FEL Stress

jinman · Dec 18, 2003

( I just have a problem with calling it a accumulator. )

Jerry, I'm not sure I understand your "problem" with the term, accumulator. In the hydraulic systems of many airplanes, accumulators provide a damping effect for the hydraulic system. They maintain pressure or absorb shock in the system when sudden surges are felt due to activation of a large cylinder like on the landing gear. The british call them "capacitors" and they function to hydraulics exactly like capacitors do to electric/electronic circuits. I can see that these are really accumulators since they use a precharge of nitrogen. That precharge would be just above the maximum lift pressure of the hydraulics so a spike or shock would be absorbed by the pressurized bladder. I just wonder if the engineer who came up with this method had experience in aircraft. /forums/images/graemlins/cool.gif

slowzuki · Dec 18, 2003

I would like to reinforce the point that none of the ballast reduces stress on the tractor frame! It reduces stress on the front axle.

As for engine and transmission damage, I can't see what they possibly mean. Maybe from a possible rollover /forums/images/graemlins/cool.gif

slowrev · Dec 18, 2003

Slowzuki,
Not sure if this is what you are looking for on engine/transmission damage, but there have been cases of the loader stresses breaking transmission cases and bell housing to engine mounts. Some tractors have actually broken in half /forums/images/graemlins/frown.gif Not a common occurance, but it has/does happen.

slowzuki · Dec 18, 2003

Slowrev, I know about the casting damage but ballasting only increases the stress on the castings. I was thinking maybe increased shock loading from unweighted tires spinning.

Lack of ballast could over load the front axle due to the much increased traction available there. This could damage the tranny or 4wd components. I fail to see how the engine could suffer.
Ken

gsxr1100 · Dec 18, 2003

I was reading all this thread and I agree and disagree with some issues.

Not having ballast in the rear of the tractor will cause a moment; this is why you want ballast. It causes the tractor to “want” to turn counter clockwise. Using the ballast just makes the moments zero.

As far as a force goes, it does not matter if you have ballast or not. The force on the tractor is the same. Having 500 lbs in the front and 400 in back does not make a difference. The tractor does not care if it feels the front and rear weight, still feels weight not matter what you use.

Lastly, as far as welds and stress on the tractor; having the ballast will help lessen the stress on the front end but again it depends on the distance and the weight used. If you have 200 lbs 1-foot from the tractor, that is not as much as if it was 3 feet out from the tractor. You could figure it out pretty easily.

For example, on my BX22 if I had 450 lbs at a 45-degree angle out 6 foot from the loader pins that would cause a 1,900 lb force on the pins. If I used rear ballast @ 5 ft from loader pins I would need around 400 lb to equal the force. But that does not take into account the tractor weight either. So a 200 lb weight would be fine from a force standpoint. Also the changing loader angle will cause different forces felt along with if you are moving.

mahlers · Dec 18, 2003

Total down-force would remain the same, but down-force on the front axle is definitely reduced by putting the ballast aft of the rear wheels. It's the teeter-totter effect.

gsxr1100 · Dec 18, 2003

I agree but 500 on front and 400 on back, you still have 500 no matter what is on the back. You can tell me "teeter-totter" but the tractor still feels 500 on front, period. The front axle will feel some # of weight based on distance from loader pins and weight in loader.

It (weight) is still there but the rear weight makes the tractor thinks it is not there but it is. Even using the example I stated, the loader pins still feel 500 no matter what is on the back. It is reduced but not much. Plus with the tractor weight and operator weight would make the force and moment much less. The weight on the front axle I would say, just throwing # out would be 30 to 40% less total weight at pins.

Again this is for a STATIC situation and not considering the tractor moving. Plus the laoder is not directly on the front but behind the front axle (near the operator by some delta) so really some weight should be subtracted from the total weight. I can figure this out on my BX22 if needed (quick and easy).

Let just throw out the (F) x (d) formula used in Statics. If what you say was true then; if I had 500 on front and 500 on back it would equal zero, but you just now added 1,000 lbs to the overal system. So from the 500 on the front I bet the front still feels 250 to 300 even with the 500 on back or 1000 overall. It is a no win and the front axle still feels in increase in weight. Do the ballast help, sure, but not much.

To close if the engineers designed these tractors so close that we need to worry about stresses on front end (not using their safety factor) they should be shot or fired. Basic design understanding.

yellowsocks93 · Dec 18, 2003

As for the stress on the engine one of the mechanics at the shop has an old 1957 Fordson Major Diesel. It needs a new engine or block assembley becasue the tractor at one point had a loader on it and the guy always rode the clutch. This forced a lot of stress on the engine and the thrust bearring fell out and then some how the block started to get worn down. I am not a mechanic and do not remember all he told me. It was something along those lines.

Currmudgeon · Dec 18, 2003

( It made a point that if you properly ballast the rear of your tractor it would reduce the weight on the front axle and distribute it more evenly upon the entire frame and both axles. )

If you ballast the rear wheels, it should have no effect on the front axle load. If you apply your load behind the rear axle, e.g. a weigh box on the 3PT, then you increase the load on the rear axle in excess of the weight added, and unload the front axle.

If you unload the front axle by adding weight aft, you increase the bending stresses on the frame.

centex · Dec 18, 2003

If you have John Deere then you would tear up the loader before you hurt the tractor since the Deere loaders on the 4XXX series are pretty weakly mounted both to the tractor and to the bucket/forks. Mine is about ready to self destruct. I really wish I had bought a Kubota or a commercial machine. I would have expected the loader to last more than 530 hours especially since I have only used the loader for maybe 125 hours or so. I was impressed at first with how easy it was to remove and replace the loader and the bucket but those are the weak points in the design.