willie59
Administrator
Ok, this doesn't look good.
I wanted to post this to point out to anyone out there that uses aerial lifts; these machines have limitations. To push one beyond the designed capabilities of one is extremely dangerous, and somethimes deadly. Only God knows how this operator escaped serious injury or death.
Got a call from a customer about a JLG 80HX+6 that came off a grade in an "out of control" manner. When I arrived on the site, it didn't take me long to sort out what happened. Near the bottom of the grade, it appears the operator released the drive controller, which would have applied the brakes. That's when the left drive wheel brake engaged, but the right drive wheel continued rolling. This is a two wheel drive machine, so it only has two brakes. With one wheel not braking, there's no way only one wheel can hold a near 37,000 lb (16,783 kg) machine. So the left drive wheel began to skid the tire, and it left a long skid mark which indicated the machine was traveling at a fair clip. I'd wager the operator did not come off this hill in high drive, but rather in low, yet the machine did not hold back in low speed and began moving with excessive speed. When the left wheel finally braked at the bottom of the driveway, by now the operator had no real control. That's when the right wheels ran off into large rip rap rocks. I'm certain that man basket began bouncing the operator violently, I'd say he was gripping the handrails with all the strength he had, unable to let go and steer the machine, hoping and praying the machine would come to a stop.
Given the right drive wheel did not apply brake, I started checking there. Found the planetary hub components good. Removed covers of drive motor, found oil, yet no failed hoses. Something going on in there.
Upon removal of drive motor, found motor shaft seal blown outward,indicating excessive internal pressure on the seal which typically means a failed motor. Here's a pic of the motor shaft, you can see the portion of seal pushed out on the shaft.
When I first arrived at the machine, I tried to operate the drives. It didn't even put any hyd load on the engine. Once I removed the right drive motor and capped those hyd lines, tried drive again using left drive motor, still no load on engine. Removed the left drive motor, capped the hyd lines to motor, tried drive again. Now the engine went under load and opened drive circuit relief valve. So the machine had both drive motors failed. Then how did it move you ask? Probably, the left drive motor was already dead and machine was only moving using right drive motor. No way an operator would know this. So he would have come off this grade with only the right motor holding back the
machine. With such pressure on one motor, boom! Seal blows out, fills the dry brake assembly with oil, and now the motor has no hold back power. The brake is now well lubricated, so it can't perform it's task to help stop the machine. This thing was an accident waiting to happen, and it's probably all as a result of the customer using this machine to go up and down hills that the machine is simply not designed to do putting excessive stress on the machine components. You must respect and heed the working
limitations given by the manufacturer with these machines, or you'll put your self and co-workers in a perilous situation.
Here's a video clip I made while on site. Sorry about the poor video quality. My
Blackberry appears to have issues in video mode.
YouTube - Stuck JLG‎
I wanted to post this to point out to anyone out there that uses aerial lifts; these machines have limitations. To push one beyond the designed capabilities of one is extremely dangerous, and somethimes deadly. Only God knows how this operator escaped serious injury or death.
Got a call from a customer about a JLG 80HX+6 that came off a grade in an "out of control" manner. When I arrived on the site, it didn't take me long to sort out what happened. Near the bottom of the grade, it appears the operator released the drive controller, which would have applied the brakes. That's when the left drive wheel brake engaged, but the right drive wheel continued rolling. This is a two wheel drive machine, so it only has two brakes. With one wheel not braking, there's no way only one wheel can hold a near 37,000 lb (16,783 kg) machine. So the left drive wheel began to skid the tire, and it left a long skid mark which indicated the machine was traveling at a fair clip. I'd wager the operator did not come off this hill in high drive, but rather in low, yet the machine did not hold back in low speed and began moving with excessive speed. When the left wheel finally braked at the bottom of the driveway, by now the operator had no real control. That's when the right wheels ran off into large rip rap rocks. I'm certain that man basket began bouncing the operator violently, I'd say he was gripping the handrails with all the strength he had, unable to let go and steer the machine, hoping and praying the machine would come to a stop.
Given the right drive wheel did not apply brake, I started checking there. Found the planetary hub components good. Removed covers of drive motor, found oil, yet no failed hoses. Something going on in there.
Upon removal of drive motor, found motor shaft seal blown outward,indicating excessive internal pressure on the seal which typically means a failed motor. Here's a pic of the motor shaft, you can see the portion of seal pushed out on the shaft.
When I first arrived at the machine, I tried to operate the drives. It didn't even put any hyd load on the engine. Once I removed the right drive motor and capped those hyd lines, tried drive again using left drive motor, still no load on engine. Removed the left drive motor, capped the hyd lines to motor, tried drive again. Now the engine went under load and opened drive circuit relief valve. So the machine had both drive motors failed. Then how did it move you ask? Probably, the left drive motor was already dead and machine was only moving using right drive motor. No way an operator would know this. So he would have come off this grade with only the right motor holding back the
machine. With such pressure on one motor, boom! Seal blows out, fills the dry brake assembly with oil, and now the motor has no hold back power. The brake is now well lubricated, so it can't perform it's task to help stop the machine. This thing was an accident waiting to happen, and it's probably all as a result of the customer using this machine to go up and down hills that the machine is simply not designed to do putting excessive stress on the machine components. You must respect and heed the working
limitations given by the manufacturer with these machines, or you'll put your self and co-workers in a perilous situation.
Here's a video clip I made while on site. Sorry about the poor video quality. My
Blackberry appears to have issues in video mode.
YouTube - Stuck JLG‎
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