Alan B
|
| posted on 14/1/03 at 04:22 AM |
|
|
Ackerman
Guys, on the locost theory list, one guy is saying is that most wheel alignment people he knows have never even heard of ackerman.
I said "wow. scary, what sort of course or training have they had?, surely they must have at least heard of it?"
My question: Am I right to be surprised? Should someone performing wheel alignment at least have HEARD of ackerman?
Opinions or experience please particularly from those in the business...
Cheers.
[Edited on 14/1/03 by Alan B]
|
|
|
|
|
Mark Allanson
|
| posted on 14/1/03 at 08:00 AM |
|
|
You are right, Alan, most fitters only know the theory of how to adjust what is already there, and know nothing of the design principles involved.
Ackerman, doesn't he have a chat show in the states?
|
|
|
jollygreengiant
|
| posted on 14/1/03 at 08:07 AM |
|
|
Alan.( sorry everyone I gone on agian.)
No you are wrong to be surprised, (IMO) most people that "do" wheel alignment are not a lot more than underqualified & over glorified "tyre
fitters" and the companies that employ them as such are purely motivated by the revenue that they can earn by doing a tracking because it is all
profit. A quick fix then on with the next one.
Not only am I a City & Guilds tech but I am also an Examiner (C&G) for Tyre & Exhaust fitting. I had cause a while back when I was between work (OK
unemployed) to be tutoring & testing unemployed people for these jobs so that they could get work. A lot of them said that they wanted to work with
tyres because tyres were CLEAN?!.
When it comes to tracking, a knowledge of ackerman angle is not 'necessary' but could be useful. However mechanical {*$%^*"%^&*** just poured
coffee on my cornflakes ******} should really be a must. How many times when you've noticed tyre wear have you gone in for tracking and its has just
been 'adjusted'. Tracking should never change. There are only two reasons why it alters.
1. Your car has hit something, OK then whats bent or broken, so you need to get the wheels clear of the ground so that you can check for damage.
2. Some component(s) have worn. Check underneath again.
In either case but especially the latter there is no point in adjusting the tracking becuase what ever you adjust it to, the suspension 'Geometry'
will still be out. In most (but not all) companies the higher management just want their trained 'specialists' to do the tracking with out any
checking first, why, becuase to check a car first takes up valuable ramp time & the customer is only paying for the adjustment.
Sorry Alan & the rest but I think I know where my daughter gets her Rattle on ability from.
Enjoy
|
|
|
stephen_gusterson
|
| posted on 14/1/03 at 10:56 PM |
|
|
loved the cornflake bit jolly.
Ackerman, as far as I have read, is the angle of the steering arms, that should project rearwards and intersect behing the rear axle somewhere?
If this is the case, then it doesnt seem in any way adjustable, so I cant imagine a alignment shop would know anything about it!
Tyres are not always fitted by less educated people - I have known people on degree courses that work p/t in them to raise some cash.
atb
Steve
|
|
|
jollygreengiant
|
| posted on 14/1/03 at 11:07 PM |
|
|
Yep it's only adjustable by changing the location of the axles relative to each other. or changing the width of the front suspension. Or if you are
really up for it, building your own front hubs with steering arms. There are a few cars where the steering arms bolt on, so by shimming front/rear
bolts you could change the angles slightly.
What those who have built/are building, are doing is making the greatest changes cos the axles are moving closer together and the front track is
narrower.
The cornflakes werent that bad.
Enjoy.
Un-employed does not equate to un educated. Sorry but I was not casting dispersions on peoples educational abilities.
[Edited on 14/1/03 by jollygreengiant]
|
|
|
stephen_gusterson
|
| posted on 14/1/03 at 11:21 PM |
|
|
quote:
Originally posted by jollygreengiant
Un-employed does not equate to un educated. Sorry but I was not casting dispersions on peoples educational abilities.
[Edited on 14/1/03 by jollygreengiant]
I didnt mean it to sound that way! Must have mis-interpreted your post.
btw - did YOU see the 'reliant' article I spoke of earlier?
atb
Steve
|
|
|
jollygreengiant
|
| posted on 14/1/03 at 11:27 PM |
|
|
Steve. Nope.
Steve. I Meant Thomas Flawn area.
Boyo.
Enjoy.
[Edited on 14/1/03 by jollygreengiant]
|
|
|
Rorty
|
| posted on 15/1/03 at 02:44 AM |
|
|
Ackermann principal is always one of the most hotly debated subjects anywhere petrolheads congregate.
I have researched it extensively over the years, and combined with my own experiences, rarely give it a second thought.
Rudolph Ackermann was a German publisher who’s father had a coach building business. Old Rudy didn’t actually invent the principle, but patented
it.
The principle is, as was stated by Steve, that by angling the rearward pointing steering arms to theoretically intersect the centre of the rear axle,
the inner front wheel turns about a smaller radius than the outer front wheel.
So simple it was perfect. Well, at least for 19th century horse-drawn carriages with narrow iron tires. The problem is that nowadays there are wide
rubber tires with much larger slip angles; so modern car manufacturers use 'modified Ackermann'. This can range from the steering arms intersecting
a point about a car's length aft of the rear axle, to the arms actually being parallel to each other.
A lot of race cars, and fast road cars use reverse Ackermann, whereby the outside wheel turns more acutely than the inside wheel. This works better
for sports cars with stiff suspension because of the more heavily loaded outside wheel when cornering at speed.
You may want true Ackermann on your Locost, but as Jolly points out, by the time you mix and match parts from various manufacturers, and install them
on a short chassis, the chances of having anything remotely like true Ackermann are extremely slim. You can always heat the steering arms to a nice
cherry red, bend them, heat them again, and before they cool, bung them in a hot oven and turn the oven off.
There’s no doubt, Ackermann is very handy at low speeds while parking etc, but when out on the road, you won’t feel any untoward effects.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
|
|
|
Alan B
|
| posted on 15/1/03 at 04:20 AM |
|
|
quote:
Originally posted by jollygreengiant
.......... Tracking should never change. There are only two reasons why it alters.
1. Your car has hit something, OK then whats bent or broken, so you need to get the wheels clear of the ground so that you can check for damage.
2. Some component(s) have worn. Check underneath again.......
JollyGG, I'm glad to hear someone else that, it's what I always thought too......there just is nothing to go out of adjustment...it's either bent
broken or worn.
Good thread this
Oh yeah, I started it....
[Edited on 15/1/03 by Alan B]
|
|
|
johnston
|
| posted on 15/1/03 at 10:31 PM |
|
|
does only adjusting 1 track rod when settin the alignment not bugger up the ackerman 2
and how many of the aligment guys no bout the thrust angle
|
|
|
Mark Allanson
|
| posted on 15/1/03 at 10:42 PM |
|
|
It throws out he toe out on turns, which is basically the angle of the inner wheel of a turn varies from left to right. The is because the rack is no
longer central, ok on a straight line but the car will handle differently on left and righthand corners
|
|
|
jollygreengiant
|
| posted on 15/1/03 at 10:49 PM |
|
|
Ackerman angle is set by the angle between the longitudinal plane, when viewed from above,of the pivot axis of the front wheel and the angle of the
arm to that plane on to which the track rod end connects and with the tracking set to within limits in the straight ahead position this angle will not
change unless something else is bent/worn/broken.
So if you adjust one track rod and leave the front wheels parrallel relative to the rear so long as the individual front toe in/toe out angles all add
up to within tollerance then the ackerman angle will be ok. That is nsf = -6 mm osf = + 6mm alignment if rearwheel are showing the same offset is then
0mm.
God I hate doing/explaining alignment.
Enjoy.
|
|
|
