The Power Of Friction

[Maine farmer]

Attaching a picture of a used wear band from the blower on a forage harvester.  The picture shows what happens to hardened steel after about 20 thousand tons (U.S) of hay is accelerated over it.  The blower throws the chopped hay into a wagon.  It can throw the feed a distance of 60 ft.

 

The wear band was originally 3/16 of an inch thick.  We just replaced it today.  

 

I just found it interesting, and I am sure there is a good high school level physics word problem in there somewhere.

[Cascabel]

Just make it thicker, it will last longer.

[Maine farmer]

Just make it thicker, it will last longer.

Yes, it would, but I would have to make it myself, and I could buy an exact replacement off the shelf and have the harvester up and running in a few hours.  I think the manufacturer's engineers figured the most profitable life of the parts.

 

In my youth, we could afford to replace a harvester every 5 years, and hardly had to replace any parts. We have had this harvester for 8 years.  Fortunately the engineers at New Holland were thoughtful enough to design this machine to be easy to service and repair.  

[exchemist]

Attaching a picture of a used wear band from the blower on a forage harvester.  The picture shows what happens to hardened steel after about 20 thousand tons (U.S) of hay is accelerated over it.  The blower throws the chopped hay into a wagon.  It can throw the feed a distance of 60 ft.

 

The wear band was originally 3/16 of an inch thick.  We just replaced it today.  

 

I just found it interesting, and I am sure there is a good high school level physics word problem in there somewhere._20160616_150824.JPG

Just for the sake of a bit of discussion, I actually think this is an illustration of wear and not friction, strictly speaking. The distinction is one I am more than normally conscious of, as I spent most of my career in the lubricants business. We always used to say that the primary job of a lubricant is to prevent wear, as that is what leads to short component life and machinery breakdown, whereas friction is just resistance to motion, which creates energy consumption but, in itself, nothing more. :) 

[Maine farmer]

Just for the sake of a bit of discussion, I actually think this is an illustration of wear and not friction, strictly speaking. The distinction is one I am more than normally conscious of, as I spent most of my career in the lubricants business. We always used to say that the primary job of a lubricant is to prevent wear, as that is what leads to short component life and machinery breakdown, whereas friction is just resistance to motion, which creates energy consumption but, in itself, nothing more. :)

Hmm, interesting, but isn't the wear caused by the energy generated by the resistance to motion?  Isn't it the energy loss due to friction that causes the wear? 

 

It would be an interesting exercise to calculate the energy used in wearing the part, don't you think?  We actually noticed the wear when the harvester began to draw more power from the tractor, as the part is  in an a location where you can't actually see it. 

Edited June 20, 2016 by Farming guy

[GAHD]

...that looks more like it got nailed by rock than by hay. You have high silica soil and/or running blades real close to ground?

[Maine farmer]

Our disc mower is set at it's maximum cutting height with the blades spinning nearly parallel to the ground.  We do, however, find the occasional new woodchuck mound of sand and gravel.  Unless we are drowsy and or operating the equipment too fast, we are able to lift the pickup head of the harvester in time to avoid any significant damage.

 

We have had our mower for over ten years, and had to replace all of the discs that hold the knives due to wear.  The tops of the discs develop holes just behind the point where the knives are mounted.  I have tried welding those, but they get paper thin and difficult to weld.  Also the bolts that hold the blades have guards made of cast iron  to protect the nuts, and they have all worn away to the point that they were not protecting anything and had to be replaced.

 

The parts on these pieces of machinery spin at 1,000 rpm

[OceanBreeze]

Doesn't look like normal wear to be. My guess is the wear band was vibrating and flexing at a high rate, probably in sync with the rotary machinery at 1,000 rpm. Then it started to crack and finally started to come apart.

 

Don't know what you use the hay for, if cattle feed, those cows will get an iron-enriched diet!

Edited November 16, 2016 by OceanBreeze

[Maine farmer]

Doesn't look like normal wear to be. My guess is the wear band was vibrating and flexing at a high rate, probably in sync with the rotary machinery at 1,000 rpm. Then it started to crack and finally started to come apart.

 

Don't know what you use the hay for, if cattle feed, those cows will get an iron-enriched diet!

I should have posted a side view of the damage.  The steel was worn very thin before failure, although I do agree there would have been a lot of vibrating and flexing, and metal fatigue.

 

Spent a few hours today replacing auger flighting on our vertical feed mixer.  The new part is more than 1/4 inch thick, and the worn part was thin enough to make a nice slice in my hand when I touched it.  That wear took about 15 years of daily use to happen.  

 

As for the iron in the diet, we feed dairy cattle, and we have our forage analyzed in a lab on a regular basis, and a magnet on the feed discharge chute to catch any troublesome loose pieces