Farm Hi Lift Jack

©  Brooke Clarke 2011


Background
Executive Summary
Mechanical Advantage
Strap Winch
Farm Jack
    Accessories
Patent
2 Ton Chain Hoist
Related
Links

48" Farm Jack
                Tractor Supply Co. No. 115902 Promo $43.09 out the door
                9/2011 48" Farm Jack
                Tractor Supply Co. No. 115902 Promo $43.09 out the door
                9/2011

Direction lever shown in the Down position.  When lifted so that the notch is engaged it's in the UP position.

Important:  The jack must be loaded with a minimum of 110 lbs. to lower step-by-step, otherwise the lifting nose will drop.


Background

After a second 10' shipping container was delivered and placed three feet from the existing 20' shipping container I wanted to move the empty container so it would be next to the existing container.

Executive Summary

Don't bother getting the Farm (Hi Lift) Jack since they are made too cheaply to survive.  It may be that a more expensive unit would survive, but I doubt it.  The strap Winch is designed to hold down a load and does not have enough mechanical advantage to move a container, so don't bother to get one for that use.

The three items that I recomend are:
An option would be to get a Strap Winch, not to move the container, but to hold the other end so it will not move.

Mechanical Advantage

Many of this type of product have working load ratings.  For example the Strap Winch is rated 3,333 pounds working load limit and 10,000 pounds break strength.  BUT, when using it to lift or pull something the amount of force you can generate depends on the leverage (mechanical advantage) and how strong you are.  Here's a guess at how much force these devices can generate based on an input force of 50, 100 or 200 pounds.
Name
Mech
Adv.
50 #
100 #
200 #
Strap Winch
9:1
450
900
1,800
Farm Jack
44:1 2,200
4,400
8,800
Chain Hoist





Strap Winch

The first attempt was using a strap winch.  There was not enough leverage using the winch, but by using a six foot steel TV mast as a lever on the strap the empty container could be moved a little less than an inch for a lot of expenditure of work.  It would take a month using this method so on to the Farm Jack.
Home Depot p/n 04622  2" x 27' $15.04 out the door.
Home Depot
                  2" x 27' Strap Winch p/n 04622 Home Depot
                  2" x 27' Strap Winch p/n 04622
You can see tht the hand grip (black) is 6-5/8" from the axle.  The highest leverage is when there's only
enough strap on the axle in order to prevent slipage, a radius of 3/4".  The mechanical advantage is about 9 to 1, so a 50 lbs pull on the handle would result in about 450 lbs tension in the strap.

There are 10 notches on the ratchet wheel so the handle travels 4.1" per notch.
There are two ratchet wheels, one on each side of the axle.  There's a handle pawl and a load pawl.
Once there's some tension on the strap the load pawl can not be retracted unless the handle is pulled enough to unload the load pawl.

When starting out pass the strap through the slot in the axle and pull the strap so it's tight.  Then just work the handle and after a half turn or so the strap will bind to the axle and then the handle will tension the strap.
Moving
                  Shipping Container w/ Strap Winch - Single Moving
                  Shipping Container w/ Strap Winch - Double
In this configuration 2 & single strap the force is just what the ratchet can apply.
Not enough to move the empty container.
But when a steel TV mast is used to add tension to the strap the
container moves a little less than in inch.
In this configuration 2 & doubled strap, the force is doubled, but the empty container
still will not move just from the ratchet force.
Now when the TV mast is used it takes less effort to move
the container.
Maybe an extension on the ratchet handle would move the container?
ans:  The release lever is in the way of just using a pry bar.
Also the mast should be pulling only one strap to double it's effectiveness.
Yes, pulling on just one strap doubles the effect.
Container now moved about a foot closer.

Farm Jack

The Farm Jacks I'd seen in the past did not have the top jaw.  For example the jack sold by Harbor Freight (Item # 6530).  So I was supprised to see the ones offered by Home Depot that had the top jaw (Model TR8485 & TR8605).  The local Home depot did not have either of them in stock but I found it at the local Tractor Supply (SKU  0115902) for less than at Home Depot.

Tractor Supply Co. No. 115902
Promo $43.09 out the door 9/2011
Reese 70334 48" Farm Jack

Leverage

The handle is 35-3/4" from it's pivot pin to the end.  The lifting pin is 1" from the pivot pin.  Mechanical advantage about 36:1.
One cycle of lifting raises the jack hand 1/2" and the Handle moves about 22", so the mechanical advantage is about 44:1.
With 100 lbs of force on the handle the jack would lift about 4000 lbs or 2 tons, with 200 lbs on the handle about 4 tons.

Physics of Moving Containers

There are a number of ways of using either the strap winch (see above) or the Farm Jack to move an empty container.
Configuration 1
Shipping
                Container Physics
Configuration 2
Shipping
                Container Physics
Configuration 3
Shipping
                Container Physics
If the jack is used at the top to try and pull
the container, it causes the lower left edge
to dig into the ground.  NOT GOOD.
When a strap is used from the upper left of the full
container to the lower left of the empty container the
forces not only moves the empty container on the right
to the left it also takes weight off the lower left edge.
GOOD.
When the jack is used between the lower right of the full
container and the lower left of the empty container not only
is the empty container moved to the left but also some
weight is taken off the lower left edge.  Good
But the jack top jaw slipps out.
07:29:59
Using Farm Jack
                  to Pull Shipping Containers toghther

Tried this but the top jaw rotated because the small tab broke off.
Farm Jack #2
                  Top Jaw Bad Design
Because of the rotation when you try to clamp the jaw slips off, so it's useless now.

The design problem is that the there's a gap to the right of the I-beam and the top jaw that allows this rotation. This is why you see many of these jacks offered for sale without the top jaw.
07:32:50
Using Farm Jack
                  to Pull Shipping Containers toghther

3' Class III
                  Safety Towing Chain
Looped a 3' Class III Safety Towing Chain through the lower left hole in the empty container and hooked the jack lower jaw in the lower right hole of the full container, configuration 3 (above).
This worked for about 3 cycles then the jack handle broke at it's base because I was not pulling exactly in the plane of the handle motion.

6772488 Wire spring latch safety hook
The nut that holds the top jaw on the jack has loosened and needs to be tightened.  In addition to the lock washer I'll add some weak locktite.
After fixing the top jaw and starting to pull the front toghther, two problems showed up:
1) as the front moves closer the rear seperates. It would be good to use the strap wrench to hold one end as the other end is moved.

2) the flange on one side of the top jaw broke off allowing the top jaw to turn, not good.  You can see crystalized metal at the break, i.e. it's cast metal.  The thing to do is have a new top jaw made of steel instead of a casting.


Farm Jack
                  Failed, Broken Handle
48" Farm
                  Jack Broken Top Jaw
This suggests two imporved jack parts:
1) a stronger top jaw.
2) an improved handle.
3) better retaining method for handle pivot pin
The top clamp can be installed pointing up.  Then the hole in the clamp can be for a hook on some supporting cable.  The long side is flush when in the up position.

I'm going to take this one back and add a new longer bolt to replace the 42mm long x 12mm dia. - 1.75mm pitch bolt so that malleable iron washers can be used on both sides.  Also going to grind the top jaw so it fits properly into the I-beam.  Maybe a 1/2" bolt?


After a lot of filing & grinding interspersed with an application of machinist's blue there's no tendency to climb and the side toward the teeth is now touching the I-beam (before that was a 0.050" gap along that side.
Farm Jack #2
                  after working on Top Jaw


The Top Jow pointing Up.  The jack could be lifted by a crane.  Also a sleeve could pass over the top jaw,, like shown in the Pole Setting device patent.

As received the top jaw would not fit because the "tabs" were too big.
48" Farm
                  Jack with Top Jaw Pointing Up


Accessories


Bumper Lift Kit

A short chain goes from the lower jaw to a hook that grabe an old fashioned bumper.

Spart Tire Mount

 Instead of carrying a spare tire on a SUV you can carry a farm jack.

Jack Handle Isolator

 -The rubber  isolator slips over the top of the jack (top jaw must be pointing up) the strap just holds them toghter to stop noise when jack is on vehicle.

Jack Handle Strap

Ties the handle to the I-beam to stop rattle.

Mag Wheel Lift Kit

Two straps with hooks on end attached to lower jaw to lift vehicle using wheel spokes.

Roof Mount Kit

Off Road Base Plate

Rear Door Mount

Rugged Ridge sells some accessories for the farm jack for off roading recovery use
Extreme Limits Off Road has a number of accessories

Patent

Some of the unique features of this jack are that the main support column is fixed to the base and there's a single mechanism that climbs or descends the main column.
There is provision to prevent getting the jack jammed when using it in the clamping mode.  i.e. there's a rod that senses that the base is close and stops the downward force.
Using holes in the main (I-beam) column instead of gear teeth is a lower cost way to get the step-by-step action and it's symmetrical.1410380
Class Numbers

74 Machine Element or Mechanism
254 Implements or Apparatuw for Applying Pushing or Pulling Force

1410380 Pole Setting Device, R.R. Daniels, Mar 21 1922, 254/133.00R (Special Engaging Elements) - has holes in main column
patent 1410380 Pole
          Setting Device, R.R. Daniels, Mar 21 1922

Harbor Freight 2 Ton Chain Hoist (p/n 631)

Wouldn't you know, the distance from the top left of the full container to the lower left of the empty container (after using the Class III trailer safety chain) is a few inches to far for the chain hoist to reach.  Tomorrow I'll get another safety chain.

The mechanican advanatge is very large.  I'll measure it shortly.
721968 Hoist, L.D. Round, Mar 3, 1903

Chain Hoist
                Patent 1903
L.D. Round Chain Hoist patent 721968
              1903
Harbor Freight 2 Ton Chian Hoist p/n: 631
The chain hoist can lift up the container.
2 Ton Chain Hoist
                Lifting one end of empty shipping container
Note: the force of the chain (see Configurations above)
is primarily up with a small force pulling the container to
the left.  But pushing the right side of the container will
not budge it at all.  This suggests that there's an optimum
angle that will have enough lift and also enough sideways
force to move the container.
The tare weight is 5,300 pounds.
Tow Chain with Grab Hooks 5/16" x 20' Grade 70 Yellow Zinc
Home Depot Model # 00422   Store SKU # 529425

20' Log Chain at upper left          3' Class III towing safety chain upper right
2 Ton Chain
                Hoist to pull shipping containers toghther
The log chain has hooks on both ends that are designed to
hook onto the chain.  You can also buy another hook that
can be inserted into any link.  This should allow getting any
desired angle of pull.
More shallow angle on chain.
2 Ton Chain Hoist
                to pull shipping containers toghther
1/4" Grab Hook added to Tow Chain
Home Depot Model # CH8001-6  Store SKU # 566678
1/4"
              Grab Hook added to Log Chain
Note the hook is installed at the end of a link.  It will not fit in the center of a link.
5/16" Grab Hook
5/16"
              Chain Grab Hook
5/16" Support (SUP) Hook
5/16"
              Chain Support (SUP) Hook
5/16"' Chain Grab Hook Fitted to 5/16" Tow Chain
5/16"'
              Chain Grab Hook Fitted to 5/16" Tow Chain


Related

Active Storage - shelving, boxes and shipping containers
Air Tools
Measuring Tools - length, weight
8" Mini Shear Break
12" Bench Shear
Lathes for less than 1" OD parts
Mini Machine Tools

Links

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page created 30 Sep 2011.