Poor braking action with Black Max wheels and Brakes

[dunc]

I have replaced my stock Silverlight AR-1C skinny wheels with the optional Black Max BX-1500 wider wheels and dual caliper brakes. Hoping to do some non-paved runways soon next month.

I am quite certain all air is bled from the brake lines as the handle is quite firm on the first squeeze. However the brakes do not hold when above 2600 RPM which is required to achieve the nominal 200 RRPM prior to starting takeoff roll. I have tried bleeding both from the top and bottom, and thoroughly cleaned pads and rotor.

Does anybody have further suggestions?

 

[Brent Drake]

They might still have air in them. Did you try to bleed the air backward?

 

[dunc]

Yes. Pressure feed at caliper, remove excess fluid at master cylinder.

 

[Aerofoam]

I had to do that, then pump from the MC in the front with an oil can while closing the bleeder on the MC.
A second person would have made it easy....

 

[gyroplanes]

If the handle is firm, you do not have sufficient air in the system. Is this a complete set? master cylinder and calipers? The master cylinder may be too large and not providing the PSI to reach best braking power.

 

[dunc]

Aerofoam: What bleeder on the MC? I am confused with your explanation.

Tommy: "insufficient air in the system??" I thought NO AIR was ideal? I am using the AR-1 master cylinder, unknown manufacturer.

 

[Sv.grainne]

What orientation are the calipers

Aerofoam: What bleeder on the MC? I am confused with your explanation.

Tommy: "insufficient air in the system??" I thought NO AIR was ideal? I am using the AR-1 master cylinder, unknown manufacturer.

No air in the system, period.

 

[Sv.grainne]

I'm using the Gyro Technic wheels/brakes and even though I have 2 pads per wheel cylinder they hold rock solid. Have only been to 3500rpm with unchocked wheels but no creep.

Sounds like full hydraulic not in play, air in the system? 4 pads you should be planted in place.

Bobby

 

[dunc]

I'm using the Gyro Technic wheels/brakes and even though I have 2 pads per wheel cylinder they hold rock solid. Have only been to 3500rpm with unchocked wheels but no creep.

Sounds like full hydraulic not in play, air in the system? 4 pads you should be planted in place.

Bobby

I have never been much past 3000 RPM without creeping. Images from my installation attached.

 

[Sv.grainne]

Can't tell for sure but have you put the bleed.screw in the topmost hole? The fluid hose should go in as low as.possible and.bleed should be at the top. Otherwise you can't get the.last few air bubbles out of the system.

You should be able.to lock the Gyro to the ground with these brakes.

 

[Aerofoam]

It's probably apples to oranges, but on the brake master cylinder( MC) on my Air Command (AC)
there is a bleeder at the pedal.
I had to bleed the MC by loosening the brake line at the MC while pumping and holding pressure from an oil can at a rear wheel.
Then tighten it while holding pressure and then repeat while holding pressure from the bleeder on the MC.
I had to go around the gyro a couple times chasing bubbles and do the MC last.
Royal PITA!!!!
The clear lines helped as I could see the offending air as it mocked me.....

 

[Abid]

Master cylinder is Matco 4GH.

MASTER CYLINDER, Short, MC-4GH - Matco Aircraft Landing Systems

MASTER CYLINDER, Short, MC-4GH

matcoals.com

It connects to a MC remote reservoir and the system will self heal. There is no "bleeder" on it.
Rob, this system will start to allow the wheels to roll slowly at 2600 RPM. The wheels are 6 inches and the brake rotor is smaller compared to standard 8 inch wheels. That is however ok. While pre-rotating if the gyro moves at 2 to 4 mph forward slightly. It doesn't have a big effect. Those tires are mainly for turf where resistance is much more than your paved runways.
If it bothers you Matco does make what they call an intensifier kit that can be installed into the MC.

 

[gyroplanes]

What orientation are the calipers

No air in the system, period.

A tiny bubble of air will compress and disappear and you will have full braking. I spent a lot of hours around Air Commands and almost all had little bubbles somewhere in the system. Some people like a little squeeze in the system.

 

[gyroplanes]

If you use a master cylinder from a different system, you may have wheel cylinders that have smaller pistons than the master was designed for, and the master cylinder piston may be too large for the caliper pistons.

 

[dunc]

Can't tell for sure but have you put the bleed.screw in the topmost hole? The fluid hose should go in as low as.possible and.bleed should be at the top. Otherwise you can't get the.last few air bubbles out of the system.

You should be able.to lock the Gyro to the ground with these brakes.

So you recommend bleeding from the bottom, upwards? I did that once, finding it required a LOT of pressure. I started at the lowest piston. Then tried bleeding top downwards, squeezing brake handle with caliper bleed screw cracked.

It's probably apples to oranges, but on the brake master cylinder( MC) on my Air Command (AC)
there is a bleeder at the pedal.
I had to bleed the MC by loosening the brake line at the MC while pumping and holding pressure from an oil can at a rear wheel.
Then tighten it while holding pressure and then repeat while holding pressure from the bleeder on the MC.
I had to go around the gyro a couple times chasing bubbles and do the MC last.
Royal PITA!!!!
The clear lines helped as I could see the offending air as it mocked me.....

Clear brake lines might be a big help. A brake pedal, rather than a squeeze bar, would work better too! I liked my old RAF setup which also used a brake pedal.

 

[dunc]

Master cylinder is Matco 4GH.

MASTER CYLINDER, Short, MC-4GH - Matco Aircraft Landing Systems

MASTER CYLINDER, Short, MC-4GH

matcoals.com

It connects to a MC remote reservoir and the system will self heal. There is no "bleeder" on it.
Rob, this system will start to allow the wheels to roll slowly at 2600 RPM. The wheels are 6 inches and the brake rotor is smaller compared to standard 8 inch wheels. That is however ok. While pre-rotating if the gyro moves at 2 to 4 mph forward slightly. It doesn't have a big effect. Those tires are mainly for turf where resistance is much more than your paved runways.
If it bothers you Matco does make what they call an intensifier kit that can be installed into the MC.

Thanks Abid! Will check that URL. Are the calipers compatible size-wise?

 

[Abid]

If you use a master cylinder from a different system, you may have wheel cylinders that have smaller pistons than the master was designed for, and the master cylinder piston may be too large for the caliper pistons.

That is true and these are different. I was not about to redesign the whole AR-1 just to fit bigger wheels. At the time wheels for these tires were a pain to get. Shortages due to Covid. BlackMax had them in stock. Matco had a 4 month lead time.
Matco does sell an intensifier kit for MCMC-4GH which can help. My ex-partner Larry uses this combo on his trikes. I test flew this system. It moved very slightly at first, getting better as I used it more (some air that self healed in a few hours). I did not have too much problem keeping it stationary while I reached 180 RRPM for normal takeoff. A slight creep forward on paved tarmac is ok. These wheels are meant to be used mainly for grass where they will not move forward at all till much more power is given.

 

[Sv.grainne]

Look at your photo, move the hose to the lower hole and the bleed screw to the top or as near as you can to the top. Your fluid hose appears to be higher than the bleed screw. You will NEVER get all the air out when connected in this fashion.

 

[Abid]

Thanks Abid! Will check that URL. Are the calipers compatible size-wise?

Well they are compatible in the sense that they did not move with me using them but I may have more strength in my guitar playing left hand than you and others. Larry says he uses the intensifier kit always with that MC and these wheels and brakes. However, Larry's pedal geometry is poor. George at Matco is not a fan of his own intensifier kit because according to him using it requires a very well bled system. I think everything requires a pretty well bled system but he discouraged using it. You could try getting the intensifier kit by calling Matco and talking to George about the intensifier kit for MCMC-4GH.

 

[Aerofoam]

So you recommend bleeding from the bottom, upwards? I did that once, finding it required a LOT of pressure. I started at the lowest piston. Then tried bleeding top downwards, squeezing brake handle with caliper bleed screw cracked.

Clear brake lines might be a big help. A brake pedal, rather than a squeeze bar, would work better too! I liked my old RAF setup which also used a brake pedal.

Yes, ultimately I bled from the front to back, high to low, but couldn't purge the big bubble at the MC in front, so I went back around to the RR brake and started backwards, it would have been very easy with someone to hold pressure on the oil can while I cracked the line, then the bleeder, but I had to play twister and do it myself....
I think with the hand brake, going backwards will consolidate the bubble up high in the MC then you should be able to purge it while bleeding either the line at the cylinder, or just pulling the brake lever to let it back flow to the reservoir.
Get someone to help......
My oil can would actually pull air into the system if I let off on the trigger......