Grading PT-425 and Beehives

[woodlandfarms]

Cmon JJ. This is the moment you pull out the slide rule and impress all of us with the Math I know you know

There is a leverage equation and I think some the smartest guys in this forum own pt's. I saddly am not one of them.

 

[J_J]

About the only thing I know about a fulcrum, is that if the same weight is on each end with the pivot point in the center, you have a balance.

You would have to know the weight behind the front spindles of the machine for one thing. Some of you have found that point by doing the PT pucker.

There is no quick answer, because then you have to know the weight of the metal fwd of the spindles, plus the weight you are trying to lift.

 

[cqaigy2]

I donno, but seems if one measured from where the front tires meet the ground to the 'pins' that's around 800lbs.

Next?

 

[SpringHollow]

I can not find it but I calculated it once for my tractor. I used a spring scale for cranes and a tie down point. Measured the force or weight needed at two different distances on the boom to make the tractor pucker. A ratcheting load binder works well for this.

w1 = weight one
d1 = distance one
w2, d2 for two
PD = weight x distance for tractor
d = unknown distance from fulcrum point to the hitch

All distances measured horizontally

Eq #1 PD = w1 x (d + d1)
Eq #2 PD = w2 x (d + d2)

expanding Eq #1, PD = w1 x d + w1 x d1
substituting for PD in Eq #2 and expanding, w1 x d + w1 x d1 = w2 x d + w2 x d2
Rearranging: w1xd - w2 x d = w2 x d2 - w1 x d1
(w1 - w2) x d = (w2 x d2 - w1 x d1)

d = (w2 x d2 - w1 x d1) / (w1-w2)

d is the only unknown in that equation so you can calculate it.

Then you can plug it into Eq #1 to solve for PD

Then in the future, the weight w3 that makes the PT pucker at distance at distance d3 is:

w3 = PD/(d + d3)

Changing implements can change the geometry and dead weight which was ignored in my calculations for simplicity since it has an effect that is less than 10% for my boom.

More than you ever wanted to know. I do not think i made any major mistakes in those calculations. Now if i could only find my data.

Ken

 

[Gravy]

OWWWW!

That just makes my head hurt.

I do the caveman approach. If I can lift it, and I can steer, and nothing breaks, life is good. If something breaks, that's why I have a welder. Life is good.

(I'm being silly. Don't try this at home, kids!)

 

[SpringHollow]

The main reason to do the calculations is if you want to start lifting something a long distance from the tractor such as making a truss lift. Nice to know if you can do it before you make it.

I showed the derivation but all you need to know is:

w1 = weight one
d1 = distance one
w2, d2 for two
PD = weight x distance for tractor
d = unknown distance from fulcrum point to the hitch

All distances measured horizontally

d = (w2 x d2 - w1 x d1) / (w1-w2)

PD = w1 x (d + d1)

w3 = PD/(d + d3)


You can even skip the first two equations by plugging them into the 3rd equation but it gets very messy. Much easier to just plug in the values in those two equations and then use the calculated result in the 3rd.

Ken

 

[lfbaumgart]

Ken, I need a diagram to interpret your equations, plus you never took into account the effect of adding counter balance such as having a gullible friend or mother-in-law sit on the engine compartment.

 

[MossRoad]

Anyone know the lifting capacity of the boom pole?

About 5 pounds less than you think.

PT pucker alert! :laughing:

 

[J_J]

Does anyone know the weight on any of the PT's behind the front wheel axle?

The wheel axle is the fulcrum point.

Go ahead and assume the weight behind the pins is 850 lbs, and then compute the lifting point in front of the wheel axle to lift 400 lbs.

Show us how on paper.

or

use a set distance and compute the weight the machine can lift. 2ft, 4ft, 6ft, 8ft.

 

[SpringHollow]

As requested, here is a crude diagram:



JJ - if you measure the weight and distance that cause a PT pucker at two different points, then you can calculate for any other points.

You can use a plastic barrel on a chain and add known amounts of water until it puckers.

Ken