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From: "Skip Slater" <skipslater@earthlink.net>
In response to the issue that Jim Scales brought up regarding ES brakes, today I spoke with Robbie Grove, owner of Grove Aircraft
Company, who I referred to in my post yesterday. I described the problem to him and he passed on the following info.
First, based on the part numbers I provided him, he told me that the Cleveland brakes supplied with the kits have 1 3/4" pistons
on the brakes. There are 2" pistons available that could increase pressure to the pads, but he said that a critical element in the
equation is the geometry of the brake pedals and the master cylinders, which dictate how much pressure gets to the brakes. If the
geometry is wrong, excessive pedal pressure will be required to get the desired braking. The attached file is out of Grove's
catalog and illustrates how to check the geometry as well as the desired ratio of pedal travel to cylinder travel. Robbie told me
that about a 2:1 ratio is desired: i.e. for every unit the brake cylinder piston travels, the brake pedal should move twice as far.
If you don't have that ratio, you don't generate the needed hydraulic pressure on the brakes and adding brake shoe size or piston
size won't achieve the desired results.
I did a rough measurement on my ES and found that my pedal travel and cylinder travel are about the same, so my ratio is
approximately 1:1. Based on this finding (and it was a crude measurement at best), we may have a reason for the high pedal pressure
needed to stop our planes. A possible solution Robbie mentioned is drilling a new attach point for the cylinders closer to the
pivot point, yielding the desired ratio. I asked if he could take a look at my plane to determine if that was feasible and he said
he would when he has time. However since he just got a government contract to make a bunch of composite parts for some aircraft in
a limited amount of time, he's extremely busy for the next few weeks, so I don't know when he can do it.
At any rate, he said he'd be willing to look into the problem when he has time and make retrofit kits available if they're
needed. I'll make a new post when I get more info on this.
Skip Slater
N540ES
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