Brakes for use with ABW 26" tires

[RDavidson 183]

Mike,

Thanks for the explanation and link!

[RDavidson 183]

Randy,

I noticed you put your brake calipers on the bottom of the wheel. I'm pretty sure this is because the back gear is angled back so far that the brakes have to go there? I have the same issue.

I was wondering if putting them in the front might be better? I've heard not to put them underneath in case you have a flat tire. I'm guessing you don't put them in the front because you might hit something with them?

What do you think?

Thanks,

Ron

[EDMO 1078]

Ron,

     What about putting them on the top?

EDMO

[RDavidson 183]

Ed,

The gear legs get in the way and hit the back of the caliper restricting their ability to float. If you put them on the front or bottom it sure makes removing them simple...

How much float room should be adequate? 1/4"?

By the way Ed, the brakes are great! I had to modify the mounting holes on the discs a little, but other than that the went right on! Thanks again!

[EDMO 1078]

Nothing wrong with mounting them on the front - whatever works.

Glad the brakes are working for you.

EDMO

[ChrisBolkan 130]

I had tire/caliper clearance issues with the 29 ABW's When running low pressure in the tires. If you can mount the calipers up/forward it will provide better tire clearance to calipers than mounting them down/back. With calipers up/forward clearance is maintained regardless of tire pressure.

 

Did that make sense?

[RDavidson 183]

Chris,

Absolutely...so you are avoiding the tire bulge at the bottom.

[ChrisBolkan 130]

yes and it became a problem for me when I really exercised the system at low tire pressures. I did not damage the tires, but I could see evidence of rubbing. I ended up using spacers to get the clearance because my landing gear was notched to carry the brake line. Your gear looks like it will work fine moving the caliper up and forward and running the brake lines down the front tube of the gear. On my Cleveland brakes, the back plate could be easily rotated to put the calipers in the better spot, but the brake tube slot in the gear did not align at all well.

[SuberAvid 617]

Ron,

 

I tried to put mine where I thought they were least likely to be damaged but on top might be better if you can make it work.  The Matco calipers are on the inside of the disc so don't stick out where they can scrape on the tire like the Cleveland calipers. Sounds like Chris has the best advice for those.

[akflyer 1427]

I talked to Matco yesterday and George got a good laugh out of me trying to stop the 30" airstreaks with the single pucks.  for 260 bucks they will send you a kit with new backing plates that allow you to put two single puck calipers on each wheel like the highlander has.  I figured while I am at it I will put new pads on my existing calipers and see how that does.  Just for shits and grins I plan on putting a pressure gauge on the end of one of the hoses just to confirm that I am getting enough pressure to the calipers with the updated pedals and the MCMC4D masters.

 

I filled the brakes from the caliper to the reservoir so there is no air in the system and the masters are nice and tight.  I was pushing on the pedals so hard that I hobbled around for 3 days after the flight due to a pulled hamstring

 

Using the MCMC4D masters I had to make some mods since they wont bolt on to the older style rudder bar on the Avids.  I don't have any pictures of it but I will try to draw something up to show what I had to do to make them fit.

 

Edit:  added drawing to help muddy the waters on installing the MCMC4D masters.

 

With the updated pedals having a lower mount point to get the correct leverage, I had to modify the clevis on the top of the master to make it as short as possible.  I also had to cut a few threads off the shaft of the master so it would not hit on the pedal mounting tab.  I ground off the corners of the pedal mount tab to give me more clearance as well.  The base of the master is rounded with holes drilled in it 90° apart.  I used a hack saw and cut down the center of the master to give me slot to slip over the mount tab on the rudder bar as the mount tabs on the rudder bar are too close together to just bolt the master on to it.  I had to make the slot about 1/4" deeper in the master as the hole drilled in the base of the master was flush with the bottom of the slot.

 

I will see if I can pull up a stock picture showing the base of the master so you can get a better visual on what I had to do.  It would be easiest to just cut one of the tabs off the rudder bar and move it out and not have to modify the master, but if its already in a flying plane and you don't want to pull out the rudder bar, modifying the master is your only choice.

 

 

 

mcmc4d install on avid.pdf

[akflyer 1427]

I think the MCMC4GH master would work better on the Avids with the updated pedals as it is shorter than the 4D master.  But you still have to deal with the rudder bar issue and slot the bottom of the master or move one mount tab on each of the rudder bars.

 

http://www.matcomfg.com/MasterCylinders-tp2-5.html

 

Link the Matco master cylinder page

 

[RDavidson 183]

Leni,

That $260 is for 2 plates? 1 for each side? Why so expensive? With the cost of machining equipment slowly coming down why do we have to pay so much for parts like these? Is it still liability? Shouldn't the "Experimental" part of our planes get rid of a lot of the liability?

I'm not slamming Matco, it is all aviation related companies. Sorry, rant is over.

Do you just tee the line into the first brake over to the second? Not a bad idea, I guess it would be a little more bulky of an install.

[akflyer 1427]

no its for 2 plates and two additional calipers and plumbing.  you then mount two calipers per plate and plumb them together to give you double pucks on each side.

[RDavidson 183]

Ok! That's more like it...

[marksires 484]

I think the MCMC4GH master would work better on the Avids with the updated pedals as it is shorter than the 4D master.  But you still have to deal with the rudder bar issue and slot the bottom of the master or move one mount tab on each of the rudder bars.

 

http://www.matcomfg.com/MasterCylinders-tp2-5.html

 

Link the Matco master cylinder page

 

The MC4G is the master cylinder I used when I remade my pedals to make the brakes work.  When I'm back in town (the end of May at this point), I'll take pictures of the new pedals/cylinders.  They work much better than the 'stock' Avid pedals with the MC5 cylinder.

Mark

[EDMO 1078]

I don't have the proper engineering words to explain this, but my comparison of the Matco internal disks and the Cleveland and Grove external disks indicates to me that the brake torque of the Cleveland and Grove has to be much greater than the Matco, considering the difference in leverage between a 2 inch radius for the Matco, and a greater, maybe 3 or 4 inch, radius for the external two.

I believe the MC and pad pressure are also greater on the Grove and Cleveland, but have no specs to prove this.

EDMO

[saskavid 47]

I think grove specifies 600 psi for thier ratings read it somethere probably kitplanes.Matco ratings are derived at 450 psi. Like I have said in the past the mc-4d the mc-4a the mc-4 setup in an avid all have the same leverage at the start 5.3 to 1. You go with a really short master and an extended clevis you start at 4.7 to 1. typical leverage under activation with an mc-4d should be 3.6 to 1 depending on rudder bar orientation.Shortness of the ram plays a part in leverage but it is the perpendicular distance ratio between vectors that are the true determining factor of leverage.I actually picked this up myself and verifed it with the content of George Happ's troubleshooting page.If I didn't have the leverage I claimed there is no way I could make the 600 psi I have demomstriated on the test stand.And matco's trougleshooting pages state anything over 600 doesn't do anything more just twists/flexes the bottom end.

MIke

[akflyer 1427]

Mike,

 

I am not sure what rudder bar you were using to start with, but with your pedals, it moves the pivot point to the right location to give me the leverage, but the 4D master was a 1/2" too long to bolt right in so I had to do some mods to make it fit. 

 

[saskavid 47]

Mike,

 

I am not sure what rudder bar you were using to start with, but with your pedals, it moves the pivot point to the right location to give me the leverage, but the 4D master was a 1/2" too long to bolt right in so I had to do some mods to make it fit. 

 

I've ran into this and it has to do with how the rudder bars are orientated .for my plane the rudder bars start paralell and the tops converge equal ammounts some people shift the tops forward compared to that and some have them pulled ahead or back towards the pilot.And that is were these length anomalies come into play I think.

Edited 4 May 2014 by Mikesk

[RDavidson 183]

One of my double puck calipers has both pistons stuck like Chuck! I got the other calipers pistons out by forcing air into the caliper. I tried it on this one and nothing happened. I tried soaking it in some WD-40, then some carb cleaner, and basically anything that eats corrosion, and they are still stuck!

Any ideas?

Has anybody tried drilling and tapping a shallow hole in the piston face, then threading a bolt in it to get some kind of turning force to break it loose?

Thanks,

Ron

[RDavidson 183]

I fixed the stuck pucks! I plugged the line end of the brake caliper then connected a grease gun to the bleed nipple. A few pumps later and the pucks started moving! Easy! I hope this helps the next guy, I was really worried I was going to have to ruin the pucks to get them out!

Thanks,

Ron