Counter weight increase

I am thinking of adding some counter weight to my Komatsu PC75uu2.
Reasoning, factory bucket set up is designed around 990 lbs. payload (.33 cubic yds)
Mine has a thumb and amulet quick connector. Adding around 250 lbs for both.
As well I have a 36 in dig bucket that has a .55 cubic yd capacity which when calculated at the same rate means a potential of an
Additional 660 lb payload.
I have lifted and moved a 2085 lb weighed bundle of steel at full extension from the ground level from the bucket teeth. She gets a little light in the tail but I could still move to where I needed to bring the load in closer.
Thinking of adding the equivalent of the thumb n quick connector.
Aprox 250 lbs.
Any thoughts on this and have any of you done this?
Thanks!

Sounds good to me. The hydraulics should stall before damage occurs I would think.

Good day Batkom
The excavator is at its most unstable working across carriage with full reach, adding counterweight often will stress the machine components.
Many users have also increased the size of the track groups to increase stability with limited success. We are aware of one customer in the Netherlands whom installed an additional fuel tank between the weight and superstructure there by aiding stability.
May food for thought.
Kind regards
uffex

Uffex:
Yes I do realize that it's adding weight and therefore stress.
However, Komatsu offered this model machines with an extenda hoe sliding stick option and these came with a very large counter weight added.
So I am thinking that adding 300 lbs would not be a real big deal stress wise and will actually increase stability with the extra weight I already have added to the work end of the machine.
As well I feel a balanced load on the swing bearing would be better than a load thats all on one side all the time.
Just my feeble thinking!
Ordered the steel today to build it, should be about 340 lbs.
If it all imlploads this year as I use it I will ppst it!
lOl

340lbs won't make an appreciable difference to the wear life of the machine, IMO. That being said with the assumption that you're not radically increasing the tail swing of the machine.

I've added counterweight to a few machines. It is a simple formula you get by measuring the distance from the center of the house to the end of the bucket and then doing the same to the center of the counterweight. What you are doing is figuring the ratio. You use the ratio you came up with and use the known weight out front and the known amount of counterweight installed to check your ratio. Let's say your ratio is six to one in length, that would assume the counterweight is six times heavier than the load you can pick. So take your 2085 lift and assume the six to one ratio in this example and you should have approximately 12,510 pounds of counterweight. If that is what your spec sheet shows for the stock weight you can now use the ratio to figure how much you have to add to get your 660 additional pounds of lift. In this example you are looking at an additional 3,960 pounds of weight on the back of the machine.

Adding counterweight when done correctly only adds stress into the swing machinery turning the house. It doesn't mean much of anything as long as the ratio keeps the load center inside the slewing bearing.

John
Thanks very much, that's exactly the info I was hoping to find, makes perfect sense.
I will measure it up tonight n see how much I should be adding to achieve the goal of balance the extra weight.

We had a guy back at home who built logging roads. They like to put in pretty narrow temporary roads around our area, and all in very mountainous terrain. Anyhow, he added more weight to his counterweight by cutting open the plate on the top of the counterweight, and having a concrete coring company bore a number of holes vertically through the concrete inside. He then filled the holes with lead and welded the plate back on the top. When he was done, you couldn’t even tell he had ever touched it, until you were in the seat lifting something heavy.

So looked up my counterweight - it is 2200 lbs according to the manual. I feel like they engineered this weight at a 2.2 ratio - based on there calculated standard bucket load of 990 lbs.
So I believe I need to add around 550 lbs to counter the added weight of my thumb and bucket quick connector.
Trying to keep it tight n neat as its current zero swing, my first 340 lbs will bring it 1 in past the zero swing.
So looking at adding the remainder underneath. Have lots of clearance to the tracks so think I can put one inch there.
Amazing how much steel it takes!

Alco
That sounds like a good idea- but I think my counter weight is cast iron.
That would make a really clean set up though!

The weight of the counterweight doesn’t factor in to rebalancing the machine... think of it as a see-saw with the turn table being the pivot.

If the CoG (center of gravity) of what you you added to the boom is 18’ from the center of rotation, and the CoG of where you can add the weight behind the centerline of rotation (center of swing bearing) is 3’, you need to add more 18’/3’=6x the weight added to the boom to restore the factory balance of the machine in that configuration.

If you bring the boom in that moves the weight closer=the balance (CoG) of the machine moves towards the counterweight. In our above scenario going from 18’ to 12’ means you’d only need 12’/3’= 4x the weight to maintain factory balance.

I'm just going to throw this out there. If you're working on slopes at all, I would be careful on how you operate with added counterweight. I've personally set up several mini's (and some full size excavators) that have rolled over backwards on slopes. The local rental house has my #, its usually inexperienced operators (but not always), trying to clear out their back yard/ put in a retaining wall. There's a lot more that I never see, they just pull it over with whatever else is on site.

When they go, they typically have their digging side/stick up hill, or just swing that way to move. (usually back in the trees) Then they boom and stick in all the way/up. Then they try to swing back to the downhill, and they go over backwards/sideways. It's a leverage game. The ones I've set up are all factory machines, and added counterweight would make it even worse.

I'm not implying that your not a experienced operator, I just wanted to point out a potential issue in the right conditions. I face the same issue with my one rough terrain crane. A year or so ago, I had to get inbetween some trees with a slope, so traveling with the boom telescoped in all the way, but boomed up. When I came out of the spot, it got light on the front, the machine trying to roll over backwards. My rigger said he saw a lot of daylight under my left front tire. Its a 66,000lbs machine, and I don't have a bucket I can put down to steady myself, and traveling with the house locked, I couldn't swing the boom uphill and down. I got out of the slope ok, but it was touch and go for a little bit.

If you're in flat conditions all the time, it should never be a problem, I just thought I'd mention it. When you're heavy on the bucket side, and you start to go, you can just put the bucket down, when you're heavy on the back side, you're going over, and you're just along for the ride.

I have had several machines and all of them have had a coupler, thumb, and as big as a bucket it could handle, I've never added extra counterweight or felt I had to, I just learned the limits of the machine when it was equipped with those attachments. Also keep in mind that you can add as much counterweight as you'd like but you'll still be limited of the weight you can pick up by the reliefs protecting your hydraulic system. If you are mainly just going to be doing something like setting a certain size/weight of retaining blocks or whatever, then it may be worth it, but you'll still be limited by the hydraulics...

Lumberjack, understood, so actual c/l of bucket pin to c/l of swing on this machine 17.5 ft, and c/l of swing to the outside of the counterweight where I am adding the weight - 3ft 10 in. Ratio 4.56. That ends up being a lot of extra weight - think I will stick to Adding around 500 lbs and see how it feels.

Crane operator - thanks for the words of caution! Mostly flat ground - but there's always that little gotcha spot that can still get you. In the last 10 years of having my hitachi ex50 then the JD 60G I only have about 1000hrs experience. I came close to tipping the 60G over. Placing 3500 lb eco blocks on recently graded non compacted ground, soft spot, one side starting sinking and the block was 6 ft in the air as I was swinging it very carefully on top of a wall of these. I got the block down quick enough, but she was touch n go for a few seconds!

Tags, this is my third mini/midi. Also have had thumbs n quick connection on the other two, but being they were Hitatci n JD factory installed always assumed they designed all that in mind. Had a 30 in dig bucket on the 50(10,000lb) machine, I did fine with it- but I always treated it with respect- cause it was definitely on the edge of comfort at times. Was tempted to add counterweight to it but never got around to doing it.

The 60G I had a 42 inch non toothed bucket, in between a dig bucket and cleanout bucket in shape - held a good scoop of dirt -this I also had to be a bit careful with as it was a good load when heaping full.
I am in the middle of going thru the Komatsu so figured while It's in the shop nice n warm I should add them and give the extra counterweights a try.
Thanks everyone for the input on this, the rearward instabilities may not have entered my head till crap hit the fan!

Here is a picture with the added counter weight installed.
Used 3in x 1 1/4 steel bar, total of 340 lbs.
4 bolts holding it onto the original, each piece welded to the other.
So its removalable either as a unit by itself or can be left on and the whole counter weight removed.
Still close to zero turn. Does it make a difference?
Don't know, I did not run the machine long enough before I started going thru it.
I will say though that it feels pretty solid with a full .55 yd bucket at full extension.
Machines original bucket size is .33 yds.
Been working on restoring it 2.5 months solid, every evening and most Saturdays!

Is your right track on backwards?
Bob

Beautiful machine, Batkom!

Great eye, Bluox!

Bluox
Would not surprise me!
I know the guy I bought it from put those tracks on there. There were so many backwards and screwed up stuff on this thing nothing surprises me at this point!
I will go and look it over. First steel track machine I have had, the other two were rubber track, never occurred to me to look for something like that!

Bluox said:

Is your right track on backwards?
Bob

Click to expand...

Good catch. . . . I'm sure he will appreciate it. I personally never noticed myself as I was looking at the weights.

Ok, checked it out when I got home, and yes indeed one track is on the opposite as the other!
So please verify which one is correct.
And what is the proper way to take it off? If it involves taking the track apart, whats the proper procedure?