Help me design a hook for mini excavator buckets...

[G60syncro]

Like the title says... I'm currently finishing up our new trenching and ditching bucket lineup for compact to large class excavators. I'll soon be starting the mini excavator series (10000Lbs and smaller) and I'm wondering about the hook we usually weld in the back.

Here's a bucket for 40-45ton machine:
http://img.photobucket.com/albums/v304/G60syncro/Bucket.jpg

As you can see we use an open hook with a closed eye just underneath it. As buckets go smaller we reduce the size of the hook proportionately. I just hit a wall when I started drawing the hook for say, a Cat 307 size machine. Any smaller than that, I end up with a hook that looks totally ridiculous!! So I'm wondering, should I go with an open hook design, or just a closed eye on which you could put a shackle or something if needed. Or one option that crossed my mind is just welding on a regular 3/8 chain hook on there and be done with it.

I'd like your input about that. I'll also ask mini excavator operators in my area what they think about that.

[Grader4me]

My two cents worth...I am not a designer of hooks for buckets by no means, but if I was buying one I would prefer a closed eye type...something that you could hook a shackle into. For a couple of reasons...with just a hook there is a chance when lifting something, and you have to curl your bucket the chain could slip off. I would not just weld a 3/8 chain hook as there is more of a chance of this breaking off or the chain slipping out.
I like your design in the picture..it is to bad that you couldn't make it work for the smaller bucket. Even if you feel it might be an overkill, it would probally be the safest way to go. Just my opinion....

[digger242j]

I agree that the closed eye is the better way to go, for the reasons given. I'd add though, that it should be large enough to slip the grab hook on the end of a chain all the way through. If it's only big enough to put a shackle into, then you need to have a shackle. That's just one more thing to put on and take off, and keep track of, and eventually lose.

By the way, thanks for asking! It's nice to know somebody, in the design phase, is looking for input from the end users. :thumbsup

[Grader4me]

Good point...I was just thinking about a smaller closed eye hook for the smaller bucket, and when lifting just hook on the shackle and take it off when finished.
But you are right...just something else to look after.

[Dozerboy]

X3 with the closed eye the only time I have used an open hook on a hoe is when I did underground. We had a very large rock box with wheels on one end and a loop of cable on the other. I would hook the cable with the hoe to move the rock box, but that was the only hoe we had a hook for so the rest of the time I would just use the teeth. Also IMO anyone doing any lifting with a hoe should use a clevis if anyone it working around the load by having an open hook you give them the option not to use a clevis not wise IMO.

[Wulf]

I expect you've done your homework but I thought that WCB or OSHA have guidelines for use of lifting devices on buckets? I would consult these and other bodies to ensure that you are marketing a safe and legitimate product.

Looks like the following device with a latch would comply?

http://catalog.thecrosbygroup.com/EnglishProdWarn/BH_313WeldHook.pdf#search='excavator%20throat%20la tches'

[Squizzy246B]

I expect you've done your homework but I thought that WCB or OSHA have guidelines for use of lifting devices on buckets? I would consult these and other bodies to ensure that you are marketing a safe and legitimate product.



Exactly...this is why most manufacturer's will not put a lifting point on a hydraulic excavator...because its not a crane.

Anyway, the best place for the hook is not on the bucket where it will get flogged. Here is our solution:

[Grader4me]

I am not sure OHS has a standard for hooks on a bucket. I know there are manufactures specifications on where and how to mount their hooks. Even with the way Squizzy's company(above picture) designed their hook is probally not taken from a OHS specification?
I could be way of base here, but I am sure that a company that designs and installs hooks for excavator buckets has a handle on the current laws (if any) and specifications.
We are changing our hooks that we have on our front and rear buckets as well. It is a design similar to the picture above. Not because of any new law or standard, but because we want the safest hook up possible, as we do use our backhoes for installing culverts etc.
I would be interested in seeing a link to any OHS regulation concerning this, as it would be good information to know.

[Squizzy246B]

Paragraph 5 covers the certification required, basically if you design something to be a lifting point it has to be certified as such.

http://www.worksafebc.com/publications/health_and_safety/bulletins/worksafe/assets/pdf/excavators.pdf

CAT now do not have lifting lugs on their compact excavator buckets primarily due to certification and liability issues.

[Squizzy246B]

This article has some good links and useful information:

http://www.constructionequipment.com/article/CA469435.html

[Squizzy246B]

This a good reference...takes some searching through but it basically spells it all out:

http://www.hse.gov.uk/research/crr_pdf/2002/crr02429.pdf

[Grader4me]

Thanks for the info Squizzy!
So lets get back to the person designing the buckets/hooks. I would hope that your companies design and the way that your hooks are mounted would meet the lift requirements of these particular machines.
One thing you will be sure to learn from us "end users" is, do it right and make it safe.:yup

[G60syncro]

One thing you will be sure to learn from us "end users" is, do it right and make it safe.:yup

Which is exactly the point of my question!! :) Great responses from everyone here. I feel that everybody plays a part in designing something... and it does'nt have to do with wether or not you have a ring on your pinkie. Everything around you was build to answer the same question: what do I need to do?? From there, the engineer's job is only to translate the idea into something feasable.

That being said, our company never got asked by anybody to give certifications or any kind of testing data for the hooks and lifting lugs welded on our attachments. If a client asks us for certification or some sort of safety requirement, I'd go for a Crosby weld-on hook and be done with it. Our welders all have proper qualification so I don't think it would be a problem.

For kicks, I ran simulations on the larger size hooks we curently use. All of them gave similar results... I used the maximum lifting capacity for the corresponding class of excavator as the load applied in the simulation. The example below are images from our largest hook usen on excavators between 65000Lbs to 115000Lbs operating weight. The load applied in this case is 60000Lbs, this is about 5000Lbs more the maximum lifting capacity of a Volvo EC460 with the short arm and lifting close to the machine, parallel to the tracks.

http://img.photobucket.com/albums/v304/G60syncro/Crochet01.jpg
The picture above illustrates what would happen if the sling slipped off the hook and the load came to be applied at the very end of the hook. Areas in blue and green mean that the part could deform but it will spring back to it's original condition once the load is removed. Yellow and red means that the part is stressed beyond the elastic limit. Since these areas are quite small in this case, the hook won't really deform. However, it could fail after repeated cycles due to fatige causing stress cracks in those areas.

http://img.photobucket.com/albums/v304/G60syncro/Crochet02.jpg
This example above shows the hook being used properly, with the sling resing in the bottom of the hook. As you see, the stress zone is diminished and it moved to a less critical area.

http://img.photobucket.com/albums/v304/G60syncro/Crochet03.jpg
In this final example the load is applied in the closed eye, the safest way to use the hook. The stress zone is greatly diminished and better distributed over a wide area.

The distorted shape of these drawings exagerate what happens in reality. Also at these load levels, I'd be more worried about the shovel tipping over rather than the hook snapping off. At that point we would trust in the jugement of the operator to call in a proper crane if he needs 30 tons of stuff moved somewhere!!

Concerning the initial question, I'll look into making a simple closed loop big enough so you can pass an open hook and chain through it. If it proves to be to big and cumbersome I just won't put it on. These hooks are also used in the shop as lifting points when manipulating the buckets in the manufacturing process. That's why we also install a lifting lug somewhere on loader forks or hydraulic hammer bracket caps... They're simply used to move the attachement around.

The hook example above could lift 20000-30000Lbs all day without complaining and the graph would show it being green all over. That's probably what would "feel" right sitting in the machine, especially when you start reaching out and the machine becomes tippy.

I want to thank you all for your comments and feel free to chime in to further the discussuion. Safety is the most important issue in any field of work!!!

[Grader4me]

[QUOTE=Grader4me]
I could be way of base here, but I am sure that a company that designs and installs hooks for excavator buckets has a handle on the current laws (if any) and specifications.


I rest my case:thumbsup