Some photos of the Hand Made CNC Machined Rack and Pinion that we had to manufacture for our truck.
It was disappointing to find that all the power steering racks on the market, (Howe, Proam, Fortin etc...) were not suitable for a 4WD vehicle. Either they rotated in the wrong direction, the shaft was in the wrong place or some other restriction. I see I am not alone - after much investigation I learned that a lot of the CORR4 trucks (now known as Lucas Oil Series??) were running buggy racks via Pulleys and a Rubber Toothed Belt) with uni joints running in a hundred different directions and I notice that most of the 4X4 race trucks I have seen (Not many mind you) have not been able to use the Ram/Racks that were designed for a 2WD buggy or TT.
Another thing that completely amazed me was that the Buggy Racks, all ran a steel sliding section that was completely exposed to dirt, mud, water and rocks. The TT and Buggy owners simply pump the steering box full of grease and the dirt sticks to the grease as it is quick pushed from the internal cavities and BOOM, sand paper/grinding paste.
A steel rack section, moving in a an aluminium slot in a steering box, with no seals and grease that is full of sand/grit is a complete design disaster -
my gosh, who thinks this stuff up?
I am amazed just how the manufacturers simply copy each other, year after year with NO innovations. Is it just me??
Steering a truck at 100MPH via a series of very pulleys lots and lots of uni joints and a rubber belt, with metal parts scraping in and out of a housing full of sand and grinding paste between the steel rack and the soft aluminium body just scared the hell out of me, so I made my own rack and ram combination. (I cannot afford to replace the rack every race like the BIG TT Teams)
The rack above has the shaft positioned opposite to the Buggy Racks to allow the steering column to pass over the diff housing with minimal uni joints.
The rack we manufactured is COMPLETELY sealed with no exposed parts that will drag dirt in and out. The massive loads are placed directly on the RAM and the steering rack is only a Servo Mechanism.
The Ram would have been too long to have no bump steer, so we simply made the ram hollow and made some spherical ball joints that allowed the steering arms to fit inside the ram, effectively making the distance between the joints shorter.
Wow, when I started building the truck, I was not expecting to have to make my own ram, rack, housing and spherical joints, but you have to do what you have to do to get what you want in the end.
Some of the parts we had to make.
We tried all sorts of pumps, steering heads and could never get the steering to respond rapidly at low engine revs.
After many many spreadsheets, it was apparent that the commercially available components were not going to work for us.
For example, the INDUSTRY standard for spinning a steering wheel in any direction is Two (2) Revolutions Per Second, yet so many buggy drivers I spoke to are experiencing PUMP CATCH at low engine revs. Do yourselves a favour - grab your passenger car steering wheel and spin it as fast as you can back and forth and see how fast your vehicle manufacturer has designed the steering system to be operated at.
I explain Pump catch as this: When you attempt to rotate the steering wheel faster than the pump can provide fluid to move the steering ram, the ram cannot move fast enough to move the rack/box to your new "desired steering wheel position" and the torque shaft in the steering head is fully twisted, the ports are fully open and the steering wheel is now trying to steer the vehicle with the limited strength of a human arm (The steering wheel appears to stop turning, you feel scared as hell that you are going to hit a tree or fly through the fence because the steering wheel will not turn) - that is my definition of pump catch.
The massive steering racks that are on the market have MASSIVE piston diameters, and I started doing all the calculations to see how fast the steering systems could react with the pumps that all the TT and Buggy guys could purchase in the USA. All my spreadsheets clearly showed that the steering components on the market would not allow for the same sort of steering wheel rotation speeds that a passenger car would provide.
I did not understand why guys in Australia were complaining of brand new buggies (Made in the USA with all the latest and greatest gear) that were fitted with the best and most expensive buggy racks and power steering pumps that would not steer quickly at low engine revs. Drivers were telling me that they regularly experienced pump catch at low revs, and they have all learned to accept it.
Bugger that I thought and I hit the spreadsheets again.
I wanted to be able to steer my truck as below:
Steering Wheel Rotation Speed - 2 Turns Per Second (I wanted to be able to flick it right and left quickly, like a speedway or WRC (Rally) vehicle.
Tyre Pressure 15PSI (we can deflate some of our vehicle deflate our tyres whilst driving)
One Turn LOCK TO LOCK
Left Lock to Right Lock in <0.5 Seconds (just like a CAR)
Engine Speed IDLE
Vehicle Sitting on Bitumen (Tyres are a bitch to turn when you have a 4000lb truck with 10-15psi in the tyres on a road surface)
Was that to much to ask?
Well it turned out to be very much above the ability of all the gear on the market that I could purchase. Sure the massive piston areas would provide enough power to pop a bead off a tyre, but the huge rams needed huge flows. A car has 3-4 turns lock to lock and small tyres. Snapping 37 or 39" race tyres left to right in 0.5 seconds on bitumen with 10PSI AT IDLE was my mission - and I was not going to stop until I figured it out.
I ended up designing a handful of different pistons and cylinders that provide alternate Piston Areas and started to measure the actual forces required to move my tyres left and right at high speed, whilst they were sitting on the ground. We uses a portable 3 Phase, Industrial Hydraulic Power pack and various piston sizes in my ram. The results were very surprising. The actual force required to move the wheels was quite low because we all use very long steering linkages at the wheel (dont we??)
After measuring the forces required to move my truck wheels, why anyone in a Buggy would use the massive ram/piston diameters that the manufacturers are selling is beyond my comprehension. With the engine in the back of a buggy, the weight on the front wheels is NIL and the power required to steer the tyres is minimal. Installing a HUGE ram is only asking for PUMP catch at low revs. Trucks like ULTRA4 and Mine require a bit more force, but really? 3" buggy rams? What pump can provide that sort of flow - read further..
With a HUGE industrial power pack providing gallons of fluid per second, my new steering ram was super responsive and powerful.
Happy with the flow and pressure required, I then fitted half a dozen different pumps (some from USA, some from Industrial applications) to my test rig and punched the flow rates and pressure graphs (the flow and pressure vary with revs, not all pumps can make full pressure at low revs due to internal losses/clearances) I quickly realised that it was Mathematically Impossible for the small car/truck pumps that are for sale in the USA Race Shops (Even those that have been modified for racing as they claim) to provide enough fluid to push those massive buggy racks back and forth at speeds ANY WHERE CLOSE to the OEM specs for cars and trucks let alone me need to move both wheels LOCK TO LOCK with a single turn at IDLE.
Why competitors put up with steering systems that have pump catch and cause a vehicle steering system to react slower than a passenger car completely amazes me, but hey, I thought racing cars needed bigger engines, better brakes and a fast responding steering system - am I wrong?
I will not name names, but guys there is a lot of BS in the power steering industry. I pulled each one appart and measured the port sizes and calcualted for myself the flow rates for different rotational speeds and no surprises, the pumps that are available for our sport (Ultra 4, TT, Class 1) would not provide sufficient flows to achieve the steering wheel rotational speeds I wanted at 1 turn lock to lock - and all the pumps would result in PUMP CATCH.
Solution, reduce the piston area to reduce the fluid flow needed? or start again to redesign what everyone else was doing to end up with what I wanted and not a compromise like others have seemed to settle for. Dont get me wrong, if you are happy lots of turns lock to lock, a bit of pump catch at low revs and and limited steering wheel rotational speed, go and buy the biggest ram you can find - it will provide enough power at your wheel to pop a tyre off the bead if you wanted to, but with power created by large ram piston areas comes velocity reductions in steering wheel revs. I am only trying to demonstrate that big rams need big flow and there are not any pumps that can keep up with your hands spinning the steering wheel fast if you have a rapid rack (1.5 turns lock to lock) and big rams.
I could indeed purchase MASSIVE pumps designed for Industrial Trucks - wow these trucks are all using some form of hydraulic pump, but the industrial pumps or truck pumps are limited in rotational speed and not suitable for petrol engines that vary in revs from 1000 RPM at idle to 9000 RP at redline. I was extremely disappointed to learn that I was not able to use a HUGE truck pump due to my engine rev range (The manufacturers simply talked me out of it). Industrial pumps are shown below - much much higher flows than car/truck pumps, but designed for constant revs and no internal pressure relief (Be careful here)
I ended up finding the perfect piston/ram/pump/pulley/belt combination size that allowed my wheels to be rotated back and forth with ONLY 0.2 seconds from Full Lock to Full Lock in the other directions AT IDLE with 1600PSI of pressure with 10PSI in the tyres, whilst parked on Bitumen.
An OLD video of the some of the testing we performed (this was close to our final solution, but not our final solution)
Proformance Rapid Response Steering Rack - YouTube
With only ONE turn lock to lock, this is pretty impressive to see live in action, but hard to describe on a forum. A 4WD Truck, with Double A Arm suspension, low centre of gravity, and a steering system that allows for rapid steering when drifting in corners was my dream and now it was becoming a reality.
Now with a HUGE pump, and one turn lock to lock and lots of fluid flying in and out of our cylinder we thought we cracked the problem. The truck was amazing to drive with FULL STEERING SPEED even at idle -
HOWEVER.
Unfortunately, the massive fluid flow created massive problems in other areas of the truck. The power steering pump was drawing so much power it kept destroying and ripping the teeth of my HTD belt. The fluid flow was so intense, that we were boiling even the best synthetic power steering fluids after a couple or hours of driving. The worst problem was the stupid CNC machined Billet Aluminium Power Steering reservoir that I purchased from a USA based race company.
The Billet Aluminium Power Steering Reservoir looked fantastic - t had a HUGE FRAM filter, huge SN ports, O ring seals - it looked great. The problem was that the bloody thing did not have any means of removing foam/air bubbles, it did not have a breather and it only held about a litre of fluid. no Breather? Are they kidding, what sort of engineering do these guys do when they design a part. As soon as the motor warms up the expansion in the lines, oil, seals, and foam will of course change the capacity. I guess this is the reason why radiators and power steering reservoirs have Hot and Cold levels guys (A message to teh manufacturer of this silly product). Anyhow, after we machined a vent into the reservoir the Foaming turned out to be the next biggest problem. Foam resulted in heat, which resulted in more heat - a circle that ended in tears every time we drove the truck hard.
After many frustrating test sessions, we threw the bloody reservoir in our bin and started to look at alternatives.
The reservoir that caused all our problems looked a bit like this one...
After many more calculations, testing and brain storming sessions (and a lot of coca cola for mental stimulation) we installed a 3 Gallon Peterson Dry Sump reservoir as our Power Steering Reservoir. Well Made Dry Sump Reservoirs (There are a few well engineered brands, and be careful there are plenty of cowboys also) allow the air on the oil (Foaming) to be removed. The oil enters the top of the reservoir in a circular motion (Like a cyclone filter) and then passes through a series of slotted discs to remove the air - long story, a good reservoir needs to remove the air and allow the pump to pump oil, NOT pump air.
We also fitted a HUGE oil cooler to keep the system cool.
It was interesting for us to learn that the LARGEST COOLER on our truck now is the Power Steering Cooler. (Yes, that is the PS cooler on the Right, the one on the left is the Rear Diff Cooler)
After more than 450 Hours of Phone Calls, Pulling pumps apart, Bench Testing, In Vehicle Testing, Calculations, Spreadsheets, Machining, 6 different pumps, 4 different pulley combinations I am happy with my final Cylinder Sizes, Piston Areas, Pump Flows, Pulley Speeds, reservoir size, ventilation, and de aeration. Whilst I will not publish my calculations online (After all the idiots that this forum seems to allow on it) if anyone wants to speak to me for advice, where NOT TO go to purchase PS gear, who really makes good stuff - please contact me and I am more than happy to share my experiences with you.
Another thing, I found that the steering heads (inline between the steering wheel and the rack) that everyone typically sells are simply using standard OEM, Delphi Power Steering internals from the "old" steering boxes from the 1960's to today that have had a few of the ports drilled out to get a bit more flow.
Would be nice to see a manufacturer step up to the plate and make a TRUE high flow steering head for our sport. Perhaps we will have to yet again make something from scratch?
Scott and the Team at Proformance in Australia (Aussie, Aussie, Aussie - OI, Oi, Oi)