Tiger in the tank
Tigercat 632E tested
now he’s first with the 632E.
Bit of a theme going on here, Kevin? “Yes, he laughs, “I guess I must be their skidder guinea-pig.”
Either that, or he’s quick to spot a successful machine in the making.
Kevin first laid eyes on the 632E when visiting the Tigercat factory in Canada last year, then saw it again at the DEMO Show in British Columbia, which convinced him it was the skidder for his operation.
DK Logging was still running the original 635C, but it was getting up around 16,000 hours and Kevin wasn’t sure a six-wheeler was necessary for where his crew is working on the eastern flanks of Tarawera Forest, off the McKee Road (aka the Million Dollar Highway).
“The reason we went with this machine and not a six-wheeler is we shovel a lot downhill anyway and the six-wheeler it’s probably a bit over the top if you are not getting up on the ridges and that,” says Kevin.
“Thought I’d go with a four, a bit faster. This one’s got the big grapple, the 23-square metre, so not far off the six-wheeler’s 25-square metres, and the 630 has the 19, so this one is a bit more than in-between.
“I was planning on a 630E but when I got to the factory these things were sitting there, so …………
“This one can pull at least a couple of tonnes more. And it does it faster. It will pull a drag that makes the tyres look as though they are flat.”
Each of those Tigercat skidder models is very closely related, as both the 635 and 632 are derived from the 630. The 635 is basically the 630 with an extra axle tacked onto the rear, whilst the 632 uses the same architecture as the 630, but has been pumped up on steroids.
Several components and structural items on the 632E have been upsized for improved durability so that it can cope with the extra workload. Examples are a larger and beefier crane and arch, bigger box sections in the chassis, heavy-duty centre pivot and larger supporting arms for the blade. And, of course, that bigger grapple. All up, the changes add a further 1.865 tonnes to the weight, compared to the 630E.
Walking around his new “beast”, Kevin points out some of his favourite changes, such as the enlarged grille in the arch, which is both deeper and wider, to afford the operator a better view of stems on the ground as he guides the grapple to them. There’s a new light built into the centre of the arch, in addition to two already there, for improved vision in early morning starts (all lights are now LED).
He pats the grapple, which looks a lot bigger up close, happy that he went with this size. Tigercat had the luxury of seeing what Caterpillar and John Deere had done with their grapples before releasing the 632E and they obviously couldn’t resist going for bragging rights by making their one slightly larger. You can get a smaller grapple, but honestly, why would you? This one can swallow 2.14 m2 (23 ft2) of wood, and when fully open, it stretches out to 3,861mm tip-to-tip, so it can be an absolute Gannet. It’s operated by a pair of hefty cylinders and comes with a choice of plate or box tongs – Kevin took the plate option.
At the other end, the blade has also been super-sized, with extra extensions built on either side because the Tigercat team knows Kiwi loggers like their big blades. They also had the good sense to increase the size of the pistons that work the blade.
You need a powerful engine to move a near 22-tonne machine and 16-plus tonnes of wood, and Tigercat has happily obliged.
Tigercat has been progressively replacing the previous Cummings engines across its range of equipment with a line of FPT engines – FPT is part of the Fiat Industrial group. The 6.7-litre six-cylinder FPT N67 engine fitted to the 632E may be smaller in cubic capacity than its direct competitors – 7 litres for the Cat 555D and 9 litres in the John Deere 948L – but it’s the most powerful of the three, with peak output dialled up to 216kW (290hp) @ 2,000rpm, from 195kW (262hp) in the 630E. It’s still a Tier 2 engine like the John Deere’s, so it isn’t as clean as the Cat Tier 4f unit, which may be an important consideration to environmentally-conscious contractors.
Peak power is only one aspect of performance measure, however. It would be nice to know what the torque output is, but no figures are given. I’m guessing that it will be closer to the Cat’s 992Nm, rather than the John Deere’s 1,276Nm, given the size of the engine.
Whatever the torque figure is, Tigercat seems to have wrangled every Newton metre from the N67 to ram through the EHS drive system, because the performance is something else.
EHS, or Efficient High Speed, might best be described as a hyper-active hydrostatic drive system. Tigercat has used standard hydrostatic drive for more than 20 years and the EHS similarly consists of two variable displacement motors as inputs to the Tigercat transfer case, with front and rear output shafts connected directly to the front and rear axles.
While the standard electronically controlled hydrostatic drive system performs exceptionally well, EHS allows it to do more, thanks to a bit of extra technology.
This is accomplished with more sophisticated computer logic and the ability to take one of the drive motors offline when high tractive effort is not required — for instance, when traveling empty or loaded on flat terrain. In this case, all pump flow is directed to one hydraulic motor, increasing both travel speed and motor efficiency.
When operating conditions demand high tractive effort, such as pulling a heavy drag, both hydrostatic motors are working. Complicated? Maybe. Effective? Yes.
With so much power directed to the ground, it’s important the driveline components are able to withstand the additional forces
The new OB20 rear axle – specially designed for the 632E and the biggest sized axle in any skidder — provides 47% more torque capacity and nearly twice the life on all bearings. The service brakes and park brake are incorporated into the new axle.
The axle mounting has been redesigned to use four high-strength 30mm bolts and two 30mm studs on each side, mounted to a massive 77mm thick steel frame. The new design transfers the force to the skidder chassis and can better handle the higher torque load of the new axle and uprated EHS drive. Rear drive shafts have been increased in size to 8.5C from 7C.
As mentioned at the very start of this article, we couldn’t help but be impressed with how the 632E gets into its work. Charging around the skid site like a machine half its size, then belting back up to the cut-over at a surprising speed, considering it was travelling uphill. Re-appearing a couple of minutes later with a heavy drag behind, yet still running like an express train. Easily faster than any forwarder we’ve seen, which are supposed to be the race horses of wood transporting in the forest.
Regular operator Rick Royal reckons he can pull as much wood as the old 635C he was driving before jumping into this machine. I recall that when we tested that 635C in 2008, in another part of Tarawera Forest, it was dragging as much as 20 tonnes on occasions.
Rick says the 632E is capable of pulling that much, but he doesn’t feel it’s necessary to put it under so much strain. Pulling lighter loads (around 16 tonnes) at higher speed delivers faster turnarounds, meaning he can still hit the 750-tonne daily average.
“That’s a big grapple and I’ve had six real big stems in there, some would have been around three or four tonnes each, but you don’t want to be pulling that much all the time,” Rick adds.
“Compared to a 630D the drags are bigger and a lot quicker – it probably takes two extra stems per drag and it does that easily.”
He’s driven a few Tigercat skidders in almost ten years with DK Logging, including the first 630D, which is a good reference point for the 632E.
“This one has more power than the 630D,” says Rick. “Lot more weight, it doesn’t come off the ground very easy. I like that.
“The 635 is pretty weighty too, that was good. The six wheels make a big difference on wet ground but I’m surprised with the traction on this one – we haven’t needed to think about chains yet.
“It’s better on the fuel than the 635. That had a smaller tank and
we filled it every day. I’m filling up the 632E every one-and-a-half days and it still has a third of a tank left. Pretty good when you consider this tank is 430 litres – less than the 630D, which has a 500 litre tank, I think. The tank has been reduced in this one so you can see better down over the arch.”
Rick says the ride in the 632E is comparable to, or slightly better than the 630D, but not as smooth as the six-wheeled 635. It does, however, make up for it with improved manoeuvrability over the six-wheeler.
For Rick, some of the biggest improvements are in the cab. The architecture hasn’t changed – it still uses the same cab structure as before – but key improvements have been made for comfort and driveability.
Top of the list of improvements is the new air-ride TurnAround seat, according to Rick.
“It’s real good, much better than I was used to in the 635, which wasn’t even TurnAround,” he says. “Compared to the 630D it’s better. Very comfortable and has lots of adjustments you can make to it. Has the 4-point harness, too.
“The ignition has been moved to over by the rear-side window. Used to be under the dash. Sometimes I go to reach under the dash and it’s not there. I’ll get used to it.”
Steering is now through joystick controls, compared to the wheel on the 635 Rick came off, although he did have joysticks on the 630D prior to going onto the six-wheeler.
A new instrument panel layout improves placement of electrical outlets and the electronic control system display.
Compared to his previous experience with the 630D, Rick has noticed some differences in the speed controls, saying: “On the lefthand joystick, where you’ve got forward and reverse – in the old one, you could just slide it and it would stay in position on the track. This one, you just flick it and it will go down.
“It starts off at about 5 and then goes to 10, 15, 20, 30, 40, 50, 60, 80 up to 100. That’s percentage not km/h. But, boy, this machine can move. If you got a good bunch of pulp in it you could shift it to 100 (percent) to go down the road and it would really go. I’ve pulled good drags at 80 (percent).
“There is an extra button on the joystick trigger, that’s to make the machine drive instead of using the pedals. If you are going down the road you just pull the trigger and away you go – so you can give your foot a rest. It’s quite touchy. It doesn’t take much to adjust the speed.”
Since Rick swapped into the 632E from the old six-wheeler, his colleagues have noticed the difference.
“It’s got a fast turnaround, that’s what the harvester operators reckon,” he says. “They say it’s that fast they can’t keep up. Lot faster than the six-wheeler.”
Rick likes the fact that the 632E is equally fast when driving in reverse, adding: “The good thing is you don’t have to turnaround when you’ve dropped the stems at the skid, you can just keep going grapple first. Saves a bit of time.”
With the additional visibility through the arch, Rick says he doesn’t have any problems seeing the track ahead when reversing back to the cut-over. And the extra depth in the grille makes a big difference when he’s manoeuvring to grab stems.
“I can see a lot better through that new grille, it means I can get closer to the stems and still see,” he says.
“The longer boom makes it easier to reach, too.”
That extra length in the boom allows Rick to raise the butt ends higher, so there’s less of the trees being dragged on the ground – another reason why this machine is so quick.
And yet, in spite of the additional bulk of the boom and the grapple they are also just as fast to work as the rest of the machine.
“The hydraulics are probably five times faster than before,” chips in Kevin.
There’s a reason for that. The hydraulic system has undergone some big changes, the most important of these being a move to load-sensing, along with a larger main hydraulic pump and valves, allowing for better multifunctioning. The larger hydraulic cylinders enable the machine to run pressures that are 10% lower while
This aspect impressed our Iron Tester, Stan Barlow, when he got behind the controls, and you can read his comments on page 34.
Before we let Stan loose on the Tigercat, we ask Rick whether the move from HID lighting to the new LED lamps (there’s 11 of them) has been a positive one for those early morning starts.
“They’re pretty good, nice and bright on dark mornings, pretty much the same brightness as the HIDs in the old skidder,” he says. “They don’t suck as much power, so that’s good.
“The new position of the lights on the boom – they’ve moved right to the front – and that new light in the middle, has made a big difference. Lights the grapple up nicely in the dark.”
We leave Rick to give Stan some pointers on the controls of the 632E, in preparation for his Iron Test, while Kevin and myself chat about harvesting in this part of Tarawera Forest.
DK Logging has been working in Tarawera for a while, so Kevin and the crew are well versed in the terrain and varied ground conditions. Even though this is largely ground base country, some of the hills can be very challenging to pull wood from, Kevin says. And the ground conditions vary wildly within the forest, from free-draining pumice to pockets of boggy clay.
I mention to Kevin that Stan and I encountered some of that sticky stuff when we took a wrong turn and ended up at their previous skid site, just around the corner.
“The ground conditions were really bad in there,” nods Kevin, “but this skidder was pulling the wood alright. We haven’t needed to put chains on it yet, seems to be getting through without them. We’ll see how it goes when we get some more rain (note: more rain did arrive, but not enough to require chains).”
Keeping those 35.5 x 32 tyres off chains for as long as possible will help to prolong their life, too.
To be fair, this new block, where they started a few days earlier, does look nicer than the one we stumbled into and it doesn’t have any standing water. That’s been very helpful in enabling the new Tigercat keep up its speedy work rate.
We’re now about to see whether Stan can match the pace of Rick behind the controls of the 632E, as he’s set off for the cut-over to grab his first stems.
Stan has wide experience on skidders, but confided earlier that this is the first modern Tigercat he’s driven with a TurnAround seat and among the few he has steered through joystick controls. Having watched how well Rich performed, Stan was anxious that he didn’t let the side down.
Maybe that’s why he reappeared on the skid a short time later with a grapple bulging with wood, as he tried to emulate Rick, dropping a couple of stems while turning towards the stack. He later admitted he should have been less greedy with his first load.
It took Stan a little while to find his rhythm, partly because the steering joystick on this machine was in the opposite hand to the Komatsu forwarder we had been testing earlier in the day in the adjoining Kaingaroa Forest.
But the 632E is a relatively simple machine to understand and Stan soon got the hang of it and was enjoying the same speedy travel and implement operation that we’d witnessed with Rick at the helm when we first arrived.
Rick has now joined our group, as we watch Stan doze the stems in towards the stack, and I ask whether he likes the big blade and how much use it gets, and he says: “It’s wider than what I had before, very useful on the skid. I do use it a fair bit, scraping the surface and cleaning it up.”
The extension has added another 700mm to the overall width of the blade, which is now almost three metres, not far off the size of the blade on the John Deere.
“We didn’t expect it to be that wide when it turned up like that from the factory, but we’re not complaining – it saved us doing it here,” adds Kevin, as Stan arrives with his final load to complete this Iron Test.
It appears to have been a speedy and seamless transfer from the Big Six to the Big Four for the DK Logging team and Kevin agrees: “So far, so good.”
Maybe that should have been: “So fast, so good”.
Longer boom and revised arch can lift the stems higher off the ground.
Facing page top left: Hills are no match for the power of the Tigercat 832E.
Facing page top right: The DK Logging 632E runs standard wheels and tyres, yet it hasn’t required chains this wet winter.
Facing bottom: Keeping those stems high off the ground is one of the secrets to faster drags.
Right: Regular operator, Rick Royal, could carry more stems in that big grapple, but doesn’t want to overload the skidder.
Above left: New LED lighting around the top of the cab, and in the arch, improves visibility on dark early morning starts.
Above right: The DK Logging team pose with the new Tigercat 632E the day it was delivered.
Bottom: New instrument panel layout, re-positioned start button and an upgraded air-suspension seat are the biggest changes in the cab.