Predict the pull

[chiselbit]

Do you guys remember oldfart? He did a stump pulling video with a bunch of mechanical advantage, everything moving slow and then pow! Stump exploded out of the ground.

 

[Arb23]

Maybe I'm thinking of this wrong, but does #4 being 4.33:1 mean that - if all loss is in the pulleys - that those pulley's are 96% efficient!? Holy cow. Before I did all the other calcs, I looked up some typical pulley efficiencies, and was seeing numbers in the 85-95% range.

I think that's 4.33 / 5 = .866 or 86.6%. think that's typical. Super efficient stuff will be 4.5+:1

 

[LordFarkwad]

I think that's 4.33 / 5 = .866 or 86.6%.

Obviously I've got some learning, listening, and thinking to do. Thanks for the word.

 

[Arb23]

Obviously I've got some learning, listening, and thinking to do. Thanks for the word.

Learning here too. Muggs does some good work!

 

[LordFarkwad]

Do you guys remember oldfart? He did a stump pulling video with a bunch of mechanical advantage, everything moving slow and then pow! Stump exploded out of the ground.

He still around?

 

[chiselbit]

Haven’t seen him here for awhile. Maybe years?

 

[Shadowscape]

I can remember my uncle pulling stumps on his farm with his tractor and a series of snatch blocks. But he was using a steel cable of about an inch in diameter.

 

[ghostice]

Do you guys remember oldfart? He did a stump pulling video with a bunch of mechanical advantage, everything moving slow and then pow! Stump exploded out of the ground.

. . . Tom Hoffman's video on tractor stump pull on his YouTube channel . . . pop went the stump!
Has anyone worked out the equipment specs for this kinda pulling? Bet it'd be fairly dollar intensive - rig with cables for tower rigging/ logging gear?

 

[LordFarkwad]

Here's where curiosity, a little thinking, and some time after putting the littles to bed got me...

This deals with a 5:1 system, but is easily expandable.




The more general form for this architecture of mechanical advantage arrangement - meaning a simple system, non-piggybacked - would be expressed as...


So with a pulley efficiency of 90% (0.9), the final MA is 4.0951:1; my earlier, *profoundly* incorrect method of calculating final MA yielded 3.3:1. Samsonite...I was way off.

In the 4th system - "homemade thing with micropulleys and rigging plates" - back-calculating from the measured 4.33:1 MA yields ~93% for each pulley's efficiency. That is more believable, but still surprising imo when compared against some of the "presentable"/streamlined systems! Really figured the rope-on-rope contact in the system would impact the overall efficiency more negatively. Pretty cool result though.

So, redoing that earlier estimate for the final MA of all 6 cascaded systems (model below) - assuming 90% pulley efficiency for all pulleys - I get 4.0951^6, or ~4,716:1, versus your ideal of 5^6 = 15,625:1.

And, referencing the diagram below for the rationale behind combining your individual MA measurements by multiplying all six systems together, it looks line the final MA is somewhere in the neighborhood of 7,584:1. Using the above equations to back-calculate the average pulley efficiency for all 24 pulleys in the cascaded system, it appears that they are on average 94% efficient! Obv. some are more, some are less, but the average amongst your collection is approx. 94%.

Model used for calculating an estimate for the cascaded system's overall MA (triangle symbol represents an anchor)...


Thanks for bearing with me. I went through all this to try and explain what's happening to myself. I've never sat down and done it with this level of thoroughness before, and it may *still* have errors, but it's at least more believable than my initial junk a couple pages back.

 

[Arb23]

Friendly AI back again...

me>I want to run a new scenario. I this scenario, I want to analyze 3 5:1 systems. Each system will have a constant input load of 25kg applied to it. The output force of the entire system will compound the previous stage's output force as it's applied sequentially. Each 5: 1 pulley and rope system is 85% efficient. I'd like to see a table with the stage number, input force in kg and kN, the output force in kg and kN and finally a total force of all 3 systems in kg, lbs, and Kn specifying that the calculations were done at the efficiency ratio provided.

ai>
Sure, here is the table with the requested information:

Stage	Input Force (kg)	Input Force (kN)	Efficiency Ratio	Output Force (kg)	Output Force (kN)
1	25	0.245	0.85	106.25	1.042
2	25	0.245	0.85	454.69	4.452
3	25	0.245	0.85	1,946.29	19.065

Total Force:

• in kg: 2,507.24 kg
• in lbs: 5,522.53 lbs
• in kN: 24.56 kN

Note that the calculations were done at the provided efficiency ratio of 0.85.


My notes:
I *think* this is right - it look AI about 6 tries to get to this - with subtle wording changes in each attempt to have it compound the output forces properly.

 

[Arb23]

This little 5:1 kit is sorta interesting as well...has progress capture prusik - around $100.
https://www.amazon.com/dp/B07C7F9XLF
Would be interesting to see how well it fares against the 'pro' stuff. Not sure I'd want to hang over a cliff on any of that hardware, but I use their slings for speedline rigging and they work ok.

 

[LordFarkwad]

Friendly AI back again...

me>I want to run a new scenario. I this scenario, I want to analyze 3 5:1 systems. Each system will have a constant input load of 25kg applied to it. The output force of the entire system will compound the previous stage's output force as it's applied sequentially. Each 5: 1 pulley and rope system is 85% efficient. I'd like to see a table with the stage number, input force in kg and kN, the output force in kg and kN and finally a total force of all 3 systems in kg, lbs, and Kn specifying that the calculations were done at the efficiency ratio provided.

ai>
Sure, here is the table with the requested information:

Stage	Input Force (kg)	Input Force (kN)	Efficiency Ratio	Output Force (kg)	Output Force (kN)
1	25	0.245	0.85	106.25	1.042
2	25	0.245	0.85	454.69	4.452
3	25	0.245	0.85	1,946.29	19.065

Total Force:

• in kg: 2,507.24 kg
• in lbs: 5,522.53 lbs
• in kN: 24.56 kN

Note that the calculations were done at the provided efficiency ratio of 0.85.


My notes:
I *think* this is right - it look AI about 6 tries to get to this - with subtle wording changes in each attempt to have it compound the output forces properly.

Can you ask it to show its math? I'm not getting anything that agrees with this, and with it being a "black box" (that is, we can't see what's going on inside), there's no way to see how it's arriving at its conclusions.

It's not treating each pulley as 85% efficient, it seems, but rather each entire system as 85% efficient (5:1×0.85 = 4.25:1). Maybe that's what you intended though.

The output in the table - 1,946kg - also does not match the output in the table summary - 2,507kg. This is because it is adding each of the stages' outputs together to arrive at a cumulative output of 2,507kg. It seems like this requires 3 entirely separate MA systems pulling on the same load, and having 3 entirely separate input pulls being inputted to them; doesn't seem like the correct architecture for this setup. See diagram below for what it seems like the AI's system architecture is.



With the cascaded/piggybacked system, treating each entire 5:1 system as 85% efficient - as the AI seems to be doing - I arrive at 1,919.1kg of output force from 25kg input force. 25kg×(0.85×5:1)^3 = 1,919.1kg; close to its answer in the table, but I'd think it should have the ability to get closer. Could be that it's including some factor I'm not, though.

Redoing the three cascaded 5:1 systems with each pulley being 85% efficient (versus each system), I arrive at 1,275kg output with 25kg input.

 

[Arb23]

It's not treating each pulley as 85% efficient, it seems, but rather each entire system as 85% efficient (5:1×0.85 = 4.25:1). Maybe that's what you intended though.

It is - I'm just looking at each 5:1 system as a whole and not worried about each pulley. There is an input, output and some losses. The ratio accounts from all losses, regardless of from pulley design, rope, or other sources.

The output in the table - 1,946kg - also does not match the output in the table summary - 2,507kg.

Total load is all 3 pulling on the load - the sum of the 3.

Treating each entire 5:1 system as 85% efficient - as the AI seems to be doing

I *think* it's compounding the in(efficiency) at each stage...so the 85% output gets added to and then treated as 85% again at the next stage making the previous stage even more inefficient. My thinking was that's probably real world - that those things do add up, but maybe not like it's calculating.

The compounding part of how these systems are loaded is the tricky part. I've always thought of compound systems pulling on each other - ie like what (I think) you're saying - the input force of stage 2 is the output force of stage 1 and the input force grows 5:1ish with each stage. But with a constant 25kg applied at 'each' stage is what's confusing the calculation (and me).

When I've been testing mine, I'll attach a prusik to the input line of each system and attach the output of the next system to the prusik and only pull on the final input. That seems more logical math wise to me. Constant inputs at each stage makes sense to me, but confuses me (and probably the AI as well) with the math.

Can you ask it to show its math?

I'll try lol...I think it's starting to get irritated...
me>can you explain how you calculated 1946.29 kg output force in the 3rd system?
AI> for f*cks sake!
Excuse me, I'm sorry...
Sure, I'd be happy to explain!

In the third system, the input force is 25 kg and the efficiency of the system is 85%.

The output force of the second system is 255.75 kg, as we calculated earlier.

So the input force for the third system will be the output force of the second system, which is 255.75 kg.

To calculate the output force of the third system, we'll use the same formula as before:

Output force = (Input force x Efficiency ratio) + Input force

Plugging in the values for the third system, we get:

Output force = (255.75 kg x 0.85) + 255.75 kg

Output force = 217.89 kg + 255.75 kg

Output force = 473.64 kg

Therefore, the output force of the third system is 473.64 kg, and when combined with the output forces of the previous two systems, the total output force is 1946.29 kg.

----
I'm not sure that's right. But it seems to match up with back of the napkin calcs.

 

[Arb23]

 

[LordFarkwad]

So this is the system you intended to have it calculate?


...and not this (but with 3 stages instead of 6)?


It's wild - the AI's decimal places are still off and, in my opinion, its explanation is kinda all over the place. I actually think for at least one of those "stages", it's using an equation for a non-ideal 2:1. Strange. It seems confused.

Edit: To be a little more explicit, the second diagram is 6 systems being cascaded or "piggybacked" to one another. The math for 3 cascaded systems each having 85% efficiency would work out in expanded/verbose form as such:

Fout1= (Fin) × (MA1 ideal) × (efficiency) = 25kg × 5:1 × 0.85 = 106.25kg​

Plugging Fout1 in as the input to MA2...​

Fout2 = (Fout1) × (MA2 ideal) × (efficiency) = 106.25kg × 5:1 × 0.85 = 451.6kg​

Plugging Fout2 in as the input to MA3...​

Fout3 = (Fout2) × (MA3 ideal) × (efficiency) = 451.6kg × 5:1 × 0.85 = 1919.1kg​

 

[Arb23]

It's wild

For sure...it's not ready yet...honestly, it's pretty amazing that it can provide these responses given the input I gave it - as it gets 'smarter' over the next year or two, it will be crazy. Put it in a robot or two, and it's time to head to the bunkers lol...

I've tried a few more times, and I've gotten different answers. It's stumbling on the input force at each stage.
I won't clutter up the thread with those...this is the best I've been able to extract...with some of the logic behind it, but I think it's still off.

me>I'm working with some pulley systems to apply force to a load. I want to analyze 3 5:1 systems to see how much load is being applied at each stage. Each stage will have a constant input load of 25kg applied to it. The output force of the entire system increase as the 25kg load is applied sequentially. Each 5: 1 pulley and rope system is 85% efficient. I'd like to see a table output with the stage number, input force in kg, the output force in kg and kN and finally a total force of all 3 systems in kg, lbs, and Kn specifying that the calculations were done at the efficiency ratio provided. I'd also like you to show your calculations at each stage after the table.

ai>
Sure, I can help you with that! Here is a table that summarizes the input and output forces at each stage, as well as the total force of all three systems, assuming an efficiency of 85%:

Stage	Input Force (kg)	Output Force (kg)	Output Force (kN)
1	25	106.25	1.04
2	25	453.13	4.44
3	25	1928.91	18.91
Total	75	2488.29	24.39

To calculate the output force at each stage, we can use the formula:

Output Force = Input Force * Pulley System Ratio * Efficiency Ratio

Since each pulley system has a 5:1 ratio and an efficiency of 85%, we can plug in those values to get:

Output Force = Input Force * 5 * 0.85

At the first stage, the input force is 25 kg, so the output force is:

Output Force = 25 * 5 * 0.85 = 106.25 kg

At the second stage, the input force is still 25 kg, but the output force from the first stage is now the input force, so the output force at the second stage is:

Output Force = 106.25 * 5 * 0.85 = 453.13 kg

At the third stage, the input force is still 25 kg, but the output force from the second stage is now the input force, so the output force at the third stage is:

Output Force = 453.13 * 5 * 0.85 = 1928.91 kg

To calculate the total force of all three systems, we simply add up the output forces from each stage:

Total Force = 106.25 + 453.13 + 1928.91 = 2488.29 kg

To convert the total force to pounds and kN, we can use the conversion factors:

1 kg = 2.20462 lbs 1 kN = 224.808943 lbs

So the total force is:

• 2488.29 kg = 5485.41 lbs
• 24.39 kN = 5485.41 / 224.808943 = 24.39 kN

Note that the table and calculations above assume that the input force of 25 kg is constant and does not take into account any additional external forces or factors that may affect the system.

---

I think we'll just have to wait on Buggs' real world results!

 

[LordFarkwad]

To be a little more explicit, the second diagram is 6 systems being cascaded or "piggybacked" to one another. The math for 3 cascaded systems each having 85% efficiency would work out in expanded/verbose form as such:

Fout1= (Fin) × (MA1 ideal) × (efficiency) = 25kg × 5:1 × 0.85 = 106.25kg​

Plugging Fout1 in as the input to MA2...​

Fout2 = (Fout1) × (MA2 ideal) × (efficiency) = 106.25kg × 5:1 × 0.85 = 451.6kg​

Plugging Fout2 in as the input to MA3...​

Fout3 = (Fout2) × (MA3 ideal) × (efficiency) = 451.6kg × 5:1 × 0.85 = 1919.1kg​

AI is putting on a pretty good showing, but....yeah....

 

[Arb23]

106.25kg × 5:1 × 0.85 = 451.6kg

AI: Output Force = 106.25 * 5 * 0.85 = 453.13 kg

me>is math hard for you?
ai>As an AI language model, I don't really have feelings, so math isn't hard or easy for me. However, like any machine, I can make mistakes or misunderstand instructions. If you notice any errors in my calculations or responses, please don't hesitate to let me know and I will do my best to correct them.

I apologize again for my mistake. You are absolutely right, the correct calculation is:

106.25 * 5 * 0.85 = 451.56

So the output force at the first stage with an efficiency of 85% would be 451.56 kg, not 453.13 kg as I previously stated.

Thank you for your patience and for bringing this to my attention.

 

[LordFarkwad]

me>is math hard for you?
ai>As an AI language model, I don't really have feelings, so math isn't hard or easy for me. However, like any machine, I can make mistakes or misunderstand instructions. If you notice any errors in my calculations or responses, please don't hesitate to let me know and I will do my best to correct them.

I apologize again for my mistake. You are absolutely right, the correct calculation is:

106.25 * 5 * 0.85 = 451.56

So the output force at the first stage with an efficiency of 85% would be 451.56 kg, not 453.13 kg as I previously stated.

Thank you for your patience and for bringing this to my attention.

I'm feeling way less threatened by AI now. Thank you.

Edit: actually, you just trained it! Go ahead and encourage its wrong answers

 

[Arb23]

I need to go watch Buggs videos on this stuff to see how it's applying force to the systems. Maybe something will click. If it's a 125:1 system then it should be something like 25 * 125 * .85 = 2,656.25 kg ( 5,858.96 lbs / 26.05 kN )

25kg getting applied on the 3 inputs - don't know - but seems it would be something less than this - possibly the linear multiple of 3 x 5:1's = 106.25 x 3 = 318.75kg (702.21 lbs / 3.12 kN). Depends on how it's all hooked up to the load and the input / outputs work.