During the build, I learn volumes from other builders. Through their websites (like this one), email, message boards and fly-ins like Oshkosh and Sun-n-Fun. One of the things I hear repeatedly is that the Matco brakes that come with the kit are awful. Both from a building standpoint (a pain to work with and around) and more importantly from a functional aspect. It appears that a common complaint is that the brakes feel mushy and brake fade is almost a certainty during heavy braking.
After hearing these stories I discovered that Velocity offers an upgraded braking systems from a different manufacture. Cleveland brakes are easier to work with and offer much better braking. But when I checked with Velocity, I learned since I had already taken delivery, I couldn’t exchange the brakes and that I would effectively have to purchase them outright.
Arrgh!
So I did some research. FAR (Federal Aviation Regulation) 23.735 states:
- Brakes must be provided. The landing brake kinetic energy capacity rating of each main wheel brake assembly must not be less than the kinetic energy absorption requirements determined under either of the following methods:
a. The brake kinetic energy absorption requirements must be based on a conservative rational analysis of the sequence of events expected during landing at the design landing weight.
b. Instead of a rational analysis, the kinetic energy absorption requirements for each main wheel brake assembly may be derived from the following formula:
where–
KE = Kinetic energy per wheel (ft.-lb.);
W = Design landing weight (lb.);
V = Airplane speed in knots. V must be not less than Vs √, the poweroff stalling speed of the airplane at sea level, at the design landing weight, and in the landing configuration; and
N = Number of main wheels with brakes.
Got that? 🙂
The brakes that I have are Matco model W600XT’s which have a “KE” rating of 337,932 ft.-lb.
I haven’t been able to find the rating of the Cleveland brakes, but they’re the same brakes used on a Cessna 210. Now the Cessna 210 is BIG airplane. Six seats with a gross weight of 3,800 pounds. By comparison, the Velocity XL-RG has four seats with a gross weight of 3,000 pounds.
Those brakes on a Velocity would clearly be enough, right? Not so fast… literally.
Reviewing the formula, notice the “V”. That’s the speed of the plane at landing.
Plugging the Cessna 210 specifications into the formula reveals a KE requirement of 292,996. Which means that you could use the Matco’s on a Cessna 210 with a 13% margin. So why are the Cleveland’s so much better at stopping? I suspect that the Cleveland brakes are rated a bit higher than the Matco’s. Probably around 350,000 ft.-lb.
So then I used the Velocity numbers in the formula. What I discovered is a KE requirement of…. drumroll please. 348,863 ft.-lb.
For me, this is a problem. Because the Velocity lands at 75 knots instead of 57 knots like the Cessna 210, the amount of additional braking energy required is significant. The Matco W600XT brakes are rated at only 337,932 ft.-lb. This explains the mushy brake complaints and fade after heavy braking. As far as I’m concerned, this changes the Matco-Cleveland issue from an “optional upgrade” to an “absolute necessity”. But the upgrade (which by my estimate would bring just within specs) was going to cost about $1,000.
So I did more research. I heard rumors of what I can only describe as a mythical Matco brake rated at 450,000 ft.-lb. I could find no reference to this “super brake” anywhere. No other builders have them, and no one has heard of it.
So I took a wild shot in the dark. I called Matco. 🙂
I was connected to an engineer and I explained my situation. He seemed… concerned that I was running W600XT’s on a Velocity. He said that I need W600XTE High Energy brakes rated at… wait for it… 450,000 ft.-lb.
So I asked how much they cost. He said “You’ve got 600XT’s?” I told him I did and he said that I could just replace a couple parts to convert the 600XT to a 600XTE (High Energy). “How much is that going to cost?” I asked, bracing for the response. “About $300” he replied. I ordered them on the spot.
Here’s the parts list:
WHLD6HE – High Energy Disc (2 required) $96.62
WHLBSP600XT-1 – Spacer (2 required) $39.29
WHLBSP6-1 – Spacer (4 required) $4.95
MSC.31-17×1.75HHBOLT – Bolt (8 required) $1.60
WHLBSP600-1 – Spacer (4 required) $4.95
WHLLM29700LA – Roller Bearing (4 required) $21.08
MSCAN4-21A – Bolt (4 required) $.60
MSCNL8 – Washer (8 required) $.69
It actually came to $416 (he initially forgot about the bearings), but still a bargain for better stopping power.
Here are the inside and outside view of the current brake system
Here are all the tools that I used:
First I removed the two nuts and bolts that hold the torque plate in position.
You can remove the torque plate at this point.
Next the four hex screws that hold the calipers in place.
Here it is disassembled.
Then it’s just putting it back together in the reverse order while substituting the new parts for the old.
Here’s the end result. New W600XTE on the left.
In the upper right corner, you’ll notice a bag of bolts and washers. These are supposed to replace the caliper retainer bolts/washers. Originally, these are safety wired. Instead of allen-head screws that are safety wired, they sent me regular hex head bolts with some fancy locking washers. My guess is that when you remove these bolts the washers will have to be replaced. I’m going to call Matco to see if I can still use the old screws with safety wire. Otherwise, I’ll order a bunch of these washers.
The primary difference is the disc. It’s thicker and it has three angled grooves cut into the face. All the other parts simply allow the thicker disc.
Here’s a close up of the old and new disc.
Now this isn’t going to make servicing the wheels and brakes any easier. But I’ll be able to stop. 🙂
I’m still a ways off from finding out how well they stop but now I’m much more confident that I will stop.