how does hydraulic self levelling (HSL) work ?

[Renze]

Hi there,

I have just built a loader on my Zetor 5245, mainly to be used with pallet forks and bale grab for big wrapped square bales.
This loader i bought has no self-levelling though it is very useful for the above mentioned tasks. I could also use some extra lifting force as 950 kg on the forks is not enough for me..

Mailleux of France says on their website, that their hydraulic self levelling system adds up to 35% lifting force, for the same size main lifting cylinders.
I have seen the Mailleux loaders with 6 hydraulic cylinders, 2 crowd cylinders, 2 lifting cylinders and 2 extra cylinders for the self levelling.

the Buhler Allied website says that HSL improves lifting capacity by 25%.

Anyways, how do these systems work ? are some lines from crowd and lift cylinders are tee'd into each other, or does it require a special hydraulic valve, like a flow divider ? Do the Allied loaders also use these 2 additional cylinders for the paralel acting ?

Thank you /forums/images/graemlins/wink.gif

 

[hobbyfarm]

</font><font color="blue" class="small">( I have seen the Mailleux loaders with 6 hydraulic cylinders, 2 crowd cylinders, 2 lifting cylinders and 2 extra cylinders for the self levelling.)</font>

Renze,
I looked at the Maileux loaders and I have the idea that the 2 extra self-leveling cylinders are somehow passive and are plumbed to the curl cylinders to provide the self-leveling adjustment as the loader is lifted and lowered.
Just my opinion. /forums/images/graemlins/crazy.gif

 

[Renze]

hobbyfarm, i think the same...

I suppose, because self levelling makes the bucket tilt forward when lifting the main booms, the total lift height (measured at center of gravity of the load) is not as much as on a non self levelling loader. So any type of self levelling loader lifts more with the same cylinder size, than a non self levelling loader, because of that idea.

But how do the HSL systems of Allied and JD work ? they dont have additional cylinders for the parallel acting, i think...

 

[ZJ_HR]

Hey Doc,
You have two possibilities for that purpose.
First is special self leveling valve (like EATON has), and second one is electronic leveling, similar to EHR.

 

[ZJ_HR]

Found similar topic posted before.

 

[Renze]

Thanks a lot, Zvonimir !

I think i know enough... Indeed, it uses a flow divider like i expected.
It only works if you get it built in into the dual spool valve of the loader controls, which means that i have to buy a complete Eaton valve block... which is 300 Euro at least. And it only works when lifting, not when lowering....

The EHR- alike function would also need power beyond hydraulics to divide the flow.. Ans i suppose it wastes hydraulic power also... ???

I suppose i'll just have some more plates and triangles laser cut at the company i work, and go for the mechanical route... Either with top mounted pullrods or down laying pushrods, like Fendt loaders have.

 

[ZJ_HR]

Renze,
I think that easiest way is to have 2 more cylinders for HSL. I think that this way you will add some lifting force. No mech linkage, lower weight, and easier to build.
Just a curious question: do you have hydraulic steering? If not, can you run external pump from there (in front of compressor)?

 

[Renze]

I have decided to build the mechanical linkage.
The 25 to 35% lifting capacity increase is the same for hydraulic as well as mechanical leveling, because the same forces apply. Two rods and 4 triangles are less weight than 2 extra cylinders, and i have access to my boss' laser cutting machine where i can make parts for free and only pay steel. /forums/images/graemlins/wink.gif

But what is the goniometry applied in a paralel linkage system ? The first part (consoles to triangles) is parallel, but the parts where the cylinders are, are not paralel...

I was wondering if anyone knew a calculation rule to get the output of the two sinus-es that apply to pivot points of bucket, the short tipping arm and the cylinder/triangle.... ???

Any mathematicians out there ?

 

[Dieterd]

hobbyfarm, i think the same...

I suppose, because self levelling makes the bucket tilt forward when lifting the main booms, the total lift height (measured at center of gravity of the load) is not as much as on a non self levelling loader. So any type of self levelling loader lifts more with the same cylinder size, than a non self levelling loader, because of that idea.

But how do the HSL systems of Allied and JD work ? they dont have additional cylinders for the parallel acting, i think...