Another aerial friction rigging device?

JMerritt

Well-Known Member
Location
santa cruz
I looked up your machine. Nice. You're in the world of R8. Tip - keep a nice 6" adjustable for the drawbar and many other things. Make a small 3 or 4" 2x4 cutoff and use it as a hammer to pop the collet wedging when loosening, pound with the end grain. My machine takes one or two good taps to break free. One hand tapping, other holding the tool which may drop out of the collet as you tap. Likewise, one hand on tool, finger spin draw bar, then snug with adjustable while still holding. This will become 2nd nature.

Consider some type of hour meter for wear and tear.

It almost never hurts your tools to cut slower or lighter than for production, and prolongs tool life. No need for smoke except on stainless.

Also, old saw files that don't do well on chains are still great for regular metal work. Different standards of performance.

They don't sell my machine anymore. Its about 600 lbs with about 4" cylindrical vertical, similar table movements and sizes to yours. 4 T slots. manual feed, 0.001" dials. no dro. R8. 5" quill travel plus head vertical repositioning. Even with 5" I bought a short set of drill bits fractional sizes, saves my bacon every so often.
Omg, short drill bits! The thought never even crossed my mind and now I feel so dumb! I know what I’ll be ordering tonight . For the the drawbar I use a 12 point socket on my cordless impact driver. It works awesome and the drawbar has a top collar that ejects they collets if you back id off all the way. No hammer needed. You ever watch dan gelbarts YouTube videos? Well worth checking out.
 

theatertech87

Well-Known Member
Location
Rochester
A very clever friend of mine suggested using a small torque converter in reverse.

An adjustment could be built in with a Bluetooth controller so that the rigger/cutter could make changes remotely.

Turn it completely open for trading the rope end back up. Then preset a load for the drop

Any Canadians here might know @Dave Spencer as the second place winner in ‘Canada’s Biggest Know it All’.

So just day dreaming about other options... There is a video a saw shop posted of their saw testing rig that i'll be darned if I can find, where they use a hyrdaulic pump to build pressure through a flow control and shear fluid to increase the load on the saw to simulate a cut. Kind of like a torque converter but adjustable. Heat could be an issue, but honestly if we were generating that much heat to be an issue, we'd likely be seeing reports of rigging rings melting the slings they were attached to.

Might also be able to do something with an electric motor or alternator. Some sort of regenerative braking like in an electric car (could generate enough energy to be stored and used to run low power remote control?) or just dump the energy into a resistor grid and let it be air cooled. Or short the terminals and let the magnetic fields fight each other and add resistance. Could even make it fit into a block... Coils in each shiv plate, magnets in the pulley sheave, highly custom of course, but i'd guess something the size of a large dmm impact block? This is already field tested (in essence) with the heated handle saws, so we know it can survive most of the abuse we hand out to tools already

Could use a gear box and run it in reverse, high to low, though it would of course provide less resistance the longer it was used as the gears came up to speed... AND you'd have the issue of a non instant stop due to the gears coasting back down

Could do a recoil spring on steroids too (ok probably not) but that would give you increased friction the longer you loaded it.

I kind of like the idea of a centrifugal clutch as well, though that i think would be highly rope type/diameter specific. designed such that it either takes very little rotation to engage and squeeze, or something that functions like the hitch hiker, where there is squeezing motion brought about by linear travel and load
 

Merle Nelson

Well-Known Member
Location
SF Bay Area, CA
"So just day dreaming about other options... There is a video a saw shop posted of their saw testing rig that i'll be darned if I can find, where they use a hyrdaulic pump to build pressure through a flow control and shear fluid to increase the load on the"


Myrtle Creek Saw Shop...Saw King(?) or Chainsaw Guy(?).
 

theatertech87

Well-Known Member
Location
Rochester
"So just day dreaming about other options... There is a video a saw shop posted of their saw testing rig that i'll be darned if I can find, where they use a hyrdaulic pump to build pressure through a flow control and shear fluid to increase the load on the"


Myrtle Creek Saw Shop...Saw King(?) or Chainsaw Guy(?).
I thought it was saw kings ior west coast saw, but I couldn't find it
 

JMerritt

Well-Known Member
Location
santa cruz
I had an idea a while back for a clutch mechanism. Imagine a pulley wheel with an oversized center hole. The pulley bushing rides on a pair of braking shoes and there is a wedge shaped piece between them. The wedge rides in a slot in the side plates. When the wedge is oriented sideways there is no pressure on the shoes and the sheave is free to spin. When the thing is tipped 90deg the wedge forces the brake shoes out, pressing against the bushing and stopping the sheave. Instead of a smooth sheave the device would use something like the maasdam comealong or grcs grip ring to hold the rope tight when locked. If the rope ran over a fairlead on the end of a lever then the ground operator could vary the amount of braking by pulling the rope end. Or there could be a way to set and lock the wedge angle for a constant friction setting.
 

Bart_

Active Member
Location
GTA
Jamie, I'll check out Gelbart, saw just a bit so far. You torque limit your drawbar tightening? Doesn't take much. Check out This Old Tony for some entertainment. What's the little lathe?

On your drum brake sheave, the shoes and drum absorb the heat whereas in rope bolllard there's some percentage split which I don't know, but point being a bunch of heat is spread out along the rope = higher capacity. I get your drift re some feedback mechanism. On most gizmos there's a fixed ratio of force amplification of the groundie via the bollard equation, number of wraps , partial wraps/bends etc. One generally sets the ratio and then modulates from near zero to my hand hurts. I say near zero because rope tail weight can hold some pieces on a BMS belay spool with two wraps. Mechanically you can do feedback, e.g. angled brake shoes like in a one way silent clutch. They use enough to head straight to lock up, but less can be amplification. Here's a head bender. Take e.g. the hitch hiker, the dog bone gets +ve feedback tighter into the rope with rope motion while the body gets -ve feedback away from the rope by the rope motion/friction. So who wins, is it overall +ve or -ve? Only the shadow knows for sure. Something like the R500 its all -ve so it settles to s speed/load point. On a disc brake there's neither +ve or -ve as the pistons/pads are at normal i.e. 90 degrees.

See all the mechanical giblets in the aerial adventure tech fan? Holy cow. Something's a gonna break.
 

JMerritt

Well-Known Member
Location
santa cruz
Jamie, I'll check out Gelbart, saw just a bit so far. You torque limit your drawbar tightening? Doesn't take much. Check out This Old Tony for some entertainment. What's the little lathe?

On your drum brake sheave, the shoes and drum absorb the heat whereas in rope bolllard there's some percentage split which I don't know, but point being a bunch of heat is spread out along the rope = higher capacity. I get your drift re some feedback mechanism. On most gizmos there's a fixed ratio of force amplification of the groundie via the bollard equation, number of wraps , partial wraps/bends etc. One generally sets the ratio and then modulates from near zero to my hand hurts. I say near zero because rope tail weight can hold some pieces on a BMS belay spool with two wraps. Mechanically you can do feedback, e.g. angled brake shoes like in a one way silent clutch. They use enough to head straight to lock up, but less can be amplification. Here's a head bender. Take e.g. the hitch hiker, the dog bone gets +ve feedback tighter into the rope with rope motion while the body gets -ve feedback away from the rope by the rope motion/friction. So who wins, is it overall +ve or -ve? Only the shadow knows for sure. Something like the R500 its all -ve so it settles to s speed/load point. On a disc brake there's neither +ve or -ve as the pistons/pads are at normal i.e. 90 degrees.

See all the mechanical giblets in the aerial adventure tech fan? Holy cow. Something's a gonna break.
I enjoy this old tony for sure. The lathe I’ve got is an atlas 9”. It needs some work to get it running, but it was free! As for the drawbar, I don’t torque it too hard. Just enough to get a click or two out of the driver.
Yeah, I never pursued the drum brake beyond a concept sketch. Too far outside my comfort zone and way beyond my fabrication skills. Heat would definitely be a big issue, as well as wear.
an interesting phenomenon I’ve noticed with the akimbo, and I’m sure other mechanicals to some degree, is that aluminum gets more slippery the hotter it gets ( or maybe it’s the rope). Long hot descents can get pretty interesting if you’re settings start loose.
friction on rope is pretty fascinating. I’ve spent a lot of time looking at rope runners, hitchhikers, and bdbs trying to fathom how it all interacts to form a functional device. There is definitely some alchemy in there somewhere. And so many interdependent forces and interactions between components. Look at the simple rope wrench. You’d think that it bends the rope and provides x amount of drag to your system, but think about its interaction with the tension on the rope itself. If the rope is fully slack then the wrench is producing almost no drag. Now imagine a rope with enough tension on it that it won’t even bend in the wrench, that wrench isn’t going to move one inch no matter how hard you pull on it. So the amount of friction given at the wrench is dynamic, maybe it’s a pretty constant ratio of the total weight on the system but I don’t think anyone has measured that.
 

Bart_

Active Member
Location
GTA
I tried to do rope wrench measurements on my version back in the day and the variation of conditions eventually averaged out to Kevin's statement of "about 2:1". It was cool seeing the angle it settled to and how that geometry sort of self dictated itself by function. The 2:1 being favourable depends on not having a bunch of rope tail weight, particularly a second climber which is practically the wrench can't bend the rope case.

Take some time and you'll eventually envision how the wrench balances into angle, bend, bollard friction and tether vs hitch force levels. I promise its worth it.

My first grey rope wrench had not one but two eccentric bollards and no pulley, but no indexing pins for repeatable settings like the akimbo. I eyeballed the rope fit or verniered it. Still have that wrench but don't use it except on second SRT line when needed. I also went 1/2" on the steel bollards as I thought otherwise was tough on the rope. But it was too much trouble to radius the bollards so they stayed cylindrical.

Some years ago I made a gizmo like a linear sailboat rope clutch but intended to slip the rope and place like a hitch hiker. Not viably midline attachable, but a pretty high gain device easy on ropes with big heat absorbing contact surfaces. My son and I took turns burning/racing descent out of the tree and it released so well you could go basically free fall and then catch yourself. But I balked at its inline life support position, so I extended the hitch cord as a (messy) redundant bypass to the bridge carabiner and then kind of shelved the whole thing. I never came up with an elegant as you climb tuning for it so it was made for a particular rope size, tachyon.

Yeah, on heating up descenders, just think about what parts can heat a small point and tend into rope glazing territory.

Have you done any boring head stuff yet?
 

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