Five Hundred And Forty Revolutions Per Minute

Something I have always wondered. Who decided that 540 r.p.m. should be the standard tractor P.T.O. speed? Why not 500 or even 600? 540 seems such an arbitrary number to come up with. It would be interesting to know the history behind it.

History source--- Wikipedia

Experimental power take-offs were tried as early as 1878, but International Harvester Company (IHC) was first (in 1918) to install a PTO on a production tractor. In 1920, IHC offered this option on their 15-30 tractor, and it was the first pto-equipped tractor to be submitted for a Nebraska Test. The first PTO standard was adopted by ASAE (American Society of Agricultural Engineers) in April 1927. The PTO rotational speed was specified as 536 ± 10 rpm; The direction was clockwise. The speed was later changed to 540 RPM.[3]

In 1945, Cockshutt Farm Equipment Ltd. of Brantford, Ontario, Canada, introduced the Cockshutt Model 30 tractor with Live Power Take Off (LPTO). LPTO allows control of the PTO rotation independently of the tractor motion. This was an advantage when the load driven by the PTO required the tractor motion to slow or stop running to allow the PTO driven equipment to catch up. 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.[4]
[edit] Technical standardization

Agricultural PTOs are standardized in dimensions and speed. The ISO standard for PTOs is ISO 500, which as of the 2004 edition was split into three parts ISO 500-1 (General specifications, safety requirements, dimensions for master shield and clearance zone), ISO 500-2 (Narrow-track tractors, dimensions for master shield and clearance zone), and ISO 500-3 (Main PTO dimensions and spline dimensions, location of PTO). The original type calls for operation at 540 revolutions per minute (RPM). A shaft that rotates at 540 rpm has 6 splines on it, and a diameter of 1⅜". Two newer types, supporting higher power applications, operate at 1000 RPM and differ in shaft size. The larger shaft has 20 splines (1¾" diameter), while the smaller has 21 (1⅜" diameter). All three types rotate counterclockwise when viewed from the tractor. A 10 spline type was used with some early equipment such as the 1948 Land Rover, a six spline adapter was usually supplied. It is customary for agricultural machines manufacturers to provide the nominal PTO power specification, an indication of the available instantaneous power at the shaft.

Not just our first names that are the same, we both have the same sense of curiosity!

"Pto shaft speed must suit the needs of implements (initially grain binders), but should the pto speed be linked to speed of the engine or the tractor drive wheels? Experience in rice states, where the 1925 crop was heavy and traction was poor, demonstrated advantages of linking pto speed to engine speed. Grain binders could run at full speed while the travel speed was reduced to accommodate the heavy crop. The fastest shaft on binders (the pitman drive) ran at 500 to 600 rpm at normal travel speeds.

The 1926 draft standard was adopted by ASAE in April 1927. The pto rotational speed was specified as 536 � 10 rpm; W.L. Zink reported that this speed "seems to work out satisfactorily for all installations known." Thus, it is likely that the choice was a compromise related to the needs of early pto-driven machines.

Acceptance took time. A 1929 study of 35 popular tractors showed pto speeds ranging from 515 to 745 rpm with an average of 549 rpm. Through numerous revisions, the pto speed stayed at 536 rpm as late as 1948. By 1958, when a new 1,000 rpm pto standard was developed, the 536 rpm standard speed had been changed to 540 - 10 rpm. Probably, the speed was simply rounded up to a more convenient value "

Another interesting value you bring up is "Pittman drive" earlier horse drawn (ground driven) vs. powered tractor. earlier equipment wasn't to be operated faster than a horse / mule could walk. wondering how they come up with that RPM



By the way ya only got it half right -- My name is Jim Glad to meet you. -- to eliminate confusion I only use part of my middle name,-- the Old is just plain fact. --- LOL

Nice to meet you too Jim. It reminds me that Europe, Argentina, United States, Canada, China, Korea, Australia, Middle East, North Africa, Mexico, Cuba, Panama, Venezuela, Peru, Uruguay and Philippines. Also high-speed lines in Japan and Spain(approx. 60% of the world's railways) use 4 feet 8 and one half inches as the standard distance between the two lines of a railroad track. I wonder how they decided on that peculiar measurement!

From the Roman cart wheel track. That was the std width of their gravel on their roads.

4' 8 1/2" supposedly is the wheel gage of the Roman Chariots and was carried down through the years. joe-

(quoted from post at 11:23:55 09/15/10) Nice to meet you too Jim. It reminds me that Europe, Argentina, United States, Canada, China, Korea, Australia, Middle East, North Africa, Mexico, Cuba, Panama, Venezuela, Peru, Uruguay and Philippines. Also high-speed lines in Japan and Spain(approx. 60% of the world's railways) use 4 feet 8 and one half inches as the standard distance between the two lines of a railroad track. I wonder how they decided on that peculiar measurement!

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I have heard the width came from Roman Charit wheels, then to wagon wheels using the "same"axels. These wagon wheel were replaced with rail wheels for the first rail trollys.
Dennis

The first shaft-drive PTO used in farm equipment that was indeed for sale to the public was demonstrated in France in 1878. This was a steam-powered live PTO. The IH thing is about mass production and tractors with serial numbers.

In the USA, George Berry invented and sold a combine with a live steam-powered PTO, in 1883.

As to Cockshut and their live PTO tractor in 1945? I'm not sure where that came from, but . . . two guys in Ohio invented the dual-clutch, live PTO for farm tractors in 1940. They described their dual-clutch setup as "independent" and "continuous." At that time, they sold the rights to Huber Mfg. What Huber did with it, I do not know.

The first shaft-drive PTO used in farm equipment that was indeed for sale to the public was demonstrated in France in 1878. This was a steam-powered live PTO. The IH thing is about mass production and tractors with serial numbers.

In the USA, George Berry invented and sold a combine with a live steam-powered PTO, in 1883.

As to Cockshut and their live PTO tractor in 1945? I'm not sure where that came from, but . . . two guys in Ohio invented the dual-clutch, live PTO for farm tractors in 1940. They described their dual-clutch setup as "independent" and "continuous." At that time, they sold the rights to Huber Mfg. What Huber did with it, I do not know.

Probably just happened that the gearing in the inventor's setup resulted in 536 RPM, and it seemed to work. Of course, any speed in that area would "work", because you design the implement to whatever the standard is.

More curious to me is baseball- and the 90 foot base path distance, and 60' pitching distance. Both also "work"- runners are usually "out" by less than a step on a routine grounder. But when someone speedy like Ichiro of the Seattle Mariners comes along, he beats out a significant number of infield hits by being just a step or two faster. And base stealing also usually results in close plays. And breaking balls pitched make their break just before getting to the hitter, thereby fooling him.

When my daughter played 10 year old softball, her team had a devastating pitcher- nobody could hit her. Nobody intentionally threw breaking balls yet- they were still working on speed and control. Batters always stood at the back of the batters box, to get the most time possible to swing.

Opposing coach was watching each of his girls strike out, swinging just over the ball. He called time, went out and moved his batter to the front of the box. She didn't want to, but he insisted. She got a hit. From then on, everybody got a hit; it seems that the pitches were "breaking" slightly downward, and by moving the batter forward, she was getting the ball before it broke. That was pretty much the end of Brittany's pitching career.

Here's where we get into the "Live" PTO vs "Independent" PTO discussion AGAIN! My understanding is that Cockshutt was first with the truely independent PTO (not 2 stage clutch or clutch beyond transmission). Please correct me if I'm wrong!
Dave

No hard evidence to cite (yet...I'm still looking) but IIRC, the reasoning behind pto rpms ending up @ 540 aren't nearly as complicated as some replies indicate.

What I remember hearing was, first tractor equipped with pto had an engine operating speed of around 1600rpm. Pto final gearing was arbitrarily decided to be 1/3rd of engine speed.

"It just happened to work out that way".

540rpm was closest "even number" to first workable pto's speed, hence 540 was settled upon as industry standard.

It does not say why 540 but according to the American Society of Agriculture Engineers, ASAE Standard.
The the rear pto was "Originally developed in 1926 by a conference of engineers representing tractor manufacturers; adopted by ASAE April 1927; revised July 1928" along with revisions in 1931, 1941, 1952, 1958, 1961, 1964, 1966, 1967, 1968, 1969,1973 and 1974. It does not state what the revisions were. I believe the early years were the size of the pto shafts.

In 1976 the 540 and 1000 RPM PTO's were combined into ASAE S204.6.

If someone could come up with a copy of the 1927 ASAE Standards it might have the exact information. Mine is the 1998 edition.

Same thing happened in a little league allstar baseball game when I was a kid.

The opposing pitcher had a slow pitch that "broke" just over the plate.

The best hitters on our team were striking out.

Me batting 9th and last in the lineup gave my dad time to figure out what to do.

He came down from the stands between innings and told me to stand as far forward as possible in the batters box.

Don't remember which pitch I "pulled", but it sailed over the left field fence.

Poor kid pitching had never given up a home run and starting crying out on the mound.

Although we didn't win the game, my dad bought me some new clothes the next day.

This was discussed on another site a few years ago. I've got the ASAE article somewhere, would need to look a little. I think it has some relationship to pulley belt speed.

You had to hit a home run to get new clothes?! And I thought we was po'!




Just kidding.

Christopher

Susan's team had another good pitcher, who was asked to give an intentional walk at one point. She couldn't believe it- "You want me to do WHAT?" She finally did it, glaring at the coach the whole time. And it completely blew her concentration- couldn't throw another strike to save her life. Coach finally took her out after she walked in a run- girl and her folks were furious.

Coach decided maybe that strategy was a little too advanced for the age group he was working with.

According to my 86 year old father-in-law, the only speed a tractor is supposed to be operated is slow idle. In fact, until I freed it up, the throttle lever on his CaseIH 540? diesel was frozen in that position. Anything faster is "too fast and will hurt the engine".

You'd have to define "truly independent" to attempt to answer. The Cockshut PTO had to rely on the tractor engine for power, so it's not really "independent" by the common use of the word.

George Berry built combines in 1883 (in California) that used one common steam boiler, one large steam engine for wheel drive, and one small steam engine for the "independent" PTO.
There were similar versions in France also in the 1800s.
I suspect, going by your use of the phrase, they were just as "independent" as the design used in the Cockshut.
The use of the word "independent power shaft" showed up in early farm tractor patents for many PTOs, as long at they could be run "independent" of the wheel drive. Use of the word did not just apply to the type you mention.

540 is divesable by 60,the amount of seconds in a min.Back then everything went by the minute.eg 540 rounds per minute.Maybe thats how they came up with the number.It would never work for it to be 540.236 R.P.M.Feet and inches are not easaly divisable to desimals and until calculaters were in production,nobody cared.

The 540 rpm was the speed of the pto on the IHC 10-20 and it sort of set the standard. As and earlier respondent pointed out IHC was the first to provide a pto as an option. However, the 10-20, 15-30 and later standard tractors used a threaded pto shaft. The Farmall (later known as the Regular) was the first to use the 1-3/8" splined shaft. If one looks at harvester etc. parts books in the 1930s and early 1940s there are an enormous variety of shaft positions, shaft speeds and shaft types and al;l sorts of pto couplings were required for the different tractors. Similar chaos held in the shaft shielding. The 1927 (1928) standard was the first attempt but the 1938 American Society of Agricultural Engineers standard put things into a semblance of order. They still left two shaft sizes, 1-3/8" for the smaller tractors and 1-3/4" for the larger tractors. Still lots of choices on couplings. IH in about 1943 standardized all their pto shafts to the 1-3/4" to simplify farmers life.

In my earlier response, please read 1-1/8" for the small shaft and 1-3/8" for the larger shaft (NOT 1-3/8" and 1-3/4"). The 10-20 had a 1" dia. left hand screw thread. The F-20 pto ran at 505 rpm.

I'd rather know why there are 10 wieners and only 8 buns in the packages.........

(quoted from post at 11:05:07 09/16/10) I'd rather know why there are 10 wieners and only 8 buns in the packages.........

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Dude, at Sams Club it used to cost more for the bun than the hot dog in big packs. Crazy world.