Aloupol
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| posted on 5/1/05 at 12:07 AM |
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Quick rack
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?
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Rob Lane
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| posted on 5/1/05 at 12:25 AM |
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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.
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Rorty
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| posted on 5/1/05 at 01:46 AM |
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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'm unsure why the thread is titled "Quick rack" yet you're talking about 2 or 2.5 turns LTL.
Are you actually after a quick rack or just interested in using an existing power rack?
If you're after a quick rack, there are a few manufacturers who make "quicker" internals which you can fit to your rack housing.
There are also several in-line adaptors that quicken the steering. Some are even adjustable which makes them ideal if you want to drive your car to
the track, quicken the steering while on track and then reset it for the drive home again.
BTW, I agree with Rob Lane, you won't be able to use a power rack in manual mode.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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smart51
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| posted on 5/1/05 at 09:27 AM |
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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.
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Aloupol
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| posted on 5/1/05 at 11:58 AM |
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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]
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britishtrident
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| posted on 5/1/05 at 12:27 PM |
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**** 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]
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HAL9000v2.0
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| posted on 5/1/05 at 12:40 PM |
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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]
You know your making enough power when your clutch operates in binary.
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Aloupol
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| posted on 5/1/05 at 12:42 PM |
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quote:
Originally posted by britishtrident
**** specific MOT failure in the testers manual
OK, it's the answer.
Thy
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Rob Lane
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| posted on 5/1/05 at 12:45 PM |
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So we're agreed then ? Don't use a power steering rack as a manual rack.
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Rorty
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| posted on 5/1/05 at 08:36 PM |
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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.
OK, I'm with you now.
What about using a steering quickener with the manual rack of your choice?
Here's a fixed version:
 
Rescued attachment steering_quickener01.jpg
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Rorty
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| posted on 5/1/05 at 08:37 PM |
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....and here's an adjustable one:
 
Rescued attachment steering_quickener06.jpg
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Aloupol
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| posted on 6/1/05 at 03:49 PM |
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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..
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locoboy
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| posted on 6/1/05 at 03:53 PM |
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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
ATB
Locoboy
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Rorty
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| posted on 6/1/05 at 09:10 PM |
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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
They're usually in the US$125 to US$150 range.
There are a number of "standard" spline counts such as 13/16"-36 (early GM), 9/16"-26 (some earlier Fords), but by far, the
most common and universal is now 3/4"-36 which means it's a 3/4" shaft with a 36 spline count. There's also a smaller
9/16"-36 spline count too and other less common ones like 5/8-36 and 3/4"-30.
The people who sell steering accessories such as these will also be able to sell you the necessary couplings to connect it all together.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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locost_bryan
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| posted on 7/1/05 at 09:24 AM |
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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! 
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chrisf
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| posted on 7/1/05 at 02:03 PM |
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Stolen topic!
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.
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Rorty
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| posted on 7/1/05 at 09:43 PM |
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quote:
Originally posted by chrisf
Rorty:
Do you happen to know the spline count and OD of the Escort MKII steering rack?
I don't I'm afraid. I'm sure someone else who has an Escort rack will come to the rescue. I'm pretty sure it's a small
one, but I don't want to guess and give you the wrong info.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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locost_bryan
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| posted on 12/1/05 at 03:22 AM |
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quote:
Originally posted by chrisf
This is a guy in the US that chopped and converted his power steering rack (MX-5) to
manual
Here is the disassembled rack. Keep an eye out here
for a how-to article - coming soon!
[Edited on 12-1-05 by locost_bryan]
Bryan Miller
Auckland NZ
Bruce McLaren - "Where's my F1 car?"
John Cooper - "In that rack of tubes, son"
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