101 Power Steering

[ejparrott]

Thinking of van PAS boxes makes sense actually, the majority of vans have very short noses and near vertical steering columns compared with all PAS LR's and the vast majority of cars.

If you succeed and pull this off, it would make a very interesting read

[Steveastrouk]

Hi Mike,

Ironically I've just found this post while looking for bits to do another LHD 101 with your PAS conversion. I've still got 62FL19, and I've just put him back on the road after three years off it.

I was looking for guidance on the drop arm you used ?

I'm emigrating to the USA on Saturday, and exporting both my 101s, but the ambi needs the PAS conversion - because she's got no steering box at all. I'm coming back to the UK in a month or so, so I'll finish the work then, but I'm trying frantically to gather the bits so I'm ready when I get here.

Steve

[Roverdrive]

Steve

Just seen your reply.

The drop arm came with the steering box, and is slightly shorter than the 101 equivalent, hence the slightly reduced lock. Could be the LDFdrop arm.

[garrycol]

Garry

This one looks similar??

http://www.ebay.co.uk/itm/LDV-Convoy-400-Power-Steering-Box-Peugeot-Engine-Only-1993-1997-/301097930855?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item461ad5d067

I can't be 100% sure though.

The years indicated would be about right as it was 1999 / 2000 when I did the conversion.

If you still have contacts in the 101 club, try contacting Steve Taylor, as he bought the 101 from me.

Thanks for the information.

I have found a power steering unit that does not change drive through 90 degrees so can be fitted in the steering column. I have seen it in a Volvo 304. The steering column is cut and about 6" taken out and the power unit is inserted - so the original manual steering box is still used - no cutting or fabrication of the chassis but cutting of the steering column.

This is the unit

This is the unit in the volvo with an outer cover welded in. - the pic got turned through 90 degrees - ad the forum will not let me fix it - sorry

[Cheesy]

Isnt that just a straight through servo valve? You would still need a ram somewhere in the system

[garrycol]

I personally do not know - according to the Volvo driver is not required.

[garrycol]

I have asked the Volvo owner to clarify.

[Defender]

I have asked the Volvo owner to clarify.

Did you get any clarification on this? It seems like a good option if no ram is needed.

[greenmeanie]

For what its worth I'd be wary of the column mounted set up mainly because it puts hydraulic lines right next to your legs. When I used to design construction equipment hydraulics for a living that would have been a problem as if a line bursts you spray high pressure hot oil over the driver's legs. He will then no doubt be somewhat distracted from bringing the vehicle to a safe halt. You can get extra sleeves to put over the lines which help but they are really just a band aid.

[Snagger]

The other problem with column mounted assistance (having looked at the Corsa electrical assistance for a 109) is that all that extra torque is applied to the steering boxes and relays, which are are not really up to such forces. I have seen plenty of photos of sheared relays and steering box forks (on the rocker shaft).

[greenmeanie]

In theory there is no more torque applied to the steering components with the power steering mounted as shown. You are overcoming the same set of forces as you have with manual input. It is the input force required from the driver to turn the steering that is reduced. If you are rock crawling etc. you might be tempted to try and turn the wheels in a situation where the steering is more heavily loaded than normal but 101s and rock crawling don't mix for a multitude of other reasons.

[Snagger]

In theory, you're right. In practice, not. The PAS will apply more torque and if the wheels are not spinning, they will not pivot fast enough to avoid stress increase in the steering system. On occasions where there is a lot of steering resistance, like stationary on dry tarmac, it can be impossible to move the wheels with manual steering, but PAS will shift the wheels with relatively little trouble - that is the sort of thing where a column mounted unit will be overstressing the rest of the system.

[greenmeanie]

Ah playing engineer again. Your theory is wrong. The maximum torque applied by the PS will occur when the steering is turned to the stops and the actual value is dictated by the bypass spring and orifice. The only torque factor that is some what time dependent is the rate of body rise due to turning the steering. On a 101 this is not a major factor in the steering loads.

You also have to be careful making comparisons with your Series Rover as it is not apples to apples. The relay shaft at least is considerably larger and it has been to long since I rebuilt one to remember the sector shaft dimensions. Even the steering ratios are different with the series being 15.6-23.8 at full lock while the 101 goes from 23.3 to 25.7 at full lock. The leverage ratios are quite different.

For what its worth the 101 steering is not impossible to move when stationary. It takes approx. 75NM to turn with bar grips, 32PSI on dry concrete. I know. I have one and I have measured. Of course on the original 16" steering wheel that translates into 375N of force. Its not easy, its not fun and it will make a man of you but it is doable. The biggest problem you have is getting enough preload in the steering to overcome the distortion of the big 9.00X16 tyre casing before the wheel will actually turn. In static steering it all feels a bit rubbery and if you let go the steering has quite a lot of kick back. That's indicative of the amount of force required to deform the tyre prior to it actually moving.

Here's a link for electric power steering offered for Land Rover among others showing a max torque of 40NM which can uprate to 70NM. IT is probably a bit anaemic for a 101 on 9.00X16 but when you consider the yield strength of a 19mm steel bar you will see there is a large factor of safety.

There are many reasons beyond simple shear stress that will cause a shaft to fail but brute force from a power steering box is not going to be one of them. There is a lot of typical quality parts from Britpart so we should exclude them. Can you show a sector shaft, column or relay shaft that you can directly attribute the root cause of failure due to power steering?

[Snagger]

You're right about some pattern relays failing under lesser loads, which I why I shelled out the extra for a genuine one years ago. But unless you have fit the relay yourself, how do you know the relay in any second hand vehicle is not pattern? The MoD used Britpart as a supplier for a while, and maybe other pattern part suppliers have been used too.

As for photos of failed units, no I don't have any, because I haven't broken one, but some embers of the forum have.

The PAS unit will apply more torque to the system than a driver will make without straining hard. I don't understand your rebuttal of that - what is the point of PAS if it isn't applying more torque? As you said, turning the steering is very difficult when stationary. The force required to turn them faster is going to be greater, and PAS will do that. The PAS will add to your input, not substitute it like power or hydro-steer, so you won't be able to measure the force on the lower components at the steering wheel. Unless you know the maximum rated forces for each component in the system and can ensure that the steering column PAS unit cannot exceed them, then I think this system is risky. Far safer, I think, to use a conventional PAS unit that applies the output forces directly to the steering rods.

[greenmeanie]

The 101 left service in the early 1990s before Britpart entered the game. The steering equipment is unique to the truck so it is all Genuine parts. There have been some aftermarket parts made for 101s but not steering parts.

Again, have any of these people with broken relay shafts ever managed to have a professional engineer attribute the failure to the force applied by a power steering conversion or even, for that matter brute force applied through manual steering? I'll bet not. There are many potential causes for a shaft to fail in which case it is a rather invalid statement to try and justify a failure due to the force potentially applied by power steering.

I was not denying the fact that PAS will add force to the system. I first pointed out that turning the wheels on dry tarmac is not a measure of the max force it will see.so its a pretty pointless example. The max force occurs when the steering hits the stops and the relief valve opens on a hydraulic system. You seem to think there is a massive increase of the forces in the system with PAS while I point out that while greater they are not drastic i.e they might double. I pointed out that the force added by the PAS is not very significant compared to the yield strength of the components. Even if you take the maximum force I measured (Note you don't normally do this when PAS is helping) add the 70NM of the system linked you still have a safety factor to yield (Note this is deformation and not shear failure) of over 3.0 for the 3/4inch dia column which is the smallest cross section of the system. You are well within the operating range for almost infinite life without deformation. This is normal automotive design safety factors. There is more to it than that but this is enough for a forum.

The strength of the recirculating nut to sector shaft is interesting but the calculations are not too difficult. Bear in mind the entire system was designed before the magic of FEA software.

On a 101 you can't drive the steering linkage directly from a PAS box directly linked to the column due to the forward control layout. On a 101 the fore and aft linkage actually passes the control input aft to the relay. You need to keep the relay in place to put the steering linkage bar in line with the axle. This is not like a series. You could substitute a PS box in place of the burmann nut at the base of the steering column as this is the weakest part of the system. This is what most systems attempt to do but the problem is, as pointed out by the OP, finding a PS box that has the correct input to output conversion and fits to the chassis without serious alteration. It has been done in various ways, usually compromising on one of the stated requirements, but it is not easy or cheap. Adding it into the column just has its own set of compromises.

[moore101]

Malcolm Whitbread used a LHD defender style steering box so the input pointed forwards and then a 90 degree bevel box at bottom of column.

The 101 relay is larger than a series unit so should survive having power steering through it and adds an element of further damping so should help improve steering box life when offroading. Cutting and vee-ing the chassis isn't a terribly messy way of doing it, rebuilding the top of the rail over the v would add strength back in and might make it a tad neater.

[daslandroverman]

A P38 box could be used if you could get a bevel box that rotated the right way, these dont seem as common.

Also worth remembering that the 101 drop arm faces backwards, and that turning it 180 degrees (as is needed with the Jeep boxes) will mean the steering linkages start moving in ways they werent designed.

I recall someone did it with the Jeep box in the above fashion and found that on full left lock the drop arm and drag link would move far enough as it couldnt be pulled back into line without assistence.

There are some Nissan boxes been made to work out in Australia, but I'm not sure on types or models.

[Snagger]

Without having a 101 to study, it's just a guess, but could you mount a P38 box (stronger than the Adwest types and more reliable) so that the input is vertical and the output shaft pointing aft? You'd have to mount it further outboard on a short outrigger so that the drop arm could move to the left, but as they're offset to the right for the drive-straight position, the length of the outrigger may be small enough that the input shaft aligns with the steering column easily. I think the swivel end TRE of the drag link will cope with the vertical pivot of the link as the drop arm moves through its range. The biggest issue would be bleeding the system with that orientation, but it may be possible to get good results with a vacuum bleeder or by bleeding the box before fixing to the chassis, drag link and column.

[greenmeanie]

Regardless of the geometry of the steering bars and the bump steer potential you have outriggers in the way which would require significant butchery. If you accept the fabrication aspect it can be done without making the other compromises inherent in your idea.

[Snagger]

I can't see why bump steer would be increased. The only issue with having the drop arm rotate on a vertical plane rather than horizontal is making sure it and the drag link don't foul anything.

[greenmeanie]

_{Again this is not as easy as a series PS conversion. Given that the steering column angle is fixed that dictates the angle of the steering box and the chassis rail position to weld a mount dictates the vertical position of the box. Your first problem will be making sure the pitman arm isn't blocked by the chassis rail as it heads towards full lock.}

_{You could play with the steering box angle by adding a UJ at the column to steering box joint but then you have to factor in how you support the steering column. You have no footwell to bolt to as in a series PS conversion so now you have to fabricate column mounting brackets which makes the job more complex again. You can't play much with column angle as the clearance between the steering wheel and you knees and stomach even with the smaller 101 wheel so you steering box location for your design is pretty heavily constrained. You will still be limited on the steering box angle to clear the bottom of the chassis rail with the pitman arm.}

_{From this you are driven to a fairly specific location for the pitman arm end of the box. After that you will find yourself very lucky indeed if your steering linkage arm is parallel with the pivot of the front axle. Do you expect to change the pivot motion and steering linkage angles without affecting bump steer?}

[Ferret65]

Did you manage to sort your power steering out .I put a post on the 101 club site using a jeep unit and I 'got rinsed .I have done over 10k miles as I use it most days as a work vehicle and it works great if you want more info Let me know

[garrycol]

I certainly have not done any more but have decided to use the modification that uses a Nissan Patrol steering box up on the front cross member and the relay is no longer needed. Where a disco steering column comes through the floor it goes into a 90 degree gearbox out of a Isuzu Rodeo that takes a steering shaft back to the Nissan box.

I would be interested in any pics on what you have - is your 101 RHD or LHD and what Jeep box did you use. I have a RHD Cherokee TJ box that would fit in where the standard 101 box goes but it turns the wrong way - a LHD Jeep box might work but I do not have access to one to check.

I find many people on the 101 forum not as helpful as they could be and as a result I am no longer a member.

Garry

[Ferret65]

I am trying to put together a few pictures together of what was done on my GS for the steering .Inthe meantime Google jeep Cherokee xj power steering box. It's a compact unit not dissimilar to the original Burman box the chassis needs no cutting as the box fits perfectly through the existing hole in the chasis. It can be rotated backwards to accommodate the steep angle of the steering column. The box itself is left hand drive and my Gs is right hand drive

[garrycol]

The box itself is left hand drive and my Gs is right hand drive

Thats what I figured - the Jeep box I have is from a RHD vehicle and does not work - I would have to buy a LHD box sight unseen from the US - shipping would also make the price pretty prohibative.