oregoncutter
ArboristSite Operative
There are two kinds of motorized carriages.
One kind has a drum and a bigger motor. They are heavy and built flimsy to keep the weight down as much as possible. If you drop them or even bump them they are broke and a big bill but they are fast.
Second kind is what you're talking about. They have a hydraulic system in them to apply the skyline clamp ( two aluminum shoes) and the clamp on the skidding line/drop line. Also they have a live wheel in them that when the skidding line is forced into, pulls slack from the yarder. They are tougher then the kind with a drum but slower because you can only perform one function at a time where the kind with a drum in them you can drum a turn to the carriage while the yarder is skidding the turn.
Carriage is stopped at the turn, skyline clamp on, skidding clamp off. Activate slack puller by line being crowded into live wheel. Drop line powers off to you. Set your turn then skidding clamp off, pull turn up to carriage then skidding clamp on, skyline clamp off and turn goes to landing.
So what about the mechanical dropline carriage. Carriage is tough, you can drop it, bang it, what ever it's good to go but there are draw backs.
First you need a yarder built for it like a grapple yarder which cost more.
Second more work for the hook tender sometimes requiring a pimp.
To understand you have to know how much extra rigging there is. On a skyline you have to string one leg of strawline on the mechanical you need to string two legs plus the blocks. Skyline, one small tommy will do. On the mechanical you're using haulback blocks which are about 75 pounds and 7/8 or 3/4 straps plus you are most often rigging tail trees because you can't hang way back to get lift like you can with a skyline. Last one I worked on I had two 15 inch tailblocks and two 13 inch tree blocks for each road so that is 8 haulback blocks you're lugging around plus 7/8 straps, 3/4 tree chokers, 4 150'x1/2" guylines, climbing gear, pass rope, axe, saw and maybe some coils for twisters. That not counting the strawline to string the road line. My back starts hurting again just thinking about it.
Another thing the MSP carriages are very hard on line. I usually figured to splice on average one eye a day. They do go through haulbacks too. Steady logging, I'd say you would be lucky to get a year out of a haulback.
Most the clampline carriages I have seen were ACME brand carriages, Humptulips explained it right on the money as far as how they work, definitely have to be fast and accurate blowing whistles to it, and the yarder separate bugs of course then if the function box in the yarder wasn't working we used to blow a short between functions to let the operator know we were changing functions it all becomes fluid after awhile and a good rigging slinger can move some wood with one. Most the Internal drum dropline carriages I have been around were Boman and a few Danebo"s, the Bomans are actually pretty well built they run a deutz air cooled 4 or on our bigger ones a 6 cylinder diesel, there are electric over pneumatic valves mounted in them when you blow for a function it sends voltage from the box to the solenoid valve or valves which are normaly closed and the pilot shifts the piston and lets air out the function side of the valve until it's triggered again, which depending on function will then engage your'e drum, brake throttle, or whatever function You ask for. They operate the drum by hydraulics from a belt driven pump mounted near the rear of the carriage, the torque converter it's self is powered by a belt driven torque pump on the front of the motor, the air for the solenoids, brake cylinder, and throttle control, come from an air compressor similiar to what You would see on an old semi or yarder, I have seen them crash and recover pretty well, but when they crash too hard they do cost alot to repair. I have seen them come in with the belly pan broke and shoved through the oil pan, motor mounts broken, front engine covers busted in pieces, frames bent You name it. The factory parts are very expensive, but we build what we can in house, and rebuild motors, and most of the drive train. They offer alot of options for example You can change gear ratios for the drum so if You have alot of lift and need too drop or suck up some line real quick You can change the gears. Anyway other than the weight, and maintenance and repair costs I like the Boman carriages.