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Benifits of a UC front end


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#26 StephenSLR

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Posted 16 March 2006 - 07:37 AM

I believe UC, LH and LX had the same ratio steering racks with the exception of the A9X which had 2 quicker versions available.

I think you are incorrect - from what I have read on this forum previously:

The racks on non-RTS Toranas i.e. LH and some LX's are 18:1 - the no.s on the housing end in 44 or 45.

The RTS racks found on later model LX's and UC's are 20.4:1 - the number on the housing ends in 32.

The A9X has a ratio of 25:1 and the housing number ends in 33.

Chopper - Is the higher the ratio the lighter the steering?

s

#27 Dangerous

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Posted 16 March 2006 - 09:43 AM

Not that you can always trust manuals, but the LH parts manual specifies only one rack for the LH (doesn't mention a ratio), the LX parts manual specifies ratios of 18 and 20.4:1 for all except A9X and 18 and 25:1 for A9X, with separate part numbers for 18 and 25:1 ratios for the A9X, and a Gregory's manual I have for the UC states a ratio of 20.4:1.

Stephen, the higher the ratio, the lighter the steering, but the more turns lock to lock.

#28 Dangerous

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Posted 16 March 2006 - 09:51 AM

-UC lower arm has thicker tie rod stop on front (durability).

I think that the different tie rod stop was to alter the max steering lock before the calipers touched the top wishbones, as the UC used different calipers to the LX.

#29 Toranamat69

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Posted 16 March 2006 - 05:03 PM

Are you serious the A9X's had the 25:1 Ratio optional? That is a 4 x 4 type steering rack ratio :) seems to be going in the wrong direction from the standard ones to me.

#30 Toranamat69

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Posted 16 March 2006 - 07:35 PM

I was a fair way off the mark on my steering rack knowledge :fool:

Seriously though I have never been more glad to be wrong, I was comparing all my calcs of the cortina and WRX rack ratios to what I thought the LX rack was.

Turns out I have an 18:1 ratio Torana one on the test rig.
This means I will have really insanely direct steering with my WRX rack if/when I get my front end sorted out. (should be around 15:1).

Thanks for clearing that up for me.

M@

#31 StephenSLR

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Posted 17 March 2006 - 07:34 AM

the LX parts manual specifies ratios of 18 and 20.4:1 for all except A9X and 18 and 25:1 for A9X, with separate part numbers for 18 and 25:1 ratios for the A9X, and a Gregory's manual I have for the UC states a ratio of 20.4:1.

This sounds right, the LX non-RTS would have had the same ratio/rack as the LH.

The later model LX's phase 1 RTS would have had the 20.4:1

The UC phase 2 RTS also the 20.4:1

#32 Dangerous

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Posted 17 March 2006 - 12:26 PM

Are you serious the A9X's had the 25:1 Ratio optional? That is a 4 x 4 type steering rack ratio :) seems to be going in the wrong direction from the standard ones to me.

Well, 25:1 is listed in the parts manual. Makes for an interesting question though - what did the race cars use? I would have assumed the lower ratio, more direct rack, but maybe someone was thinking along the lines of big wide slicks which would give much heavier but more direct steering, so went for a wide ratio option???

#33 Toranavista

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Posted 07 October 2006 - 06:50 PM

Are you serious the A9X's had the 25:1 Ratio optional?  That is a 4 x 4 type steering rack ratio :)  seems to be going in the wrong direction from the standard ones to me.

Well, 25:1 is listed in the parts manual. Makes for an interesting question though - what did the race cars use? I would have assumed the lower ratio, more direct rack, but maybe someone was thinking along the lines of big wide slicks which would give much heavier but more direct steering, so went for a wide ratio option???

Anyone have the answer?

#34 LX2DR

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Posted 09 October 2006 - 11:07 PM

as the UC used different calipers to the LX.

Must have been a crossover for identical calipers between late LX & UC.

I swapped my 12/77 LX front end for a UC and they had identical PBR calipers.

Made the swap simple, left the calipers on the car, swapped only the front end and bolted everything back on, easy as.

#35 makka

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Posted 10 October 2006 - 12:15 AM

I was a fair way off the mark on my steering rack knowledge :fool:

Seriously though I have never been more glad to be wrong, I was comparing all my calcs of the cortina and WRX rack ratios to what I thought the LX rack was.

Turns out I have an 18:1 ratio Torana one on the test rig.
This means I will have really insanely direct steering with my WRX rack if/when I get my front end sorted out. (should be around 15:1).

Thanks for clearing that up for me.

M@

that could even be too fast! you might need longer steering arms to counter it!

#36 _devilsadvocate_

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Posted 10 October 2006 - 05:56 AM

my 2 cents(a little of topic).........steering in all cars is too slow.
The controls of the modern car are a hangover from the start of last century where the non availability of power assistance required that huge mechanical advantage was required to operate steering, brakes and clutch.
Brakes and clutch with the extra strength of the legs and highly geared down steering so the wheels could be turned with the hands.
The part of the body that takes longest to react, the foot, is still left in charge with the part of motoring which needs the quickest response......braking(with the added complication of having to lift and remove it a considerable distance from the accelerator pedal).........when your hands respond far more quickly.
We are able to ride pushbikes and motorbikes where there is a one/one ratio with the steering.........no one harps on about that being unsafe........or puts some force multiplier reduction gears in there........aeroplane controls too.
Too many collisions happen at low speeds simply because the person at the wheel is unable to turn the turning wheels fast enough to cause the desired correction. The car would become too twitchy at speed if one/one steering is used?..........motorcyles get by..........less assistance could be applied at speed to stop small movements of the wheel sending the car offline.............which is already done to a certain extent in modern cars + the rotational momentum(gyroscopic effect) makes it harder to turn the wheels at speed anyway. Im sure also a fail safe reserve reserviour could also be applied for when engine power is lost........renders most cars unturnable with power steering at present anyway.

Edited by devilsadvocate, 10 October 2006 - 05:58 AM.


#37 _DocDamage_

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Posted 10 October 2006 - 07:25 AM

the rotational momentum(gyroscopic effect) makes it harder to turn the wheels at speed anyway


Its the castor angle that keeps the wheels straight. the gyroscopic effect of the wheels rotating on opposite sides would counter each other

#38 _devilsadvocate_

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Posted 10 October 2006 - 11:09 AM

To ^, large rotational momentum means the wheel wants to keep rotating in the plane it is in and is more resistant to change in direction the faster it is going(I loosely referred to this as the gyroscopic effect as most people have some familarity with how hard it is to change the plane of a spinning wheel or maintain it if held at some distance from its centre ).......or less likely to be bumped of its intended line than if it were moving at slow speed.....whether that bump comes from the road or the person bumping the steering wheel.

#39 _DocDamage_

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Posted 10 October 2006 - 12:54 PM

Gyroscopic effect, if not negligible is inapplicable. Yes is causes resistance to change in direction, and would therefore resist returning to a straight line as much as it resisted turning. Gyroscopic effect is not making your car return it to center at carpark(10-20kph) speed, its castor, the faster you go the more force is applied to this angle making it resist turning and return to center.

#40 _devilsadvocate_

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Posted 10 October 2006 - 01:34 PM

Gyroscopic effect is not making your car return it to center at carpark(10-20kph) speed, its castor, the faster you go the more force is applied to this angle making it resist turning and return to center.

Did I say that it was ^?
.......or not make myself clear in my last post..............yes the castor is very important for making the car track properly.........this doesnt mean that the rotational momentum doesnt play a role in stabilising the direction of each wheel. I think you are referring to the procession effects cancelling when both wheels are forced to turn from their rotating axis?
Anyway, I think we are getting lost here from the point of my post Doc: You obviously have a considerable knowledge and understanding of the mechanics of steering, do you have any comment about having much more direct steering(which I was hoping to stimulate).......given the necessary amount of power assistance........than is presently supplied with cars.

Edited by devilsadvocate, 10 October 2006 - 01:39 PM.


#41 _DocDamage_

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Posted 10 October 2006 - 05:42 PM

I would guess the ratio itself shouldn't make it too touchy at speed because any well aligned car will prefer to run straight. Power steering would make it easy to stuff up and oversteer, but if it was speed sensitive (current technology) that shouldn't be a problem. There's a few at our speedway with quicksteers, some of them are very low ratio (I'll check on the figures), and although we probably don't exceed 80kph on the straight, nobody has a problem with over correction. There could be a host of other issues why they don't do it, I don't know much about hydraulics but I assume higher pressure would be needed and the power required may make it inefficient, better to turn the wheel a few times than have a large pump running at traffic speeds.

#42 Toranamat69

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Posted 10 October 2006 - 05:54 PM

Makka,

If the WRX rack is a go-er and turns out to be too fast/slow at 15:1 (hopefully just right though) then there are WRX, impreza and forester ones with 2 ratios either side of that 15:1 so I hopefully have that under control.

M@

#43 _CHOPPER_

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Posted 10 October 2006 - 06:35 PM

...do you have any comment about having much more direct steering(which I was hoping to stimulate).......given the necessary amount of power assistance........than is presently supplied with cars.

I do. I don't see manufacturers selling new cars with quick racks. The main reason being the car would steer so differently to everything else on the market that new car buyers would take it around the first corner and get into a lot of trouble. As an aftermarket accessory, variable ratio power steering quick racks could have a small market. They are in competition vehicles, but I've heard of very few ( if any ) that are in street registered vehicles.




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