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Note: Until Further Notice, do not use these cylinders in applications with two pairs of brakes (pilot and copilot etc).
More information here: https://bearhawkforums.com/forum/saf...e-applications
In the early days Bearhawk folks mostly used long-shaft Gerdes master cylinders (A-110-10). They were abundant and cheap. Then when those got scarce around 2006 or so, folks started using a short shaft version, with a longer machined fork threaded onto the end (A-110-4). On our blue plane, I had two of each. The forks are a special Bearhawk part that Mark keeps in stock.
It seems we Bearhawkers have finally depleted the world's supply of surplus Gerdes cylinders, (or at least B&B's supply) so something needed to change.
Bob has designed a new machined master cylinder, and while it is still in final testing, it is beautiful. First, here is a long-shaft Gerdes next to Bob's new one:
IMG_20220113_095459090.jpg
Another view:
IMG_20220113_095502949.jpg
Notice that the new cylinders are machined aluminum, vs the originals which were cast. Either works, but the bling factor is high on the new ones. The center shaft on the Gerdes is made from a very soft aluminum that is easy to bend while handling. On our blue Bearhawk I had to straighten a bent one, and one of the cylinders I removed from 303AP was also very bent. The new ones use a stainless steel center shaft which is much more durable.
Like the Gerdes, the new cylinder ports use 1/8 NPT thread, which allows for installation of an AN822-4D (90-degree), AN823-4D (45-degree), or AN816 (straight) fittings to connect to hoses. Also like the Gerdes, the threads on the shaft are 5/16x24 (fine thread) which means it's easy to find jam nuts made from aluminum, cad-plated steel, or stainless as you prefer. Bearhawk Aircraft has the machined forks that go on the end. Both ends have 3/16" holes for bolts or clevis pins, where the cylinders attach to the airframe and to the brake pedals.
More pics:
IMG_20220113_095703976.jpg
The above photo shows the Gerdes long shaft compared to the new cylinder. Note that the forks are longer. If you replace a short-shaft Gerdes cylinder with one of the new ones, Bob's design will be a drop-in replacement. If you'll be replacing long-shaft cylinders, you'll also need a set of the longer forks but can reuse your old jam nut. Bob prefers aluminum nuts, because, as you would expect, they are lighter. They are serving a very minor strength role here, and primarily just keep the shaft from rotating and to keep the threads from wearing. The Gerdes cylinder in the picture is missing a jam nut, but don't call Vic Syracuse, it wasn't in service like that! I was in the process of swapping the hardware over when I realized I should probably get a picture. The photo shows a zinc-plated jam nut but new aluminum nuts are enroute as I type.
IMG_20220113_094424392.jpg
Above: Notice that the top cap is retained by a snap ring. So like the Gerdes, these are field-rebuildable with off-the-shelf o-rings.
IMG_20220113_094915274.jpg
Look at this machined end!
The new cylinders have been flying in 619MS (the prototype Bearhawk Five) and in Mark Goldberg's Patrol, which is currently getting some travels thanks to Peter Brown. The cylinders have performed well in a wide range of ambient temperatures. They have not yet been subjected to many years and hundreds of hours of use, but there's no reason to doubt that they will provide excellent service life.
The initial test batch was of less than a dozen cylinders, but the first big production batch is underway now. If you have an urgent need and are ready for some right away, reach out to Mark Goldberg (512-626-7886). If you'll need some later this spring, there should be plenty to go around. I have installed a set on 303AP and look forward to testing them as soon as it is ready to fly again.
IMG_20211231_142007298.jpg
Here is a link to the 2006 Beartracks article that talks about using the short shaft Gerdes instead of the long shaft:
And here is a link that talks about how to rebuild the Gerdes cylinders:
More information here: https://bearhawkforums.com/forum/saf...e-applications
In the early days Bearhawk folks mostly used long-shaft Gerdes master cylinders (A-110-10). They were abundant and cheap. Then when those got scarce around 2006 or so, folks started using a short shaft version, with a longer machined fork threaded onto the end (A-110-4). On our blue plane, I had two of each. The forks are a special Bearhawk part that Mark keeps in stock.
It seems we Bearhawkers have finally depleted the world's supply of surplus Gerdes cylinders, (or at least B&B's supply) so something needed to change.
Bob has designed a new machined master cylinder, and while it is still in final testing, it is beautiful. First, here is a long-shaft Gerdes next to Bob's new one:
IMG_20220113_095459090.jpg
Another view:
IMG_20220113_095502949.jpg
Notice that the new cylinders are machined aluminum, vs the originals which were cast. Either works, but the bling factor is high on the new ones. The center shaft on the Gerdes is made from a very soft aluminum that is easy to bend while handling. On our blue Bearhawk I had to straighten a bent one, and one of the cylinders I removed from 303AP was also very bent. The new ones use a stainless steel center shaft which is much more durable.
Like the Gerdes, the new cylinder ports use 1/8 NPT thread, which allows for installation of an AN822-4D (90-degree), AN823-4D (45-degree), or AN816 (straight) fittings to connect to hoses. Also like the Gerdes, the threads on the shaft are 5/16x24 (fine thread) which means it's easy to find jam nuts made from aluminum, cad-plated steel, or stainless as you prefer. Bearhawk Aircraft has the machined forks that go on the end. Both ends have 3/16" holes for bolts or clevis pins, where the cylinders attach to the airframe and to the brake pedals.
More pics:
IMG_20220113_095703976.jpg
The above photo shows the Gerdes long shaft compared to the new cylinder. Note that the forks are longer. If you replace a short-shaft Gerdes cylinder with one of the new ones, Bob's design will be a drop-in replacement. If you'll be replacing long-shaft cylinders, you'll also need a set of the longer forks but can reuse your old jam nut. Bob prefers aluminum nuts, because, as you would expect, they are lighter. They are serving a very minor strength role here, and primarily just keep the shaft from rotating and to keep the threads from wearing. The Gerdes cylinder in the picture is missing a jam nut, but don't call Vic Syracuse, it wasn't in service like that! I was in the process of swapping the hardware over when I realized I should probably get a picture. The photo shows a zinc-plated jam nut but new aluminum nuts are enroute as I type.
IMG_20220113_094424392.jpg
Above: Notice that the top cap is retained by a snap ring. So like the Gerdes, these are field-rebuildable with off-the-shelf o-rings.
IMG_20220113_094915274.jpg
Look at this machined end!
The new cylinders have been flying in 619MS (the prototype Bearhawk Five) and in Mark Goldberg's Patrol, which is currently getting some travels thanks to Peter Brown. The cylinders have performed well in a wide range of ambient temperatures. They have not yet been subjected to many years and hundreds of hours of use, but there's no reason to doubt that they will provide excellent service life.
The initial test batch was of less than a dozen cylinders, but the first big production batch is underway now. If you have an urgent need and are ready for some right away, reach out to Mark Goldberg (512-626-7886). If you'll need some later this spring, there should be plenty to go around. I have installed a set on 303AP and look forward to testing them as soon as it is ready to fly again.
IMG_20211231_142007298.jpg
Here is a link to the 2006 Beartracks article that talks about using the short shaft Gerdes instead of the long shaft:
And here is a link that talks about how to rebuild the Gerdes cylinders:
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