Editing Power take-off (section)

==History==
[[File:International Harvester Cub Tractor (1963).jpg|thumb|Yellow shaft provides PTO drive to a [[flail mower]] on this [[International Harvester]] tractor]]
Various power transmission methods were available before power take-offs became common, but there were applications which would benefit more from some of the attributes that PTOs would provide. [[Belt (mechanical)#Flat belts|Flat belts]] were generally only useful for applications where the engine was stationary, such as factory [[steam engine]]s, [[portable engine|portable stationary engine]]s, or [[traction engine]]s parked in front of the work. For moving vehicles such as a [[traction engine]] or early [[tractor]] towing a [[list of agricultural machinery|farm implement]], the implement could receive rotary power by taking it from one of its own wheels (whose turning was imparted by the towing) and distributing it via roller chains (to a [[mower#Sickle mower|sickle bar]]'s crank, for example), but such a transmission ceases if the vehicle stops traveling, and the workload's resistance tends to make the wheel skid rather than turn, even if [[grouser|cleated]]. The concept of a shaft drive with easily connected and disconnected couplings, and flexibility for driving at changing angles (such as when an articulated tractor-and-trailer combination turns), was a goal to pursue.

Experimental power take-offs were tried as early as 1878, and various homemade versions were constructed over the subsequent decades.<ref name="Spinning">
  {{
    cite journal
      | last1=Quick
      |
first1=Graeme
      |
title=Spinning an historical yarn about power-take-off shafts
      |
journal=Australian Grain
      | publisher=Greenmount Press
      |
date=March–April 2008
      | volume=17
      | issue=6
      | pages=36–37
      | url=https://www.ausgrain.com.au/Back%20Issues/176magrn08/36_Spinning.pdf
      | url-status=dead
      | access-date=2022-07-28 | language=en-au
      | archive-url=https://web.archive.org/web/20210226232835if_/http://ausgrain.com.au/Back%20Issues/176magrn08/36_Spinning.pdf
      | archive-date=2021-02-26
      | archive-format=PDF
      | quote=[From p. 36] The medal for the first recorded power take-off on a piece of mobile machinery on the other hand ought to go to an Aveling and Porter Bell-type reaper.  This steam-powered outfit was put on show at the 1878 Universal Exposition in Paris.
  }}
</ref> 
[[International Harvester]] Company (IHC) was first to market with a PTO on a production tractor, with its model 8-16, introduced in 1918.<ref name="PrippsMorland1993pp37-39">{{Harvnb|Pripps|Morland|1993|pp=37–39}}.</ref> Edward A. Johnston, an IHC engineer, had been impressed by a homemade PTO that he saw in France about a decade before, improvised by a French farmer and mechanic surnamed Gougis.<ref name="PrippsMorland1993pp37-39"/> He and his IHC colleagues incorporated the idea into the 8-16, and designed a family of implements to take advantage of the feature. IHC was not alone in the market for long, as within a year PTOs were appearing on other production tractors, such as some [[Case Corporation|Case]] models. In 1920, IHC offered the PTO option on their 15-30 tractor, and it was the first PTO-equipped tractor to be submitted for a [[Tractor#Nebraska tractor tests|Nebraska tractor test]]. The PTO was a competitive advantage for IHC in the 1920s, and other companies eventually caught up with PTO implementation.

Inside the [[transmission (mechanics)|transmission]], the exact point along the [[gear train]] where the power is taken off determines whether the PTO can be run independently of vehicle travel ([[ground speed]]). Early PTOs were often taken off the main output shaft, meaning that the vehicle had to be "in gear" in order to run the PTO. Later this was improved by so-called live PTO (LPTO) designs, which allow control of the PTO rotation independently of the tractor motion. This is an advantage when the load driven by the PTO requires the tractor motion to slow or stop running to allow the PTO driven equipment to catch up. It also allows operations where the tractor remains parked, such as silo-filling or unloading a [[manure spreader]] to a pile or lagoon rather than across a field. In 1945, [[Cockshutt Plow Company|Cockshutt Farm Equipment Ltd]] of [[Brantford]], Ontario, Canada, introduced the Cockshutt Model 30 tractor with LPTO. Live PTOs eventually became a widespread norm for new equipment; in modern tractors, LPTO is often controlled by push-button or selector switch. This increases safety of operators who need to get close to the PTO shaft.