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Ag&Au · 12-03-2014, 01:24 PM

Quote:

Originally Posted by ROBERT CROSS

Can I have a KISS.....please.

Bob

Quote:

Originally Posted by Inland RV Center, In

As per your request.

Andy

Be Careful, he did not say where he wanted to be kissed.

Ken

SteveH · 12-03-2014, 01:41 PM

Quote:

Originally Posted by dznf0g

So air is now heavier that fluid?

I guess Dexter air is heavier than fluid..........

SteveH · 12-03-2014, 01:42 PM

I have ordered the 2lb residual valve. We'll see.

dznf0g · 12-03-2014, 02:31 PM

Quote:

Originally Posted by SteveH

I have ordered the 2lb residual valve. We'll see.

Let us know.....I'm struggling with 2psi X the surface area of the four pistons = how many pounds of apply force? What's the drag, heat buildup and wear factor. There are no balancing retraction springs on those pads/calipers.

J. Morgan · 12-03-2014, 02:37 PM

If at all possible bleed the actuator WELL before tightening the output line.

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

J. Morgan · 12-03-2014, 02:40 PM

A two PSI RPV should not cause any appreciable drag unless it is behind another 2 PSI valve already in place in the actuator, I seriously doubt there is one already in the actuator.

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

dznf0g · 12-03-2014, 02:45 PM

Quote:

Originally Posted by J. Morgan

A two PSI RPV should not cause any appreciable drag unless it is behind another 2 PSI valve already in place in the actuator, I seriously doubt there is one already in the actuator.

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

I'm not sure how to measure "appreciable drag" in terms of wear and temp, but if you think about it:

If the gravity force of a column of fluid in a street rod, whose MC is lower than the caliper, has enough "suction" to retract the piston and make a low pedal, then 2 psi will surely keep the pads in constant contact with the rotor, overcoming the retraction and gap between rotor and pad caused by normal hub/bearing/rotor runout. I'm not saying it's a bad idea....I'm just not sure it's worth the tradeoff for me.

ROBERT CROSS · 12-03-2014, 02:52 PM

Would not a Mityvac help?

Bob

dznf0g · 12-03-2014, 02:56 PM

Quote:

Originally Posted by ROBERT CROSS

Would not a Mityvac help?

Bob

No, Bob. No matter how hard the mighty vac pulls, it'll never pull the air from the top to the bottom of the inner caliper half, through the connecting line, in order to let it rise to the bleeder.

SteveH · 12-03-2014, 03:04 PM

Quote:

Originally Posted by dznf0g

Let us know.....I'm struggling with 2psi X the surface area of the four pistons = how many pounds of apply force? What's the drag, heat buildup and wear factor. There are no balancing retraction springs on those pads/calipers.

Rich,

All I know is you could not feel any drag on the wheels on the cars with them lifted off the ground and rolling them by hand. I did this many times aligning front ends. Actually, a semi-tight adjusted drum brake had more drag, as I remember.

dznf0g · 12-03-2014, 03:08 PM

Quote:

Originally Posted by SteveH

Rich,

All I know is you could not feel any drag on the wheels on the cars with them lifted off the ground and rolling them by hand. I did this many times aligning front ends. Actually, a semi-tight adjusted drum brake had more drag, as I remember.

OK, you're the guinea pig then?

SteveH · 12-03-2014, 03:09 PM

Quote:

Originally Posted by J. Morgan

If at all possible bleed the actuator WELL before tightening the output line.

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

J.M.

What I did the first time when I replaced the Actibrake with the Dexter was lifted the tongue of the trailer as high as I could get it, changed the unit, then bled the unit to the first junction in the brake line. Think it was at the "T", and the delay was no longer, or shorter than with the Actibrake.

I'll need to get a short section of brake line to install the valve.

SteveH · 12-03-2014, 03:10 PM

Quote:

Originally Posted by dznf0g

OK, you're the guinea pig then?

Been there many times, and I can take it.

Used to work with a guy that had a saying, "Nothing is ever useless, worst case it can be used as a bad example".

J. Morgan · 12-03-2014, 03:53 PM

Concerning the "no appreciable drag" with the 2 PSI RPV, I am with Steve, I think we both make this statement based upon experience using these valves on different vehicles.

I currently own two vehicles that have RPVs that I installed.

Experience does build knowledge.

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

dznf0g · 12-03-2014, 04:04 PM

Quote:

Originally Posted by J. Morgan

Concerning the "no appreciable drag" with the 2 PSI RPV, I am with Steve, I think we both make this statement based upon experience using these valves on different vehicles.

I currently own two vehicles that have RPVs that I installed.

Experience does build knowledge.

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

I'm not fightin' you.. I have no experience working on anything with the MC lower than the caliper. BUT, I'm not sure the actuator isn't slightly higher than the calipers on the AS.....in my minds eye, as it's not here to really look at.

SteveH · 12-03-2014, 04:24 PM

Quote:

Originally Posted by dznf0g

I'm not fightin' you.. I have no experience working on anything with the MC lower than the caliper. BUT, I'm not sure the actuator isn't slightly higher than the calipers on the AS.....in my minds eye, as it's not here to really look at.

Rich,

My actuator is mounted in the tool box behind the propane bottles, and it's output is about level with the belly of the trailer. If the calipers are below this level, it's not by much.

And then if you figure full braking pressure is 1600 PSI, what is 2 PSI in this setting, something like .0000125% ?

In my mind I'm trying to reduce the time it takes for the actuator to build pressure to the point that braking starts.

dznf0g · 12-03-2014, 04:35 PM

Here's what is bothering me. 2psi in the line results in 11 pounds of pressure on each pad and 22 pounds of pressure per caliper. On a single piston system, I can see where, after actuator release, normal runouts will push the piston inward in it's bore, overcome the 2psi very briefly and displace a tiny bit of fluid back to the actuator reservoir. You then have zero psi in the line, an appropriate small gap between the pad and rotor, no further drainback (due to the residual valve) and life is good.

With a four piston system, it seems to me that the runouts will just transfer fluid between the caliper halves, not overcome the 2psi "pop-off" and you will always have 22 pounds of pressure (give or take for slight thickness variation around the circumference of the rotor) on the pistons. Maybe the tiniest thickness variation is enough? What am I missing?

dznf0g · 12-03-2014, 04:41 PM

Quote:

Originally Posted by SteveH

Rich,

My actuator is mounted in the tool box behind the propane bottles, and it's output is about level with the belly of the trailer. If the calipers are below this level, it's not by much.

And then if you figure full braking pressure is 1600 PSI, what is 2 PSI in this setting, something like .0000125% ?

In my mind I'm trying to reduce the time it takes for the actuator to build pressure to the point that braking starts.

I get that. We are assuming that the system is draining back, pulling the pistons in some and that is why the apply time is lagging, right? Sort of the actuator version of having to depress the brake pedal further down like in the street rod example.

All of that has nothing to do with if and how much a residual 2psi in the line during actuator rest, or just running down the road, affects brake drag.

SteveH · 12-03-2014, 04:57 PM

Quote:

Originally Posted by dznf0g

I get that. We are assuming that the system is draining back, pulling the pistons in some and that is why the apply time is lagging, right? Sort of the actuator version of having to depress the brake pedal further down like in the street rod example.

All of that has nothing to do with if and how much a residual 2psi in the line during actuator rest, or just running down the road, affects brake drag.

I suppose we will see.

SteveH · 12-03-2014, 05:29 PM

Quote:

Originally Posted by dznf0g

Here's what is bothering me. 2psi in the line results in 11 pounds of pressure on each pad and 22 pounds of pressure per caliper. On a single piston system, I can see where, after actuator release, normal runouts will push the piston inward in it's bore, overcome the 2psi very briefly and displace a tiny bit of fluid back to the actuator reservoir. You then have zero psi in the line, an appropriate small gap between the pad and rotor, no further drainback (due to the residual valve) and life is good.

With a four piston system, it seems to me that the runouts will just transfer fluid between the caliper halves, not overcome the 2psi "pop-off" and you will always have 22 pounds of pressure (give or take for slight thickness variation around the circumference of the rotor) on the pistons. Maybe the tiniest thickness variation is enough? What am I missing?

OK, I re-read your post above and I don't understand it. I don't understand how you have computed that 2PSI in the line computes to 11 pounds on each pad. In my thinking, pressure is pressure anywhere in the system, kind of like kinetic energy, or voltage on a wire. Measure the voltage any where on the wire, assuming no high current, the voltage is the same.

I would also think that 2PSI applied to a hydraulic system would be 2PSI anywhere in the system. No?