program is presently set up. It takes about three mouse clicks to view this information through Firehouse.com's MEMBER ZONE.
'14, No one is trying to hide anything from you. The fact that YOU did not know that an equipment distributor could do this does not make it wrong!

You make a point of stating:
"At least everyone can now read your posts with the knowledge that you are a distributor for the products on which you are commenting here,..." In this, you have conveniently left out that, in addition to the entry in my personal profile, this statement was included in the posted reply that set you off:
"From personal experience as a +15 year distributor of rescue equipment... Now, that said AGAIN, why is this an issue with you AFTER I have already stated the fact in: #1 My PROFILE, #2 my MEMBER ZONE Affiliation, and #3 my ORIGINAL post?
Additionally, I notice that you have not attacked others who have posted THEIR information here.


In a nutshell: I am keenly interested in advancing the practice of STABILIZATION. In our region, it's so often a seldom applied skill. (Heck, I don't even take the knowledge of what a box crib is for granted, much less its' proper construction.) I involved myself here because I read something that I disagreed with from a "user's point of view," and I replied. If read literally, the rule you have quoted would mean that I cannot reply to any thread on the University Of Extrication forum if that thread involves the use of rescue equipment. In effect, this completely takes away my privilage to participate in this forum; a privilage that I have been charged a fee to receive.

Step back a momment and consider just how many active and retired fire/rescue types today are also affiliated with companies that manufacture distribute or maintain emergency equipment and vehicles. In fact, it's difficult to find someone in this business who is not also involved in the emergency services of their communities; and that's a good thing! Is it the intention of YOU and the webteam to tell these members that they are not welcome here?

I fully agree with the prohibition against advertising or selling a product on the forum. However, after I have complied with all rules in effect at the time I was accepted into membership (see note below) at Firehouse.com, for rules to be adopted saying that because of my occupation, I cannot voice my personal opinion on a topic seems like a rather severe form of selective censorship.

NOTE to readers: In Resq14's most recent eddition of his previous post about me, he has added these words in hyper bold print; "All commercial related representatives or associates MUST identify themselves as such within EACH post." However, he continues to alow post by distributors of competing products on this forum. I guess one only needs to identify themselves if Resq14 doesn't like their product.
Last edited by Resq14 on 12-04-2003 at 07:19 AM.