Powered steering street cars have something like 2 or 2.5 wheel turns from full left to full right.
Is it a good option to use a street car's powered rack as a non powered quick rack after removal of all the hydraulic bits?

I seem to remember that power steering racks have built in centre play to allow for 'hysteresis'. i.e. in centre it prevents the hunting of the pump backwards and forwards for small inputs.
This makes them unsuitable for manual use.

quote:

---

Originally posted by Aloupol
Powered steering street cars have something like 2 or 2.5 wheel turns from full left to full right.
Is it a good option to use a street car's powered rack as a non powered quick rack after removal of all the hydraulic bits?

---

I don't know if a power assisted RACK has play in it or just the hydraulic controls. You will need to connect the two steering fluid pipes together on the rack because of the oil shift between the two "pistons". All that oil flow - it might make the rack seem over damped.

A hydraulic rack has a seal in the middle of it creating two chambers inside the rack housing. pump oil into one and the rack moves with the pressure. pump oil into the other side and the rack moves the other way. seal the pipes and you will create pressure in the "pistons" causing the steering to wight up heavily.

Ratio: the last car without servo steer I had was a 205 Rallye, the wheel had 4 turns from stop to stop. So a standard servo steer with 2.5 turns used in manual and with a 300 mm wheel would look to me as "quick rack". A real quick rack (what I call "too quick rack") is probably more direct but I don't consider it, I won't be able to keep the car.
The problem is, I think, not the gap which is likely the same in manual and servo racks, but the flexible part used to allow the servo system to sense the torque. I don't know if that bit is in the rack or in the column, neighter if it's replacable by a rigid part. I will check in some shop manuals.
My daily car recently had a servo steer problem, it was deadly heavy (due to the front end geometry I think, designed for servo) but there was no play and no flex at all. I think modern cars don't have a flexible unit, the torque sensor remains rigid in our effort range.

[Edited on 5/1/05 by Aloupol]

**** specific MOT failure in the testers manual **** --- if you have a power steering rack you can't just remove the pipes and pump and call it a manual system note the same situation applies to brake servos -- if fitted it is testable must work as intended.

Early power racks fitted to BL cars used side to side play in the pinnion to operate an external spool valve which sat piggy back on the rack.
In later hydraulic power racks everything is internal to the rack, the steering wheel connects to a rotor valve valve the shaft of which connects then to the actual rack via a lost motion coupling. When the internal coupling wears the steering becomes fully powered with no feed back this is a common fault on Rover 800s are very high mileages quite frightening to drive !

Power racks are not designed to take the high pinnion loads found in a manual rack and won't stand up to it for long.

.


[Edited on 5/1/05 by britishtrident]

I'am using Peugeot 309 power steering rack without valves and seals except end one. It have normaly 3,75 turns. On front uprights (Toyota corola RWD) I have cuted "arms" for steering rack and weld it back lower and closer. With that I have 1,82 turns and bump steer less then 0,003°/cm (0,00762°/" )

[Edited on 5-1-2005 by HAL9000v2.0]

quote:

---

Originally posted by britishtrident
**** specific MOT failure in the testers manual

---

So we're agreed then ? Don't use a power steering rack as a manual rack.

quote:

---

Originally posted by Aloupol
Ratio: the last car without servo steer I had was a 205 Rallye, the wheel had 4 turns from stop to stop. So a standard servo steer with 2.5 turns used in manual and with a 300 mm wheel would look to me as "quick rack". A real quick rack (what I call "too quick rack") is probably more direct but I don't consider it, I won't be able to keep the car.

---

Rescued attachment steering_quickener01.jpg

....and here's an adjustable one:
Rescued attachment steering_quickener06.jpg

Looks nice enough...
Maybe even too, I guess it will be slightly uneasy to find here in BCB-Land (AKA Belgium) at affoardable cost...
I will go the manual rack way, and try to manage something by myself if the ratio is too high.
Thanks..

Rorty,

What sort of price are those things? and do steeting racks have a 'standard' spline pattern? ie will that device be specific to the rack or is it a one size fits all set up?

Cheers

quote:

---

Originally posted by colmaccoll
Rorty,

What sort of price are those things? and do steeting racks have a 'standard' spline pattern? ie will that device be specific to the rack or is it a one size fits all set up?

Cheers

---

If I understand power steer racks correctly, the input shaft is connected to the pinion via a toque-sensing unit (a torsion bar or some such), and this is used to sense the amount of assistance required and controls the flow from the pump to the piston. Engine or road speed sensitive systems meter the pump pressure to reduce assistance on the move.

My potential single-source donor has no manual rack option. In NZ we don't have SVA, but we have a certification process that requires approval by a certifying engineer.

Would it be technically feasible to rigidly connect the input shaft and pinion, connect the two hydraulic sides together with a pipe for 0 pressure (I understand the rack requires the hydraulic fluid for lubrication), to make a manual rack?

I've experienced a loss of power steering after an engine failure, and it scared the hell out of me when I had to struggle to get round a tight bend!

Rorty:

Do you happen to know the spline count and OD of the Escort MKII steering rack?

As for the powersteeing to manual conversion...I'm not sure I understand what the problem is. This is a guy in the US that chopped and converted his power steering rack (MX-5) to manual. He reports no issues.

quote:

---

Originally posted by chrisf
Rorty:

Do you happen to know the spline count and OD of the Escort MKII steering rack?

---

quote:

---

Originally posted by chrisf
This is a guy in the US that chopped and converted his power steering rack (MX-5) to manual

---