Why 540?

mcfarmall · Dec 28, 2018

Why not 500 or 632 or whatever?

There must be some mechanical basis for standardizing on 540 rpm for PTO speed.

Let's light it up, tractor gurus!

Norm W · Dec 28, 2018

Many of the old engines (open fly wheel) ran at 550 no load, 540 under load. I think it is just a carry over from the flat belt days.

CalG · Dec 28, 2018

A close enough factor of electric motor rpm based on 60 cycle electrical systems.

joeu235 · Dec 28, 2018

Tractors were designed by folks who had a Base 9 number system.

mcfarmall · Dec 28, 2018

Norm W said:
Many of the old engines (open fly wheel) ran at 550 no load, 540 under load. I think it is just a carry over from the flat belt days.

You mean like the hit and miss types, oilfield engines, etc.?

kthompson · Dec 28, 2018

Just wondering, in today's world some very good rpm meters but how did they know it was 540 that many years ago?

Motorboatin · Dec 28, 2018

From Wiki.......“The first industry standard for PTO design was adopted by ASAE (the 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.”

Power take-off - Wikipedia

RickB · Dec 28, 2018

CalG said:
A close enough factor of electric motor rpm based on 60 cycle electrical systems.

I can’t recall any electric motors running at 540 rpm.

Wagtail · Dec 29, 2018

Motorboatin said:
From Wiki.......“The first industry standard for PTO design was adopted by ASAE (the 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.”

Power take-off - Wikipedia

Well, there ya go. Learnt something today.

= no matter what, the day wasn't wasted.

mcfarmall · Dec 29, 2018

Motorboatin said:
From Wiki.......“The first industry standard for PTO design was adopted by ASAE (the 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.”

Power take-off - Wikipedia

So the question still stands...Why 540? Why did the ASAE in April of 1927 decide that the PTO rotational speed was to be 536 +/- 10 rpm?

I don't understand the 60 cycle electric motor explanation...the common speeds for AC motors are 1725 and 3450 rpm.

I believe the early engine speed comment has merit and could be a good starting point for the ASAE logic.