Forum:
Hi all.
A subject that I was tossing over a few evenings ago,after reading an article on equal wheel size 4WD tractors, thought it might have some bearing/implications on 4x4 trucks.
I used to be a farm fitter,responsible for a number of equal wheel size 4WD tractors,and we were incouraged to get the max life out the tyres/fuel, re tyre ballasting, pressures and the correct amount of front ballast.
The tractors we operated, were 60 % front axle/40 % rear axle weight destribution, unloaded. To get max traction we balanced out the weight of the implement, plus ground engaginging drag, which also transfered weight,to get the optimun grip .
My question is - would a 4 x 4 (Fourtrak) benifit from this theory, equalise the percentage of axle weights, to get max traction. ie carry some ballast in the load bay, okay all this is subject to ground conditions,tyre choice, ect. And I may be barking up the wrong tree, but it always seems to be the rears which let go first.
Any thoughts any one.
Edward (ews)
Weighty Issues
Well, a complex issue, but the answer is both yes and no.
Tractors run on what is known as a constant surface, this is a paved road, or what is termed an average mud terrain, this average mud terrain is where the tractor is of balanced operation. Average mud terrain is where the tractor is used mostly, and at its hardest for heavy work duties such as ploughing.
Implements fitted to the rear of the tractor are of varying weight, as well as dimensions, a long heavy implement fitted to the rear exerts more leverage and therefore more loading to the rear end, this is why balance weights are fitted to the front.
Front end implements are far less commonplace, mainly a bucket loader, and various grabs such as bale grabs.
Three point linkages transfer the load from the rear end to the front end of the chassis, a clever design from Mr Ferguson, still used today; based on this theory the rear end should be biased at 60%, and not the front end.
Factor in abrupt weight transfer and the calculations all go totally to cock, add in lateral loadings and this compounds the issue further, to answer the question, there is really no right or wrong answer, and very little benefit to balancing a tractor except for road use when it is travelling between fields.
Tractor manufacturers issue a set of operating instructions, these are a compromise, and act as a starting point only, operaters then work from this point using experience, and a number of misconceptions, as well as practical proven modifications to suit their particular requirements.
Fourtraks would not generally benefit in most conditions, from ballasting; but in certain conditions such as icy roads, a small advantage could be gained from ballasting out the vehicle.
with a tractor with an
with a tractor with an implement on the rear linkage the weight of the implement takes weight from the front wheels to the rear, even to the extent of lifting the front wheels clear of the ground, so tractors are often seen with front weights both to give sufficient weight on the wheels for positive steering and with four wheel drive to prevent wheelslip when the vfront wheels are driving. similar weight transfer occurs with agricultural trailers where the wheels are to the rear of the trailer and there is several tonnes on the tractor drawbar. some four wheel drive tractors are fitted with front linkages to fit a 2nd implement on the front to balence the weight on both axles.
with a front end loader fitted the opposite happens all the weight is on the front axle and the rear wheels spin, we use an old srayer tank on the rear with about a hundred gallons of concrete to provide go anywhere grip on a big two wheel drive loader tractor
with vehicles like the fourtrak the front axle is usually the most laden due to the weight of the engine and gearbox at the front of the vehicle. usually this is not a problem, however in snow or ice it can ge advantageous to put some ballast in the rear, a couple of heavy toolboxes and a welder usually does the trick for me.
Advantage to waight (off
Advantage to waight (off road): More waight forces the tyres down into holes / through top slop to find traction. This is better achived with water balasted tyres, as unsprunge waight holds the tyres to the ground without lowering the chassis over the axles.
Dissadvantage to waight (off road): More waight means axles pulled down into soft stuff, so more likely to hange up on stuff. Also more waight means a lower power to waight ratio, so less grunt per tonn to get you through the muck.
From experiance there is definatly something to be said for a few tools / bags of horse feed / builders sand left in the back when snow is deep and crisp and not so even.
Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.
Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.
it does pay
It does pay to have weight on the rear load bay of normal 4x4's when off roading because of the weight distribution, i have seen it before with hi lux pick ups for example, where all your weight is at the front and zero weight on hard loading springs on the rear create traction problems.Tractors need to be heaviest at the front for implement loads on the rear, but when in work the implement weight is more or less taken off the tractor and placed on the deck, the tracor needs weight on the front to hold down the front of the machine because the implement will lift the front end as the tractor tries to pull and the implent snowploughs into the ground, but this is neither here nor ther i think in comparison, jabbering a bit, the comparison to the 4x4 and the tractor for traction i think comes down to plenty of weight on the back as (especially with heavy diesals) there is ample weight on the front all ready, there is a noticible difference when ploughing through soft wet clay mud down cart tracks with a load bay full and a load bay empty and at that point then comes tyre choice, you may get to a destination loaded but not make it back unloaded, blah blah thats enough writing etc.....:)
Full of ideas but no time to do them!!
www.bloodredoffroad.com
www.milneroffroad.com
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