Jump to content


HX stubs or not?


  • Please log in to reply
65 replies to this topic

#26 _XY driver_

_XY driver_
  • Guests

Posted 03 December 2016 - 01:15 AM

There's some voodoo going on here with the bumpsteer... using the Torana stub axle... if we can get a figure like that when it's done then I reckon everything will be pretty flash.



#27 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 7,140 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 03 December 2016 - 04:45 AM

Not trying to rain on your parade but the bump steer could change significantly if you still don't have shims set to the desired static alignment, you really need to do that first. Because it moves the upper arm (and indirectly the steering arm) around it changes the position/arc of the wheel (which the tie rod needs to match for minimal bump steer).

Its an extreme example but I did some measurements comparing maximum positive caster settings to maximum negative caster settings and found up to 20mm difference in bump steer, in excess of 3mm immediately off ride height.

#28 _XY driver_

_XY driver_
  • Guests

Posted 04 December 2016 - 11:55 AM

Absolutely no offence taken, I have done a little of this before with an off-road racer. Placement of the steering rack on that car was a real eye opener, with minor changes making major problems. What I'm trying to get my head around is how much camber change is desirable or useful. I can easily imagine that throwing this thing into a corner could produce 5 degrees of body roll, so a similar amount of camber would help keep the tyre square to the road. However the car might be badly served by excessive camber under brakes. I think I'm happy with the cant on the top arms, next step might be to drill the crossmember and set up with some washers for a proper alignment. Before that I think the most urgent matter is some 12(?) degree wedges to make sure the extended top ball joints don't bind at full bump. Not sure how I'm going to do them yet.

Attached Files



#29 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 7,140 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 05 December 2016 - 06:06 AM

In that case it sounds like you also want to determine (roughly) what the actual ride height will be so you can figure out the total travel - could be as little as 40mm in compression which would affect the camber gain options.

Didn't realise that the extended ball joint would bind to the point of not even reaching the bump stops. Very interested to see how it all comes out especially with the upper arm canted for anti-dive.

#30 _XY driver_

_XY driver_
  • Guests

Posted 05 December 2016 - 09:46 AM

I'm still working at it.

 

With the crossmember bolted to a pallet I can get the thing level from side to side, easy. What's the general consensus about fore/aft angle of the crossmember... I have compared the sills to the engine bay chassis rails and it seems the latter are pitched up about 2.5degrees? However that might be an inconsistent figure, the engine bay rails have been damaged a bit so it's hard to get a straight piece to measure from, and the turned down lip at the top of the engine bay rail isn't necessarily parallel to the bottom, nor are the bottom face of the sills to the very bottom edge. These are mass produced cars of course.

 

 

 

Caster measurements without a gauge are a pain in the arse but I've read up enough to quietly ignore the highly complex maths that talk about thrust line and tangental error. The simple approach is to gauge 20 degrees of steering lock each way, measure camber at each end, take one from the other and multiply by 1.47.

I can't believe there isn't an android app to make your phone into a caster gauge...

 

Ball joint bind has thus far been fixed by a piece of 2" exhaust tube cut at 20degrees. This sleeve probably needs to be 15 or 18 degrees, or the arm clearanced slightly to allow the joint to sit at 20 degrees. At the moment the hole in the arm isn't big enough.

 

 

Must carry on, work is calling



#31 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 7,140 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 06 December 2016 - 05:42 AM

That's the basic version of the caster calculation, which is probably near enough. If you're interested here is an example of the wheel alignment sheet I use with a slightly more accurate calculation:

Toranaalignment2Sep2014.jpg

You can usually work on the chassis rails and cross member being level, all depends on how you set the car up with springs of course. As long as the caster is even side to side you probably just want to get the maximum you can since its unlikely to be excessive (note GMH max shim stack 0.5" if legality is a concern), with static camber in the ball park at ride height.

I have wondered about the app thing but came to the conclusion that a phone probably isn't particularly accurate with its angle measurements especially since many don't have properly flat edges.

#32 _XY driver_

_XY driver_
  • Guests

Posted 08 December 2016 - 07:55 PM

Just call me the suspension whisperer... O.o

 

I'm wondering what I did wrong but I've measured it three times, even braced up the pallet/workbench to make sure the shift in suspension wasn't flexing things... but I just can't get this thing to bump steer. It's quite disturbing because I just want to weld the thing in place and say "my work here is DONE" Surely it won't be this nice when it's back in the car?

 

So the setup is like this. The crossmember is laid back 2.5 degrees to the rear. (I can make sure this is preserved in the car by making offset outrigger bushes?) Top arm canted 16/32mm lower art the rear. Standard UC spindle and arm. +900" top ball joint mounted in a 20degree wedge. Finally a 9.6mm spacer behind the rear of the top arm...

 

Mid suspension travel basically has the rack end level. At that point the static alignment is .96deg neg camber & 6.67deg pos caster

 

What's figjaming me is the bump steer or complete lack of it. .07deg toe in at full droop... .04 toe in again at full bump. It's embarrassing.

 

Think I need to go and do something to bugger it up...

 

 

 



#33 _XY driver_

_XY driver_
  • Guests

Posted 08 December 2016 - 08:13 PM

So here's the picture

Attached Files



#34 Bigfella237

Bigfella237

    Socially Distant

  • Members
  • PipPipPipPipPipPipPip
  • 4,359 posts
  • Name:Andrew
  • Location:Far South Coast of NSW
  • Car:(s) not as many as I'd like but more than I've got space for!
  • Joined: 31-October 14

Posted 08 December 2016 - 08:59 PM

Love yer work Tony! Just to clarify your UCA mounting position, I assume your holes are 16mm & 32mm lower than the standard UC mounting holes, but are all UC mounting holes in the same place?

 

And say somebody has an LH k-member, is there some other common point from which you could measure that will be the same on any Torana? Or would they have to set everything up as you have and take their own measurements?

 

One last thing, I note you have Nolathane bushes in the steering rack mounts, if someone were planning on replacing these with solid alloy bushes, would offsetting the rack up or down slightly help with tuning the bump steer (not that you need to)?



#35 _XY driver_

_XY driver_
  • Guests

Posted 09 December 2016 - 12:47 AM

I can't tell you if LH or LX are the same, there were changes made when they went to RTS suspension, however I believe the UC rack is a bit longer/rack ends shorter, the UC upper arm mounts are higher, and the UC top arms have an offset ball joint for more caster.

 

A9X and XU1 Toranas both had the upper arm mountings moved down about 25mm from their existing holes as far as I know.

 

Moving the rack could be frought with danger, though I'm sure the other knowledgeable blokes on this thread have done it when they've been doing power steer conversions. It's bloody hard to predict what any of these changes do and I'm often surprised at how much things move with what seems like a slight adjustment.

 

From what I can tell, the best approach is to work out a basic alignment on your car, the static settings at the ride height you want, then with a few tricks you can adjust the height of the outer tie rod ends to minimise bump steer. I'll try to find a picture of an adjustable setup, not that it's the final word, but it'll give you an idea.

 

Cheers



#36 _XY driver_

_XY driver_
  • Guests

Posted 09 December 2016 - 12:54 AM

This is a 5/8 rose joint I think, on a modified UC front end. Uses a 5/8" bolt through the arm, taper is drilled out and height is adjusted with washers. I think there is a threaded sleeve to adapt the rose joint to the rack.

Attached Files



#37 axistr

axistr

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 1,163 posts
  • Location:North west sydney
  • Joined: 19-November 05
Garage View Garage

Posted 09 December 2016 - 07:27 AM

The only way you can get zero toe movement through out the suspension travel is to have the inner steering rack ball socket centre at exactly the same height and centreline as the lower inner control arm mount pivot bolts, and the outer tie rod end ball centre must be inline and same height as the lower control arm ball joint centre. You can also have these rack ball joint centres above the lower control arm mount pivot and lower ball joint but must be at the same centreline heights.(ie standard holden design) The problem with the raised heights is you must have even length top and bottom control arms to achieve zero toe bump steer and that isn't going to happen with the torana setup.

 

The stub axle close to inline height with the lower ball joint is also desirable to keep things better inline. As previously mentioned  bump steer or the movement in an unwanted direction is just as common from excessive movement in camber and or caster.   



#38 76lxhatch

76lxhatch

    That was easy!

  • Members
  • PipPipPipPipPipPipPip
  • 7,140 posts
  • Location:Unzud
  • Car:SS
  • Joined: 04-August 08
Garage View Garage

Posted 09 December 2016 - 09:57 AM

By my calculation 0.07 degrees over a 600mm diameter wheel/tyre is ~1.5mm (got to account for both sides) change in toe, which is very good. I only got mine down to about 2.5mm.

Yes moving the rack does help with bump steer (and is one of the main reasons you would move it). If that and the Ackermann geometry comes out correct (as well as ensuring its on centre) you can generally be assured it will be fine. If you are moving outer ends by much you will usually find you need to move the inner ends to match.

#39 _XY driver_

_XY driver_
  • Guests

Posted 10 December 2016 - 01:15 AM

So I've got the brakes now, Seems UPC aren't too bad though I've not found any hubcaps in the box full of bl##dy foam packing peanuts. Most pleasingly the Convo Pros fit, except I've got to turn nearly 1mm off the hub diameter to allow the center cap to fit. Extended top ball joints offer lots of room for the caliper so I reckon they're worth the price of admission. Had to grind a little out of the corner of the spindle to fit the UPC caliper bracket but that's neither here nor there really. The caliper is very close to the tie rod end, so I'm tempted to swap the spindles & try the caliper on the back, perhaps just so it's not as busy when we fit a front mount sway bar. Have to get the PC fired up and get the next graph uploaded, but pictures will have to suffice for now.

Attached Files



#40 Rockoz

Rockoz

    Lotsa Posts!

  • Members
  • PipPipPipPipPipPip
  • 3,945 posts
  • Name:Rob
  • Location:Cowra NSW
  • Joined: 21-September 08

Posted 10 December 2016 - 09:26 AM

Just wondering if the picture that is on here with the chassis measurements will help you determine the angle of the crossmember.

Someone will know where to find it for you.



#41 _XY driver_

_XY driver_
  • Guests

Posted 10 December 2016 - 10:19 AM

You'll like this one more Axis... just out of interest I put it back to standard with the exception of the extended ball joint and a 9.6mm shim behind the rear of the top arm mount.

Attached Files



#42 _XY driver_

_XY driver_
  • Guests

Posted 10 December 2016 - 10:23 AM

However when we go back to a lower/canted top arm and a 12.5mm shim the bump steer straightens up again!

 

I might have a better solution for the top ball joint shortly... better get on with it;)

Attached Files



#43 axistr

axistr

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 1,163 posts
  • Location:North west sydney
  • Joined: 19-November 05
Garage View Garage

Posted 10 December 2016 - 10:57 AM

Tony I reckon your better off with the least amount of caster change throughout the suspension travel as possible, hitting a decent bump at speed and finding out you have just added two degrees more caster on one side will very quickly steer you in an unwanted direction. Going on some of the graphs you have posted the car could move across the road substantially before you could properly correct it.  I would prefer a small amount of toe change over any caster variation between sides.

 

I also found an old picture I took of a Torana on my alignment machine some time ago, This thing was a real mess when it turned up and I had to change steering arms and correct bent parts and start from scratch. It had major bump steer problems which we had to iron out.  I scribbled on the photo which helps explain the importance of even rack tie rod bar to cross member and lower ball joint heights. And the importance of having level tie rod bars at ride height. 

 

 

   

Attached Files



#44 Bart

Bart

    Shit a brick

  • Members
  • PipPipPipPipPipPip
  • 2,559 posts
  • Location:Sydney
  • Car:LJ Torana
  • Joined: 20-November 05

Posted 11 December 2016 - 03:32 PM

I like those top ball joints. I have similar in my LJ where tapered pin can be removed and swapped for a longer or shorter pin.
My top ball joints are also Chrysler screw in ball joints.

Edited by Bart, 11 December 2016 - 03:34 PM.


#45 _XY driver_

_XY driver_
  • Guests

Posted 14 December 2016 - 12:41 PM

Joints to be fitted today... have to find myself a suitable holesaw I think. I'm surprised there's so little depth in the thread that engages these joints in the sleeve.

Attached Files



#46 mattie304

mattie304

    Forum Participant

  • Members
  • PipPip
  • 27 posts
  • Name:Matt
  • Location:Newcastle
  • Car:LX 4 door
  • Joined: 22-December 15

Posted 08 January 2017 - 11:23 AM

What stubs and steering arms are you running ?



#47 71XY

71XY

    Forum Participant

  • Members
  • PipPip
  • 9 posts
  • Name:Anthony
  • Location:Gawler
  • Car:LX
  • Joined: 26-January 21

Posted 22 October 2023 - 12:10 PM

Right so he made it to Summernats after a couple of all nighters getting the front end back together... https://m.facebook.c...801630306777740 And despite limited miles he told me is was pretty good to steer so that was a win. Sadly it managed to have an engine bay fire fuelled by trans fluid a couple I've outings later and has been off the road since. While the blower out the bonnet was always a cool look, it had that wow factor which really attracts police attention and a defect to go with it. So now they're trying to fit a late model factory supercharged Corvette engine... and it's just too big to fit under the bonnet. The *GENIUS* solution was to section the middle out of the crossmember and lower it about 100mm(?) and take the steering rack with it. They know not what they've done.

Attached Files



#48 71XY

71XY

    Forum Participant

  • Members
  • PipPip
  • 9 posts
  • Name:Anthony
  • Location:Gawler
  • Car:LX
  • Joined: 26-January 21

Posted 22 October 2023 - 12:14 PM

I can't unsee it...

Attached Files



#49 71XY

71XY

    Forum Participant

  • Members
  • PipPip
  • 9 posts
  • Name:Anthony
  • Location:Gawler
  • Car:LX
  • Joined: 26-January 21

Posted 22 October 2023 - 12:16 PM

I haven't looked to see how they gor a steering shaft to it; through the crossmember.

Attached Files



#50 71XY

71XY

    Forum Participant

  • Members
  • PipPip
  • 9 posts
  • Name:Anthony
  • Location:Gawler
  • Car:LX
  • Joined: 26-January 21

Posted 22 October 2023 - 12:28 PM

I guess my only question is what can they do with it? I'm probably not going to be into it this time. I was heavily invested in the last attempt and not really consulted on what's happened since. Same token I don't want to see him in an undriveable hunk of shit. I heard they were struggling to fit the new donk & was initially pleased they didn't just bin the front end and put a tube steel one in... but in retrospect this is worse for all concerned. Can it be saved with some unconventional steering arms (orange) and a bump steer kit like they make for a Mustang (blue) with rose joints (yellow) Or do we make it much easier (or actually possible) to install an exhaust by resorting to an aftermarket front end like MacDonald Bros? Do those things even steer or are they just for drag racers? ¯\_(ツ)_/¯

Attached Files






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users