SIMEXSLAVE Posted March 21, 2009 Share Posted March 21, 2009 J999dpt - how do you plan on balancing the hydraulic and mechanical part of the steering? Even if you can get the turns to lock to match the ram is turning linear motion into rotary motion and the mechanical system is all rotary so the movement won't be balanced. This was the reason I ditched this idea and looked for another solution. The way a PAS steering valve and a hydraulic steering control valve work are very different!Like you I wanted to remove the issue of the Rover PAS box which isn't up to what we want to do to it. Even with the sort of work Simexslave has had done you don't get that much steering force (and if you did then you'd just break LR TREs) and modifying them for hydro assist only has reasonable results - you can't flow enough fluid at a high enough pressure IMHO. I ditched the idea of going to Howe for a system like filthyboy's because it was very expensive and required the steering box be sent back and forth across the pond to get it set up. After a few nights of research I came across the Sweet steering valve and concluded they were ideal for the job - this is essentially a bigger, stronger version of the valve in the top of your PAS box but is remote mounted. This will take high fluid pressures and will flow fast enough to move a 3" OD ram as quick as the driver can steer on trophy trucks linked up with a quick ratio steering rack. Oh, and Rakeway sell them too so they're easy to get hold of B) HTHs Hi Will Just been looking at the sweet valves can you put them in line with the columb shaft or are they like an orbital valve ? Also which flow did you go for ? Quote Link to comment Share on other sites More sharing options...
will_warne Posted March 22, 2009 Share Posted March 22, 2009 Hi WillJust been looking at the sweet valves can you put them in line with the columb shaft or are they like an orbital valve ? Also which flow did you go for ? Yep, I got one of the in column valves - servo's they call them. I went for one of the standard sized valve with the lowest rated torsion bar (lightest steering). Quote Link to comment Share on other sites More sharing options...
SIMEXSLAVE Posted March 22, 2009 Share Posted March 22, 2009 Yep, I got one of the in column valves - servo's they call them. I went for one of the standard sized valve with the lowest rated torsion bar (lightest steering). Hi Will are you running a single ended double acting ram or a double ended unit ? Jon Quote Link to comment Share on other sites More sharing options...
will_warne Posted March 22, 2009 Share Posted March 22, 2009 I'll be running double ended, 80mm OD. Quote Link to comment Share on other sites More sharing options...
SIMEXSLAVE Posted March 23, 2009 Share Posted March 23, 2009 I'll be running double ended, 80mm OD. Thats the same ram as im using on my rear steering, theres no argument when you use it you just have to make sure the steering arms from the ram are upto the job. Quote Link to comment Share on other sites More sharing options...
will_warne Posted March 23, 2009 Share Posted March 23, 2009 Thats the same ram as im using on my rear steering, theres no argument when you use it you just have to make sure the steering arms from the ram are upto the job. Absolutely - arms will be a little on the HD side Quote Link to comment Share on other sites More sharing options...
j999dpt Posted March 24, 2009 Share Posted March 24, 2009 wicked good to know im not barking up the wrong tree. you gonna use rose jointed ends instead of tre's . Quote Link to comment Share on other sites More sharing options...
filthy boy Posted March 24, 2009 Share Posted March 24, 2009 Absolutely - arms will be a little on the HD side WIll Any ideas how you will get your system perfectly balanced? If there is any "mismatch" between the valve / ram / steering box you will get a feedback loop going with each component trying to correct to a different version of straight ahead. The Sweet type remote servo is more commonly used with rack and pinion where this problem seems not to arise. ALso worth looking at Woodward steering in the US. Tim PS the box doesn't actually fly the Atlantic 3 times, there is a way round that Quote Link to comment Share on other sites More sharing options...
will_warne Posted March 24, 2009 Share Posted March 24, 2009 WIllAny ideas how you will get your system perfectly balanced? If there is any "mismatch" between the valve / ram / steering box you will get a feedback loop going with each component trying to correct to a different version of straight ahead. The Sweet type remote servo is more commonly used with rack and pinion where this problem seems not to arise. ALso worth looking at Woodward steering in the US. Tim PS the box doesn't actually fly the Atlantic 3 times, there is a way round that Tim, I'm not expecting any problems but I'll have to wait and see. Given the nature of the valve the system should balance itself as it will only open when there is an unbalanced force at either end of the valve. At the end of the day the system isn't any different to a PAS steering box except the valve is moved up the steering column and the piston providing the assistance is moved outside the steering box.... If there is a problem with feedback the first thing I'd try would be a steering damper but I'll just have to wait and see if there are any issues. Quote Link to comment Share on other sites More sharing options...
simonr Posted March 24, 2009 Author Share Posted March 24, 2009 There is a dead band between the input and output shaft. It is the difference between these that operates the valve. The trouble is that when you turn the steering wheel, the orbital valve you have added will operate first and that will operate the ram which will pull the arm on the original steering box round. Because the input shaft of the original box has not moved yet, it's valve will be operated in the opposite direction - so it will be acting against the ram assist. I'm not sure you will get oscillation / feedback - but I think the steering will feel lumpy at small displacements / steering forces. It will be interesting to see what the effect is! My electric solution has moved a step closer. I have bought a pair of pressure transducers from eBay and connected them (using brake hose) to the steering box. This allows the transducers to be away from all the muck. The transducers spit out a voltage of 0 to 5v between 0 and 100bar. All i'm going to do us use a comparator to detect when the voltage is above a threshold then operate a valve. I'll post some piccies when the camera and steering are in the same place. Si Quote Link to comment Share on other sites More sharing options...
simonr Posted March 24, 2009 Author Share Posted March 24, 2009 I was just about to order a valve - then wondered.... I have a hydraulic pump intended for opening & closing gates. Instead of using a valve, it just reverses the motor. Do any of the electric/hydraulic pumps used on cars work that way? It would obviously me much simpler (and cheaper) than having to buy a valve too. Si Quote Link to comment Share on other sites More sharing options...
will_warne Posted March 24, 2009 Share Posted March 24, 2009 There is a dead band between the input and output shaft. It is the difference between these that operates the valve. The trouble is that when you turn the steering wheel, the orbital valve you have added will operate first and that will operate the ram which will pull the arm on the original steering box round. Because the input shaft of the original box has not moved yet, it's valve will be operated in the opposite direction - so it will be acting against the ram assist. I'm not sure you will get oscillation / feedback - but I think the steering will feel lumpy at small displacements / steering forces. It will be interesting to see what the effect is! I see where you're coming from however the valve won't open until there's some resistance coming back through the steering (assuming the resistance in the steering box is so negligible that the twist through the valve will not be enough to cause any fluid flow - I'm assuming there will be a few degrees of rotation in the valve before it opens due to the fact some steering effort is always required) so the ram won't start to move until the play in the mechanical system has been taken up and the steering starts to load up. Once it does then the ram kicks in until it cancels out the load on the steering. Again play shouldn't be an issue as the valve will no longer supply fluid once the threshold force has been reached and won't push through beyond this. This is how I think it should all work.... At the end of the day the only real difference between this system and a hydro assist using a conventional PAS box is that my steering box is not assisted which may remove some damping from the system. If I have an issue with it being fidgety or notchy I'll add a damper to the drop arm which should solve any issues. Quote Link to comment Share on other sites More sharing options...
SIMEXSLAVE Posted March 27, 2009 Share Posted March 27, 2009 I was just about to order a valve - then wondered....I have a hydraulic pump intended for opening & closing gates. Instead of using a valve, it just reverses the motor. Do any of the electric/hydraulic pumps used on cars work that way? It would obviously me much simpler (and cheaper) than having to buy a valve too. Si Hi Si The electric pump im using runs constantly and the pressure is directed by a proportioning valve, but i have also used a simple rocker switch to operate valves but this was an arse to use when theres loads going on in the cab, the proportioning valve duz give u a certain amount of feedback. I do only use this for the rear steering though so im not trying to balance two systems ,but what you were saying about the torsion bar /valve on the sweet valve should only be giving extra assistance when under heavy use of the steering wheel. Jon Quote Link to comment Share on other sites More sharing options...
simonr Posted January 3, 2010 Author Share Posted January 3, 2010 Finally, after a lot of distractions, I got this working today! As mentioned above, I bought a couple of pressure transducers on eBay which were supposed to spit out 0 to 5v at 0 to 100 Bar. Unfortunately, they were broken/Chinese - I guess that's why they were £16 a pair rather than the £110 each RS charge. I looked and looked, but couldn't find anyone making adjustable 100 Bar hydraulic pressure switches - so decided to make some! The design is pretty simple - a 4mm plunger being pushed down by a spring. When the pressure is sufficient, the other end of the plunger pops up and touches the bolt in the top of the plastic bit, closing a circuit and activating the hydraulic valve. Not a very 'Land Rover' ish steering box - but the principle is the same. The switching pressure is adjusted by slackening the lock nut then screwing the plastic bit in and out. I'm still a little amazed that they do not leak, even at 100 Bar. All that is sealing it is a tiny O ring around the piston. What I've found is that id the pressure is set too low, the steering is very jerky (due to the lag in the valve opening and closing). However, as you raise the activation pressure, the system becomes more stable and less noticeable that it's doing anything. Where I've left it set, the ram assist cuts in before any damage is done to the steering box - so it's behaving as a protector, only coming in to play when needed. The result is the steering is normally light and fast, but if it encounters sufficient resistance, the ram assist kicks in. You can feel the force you are putting in at the wheel increases to as plateau (at the point the valve opens) and doesn't increase beyond that. Quote Link to comment Share on other sites More sharing options...
robhybrid Posted January 3, 2010 Share Posted January 3, 2010 hi simonr this looks very interesting. I think again you have as the main inventor in the film robots said "find a need fill a need" Quote Link to comment Share on other sites More sharing options...
forkrentfitter Posted January 3, 2010 Share Posted January 3, 2010 That was really the point. (Well done Steve - have a House Point ) As has been mentioned, there are a lot of cars with electric/hydraulic PAS. The hydraulic pump assemblies seem to contain everything needed - and are pretty light and small. The nice thing is they will operate in addition to your existing steering - so only needs the capacity to cope with the volume of the ram, not the box and ram. I agree that I could put a variable pressure relief if the system I have and it would fix it - but still the flow through the valving in the box is very limited. Will's solution is fine - but still expensive compared to something mostly made of scrap like this! Something else I wondered about was using the torque sensor from an electric PAS system and using that to control the valving on a ram. Trouble was that the output of the torque sensors is difficult to read without a computer - which is when the pressure switch thing occurred to me! Si si,the tarmac rally boys use an electric pump on escorts,they run 15" wheels with 7" slicks,if there is enough power to turn those it will do your job,google a bloke under the name rally extreme in suffolk,he may point you in the right direction. Quote Link to comment Share on other sites More sharing options...
will_warne Posted January 4, 2010 Share Posted January 4, 2010 si,the tarmac rally boys use an electric pump on escorts,they run 15" wheels with 7" slicks,if there is enough power to turn those it will do your job,google a bloke under the name rally extreme in suffolk,he may point you in the right direction. You may be surprised - once you start moving steering lightens up considerably. There are very few pumps available that will give you enough pressure and volume for a really good off road steering system. I'm taking here about tonnes of steering force! There's a reason you need 3/4" rose joints in a high spec hydro assist/full hydro system! Quote Link to comment Share on other sites More sharing options...
simonr Posted January 5, 2010 Author Share Posted January 5, 2010 You may be surprised - once you start moving steering lightens up considerably. There are very few pumps available that will give you enough pressure and volume for a really good off road steering system. I'm taking here about tonnes of steering force! There's a reason you need 3/4" rose joints in a high spec hydro assist/full hydro system! That's where what I've built comes in - it delivers fast, responsive steering when the load is low, but when the force required to move a wheel goes above a preset level, the ram assist kicks in. Although the max rate of steer is reduced - it would be slow to zero without the ram assist! I have a plan to build another one combining all the hydraulics in a single machined part - two pilot cylinders operating a spool valve. Si Quote Link to comment Share on other sites More sharing options...
zim Posted January 5, 2010 Share Posted January 5, 2010 simon - does such a thing as a pilot operated orbital valve exist ? Quote Link to comment Share on other sites More sharing options...
simonr Posted January 5, 2010 Author Share Posted January 5, 2010 Never heard of one - it would be a strange combination anyway. Much easier to make a spool valve. I can only find pilot check valves - essentially a one way valve which will allow flow in both directions when you pressurise the pilot port - a lot like a MOSFET really. Unfortunately, they wouldn't work in this application. This application requires a valve which normally allows free flow between all four ports P, E, A, B. When one pilot port is pressurised, P connects to A and E to B. When the other port is pressurised, P to B and E to A. Si Quote Link to comment Share on other sites More sharing options...
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