NewLight
Bronze Member
That looks incredibly handy. What safeguards dose it have against hydraulic failure?
work platform on truss boom
- Thread starter Renze
- Start date
- Views: 15382
Rock knocker
Veteran Member
None?
jerrybob
Elite Member
The ground!:laughing:
The problem is getting the thing upright. With bad piston seals and a 42 year old pump it takes more tilt force than the bucket cylinders can provide, so i use the loader lift cylinders to push it to the ground in order to use another fulcrum to get it upright with a man, saw, fuel and bar oil in the bucket. If a hose didnt burst during those first three meters, i dont see it as a risk during vertical work either.
Now if the bucket is moved out of reach (allmost horizontally) and when the safety relief of the dump circuit opens, a hose bursts at the same time, i do have a problem.
In normal operations i dont fear hose bursts, because the most critical part of the journey is closest to the ground, when tipping it up from lying horizontally on the ground. I have to hold on anyways when its horizontally, because the manbucket tilt doesnt tilt that much.
I used to work as a design engineer for a small (now defunct) wheel loader manufacturer. We couldnt compete with the big boys on a standard machine, but when people wanted to use, e.g. a 22 meter extendible lift mast, we were the supplier of choice. By law, a load monitoring system should be installed that provides hose burst safety (electromagnetic valves mounted directly on the cylinder port) but also monitors cylinder pressure, and would switch off at 75% of nominal pressure. In reality, NONE of these clients use the full safety system (only the hose burst failure safety) because they arent competitive with 75% of outreach. Their biggest advantage is that they can drive with load, where telehandlers or telescopic cranes allways need their outriggers, which immobilise them so a big crane with far greater outreach than required is hired to get the job done in one lift. They prefer wheel loaders with parallel kinematics, and servo valves instead of electric valves, so the operator can "feel" the load from its control lever.
This business is running like this for decades with no accidents that drew attention of OSHA, or ARBO as its called in Holland, while operating on the edge virtually all the time.
Last edited:
MMagis
Veteran Member
That is without a doubt the most dangerous thing I’ve ever seen posted here. The idea is good, but the design got out of hand by trying to make it taller than it should have been. With the forces that thing is subjected to, it’s not a question of if it will fail, but when. And it’s not going to fail on the ground, it will fail while it’s up in the air with someone in it. Hopefully it’s not catastrophic and gives the tractor operator time to get the rider down, so he can change his britches.
MMagis
Veteran Member
Actually, I’m basing that off of my career as a design engineer, with a little common sense thrown in. There are plenty of platforms already on the market, but they’re designed by people with a good understanding of physics. No offense, but that thing isn’t safe in the long run.
NewLight
Bronze Member
:stirthepot: :laughing:
Rock knocker
Veteran Member
Cranes, boom lift and material handlers have pretty sophisticated hydraulics where a simple hose failure won't lead to a uncontrolled boom lowering. That is not the case with a simple ag tractor.
Read up.
https://www.worksafe.qld.gov.au/__data/assets/pdf_file/0017/83222/earthmoving_burstprotection.pdf
Yes they have pilot valves that
open the gravity loaded side when the oil pump creates pressure on the non loaded side so that it wont drop at a rate faster than the oil pump can fill the other side of the piston.
However these allways jerk a bit, which makes the machine pretty awkward for precise positioning and levelling. The electromagnetic system as i described in my earlier post, isnt worth it for my use.
The difference of a manlift and a farm loader is that the farm loader operates at 30% pressure with this weight, and the manlift at 75%. The chance of hose rupture is much lower because it would pop when picking up 1.5 ton with the forks, not when keeping 300kg upright