Stag Power Steering

[chamchella]

Hi,
I am looking at how I can induce a little more feel at driving speeds into the stag steering and see that the control valve is operated by a torque bar down the centre of the valve assembly.
My thoughts are to reduce the diameter of this torque bar to increase the amount of movement required before power is applied.

Does anyone have any experience or comment on this subject?
Cheers

[mikeyb]

I'll be watching this thread with interest!  I too am looking to reduce the assistance on my Stag.  Have heard talk of faulty one way valves etc being the cause but every power assisted Stag/Big saloon I have ever driven have felt over assisted to me!

[shenderson]

As I understand it, the torsion bar allows a slight misalignment between the input shaft (steering column) and the pinion to develop when steering is applied.  This allows pressurised fluid to flow through the valve and enter one or other side of the rack to assist steering effort.  Reducing the diameter of the torsion bar will reduce its 'springiness', which will allow fluid pressure into the rack earlier when steering is applied.  This in turn will make the steering feel lighter, opposite to the desired effect.

Hope this helps.

Steve H

[chamchella]

Thanks Steve,
I had thought that the torque bar drove the valve, however if the valve lags behind, it is the opposite to what I thought and lines up with another comment that replacing the drive pins made a difference in one case I read about.

I am making up a jig to determine the deflection of the torque bar and was going to make up new bars rather than alter the original.

It might be fiddly but it seems everyone agrees that stags did not have enough feel in the steering at road speeds.
Rob

[andy thompson]

I have found late 2500S PAS racks to be nice and heavy ... my dads 1976 2500S had such heavy PAS compared to a 1973 2000 that he thought it was not working correctly. I clearly remember when he part/exchanged the 2000 (original/unmodified) for the 2500S (also original and unmodified) he said the steering felt COMPLETELY different

Early PAS systems on Triumph (pre 1975/76?) seem to behave like the early XJ6's and XJ12 - very american - finger light and no feel.

I have PAS on my 2100 EFI and obviously my Stag - they have good weight and feel although the original rack on the Stag was awful .. luckily plenty of S/H 2500S rack here.

[chamchella]

Interesting Andy
I might have a look around for one. I am in Tweed NSW.

[RoddersStag1977]

lagerzok wrote:

I have found late 2500S PAS racks to be nice and heavy ... my dads 1976 2500S had such heavy PAS compared to a 1973 2000 .

I have read on the TSOA website that the steering ratios of the earlier Triumphs was substantially higher, meaning more turns of the steering wheel from lock to lock. perhaps the 'feel' in your dad's S is due to the tighter ratio in this later model.

I'm interested in this thread because I'd like to know if the stag power steering rack is the same as the spare 2500s rack that I have. I suspect so, but can't seem to get it confirmed online.  ::)

[RoddersStag1977]

lagerzok wrote:

I have found late 2500S PAS racks to be nice and heavy ... my dads 1976 2500S had such heavy PAS compared to a 1973 2000 .

I have read on the TSOA website that the steering ratios of the earlier Triumphs was substantially higher, meaning more turns of the steering wheel from lock to lock. perhaps the 'feel' in your dad's S is due to the tighter ratio in this later model.

I'm interested in this thread because I'd like to know if the stag power steering rack is the same as the spare 2500s rack that I have. I suspect so, but can't seem to get it confirmed online.  ::)

[andy thompson]

I am virtually sure it is related to the control valving (torsion bars?) in the rack itself - where the hoses bolt in. The ratios are the same although dependant on where the rack stops are set gives a slightly different "book ratio" between 2500 and Stag.

[CRAJ]

On our estate I have what was said to be a Stag rack (recon), it is much heavier than the original S rack was (strangely), but I have also lost a little lock each side which means a bigger turning circle than before. This is caused by slightly thicker nylon end stops on the rack in a Stag rack in comparison to those on a big saloon one. A between the cones type of driving test at last year's Register National highlighted this and was verified by Charles Harrison when we swapped cars for a second go , 'turn you bas@*£d' was I believe what Charles was shouting at the estate.

I drove a friend's Stag the other night and would agree that the steering was way too light and certainly much lighter than the PAS on our estate or our pi saloon and that was with a 13" motalita wheel fitted!

Colin.

[chamchella]

You are right about the rack ratios,
Pre 1972 Stags had 4 turns lock to lock; 72 and 73 has 3 turns and 1974 onwards has 2 1/2 turns. the later Stags, 73 onwards had a smaller steering wheel as well; 141/2" against the 16" on earlier cars. This probably accounts for the heavier feel in the later Triumphs.

I still think like most people that my 1975 steering is lighter than optimum and can be difficult to keep on line in corners.

Perhaps the only way to find out is to make up a jig to measure the torque required for a specific torsional rotation and then experiment by making up a couple of new shafts with say a 10% and 15% increase in torque required to make the same rotation.

Some would say that is a waste of time but then why else would we own a Stag?

[StagNL]

Interesting info you post there cham.  Do you (or anyone else for that matter) have any info as to how one can see the difference (markings?) with the rack off the car?

See, I have two steering racks..... one off a 72-73 car, the other off a 75.  

Julian

[chamchella]

I will have a look but I think the quickest way would be to see how many turns from lock to lock.

[chamchella]

I now have a better appreciation of what is going on. The test rig worked a treat.

I transpires that the inner spool only has to move 2.5  degrees (0.0195") before the power assist ports begin to be exposed. This requires 2.6 foot pounds of Torque at the shaft, which is next to nothing at the steering wheel and clearly relates to the light steering.

The next step is to make up a couple of new torque shafts with say 15 and 20% more meat in them and see what happens.

[mikeyb]

Fantastic, great to see some proper engineering being explored!

[chamchella]

Well we now have a new control shaft which has a 25% increase in torque required to move through 5Deg and then we find that the original shaft and spool was drilled 5deg off Centre at the input end??? This means that it would not be possible to fit new components to these power steering spools as each one may be different.

If a new input shaft does fix the steering feel then each one would need to have the unit partly assembled and the input drilled in situ?

It makes one wonder how many other components on the Stag suffered such ignominy.