Rear wheel width setting vs. Bucket Width

[CobyRupert]

No that's impossible. The line of rotation is from outside edge of rear tire to outside edge of front tire. If the COG is outside that line, stops or not ,she’s going over.

Yes, this is true. What I was trying to convey was a scenario where the cog is towards the front and inside this "front tire to back" (plan view) line, but looking at the cog location from the rear "elevation" view it appears to be outside a vertical line drawn up from the outside of the rear tire (only). That is the horizontal distance between the rear tires is narrower (cause they're tipped) than the wider front. i.e. on the image, imagine the front wheels are the back and vise-versa (cause only the back is tipping) and the cog is effectively located right up next to one of the front tires (in plan view), it would "appear" from a rear "elevation view" to be outside the rear tires. (We are way into the theoretically "could happen" zone here!)



ovrscd: "This leverage can work against you too. If on a sidehill and the upper front tire rides up on an obstacle far enough to cause the axle to oscillate to the stopper it will have increased leverage to try to tip the tractor over." - Good point!

 

[jimmysisson]

Fact is, when you dig into a pile you want the fronts well narrower than the bucket so they don't hamper digging in. Set the fronts for convenience and the rears for stability. My $.02
And don't forget as someone said that the rears may not fit through where the bucket might.
Jim

 

[TerryR]

The line of rotation is from outside edge of rear tire to outside edge of front tire.

Actually it's not until the front axle hits the stop. Until then the line of rotation is from the outside edge of the downhill rear tire to the pivot point of the front axle. That's where the rotation happens until the front axle hits the stop. If that weren't the case the uphill front tire would lift before the stop is hit, and of course it doesn't. Once the stop is hit the line of rotation is as you describe.

So, the uphill rear can lift off the ground while both fronts stay put because the line of rotation runs through the pivot point of the front axle. Once the stop is hit, the line of rotation shifts downhill to the downhill front tire, making the tractor more stable, in theory. But the rotation has already shifted the center of gravity down hill somewhat (assuming a load in a low bucket in the FEL isn't counteracting), and is rotating with some momentum. So the shifted CG may now be outside the line of rotation even after it shifts from the pivot point to the downhill front tire, and even if it's not the momentum already gained may carry it over.

Terry

 

[ovrszd]

Actually it's not until the front axle hits the stop. Until then the line of rotation is from the outside edge of the downhill rear tire to the pivot point of the front axle. That's where the rotation happens until the front axle hits the stop. If that weren't the case the uphill front tire would lift before the stop is hit, and of course it doesn't. Once the stop is hit the line of rotation is as you describe.

So, the uphill rear can lift off the ground while both fronts stay put because the line of rotation runs through the pivot point of the front axle. Once the stop is hit, the line of rotation shifts downhill to the downhill front tire, making the tractor more stable, in theory. But the rotation has already shifted the center of gravity down hill somewhat (assuming a load in a low bucket in the FEL isn't counteracting), and is rotating with some momentum. So the shifted CG may now be outside the line of rotation even after it shifts from the pivot point to the downhill front tire, and even if it's not the momentum already gained may carry it over.

Terry

Well stated. That's been my point thru this discussion. A wide front tractor is no different than a tricycle until the front axle oscillates to the "stop". Then the formula changes and it's more stable.

The diagram posted above is inaccurate because of this.

 

[vtsnowedin]

Well stated. That's been my point thru this discussion. A wide front tractor is no different than a tricycle until the front axle oscillates to the "stop". Then the formula changes and it's more stable.

The diagram posted above is inaccurate because of this.

Please don't kill yourself trying to prove me wrong on this.

 

[vtsnowedin]

Fact is, when you dig into a pile you want the fronts well narrower than the bucket so they don't hamper digging in. Set the fronts for convenience and the rears for stability. My $.02
And don't forget as someone said that the rears may not fit through where the bucket might.
Jim

I'm not following you here. Would not the bucket get full long before the fronts got to the pile? As to the rears fitting into the path made by the bucket: I ran a four foot wide bucket for years on a seven foot wide rear tread tractor. No problem at all taking a bucket on the left then a bucket on the right and working an eight foot wide face.

 

[ovrszd]

Please don't kill yourself trying to prove me wrong on this.

What?? I didn't know I was on a mission to prove anything??? Thought we were discussing theories??

 

[vtsnowedin]

What?? I didn't know I was on a mission to prove anything??? Thought we were discussing theories??

OK I'll try again. The wide front end is Always better, all the time. It averages two points on the ground that are several feet apart so one wheel falling into a hole has only half the effect of a narrow front end dropping into the same hole. Even before it hits the stops the line of rotation runs to the low side tire not the pivot pin. When making a turn the wide front tire is in line with the turning force where it can resist that force in compression instead of being behind it. Think of it as a lever trying to right the tractor as it tips to the side. The narrow front end has a four inch lever arm while the wide front end has perhaps 36 inches That’s a nine to one advantage. And the inside tire has that same lever arm being pushed down on it by the weight of the tire and rim.

 

[ovrszd]

OK I'll try again. The wide front end is Always better, all the time. It averages two points on the ground that are several feet apart so one wheel falling into a hole has only half the effect of a narrow front end dropping into the same hole. Even before it hits the stops the line of rotation runs to the low side tire not the pivot pin. When making a turn the wide front tire is in line with the turning force where it can resist that force in compression instead of being behind it. Think of it as a lever trying to right the tractor as it tips to the side. The narrow front end has a four inch lever arm while the wide front end has perhaps 36 inches That’s a nine to one advantage. And the inside tire has that same lever arm being pushed down on it by the weight of the tire and rim.

I hear ya. But your theory is just not mathematically correct. On a wide front tractor, until the front axle oscillates to the stops, the balance of the tractor isn't affected by how wide the front tires are set. That only happens when the axle hits the stops.

As for a wide front handling uneven terrain smoother, yes it does, for the reasons you talked about.

With a wide front on a sideslope, when the tractor tips to the point of contacting the oscillation stops, then the width of the front tires comes into play. And will most certainly add stability to the tractor.

Unless, like has been discussed before, the upper side tire rides up on a hump, or the lower side tire falls into a hole big enough to hit the stopper, then the wide front applies the leverage you are talking about and actually contributes to the tractor tipping sideways, downhill.

To prove this theory, load your FEL with as big a load as your tractor will handle on flat ground. Then while on flat ground, drive one front tire off into a ditch deeper than the front axle can oscillate to overcome. As soon as the tire going into the ditch loses contact with the gound the balance of the tractor changes dramatically, and in most cases the opposite rear tire will lift off the ground until the front tire returns to solid footing or the tractor tips over, whichever happens first!!! At this time the lever you talked about comes into play and contributes to the rollover of the tractor.

But don't mistake what I'm saying as being in favor of a tricycle tractor. I'm not. They are inherently dangerous. Not because they will start to tip sideways quicker, but because they have no safety net (wide front) to catch them once they start tipping.

 

[vtsnowedin]

Well I tried. :banghead: Consider if you will your wide front tractor parked sideways on a large tilt bed. Nice even plane under all four tires. Now tilt the bed until the tractor is just about to roll. The front axle is still on the same plane as the rear tires and nowhere near the stops. But the tractor is ready to roll because the center of gravity has reached a position in the vertical plane that is determined by the line from the lower rear tire and the lower front tire. If the tractor had a narrow front end it already would have rolled as that plane would be closer to the COG to begin with.