Turning Radius

[chief14]

We are looking at a used International 9600 tanker with tandem axles and a 245 inch wheelbase (center of front axle to center of rear). Any idea of high tight this critter can turn?

[N2DFire]

chief,
You ask a very tricky question that looks simple on the surface.

Turning Radius is a function of Wheel Base and Steering Angle.

For a Tandem Axle rig wheel base is measured from the center of the front Axel to the midpoint between the 2 rear axles.

Also - another point to consider would be the fact that the "curb to curb" turning radius will be affected by the amount of front overhang.

To find that you would have to allow for anything forward of the front axel (bumper, front mount pump, etc).

There was some good discusion on this in the Aparatus Architect forum a while back, but since the search feature is no longer with us, I have had a little trouble finding it thus far.

Also - there was an article in On The Street Magizine regarding Turning Radius. Click here for the web site & Online Article (Adobe Acrobat Reader required to read articles)

Between the two of these and a little web surfing - I think you can come up with an answer, however it may be easier to contact your nearest Navistar (International) dealer and see if they have a spec. book on the truck.

Take Care - Stay Safe
Stephen
FF/Paramedic

[ScottCook]

Or, if you can, go drive it or a similar truck and find out.

Make sure you turn full circles both ways, some trucks turn sharper one way than the other.

[ENG6511]

S.Cook: By Design? If so,why?

[ScottCook]

By design yes. It may be due to what the customer specs going to the front of the truck. Or, it might be poor mfg design in that they simply put an obstruction that prevents the wheel from turning fully one way, but not the other.

For example, a front intake that prevents the officers side wheel from turning as sharp one way because of the obstruction the pipe causes.

I'm not saying it's always that way or pointing any fingers, but it is something to be aware of, to ask about and check in the delivery inspection.

One way to determine it is to do a figure 8, find an area that will leave tire marks, turn the wheels full one way, make a circle and when you come back around, stop, turn the wheels the other way and make a circle. Then measure across each circle. If they have the same turning radius, the measurement will be the same acorss each circle, if they don't, the radius is different (or the driver errored).

I've also seen trucks that can't even make one circle back onto themselves in the same direction. It seemed like the farther you went in the circle, the steering "untightened" and we ended up with what is best described as a loose and open "6" instead of a closed circle ("0").

[ 08-11-2001: Message edited by: S. Cook ]

[distchief60b]

From my experience the "cramp angle" is what you need to examine. The bigger the cramp angle the better it turns... Check with a fire apparatus dealer in your area on cramp angle.