Hydraulic brake conversion

[DCASonex]

Used GP brakes with custom mount that incorporated wheel pant mounting, and toe brakes. The toe brakes should be applicable to Matco and may not be as complicated as you think. photos and drawings on old yahoo Sonex builders form under "Modifications to Sonex #1327", or e-mail me if interested.

David A.

[mike.smith]

On the Sonex hydraulic brakes, which I'll be installing next week, I saw a reference on another site, but not in the plans, to having to add a 1/16" spacer "somewhere," or to shave the brake pads 1/16". Can anyone who has installed those brakes shed some light on that?


BTW, after 50 hours flying my Sonex I'll offer my opinion about differential braking (I have a tail dragger). Like most people I have spent over 400 hours flying planes with differential brakes, so I got used to them. But I have not found any need for them on a Sonex. It would be nice to have the brakes on the control stick like some people have done, but I've gotten used to the single handle near the flaps. Just my personal observation.

Mike Smith
N439M

[falvarez]

I added a washer between the hydraulic brake unit and the wheel hub to provide the extra space needed; otherwise, the pads were pressed against the disk even when fully retracted. I used a unibit to drill out hole in the washer, so you only need to find one with the correct outer diameter.

[SNX1454]

Matco brakes
I installed Matco dual toe brakes when it took 500 feet for the Azusa drum brakes to stop me from 20 Kts with my Viking engine at idle on my first taxi. The Matco brakes have exceeded every expectation, which, of course, has created its own problems. I have 4 master cylinders, one on each rudder pedal, and link everything together hydraulically. The brakes easily hold the 110 horsepower at WOT at the end of the runway. My Sonex is trigear and I have found that the dual brake thing is pretty useless as I have to use the toe brakes simultaneously or all I do is load the nose wheel up to one side. It certainly doesn’t help much with the steering. I am considering removing the left master cylinders and plumbing the brakes to operate together off the right brake pedals. My use of the 1/8” nylon tubing Matco sells would make all this very simple.

One problem I have is that the Matco master cylinder pedals hardly depress, maybe ¼” at lockup, so you don’t get pedal motion merely pedal pressure. No spongy brakes. I didn’t design the pedal linkage that way so my pedal position is awkward.

Not sure how a differential hand brake thing would work out. Also question its necessity at least on a trigear or without a free castoring tail wheel. There is also the mechanical advantage required for the master cylinder linkage might be a space problem.

Things of concern if you install Matco brakes:

You have to use Matco's wheels with this setup. Azusa's are not convertable.

A stress analysis of the Sonex brake torque tab shows that it is totally inadequate for the Matco brake torque. I welded on a wider .125 thick 4130 tab with a longer arm and used an AN-4 bolt for the reaction to the brake back plate.

The Sonex kit Matco sells has an axle spacer that is much too long so you have to machine that.

Use Matco’s short master cylinders and save weight and money. The long stroke is useless.

It takes very careful design and layout to get everything to fit on the back plate. Be very careful.

Make a separate 6061-T6 mounting plate for the wheel fairings. The back plate is just too small to get it all to work with the fiberglass fairings and their required cutouts and fender washers.

I use Dextron III ATF for brake fluid because it is red (you can see it and bubbles in the 1/8” lines), has the necessary viscosities, is compatible with the rubber components, is available anywhere and works wonderfully. 5606 turns to goo when a spill is exposed to air for a long time and is messy.

[mike.smith]

I added a washer between the hydraulic brake unit and the wheel hub to provide the extra space needed; otherwise, the pads were pressed against the disk even when fully retracted. I used a unibit to drill out hole in the washer, so you only need to find one with the correct outer diameter.

Thanks. That's what I needed to know. I have some large washers of the right diameter left over from shimming the axle nut (to get the right pressure and get the cotter pin in the hole). I think they should do the trick.

Thanks again,
Mike Smith

[daleandee]

BTW, after 50 hours flying my Sonex I'll offer my opinion about differential braking (I have a tail dragger). Like most people I have spent over 400 hours flying planes with differential brakes, so I got used to them. But I have not found any need for them on a Sonex. It would be nice to have the brakes on the control stick like some people have done, but I've gotten used to the single handle near the flaps.

The only time I used differential braking was during my tail wheel endorsement training. In my Sonex I haven't needed differential braking; but in full disclosure I don't fly in really nasty crosswinds if I can help it. Some who fly the Waiex have said they are needed but that's a different rabbit trail to chase.

A couple of experienced tail wheel Sonex guys told me that once I had the tail pinned to the runway life would get easier. Last year on the way over to ASA I had a "full attention required" crosswind landing in Georgia on a fuel stop. But just as I was told, once the tail was down, even when it grumbles a bit, stay with it and it will do exactly what your feet tell it to do.

The direct tail wheel steering on the Sonex makes me feel like I'm cheating when I admit to being a tail dragger pilot. :oops:

Dale
N319WF

[DCASonex]

To SNX1454,

Simplifying hydraulics by removing one toe brake cylinder and operating both from one pedal will will leave you pushing harder on one pedal when braking which will not simplify steering. One brake hand grip on stick does work well, Only reason I put differential toe brakes on mine is that those saved by behind from nasty ground loop in a Luscombe many years ago, but like the result and would do so again.

David A.

[ldmill]

I also used the Matco conversion kit for Sonex and absolutely love them. I don't get wheel shimmy or grabbing during braking at all. I also used their matching single handbrake setup. I did have to fabricate my own wheel pant mounting bracket from 4130 plate like SNX1454 mentioned above, but that wasn't too hard at all. I can do a WOT run-up (2900+rpm) with my Jab3300 and get no creep. Also installed the hydraulic brake lock - it's totally worth it to do so. I did not add an additional brake torque tab, but would consider doing so if doing this again. This is a pretty highly stressed component and I've had the bolt loosen up on me even when using blue Locktite. It's the only non-factory mod I did on my Waiex - and I'd do it again in a heartbeat.

Regarding differential braking and port side cross winds, I've got 120 hours and several hundred take-offs now on my Waiex and am finally getting a handle on this issue without diff brakes. I live in Iowa and if you don't fly in over 10mph crosswinds - you might as well sell the plane. I've been able to deal with winds of 10-15kt almost direct on my left side by using the following technique:
1) Left full aileron and begin backing off to neutral the faster you go.
2) Do NOT start the takeoff run with full throttle - only go to about 2500-2600rpm till you can get the tail up(~30mph). Once the tail is up, then go WOT. If you go WOT immediately - it's a prompt and exhilarating left hand turn and off into the weeds chasing furry animals you go... you WILL have to change your shorts afterwards...
3) When the tail comes up - you have complete rudder authority and left side crosswind is not really an issue at that point.
4) Do an arcing takeoff path starting on the left side of the runway with the nose pointing at the ride side about 300-400' down the runway. By the time the tail comes up at 30mph (and at 2500-2600rpm) - you will be straight down the middle of the runway.

I have absolutely not been able to keep the plane straight on left side crosswind with only the tailwheel with more than even a moderate crosswind.

Taking off with a right side crosswind and landing with crosswind from either side just isn't an issue with a Waiex. Just use standard good tailwheel techniques.

Just my $.02. Cheers!
Lorin Miller
N81YX

[mike.smith]

I'm converting to the Sonex hydraulic brakes, from the machined drums. For anyone who has installed these brakes, did you do anything about the wimpy tab on the bottom of the axle assembly? It bends as easily as a piece of cardboard, and has been incapable of not doing so with my standard brakes, leading to brake assemblies that grab the drums because they won't stay square to the drums.

Mike Smith
N439M

So now that I have the brakes on the axles, I'll answer my own question. The depth of the brake body, and it's relatively close fit to the axle, means the brake body itself provides all the stability required against the axle. So that little tab is doing almost nothing, other than making sure the backing plate and brake assembly don't rotate. The assembly is solid as a rock on the axle. The hole in the tab has to be updrilled to match the AN3 hardware that goes through it.

http://www.mykitlog.com/users/category. ... egory=7396

Mike Smith
Sonex #439

[hickej]

Here is a quick video of the Sonex brake conversion.
https://www.youtube.com/watch?v=RRZIaTf5G3c
Jim Hicke W0162 3300 TD