Trailer Brakes

[Heavymetal]

On May 8, 2017 at 10:15 AM, GeorgiaHybrid said:

I might be on the wrong side of this but I still prefer DirecLink. I can adjust the braking pressure in multiple steps and it brakes in proportion to the amount the truck is decelerating. Is the pressure applied with the BluDot system adjustable at all or is it just directly related to the truck airline pressure?

No need because it is totally proportional to the amount of pressure on the pedal just like your truck. Light pressure light brakes more pressure on the pedal more brakes. 

[NoDirectionHome]

Perhaps some clarification is in order.  The BluDot brakes in proportion (fixed ratio) to the pressure delivered to the truck air into the hydraulic master cylinder.  The DirectLink is adjustable as to what that ratio is.  The BluDot could be "tuned" with master cylinder changes or with a proportioning valve but not on the fly for road conditions from the cab.

[Heavymetal]

1 hour ago, NoDirectionHome said:

Perhaps some clarification is in order.  The BluDot brakes in proportion (fixed ratio) to the pressure delivered to the truck air into the hydraulic master cylinder.  The DirectLink is adjustable as to what that ratio is.  The BluDot could be "tuned" with master cylinder changes or with a proportioning valve but not on the fly for road conditions from the cab.

Gotcha

[GeorgiaHybrid]

Richard,

As noted above, BluDot is proportional to your truck but you have no idea how much pressure is being applied. You might only be going to 50% of it's available braking force.

You can't easily adjust the amount of braking force on the trailer compared to the braking force applied by the truck brakes.

If your trailer had commercial air brakes then yes, I would agree the braking force would be proportional to the truck.

[Heavymetal]

1 minute ago, GeorgiaHybrid said:

Richard,

As noted above, BluDot is proportional to your truck but you have no idea how much pressure is being applied. You might only be going to 50% of it's available braking force.

You can't easily adjust the amount of braking force on the trailer compared to the braking force applied by the truck brakes.

If your trailer had commercial air brakes then yes, I would agree the braking force would be proportional to the truck.

I had never thought of it that way but now I can see the control he is looking for. 

[Heavymetal]

9 minutes ago, GeorgiaHybrid said:

Richard,

As noted above, BluDot is proportional to your truck but you have no idea how much pressure is being applied. You might only be going to 50% of it's available braking force.

You can't easily adjust the amount of braking force on the trailer compared to the braking force applied by the truck brakes.

If your trailer had commercial air brakes then yes, I would agree the braking force would be proportional to the truck.

You know you have just caused me to install a gauge and move a camera to watch it while I observe my trailer braking. Sometime you guys sure cause me to have to work hard, I'm retired! I am suppose to be driving around enjoying myself but noooo you have to bring something up that will eat at my brain until I figure it out. There went the fishing trip! Lol

[Alie&Jim's Carrilite]

What brand master cylinder does Blue Dot use?  At full stroke what is the line pressure applied to the calipers?  What is the clamping force of the calipers - 2- 4 pistons?  

There should be a formula of applied air pressure to stroke length to applied fluid pressure to clamping force.  Now the more weight/momentum each "wheel" has to stop, the more pressure it needs.   Most of the heavier New Horizons use 2 Blue Dot systems so that the individual wheels have equal force applied.

[Heavymetal]

3 minutes ago, Alie&Jim's Carrilite said:

What brand master cylinder does Blue Dot use?  At full stroke what is the line pressure applied to the calipers?  What is the clamping force of the calipers - 2- 4 pistons?  

There should be a formula of applied air pressure to stroke length to applied fluid pressure to clamping force.  Now the more weight/momentum each "wheel" has to stop, the more pressure it needs.   Most of the heavier New Horizons use 2 Blue Dot systems so that the individual wheels have equal force applied.

Ok now you guys are just trying to make my head explode! I don't have any problems with my trailer braking but that's not good enough. I will have to start at the front and work my way through my brakes just so I know how every piece of the system works and if there is any adjustments that can be made for future reference. That's two fishing trips I'll miss. 

[GeorgiaHybrid]

Jim,

The BluDot actuator works with whatever master cylinder the trailer has, Dexter, Kodiak, etc. That is where my problem with BluDot starts. You have no idea of the pressure you can put on the system.

I can dial my DirecLink up to lock the wheels on a panic, push it to the floor stop and then back of a few steps. That way I get minimum stopping force at low G braking and maximum brake force when required.

I also gives me the option to dial back the brake force on the fly if needed due to road conditions.

[NoDirectionHome]

Quote

There should be a formula of applied air pressure to stroke length to applied fluid pressure to clamping force. 

Just for the record, stroke length has nothing to do with the force equation.  The formula is just pressure times the area's of the master cylinders and caliper pistons or wheel cylinders.

[Alie&Jim's Carrilite]

1 hour ago, NoDirectionHome said:

Just for the record, stroke length has nothing to do with the force equation.  The formula is just pressure times the area's of the master cylinders and caliper pistons or wheel cylinders.

 

True, But I'm looking at it from The Blue Dot piston that is connected to the master cylinder moves a total of XXX inches.  For today lets say 4 inches total at max application. So if I apply 15 pounds of air pressure to the truck brakes, theoretically, that should be 15 psi to the Blue Dot system, which moves the master cylinder piston XX amount of travel, which generates XX braking force. So if the piston travels a total of 4 inches at 60psi, then at 15 psi it should only move 1 inch which generates XX force.

Is the Blue Dot braking linear or is it a bell curve and are the systems matched to the application or are they generic?

While the Direct Linc lets you chose what you (we) feel is the correct braking force by using the skid test as David described, is this the best method?  

[Heavymetal]

11 hours ago, GeorgiaHybrid said:

Jim,

The BluDot actuator works with whatever master cylinder the trailer has, Dexter, Kodiak, etc. That is where my problem with BluDot starts. You have no idea of the pressure you can put on the system.

I can dial my DirecLink up to lock the wheels on a panic, push it to the floor stop and then back of a few steps. That way I get minimum stopping force at low G braking and maximum brake force when required.

I also gives me the option to dial back the brake force on the fly if needed due to road conditions.

The BluDot comes with its own master cyclinder. I will be putting together a gauge today to place inline to see how the pressure on the truck and RV differ if they do. 

[GlennWest]

As I understand, 100 psi yields 1500 psi brake pressure. I will have an RV-1 Bendix valve in mine so as not to over pressure my Kodiak's brakes. 

[Ronbo]

My first year with my direclink I went through a set of pads. I have since backed off on the breaking with no difference in stopping difference. I like that if I am on a road in freezing wether, I can decrease the trailer breaking on the fly.

[Jack Mayer]

Bludot is a 10:1 linear relationship.  That is from memory, but I have instrumented both the air and hydraulic pressures when working with Dexter and BluDot on a previous "problem"....which was not a real problem, only a change that was not documented and required two master cylinders to resolve. This is why New Horizons uses two master cylinders.....to get the volume required for the large Dexter disc's.