interestedparty
|
| posted on 23/10/02 at 07:59 AM |
|
|
I'm going to think about this some more, and get a second opinion. In the meantime, why haven't you chased Mr Porter for some feedback, and surely
you must have some photos of the real thing?
John
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
|
|
|
|
|
MK9R
|
| posted on 23/10/02 at 08:11 AM |
|
|
I didn't contact him for a while, but after numerous attempts to get hold of him i gave up. He was always a bit like that.
I have got some photos in my disertation. Next time i visit my parents i will hunt it out of their loft.
|
|
|
Dunc
|
| posted on 23/10/02 at 08:20 AM |
|
|
John,
the motion of the trailing arm isn't circular it's spherical. As is the joints at the top and bottom of the wishbones. The wishbone motion relative
to the bushes is circular. As the wishbones move up the castor changes on the upright and possibly the camber too depending on the wishbone lengths.
This design is basically similar to a front suspension system but with the track rod being replaced by the trailing arm. The wishbones do not hold the
upright parallel to their pivot axis.
|
|
|
MK9R
|
| posted on 23/10/02 at 08:49 AM |
|
|
wahey!!
I actually started to think i had got it wrong!
|
|
|
Alan B
|
| posted on 23/10/02 at 02:30 PM |
|
|
If I'm seeing this right then the length change of the trailing arm as it passes through it's arc will cause toe change at the upright?
Deliberate bumpsteer and rollsteer in effect?
Just seeing if I understand
|
|
|
Alan B
|
| posted on 23/10/02 at 02:39 PM |
|
|
I mean deliberate if the geometry is appropriate of course...it may be possible to dial out all the toe change....?
Or you may not want to?
|
|
|
interestedparty
|
| posted on 23/10/02 at 02:46 PM |
|
|
OK, I will now accept that the suspension as shown can move through a short distance without binding. It looks to me as if that upright is going to
have to twist quite a bit in order to accommodate a 50mm bump.
Do you have any figures? especially the lengths of the wishbones and the trailing arm
John
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
|
|
|
wayner
|
| posted on 23/10/02 at 04:18 PM |
|
|
Have a look at the fifth photo down on this site http://www.pilot-odyssey.com/~hoser/web/drakart.htm this setup is pretty good and seems to get lots
of grip, some consider it superior to a conventional twin A arm setup
|
|
|
Alan B
|
| posted on 23/10/02 at 04:31 PM |
|
|
A bit like mine but 1 trailing arm instead of 2 trailing links. Will give castor change...but so what?
simple and effective..
|
|
|
MK9R
|
| posted on 24/10/02 at 07:32 AM |
|
|
quote:
Deliberate bumpsteer and rollsteer in effect?
Just seeing if I understand
Yes. Obviously bumpsteer is not a good thing, but the roll steer could be used to an advantage. It depends what your car would be used for. Both of
this can be minimised/maximised with the geometry set up.
With the relative small amounts of suspension movements in 7 type cars (as it was designed for) i considered the combined advatages of anti squat and
roll steer to outway the bumpsteer, especially as i was intending it to be a setup mainly for the race track.
Once i have finished the MK, i might think about building a one off special with a suspension set up like this.
|
|
|
Alan B
|
| posted on 24/10/02 at 01:43 PM |
|
|
Just curious...is it actually possible to have rollsteer without bumpsteer?
If you find the thesis in electronic form I'd like a copy please..cheers..
(edited for spelling...AB)
[Edited on 10/24/02 by Alan B]
|
|
|
Simon
|
| posted on 24/10/02 at 03:14 PM |
|
|
Andya,
Even though Ron's wishbones may me horizontal to the ground, by their very nature, they both scribe different diameter circles.
The top, being much shorter than the lower, will naturally draw top of upright inwards during compression.
If the top w/bone is inclined, during "de"compression, this should aid keeping the wheel upright (assuming body roll).
I'll pop a doodle in the pic's later.
ATB
Simon
|
|
|
95seped
|
| posted on 28/10/02 at 10:55 AM |
|
|
Ok, I read most of the posts, not all, so sorry if some of this was covered... but here we go.
First, the rear suspension works... it's a front suspension with the steering links (tierods) connected to the chassis. By moving the chassis
position front or rear of the hub you can get bump toe-in or toe-out.
To make your car more stable, you want toe-in. (tie rod behind the hub) Just say you turn right... the left suspension compresses. As it compresses,
you want the left wheel to turn to the right (toe-in).
A book I'm reading, that i suggest is: Chassis Engineering by Herb Adams ISBN: 1-5788-055-7 it's only 130pages, but is easy to understand for the
beginner.
Some basics for independant suspension design for both front and rear (from the book I suggest you buy):
You want unequal length A-arms... top shorter. This provides Camber gain so as the car rolls, the tire stays flat on the ground. Lower arm as long as
possible. Upper is very important... normally between 50%-80% of lower length. If you extend the lines of the a-arms to where they cross (the chassis
mount of the upper A-arm should be closer to the lower A arm then the distance between them at the hub), and measure from that point to the wheel
center you get swingarm length. At ride heigh 100-150 inches is good. I won't go into roll centers... too much explaining... get the book for that.
Wheels should have the most negative offset possible, this is for proper knuckle design.
wide track eguals less weight transfer. this equals more even tire grip = more turning power.
Knuckle design:
Balljoints as far apart as possible (height) for most strength to keep wheel position true.
Kingpin angle (top balljoint in farther than bottom) 5-10 degrees. This centers the steering. The distance between where this line hits the ground and
the center os the tire is scrub radius... we want this to be as close to 0 as possible (this is reasn for high offset tires... gets knuckle inside
wheel)
Caster angle change should be minimal during suspension movement because it causes a change in handling (very important for speedway oval cars) but
should change for anti-dive characteristics. The upper Arms should be angled up at the front to provide anti-dive.
Bump steer..... toe-out in front, toe in in rear... makes understeer which is more predictable to drive.
Springs.... run soft as possible so tires absorb bumps and stay on ground. Run antiroll bars to stop roll. Springs should be stiff enough to stop most
bumps. Run rubber bump stops, they are like variable rate spings, for the big bumps. Springs also need to be stiff enough to provide anti-dive and
anti-squat. Good chassis design will have anti-dive and anti-squat built in (anti squat can only be up to 25% on the IRS, over 100% can achieved on a
solid axle)
For more indepth study, and how to design a suspension I suggest getting this, or another book.
BTW, this is my first post... thought i'd say Hi!.
I live in Canada, and am planning to make a few 7s, one for me and a few (4) to sell to pay for the first. I think I'll make a McSorley 7+442 with
mods like cymtriks mentioned in a chassis strength post. I'm researching the costs, and suspension design is a major thing I'm looking at. I am
planning to design all the suspension parts to get the proper handling. I plan on IRS with common hubs (custom) front and rear to keep costs down
(build 20 of the same thing). Having a full machine shop, aswell as friends in the metal supply, aluminum welding and CNC machining help alot. I also
am restoring 2 1972 Datsun 510s and a 1964 Reily Elf. (see attached)
[img]a15842-mysig.jpg[/img]
|
|
|
Alan B
|
| posted on 28/10/02 at 05:03 PM |
|
|
Good, informative post
Are you also on the Locost North America list on Yahoo?
Good resource.
|
|
|
Alan B
|
| posted on 28/10/02 at 05:10 PM |
|
|
Oh, BTW I recommended someone on TOL to visit here too
By way of balance,,,,
|
|
|
