Sonex Hydraulic Brakes on my Sonerai IIL

[soneraifred]

I thought you guys might be interested in the new Sonex hydraulic brakes that I’ve installed on my Sonerai IIL. See photos showing the installation in my Sonex Brake Install album in the Soneraifred gallery. The installation was really straightforward. The brakes are designed to work with ¾” axles and the Azusa 5” wheels, and the entire package fits within the diameter of the wheel. It makes for a very compact package. The only difficulty I had was figuring out how to provide an anti-rotation stop on the brake unit. I ended up installing a 1/4” grade 5 bolt, nut, and some washers, and cutting a slot in the axle mounting plate to engage the end of the bolt. I also found it necessary to chamfer the center bore on the brake unit to clear the radius under the head of the axle bolt so the unit would seat properly. The brake disc bolts to the inside face of the wheel using three countersunk, allen head machine screws replacing the original bolts holding the wheel halves together.

I found that my original MCP master cylinders did not provide enough pressure to make the brakes effective enough because I’m constrained to having brake levers only 6” long, and the MCP’s have 7/8” diameter cylinders. I resolved the situation by installing a set of Hegar ½” diameter master cylinders with 7” levers to raise the operating pressures. Bleeding the Hegars is a bit of challenge, but now the brakes work really well.

The one task that I have left is fitting a new set of wheel pants. My old pants were two-piece to clear the original brake units, and were pretty well beat up, so because my new brakes fit within the diameter of the wheels, I’m going back to one-piece pants.

 

[Gaston]

Hello Fred

Very interesting installation
But I can't see how the disc are pinched by the calipers...
could you add a few photos please ??

Gaston

 

[smoothmat]

I have seen a style like this on another fellows plane (if its the same?). The calliper doesn't squeeze, it pushes against the brake rotor.

 

[Gaston]

Oh I see ...

Gaston

 

[soneraifred]

Matt is correct. The two brake pucks push on the inside face of the brake disc. The puck force is reacted by the outer wheel bearing. This concept is not new. The first set of Great Plains hydraulic brakes that I had several years ago worked the same way.

 

[Pttim]

Nice work Fred, Looks like a very light weight setup.

 

[mhflyit]

Fred - very neat setup. I have the GP hydraulic brakes and wondered if you had any operational issues with those and what difference you've seen with the Sonex brakes.

 

[soneraifred]

Matt:
These new brakes replaced a set of Great Plains disc brakes. The GPASC brakes were very effective, even with the MCP master cylinders. The reason I replaced them is because they were very noisy when taxiing. They'd rattle and clatter enough to drive me crazy. It was probably due to the fit between the calipers and the cast caliper holders. I may have had too much clearance, although I tried tightening the fit by applying aluminum tape to the outside of the calipers. I also machined the wheels where the disc mounts to minimize the disc runout. None of it seemed to help for very long. There may be a better way to eliminate the noise, but I couldn't find one.

 

[phzabriskie]

Had time to look over your pix, great installation Fred. I will look for follow up later in the Summer to see how they hold up over time. One question, how did you polish your gear to get that very decent reflection of your wheels?
-Pete

 

[soneraifred]

Hi Pete: There's no magic in polishing the gear. I used Mother's Aluminum Mag polish, over and over again. The more often I use it, the better the gear looks.

 

[Desloges]

Hi,

I now install sonex brakes as Fred did, with hegar master cylinder to replace cable brakes, I can't read anywhere if the hegar is dot 5 compatible.

Does anyone know that, sure Fred.

Pascal

 

[soneraifred]

I have DOT 5 silicone brake fluid in mine.

 

[Desloges]

Ok Many thanks Fred

Pascal

 

[MarkW]

Hi Fred,

I'm getting ready to put brakes on mine:
Are you still happy with the Sonex brakes?
On your levers do you have a way to lock them for parking brake as well?

Thanks,
Mark

 

[soneraifred]

Hi Mark: I'm still happy with my Sonex brakes and Hegar master cylinders. For a parking brake, I use piece of bungee cord with a hook on one end to hold the brake levers back. The hook was fabricated from 1/4" steel rod stock. The bungee cord is attached to fuselage cross member at the back of the rear seat. I'll try to get a photo and attach it later.

 

[MarkW]

Fred, Thanks for the reply your gallery tells a real good story on how to install them as well. I did order the brakes last evening.

Thanks again,
Mark

 

[wbpace]

This may be one of those threads that never go away entirely, and I freely admit I am committing the sin of reopening an old topic.

So Fred, how well do your brakes hold during runup? I seem to recall that some have reported their brakes are not quite enough to keep them from rolling when at full power.

And as I recall, you use the Azusa AZ-1137 wheels, right? What size spacer did you use on the inboard side of the axle between wheel and landing gear?

O'Bill

 

[soneraifred]

Hi Bill:
My set up, which now has a pair of Matco MC-4 master cylinders with a separate reservoir, will easily hold 2500 rpm. I’m pulling pretty hard on the levers, though. Holding for run up is not really a concern for me. I start the engine on the magneto, taxi out to the run up pad, turn on the secondary ignition, turn off the mag to verify that the secondary is working properly, turn the mag back on, and go flying. The “mag check” is done at idle. By the way, the mag drop is 100% since the tach is driven by the mag.