Frans
ArboristSite Operative
Frans and I just finished up the drop load test on the GRCS. I'm glad that's over, but still I have a heck of a job putting all the video clips together to make something out of it all.
Intrestingly, the repair cost on the supposedlly exploded GRCS was only $170. With it back in shape and running we subjected it to the same loads again.
3000 lbs/10 feet of slack
This time with a heavier duty fair lead and particular attention paid to securely mounting the device. The GRCS took the hit without exploding. The volvo was still in the air. Though the GRCS did slip up the trunk about its own length. The trunk was knotched on the root flair to hold the binding strap in place. If we didnt to that the device would have run completly up the trunk.
We went to the bollard next and used 5/8 lags to butt the base plate against. Knotched the unit into the tree and the binding strap. And subjected it to the same load. The device never moved, but the choker holding the load block broke sending everything to the ground. The choker cable hit the back of the volvo so hard it caved it in. I admit it was a used choker. 9/16, it had a kink near the nubbin and had surface rust. The first two drops must have a cycle or two too much.
The drop tests were interesting and I drew my own conclusions from them. In both units the fairlead was the weak link. They straightened out, letting the line escape and run out on the spool axis, applying the load where it shouldn't be and resulting in damaging the units. The GRCS was repairable, and I believe the Hobbs could be straightened by the factory. In normal use the units and their fairleads would never be subjected to such forces and would hold up incredibly fine.
For my own comfort, with either unit, I would change the fairleads to a closed system that would lock shut like the schackle on a snatch block. And have a cleat on the unit to tie the tail end fast to. That's only my feeling about it. You can draw your own conclusions after watching the video.
Working on the video and watching the action frame by frame in slow motion shows you things you can't see in real time. It's all very interesting and fun.
Should be done in a couple of weeks
All the best, Jerry B
Intrestingly, the repair cost on the supposedlly exploded GRCS was only $170. With it back in shape and running we subjected it to the same loads again.
3000 lbs/10 feet of slack
This time with a heavier duty fair lead and particular attention paid to securely mounting the device. The GRCS took the hit without exploding. The volvo was still in the air. Though the GRCS did slip up the trunk about its own length. The trunk was knotched on the root flair to hold the binding strap in place. If we didnt to that the device would have run completly up the trunk.
We went to the bollard next and used 5/8 lags to butt the base plate against. Knotched the unit into the tree and the binding strap. And subjected it to the same load. The device never moved, but the choker holding the load block broke sending everything to the ground. The choker cable hit the back of the volvo so hard it caved it in. I admit it was a used choker. 9/16, it had a kink near the nubbin and had surface rust. The first two drops must have a cycle or two too much.
The drop tests were interesting and I drew my own conclusions from them. In both units the fairlead was the weak link. They straightened out, letting the line escape and run out on the spool axis, applying the load where it shouldn't be and resulting in damaging the units. The GRCS was repairable, and I believe the Hobbs could be straightened by the factory. In normal use the units and their fairleads would never be subjected to such forces and would hold up incredibly fine.
For my own comfort, with either unit, I would change the fairleads to a closed system that would lock shut like the schackle on a snatch block. And have a cleat on the unit to tie the tail end fast to. That's only my feeling about it. You can draw your own conclusions after watching the video.
Working on the video and watching the action frame by frame in slow motion shows you things you can't see in real time. It's all very interesting and fun.
Should be done in a couple of weeks
All the best, Jerry B
