Actual Flying Rotax Installs

[Kai]

Kai - did you check out the parts catalogue I mentioned above ? - two different hand/master cylinder options.

Yes- I did. Thanks for letting me know!

However, they come with a hefty price- I will probably have to get a little more desperate before I decide to contact them.

Kai

[Kai]

Kia,
I have Great Plains (now O'Keef) brakes with custom differential toe pedal operators and came much too close to pulling my CAMit 3300 powered tail-dragger over on its nose when a stray gust of wind at end of runway of our hill top airport lifted the tail. MUCH TOO CLOSE! Now only do full power run-ups with tail tied to something immovable.

David A.

David,
That can’t have been much fun! And compared to the prop dia that goes for the CAMit, the 64 inches on my own Sensenich would only make it much worse. Only emphasizes to heed the dire warnings from Sonex Tech.

Thanks
Kai

[DCASonex]

Kia, I installed my hydraulic brakes before Sonex offered their own version. Back then they were telling one and all that any change from their wonderful mechanical brakes would end up tipping your plane on its nose. I have never come close to pitching my plane forward when applying them while still moving following landings, Just use common sense. I see no need for Full power run-ups prior to flight. If there is any problem when applying full power it will likely show up early in the run with time to abort.

David

[Kai]

All,

I have learned that the size of lever operated MCP master pump Sonex supplies in the Aerobrakes kit, is 3/4”. As mentioned previously I am toying with the idea of replacing it: either with a single 7/8”, or install a second 3/4”- one master for each caliper.

Now, my knowledge of hydraulic brakes is limited: so what would you suggest?

Thoughts? Comments?

Thanks
Kai

[Murray Parr]

I have learned that the size of lever operated MCP master pump Sonex supplies in the Aerobrakes kit, is 3/4”. As mentioned previously I am toying with the idea of replacing it: either with a single 7/8”, or install a second 3/4”- one master for each caliper.

Kai,

Larger diameter master cylinder will decrease the braking force to the slave cylinder (calipers) and the brake lever will travel less. You actually need a smaller master cylinder bore size to increase the force applied to the slave cylinders but that will increase the travel required on the lever. Think of it as changing the mechanical (hydraulic) advantage ratio. Not sure if you can buy much smaller than 3/4" and if you can, it might need to have a longer stroke. A simpler way of increasing force would be to change the mechanical advantage with the linkage geometry however, you are now potentially applying more force to the master cylinder than the designer intended.

Murray

[Kai]

Murray,

Much obliged for your comments- but not what I was hoping for!

I know of one Sonex standard gear flying in this country with the original Sonex puck calipers. After testing with the original single 3/4’’ MCP master the owner informs it was replaced with two pcs 7/8’’ Hegar hand lever operated master pumps- one pump for each wheel. At least- that is what he says. Maybe they were 1/2’’?

I tested this setup- the improvement was startling! That is why I thought of trying something similar.

So what you are basically telling me is to downsize: what about two handlever operated 1/2’’ masters?

Thanks
Kai

[Skippydiesel]

Hi Kai,

Just wondering how easy it would be to use two hand levers (independent main wheel braking).

Have had a short fly in a Europa, configured as a conventional tail dragger and fitted with two hand brakes - not so easy to use when landing. Once down, did help with tight turns at taxi speed.

I am experienced with one lever, mounted on the control/joy stick, operating both mains - does a good job but does not facilitate tighter turns.

Trained in an aircraft fitted with independent toe brakes - also works well but great care needed to avoided doing a ground loop.

[Kai]

Skippy,

Yes- you do have a point!

As long as the levers are short, such as a dual Hegar setup, it is definitely doable- at least I don’t seem to recall any paricular problems.

However, playing two long levers like on the Sonex setup, might be something else- I am far from sure I want to go down that road!

I see that Hegar can provide a 1/2’’ master with a button on the stem, intended for floor installation and heel operation. What about two of those, one for each caliper?

Thanks
Kai

[CaseyCooper]

Kai,
Murray is absolutely right.
A larger bore will decrease your overall brake pressure, a smaller bore will require a little more effort, but much more pressure. On my Sonex I’m using 1/8” line and 1/2” bore Hegars on my Sonex brakes and if I try and land short and apply hard pressure, I have to back off sometimes because my tail will rise and the plane will nose over. They are toe brakes so I am able to apply a good amount of pressure. They do provide adequate stopping power. Differential definitely makes a difference in control and stopping ability. Now I don’t need a parking lot to make a u-turn. Hegar makes a quadrant of dual masters and handles you could install. Also you could install 2 handles on the stick, I say that because my other aircraft with Hegar brakes have them set up on the handle and they work awesome. I just alternate with my fingers and I don’t have to take my hands off any controls. Only difference between the 2 planes is I have Hegar disk brakes on one, and Sonex on the other. Lines and bore sizes are all the same. I would shy away from heel brakes in my opinion. Or, just make some toe brakes!

[Murray Parr]

Kai,
I ran the numbers for the master cylinder sizes. The Sonex standard setup (if the master cylinder is 3/4") has a hydraulic advantage of 8.99:1 If you change the master to 1/2" you get a 20.28:1 advantage (which would require less effort but further brake handle travel) or if you use 2 of the 1/2" masters supplying individual brakes you get a 10.14:1 advantage which is a 13% better than factory and most likely a good combination. A single 5/8" master gives a 12.95:1 advantage. The factory brake handle gives a mechanical advantage of 8.93:1 so if considering a change in geometry this should be considered as well. I am toying with the idea of dual brake handles with 1/2" cylinders mainly because it would be easier than fabricating toe brakes.

Murray