8smokingbarrels
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| posted on 2/7/03 at 09:56 PM |
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Strut your stuff
Ive been looking closely at the Audi struts I got and seem to have hit a snag. Basically the steering knuckle (more like a bracket really) is up very
high (just below the spring) and will have to be relocated.
I was keen to use the bottom part of the strut because driveshafts and lower balljoints naturally fit straight in. But Im sure an SVA inspector isnt
going to be particularly pleased by welded steering knuckles.
Just wondering if I should look for something with a knuckle lower down (like Alan's MR2 strut). Thoughts anyone?
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kb58
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| posted on 3/7/03 at 03:00 AM |
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What's wrong with welding one on, assuming reasonable thickness material is used?
Why not ask the SVA people now?
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Alan B
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| posted on 3/7/03 at 12:27 PM |
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I was going to answer this by saying I'd seen a welded on steering arm which looked good.......but I couldn't recall where.....now you
reminded me...it was you KB...
If are going to trust your life on a home welded chassis with home welded suspension then this is no different IMO.
Good welding, and plenty of run length by design, you should be OK....
But, as KB says, the SVA guys should be able to clarify.
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kb58
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| posted on 4/7/03 at 12:52 AM |
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I hope you're not referring to the picture showing the steering arm tacked on by a couple tiny welds... It's that way because I'm
going to double-check bump steer before final welding. It's good for another reason, that I recently changed my mind on how much Ackerman to
use.
How much are you using?
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Alan B
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| posted on 4/7/03 at 01:08 AM |
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Don't worry I could see it was just tacked......I meant the idea of the square tube arm looked good......plenty of weld length
available....
Ackerman?...I guess it will be the same as per the standard MR2....there isn't really anything I've changed except perhaps the fore and
aft position of the rack (slightly)...
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ProjectLMP
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| posted on 4/7/03 at 03:10 PM |
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KB how much ackerman are you planning on using? Allan Staniforth was very insistant that I use full ackerman on my car. My uprights allow me to bolt
on different steering arms so it will be easy to experiment.
Home of the Astronomicalcost Mid engined LMP project
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8smokingbarrels
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| posted on 4/7/03 at 09:26 PM |
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Usual thx to you all for replying. I will toodle off and get the SVA regs ASAP.
Ill definitely go with cut down Struts on the back with relocated knuckles for the non-steer arms.
At the front I was tempted to use another pair of cut-down Audi struts but not sure if i can. The problem is that the strut will no longer be
attached to a driveshaft - leaving a rather large hole in it!
Obviously the strut couldnt come off as it would be attached to the wishbones but I guess it would still need some sort of 'stub axle'
running thru it for the disc to spin on.
Any thoughts on this or should I simply use something like Sierra uprights- which might be a lot less hassle!
chris
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ProjectLMP
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| posted on 4/7/03 at 10:15 PM |
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I use the same wheel bearings and drive flanges all the way around (of a Mitsubishi EVO 4 wheel drive car). On the front I have two machined stub
axles in place of the drive shafts. In my case I have to run then as they help keep the bearings in place.
Home of the Astronomicalcost Mid engined LMP project
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kb58
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| posted on 5/7/03 at 01:07 AM |
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quote:
Originally posted by ProjectLMP
KB how much ackerman are you planning on using? Allan Staniforth was very insistant that I use full ackerman on my car. My uprights allow me to bolt
on different steering arms so it will be easy to experiment.
I was going to use zero, based on the Milliken design book. Then I reread Smith's "Engineer to Win", where he actually went out and
played around with different settings on a real race car, asking the driver how it felt everytime he changed something. The results were contrary to
what Smith expected (and voiced as opinion earlier.) His latest conclusion is that more is better.
So I'm going to put in as much as possible. It takes care of several items. One, my steering arm will miss the lower a-arm if I move it
outboard. Two, the car can easily be pushed around (with no Ackerman this can be very hard,) and Three, Smith is the only engineer I know who
actually tried different settings and found what worked.
Of course this was a *real* race car on slicks... which isn't what I'm building, but as the saying goes, "At some point you have to
stop dicking with stuff and just build the damn thing."
[Edited on 5/7/03 by kb58]
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Alan B
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| posted on 5/7/03 at 11:49 AM |
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quote:
Originally posted by kb58
..........."At some point you have to stop dicking with stuff and just build the damn thing."...........
That should be engraved in granite somewhere...it is soooooooo true..
I think someone also said something like..."a good plan executed, is better than a perfect plan that isn't"....means the same I
guess....
When a hour's worth of planning and calculating saves you a week's worth of post build changes...then that is worth doing, and you will do
this early on in the design phase.....
However, when a week's worth of extra design/calcs saves you an hour's worth of post build changes, then things change, and you are into
the "build the damn thing" phase...
That's my theory anyway (and KB's I suspect).....
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giel
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| posted on 2/8/03 at 10:19 AM |
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quote:
Originally posted by 8smokingbarrels
Ive been looking closely at the Audi struts I got and seem to have hit a snag. Basically the steering knuckle (more like a bracket really) is up very
high (just below the spring) and will have to be relocated.
I wonder why the high position is a problem for you, are you not going to convert it to double wishbone?
I am using the audi struts too, but haven't seen the problem yet. I'm going to use the rear spring-damper units on the struts, on front-
and rear axles. So I need two donors for the suspension.
Giel
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8smokingbarrels
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| posted on 8/8/03 at 10:34 PM |
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Yes indeed, Im going for double WB.
I have since moved the steering arm down without too much fuss although positioning horizontally in both planes was tedious.
The main problem Im having at the moment is the large KPI angle which is going to make the upper wishbone very short.
This could be resolved by reducing the angle to the vertical of the upper wishbone brackets (i.e. placing them more or less directly above the lower
brackets).
The locost has its upper brackets mounted outwards at 19 degrees from the vertical. Can anyone tell me what effect reducing this angle would have on
things. For example would there be less gain in negative camber during compression?
Thanks
chris
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Rorty
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| posted on 9/8/03 at 03:02 AM |
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If I follow what you're saying, you'd have increased neg in bump, and increased pos in droop with horrible things going on in roll.
It depends at what height you mount the upper inner pivots though.
You'd be better off drawing it in half scale on cardboard, with moving elements (using drawing pins for pivots), and overlaying it on a roll
simulator. That way you can play around with just about all but the lower inner pivots, and see what difference 0.5mm can make (unless you have a CAD
programme, which would be even more accurate).
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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8smokingbarrels
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| posted on 13/8/03 at 11:14 PM |
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Thx Rorty
Sorry didnt explain myself too well- should have said that FU1/2 is angled 19 degree from the vertical. I was thinking of reducing this angle (make
FU1/2 more vertical)because of the large KPI angle that my audi upright has.
However Ive decided to modify the upright (read: chop the crap out of it! ) to reduce the KPI. Ive also realised that i was being a bit thick by
thinking of using trackrod end as the upper balljoint. Since it is going on the BACK of the car- I should use the usual C bracket welded to the top
of the upright and bush/tube on the wishbone. My concern is: will this be enough to stop the wheel turning (inwards/outwards) as the lower part of
the upright will still have the original balljoint.
I can still weld on the steering arm/knuckle and connect this to the chassis as a 'non-steer' system. However as Alan pointed out there
is the problem of bump steer to overcome and id prefer to avoid that one if possible
Hope u all can follow what im blethering on about!
chris
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Rorty
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| posted on 14/8/03 at 03:44 AM |
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Again, if I understand correctly, just employing a narrow double-shear joint at the top of the upright, and a single balljoint at the bottom will not
cut the cheese. You need a good wide base on the upright to accomodate the twisting forces,
Perhaps you could weld a length of hollow bar to the bottom, and thread the ends to take rod ends in single shear.
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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