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Komatsu PC290-11

Shimmy1

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Anyone have any seat time in one of these? Seems they are kind of a niche machine? The old tried and true 300 had long suffered from the model creep and -8s are pretty much 80k pounds, so the 300 became the 360 and now we have a 290. Supposedly, they are a 300 undercarriage, 200 carbody, 240 boom/stick and 300 counterweight. So, pretty much a 240 on steroids. I'm seriously considering purchasing a 2019 and am looking for some opinions on them, most of you know I do mainly land clearing and drainage, so it would be getting challenged on a daily basis. None of that easy, cushy pipeline or basement digging, lol.

I have always been a Case guy, but I can't find a decent 300 (Case or LB) that I'm willing to take a chance on, and the price is right on this one. Plus, I'm hoping that the 300 undercarriage might come in handy on some of the slopes I need to work on.
 

John C.

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Komatsu has been doing that since I worked on the line back in the eighties. PC360-5 was a PC300 upper with a PC400 carbody. At any rate the only issue was the slewing bearings didn't last as long because they used the smaller bearing to fit the carbody. It was never a problem on the construction machines. It was a little bit of an issue in the loggers because the bearings started failing at around 5,000 hours. 40 and 45 foot fronts with 60" grapples and shovel loggers that continually pulled and punched stumps was something that the engineers never knew about designing machines for.
 

Shimmy1

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After reading John's post, I realize I didn't refer to things properly. This PC290 is a 300 carbody, with a 200 upper, 300 counterweight, and a beefed up 240 front. The salesman called me yesterday and said that he had cleared the purchase with his equipment manager and that they would be getting it through the shop and ready to deliver.

So, I guess I'll be finding out if a 35 ton excavator is going to be the answer moving forward. Here are a few pics the salesman sent me.Shipping_GES BISMARCK TO SHANCO_E00061806_47613_8 (12).jpg Shipping_GES BISMARCK TO SHANCO_E00061806_47613_8 (13).jpg Shipping_GES BISMARCK TO SHANCO_E00061806_47613_8 (22).jpg
 

John C.

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Nice welding but we never welded around the corners. The welds always went straight off the ends in a whale tail to prevent stress risers and cracking.
 

southernman13

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I thought that welding practice pertained more to the plate welded to the boom. That’s where I’ve been told to whale tail it out to keep the boom plate from cracking.
 

John C.

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I've seen cracks propagate from the corner of a boss, go through the mount plate and then through the weld on the mount plate and into the stick. We also stopped doing the chevron ends on the mount plates and made an inverse pattern or an H looking bracket to stop the beer canning in the middle of the stick. Highline Portafab as I recall started that design back in the nineties.
 
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Shimmy1

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We debated over chevron or inverted ends, decided on an extended length on the plate in the hope that it would spread the load out further. I looked at a lot of different cylinder mounting pads, and most have Chevron towards the top, and an invert on the bottom, including the factory-designed mount for this Solesbee, which I didn't get with the thumb. I figured there would be some debate lol.
 

John C.

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In truth I think the biggest issue with how the welds last has as much to do with the operation and the operator as anything. The machines with cracks usually were high hour sloppy jointed and lots of bent sheet metal. Lots of clearing and grubbing stumps with stacking piles or loading grinders.
 

coalrulz

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Good Question
Shimmy1, what pressure are you going to run on the thumb circuit?
 

Shimmy1

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Shimmy1, what pressure are you going to run on the thumb circuit?
I'm not sure if I can set it as easily as I can on the Case, but however it gets set I will have it set a few hundred psi higher than what the bucket will push the thumb back with nothing in it's grasp. That way under normal circumstances the thumb won't be giving way every time I grab something, but if it needs to, it can. That's the way I've ran the thumb on our 210 for 8 years, and haven't had any catastrophic failures related to overpressure on the cylinder.
 

John C.

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We always set them at 2,500 PSI. The bucket is supposed to push the thumb back easily to the point that the cylinder lines up directly through the attaching link. It used to be that the circuit reliefs had to be purchased separate and installed, then pressure reduced to your setting.
 

Shimmy1

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Well, criticize away guys. We had to fabricate a holder for the main pin since this thumb originally was intended for just a bucket. That is 1/2" wall, 3" tubing.2022-07-05 23.42.28.jpg 2022-07-05 23.42.47.jpg 2022-07-05 23.43.21.jpg
 
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