Chain speed calculation discrepancy and PPE - Help me understand

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

CFar45

ArboristSite Lurker
Joined
Jan 1, 2022
Messages
12
Reaction score
15
Location
NY USA
When looking at PPE (ie. chaps/pants/boots), chain speed is often used as a reference in determining the effectiveness of protective equipment. However, I’ve noticed some discrepancy in chain speed calculations between manufacturer, safety organizations (ISO) and my own calculations.

For example:
From Stihl ms400 manual:
ISO max chain speed = 28.9m/s
Chain speed at maximum power (according to Stihl, I assume) = 21.7 m/s.
E0066C1B-C27A-468E-84F3-7C5663BB973D.jpeg

Why the (significant) discrepancy between ISO calculation and Stihl calculation? What am I missing?

To further confuse the issue, when I plug the numbers (3/8 pitch, 7 tooth, 14000 max RPM) into the formula on Madsens, I get 31.12 m/s. (Converted to m/s using online calculator)

Just trying to understand as I assess PPE.

I understand that my leg doesn’t know the difference between 21 m/s and 31 m/s and the damage is going to be the same for practical purposes if chain meets unprotected body part.

I also understand that in general, the more robust the PPE, the better. But PPE manufacturers use chain speed as a reference to help the consumer determine appropriate level of protection…. for example, class 1 vs class 2 vs class 3 chainsaw boots….

So I’d like to better understand why Stihl says 22 m/s and ISO says 29 m/s.

Thanks in advance to those here who are smarter than me!
 
Not a matter of smarts, a chainsaw does not make its maximum power at its highest rpm. I don't know how ISO measures things, but if you take it at face value - a chainsaw's maximum speed is much higher than it is at maximum power. I understand that it is not usual for a 12,000+ rpm saw to make its maximum power at 9,500 rpm.

As stated above, your question will likely see more action in the chainsaw forum.

Ron
 

Latest posts

Back
Top