[AT] Tractor safety

Mon Sep 2 09:11:25 PDT 2019

Under identical conditions, and with the same rear wheel spacing and weight distribution, identical WFE and NFE tractors will have different roll over characteristics. The reason is that in order for a tractor to roll over there has to be a rotational moment applied. The rotational moment occurs as one of the rear wheels comes off of the ground. 

Now consider a man standing on two legs and somebody pushes him from the side at his shoulder. At the time of the push a rotational moment is being applied to his shoulder, trying to tip him over. One of his feet may come off of the ground, but he should be able to stay standing.

Now consider the same man standing on one leg and the same push is applied to his shoulder. He’s going to have a harder time staying upright.

If you could find some people who would be willing to test their tractors on a tilt bed, and who had the necessary parts to change their WFE to a NFE (I know that older Farmalls can be switched between WFE and NFE with some simple bolting work) you could get all the data you need to put this issue to bed.

You could attach strain gauges to the safety chains/cables of the test bed and determine the amount of rotational moment it takes to cause a specific tractor to roll. It would be nice to get a variety of tractor types and sizes to see how tractor manufacturer/size affects the the rolling over concern.

----- Original Message -----
From: Dennis Johnson <moscowengnr at outlook.com>
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Sent: Mon, 02 Sep 2019 11:29:09 -0400 (EDT)
Subject: Re: [AT] Tractor safety

Years back I was involved in doing some testing for rollover stability with oil field equipment. We went to a Nevada test facility (I think owned by Hodges trucking) where  many auto companies do various testing. One test was to put a vehicle on a tilt bed, and raise one side until the tires came up and vehicle started to roll over. We had chains to stop the rollover.
It would be interesting to have a day with that test stand, and a few tractors to test. Would need to have 2 tractors identical except for the front end configuration to get good results.
Those results were basically static without any forward motion, but would still give some accurate results.

Dennis

Sent from my iPad

On Sep 2, 2019, at 10:09 AM, Jim Becker <mr.jebecker at gmail.com<mailto:mr.jebecker at gmail.com>> wrote:

As I recall, the difference between the front pivot point for a NFE being on the ground vs. at the pin of a WFE axle was George’s primary argument.  My argument was that with 2/3 to 3/4 of the weight on the rear axle, this difference wasn’t very significant.  Besides, the pivot point on a WFE is at the center.  With a NFE it is at the low side front tire (with dual fronts), which cancels out part of the WFE advantage.

I tried, during one of these discussions, to find a reliable university study of stability.  I only found one that had gathered any hard data by rolling some tractors over.  I contacted the primary author to see if they had anything on wide vs. narrow.  From his reply, it was clear the question hadn’t even occurred to them.  He then added words to the effect that obviously a WFE was safer.  It was also clear that his reply was not thought out and lacked any consideration for the fact an axle pivot even exists.

Jim Becker

From: Dennis Johnson
Sent: Monday, September 02, 2019 7:21 AM
To: Antique Tractor Email Discussion Group
Subject: Re: [AT] Tractor safety

The significant difference between a wide and narrow front is the height of the “pivot point” on the front end. A narrow front pivots close the the center of the front tires on the ground. A wide front pivots on the front axle pin, which is close to 2 feet above the ground, until it hits the stops. After it hits the stops things change.

Dennis

Sent from my iPad

On Sep 2, 2019, at 2:26 AM, "deanvp at att.net" <deanvp at att.net> wrote:

Howard and Jim,

Many years ago right here on ATIS I published a link to the engineering study  that showed the roll over potential difference between NFE vs WFE.  As I recall it was a study accomplished in some other country other than the US. For some reason I want to say Australia but that may be a fig newton of my imagination. A few years ago this subject came up again here on ATIS and I tried to find the published information but didn’t have luck then.   Maybe someone who knows how to do a really good search on ATIS Archives can find my reference link.  I’m guessing it was well over 10 years ago maybe even 15 years ago.  The tests were very well documented and the Engineering Science was included showing how the COG changed between the two front ends, before and during a potential roll.  It was a very well done engineering piece of work.  I’ll do some web searching again and see if I can find the article.

Dean VP
Snohomish, WA 98290

From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of Jim Becker
Sent: Sunday, September 1, 2019 10:10 PM
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Subject: Re: [AT] Tractor safety

I thought I was the only one that had that repeated argument with George.   My assertion was that any advantage a WFE might have was inconsequential.  By the time a WFE hit the stop, you were already near, if not past the tipping point.  None of us had any hard data to back up our opinions.

Jim Becker

From: Indiana Robinson
Sent: Sunday, September 01, 2019 7:47 PM
To: Antique Tractor Email Discussion Group
Subject: Re: [AT] Tractor safety

Hi Dean:
You or some other long time members here might recall (or maybe not)  :-)  me having a friendly disagreement years ago with my old friend George Willer with me trying to make the exact same point about not encouraging wide front operators to become over confident on hills.
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