PMC Polyurethane Struts - by Jeff Quayle 07/04/2006
Overview
The following is a review the PMC Polyurethane undercart for the T-Rex. Thanks to Greg at PMC for providing the struts for review.
As we all know, Align's stock plastic struts can be on the brittle side. I've personally broken more than one strut just trying to get the skids installed. These new skids are not only much more resilient than the stock skids, but also come with a 5 year warranty. A guarantee against 'dumb thumbing' your heli into the pavement and breaking parts isn't something we see very often in the r/c helicopter world. Here's a look at what you get:
Packaged product 
Fully Assembled 
Set screws hold the skids in place 
Comparison to stock undercart
Crash Test
These skids are made from a high molecular high density polyurethane which is then machined into the finished product. It is quite stiff but does have a bit of give when flexed. Unlike the new Align or Heliup offerings though the polyurethane will not spring back to it's original shape if bent. Four set screws are also installed in the struts to secure the skids with a provided allen wrench. This makes installing the skids quite easy and with a quick tightening of the screws the skids hold in place very well. No loctite is needed as the struts themselves will hold the screws. The undercart has a slightly wider stance then stock. This should prove helpful for people still learning or just looking for a bigger footprint.
I had the opportunity to 'test' the durability of these skids during a mechanical failure today. The heli came down mostly flat, but leaning slightly forward and to the left. Here are some photos of the skids post crash:
post crash 
view from bottom
Back to normal
After a quite re-adjustment, I was able to bend then back into shape. Although you can do the same thing with aluminum struts, eventually they will become brittle and break. I'm told by the manufacture that this can be done repeatedly without weakening the struts. That durability allows them the confidence to offer a warranty that I doubt you will ever see on plastic or aluminum struts.
Front
Rear
This is not the first pair of struts I've used that were supposed to be 'the last pair I ever needed to buy'. Although I like the new Align 'bump resistant' skids they are far from unbreakable and the Heli-Hobby Delrin struts lasted me several months until I actually crashed with them. They also snapped like a twig. Whether you like the different styling of this struts comes down to personal opinion, however the 5 year warranty is an undeniable advantage over any other struts I'm aware of on the market for the T-Rex. I'm quite happy with these struts overall and it has found a permanent home on my test heli.
PMC makes the same style skids in aluminum minus the warranty.
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