Rob, et al,

 

Chris is right.

 

Let's remember that the "rat-trap" springs purpose is to ensure the over center link is locked and remains so, not extend the gear.  On jacks or in the air these springs may make it seem slow to get the mains to lock at the end of the non-hydraulic extension.  On jacks it should take only a few pounds of outward pressure to finally get the over centers to lock - in the air a minor slip or skid will use air against the middle door to provide the pressure to ensure a lock.  One way to avoid this minor problem is to lubricate all the gear pivot points and keep the springs clean and lubricated (LPS-2 is OK) so that the coils can move against one another easily since they are so close together.

 

I think I got my rat-trap springs before 1996 (first flight) and they worked adequately for me since then.  I recently had a call from the new owner of the airplane and he said he was going to replace the springs because they did not have the same shape as the newer ones.  OK as that will make him feel more comfortable. 

 

The real test is that the over-center links are easily locked and that they stay locked.

 

Scott Krueger

 

Chris,

 

Thanks for the encouragement. I am afraid my confidence in those rat trap springs has been rather battered. At the very least I will be measuring those springs at each annual inspection. I would like to incorporate both types of springs if I could ascertain what coil extension springs I need, but I don’t know how to specify them.

 

I am still some way off flying yet, so I have time to research it.

 

Thanks again for your input.

 

Rob.

 

 

From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Chris Zavatston
Sent: Sunday, 28 July 2013 1:35 AM
To: lml@lancaironline.net
Subject: [LML] Re: L360 Over centre springs

 

Rob,

Let Lancair know about the replacement springs going soft.

I am still using my original rat-trap springs after 15 years (1,400 hrs) of flying.  They work great.  Springs are not rocket science, but it sounds like you've rein into an inventory or manufacturing issue.  

The rat trap spring was a great design improvement.

Once you get your hands on a good set, you'll be set for life.

 

Chris Zavatson

N91CZ

360std

www.N91CZ.net

Sent from my spiffy iPhone

On Jul 27, 2013, at 9:12 AM, "Stevens Family" <stevens5@swiftdsl.com.au> wrote:

Another query for those who have, or have built the L320 or 360,

 

I purchase a partly built L360 kit some years ago, which I am still in the process of building. It came with the original undercarriage. I decided to upgrade to the outback gear early in my build process, and installed it some years ago. After a couple of years, I discovered that the Rat Trap springs were not maintaining their tension when the gear was in the retracted position, and on occasions, when I extended the gear (which I do by hand as the aircraft is upside down in the jig) the hook would disengage from the over centre link. Upon enquiry with Lancair, I was advised that they had had a bad batch of springs, so they subsequently replaced them, free of charge. The replacements are shown on the order as being “ Item 1441” and “SEQ U10B”. That was in early 2009. With the new springs, all seemed in order.

 

Today I was again working in the wheel well, and discovered that once again these springs had lost tension and were not remaining engaged when the gear was in the retracted position. I have scanned the LML archives and notice a number of others have had similar problems. One poster had only been saved because he had installed both the Rat Trap springs, and the “screen door” springs. Others had had Rat Trap springs break. All of this has severely shaken my faith in them, as there is no back up if they mal function.

 

My options from here appear to be to either try another pair of Rat Trap springs, or install the original screen door springs, or perhaps install both. However the screen door springs which came with the original kit are too long for the outback undercarriage, as the distance between the hinge bolt of the over centre link, where they attach at one end,  and the undercarriage pivot bolt where they attach at the other end, is about 60mm (2 3/8”) shorter on the outback gear.

 

Has anyone else had problems with later Rat Trap springs in recent years since the original problem ones?

Has anyone out there used screen door springs with the outback gear? If so, what specifications are the springs?

 

Thanks in anticipation.

 

Rob Stevens,

Perth, Western Australia.