Technically maximum permissible mass

[Waffles]

In anticipation of becoming a first time tractor owner I started reading the owners manual for MT225HE.

I'm not sure if it is due to the fact I'm not familiar with tractor lingo, or is something being lost in Korean to English translation.

Does anyone know the correct way to interpret this information?

My best guess is for a safe and stable ride you should not exceed 5033 lbs. prior to placing any load in the bucket.
A safe working load carrying full bucket should not exceed the front and rear axle weights 2564 and 3869 lbs. respectively. 6433 lbs. total.
Allowed to move a maximum loader load a short distance, such as unloading a pallet from a truck to the ground, not to exceed front axle weight 4398 lbs.

 

[oosik]

I got to admit - I've never seen specs listed in this manner. At least for the front axel carrying capacity - the weight of the loader frame and bucket must be subtracted from the 2564 pounds. That's likely to bring the lift capacity of the bucket/FEL combo to around 1000 to 1200 pounds.

 

[KennyG]

It looks to me like 5033 is recommended as the maximum total weight when loaded. If you have the maximum front axle load of almost 4400 (for limited use) the rear axle allowable load would be less than 700 lbs.

Maybe they are discussing everything in terms of mass in case you are operating somewhere other than planet Earth. :confused3:

 

[CobyRupert]

It looks to me like 5033 is recommended as the maximum total weight when loaded. If you have the maximum front axle load of almost 4400 (for limited use) the rear axle allowable load would be less than 700 lbs.

Maybe they are discussing everything in terms of mass in case you are operating somewhere other than planet Earth. :confused3:

They shouldn’t list the ratings in mass, they should list it as force for that exact reason. By listing a “mass”, but the rating the axle can withstand is really a maximum “force”, they are assuming a force based on earth’s gravity (32.17 ft/sec^2).
Obviously if your on the moon, you could add a lot more weight.
Of course, most people couldn’t calculate or estimate the force, so it would be a meaningless number.

Consider this, regarding “mass” vs “force” : What if, on earth, you load the axle to within 100 pounds of max. weight. But then, with good deep lug tires that REALLY bite, you pull at full power.
In some situations, good traction and power can apply more force (to snap an axle), regardless of weight. (Granted, increase weight usually results in better traction, but there are situations you could get this traction without weight)
Hopefully tractor engineers design the axle to withstand full engine/wheel torque at 100% traction, plus tractor weight (x local gravity ) and the listed max load.
...so you can overload the axles as long as you don’t add excess force (engine/wheel torque) while moving right? ...but wait: gravity pulls axle down, whereas engine/wheel torque pushes axle forward, so forces don’t add simply.....plus there the “moments” when you hit a bump to consider. Yeah....just read the manual.

 

[jaydee325]

It's in the translation from Korean to English. Lots of weird statements in my R3039 manual.

Just sub weight for mass. It's no more difficult than that.

 

[Waffles]

I decided to make a model and see how the recommended loads look. I still don't have the tractor in possession so I modeled it from the information I could find, but I think it is pretty close.

I modeled the tractor with the recommended 840 lb ballast. Front axle weight: 1710 lbs. Rear Axle: 2700 lbs. Everything looks great almost 40/60 weight distribution.




Then I added the rated bucket load of 1160 lbs. Front Axle: 3750 lbs. Rear Axle: 1820 lbs. Everything still looks good, front axle is still below absolute maximum 4400 lbs. and weight distribution is better than 75/25.



Then I added what I estimate to be the maximum load the cylinders will lift, 1850 lbs. in the bucket. This is where it becomes concerning. Front Axle: 4960 lbs. Rear Axle: 1300 lbs. Tractor has now exceeded axle capacity and weight distribution is an unstable 80/20.



What is even worse, I simulated maximum ballast the 3 point will lift 1430 lbs. 24 inches behind arms. Front Axle: 4640 lbs. Rear Axle: 2200 lbs. Stability is good at 68/32, but still exceeding front axle capacity.

Does this mean that no matter how well I ballast this tractor, if I go into a pile and the loader goes into relief I might break something?

 

[milkman636]

I’ve seen these types of calculations explained in John Deere manuals previously. Is there any mention of necessary combination tire/wheel ballast and hitch ballast for rated lifts in the tractor or loader manual?

That’s a lot to be able to get right unless they have super good diagrams of all tractor measurements, and a published initial center of gravity for the machine with the factory loader mounted.

The Initial front and rear weight distribution needs to be known for the bare tractor with loader mounted. Then weight and center of gravity of the ballast from the hitch points needs to be known, and the distance from hitch points to center of rear axle, the wheel base, and distance from center front axle to center of load on the loader all need to accurate in order to calculate a new weight distribution. Then if you throw ballast into rear wheels it changes the initial starting weight distribution more in your favor prior to adding the hitch ballast. Are you able to get all those dimensions accurately from the literature you have?

 

[Waffles]

I started with a guess of the bare tractor (no loader) at 40/60 distribution. Center of mass height is a complete guess, but not critical in these measurements on level ground. Wheel base and loader arm dimensions captured well in the manuals. 3PH is a guess from photos that I believe to be within 2 inches which I played around with and the front axle load is not that sensitive to a few inches of rear ballast location.

My largest room for error is my starting assumption of bare tractor weight distribution. If anyone knows what it should be for a MT225E I will make changes.

Ultimately I would like to know how cautious y'all are of over loading the front axle, or do you think there is a large safety factor on the published maximum rating. I'm scared because of the stories of cracking cases.

 

[Rock Crawler]

I crank the hydraulic pressure up on my machine, use the larger "light material" bucket, load it with heavy material until it is heaped over and spilling out and I never give two hoots about axle loads or manual wording. If the rear tires stay on the earth, it's all set. Others may be far far more conservative, but I make mine work for it's paycheck and if it snaps in half or blows up... I'll go buy a bigger one. 500 hours and so far... so good.

 

[CobyRupert]

“Go ‘till she blows!”

Of course they have a safety factor.
What’s the force on the axle when the load in the bucket is only 50% of maximum rating, but you hit a pothole at road speed? Does it exceed the force of lifting 100% load and creeping around the yard? Who knows?
Rating numbers are just a line in the sand someone took a educated guess at. And you can bet they did a CYA.....unless they’re trying to up the numbers to beat the competition.