cylinder safety stops for *bucket* cylinders

[Sportsman762]

@Smokeydog I could not remember who made a platform with legs. That is some nice work you did!

 

[orangetree]

My mechanics-of-materials is screaming BUCKLING BUCKLING! Just giving you a hard time. A great safety feature.

But since we're talking safety - I can't not add here don't rely on that for anything beyond a true backup. While you didn't state tube specs, it's likely a fine safety factor in compression only - but it's buckling that'd be the failure mode for sure, and this could develop very quickly. Also any torque on the structure would exacerbate it.

I point out the above because my FEL sags quickly enough (an inch per hour maybe?) that it would load the "safety" structure. Granted you'd still have to have a hydraulic failure to experience a full fall; but again we're talking redundant systems here and if the FEL were to relax onto to posts, followed by post buckling, you could see several inches of ~free fall. Plenty to send you toppling if it happens at a sub-optimal moment.

 

[Too many Kubotas]

If those legs would be able to buckle, the set bolts would've seriously deformed them first.

 

[orangetree]

If those legs would be able to buckle, the set bolts would've seriously deformed them first.

You're correct that any deformation caused by the bolts will dramatically decrease a tube's resistance to buckling (see: a dented pop can). But less so about the tube's behavior in buckling overall.

I'm replying because we're discussing implementing safety features. The actual mechanics of buckling stress are not necessarily intuitive if you've never had to calculate them. Perhaps even then, lol. They are MUCH lower than you'd expect.

If you want to learn more there are tons of better teachers online than I - but I'll just offer one contrived example. Have someone push down on a vertical tent pole. Easy to buckle. Now see how much lateral support is required to prevent them from buckling it. Very low, comparatively. lateral support, even though very small compared to the axial load, makes an outsized difference in buckling of something "high aspect ratio".

 

[Smokeydog]

Not sure of your platform design or lateral loading but maybe you shouldn’t be using a tractor loader? There are many alternatives. The safety legs don’t have to support much lateral load as the loader and tractor are there even with loss of hydraulic pressure. Even if they buckled they would slow descent in catastrophic failure. How they might fail was considered in the design. Survivable? Hope I never find out. 12’ fall I would much rather be in man basket than on a ladder. Don’t bounce as well as I used to.

 

[Too many Kubotas]

Okay, took a quick look at the loader on the M6040 and there are five (per side) places where it'd be easy to run a strap to keep the bucket from curling out.

Only counted places that have favorable geometry. Simplest would be a single strap going around the center of the tube between the loader arms.

 

[scootr]

I made a pair for the MX. Just welded 2 pieces of 2" angle to make a U shape that fits over the bare piston part of the cylinder and fastens in place with a clevis pin.

 

[oldnslo]

Install counterbalance valves hard plumbed directly to the cylinders. This is what is used on boom lifts. Works in all cylinder positions and requires no manual adjustment of locks or supports.

I believe must be set around 25% higher than system pressure to meet safety standard but not positive on than percentage.

 

[orangetree]

I made a pair for the MX. Just welded 2 pieces of 2" angle to make a U shape that fits over the bare piston part of the cylinder and fastens in place with a clevis pin.

As in the OP, I'm talking about the bucket cylinders not the main/arm cylinders. I am already using a block for the arm cylinders.

 

[orangetree]

Install counterbalance valves hard plumbed directly to the cylinders. This is what is used on boom lifts. Works in all cylinder positions and requires no manual adjustment of locks or supports.

I believe must be set around 25% higher than system pressure to meet safety standard but not positive on than percentage.

Thanks. It's looking like these, or some sort of chain attachment, are my options. IDK - I'm sure you're correct about the counterbalance being used in safety situations, but I don't design this sort of equipment / am no hydraulic expert, presently I'd feel a LOT better about something purely mechanical I will do some more research, though.