Hydromax and a GMC motorhome

Testing on a fixture like the dash Sue is my foot model/pedal pusher Front pressure on the coach with 80mm calipers Rear pressure on the coach 80mm mid and 66mm rear calipers

Under construction and pivot points

Booster adapter

original clevis connection with rubber bush

O ring boss adapter for remote reservoir

pressures at maximum

Method to measure pedal pressure

Test rig with 1 square inch area air cylinder

Angularity check

Observed pedal force and output pressure

hood clearance

Dash protrusion

F-250 reservoir and remote adapter

Additional pump and fourth pulley

Long pilot oring adapter fitting for Hydromax

The Hydromax takes a "long pilot oring" connection for the hydraulic input. I could only find short pilot fittings for hydraulics. Any long pilot fittings found were for refrigeration service. I didn't want to try and buy a OEM hose and adapt it to the hydraulic pump I already had. I set out to make an adapter fitting to get to a common oring boss connection and go from there.

Started with 1.25" 12l14 hex stock and made the oring boss

Measuring threads using three wire method, first time for me with this.

Adapter assembled on Hydromax. Long pilot oring to female oring boss to a 90 degree JIC flare.

GMC Motorhome brake booster comparison OEM vacuum, Hydroboost and Hydromax

 

Top to bottom Hydromax, Hydroboost with 40mm master, and OEM Vacuum booster

OEM vacuum booster

Hydroboost with 40 mm master cylinder

Hydromax with 2" master cylinder

http://1999southwind.com/DOWNLOAD/Bosch%20HydroMax%20Booster%20Manual.pdf

Hydromax manual link

Brake pressure from Hydromax

2" Hydromax master with reservoir removed. Built like a "P30" master

Booster poppet valves

Hydromax master at assembled length. Volume ratio between sections 1 to 1

Hydromax rod does come out and a few styles are available or make what you want. New grommets are available.

Hydromax is different than Hydroboost in that the hydraulic flow path can have no restriction on the outlet, not a power beyond deal. Need a separate engine driven pump on the GMC or some kind of dual section pump. Relatively huge volume from the large master should satisfy all disk brakes with big pressure. Backup electric pump on primary flow failure.