Premier President 1973

[yaser_cyclist]

chk a fiat at this link:

http://www.delest.nl/media/img/DCP_0617.JPG

probably in new zealand? going by the site address... notice, its LHD

Yaser

[1100D]

Ha Ha the car behind this car is the "REAL" car. Gosh why didn't we have PAL joining forces with them earlier!

[1100D]

Originally Posted by ram

BTW, camber is designed to get the kingpin axis (when produced downward) to coincide with the tire contact patch on the road.

Is there anyway (other than wearing out of the kingpin) that the Kingpin axis incliniation will change with respect to the wheel (camber) axis?

For people without the knowing, Kingpin is the "pin" or so to say the axis on which the hub moves right to left. To observe, please take off one front wheel, and follow the steering movement, how the steering linkage makes the arm on the hub move to left to right, the fulcrum of this movement of the hub is the kingpin axis.

Have anyone noticed that on a Static car, when you turn the wheels either way the car lifts up!

Anyway Ram sir, do we have the specifications as to the distance between the left and right mounts for the upper arm. For my car I did it the crude way of comparing with another baselined car. But since my cars alignment specs matched exactly with the data available with the Manatec machines (with the driver load) I was quite okay with the crude way employed!

Anyway the Bush kits are available freely and are manufactured by VIR.

[Stanher]

Originally Posted by yaser_cyclist

chk a fiat at this link:

http://www.delest.nl/media/img/DCP_0617.JPG

probably in new zealand? going by the site address... notice, its LHD

Yaser

Actually "nl" would mean Netherlands (Holland).......which explains why the car is LHD.....NZ has RHD cars just like we do....

Lovely car, even though white isnt exactly one of my favourite colours!

[moralfibre]

Originally Posted by 1100D

Have anyone noticed that on a Static car, when you turn the wheels either way the car lifts up!

Doesn't happen in my Palio because of the design. To know what I am saying open the hood and turn the steering lock to lock and check the movement of the struts . I can't give a technical explanation like you guys but the movements of the Strut are very interesting to see.

[yaser_cyclist]

U r right Stanher - nl is for netherlands, I noticed that after posting the link and wow looks like you can find this beauty across Europe(bet its already a classic there by now) and even in US people recognize it.

Makes me even more proud to drive and and also to be a part of this forum and discuss it out with you all guys.

hey! anyone else has more pictures? Please share.

Yaser

[Ram]

Originally Posted by 1100D

Have anyone noticed that on a Static car, when you turn the wheels either way the car lifts up!

Actually on the contrary the car will stand tall and level only when the front wheels are pointing straight ahead.
At any other angle the car will stoop down.
Why?
Cars have positive castor (like hospital bed wheels), to get them to automatically straighten out after completion of a turn. However, the positive castor is achieved by tilting the kingpin axis rearward.

This causes the entire front end to stoop when the wheel supporting it up is steered. Haven't you seen a motorcycle lower its front when you steer the front wheel while locking the handlebar?

Look at the geometry in the figure.



There's more!
As each front wheel deviates by a different angle with the direction of the car, the two front corners will stoop down by different extents.
In fact, the corner inside the turn will stoop more than the outer corner.

Ram

[V-16]

Originally Posted by yaser_cyclist

U r right Stanher - nl is for netherlands, I noticed that after posting the link and wow looks like you can find this beauty across Europe(bet its already a classic there by now) and even in US people recognize it.

Makes me even more proud to drive and and also to be a part of this forum and discuss it out with you all guys.

hey! anyone else has more pictures? Please share.

Yaser

Yaseer please check this link.. it has loads of pics do go through the entire thread, it has pics in almost all pages... ..enjoy!

http://www.team-bhp.com/forum/modifi...tml#post485086 (1961 Italian Fiat 1100/D Special. A Restoration Project.)

[1100D]

Originally Posted by ram

Actually on the contrary the car will stand tall and level only when the front wheels are pointing straight ahead.
At any other angle the car will stoop down.
Why?
Cars have positive castor (like hospital bed wheels), to get them to automatically straighten out after completion of a turn. However, the positive castor is achieved by tilting the kingpin axis rearward.

This causes the entire front end to stoop when the wheel supporting it up is steered. Haven't you seen a motorcycle lower its front when you steer the front wheel while locking the handlebar?

Look at the geometry in the figure.



There's more!
As each front wheel deviates by a different angle with the direction of the car, the two front corners will stoop down by different extents.
In fact, the corner inside the turn will stoop more than the outer corner.

Ram

On a bike the stooping is caused by the reduction in the distance between the wheel-ground contact and the ground contact of the steering axis. When the wheel is totally turned perpendicular the distance is zero, hence the wheel center moves down and the upper portion stoops down.

However, in this case the steering axis, is coincident with the wheel-centerline. Not applicable to cars.

In case of a car with the wheel centerline being offset (at the point of suspension), just because of the positive caster, the trailing side lowers and thus pushes the ground below, and the car rises up. Now due to the caster settings and the fact that the wheel center line is outwards from the wheel center-line, the outer wheel center rise and inner wheel center lowers. The car stays lowest at dead ahead position and thus increases its tendency to keep straight ahead with no forces on the steering.

The difference in lateral angle while steering is due to the Toe settings, the inner wheels turn more than the outer wheels.

I can explain the same diagramattically but the super-computer that I am posting this from does not even have a basic paint!!

[1100D]

I have a stapler (thats what I have near me now!) in hand. It is kept absolutely vertical on the stapling line (the way you will staple something). My right hand thumb is on the top arm (of the stapler) and the forefinger on the lower arm. The back of the palm forms the wheel hub. In this position move the palm back and forward on the axis passing through the contact point of your fingers with the stapler. You will obeserve that there is no vertical movement of anypoint of the back of your palm.

Then tilt the top of the staplertowards you (rearward), then when you turn right (meaning the back of the palm moving towards you), you will see points on the back of the palm actually going down. Which will mean, when you fix the palm on solid ground, the stapler will be pushed up. Just the reverse when you turn left (meaning when you move the back of the palm forward).

[V-16]

Originally Posted by 1100D

I have a stapler (thats what I have near me now!) in hand. It is kept absolutely vertical on the stapling line (the way you will staple something). My right hand thumb is on the top arm (of the stapler) and the forefinger on the lower arm. The back of the palm forms the wheel hub. In this position move the palm back and forward on the axis passing through the contact point of your fingers with the stapler. You will obeserve that there is no vertical movement of anypoint of the back of your palm.

Then tilt the top of the staplertowards you (rearward), then when you turn right (meaning the back of the palm moving towards you), you will see points on the back of the palm actually going down. Which will mean, when you fix the palm on solid ground, the stapler will be pushed up. Just the reverse when you turn left (meaning when you move the back of the palm forward).

Very well explained 1100D. I wish i had a geometry teacher like you in school, my grades would have been better..

[1100D]

Interesting reading

Performance > Suspension Tuning > Caster - Nissan 240SX Performance Tuning

This explains it in a different way , increasing the caster to a point where it becomes horizontal (90 degree). When you turn on one side, that side pushes the ground down, meaning car moves up on that side, the other side goes down.

quoting from this

"
When the tires stand up on their edges, the front of the car is actually raised up. This is why the wheels "center themselves" when you let go of the steering wheel. The weight of the car pushes the wheels flat on the ground, which resets the steering. This improves high-speed stability because it keeps the steering firmly in the center position. However, it is difficult to turn a car with a large caster setting because, while turning, you are actually lifting the front of the car with the steering. This effect is most visible in luxury sedans, where high-speed stability is important and sophisticated power steering makes up for the extra steering effort. If you watch one of these cars as the wheels turn to full lock (maximum steering angle), you will see the front end of the car rise slightly."

However I do not agree the shopping cart/hospital bed logic, as a shopping cart/hospital bed turns because of external forces and the axis layout is to help the wheels align to the direction of the forces. But in a case of an automobile, the internal reasons (steering turning) create the forces enabling the vehicle to turn (they are completely different scenarios). Teir logic is better applicable to trailers rather than automobiles.

[Ram]

Originally Posted by 1100D

Performance > Suspension Tuning > Caster - Nissan 240SX Performance Tuning
This explains it in a different way,

This explains correctly, why the front of the inner wheel on the turn raises its corner.

See my diagram. It has my original premise as well as the one with the thick tires.

Originally Posted by 1100D

When the tires stand up on their edges, the front of the car is actually raised up.

It is true that they are raised up. That is a side-effect.

Originally Posted by 1100D

This is why the wheels "center themselves" when you let go of the steering wheel.

That part is not correct. The wheels center themselves because of caster (castor:Brit).
Even were the wheels to be thin discs, they would still center themselves because of caster!

Originally Posted by 1100D

However I do not agree the shopping cart/hospital bed logic, as a shopping cart/hospital bed turns because of external forces

Do you realize, you are dismissing the classic caster explanation.
We are not discussing why the vehicle turns. We are discussing why it returns to straight-ahead after the turn.
The reason is "caster". The whole purpose of why automobile engineering builds caster into the steering-geometry at all is missing in your reasoning!

Aside: I learned about these concepts by playing with different amounts of steer, different caster angles, different camber angles and different toe-in/toe-out angles as a kid. When I was a kid, my father got me from Russia, a tractor model construction kit. It had re-usable painted steel parts, plates, angle girders, wheels, tires, axles and gears, with nuts and bolts to connect the pieces. You could build a front-engined tractor and a rear engined tractor, with working steering gear.

Ram

[Ram]

Before people bring up the camber angle issue, protesting that I don't understand steering geometry, let me state this!

Suspension geometry works in three-dimensions. Caster, Camber and Toe all work in mutual conjunction.

I have exaggerated my drawings to illustrate a point.
My kingpin inclination is at right angles to the vertical.
Actual displacements will be proportional to the cosine of the kingpin inclination from the vertical, and therefore smaller than those illustrated. The diagrams nevertheless illustrate the effects of positive caster.

Camber significantly reduces the lifing effect of the distance between the kingpin axis and the outer edge of the tire contact patch. The downward extension of the kingpin axis should ideally pass through the centroid of the tire contact patch to lighten steering effort.

Ram

[1100D]

Originally Posted by ram

It is true that they are raised up. That is a side-effect.

When was it ever claimed that this was not a side-effect. Read my original post, It was simply being asked if people have observed the lifting effect.

Originally Posted by ram

That part is not correct. The wheels center themselves because of caster (castor:Brit).
Even were the wheels to be thin discs, they would still center themselves because of caster!

Do you realize, you are dismissing the classic caster explanation.
We are not discussing why the vehicle turns. We are discussing why it returns to straight-ahead after the turn.
The reason is "caster". The whole purpose of why automobile engineering builds caster into the steering-geometry at all is missing in your reasoning!

I think the whole lot of the posts above was based on "caster" (castor:Brit) itself. (I dont guess we were discussing Camber by any chance) So where is the confusion. What was being discussed was how caster goes about adding to the centering effect, castor gives rise to lifting which gives rise to "tendency" to center. (However this "tendency" is not dictated by caster alone).

Originally Posted by ram

Aside: I learned about these concepts by playing with different amounts of steer, different caster angles, different camber angles and different toe-in/toe-out angles as a kid. When I was a kid, my father got me from Russia, a tractor model construction kit. It had re-usable painted steel parts, plates, angle girders, wheels, tires, axles and gears, with nuts and bolts to connect the pieces. You could build a front-engined tractor and a rear engined tractor, with working steering gear.

Ram

Wow, you're one of the lucky few in this country.

Originally Posted by ram

Before people bring up the camber angle issue, protesting that I don't understand steering geometry, let me state this!

No body will protest as we are all trying to understand something or the other, if we understood everything we did not need to be on the forum.

Originally Posted by ram

Suspension geometry works in three-dimensions. Caster, Camber and Toe all work in mutual conjunction.

I have exaggerated my drawings to illustrate a point.
My kingpin inclination is at right angles to the vertical.
Actual displacements will be proportional to the cosine of the kingpin inclination from the vertical, and therefore smaller than those illustrated. The diagrams nevertheless illustrate the effects of positive caster.

Camber significantly reduces the lifing effect of the distance between the kingpin axis and the outer edge of the tire contact patch. The downward extension of the kingpin axis should ideally pass through the centroid of the tire contact patch to lighten steering effort.

Ram

Agree to this. However my discussion on posts above was trying to explain the lifting effect caused by Caster (castor:Brit). I did not discuss the Camber. I assume you already know, but still stating this, that the purpose of "camber" is not only to reduce the lifting effects of caster but also to enhance grip/handling while cornering.

But this thread is becoming a great Steering geometry discussion and I guess should not be limited to the confines of the 1973 President.