I have several lifting machines in my fleet... including, but not limited to:
Hyster H50H forklift, 7x16 drive and slightly smaller steer pneumatic tires, Monotrol foot direction/throttle, 192 Ford four, 12ft lift mast, 6500lb machine.
Clark IT-60 rough-terrain forklift, 'Super-Single' drive and 30" diam x 10 wide pneumatic steers, 225 slant six, multistage collapsing-cylinder, 32ft lift, about 18,000lbs
IH4130 skid steer, repowered with Kubota 3-cyl diesel
Kubota BX1800 with front end loader, removable forks
Allis-Chalmers D17 (series 1) with a 3-point attachment with forks (no mast, just 3-point).
Each one has it's advantages and disadvantages.
The H50H will go anywhere that there's flat, solid, well-packed, or deep-frozen gravel... or concrete. IF it isn't perfectly flat, solid, well packed, or deep-frozen, you'll be pulling it out with the Allis. It'll work in a tight spot, and lift nicely, and with an overhanging boom, it makes a fairly nice crane, but don't expect it to turn tight on anything other than solid, level concrete. If you have a load on it, and turn on gravel, the inner tire will dig in immediately, and if your load happens to be over about knee high, the machine will destabilize FAST.
The IT-60 will go over MOST of the gravel, and SOME soft surfaces. the Super Singles are wide, but not nearly as tall as a tractor tire, so they'll float, but with it's mast, the 60 is a heavy pig. If you try to turn in anything more than very gradual, it'll dig a drive tire straight down, just like the Hyster... even without a load. The 60 has a wide footprint, which is fortunate- the mast is VERY heavy, so it needs the wide to survive a lean. Keep in mind, this machine was designed for the mast to lay back against the cage, and the shaft-mount forks flip up and lock into holders on the mast, with a pintle-hitch tow-bar attached to the counterweight, surge-brakes on the coupler so it can be flat-towed down the highway. The steer axle has springs, and the truck has a 4-speed Clark transmission along with it's shuttle shift box (torque converter), it has a fair ability to climb, and in 4th gear, it'll hustle down a road at 25mph... but it's very uncomfortable, as the steering is vane-pump hydraulic, and rather vague.
The IH 4130 is basically a Hydra-Mac, it was originally a 2cyl Onan, I repowered with a Kubota 800ish CC three-cyl diesel. It has a ROPS, and I've got both forks and a bucket. As for maneuverability and load, it's a small skid-steer, it'll go fairly tight places, but it's 25hp, and only about 2600lbs, and small footprint, on 15x8 snow tires- it's not a tracked skid-steer weighing 12000lbs and a 90hp diesel... it might be good for 800lbs or so... right at the face of the mast... anything past that, if you back up, you plant your face. It won't work on hillsides in ANY direction, and as others have noted, if you're gonna use it as a lifting machine, you can't do it alone, you need a ground-man. Visibility is very restrictive, you can't get out if there's something wrong, and because it's a balance-critical machine, it is VERY limited reach, and will NOT tolerate an overhanging load. It WILL get into places, and it will push and pull things, and wedge the bucket under, and get a wood block under the back of the bucket, it will lever up some amazing loads... but it cannot carry or handle them. Picking up a fully-dressed small block, no problem... lifting and placing it in the back of a pickup can get hairy. As long as a load is low, it does okay... just don't sink it into soft ground. A larger machine, with more significant tires, or tracks, and more weight, lower CG, would do much better, but at much higher cost, and much larger footprint.
Now, the Kubota BX1800. This is an 18hp 3cyl diesel with live hydraulics and a front end loader. It happens to also have a 3-point hitch, it's 4wd. I have a detatchable weight box, and iron weights on each rear wheel... but no fluid in the rears. Front tires are filled with tire foam. I can pop the bucket off and put on a pair of light forks, but most of the time, I'm using chains to hooks on the bucket. These tractors tend to be rather weak in the hydraulic department, I have to crank it up to full snot to get significant lift, it'll pick several hundred pounds, and because of it's size and geometry, it will maneuver into places that many other things just cannot go... it'll also chain up and pull from both ends, and it'll do it really well... but the BX series has some driveline weaknesses that people need to be careful of, one of them is to NOT use the differential lock (just take the pedal off, so nobody does). The other is to only put it in 4wd when you NEED to, otherwise you'll be carrying some load, and be totally unaware that the rear tires aren't on the ground. Not a carrying brute, but a very handy and capable tool when the need suits.
The Allis D17 is an agricultural utility tractor in the 60hp range, they were built from '57 to mid '60's, mine is the earliest version... the first three series were NOT available with any sort of 3-point hitch, because the 3ph was under a heavily enforced patent held by Harry Ferguson. After that patent expired, the 3ph became a standard thing for most manufacturers. My D17 had a factory 2-point lifting system, as most others did... I added bracketry, arms, and links to give it my own version of a 3-point, and it'll accept any Category 2 implement. I made a face to fit Category 2, that accepts a standard style of forklift forks, and I fitted a pair of 48"ers to it. The face and forks weigh about 200lbs, and the Allis's lift system will hoist this setup, and still have about 3000lbs of lifting capacity AFTER. The nose of the tractor gets light after about 2600lbs, so I add weights to the nose. Original tires for the D17 were 13.6-28's on adjustable spinout wheels, I replaced my worn out originals with a pair of 18.4-26's on solid wheels from a combine... wider footprint, slightly larger diameter, and low price. No fluid in any of the tires, the tractor weighs around 3800lbs. It has 4 transmission speeds and a high-neutral-low range operator. 4th and high, at full governed speed will get you about 12mph, but in 1st and low, at idle, it will inch it's way up OR down an incline with no drama. With split brakes, it will pivot on one wheel when you need to turn tighter, and it'll steer with brakes when the nose is too light. While it isn't the ULTIMATE in forklifting, it has the ability to maneuver through, over, under, and around things that a conventional forklift cannot, it can cross over soft ground that the skidsteer cannot, and it can lift and carry things that would otherwise be unreachable by anything other than a crane or telehandler. The primary advantage, is that the tractor doesn't have a mast, so it isn't vexed with the high center of gravity of a forklift, doesn't suffer the added weight, and consequently, doesn't need the ground surface pressure. With it's large-diameter tires, it can carry a significant load weight over soft surface, and not be at peril of getting stuck or sinking and tipping. The down-side, is that the tractor cannot lift high... but it is able to lift up a 3000lb pallet of bricks and set it on my trailer... It'll lift IBC totes full of debris or firewood, and if I need to go higher, I just tote them around to the driveway, and pull out the H50H.
The all-terrain forklifts that 'look' like they're based on tractors, is somewhat of a misnomer. While they have that layout, identifying them as such, is like calling a Case 580D a 'farm tractor with a backhoe attachment'... it's about the farthest thing from it. One can BUILD an AT forklift by reversing a tractor, and that's part of what factory builds did for those machines, but they thoroughly revisited every aspect of the machine to transform it into an AT forklift. Even REGULAR forklifts came from redesign of a common truck, so qualifying a design from any point in history is irrelevant.
Every machine has it's good and bad points... a telehandler would cover many, but not all... but the pricetag is out of my 'allowed domestic budget'. The least costly, and save for one aspect, most effective, has been the D17 with 3-point forks. In all the cases when it couldn't accomplish either the load weight, or the lifting height, it was able to do one thing that NO other machine could:
Drag a stuck forklift out of a hole, back onto solid surface.
