A belly full of steel: "chain shot" slide show

[Oregon Engineer]

The Workmen's Compensation Board of British Columbia has put out an excellent slide show on the circumstances that lead upto a serious chain shot injury. The slide show also discusses ways to minimize the risk of a chain shot. Check it out and see what hit a guy in the belly.

http://www.healthandsafetycentre.org/enews/050516/fse2.htm

 

[P_woozel]

Wow, I'vw worked with a processor before following with them doing oversize, always wondered about the chain snapping. Blew thru a 1/2" poly window, scary. :umpkin:

 

[darkstar]

nasty .... has anyone here been cut by a chain saw when the chain breaks ...i had one slap my leg once but only got a scratch ...

 

[MasterBlaster]

Wow. That was a good presentation.

 

[ehp]

Yes I have been cut when a chain broke on a racesaw, lots of people have been cut with chains breaking, coming off ********, and yes I was wearing cutting pants

 

[Xtra]

Last week I was using the top of the bar and up-cutting a wedge on a stalk about chest level with my 460, 32" bar & new chain. The chain jumped off the bar. It got wedged by the chain catcher, but the chain wipped around and caught me right between the legs. I was afraid to even look down it felt like I was kicked. Only damage was some scuffing to my double front carhardts. Now that was a scare!

 

[Stumper]

Last week I was using the top of the bar and up-cutting a wedge on a stalk about chest level with my 460, 32" bar & new chain. The chain jumped off the bar. It got wedged by the chain catcher, but the chain wipped around and caught me right between the legs. I was afraid to even look down it felt like I was kicked. Only damage was some scuffing to my double front carhardts. Now that was a scare!

Stalk? Were you cutting corn? Trees have trunks. A trunk can be referred to as a stem, or if it is denuded of branches it can be termed a spar.

Glad you avoided damage.

 

[Xtra]

LOL . . . yea I guess I meant stem or spar.

I had to cut it high because it had a horse fence connected to it. As I was coming up I must have made a groove in the wood, shifted the bar and threw the chain off. The chain slapped around me from front to back . . . thank God for that chain catcher.

 

[Ekka]

Don't forget that the failure had contributing factors

A/ worn parts (links) used to join chain

B/ links not spun together but hammered

C/ excessive wear on drive sprocket

So, it will come down to maintenance procedures and negligence ... the company will be fined! Some-one joined that thing up.

And perhaps those things dont have chain catchers.

 

[Xtra]

Do processor chains run faster than a handheld chain saw?
That must have been a lot of energy to throw a tooth thru that much plexi.

 

[P_woozel]

They run prtty quick,way faster than any woods saw, and they have gobs of torque. Never timed one, but itts way quicker than a 2-stroke saw. :umpkin:

 

[disandat]

Had a chain jump off once and wrap around my wrist. I was only wearing rip-stop nylon and the saw was a Husy rental. The chain was streched (to many renters) and pretty worn from all the novice sharpenings. Yep...definitely will not rent ever again.

Oh, barely even a scratch...much do to the fact that I got of the throttle the instant it jumped.

 

[Oregon Engineer]

Xtra - The processor or harvester chains run at double the speed of a chain saw!

Most chain saws are in the 2 to 7 HP range for .404 chains, the harvesters are in the 20 to 50 HP for .404 chains, the 3/4 pitch machines can go up to 75 HP.

The feed force you put on a chain saw is the weight of the saw plus a bit more if it is dull, 10 to 20 lbs. The harvester pushes on the bar to generate 70 to 200 lbs at the center of the bar.

Add it all up and that's why "chain shot" occurs on the harvester machines and not on a chain saw.

Chain saws occasionally will break a chain but the energy is not enough to create a chain shot. However, if you get hit between the legs with one end of a chain it will feel like you got shot! How long did it take before you looked down? Oh, you make me weak in the knees!

Ekka - The machine in the slide show did not have a chain catcher or a chain shot guard.

The chain catcher on a harvester is different than on a chain saw. The harvester chain catcher is a spool the extends out from the center of the drive sprocket about 4+ inches. It will only "catch" a "loop" when the chain is thrown. If the chain breaks, the chain catcher will not catch it because the chain ends never cross by the spool. That's where a chain shot guard comes in, it is located right behind the drive sprocket and it prevents the chain from undergoing a dynamic whip lash that creates a chain shot.

 

[Oregon Engineer]

If you could not open the slide show - here are two pictures from the slide show. One shows the cab and hole in the window, the other picture shows how the harvester head was oriented when the chain shot occured.

The operator was in the cutting plane, and worse, the bar tip was aimed at him.







.

 

[Xtra]

Thanks for the info Oregon Eng.
Wow, that's a lot of force & energy!

. . . and yes, it took a moment or two to finally look down.

 

[Oregon Engineer]

Check out the piece of steel that went in the front of the operator and had to be surgerically removed out the back.


Place three pennies side by side in front of you for scale.

 

[MasterBlaster]

An impressive bit of shrapnel, to say the least!

 

[Oregon Engineer]

The pictures show the location and design of both the chain catchers and chain shot guard on a harvester. The chain catcher is a spindle extending out from the side of the drive sprocket and it catches the chain when a loop is thrown. The chain shot guard is semi-circular in shape and located close to the drive sprocket and in the same plane with the bar and chain. When a chain breaks the broken end comes into contact with the guard before it does the whip cracking motion.

 

[Oregon Engineer]

Here are some pictures of chain shot guards on other machines. The pictures were taken at the 2005 Oregon Logging Conference in Eugene, OR.
The chain shot guard is the semi circular band of metal following the edge of the of the drive sprocket and chain path.

The spindle coming off the center of the drive sprocket is the chain catcher.



A Denharco chain shot guard

A Valment chain shot guard, the grease flung off the drive sprocket at piled up on the chain shot guard, (no chain on this head).

A Waratah/John Deere chain shot guard

If you have a harvester head let me know what kind and if it is supplied with a chain shot catcher.

 

[notahacker]

Not only was there high velocity on the driver link, but it was so hot it melted it's way through the "plexy glass." That is a scary thing to think about.