{{Projects infobox
|image           = Three-point-hitch.scad.png
|designers       = [[User:Tim|Timothy Schmidt]]
|date            = 2021
|vitamins        = 
|materials       = 
|transformations = 
|lifecycles      = 
|tools           = 
|parts           = [[Frames]], [[Nuts]], [[Bolts]], [[End caps]], [[Plates]]
|techniques      = [[Tri joints]], [[Space frames]], [[Trusses]], [[Bolting]]
|files           = 
|suppliers       = 
|git             = 
}}

[[Category:Projects]]
[[Category:Agriculture]]

=Introduction=
The three-point hitch is a widely used type of hitch for attaching [[Ploughs|ploughs]] and other implements to an agricultural or industrial [[Tractors|tractor]]. The three points resemble either a triangle, or the letter A. Three-point attachment is the simplest and the only statically determinate way of joining two bodies in engineering. 

=Challenges=
How to match industry standard sizes using as few [[:Category:Parts|parts]] and [[vitamins]] as possible.

======Size categories======
There are five different hitch sizes, called categories.  The higher category hitches have sturdier lift arms and larger connector pins.

{| class="wikitable" border="1"
|-
! style="text-align: left; padding-left: 1em; padding-right: 1em;" | Category
! style="text-align: left; padding-left: 1em; padding-right: 3em;" | Tractor power
! style="text-align: left; padding-left: 1em; padding-right: 3em;" | Top link pin diameter*
! style="text-align: left; padding-left: 1em; padding-right: 3em;" | Lift arm pin diameter
! style="text-align: left; padding-left: 1em; padding-right: 3em;" | Lower hitch spacing
|-
| style="text-align: center;" | 0
| style="padding-left: 1em;" | Up to 20hp
| style="padding-left: 1em;" | 5/8 in
| style="padding-left: 1em;" | 5/8 in
| style="padding-left: 1em;" | 20 in
|-
| style="text-align: center;" | 1
| style="padding-left: 1em;" | 20 to 45hp
| style="padding-left: 1em;" | 3/4 in
| style="padding-left: 1em;" | 7/8 in
| style="padding-left: 1em;" | 28 in
|-
| style="text-align: center;" | 2
| style="padding-left: 1em;" | 40 to 100hp
| style="padding-left: 1em;" | 1 in
| style="padding-left: 1em;" | 1+1/8 in
| style="padding-left: 1em;" | 34 in
|-
| style="text-align: center;" | 3
| style="padding-left: 1em;" | 80 to 225hp
| style="padding-left: 1em;" | 1+1/4 in
| style="padding-left: 1em;" | 1+7/16 in
| style="padding-left: 1em;" | 40 in
|-
| style="text-align: center;" | 4
| style="padding-left: 1em;" | More than 180hp
| style="padding-left: 1em;" | 1+3/4 in
| style="padding-left: 1em;" | 2 in
| style="padding-left: 1em;" | 48 in
|}
There are also variants to the above categories denoted by N, (narrow). These utilize the pin sizes of the listed category, but the width of a category one step lower. The N variations are common in "quick hitches" and allow larger tractors to easily hook onto smaller utility implements.

:<nowiki>*</nowiki> refers to implement end; tractor end not specified

=Approaches=
<gallery>
File:Plate-three-point-hitch.scad.png|Plate adapts to 5/8 inch, 3/4 inch, 7/8 inch pins for category 0 and 1
Three-point-hitch.scad.png|Category 0 hitch
Three-point-hitch-category1.scad.png|Category 1 hitch
</gallery>

=Attachments=
<gallery>
PXL 20210531 000317977.jpg|Planter
</gallery>
  * Backhoes
  * Cement mixers
  * PTO stump grinders
  * Trenchers
  * Scoop pans
  * Wood chippers
  * Post drivers
  * Chain harrows
  * Cultipackers
  * Land levelers
  * Soil pulverizers
  * Cultivators
  * Subsoilers
  * Harley rakes
  * Finishing mowers
  * Flail mowers
  * Sickle bar mowers
  * PTO fertilizer spreader
  * Pine needle rakes
  * Sprayers
  * Straw blowers
  * Seed planters
  * Potato plows
  * Booms
  * Carry alls
  * Sweepers

=References=
  * [[https://en.wikipedia.org/wiki/Three-point_hitch|Wikipedia: Three-point hitch]]
  * [[https://wiki.opensourceecology.org/wiki/Bobcat_Standard_Quick_Attach|OpenSourceEcology: Bobcat Standard Quick Attach]]