[AT] narrow vs. wide front tractors
Dean VP
deanvp at att.net
Sun Apr 6 12:22:41 PDT 2014
I'm going to summarize the physics of a possible roll-over on our tractors
as described in an article which I am unable to find on the internet right
now. It is a very complex issue and the difference of potential roll-overs
on a Narrow Front End tractor vs a Wide Front End Tractor is stated to be
not nearly as much as we might want to believe. However, there are three
conditions that have to be considered to properly analyze what might happen
and why. These are whether there are any static vs dynamic forces involved.
Static Test:
1.) Test one might be putting both a NFE and a WFE tractor on a rotating
flat plane and then very slowly rotate the plane until one tractor rolls
over. This assumes the tractor doesn't start sliding down the plane.
According to the article I read there isn't much, if any, difference of
plane angle at which the tractors roll over between the WFE and the NFE. On
a crawler tractor the roll -over axis is along the outer edge of the inner
track. On WFE and NFE this roll over axis gets complex very fast. On a NFE
tractor the roll over axis runs from the outside of the rear tire to the
outside of the front tire at ground level. I would suspect it wouldn't make
much difference whether it was a single front wheel of two front wheels
closely together at the front such as Row Crop tractors have that are called
tricycle front ends. Ok, then we get to a WFE and here is where we may have
a misconception about how much safer WFE's are vs NFE's. The Roll over axis
for a WFE runs between the outside edge of the rear tire to the center point
of where the front axle rotates around, higher up under the frame of the
front of the tractor. The front axle rotates before it hits the stop of the
frame. So in all cases the tractor starts rolling over when the center of
gravity passes this roll -over axis. So according to this article there
isn't a whole lot of difference where the roll over axis is between a NFE
and a WFE. The article goes on to say that yes the roll over axis shifts to
the line between the line from the outside of the rear tie to the outside of
the front tire of the WFE when the front t axle hits the stop of rotation
against the frame but they explain that the tractor is already in roll over
condition before that happens. They explain that is why there isn't much
difference between the angle of the plane that causes roll over between a
NFE and a WFE. The bottom line they explain is that most (my personal guess
is over 95% or more) of the tractor stability come from the rear tires.
Lower to the ground and the wider the distance between the rear wheels would
obviously be the best.
Dynamic situations.
According to the article I read two additional issues can come into play and
have more influence while on a side his or for that matter even flat ground
that can cause a roll over.
1.) A combination of speed(centrifugal force) and rate of turn up or down
the slope
2.) Hitting an obstruction such as a rock or sudden elevation change with
either one of the front or rear tires or both on one side with speed and/or
a simultaneous turn adding an additional dynamic influences.
This adds a level of complexity that I'm not going to even try get into here
without being able to reference the original article I read.
But the bottom line of the whole article was that the configuration of the
tractor whether it had a WFE or a NFE was very minor compared to all the
other variables(center of gravity closer to the ground, smaller radius
tires, elevation changes, slope, speed, turning radios and direction of
turn)that come into play. I suspect one of the influences that make a NFE
more dangerous on side hills is that typically it is capable of shorter,
differential brake assisted, turns than a WFE tractor. And at high speeds
turning up hill that could be deadly on a steep slope. I'm really not trying
to say NFE tractors are just as safe, I'm just trying to point out that the
physics of the WFE is often over looked because the front axle rotates on a
WFE tractor before it hits the rotational stop on the frame. That rotational
axis cause the roll over axis line to move inward similar to a NFE tractor
vs say a crawler tractor. I had over looked this issue before when thinking
the WFE tractor had considerably more stability on a slope than a NFE
tractor.
However, I suspect most roll overs are caused by more than just the slope of
the ground the tractor is on. I suspect speed, hitting an obstruction or
turning to quickly in the wrong direction have a huge influence in the
cause of the roll over. All of this above totally ignores the situation
where a front end loader is added to the tractor and when the bucket is
raised which moves the center of gravity much higher on the tractor which
really makes it dangerous at higher speeds and on slopes. But again I
suspect that once a tractor starts to roll over it is before the WFE axle
has hit the stops on the frame and the added benefit of the WFE does not
really come into play since the dynamic forces already in play will continue
to roll over the tractor.
Again, I'm not arguing one type of FE is better than the other but trying to
expose some studies that have shown that there isn't as much difference
relative to roll over potential between the two types (NFE vs WFE) as we
might think. The real bottom line is we need to try to use safe operating
procedures. And, use lower to the ground, wider tread setting on hilly
ground and go slower to try to keep the centrifugal forces at bay.
Dean VP
Apache Junction, AZ
" . . . The tree of liberty must be refreshed from time to time with the
blood of patriots and tyrants. It is it's natural manure . . . " Jefferson
-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Dean VP
Sent: Friday, April 04, 2014 6:06 PM
To: 'Antique tractor email discussion group'
Subject: Re: [AT] narrow vs. wide front tractors
Herb,
We are presently in AZ but the mud slide was about 30 to 40 miles N from our
home in WA which we will be back at in about a week. I did find some data
that I had captured off of a web site relative to the stability of WFE vs
NFE tractors. I'm presently trying to find the web site and the referenced
tests. Knowing the members of ATIS, unless I can attribute the data to a
formal test it probably wouldn't be wise to publish the data.
Dean VP
Apache Junction, AZ
" . . . The tree of liberty must be refreshed from time to time with the
blood of patriots and tyrants. It is it's natural manure . . . " Jefferson
-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Herb Metz
Sent: Friday, April 04, 2014 4:43 PM
To: Antique tractor email discussion group
Subject: Re: [AT] narrow vs. wide front tractors
Dean,
Good to hear from you.
Last week several posts were about the WA landslide, and your situation.
Were you or your property close to the tragic landslide in WA?
Also, hope you can find and share that published study about stability of
WFE/NFE tractors. I imagine some of us will be quite surprised about parts
of the findings.
Herb
-----Original Message-----
From: Dean VP
Sent: Thursday, April 03, 2014 11:01 PM
To: 'Antique tractor email discussion group'
Subject: Re: [AT] narrow vs. wide front tractors
Greg,
There is a thought process that a WFE tractor is more stable on hilly
terrain that a narrow front end tractor and that may be one of the reasons
it is regional. Another might be that one area wanting narrow FE tractors is
more oriented to Row crops and farmers wanted more front mounted implements
such as cultivators. There has been some studies made of how stable a WFE
tractor is compared to a Narrow front end. I found some published studies
on this on the web and the results are really surprising. When I have time
I'll try to find that study.
Dean VP
Apache Junction, AZ
" . . . The tree of liberty must be refreshed from time to time with the
blood of patriots and tyrants. It is it's natural manure . . . " Jefferson
-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Greg Hass
Sent: Thursday, April 03, 2014 7:16 PM
To: at at lists.antique-tractor.com
Subject: Re: [AT] narrow vs. wide front tractors
Since things are a little slow on the list I will ask something that has
bothered me for quite some time. I suspect the answer is somewhat regional,
but here goes. First of all, this applies to older tractors; but why do some
areas lean heavily to narrow fronts and others to wide fronts? In our area
of Michigan, IH starting with the late letter series and JD starting with
the early numbered series, almost everyone bought wide fronts; whereas in
other areas,I'm thinking maybe Indiana, people stayed with narrow fronts. As
an example, google "plowing of the past 1962" and you will see what I mean.
In this video, the sound does not start for 30 seconds. Almost every tractor
is narrow front, although a town is mentioned, I am not sure what state the
video was in. I have driven both types and I personally hate narrow fronts.
When Farmer was on the list, I know he said his 4010 or 4020, I forget
which, had a narrow front. So my question is, why do certain areas seem to
favor one or the other, and also those of you on this list, why do you
prefer one over the other?
Greg Hass
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