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p7m8
12-11-2004, 05:38 PM
How are these calculated? Is ROC what can safely be lifted and moved around? How much am I carrying with my LS180 when the back wheels are almost coming off the ground? I usually am lifting logs with my loader and sometimes I find myself going very slowly to avoid tipping forward. Is this the tipping load?

Tigerotor77W
12-12-2004, 01:27 PM
Excellent question. I haven't found one manufacturer that can give a valid, honest answer to this yet.

The rated operating capacity, as specificed by the SAE rules number J818 or 732 (one refers to the other; don't remember which) is that the ROC is rated to be exactly one-half the tipping load of the loader. That's the purely theoretical definition. Now... let's take a look at reality.

John Deere released a video when its 200 series first came out about how their machines were better than the competition. There was a lifting comparison between a 773-F, Case 1845C, and NH Lx665. Now... the 250 was the only machine able to unload and manuever a pallet of sod from the bed of a flat-bed trailer. However, the tipping load of the other three machines were all comparable, which begs the question how manufacturers rate their tipping load. If two machines have the same type of lift geometry and same tipping load, you would expect them to lift the same amount without tipping. That's certainly not the case.

Tipping load and stability is affected by more than just the machine's lift geometry, it seems. Of course, all vertical lift systems differ in how they project the load, but the point is, Deere's machines are heavier. Consequently, they can dumb down the advertised tipping load without sacrificing performance. Bobcat's S175, for example, will tip at 3,900 pounds anywhere in its lift cycle. The Deere 317, however, might not tip until 4,200 pounds -- its machine weight is nearly 500 pounds more than the S175 which will, no matter what, lead to a higher tipping load.

Another factor influencing the tip capacity is wheelbase. A shorter wheelbase makes the machine more manueverable and easier to spin; it requires less horsepower to spin, say, a 553 Bobcat than a 963 Bobcat. However, that shorter wheelbase will also negatively affect the ROC of the machine. The Deere 317 wheelbase is 42.3"; the Bobcat's is 40.6". Although not a big different, those two inches, combined with Deere's professed better center of mass distribution and a higher machine weight yields a skid steer that lifts far more than Bobcat's.

The final issue affecting ROC is lift geometry. Deere's geometry is entirely lift-optimized, not reach-optimized. (Case, Bobcat, and Cat are opposite.) That is, the Deere will lift nearly straight up -- even bring the load CLOSER to the machine at one point -- until the last few inches of its lift cycle, where the loader arms move away from the machine. The Case, Bobcat, and Cat styles lift the load out, primarily; these three do differ a little bit but the concept is up/out rather than up, then out. You can see why, then, given these parameters, the Deere seems to lift more than the S175 at mid height. Where the Bobcat linkage has its maximum reach near mid-lift (flat-bed level), the Deere actually has its linkage closest to the machine.

Now to answer your question: if you are carrying logs with the boom arms raised, it's tough to say what you are carrying. It could be 5,000 pounds; it could be 4,500. If you are carrying them close to the ground, it's probably more like 5,500 or more (possibly). The SAE -- and accordingly, manufacturers -- do not specify where the tipping load is minimized. Where your NH is *supposed* to tip at 5,110 pounds, we don't know where that occurs -- at the top of the lift range, middle, some fraction, etc. It's *supposed* to be at the point where the lift linkage is furthest away from the machine -- but as the Deere example illustrated, publishing a tipping load doesn't mean anything so long as the manufacturer can still find a way to beat the competition somewhere else. So yes, you're pretty much at the tipping load if your rear wheels are coming off the ground. But keep in mind *each height* along the entire lift cycle has its own tipping load; at the ground, where the load is closest to the machine, you have a higher-than-published tipping load. Hence the confusion about exactly how much you are carrying.

Last note -- I used tipping load and ROC somewhat interchangeably here. They're not the same thing.

Hope that helps...

Tigerotor77W
12-12-2004, 01:54 PM
I wrote "Tipping load and stability is affected by more than just the machine's lift geometry, it seems. Of course, all vertical lift systems differ in how they project the load, but the point is, Deere's machines are heavier. Consequently, they can dumb down the advertised tipping load without sacrificing performance. Bobcat's S175, for example, will tip at 3,900 pounds anywhere in its lift cycle. The Deere 317, however, might not tip until 4,200 pounds -- its machine weight is nearly 500 pounds more than the S175 which will, no matter what, lead to a higher tipping load."

The Deere's listed tipping load is 3,700 pounds. This example was to show how operating weight affects tipping load. I also meant to bold the "might" -- I have no idea when the Deere will tip.

I also wrote "Now to answer your question: if you are carrying logs with the boom arms raised, it's tough to say what you are carrying. It could be 5,000 pounds; it could be 4,500. If you are carrying them close to the ground, it's probably more like 5,500 or more (possibly). The SAE -- and accordingly, manufacturers -- do not specify where the tipping load is minimized. Where your NH is *supposed* to tip at 5,110 pounds, we don't know where that occurs -- at the top of the lift range, middle, some fraction, etc. It's *supposed* to be at the point where the lift linkage is furthest away from the machine -- but as the Deere example illustrated, publishing a tipping load doesn't mean anything so long as the manufacturer can still find a way to beat the competition somewhere else. So yes, you're pretty much at the tipping load if your rear wheels are coming off the ground. But keep in mind *each height* along the entire lift cycle has its own tipping load; at the ground, where the load is closest to the machine, you have a higher-than-published tipping load. Hence the confusion about exactly how much you are carrying."

I'm not sure whether the SAE dictates where the minimum tipping load occurs. I'm looking into that right now. It seems to me that the SAE does not dictate this, but again, I'm really not sure.

TerraFirma Excavating
12-12-2004, 03:55 PM
ROC and tipping load will greatly be affected by the leverage of the load on the lifting implement. For example say you are using 48" pallet forks. A machine which can lift a 5,000# 12" diameter pipe will have a load centered 6" ahead of the fork's headache rack. The same machine may not be able to lift a 5,000# fork load of logs with the load centered 24" ahead of the fork's headache rack. My Bobcat pallet forks have a decal stating the "safe" lifting load chart as it is reduced as the load moves further out on the forks.

Are the ROC and tipping loads for machines calculated without any implement on the machine? Or do the manufacturers assume an average weight for an implement? Say a heavy duty bucket weighs about 800# and a set of pallet forks weighs 500#, you should be able to lift 300# more with the pallet forks than with the bucket.

p7m8
12-12-2004, 03:56 PM
Thanks for the reply. When I am carrying logs or stumps I carry them as low as possible if the machine feels tipsy. I'm thinking of getting counter-weights to increase the stability. I always knew I was lifting more than the ROC of 2500 pounds but I didn't think I was possibly lifting 5100 pounds until I looked at the specs. I appreciate your responses.

Tigerotor77W
12-12-2004, 06:04 PM
TerraFirma hit another point that I forgot. Attachments make a pretty BIG difference; yup.

p7m8 -- how large are the logs? (Length and diameter.) If you're looking to stay with the machine you have currently and want to increase your lifting capability, counterweights are the first thing to add, but there are other alternatives out there as well. Foam-filled tires increase lifting capability, as do rear-mounted stabilizers.

Keep in mind that if you're routinely lifting the tipping capacity in some form, you are putting excess stress on the machine's loader arms and bearings, which may lead to premature wear and failure. So if you do plan on lifting that much... remember the *possible* ramifications (not necessarily definite).

cajensen
12-14-2004, 05:49 PM
Yep, I almost ended up in my pond because of that. I had a big rock in my bucket that I wanted to put in my pond. As the rock slid of the bucket it changed the leverage of the load and my bobcat started tipping into the Pond. luckily enough the rock slid off early enough for the Bobcat to recover but there was a moment where I didn't breathe.

Tigerotor77W
12-14-2004, 07:22 PM
Whew... glad nothing bad happened! How did you manage to get the rock out of the pond?

cajensen
12-15-2004, 03:37 PM
I wanted the rock in the pond standing on when fishing.

Tigerotor77W
02-10-2005, 06:15 PM
I found the SAE Handbooks... wow, those things are huge. Bigger than any dictionary; that's for sure!

Two things I want to cover here. This reply will be somewhat subjective and "I would think," so take it with a grain of salt. It may be also very redundant... haha

The SAE J732 standard is the main defining standard of loaders. The tipping load -- purely defined by the book (not quoted; this is by memory) -- is the load at the CENTROID of the bucket, which is elevated to the height corresponding to the forward-most point on the lift cycle, with the bucket rolled back as far as possible without the cross-plane horizontal, and with standard machine weight. What I called the "cross-plane" is the plane that you would see if you placed a 4x8 across the bucket. If you roll the bucket at ground level, for example, on certain loaders this plane would still be tipped toward the machine. Machine's operating weight I don't remember perfectly, but it's with full fuel, 75 kg operator, and all the fluids as prescribed by the manufacturer. Okay, back to 732: let's suppose you're on a radial-lift loader and raise the bucket to about mid-height, where the horizontal distance between machine and load is farthest. Let's say that the tipping load for this radial-lift machine is 3,700 pounds. Now go on a Deere 317 whose tipping load is also 3,700 pounds. At MID-HEIGHT, the Deere will be able to lift more -- that's not where it's maximum forward reach occurs. However, at the top of the lift cycle, where Deere's linkage pushes the load out a bit more, the radial-lift machine *may* have a slight edge. Of course, the trick, then, is to get the load up that high without tipping. I hope that clears things up a bit about the published tipping load. Just remember -- an ROC of 2,500 pounds on two different loaders, even of the same lift style, doesn't necessarily mean that the two loaders can lift the same load at the same height. J732.5.4 actually is a standard that is identical to 732.5.3 (what I explained above), but 5.4 dictates that the manufacturer state at which height the tipping load occurs. Obviously, no one follows this guideline...

I'm still trying to figure out breakout force. I suspect that a few manufacturers publish the force at which the loader actually lifts the rear off the ground (completely within J732 guidelines, in fact), while others publish hydraulic forces (if their machines are hydraulically limitied). It is allowable to publish the force at which the machine begins to rotate; it is also allowable to publish the maximum force of the cylinders if they cannot rotate the machine. It would seem that certain manufacturers definitely take the "tipping" route while others use hydraulic capacity. Not sure about this one completely.

In any case, hope that helps somewhat... I'm still trying to figure out breakout force.

StoneStacker
02-11-2005, 10:49 AM
Everyone has made some excellent points. I noticed that when I was looking through a CAT 226 OMM that there was a section that covered what the ROC was with different types of buckets. I think this applies to what is being discussed concerning moving/pulling the load further/closer to the CG of the machine. Excellent topic.