Magnum brake issues

[NorthIdahoAvidflyer 374]

The brakes on this Magnum are spotty at best. After removing the peddles it was discovered that there are two different Matco master cylinders. Same type with different rod lengths. This might explain the difference in braking from right to left. The bottom of the right master cylinder had been cut away to change the angle.  

Edited 27 Mar 2019 by NorthIdahoAvidflyer

[saskavid 47]

Well it looks to me like you don't have any fluid in the left master cylinder lines.Just from pictures hard to tell. The trick to making leverage is to get the activation shaft of the master cylinder as close to the brake pedal pivot point as you can. And by pivot point I mean the place where the brake pedal bolts to the rudder bar. leverage works as a function of perpendicular distance to the master cylinder centerline  of that brake pedal attachment point/ pivot point. On a non magnum avids with mc4 master cylinders all start with 5.3 to 1 leverage regardless of the length, assuming that they start with the activation shaft of the mc touching the back of the rudder pedal. The exception being the ultra short mc4g and such which have like 4.7, because the clevis contacts the rudder pedal not the shaft . With activation or when you step on pedal the longer the mc the more the leverage is reduced from that starting value. the original owner builder was probably modding on the pedals already somewhat but without a comparative picture hard to tell.

[NorthIdahoAvidflyer 374]

Yes, there is fluid in the lines it's just hard to see. I never understood why they use the small 1/8 inch lines on these. Seem like you would want the bigger lines to push a larger volume of fluid to the brake cylinders. 

Yes the peddles had been modified at least twice. Someone had cut the threads off one of the shafts and installed a longer clevis to make up the difference. The attachment points on the peddle have also been moved closer to the peddle which I assume was done to gain more leverage. I'm going to change out the cut off shaft, add a new clevis to match the other side, add a new body to one of the master cylinders to fix the ground off bottom mount and add the intensifier kits to both master cylinders.

When done I hope to have nice even braking from both sides and not have to worry about something falling off.

[saskavid 47]

They use the 1/8th inch lines over the 1/4 because the scale and ratio implies a gain in rigidity, less ballooning. In a conventional avid doesn't make or break the deal because it's difference as a function of percentage between the 2 isn't where force is gained or lost to an extent that it matters. I can wrap a 600 psi gauge with my planes setup and a 1/4 inch line. that is the limiting psi you need. Any more does nothing more to stop the plane. My personal preference for the lines to the mc's from the res would be 1/4 inch to facilitate more of a funnel effect getting fluid pressure to the calipers when everything is static.

[RDavidson 183]

Vance,

I don't want to poop on Matco because I haven't used them, but originally the Magnum used Cleveland everything.  I get that the cleveland stuff is crazy expensive and it makes Matco very attractive, but if you go big tire/bigger gear at anytime I think the clevelands are the way to go.

I could be wrong about matco, so don't through eggs too hard at me!  lol!

 

Ron

[NorthIdahoAvidflyer 374]

Vance,

I don't want to poop on Matco because I haven't used them, but originally the Magnum used Cleveland everything.  I get that the cleveland stuff is crazy expensive and it makes Matco very attractive, but if you go big tire/bigger gear at anytime I think the clevelands are the way to go.

I could be wrong about matco, so don't through eggs too hard at me!  lol!

 

Ron

Ron, The plane does have Cleveland calipers on the wheels. I just got the parts to fix the Matco MC and I purchased the intensifier kits also. I will run this and see if it helps and if it doesn't or if I switch to larger tires I will look for a set of Cleveland MC.  I always appreciate your input. 

[akflyer 1427]

I have matco masters and Cleveland double pucks on mine and can lock them up easily.  I also have the pedals from saskavid and they made a huge difference getting the leverage correct to put the pressure to the calipers.

 

[RDavidson 183]

Word...