Damn Brakes!!! / Seats

6 posts in this topic

Posted

I have been through every part of these brakes and the right brake will still not release after some taxi testing. I have figured out a few things.

1. My father had re-welded the upper Master Cylinder attachment point and they are setting at different lengths and angles. I will correct this geometry.

2. I have been hooking the system up and then bleeding from the Calipers up to the firewall mounted reservoir. At some point during the bleeding one side or the other will pressurize and stop taking fluid before fluid reaches the reservoir. I have been bleeding both sides back and forth until fluid fills the reservoir. After the system is filled I adjust the peddle clevises for a firm peddle. Here is where the problem starts. After taxiing the plane the brakes get warm, The fluid expands and the brakes lock up because I have the peddles adjusted to tight to start which does not allow the fluid to return to the reservoir thus compounding the problem as the fluid gets warm and expands. 

What's going wrong???? I have always had master cylinders with self contained reservoirs. You hook them up and pump fluid to them until it comes out he top. I believe I may be causing the problem by having the master cylinders hooked to the peddled during initial bleeding. If the peddles are depressing the master cylinder shafts even slightly this could be the reason why the system is pressurizing during bleeding. There is also a possibility that there is a restriction in the lines. I have a friend coming over to help me this week so hopefully we can get this taken care of once and for all. 

I hate the seating in the Magnum. They installed aluminum pans and have cushions. What are you guys doing for seating. I see pictures and it looks like lost other planes have nice seats?

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Posted

I have been through every part of these brakes and the right brake will still not release after some taxi testing. I have figured out a few things.

1. My father had re-welded the upper Master Cylinder attachment point and they are setting at different lengths and angles. I will correct this geometry.

2. I have been hooking the system up and then bleeding from the Calipers up to the firewall mounted reservoir. At some point during the bleeding one side or the other will pressurize and stop taking fluid before fluid reaches the reservoir. I have been bleeding both sides back and forth until fluid fills the reservoir. After the system is filled I adjust the peddle clevises for a firm peddle. Here is where the problem starts. After taxiing the plane the brakes get warm, The fluid expands and the brakes lock up because I have the peddles adjusted to tight to start which does not allow the fluid to return to the reservoir thus compounding the problem as the fluid gets warm and expands. 

What's going wrong???? I have always had master cylinders with self contained reservoirs. You hook them up and pump fluid to them until it comes out he top. I believe I may be causing the problem by having the master cylinders hooked to the peddled during initial bleeding. If the peddles are depressing the master cylinder shafts even slightly this could be the reason why the system is pressurizing during bleeding. There is also a possibility that there is a restriction in the lines. I have a friend coming over to help me this week so hopefully we can get this taken care of once and for all. 

I hate the seating in the Magnum. They installed aluminum pans and have cushions. What are you guys doing for seating. I see pictures and it looks like lost other planes have nice seats?

Is your remote firewall reservoir vented / plugged vent?? It needs a very small vent and sometimes it gets plugged with old dirty oil?

Just a thought....

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Posted

I remove the cap when bleeding, have checked the small vent hole and make sure the washer is under the mount when re-installed. All seems good.  Thanks for the input.

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Posted

As you press on the brake, the firstpart of its motion locks flow so the pressure acts on the caliper. In other words, the brake cylinder at the pedal will not release the flow to the reservoir until the pedal is pulled back all the way. If your rigging doesn't let the pedal relax fully, the flow will stop at the cylinder and not let fluid pass to the reservoir. Try pulling the pedal back forcibly and see if that opens up the flow.  

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Posted

As you press on the brake, the firstpart of its motion locks flow so the pressure acts on the caliper. In other words, the brake cylinder at the pedal will not release the flow to the reservoir until the pedal is pulled back all the way. If your rigging doesn't let the pedal relax fully, the flow will stop at the cylinder and not let fluid pass to the reservoir. Try pulling the pedal back forcibly and see if that opens up the flow.  

You are correct and when the brake locked up the second time unhooking the peddle relieved the pressure. This tells me that I still have issues with my adjustment or geometry. I am going to do some measuring this evening. My dad had changed the upper arms and I have a sneaking suspicion they are not placed in the correct orientation.

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Posted

Brake update: After correcting the peddle geometry a flying/mechanic friend of mine met me at the hangar and we went through the brakes system. We started by pushing fluid up the lines to make sure the lines were clear to the bottom of the master cylinders. With the peddles unhooked from the master cylinders we were able to push fluid easily clear to the reservoir. We bled the system and hooked up the peddles. After some taxi testing and adjustment its amazing how much better it's working. 

I have always had master cylinders with self contained reservoirs. I learned that you have to bleed the two types differently. 

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