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[Pulsar-Aviators] Hydraulic Brake Options

 
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ronko(at)att.net
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PostPosted: Mon Jan 17, 2011 11:44 am    Post subject: [Pulsar-Aviators] Hydraulic Brake Options Reply with quote

From: Ron Koval <ronko11(at)yahoo.com>
To: Pulsar-Aviators(at)yahoogroups.com
Sent: Mon, January 17, 2011 1:36:03 PM
Subject: Re: [Pulsar-Aviators] Hydraulic Brake Options
Disc Brake Pulsars Owners:

The responses sharing experiences with brakes on our Pulsars has been a great learning experience for me.
 
I need to ask those that have disc brake systems a question. Previous to owning a Pulsar, I owned a Grumman Cheetah that has a castering nose wheel, differential steering and braking with hydraulic brakes, with gross weight of 2200lbs. To the best of my memory, I don't ever remember experiencing brake fade, a manufactured a/c may have twice the brake it needs for safety margin. When I had new brake pads installed, the mechanic gave me specific instructions, to glaze the brakes. Two to three passes of his 4000' runway, applying the brakes heavily to build up heat and glaze the pads. He noted, you know you are done when at the end of the second or third pass, while maintaining your throttle, you still increase braking power significantly. He also noted that brakes need to be used enough to produce enough heat to maintain this glazing, so don't baby them with long roll outs.

Do you Pulsar owners with Matco and other disc brake, do this glazing process on a new set of brake pads?

In advance, thanks again for your valuable feedback.

Ron


From: Peter Walker <peterwalker58(at)yahoo.com>
To: Pulsar-Aviators(at)yahoogroups.com
Sent: Mon, January 17, 2011 4:07:18 AM
Subject: Re: [Pulsar-Aviators] Hydraulic Brake Options


Hello Brakes and everything in life is a compromise The trick is picking the one that works for YOU
A Pulsar is a fairly slippery bird and lands normally on paved runways with little rolling resistance Your main concern is stopping from speed in a controlled and consistent manner Once per flight Pads don't make heat They convert kinetic energy to heat High friction pads only convert it faster by reducing the time and distance
As for the difficulty in locking up the brakes (mag check?) its possible you are suffering knock off where the pads are knocked open by the wheel rocking because of freeplay or warped discs You then lose much of the cylinders stroke just taking up slack You may also might be using hoses with too low a pressure rating that swell when under pressure
BTW I worked with brakes too
Peter



--- On Mon, 1/17/11, Keith Palmer <kdpalmer(at)mweb.co.za> wrote:
[quote]
From: Keith Palmer <kdpalmer(at)mweb.co.za>
Subject: Re: [Pulsar-Aviators] Hydraulic Brake Options
To: Pulsar-Aviators(at)yahoogroups.com
Cc: pulsar-list(at)matronics.com
Date: Monday, January 17, 2011, 8:00 PM


 Hi Dre,
  No I did not use O'briens system so I don't know what they can offer.
  But I was in the braking game ( years ago ) where we designed brakes for different applicatios from the motor industry (racing cars to heavy trucks) to drag brakes for mine hoists & winches. It is a very technical subject and brakes are normally designed  for a very specific function and is always a compromise when you need say a drag brake (for slowing over a long period) and an emergency brake (for stopping quicky within seconds). In simplistic terms,  In the first instance you need a Low friction material, with a big contact area, using a low pressure system, so as not to generate excessive heat and burn the lining out, In the second instance for quick stopping you need High Friction Material and high pressure for your quick stopping, remember energy converts into heat so you can't have a long application of the brakes without fade or burn out of the lining in this instance.
  Now with the Pulsar nose wheel you are steering and braking, ie in a compromise situation at each end of the scale because you want a Drag brake for steering and an emergency brake for stopping, So you have the choice of light weight band brake or a heavier disc brake system , both have there compromise situations. so you must fly accordingly to what you have installed, so as not to extend the limits of thier weakest features.
  I went for the light drag drum brake and taildragger config for steering.
  I hope this helps with understanding some of the braking problems expressed recently. As mentioned this is a very technical subject and have been unable to give a full explaination in this short text, but I could try and answer some specific questions if necessary.

Keith


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kdpalmer(at)mweb.co.za
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PostPosted: Mon Jan 17, 2011 9:53 pm    Post subject: [Pulsar-Aviators] Hydraulic Brake Options Reply with quote

Ron, I will try and answer queries within your text :-


Disc Brake Pulsars Owners:

The responses sharing experiences with brakes on our Pulsars has been a great learning experience for me.

I need to ask those that have disc brake systems a question. Previous to owning a Pulsar, I owned a Grumman Cheetah that has a castering nose wheel, differential steering and braking with hydraulic brakes, with gross weight of 2200lbs. To the best of my memory, I don't ever remember experiencing brake fade, a manufactured a/c may have twice the brake it needs for safety margin.You are right they have used a low to medium friction material to avoid fade and burning but have given you a high pressure caliper (Heavy) which will give you better braking with this material When I had new brake pads installed, the mechanic gave me specific instructions, to glaze the brakes. Two to three passes of his 4000' runway, applying the brakes heavily to build up heat and glaze the pads. He noted, you know you are done when at the end of the second or third pass, while maintaining your throttle, you still increase braking power significantly. He also noted that brakes need to be used enough to produce enough heat to maintain this glazing, so don't baby them with long roll outs. When pads are made and baked they only get a crust on the surface ( like bread ) as they wear down they keep the mating surface crust baked hard, When you replace pads without skimming the discs you normally find the disc has a corrigated surface. So you need to bed the pads in ( Glaze ) as only the high ridges on the disc will touch the new flat pad and only the areas touching will act as a breaking surface could be down to 10% .And when they are bedded in (glazed) will they give you full mating and therefore braking. You should not let the discs get to corrigated as this increases the braking pad square area which will need more hydraulic pressure to get the same pounds per square inch to get the correct breaking pressure on the disc
Do you Pulsar owners with Matco and other disc brake, do this glazing process on a new set of brake pads?Best give a light skim if needed on your car and plane discs and go easy until bedded in

In advance, thanks again for your valuable feedback.

Ron
Hope this gives some ideas on the points raised.

Keith









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sonja.englert(at)juno.com
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PostPosted: Tue Jan 18, 2011 6:53 am    Post subject: [Pulsar-Aviators] Hydraulic Brake Options Reply with quote

The brake break in procedure you secribed is what we also do with new airplanes before the first flight. It does not take much: get up to 40 kts and apply brakes as heavy as you can to a stop, repeat two or three times. You notice how the stopping power increases. I think glazing is the word when you overdo it, then they do not work well anymore.

Sonja

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