This is a very old design bale spike, copied from one to fit a grey ferguson which has been adapted for modern tractors. its advantages include support for liftarms which catch and release their balls, and an excellent cock upwards when the lift arms are raised. the feet at each side do not dig into the soil on modern tractors but offer a help in hooking up by reducing manual lift height.
most commercial bale spikes use a single spike which has the disadvantage of causing the bale to rotate to find its lowest center of gravity. The bale often falls apart due to the pressure on one place. they tend to cut corners on iron and so the top link is too low which causes the spikes to be self levelling or worse, hang down when the arms are risen.
you'll find that you can make this for less than the price of a commercial spike and have a better quality implement.
The picture above is of incorrect dimensions which cause the frame to come in contact with the ball latch on the left liftarm. I corrected it on the right arm, however the dimensions are corrected in the plans, so you will not run into this problem. I added height to the top hole as modern tractors seem to have different 3 point linkage geometry to vintage tractors. it is still backward compatible with older tractors though.
9 inch angle grinder, 3/4 hp drill press, arc welder and safety gear capable of burning 3.2mm rods( i used 4.0), sockets or a wrench to tighten both tines. measuring tape.
Step 1: Bill of Materials
2x 50mm bushings
51mm cobalt hole saw, 50mm may do if you install the bushings with a hammer, I haven't tried it.
26mm cobalt hole saw, or larger if you want to use pins that fit your tractor perfectly. I used a 25mm hole saw and the standard pins all jammed.
2x 4ft teeth, 3 1/2 ft minimum
5 feet of 4 inch wide channel iron, or a metric equivalent no wider than the bushings. You can use a box here instead but channel is cheaper.
18 feet of 20mm thick 4 inch wide plate.
Step 2: Dimensions
a: 2 3/4"
d: 27 1/2" channel box length
the centres of each bushing hole in box d are 24 inches apart.
bushings should be located an equal distance from each end of the box,
and from the axis of the box, i.e. 2 inches from each side.
the top and bottom 26mm top link hole centers in plate e are 13 1/2 inches apart
the top lift arm hole center is 31 inches from the end of plate e.
the top and bottom lift arm hole centers in b and c are 6 1/4 inches apart
The bottom holes in b and c are 5 1/2 inches from the end of the plate.
lift arm plates should be welded so that the holes are equidistant from the channel box, i.e the edge of the hole will be 5/8 inch from the channel.
Step 3: Construction
First cut the channel into 2x 27 1/2" lengths, face them edge to edge and weld them into a box on two opposite sides. Find the center of length of the box and measure out each end from the center on one unwelded side for 12". mark and drill two pilot holes.
Drill two 51mm holes over the pilot holes, stop often to lubricate the process with any lubricating oil. When you have the holes made, raise the table on the drill to continue the hole downwards. once the pilot hole is marked inside the box, drill it out with a pilot hole bit. turn the box over and drill both 51mm holes from the other side.
Weld in both bushings in the same orientation, taking care not to weld inside the bushings.
Now, cut off 2 lengths of plate of length b, 2 lengths of plate of length c, 2 lengths of plate of length e. When you have one of each marked and drilled, lay each over its partner and drill through, this will ensure the pins line up. Before you drill through each plate with the hole saw, drill a pilot hole. Drill the 26mm hole halfways from each side.
When all the holes are drilled weld it all together. put snug pins in the holes before welding to ensure the pins will fit after welding. the unlabelled stay plates on the diagram will be of uncertain length, just ensure they each contact c and b and e, you can cut off the overhang after they are welded in place. The entire design is in a two dimensional plane, there is no need to move the top link attachment point any closer to the tractor, you may damage the cab if you do so. If you want to make welding easier you can bevel the ends of many plate lengths to aid forming a fillet weld. It's not necessary with a high powered welder however.