04 February, 2003
Improving the Brakes on the M-18
Thanks to Glenn Bell, ex Mite owner and glider pilot, here are some links to information about fixing the notoriously weak brakes on a Mite.
Putting the Bite Into Weak Drum Brakes, by Tillman Steckner [from Soaring Magazine, 1998] [PDF 538KB]
"The [Steckner] mod at first appears to be confusing and difficult, but it is actually a fairly simple. Anyway, here it is in its entirety for the maintenance page. I'm reasonably certain that this mod could be adapted to the Mite.
"I'll add a link here as well that I found from users of this mod. It has impressive reviews, and comes with a warning that if the mod is done improperly the brake could lock up. Apparently several people have sent glider brakes to a guy in Sonora, CA, just down the road from Columbia, for brake work with excellent results. He specializes in antique motorcycle drum brakes which is pretty much what the Mite has. I think this is where I'll send my glider brake."
Discussion in AviationBanterforum on the topic of brake upgrades, including comments on the good work done by Michael Morse at Vintage Brake.
2010-12-28
Suggestions on improving Mite brakes:
I have noted that you have had several questions about the Mite Brakes. I have had many thoughts on the same subject. My first repair was quite successful but quite expensive. I installed new Cleveland 5 inch wheels with disc brakes. With the 5 inch wheels I had to use low profile Lamb tires. They will retract nicely. The axle on the Mite is 3/4 inch and the Cleveland wheels are 1-1/4 inch. I welded a sleeve on the original axle. If you reverse the brake pedals you can mount the hydraulic cylinders to the arms on the brake pedals. I bolted mounting lugs on the firewall for the other end of the cylinders. The hydraulic reservoir is also on the firewall. None of the above is approved!! But works great.
The second method I have installed on one of the Mites undergoing restoration but not flown. I replaced the old 1950 brake cables with motor boat throttle cables. On the wing stand they work extremely well. I took the old cables to MonteVista Marine Inc., a local boat store in Flagstaff, AZ. I didn't tell them what the cables were for. I bought two 33C9 teflon lined throttle cables. I paid $31.30 each plus tax.
Just an idea!
Submitted by Ray Allen, N476M
New Brake Cables for the Mite:
Marine 33C9 throttle cables are almost exact replacements for the original
brakes cables on the Mite. Ray Allen used these on his Mite, currently in
rebuild, but hadn't tried them yet. There are some modifications needed, which I
thought I could share.
The terminations of the 33C9 cables are longer than the originals, resulting
in the brakes, with no adjustment, being (1) as far released as possible and (2)
the brake peddles as far forward as possible. Only through hyperextension of my
ankle could I actuate the brakes with my foot. Fortunately, the extra length of
the terminations can be easily (?) corrected by threading the wheel end rod
about another 1-1/2 inches, which leaves some room for adjustment of the brakes
with wear. AFTER extending the threads, cut about 1-2/3 inches off the rod. DO
NOT remove the sheathing. We shortened the sheath about 1/2 inch and found we
were already just past the rod/termination at the twisted cable. If you do not
remove any of the sheath, you can make the modification on one end only;
otherwise you're going to have to extend the threads at both ends -- not too
hard if the cables are free, but once installed, it's much easier to work on the
wheel ends.
The threads are 10/32. The two cable diameters were slightly different, resulting in one being very hard to thread -- the existing threads were the same, as expected.
After replacing the clevis, adjust the brake lever so the shoes are just touching. Total movement for brake action is less than 1/4 inch, static test. (My brake pads are like new for lack of use!)
The brakes work GREAT now and will hold for runup and brake for turning off -- much better than before. I'm thinking that others with braking problems might be plagued with tight cables like I was. I lived for 3 years with poor brakes, never knowing the cables were the whole problem.
Another caution!! Do a retract check! The extra length must not interfere with the gear. On my first flight with gear down, I could only get about 1/3 retraction before hitting something. I didn't want to force it, fearing (1) the gear sticking up, (2) bending something or (3) pulling out the just-completed cables. I'm not sure what's wrong yet, I just took the plane home this evening. I'm going to check it sometime in the next couple of weeks; it feels like an interference, which I'm sure will be much easier to solve than the cable installation. I've had the Mite on sawhorses before for retract tests and tire replacement and have a good procedure, jacking up one wheel at a time and sliding a padded sawhorse under each wing, just inboard of the wheel wells (per the M18X assembly drawings), plus weighting the tail.
I want to again thank Ray for finding replacement cables; this is the first time I've got really good brakes. If anyone wants to talk about the installation, email me.
David Dodson, N393A. January 9, 2002
Additional comments by Dave, added January 14, 2002:
We've finished troubleshooting and solved the [interference] problem. The basic mistake by my mechanic who did the initial install of the new cables was leaving one of the cable clamps off. It is possible one was missing before, from when the plane was rebuilt three years ago. But with the new cables, both clamps are essential. The first is on the axle swing arm, the second on the side of the strut (on a bolt in a cast hole).
The new cable has a slightly larger diameter and is stiffer than the
original. When the gear was swinging up, the cable was catching between the
swing arm and the pivot of the lockdown arm. However, on the other side, the
cable appeared to be hitting the over-center lock joint. Both cables showed
signs of abrasion from just the one attempt at retraction (during the flight
home).
The placement of the clamp on the swing arm is also critical. If it is inside
the structure, it will impact the centering pad on the rib cutout and prevent
the gear from retracting fully (about 95% up). Therefore, the clamp must be on
the outside; however, if too far inboard, the cable will rub on the hinge.
I believe the old cable was thin and flexible enough to pass between these more easily and, perhaps, didn't even really need the second clamp on the strut.
The strut clamp must be rearward-facing and the cable must curve from the first to the second clamp tightly, to avoid the above-mentioned contact. Since there are likely differences between airplanes (we even found some left to right side), several retractions and adjustments will likely be required to assure no binding or rubbing of the cable.
When all is done, the brakes work great, so it is definitely worth the effort. And, of course, be careful putting the Mite on and off the sawhorses and weight the tail before jacking it up so you don't damage that beautiful wooden wing. As always, you can always call to talk about Mites and, if you're not too far away, I'd probably enjoy traveling to wherever to help out with the installation and adjustment.
Submitted by Dave Dodson, Mite N393A
04 February, 2003