Grapple Failure

[IslandTractor]

That is my perspective. I plan on keeping the grapple and reinforcing it if needed, to do the job I bought it for. Welding on some extra steel while everything is straight and true is a much easier prospect than repairing one that is already wrecked. I'd like to see them make an improvement to the product by upgrading to 1/4" steel and/or improving whatever else is causing these failures and thrive in business as a result but it is unreasonable, in my opinion, to demand they redesign the product to replace mine with a new and improved model, if they have not made the improvements already. If Whirlpool comes out to repair or replace a broken dishwasher, it would be unreasonable for me to demand that they redesign the dishwasher before replacing the broken one.

I agree that is a good solution for you if you are willing and able to do the necessary modifications. However IMO, until we learn that Wildkat has actually changed to 1/4" wall top tubing, anyone contemplating a grapple purchase should steer clear unless they 1) have a very light weight machine with limited loader power. Or 2) intend to give it the Lada treatment and put some reinforcement on that top tube before ever using it. As it stands, I wouldn't put one on my old CK20.

 

[ovrszd]

Since the cylinder is the thing that is actually creating the damage here, they should probably "downgrade" that for the 1/8 lite version as well.

That's the fix right there. Build a "cheap" version with 1/8" beam and smaller cylinder so it doesn't destroy itself. Problem solved.

When I'm building something hydraulic I just guess as to cylinder size. But if I was marketing a hydraulic item I'd contact someone like JJ or oldnslo and have them figure a cylinder size for me so my junk didn't destroy itself.

 

[J F]

No question Ralph was and still is an idiot. He gave us Shrub as his last great gift to the nation.

Compared to the current "gift", the "shrub" just keeps looking better and better.

 

[k0ua]

Compared to the current "gift", the "shrub" just keeps looking better and better.

No kidding, I didn't think much of the "shrub" at the time, but I would take him back now in a heartbeat.
I used to think Carter was the worse president we had ever had, but no... not so much any more.

 

[CalG]

That's the fix right there. Build a "cheap" version with 1/8" beam and smaller cylinder so it doesn't destroy itself. Problem solved.

When I'm building something hydraulic I just guess as to cylinder size. But if I was marketing a hydraulic item I'd contact someone like JJ or oldnslo and have them figure a cylinder size for me so my junk didn't destroy itself.

How would one EVER calculate the destructive loading on that top transverse member?

The failure was in the HAZ, a very difficult region to quantify. (What is the shear value within the HAZ?

Sure adding material will do in a "belt and braces" approach, but if a 2 inch cylinder will not work, how can one say a 1.5 inch cylinder will. Or, what value would one set the pressure regulation valve ?.... 2500psi? 2250? ... or start at 1000psi and see how things work out clamping on material wise. tuff call I would say.

Me? I'm using the T-LAR finite element analysis software to qualify all my fabrication efforts!

(T-LAR? = That looks about right!)

 

[TomSeller]

That's the fix right there. Build a "cheap" version with 1/8" beam and smaller cylinder so it doesn't destroy itself. Problem solved.

When I'm building something hydraulic I just guess as to cylinder size. But if I was marketing a hydraulic item I'd contact someone like JJ or oldnslo and have them figure a cylinder size for me so my junk didn't destroy itself.

The damage in the previous thread was not from closing the cylinder. It was from pushing with the lid. Granted you should not push on the lid but a little is unavoidable. They just need to use something besides pop can walled tubing.

 

[Zebrafive]

I know I came to this late.................. Checking online steel prices:

3x3x1/8 wall x 4ft weight 19lbs, cost $30.65 includes $5 cutting fee, no shipping fee

3x3x1/4 wall x 4ft weight 35 1/4lbs, $36.72 includes $5 cutting fee, no shipping fee.

16 1/4 lbs more metal for $6.07 more. Or $1.52 per ft.

Another thing about square tubing, wall thickness can be plus or minus 10%, so your 1/8" wall might only .113"

Source: The Best Place To Buy Metals & Industrial Supplies Online | Buy Metals Online | Buy Industrial Supplies Online | Cut to Size | No Minimum Order | CNC Laser Cutting | CNC Machining

 

[IslandTractor]

I know I came to this late.................. Checking online steel prices:

3x3x1/8 wall x 4ft weight 19lbs, cost $30.65 includes $5 cutting fee, no shipping fee

3x3x1/4 wall x 4ft weight 35 1/4lbs, $36.72 includes $5 cutting fee, no shipping fee.

16 1/4 lbs more metal for $6.07 more. Or $1.52 per ft.

Another thing about square tubing, wall thickness can be plus or minus 10%, so your 1/8" wall might only .113"

Source: The Best Place To Buy Metals & Industrial Supplies Online | Buy Metals Online | Buy Industrial Supplies Online | Cut to Size | No Minimum Order | CNC Laser Cutting | CNC Machining

Yep. Looks like saving $12-15 bucks per grapple is more important to some companies than quality.

 

[Red Horse]

I agree Wildkat is making an effort but replacing a Chevy Corvair with another identically flawed model doesn't make sense.

How do you draw that conclusion?

 

[Red Horse]

The damage in the previous thread was not from closing the cylinder. It was from pushing with the lid. Granted you should not push on the lid but a little is unavoidable. They just need to use something besides pop can walled tubing.

Agree 100%-although there are many whom have posted on this subject that insist its an over application of hydraulics.

Speaking from EXPERIENCE, I wrecked mine by doing something it was not intended to do- I had rolled the top grapple onto the edge of good sized boulder and was trying to drag it out of the ground-using my 60 horses and close to 6000 lbs of weight.

Now while I have been vocal in defending Wildkat-I got what I paid for and IMO you are dreaming if you think you have the right to get Big buck tractor quality (Deere/Kubota?) when you buy a Chinese Nortrac tractor or whatever they are called- I will say in my case thjey dropped then ball and it may well have been just a welder's error. check out attached shot. The cylinder attachment bracket did not have a full weld on it. Regrdless of 1/8th or 1/4" tube, this bracket had no benefit of the front of the tube as it was not attached!!

 

[94BULLITT]

I agree. The first thing I would do is drill a 1/4 inch hole in that top tubing and see how thick it is. If it is still 1/8. then reinforce it to distribute the stress and carry on.

James, look at the cylinder mount on it then compare it to your grapple. The Wildkat looks like a poor design even though it is made out of 3/8''.

 

[k0ua]

James, look at the cylinder mount on it then compare it to your grapple. The Wildkat looks like a poor design even though it is made out of 3/8''.

I did that very thing 2 days ago.. and noted the differences in how the cylinder was mounted.

 

[Coyote machine]

For discussion sake, why not install a crossover valve in the hydraulic cylinder's circuit, set it to where inadvertent clamping down on a load would not create forces large enough to result in damage to the grapple? This would allow use of the current design; though going to 1/4" stock tubing would likely effect the same result, at possibly lower overall cost increase. The best might be to do both, and likely eliminate both self destruction of the 1/8" material AND less potential failure in use with larger weight and HP tractors. End result, happier users, more sales, better reputation, etc.
What say you 'herd' :confused3: ?

 

[TomSeller]

Agree 100%-although there are many whom have posted on this subject that insist its an over application of hydraulics.

In the previous thread (from 2 years ago) referenced in this thread it was mentioned that the cause of failure had to do with pushing with the lid. In this thread the cause of failure had to do with clamping down with the hydraulics if I understand correctly.

 

[ishiboo]

IMO using thin wall tube for that area is not really the problem, but the design itself. There grapple mount should be two plates (1/4?) that are welded to both the top tube and travel down to the bottom tube.

 

[jmc]

Yep. Looks like saving $12-15 bucks per grapple is more important to some companies than quality.

If he did that cost comparison with the steel prices companies pay for a few thousand pounds instead of a few feet, their cost savings would seem even less defendable. Also, some of the steel service centers have price schedules that discount according to ALL the steel you buy annually, not just that few thousand pound order.

 

[bhh]

Because the FELs have a rather small payload capacity on these smaller compact tractors, let's remember there is a real need to NOT over-design them. That is as much a reason why people choose these 48" "economy models" than just saving a couple hundred dollars. That was the case with me personally. I attempted to balance strength with weight but cost is obviously part of the equation or I'd have a titanium grapple or whatever. It's a real balancing act between weight and strength and some companies are going to do a better job than others.

I can actually understand why thinner walled steel may have been used to shave down some weight at some point but if that decision leads to an abnormally high failure rate, then it obviously needs to be corrected. What we don't know though is how many of these units have been sold and how many had/have problems. We have two on this thread but those could be due as much to bad workmanship than to a design flaw and the actual failure rate could be quite low. I'm not saying I believe that is the case but I'm also trying to have a balanced view through all of this.

If 2 out of 100 fail, is that bad? 1 out of 100? 5? Everyone is going to have a different number and I'm sure they could achieve a zero fail rate but what would be the weight penalty we would have to endure as a result? As long as the company stands behind these failures and does right by the customers, a 1-2% failure rate might actually mean that the grapples are designed appropriately for their use. Just a thought.

 

[IslandTractor]

Because the FELs have a rather small payload capacity on these smaller compact tractors, let's remember there is a real need to NOT over-design them. That is as much a reason why people choose these 48" "economy models" than just saving a couple hundred dollars. That was the case with me personally. I attempted to balance strength with weight but cost is obviously part of the equation or I'd have a titanium grapple or whatever. It's a real balancing act between weight and strength and some companies are going to do a better job than others. I can actually understand why thinner walled steel may have been used to shave down some weight at some point but if that decision leads to an abnormally high failure rate, then it obviously needs to be corrected. What we don't know though is how many of these units have been sold and how many had/have problems. We have two on this thread but those could be due as much to bad workmanship than to a design flaw and the actual failure rate could be quite low. I'm not saying I believe that is the case but I'm also trying to have a balanced view through all of this. If 2 out of 100 fail, is that bad? 1 out of 100? 5? Everyone is going to have a different number and I'm sure they could achieve a zero fail rate but what would be the weight penalty we would have to endure as a result? As long as the company stands behind these failures and does right by the customers, a 1-2% failure rate might actually mean that the grapples are designed appropriately for their use. Just a thought.

The proper way to make a lighter grapple is to use high strength steel rather than lower gauge mild steel. That is essentially what EA did with their new light duty grapple. The other consideration, if you intend to stick with lower gauge mild steel tube is to engineer it properly. Not only does Wildkat use 1/8" tube but they also use a higher cylinder tower which puts more leverage force on the base. Putting in some extra support at the predictable stress points would work but increase cost due to additional welding. Yes, some builders will choose the HF strategy and just build it cheaper and cheaper until it breaks, but I for one would like to know that I am buying an HF quality implement. Is that what we should expect from Wildkat?

I don't think any of us know the exact failure rate of these 1/8" top tube grapples. I would guess that all of these 1/8" grapples would fail at the same spot if used aggressively or at the point when a predictable accident puts a bit more stress on that rear cylinder tower. Probably not likely if the tractor is a BX or B size just moving brush piles but for someone with an L size tractor digging and moving stumps and trees etc the safety margin is slim. I don't recall anyone with a 1/4" tube grapple having this same issue despite using this general light duty grapple type on tractors as big as M59s.

 

[blueriver]

Okay .. Was this or was this not the economy model? Did the OP know this when the order was placed?

I'm thinking out loud here .. A choice was made when the order was placed???

 

[murphy1244]

Okay .. Was this or was this not the economy model? Did the OP know this when the order was placed?

I'm thinking out loud here .. A choice was made when the order was placed???

Since everyone here knows about it I don't think they would buy it now. I sure won't.