{{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.
:* refers to implement end; tractor end not specified
=Approaches=
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
=Attachments=
PXL 20210531 000317977.jpg|Planter
* 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]