NF wedge-plate

I got a IHC NF wedge-plate with a bunch of stuff at an auction sale. I have heard a couple of explainations as to what they did for the tractor, but have never seen one installed. What was the real purpose of installing them? Was it to make steering easier? Was it to decrease the amount of front end wobble? Or something else? Also, what is the propper way to mount them? Does the thin end go to the front of the tractor or the rear? Lastly, do they really improve the steering enough to warrent instaling them? Thanks ahead of time.

Leo

The thick to the front.
They increase caster, (like a shopping cart front wheel) they can work to aid stability, but increase steering effort some what at road gear speeds.
It increases self centering.
Real anti wobble is cured by tight shaft bearings in the bolster, wheel bearings with correct preload, balanced good front tires, Steering gear box worm and sector in good adjustment and little wear, Good worm bearings in proper preload, good U joints (and Ujoint to shaft double roll pins)in the shaft, and a steady hand at the wheel. JimN

Some have front marked on them at the thin section. They increase the caster with thin part forward. If you search under wedge plate you can find several posts on the subject. One post had a old advertisement for the wedge, but the picture won't come up for me now. Couple of tractors I had with the wedge did seem to steer better. With these old tractors some steer better than others anyway though.

Shopping carts have negative caster, that is why they are prone to wobbling and going crazy.

Bicycles and motorcycles have positive caster. Positive caster will reduce the wobbling and cause the wheels to WANT to go in a straight line. This is the reason that ALL cars, trucks, and tractors SHOULD be set up with positive caster, just like a bicycle.

In my 1951 edition of "The Tractor Field Book" there are cutaway views of a "C" and an "M". The M has positive castor and the C has a very pronounced negative castor.
In the Lubrication Section of the Owner's Manual for the Super C, there is a diagramatic illustration of the tractor which also shows a negative castor. Would be interesting to know why the variations. Sid.

Leo,
I have one of those wedges on my H Farmall. The thick end goes to the front (some wedges are marked). It's supposed to eliminate/lessen wheel wobble. They were a quick fix years ago but are over-rated and are a bandaid to the real problems causing wheel wobble.
I agree with Janickolson on how to fix the front ends. BTDT.
LA in WI

Well rusty I rarely disagree with you, but you are thinking of the same thing, but not looking at the geometry. Both are a result of having the steering axis lead the contact patch. Casters on a shopping cart go nuts becausw they are worn out and loose. Any one of the degrees of freedom will allow them to get into a self feeding vibration. The pivot on a shopping cart is in front of the contact patch.
In a car (or cycle) the ball joints (or strut) are tipped to the rear to force the contact patch to follow where the axis of the steering projects to the ground.
A narrow front is far more like a shopping cart (doing the wobble thing) than a car or cycle.
Increasing the caster by wedge action is in the same direction as having a caster wheel on a shopping cart with a 4" offset to the rear of the axis. If they put that much offset (caster) in the shopping cart, they would not go nuts. But they would be more easily broken, and take up more space under the cart. JimN

This article, found by doing a Google search, proves MY theory.
http://www.ozebiz.com.au/racetech/theory/align.html

The guy that wrote that article knows a lot of words. It isn't clear if he is confused or just a bad writer. None the less, he does clearly state the positive caster explanation:

Fortunately, it is possible to create castering by tilting the steering axis in the positive direction. With such an arrangement, the steering axis intersects the ground at a point in front of the tire contact patch, and thus the same effect as seen in the shopping cart casters is achieved.

Click to expand...

I never dealt with one of those wedges so I don't know whether you want to add more or remove some positive caster to hide the worn steering problem. But total caster should be positive whether you are dealing with a tractor, car or motorcycle.

Point to JimN.

I guess we need a certified alignment technician to explain it. I can't seem to get my point across, even when I offer proof.

I am one. With respect Jim

I've been through this discussion before here on the forum. I understand positive caster on a motorcycle (an exaggerated example is a long forked "chopper") and I understand positive caster on a car with upper and lower control arms - the ball joint on the upper arm being positioned behind the lower ball joint. In both those cases, the geometry causes the front tire/tires to return to center - or, putting it another way - to steer straight(er) or more true.

But, I still cannot get it through my head how installing the wedge with the thick end forward (moving the tire contact rearward in relation to the axis) can add positive caster. Seems to me it would reduce steering effort, but cause the tractor to be more apt to wander. Also seems to me if the wedge were installed with the thin end forward, turning effort would be slightly harder, but the wheels would be more apt to return to center and not wander as much. I'm sure I've probably got it backwards......

Either way, I have two wedges; one for the M series tractor and one for the H series. Neither is installed on a tractor. The M series wedge has no wording embossed on it. The H wedge has the word "Front" embossed on the [b:ac56994ae3]thin[/b:ac56994ae3] end.

mike

(quoted from post at 19:13:48 02/01/10) I've been through this discussion before here on the forum. I understand positive caster on a motorcycle (an exaggerated example is a long forked "chopper") and I understand positive caster on a car with upper and lower control arms - the ball joint on the upper arm being positioned behind the lower ball joint. In both those cases, the geometry causes the front tire/tires to return to center - or, putting it another way - to steer straight(er) or more true.

But, I still cannot get it through my head how installing the wedge with the thick end forward (moving the tire contact rearward in relation to the axis) can add positive caster. Seems to me it would reduce steering effort, but cause the tractor to be more apt to wander. Also seems to me if the wedge were installed with the thin end forward, turning effort would be slightly harder, but the wheels would be more apt to return to center and not wander as much. I'm sure I've probably got it backwards......

Either way, I have two wedges; one for the M series tractor and one for the H series. Neither is installed on a tractor. The M series wedge has no wording embossed on it. The H wedge has the word "Front" embossed on the [b:006a54c89f]thin[/b:006a54c89f] end.

mike

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Mike, you and I are in total agreement on this issue. That wedge has GOT to be installed with the narrow edge toward the front to produce "POSITIVE" caster.

Mike, you and I are in total agreement on this issue. That wedge has GOT to be installed with the narrow edge toward the front to produce "POSITIVE" caster.[/quote]

It seems that way initially, Rusty, but I am not so sure about that. Look at those two diagrams again in the article you attached. See the vertical dotted lines showing the axis center vs. the contact area? They are the same in both examples as far as their relationship to each other...... I'm not ruling Jim's position out; just that it's hard for me to envision the shopping cart front wheel having positive caster. But, I think he's right - darn it!
Maybe the wedges were designed NOT to stabilize steering, but to ease steering effort on tractors without power steering. mike

Well, looks like I stired the pot on this one. Thanks for all the input. This is for a 300 Farmall. It always steered good and drove straight but had a slight slop in the steering, not bad, but I would have liked better. Last summer I had the radiator reparied, and as always, I checked the steering items when I had it appart. The bushings seemed good. When I reassembled, I tured the steering gear to its best position like I do when I have any of them apart. I also replaced worn bolts in the power steering couplers. When I got it back together, it did seem tighter. I have a mower on this tractor and travel up to 5 miles on roads to mow road ditches. After the maintenance, I could drive a distance, and suddenly the front wheels would start wobbleing, sometimes pretty bad. After a while they would sometimes stop wobbleing, other times they would continue to wobble until I stopped the tractor. There was no consistancey in this at all. It became very frustraiting. I will note that I have the front hub weights on this tractor, but they have been on for a few years now. I thought since I had that wedge lying around, that I would try installing it to see if it helped. Steering effort is of no consiqunce since I have power steering. Like I said, this makes no sence because I thought I should have improved the situation that was already pretty good. I'm temped to remove the front weights, but I like the extra weight and stability in the ditches.

Thanks again, Leo

(quoted from post at 08:17:59 02/02/10) Mike, you and I are in total agreement on this issue. That wedge has GOT to be installed with the narrow edge toward the front to produce "POSITIVE" caster.

Click to expand...

It seems that way initially, Rusty, but I am not so sure about that. Look at those two diagrams again in the article you attached. See the vertical dotted lines showing the axis center vs. the contact area? They are the same in both examples as far as their relationship to each other...... I'm not ruling Jim's position out; just that it's hard for me to envision the shopping cart front wheel having positive caster. But, I think he's right - darn it!
Maybe the wedges were designed NOT to stabilize steering, but to ease steering effort on tractors without power steering. mike[/quote]

O.K. My knowledge of automotive front end alignment, and the difference between positive caster and negative caster, was gained from attending the auto mechanics course taught at Southwestern community college, Creston, Iowa, in the year 1971. We learned, and were tested on all aspects of auto repair, including front end alignment. I still have my text books.

Could it be that the wedge plate was originally designed for reverse operation tractors? And yes, I am aware that reverse operation requires that the lower bolster be rotated 180 degrees but they may have needed additional caster due to a changing center of gravity with heavy permanently mouned equipment.

The word "front" was stamped for a few years until people with worn out steering discovered the plate and put them on forward operation tractors. With this application, the word "front" was now in the wrong place and no longer stamped.

Clipped from a Honda Forum, the following explains it as clearly as I have found.
The issue is centered (no pun) on the idea that on a car the pivot axis is thriugh the spindle. on a Narrow front tractor (with a bolster set perpendicular to the ground) the axis angle is fixed, and the only caster adjustment is in Trail as described below. The more trail, the more positive caster. The Wedge plates installed with thin to front, reduce caster and make steering easier, compensating for the positive caster that the IH engineers built into the tractor. Turning it around Fat in front increases trail, and effort to steer, and resistance to wobble (but not much) With the wheels straight ahead, on concrete, parallel to and near a building, measure from the front bolster to the wall. Now turn the steering full toward the wall and remeasure. The change in the distance is a reflection of caster. Zero caster will be no change, Positive will be Shorter distance to the wall, and negative will be greater distance. (the same as turning a caster wheel by hand and seeing the cart move.) JimN


“Caster is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. If the pivot axis is tilted backward (that is, the top pivot is positioned farther rearward than the bottom pivot), then the caster is positive; if it's tilted forward, then the caster is negative.



Positive caster tends to straighten the wheel when the vehicle is traveling forward, and thus is used to enhance straight-line stability. The mechanism that causes this tendency is clearly illustrated by the castering front wheels of a shopping cart (above). The steering axis of a shopping cart wheel is set forward of where the wheel contacts the ground. As the cart is pushed forward, the steering axis pulls the wheel along, and since the wheel drags along the ground, it falls directly in line behind the steering axis. The force that causes the wheel to follow the steering axis is proportional to the distance between the steering axis and the wheel-to-ground contact patch-the greater the distance, the greater the force. This distance is referred to as "trail."

Due to many design considerations, it is desirable to have the steering axis of a car's wheel right at the wheel hub. If the steering axis were to be set vertical with this layout, the axis would be coincident with the tire contact patch. The trail would be zero, and no castering would be generated. The wheel would be essentially free to spin about the patch (actually, the tire itself generates a bit of a castering effect due to a phenomenon known as "pneumatic trail," but this effect is much smaller than that created by mechanical castering, so we'll ignore it here). Fortunately, it is possible to create castering by tilting the steering axis in the positive direction. With such an arrangement, the steering axis intersects the ground at a point in front of the tire contact patch, and thus the same effect as seen in the shopping cart casters is achieved.

The tilted steering axis has another important effect on suspension geometry. Since the wheel rotates about a tilted axis, the wheel gains camber as it is turned. This effect is best visualized by imagining the unrealistically extreme case where the steering axis would be horizontal-as the steering wheel is turned, the road wheel would simply change camber rather than direction. This effect causes the outside wheel in a turn to gain negative camber, while the inside wheel gains positive camber. These camber changes are generally favorable for cornering, although it is possible to overdo it.

Most cars are not particularly sensitive to caster settings. Nevertheless, it is important to ensure that the caster is the same on both sides of the car to avoid the tendency to pull to one side. While greater caster angles serve to improve straight-line stability, they also cause an increase in steering effort. Three to five degrees of positive caster is the typical range of settings, with lower angles being used on heavier vehicles to keep the steering effort reasonable.”

I-H moved the wheels back for easier steering.