Rigging Physics 101 -- Redirect Pulley

[rfwoody]

This is a very simple question, but I would much appreciate a "sanity check" on my thinking and other pairs of eyes....

thanks for looking.

I hope this diagram is pretty clear and self-explanatory:



Just to reiterate the questions:

1) Will the redirect pulley (significantly) reduce the force applied to the victim tree?

2) Will the force on the victim tree increase significantly since all the horizontal movement of the truck will be applied to horizontal pull instead of some of the force being lost to vertical pull if the pull line was connected directly to the truck hitch?

3) AND possibly additionally(?) ... because *traction* of truck tires will not be reduced because of vertical pull... trying to pull the back of the truck up?

hope I haven't hopelessly confused this simple question.

Thanks a lot for your consideration and input!

 

[SeanKroll]

Try to get the redirect pulley AS LOW AS POSSIBLE AND SECURE. This will ideally lead upward to the truck, increasing traction.


If your pulling directly with the truck, the rope will be above-horizontal, negatively.





You really need throw line skills to get higher.

A load in bed does a lot for traction.




Try to find a YouTube explanation of vector forces.

Read Mark Chisholm's Engineering a Tree Removal article.

 

[rfwoody]

Thanks Sean!

 

[Burnham]

It's worth noting that tire chains can make a world of difference in traction on off road surfaces, not just snow and ice. Don't spin the tires, throttle control is critical.

 

[SeanKroll]

One on the gas, one with a little pressure in the brake... Two-foot driving.

Manuals aren't good for pulling slow and steady, like an automatic or winch.

 

[Burnham]

Of course, a winch beats all.

 

[squisher]

Depends on the manual. Just got to know how to use a clutch. All my work trucks have been manuals. Every bucket, my old ghetto 1ton, 550, couple of different 350's. You can certainly pull decently with a manual if you have the slightest bit of skill with a clutch.

 

[Burnham]

I'm with Squish on this one...although maybe somewhat more than "the slightest bit of skill" is needed .

I'd even argue that on some of the newer trucks with drive by wire throttles, an automatic transmission can be somewhat erratic in delivery of power as expected. This I know from both my personal pickup, and a couple of work rigs.

 

[Mick!]

Bloody yanks! Put them in a stick shift and they haven’t a clue!

Seriously though, manuals are absolutely fine as a pulling device.

To answer the questions directly.

1: not significantly.

2: never really thought about it before but yes, it’ll keep your wheels on the ground.

 

[Burnham]

Agreed, per Mick's answers . Otherwise...bloody Brits, so condescending. Especially the expats .

 

[Tree09]

Sticks are awesome, no power lost in the torque converter, and much more feel imo. 4x4 low solves most problems mentioned, my 7.3 in granny low and 4 low was at most .000002 mph lol

Force vectors in rope is very easy, line tension in the direction of pull. Your redirect tree will see much more, up to 2x the line force. You can also take the efficiency of the pulley to calculate the actual force lost. For example you have a 95 percent efficient pulley, and 1000 pounds on the line. So you only have 950 pounds going to the tree. Our apprentices are required to be able to calculate the forces on all rigging, with all sorts of angles, to simulate rigging using a tugger, which we use on big jobs all the time.

 

[Burnham]

 

[SeanKroll]

4 low, and stick is different than plain stick, imo.


I was warned about not pulling with a manual after my co-workers ruined the clutch on their bucket truck.

I stand corrected. Maybe they're fine. I've definitely pulled things with my manuals before, just not hard-pull-trees.

If it's a heavy pull compared to the vehicle, is that different than a light pull?


Much easier to stall and lose ground with a stick, I'd think.


I'm not sure how a guy I know glazed his bucket truck clutch. My only guess is pulling a big tree.

 

[flushcut]

The FOGTW has an entire chapter dedicated to line angles, worth checking out.

 

[Stumpshot]

And for the acronym impaired, that means...?

Jerry B's Fundamentals?

 

[rfwoody]

It's worth noting that tire chains can make a world of difference in traction on off road surfaces, not just snow and ice. Don't spin the tires, throttle control is critical.

Of course, a winch beats all.

I'm with Squish on this one...although maybe somewhat more than "the slightest bit of skill" is needed .

Agreed, per Mick's answers .

Thanks a lot Mr. Burnham... will you please see questions below?

Depends on the manual. Just got to know how to use a clutch. All my work trucks have been manuals. Every bucket, my old ghetto 1ton, 550, couple of different 350's. You can certainly pull decently with a manual if you have the slightest bit of skill with a clutch.

Thanks Squisher. putting questions/comments at end please.

One on the gas, one with a little pressure in the brake... Two-foot driving.

Manuals aren't good for pulling slow and steady, like an automatic or winch.

4 low, and stick is different than plain stick, imo.

I was warned about not pulling with a manual after my co-workers ruined the clutch on their bucket truck.

Much easier to stall and lose ground with a stick, I'd think.

Thanks Sean. putting questions/comments at end please.

Seriously though, manuals are absolutely fine as a pulling device.

To answer the questions directly.

1: not significantly.

2: never really thought about it before but yes, it’ll keep your wheels on the ground.

Ha, thanks Mick! short and to the point!

Sticks are awesome, no power lost in the torque converter, and much more feel imo. 4x4 low solves most problems mentioned, my 7.3 in granny low and 4 low was at most .000002 mph lol

Force vectors in rope is very easy, line tension in the direction of pull. Your redirect tree will see much more, up to 2x the line force. You can also take the efficiency of the pulley to calculate the actual force lost. For example you have a 95 percent efficient pulley, and 1000 pounds on the line. So you only have 950 pounds going to the tree. Our apprentices are required to be able to calculate the forces on all rigging, with all sorts of angles, to simulate rigging using a tugger, which we use on big jobs all the time.

Thanks Kyle. Yes I did enjoy vectors in school and I really appreciate your practical and theoretical knowledge of all this.
yeah, I wanted to make sure I understood correctly on the redirect pulley... that there is no significant loss of force except from pulley efficiency. Thanks for clarifying.

The FOGTW has an entire chapter dedicated to line angles, worth checking out.

Thanks Flushcut... yeah, just rechecked.... Chapter 31 "Pulling the Tree" (?) .... also in the DVDs he talks some about this I recall.
.... every time I go through Mr. Beranek's book and DVD's (or any other books (e.g. Jeff Jepson (thought not exactly same category)) I see something new to add to what has been more digested via experience.

========================================

General Comments and Questions to above if you please:

I have a 1995 Dodge 2500 which everyone says is a "beast" (relatively speaking of course).
The 4x4 low "granny" mode (and per Kyle) seems to give a lot of strong steady pulling power.
--- would this qualify as the "best" sort of scenario if using a truck to pull?

Winches ------ would you trust a Harbor Freight winch in your work? ..... or would you trust nothing less than a Warn (or comperable).

Thanks!

 

[SeanKroll]

Is factory reverse typically geared lower (more powerful gear ratio) than first gear, in passenger trucks? Medium duty?


Being able to see the tree, if backing away, sometimes helps.

 

[flushcut]

And for the acronym impaired, that means...?

Jerry B's Fundamentals?

Yes

 

[SeanKroll]

aka FOGT in some references.

 

[Burnham]

Robert, in my experience, your truck (assuming top operating condition) is an excellent tool for the job. I drove one just like it for 7 years, over 80k miles, 80% on backwoods logging roads. A USFS rig.

As for the question of Warn vs. Harbor Freight. I have no experience with the latter. They may be wonderful...or for all I know, crap. There are other manufacturers out there too. But again, I have extensive experience with 3 different Warn models, and no other. To be clear, I am definitely prejudiced, but with no decent standing for comparisons.

But I do see the prices. A 12k Warn will run you about 400-500 dollars more than a 12k Badland (Harbor Freight). I'd spend that pissant bit of money more in the drop of a hat, for a tool I KNOW will work hard, and for a very long time. I'd go with Warn, myself.

Now if you can get positive feedback from real people with real experience with the Badland models, I say go with that info...I just don't know anyone among my friends and fellow woods workers who has gone that route.

 

[flushcut]

Warn is pretty much the gold standard for winches.

 

[Jonny]

So depending on which Warn winch you're considering, you might already be in the price range of a gas powered capstan winch, or maybe a Lewis winch.

Just to make sure we're not missing out on something basic here, what kinda knot you gonna use to tie to the truck hitch? A bowline unties easy after yanking with a truck.

 

[Stumpshot]

We've standardized on a doubled bowline for pulling with a truck -- comes undone very well no matter how much pull you've put on it (chip truck, log truck, skid steer).

 

[Marc-Antoine]

Is factory reverse typically geared lower (more powerful gear ratio) than first gear, in passenger trucks? Medium duty?

Not in my car and van. The reverse seems between 1 and 2. I have to use harder the clutch, backing on a slope when loaded.

If you need a high torque /strong pull with a stick, but at a slower pace than allowed by the gear at this motor's speed, you can't do it otherwise than slipping continuously the clutch. That works well and can be precise enough but only for a relative short time because the clutch heats up quickly with all the excess of energy coming from the engine. Do it too long and the clutch is toast.

 

[treesmith]

Depends on the manual. Just got to know how to use a clutch. All my work trucks have been manuals. Every bucket, my old ghetto 1ton, 550, couple of different 350's. You can certainly pull decently with a manual if you have the slightest bit of skill with a clutch.

I drove a 1995 Chevy 3/4 ton 4x4 for 13 years that had a 5-speed manual. I bypassed the clutch-starter switch right off the bat. When pulling a leaner, I'd pretension, notch and start back cut, then just lean in and wind the starter a second to further tension it (in 4-LO). I loved that manual tranny for pulling trees.