steel vs composite strut?

[cdogg37]

we are getting ready to purchase a strut system and have looked at all the major brands. res q jack, rescue 42, zmag, airshore, advance rescue systems (ARS), and junk yard dog. there all about the same. my question is how strong are the composite struts compared to steel struts. some people say the composite is stronger than steel. how is this posible when there are all the holes drilled in the composite? dosen't that weaken the composite metrial? steel has been around for ever and has proven to be strong! I've also heard that when composite metrails fail it breaks with out warning, where steel will bend first giving you some warning. also what about longevity? Has any one seen any failures in any of the strut systems that are out there?

[WLynch]

there all about the same.

Codgg,

First, if you think that all the struts are basicly the same then you haven't really looked at them all.

As far as your question about composites, I saw a composite strut that had a tool droped on it and it caused a fracture on the inside of the strut which wasn't visible from the outside.

I understand that the strands in a composite strut run verticle and do not offer much support from a lateral impact. And you are correct, a steel strut will bend before it fails.

Good Luck.

[SpokaneRep]

According to WLynch, wood is out of the question too, since its strands run the length of the strut, and it snaps when overloaded. So you should not look at ZMag. You probably dont want steel either, since it corrodes and might not be visible from the outside. Come to think of it, Im pretty sure there is nothing that is completely idiot proof available on the market today, so I guess you are going to have to take you chances

[GhettoBatt1]

Composites

Struts are all based on the same concept...make the strongest geometrical shape- a triangle. Now, the qustion is, how much time do you want to spend making that triangle? I have seen homemade struts guys fabricated in the basement of the firehouse work just fine for YEARS prior to the influx of them on the market. Just pick something simple to use. Also...dont pick composite struts based on the fact that they're marketed as "hybrid safe-wont conduct electricity..." come on now, lets be serious...

[Purdue03b]

we are getting ready to purchase a strut system and have looked at all the major brands. res q jack, rescue 42, zmag, airshore, advance rescue systems (ARS), and junk yard dog. there all about the same. my question is how strong are the composite struts compared to steel struts. some people say the composite is stronger than steel. how is this posible when there are all the holes drilled in the composite? dosen't that weaken the composite metrial? steel has been around for ever and has proven to be strong! I've also heard that when composite metrails fail it breaks with out warning, where steel will bend first giving you some warning. also what about longevity? Has any one seen any failures in any of the strut systems that are out there?

cdogg37, you are correct when you assume the material is weakened when drilled. You are also correct when you question the failure mode of steel vs. composites. There is generally no warning, audible or visible when it comes to composites while steel or aluminum (the best compromise of strength vs. weight) will deflect before failing. They aren't all about the same either as one of the other posters states. Do you really think the Airshore strut can handle all the load on one pin? Put them into use (I have) and try to get the load evenly supported on both pins, it's near impossible and normally you can simply pull one of the pins out which means your working load is effectively cut in half. Plus, that's point loading in the extreme, all your load is transferred through that impossibly small pin cross-section. Your best bet is to have a rep from each brand come out and let you get some serious hands on training with each tool in a rescue scenario if possible. You should take a look at Paratech too, as they are a competitor with Airshore and all the FEMA USAR teams have their struts. Let me know what you choose, I'm always interested to hear what someone chooses and why, keeps me informed and up to date.

[MetalMedic]

my question is how strong are the composite struts compared to steel struts. some people say the composite is stronger than steel. how is this posible when there are all the holes drilled in the composite? dosen't that weaken the composite metrial?

Drilling holes does not always mean the material is weakened. In some materials, the addition of holes to the material changes how weight is distributed into the material and can result in strengthening the material in some regards.

I think you are getting some decent feedback here, but the bottom like is that you need to have a set that YOU are comfortable with. While you say that they are all basically alike, I disagree since they all have some differences in how they operate, how they are deployed and how they are set up. Find the one that feels the best for you and your department and go with it. When you get them, TRAIN, TRAIN and TRAIN until you are completely comfortable and confident with them.

[Purdue03b]

[QUOTE=MetalMedic;796537]Drilling holes does not always mean the material is weakened. In some materials, the addition of holes to the material changes how weight is distributed into the material and can result in strengthening the material in some regards.
QUOTE]

Taking away material NEVER strengthens a material, all you do is remove material that could othewise better distribute the stress. Medic ask any machinist or engineer, it's impossible to take away material and strengthen something. Whoever told you that probably wanted to sell you some oceanfront property in Kansas too. It is where you concentrate the material that it is important, that's why a larger diameter hollow strut with the material at the perimeter(i.e. aluminum tubing) is better at resisting deformation than a smaller diameter solid strut (solid aluminum bar).

[Purdue03b]

And please, don't get me wrong, I'm not disparaging any struts with holes drilled. I'm sure the designers took into account the holes when designing them for strength and safety. Composites are a wonderful material when it comes to strength vs. weight factor which is why they make many race car bodies out of them. I do agree with MetalMedic in that you need to buy what you are comfortable with and what you feel your department can best afford. One consideration that I don't see many people post is cross-department compatibility. What are the nearby departments using and can they be used in conjunction with your selection? It makes it that much easier for rescue crews to execute a safe and quick extrication if they already know how to use your equipment should multiple rigs show up and can use any and all pieces.

[mcaldwell]

We just bought the Res-q-jacks, and have been very impressed so far.

Weight is a minor issue, but the fact that I have little fear about cross-loading, UV or chemical degradation, or drop damage, means that we can put up with the little extra weight. And the load capacities were cirted as the same for each manufacturers jack struts (8000 max /4000 working).

And hell, I know that in the worst case scenario, I could even weld on these if I had to. I prefer to slightly over spec and not need, vs underspec and limit my options.

But having said that, we tested many designs, and I'm sure we would have been more than happy with any of the major manufacturers for our day to day needs.

[MetalMedic]

Medic ask any machinist or engineer, it's impossible to take away material and strengthen something.

Actually.... it was an engineer who told me this, and explained it rather clearly as well... but I am not going to argue with you. Regardless of what you want to believe, the bottom line still is that you need to have a set that YOU are comfortable with.

[Purdue03b]

Actually.... it was an engineer who told me this, and explained it rather clearly as well... but I am not going to argue with you. Regardless of what you want to believe, the bottom line still is that you need to have a set that YOU are comfortable with.

Medic, it's not what I want to believe, it's what I know. I AM an engineer and I do stress analyses as part of my job and I use the latest analysis software along with hand calculations to double check what the computer spits out. People trust their lives to our products, I can't afford to be wrong. We have products that have drilled holes and in every case, when the product is taken to failure in testing,the product will always fail at the holes, why, because holes weaken the material. Like I said, I'm sure whatever engineer designs a strut takes into account that when he removes material from the strut wall, he strengthens the strut elswhere to account for that loss. As was posted earlier, all the struts are certified independently for their individual ratings. Good luck with your choice cdogg and safe rescues.

[MetalMedic]

Medic, it's not what I want to believe, it's what I know. I AM an engineer and I do stress analyses as part of my job and I use the latest analysis software along with hand calculations to double check what the computer spits out. People trust their lives to our products, I can't afford to be wrong. We have products that have drilled holes and in every case, when the product is taken to failure in testing,the product will always fail at the holes, why, because holes weaken the material. Like I said, I'm sure whatever engineer designs a strut takes into account that when he removes material from the strut wall, he strengthens the strut elswhere to account for that loss. As was posted earlier, all the struts are certified independently for their individual ratings. Good luck with your choice cdogg and safe rescues.

Well... if you have products with holes drilled in them that are failing at the location of the holes, maybe you need to get back to the drawing board. In the meantime, talk to the engineers at the hydraulic tool manufacturers who have holes in their spearder arms and their links attachments and ask them why they have holes in these critical parts of the hydraulic tool.

[BuzzCut1]

Our Batallion Chief dropped by with a suprise package of four Rescue 42 strut systems so I guess we shall see first hand how well they work an hold up

[mcaldwell]

I think you will like them. We were an inch away from going with them.


Let us know how the testing/use goes.

[Purdue03b]

Well... if you have products with holes drilled in them that are failing at the location of the holes, maybe you need to get back to the drawing board. In the meantime, talk to the engineers at the hydraulic tool manufacturers who have holes in their spearder arms and their links attachments and ask them why they have holes in these critical parts of the hydraulic tool.

Medic, we take them to the failure point so that we can see what safety factor to include, they don't fail in the field when correctly used. The reason they have holes in the "spreader" (spearder?) and attachments is to save weight, the same reason every manufacturer puts holes in a product. Plus, the holes are in the planar direction of the spreading force and don't have the same stresses as in a strut which sees a bending moment when in axial loading. Our company has done work hand in hand with a hydraulic tool manufacturer, so yes, we have experience with spreading tools.