Theory of rear ballast?

[vtsnowedin]

I would not factor the liquid in the tires. Sure it adds stability and will increase the amount it takes to top the tractor forward. But does nothing to help unload the front axle.

And do you find that number to be accurate? May be different for larger tractors. But I would guess smaller CUT's are closer to 70/30 weight split.

The formula as labeled as talking stability not front axle load which are two different things. It states you need 20% of the total load on the rear wheels. They mean you need this much to have effective braking (in 2Wd)and that also gives you a safety factor against standing the tractor on it's nose. In this case all the weight on the rear tires including the fluid would be included in G.
As to the 60/40 split I don't remember where I read this but it does match the tire load ratings of the tires. If it was indeed 70/30 I would have an increased margin of error.

 

[LD1]

I figured out why I dont like the formula.

It uses loader payload as measured to a lift height of 2m. That number is usually ~ doubled what the spec is for lift to max height. And not a well published spec. Deere is the only one that I know of that lists that number online. My kubota only lists it in the manual.

Either way, it still works out to the counterweight needed being about what the loader is rated to lift max height.

Using your deere numbers, not counting the fluid ballast, it would have you needing 2141#
If using a 70/30 F/R weight split, would have you needing~2600#

Probably closer to the lift capacity @ max height on the loader. Which is my general rule of thumb for counter weight

 

[LD1]

Just did the numbers on my tractor.

Assuming 70/30 split and total weight (not counting tire ballast) of 1600kg

WB is 1650mm, front load 1500mm forward, rear ballast 750mm back. Which would be CL of the ball ends.

Loader lift spec to 2m is 800kg, and actual lift capacity @ pins is 500kg (~1100lbs to max height)

Calcs say I need 1240# rear weight. Bout right. I can hang a 1000# concrete barrel back there and still lift the rears (just barley) if they werent loaded.

Same calcs with the rear counterweight COG 3' behind the ball ends (1650mm behind CL of axle) it says I would require 850# back there. My 7' blade (700#) has a COG of ~36" back, and is not enough until I loaded the tires. But the 1100# 6' bushhog was enough without fluid in the wheels.

So....I think the formula has some merit. But it all depends on how accurately you can determine the weight ratio of F/R of the tractor, and weather you have a 2m spec for the FEL. Which is ALOT more than a Max height spec.

 

[vtsnowedin]

LD1 Moving machine COG back from 60/40 to 70/30 should decrease the amount of counter weight you need both for stability and front axle load relief. When I said my loader would lift 4000lbs that was at the pins at 1.5meters 800mm out in the bucket it is 2891@1.5m and to full height drops to 1956 which is close to equal to the recommended counter weight on the 3ph.
TractorData.com John Deere 5075E tractor attachments information

 

[LD1]

LD1 Moving machine COG back from 60/40 to 70/30 should decrease the amount of counter weight you need both for stability and front axle load relief.

Maybe we are backwards. When I say 60/40 or 70/30 I am assuming the higher percentage is on the front. Thus 70/30 has less weight on the rears, which requires more ballast.

Maybe things are different for your larger machine, but for CUT's similar in size to mine, having the loader on the front, there is little weight on the rears without an implement attached.

1956 which is close to equal to the recommended counter weight on the 3ph.

That is the easy number I use to approximate without doing lots of measuring and calculating. And works well for our smaller tractors IMO. Whatever the loader is rated to lift to max height, put that on the back and you should be good. Ofcourse if that weight is in the form of an implement, you can get by with less, as it hangs further back than a ballast box does.

 

[vtsnowedin]

Bare tractor the COG is usually between your feet and just a little higher then the PTO output shaft. That comes from the weight of the rear end, rear axles and housing plus the rims and tires before any weights or liquid. The engine and transmission acts like a beam between front and rear axles so a loader frames weight would also get split but perhaps not 60/40 depending on where it's bolted on. The loader arms and bucket would all get carried by the front axle and any liquid or cast weights on the rear would only load the rear until you lift the rears off the ground. If the CUTs are different they should have bigger tire on the front.

 

[LD1]

Bare tractor the COG is usually between your feet and just a little higher then the PTO output shaft. That comes from the weight of the rear end, rear axles and housing plus the rims and tires before any weights or liquid. The engine and transmission acts like a beam between front and rear axles so a loader frames weight would also get split but perhaps not 60/40 depending on where it's bolted on. The loader arms and bucket would all get carried by the front axle and any liquid or cast weights on the rear would only load the rear until you lift the rears off the ground. If the CUTs are different they should have bigger tire on the front.

Bare tractor, I would agree with 60/40 with more on the rear.

Adding a loader to a bare tractor shifts that load ALOT forward. It matters not where it is bolted on. It is where the COG of that loader is. And on mine, the COG of an empty loader frame and bucket is FORWARD of the front axle. So it actually takes weight OFF the rear, and adds to the front.

Similar to the 3PH. It dont matter where it is connected to the tractor at, It is where its COG is at.

And I agree, on a CUT sized tractor, the tires can be a limiting factor and easily used beyond capacity. Thus the emphasis on proper counterweight and not just tire ballast

 

[LD1]

https://docs.google.com/spreadsheets/d/19WZJsz9OGbuQU1oD0uQ8je0KtKVyyrur2_ocfLgmWDo/edit?usp=sharing

If that works, its a spreadsheed for that formula. No need to enter front/rear weights. Just enter total tractor weight then a percentage of that over the fronts

 

[vtsnowedin]

Well I do think where it is bolted on does matter but in the case of the 5045E the frame is bolted on about 1/3 of the way back between the axles so perhaps on that weight of 370 lbs I should have gone 33/67 so perhaps I'm 100 lbs off on each axle. So not counting chains and wheel spacers but adding in 100lbs of fuel and 250 of me the rear weighs 3024+920+122+100+250=4416 and the front carries 2016+248+699+451=3414 for a total of 7830lbs and is a 56/44 split. Take a set of truck scales to know for sure but I am satisfied that it is safe and handles well day to day and that a ton on the back would work real well for heavy loading.

 

[LD1]

The only thing that matters about how its bolted is where it shifts the COG of the loader as a unit.

Alot of backhoe loaders are a complete frame that is attached at the rear axle. That dont mean that the load, or anything in the loader bucket gets applied to the rear axle weight.

My money says that if you remove the loader and weigh the rear axle, then re-attach the loader and re-weight the rear axle, with the loader on the rear will weigh LESS. That means the entire weight of the loader arms and bucket + how ever much less the rear weighed is ALL added to the front.

I could be wrong, but I dont see any way you still have over 50% on the rear axle with the loader on. Even with ballast in the tires.