Q-talk 134 - Finley/LaRue/Coughlin/Hoskins Q2 Brake Installation
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- Category: Q-Talk Articles
- Published: Wednesday, 23 December 2009 16:24
- Written by Jon Finley
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Up until January 2009, I had been using the AirHeart brakes with a relatively cheesy caliper mounting bracket, "floating" disks, and a single master. This has worked "ok" in that the brakes were useable and did not feel unsafe. The breaking "power" has always been very poor with some tendency to grab slightly on initial application, so I was always very careful.
During my condition inspection in January 2009, I disassembled the brakes and found incredibly uneven pad wear which was caused by the caliper not being in alignment with the disk. A couple years ago I had a batch of the LaRue/Coughlin/Hoskins brackets water-jet cut from drawings that Sam Hoskins made. So, I figured now was as good a time as any to install this proven "better" brake mount solution.
The calipers went in the parts washer; the water-jet cut brackets needed just a bit of time with a file and cleaned up nicely. The hardest part of this bracket assembly is making the threaded rod "tube" on which the brake is able to move laterally. I threw it in the lathe, and started boring the center. A few hours later I had the four pieces required.
Assembling the brake with the brackets is pretty straight forward, I just looked at Sam's photos. (These Photos & drawings can be seen at the QBA web site under Issue 134 Photos) The only change that I made was installing a nut on the threaded rod on both sides of the bracket.
Installing the caliper assembly in the wheel pant was a royal pain!! The cut out for the brake assembly had to be enlarged. However; I always enjoy work that involves power tools and sharp bits and blades! A little grinding and the fit was perfect. The REAL problem came along when I discovered that the existing brake lines were not long enough. The obvious easy solution is to just pull a bit of line thru and put an extension back in the cockpit. Easy enough - wrong! I was unable to pull the line thru the pant, obviously well floxed in place. I ended up making a bit of an "extension" from brass parts at the caliper. Basically, I ended up with a rather long 90 degree brass elbow.
I spent a few minutes trying to figure out how to mount the caliper assembly so that it was perfectly aligned with the disk. The only good solution that I could come up with was to "set" the brakes so that each caliper was clamping itself to the disk and then mash a bunch of flox between the caliper mounting bracket and wheel pant - thus creating a custom "spacer". Well, that sounds nice, but I'm an impatient sort and waiting a day for epoxy to cure is always painful for me. So, I ran to the hardware store and bought some of the two-part epoxy paste that you "squeeze" together to mix and it hardens in 15 minutes. I set the brakes, mixed the paste, squished it between the bracket and pant, and then very lightly tightened the bolts (holding the brake to the wheel pant) causing a nice squeeze out of the paste.
Did it work? Yes, it seems so. After getting everything installed and tightened down, I spent some time taxiing around and found that I have very even breaking. If you are fighting with the mounting of the Airheart brakes, dragging, or binding - I would strongly suggest trying this LaRue/Coughlin/Hoskins setup - it really works! As of this writing in April 2009, I have a few dozen landings and about 30 hours with the new setup and I am pleased. Additionally, my brakes no longer make the "squeak, squeak, squeak" sound as I roll my plane in and out of the hangar.
Those of you that know me, know that I am a cheapskate. I was quite shocked when I discovered that the AirHeart brake pads are now $60 for a two wheel set. The search was on for an alternative. My first iteration are installed with the new caliper brackets - time will tell if it is a good option or not.
McMaster-Carr (www.mcmaster.com) sells brake/clutch lining material rather inexpensively and has several options. I ordered 12" of part number 6175K173 for $8.00. This is a strip of material 3/8" thick and 2" wide. Compared to the AirHeart pads, this material is quite soft & flexible.
I used a 2" hole saw to cut two "pads", chucked them in the lathe, and a few minutes later had pads that matched the dimensions of the AirHeart pads. I had been semi-fearful of how long this step was going to take and was shocked at how quickly it went. So, for the second set I started the timer - 14 minutes from start to finish! Since my time is very valuable and worth about $300/hour, I figured my homemade pads cost $158.00!! Seriously; the pads are still working very well and I've had no problems. However; I have not removed the pads and attempted to measure how much wear has occurred. I will do this next condition inspection or if/when the braking action starts to fade.
Those of you that know me, know that I am a cheapskate. I was quite shocked when I discovered that the AirHeart brake pads are now $60 for a two wheel set. The search was on for an alternative. My first iteration are installed with the new caliper brackets - time will tell if it is a good option or not.
McMaster-Carr (www.mcmaster.com) sells brake/clutch lining material rather inexpensively and has several options. I ordered 12" of part number 6175K173 for $8.00. This is a strip of material 3/8" thick and 2" wide. Compared to the AirHeart pads, this material is quite soft & flexible.
I used a 2" hole saw to cut two "pads", chucked them in the lathe, and a few minutes later had pads that matched the dimensions of the AirHeart pads. I had been semi-fearful of how long this step was going to take and was shocked at how quickly it went. So, for the second
set I started the timer - 14 minutes from start to finish! Since my time is very valuable and worth about $300/hour, I figured my homemade pads cost $158.00!! Seriously; the pads are still working very well and I've had no problems. However; I have not removed the pads and attempted to measure how much wear has occurred. I will do this next condition inspection or if/when the braking action starts to fade.
By the way, I still have enough of the water-jet cut brackets available for about five airplanes. I had a large batch made a few years ago as part of a group buy and these are the left-over. I'll sell these for $30.00/set (both sides of a Q2) plus shipping. If you want a set let me know by email (This email address is being protected from spambots. You need JavaScript enabled to view it.).
Submitted by Jon Finley Subar-Q Los Lunas NM
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