How do you guys deal with "chain shot"?

[hosslog]

Howdy Fred, From your description of folks attitudes it sounds like I would fit right in.Can I bring my horses?
Seriously, after I saw the pics my reaction was, is all that power necesary.

[crtreedude]

They would love your horses!  We have a herd - or so it seems at times. 4 mares, one gelding that was a stallion. And one of the mares is pregnant. We are about to buy two more horses for the second finca (farm) 

My horse, Toro, was used to haul logs when we bought him - he isn't very big, but boy is he strong! If a 4x4 gets stuck in a ditch, they hook it up to him and he pulls it right out, and we are talking some steep ditches.

We just had some visitors and she owns a Morgan, she rode Flor, Amy's chestnut mare and wanted to take Flor home.  It is pretty rare down here to use a bit - almost all the horse are neck reined and respond very well to just about command.

The only issue for me when I first got here is dealing with horses that love to run! You will spend you entire time holding the horse back if you like to walk.  :D

I have a friend down here that uses a Water Buffalo for dragging logs - usually they use two oxen, but only one Water Buffalo is necessary.

Fred

[SwampDonkey]

Oregon, I think I seen a thread you had started on this earlier on a forum at Forests.com . Glad to see you over here as a new member, as it doesn't seem like their forum is very active. Sorry I can't help with your question though. If we had some experienced operators on here that were trained and certified by the NBCC we may have some type of answer for you. I'm sure there are other folks experienced with the problem somewhere on the forum, they just haven't discovered your question. Just be patient. I'm on dialup , like Gary is and I can't even come close to loading those internet videos within a limited time frame. ;)

cheers

[Sawyerfortyish]

Oregon I don't have a feller buncher but I think it is safer to have one guy sit in a heated or air conditioned cab of a machine then to have two or three guys doing the same job with chainsaws.  Your chances of getting hurt in that cab are minimal. Yes mishaps happen but the danger of getting hurt doing the same thing manualy are many times more. Of course if you guys are leary of running these dangerous machines you can send them to me and I'll experiment with them for while to see if there is really a problem : ;D

[crtreedude]

I suspect the best approach is inbetween. I think if I were to ride a horse between here and the finca, besides taking a long time, it would increase my chances of an accident. However, using a race car would probably shorten my life expectancy.

There is probably a safe rate of power and speed - and then there is something else.

Just my dos colones

[Oregon Engineer]

Gary C - Don't be fooled by the "big" Timbco with 3/4 pitch chain as the only machine capable of chain shot. Any machine set to over speed and over power any chain (3/4 pitch or .404 pitch) will produce a chain shot. Most of the chain shot work done is on .404 pitch chains.
Most used chains that have been bent have micro cracks on the surface. Please do not try to straighten them as there is a crack just waiting to get bigger! Besides the danger of breaking, bent drive links also will gouge out your bar rails and over heat adjoining chain links.

Happy to hear you have tuned your system so the chains are not breaking. Chain manufacturers will supply you with recomended maximum speed and power for safe operation of the chains you are running. Check the chain box for factory phone number and give them a call. You can verify your chain speed with a tachometer, the power is done using the gallons / minute and the line pressure. Send me a private message with your address and I will send you a handbook that gives advice on proper chain speeds and how to calculate power.

Here is an article from a Canadian magazine with some good tips.
http://www.findarticles.com/p/articles/mi_qa3764/is_200408/ai_n9449962

Thanks for the input on your operating methods!!

Caryr - Motor power, chain speed, bar sweep speed, bar feed force, lubrication, and chain maintenance are the major factors in generating a chain shot. Direction of the plane of the bar, thickness of the cab windows, location of bystanders, and presence of a chain catcher are the major factors that determine if the chain shot is going to hurt someone.

Super sonic speeds can be obtained when a bull whip is cracked with your bare arm. Imagine what 20 to 100 HP will do!!!!!!! The pieces can be accelerated to 894 miles/hour and turning 400,000 rpm, those are some of the numbers published from test labs in Europe for .404 pitch chains. The dynamics of the chain motion impart all the energy in the chain to the last two or three links durng the "snap".

Many manufacturers have come out with "chain catchers". These are not designed to catch a chain shot. They are designed to prevent the chain from "snapping" so a chain shot is never generated. They are usually located close to the drive sprocket so the chain is "caught" before the end of the chain goes into the dynamic "snap". But, there is nothing stopping a chain shot if it comes off the nose of the bar!!!

Thanks for your input, and be careful that machine is within the power and speed limits of the chain.

Crtreedude -  Higher power and chain speed mean higher production. There is a balance between production and operator safety. I'm hoping this thread will alert operators to methods to increase their safety, they already know how to increase production.

Sawyerfortyish -  The machines are fffffffffffffffaaaaaaaaaaaaaaarrrrrrrrrr safer than a man in the woods with a chain saw in his hands!!!!!! But when you can cut a 20 inch tree in 2 - 3 seconds there is alot of power that needs to be respected and handled carefully!!

[SwampDonkey]

Oregon,

Thanks for bringing this info forward to the forum. As you read through the forum you'll notice that some threads can take a turn, then a twist, and land back on the tracks. That's just the way things fall into play alot of times and most of us are comfortable with that format. There is less tension if there isn't someone leaning over your shoulder asking you to stay on topic. Plus we get more interesting threads. ;D Don't be surprised if a thread turns into food (grits) or the weather. When some of us get reading a thread we inadvertantly reply with the first thoughts in our heads. ;) ;D We are all (or most of us are) friendly on here and value everyone's contribution, large or small.

I'm aware of the Canadian Woodlands Forum and I wish there was more participation by small woodlot owners and contractors working woodlots. It seems to me purhaps those forums are geered more towards industrial contractors , maybe I'm wrong. Of course our provincial Marketing Boards are doing what they can to promote safety, as I was employeed by our local board for over 10 years. There are alot of folks still not attending field days and training courses that would greatly benefit. It's been a problem sometimes attracting interest and alot of it (I think) has to do with everyone's schedules and plans during their quality time. Some folks are putting in long days and sitting in a public forum or training course isn't what they have in mind at the end of the day or weekend. It's everyone's responsibily however, to be educated/informed.

cheers

[Oregon Engineer]

Swamp Donkey - A bit of variety does make it a lot more interesting.

I'm curious if anyone has found any damage on their machines from a chain shot.

The picture shows part of a "chain shot machine" that is operating in a Swedish test lab. The orange line shows the shape of the chain.  The number 1 shows where a knife breaks the chain (first break). The number 2 shows the shape of the chain when the broken end gets back to the drive sprocket. The number 3 shows the shape and location of the chain when the chain end whips or snaps and a chain shot occurs.

[DanManofStihl]

Yeah I saw that post on arborist site.com earleir this week. It looks pretty dangerous I feel sorry for the guy it happened to one of those freak accidents kinda like being struck by lightening I guess. I liked the discription and the slide show never heard of the chain snaping and going through the protective cage though. First time for everything I guess.

[sawguy21]

All this is why I am uncomfortable with being on the "dummy" end of a two man saw.  I only tried it once and the chain headed toward my kisser was unnerving.

[Oregon Engineer]

Hello DanManofStihl - The accidents are not all that freak. There have been several reported ones and likely many unreported minor injuries and near misses. Here is one from New Zealand.

[Oregon Engineer]

Here is an example of a "near miss", most likely a little too NEAR to the guy in the cab.





You can read the entire article at the link below as it is from
a Canadian magazine with some good tips.
Link

[Barkman]

I'm curious what you do to deal with "chain shot" and if you've ever experienced it.

My first thought would have been flack jacket and kevlar helmet, but I like the thicker polycarbonate as well.  It seems to me a basic design flaw that such an expensive piece of modern equipment doesn't include "bullet proof" protection for the operator.  I can't imagine an extra half inch of polycarbonate could be so expensive that it would be worth losing a man over.

[Oregon Engineer]

Polycarbonate is a "softer" plastic and tends to scratch easily. I've heard that operators have to change out windows every two years because the windows get too scratched up to see through.

I don't think it was a cheap operation trying to cut costs as much as just not knowing about the danger. A lot of operators and manufacturers are just getting educated on chain shot and are still unclear as to how thick of a window is needed. It's a sharp learning curve for the market.

Check out the piece of chain that tore up the operator. It entered the operators front and had to be surgically removed from his back.

[slowzuki]

I find this pretty interesting...  I know guys may find it offensive to try and make a tool that is already so much safer than a chainsaw even safer but I'm sure old fellas protested chain brakes on chainsaws.

Reusing bent links would be a big no-no in my book.  I don't know for sure the metalurgy of those chains but would guess they are strain hardened already so a lower grade of steel can be used.  This means it doesn't take much bending to get them to fail.

Limiting the chainspeed would seem to be an obvious answer, I suppose guys would swap out motors and valves etc to try and speed them up.

[Oregon Engineer]

slowsuki,

You're absolutely correct! Reusing bent links is a very bad idea for two reasons. 1) The bent link will not have enough room in the bar groove and will greatly increase the friction generated heat. This wears out the bar grooves faster and burns up the chain links close to the bent link. 2) If you look at used harvester links with a 10X or better magnification you will see very small cracks called "heat checks". The "heat checks" are on most chain surfaces in contact with the bar because of the heat generated during cutting with the power of the harvester. When the link gets bent the cracks on one side grow deeper into the metal and weaken the link. The link does work harden from the bend and its toughness decreases.

You're right on the chain speed issues. Slower chain speeds do a great deal to reduce chain shot. The test lab reported it can not generate a chain shot when the chain is broken while moving below 5900 ft/min but at or above 9800 ft/min they get 100% chain shots with every chain break.  The lab recommends running chain around 8000 ft/min to give the needed cutting speed without overly increasing the risk of a chain shot.

I've talked with operators who drilled out the hydraulic fuild flow restrictor to increase the speed of the chain, they thought they were clever in out smarting the manufacturer. An accident waiting to happen!

Here is some information on how to reduce chain shot.




To reduce the risk of chain shot and injury:
•   Operators and bystanders must never be in the plane of the bar when the chain is moving about the bar.
•   Appropriate windshield material must be installed.
•   Chain speed should be 40 m/s (8000 ft/min) or less for .404 pitch OREGON® chain and 35 m/s (7000 ft/min) or less for ¾ pitch OREGON® chain.
•   A chain shot guard should be installed near the drive sprocket.
•   Chains should be inspected frequently and damaged or cracked chains removed from service.
•   Always use new  parts when repairing chains.
•   Industry groups recommend that chains should be discarded after the second break.
•   Remove dull chains from service.
•   Always sharpen chains to factory specifications.
•   Maintain proper bar and chain lubrication.
•   Maintain proper chain tension.
•   Replace the drive sprocket when it has visible signs of wear.

[Dom]

I believe our Logmax heads all come equipped with a safety device to help prevent chain shot. I was talking to my boss about it, and he mentioned that one fellow in Sweden nearly got killed, as the chain hit him a few millimeters from a artery. Apparently we already had a few machines come in the shop with chains dangling from the cab area.  The windows are bullet proof, but a chain at high speed can still do alot of damage!

[Oregon Engineer]

Hello Dom,

I've seen chain shot guards on the Log Max machines at some recent logging shows. I took a picture of one. The chain shot guard is the bright metal semi-circular piece directly behind the chain that is rapped around the drive sprocket.




Hey, if there are chains parts hanging from the cab, someone is playing Russian Roulette!! Let them know the parts fly as supersonic speeds and they should not be in line with the bar and chain. Treat the bar and chain like a loaded gun, don't aim it at anything important!



Do you know who made the window and what model it is? I'm curious as I'm also in contact with a New Zealand logging company that is installing bullet proof laminated windows as a safety measure.

[Dom]

Yes, that would be the chain catcher. We always have plenty in stock for our customers.

I know what you mean about Russian Roulette!

As for the windows, I'll have to check. We sell all of our machines (Rottne's and MHT's) with lexan windows.

[Oregon Engineer]

Just to make sure I've been clear. The LogMax machine in the picture has both a chain shot guard and a chain catcher. I've labeled them both.

[Dom]

Yup, I understood. I went for a short walk in the partsroom today, and found both parts. We use Marguard windows for our machines, if that's any help.

Also,  Oregon chains are great, that's all we sell.  ;D

[Buzz-sawyer]

I would like to use some of these windows to build a shield to use on my headrig...I have nothing now I would like to rig it t o swing into positionwhile sawing........basically a simple bulletproof window...........???? Sound like a winner? How much would a 4'x4' piece run?

[SwampDonkey]

Buzz, don't forget the A/C in that booth. 

[Oregon Engineer]

Buzz-sawyer

Marguard and Lexan are two brand names of polycarbonate that are used in cab windows. The European test labs have found that .404 pitch chains can penatrate a 12mm thick window. There have been no tests done with 3/4 pitch chain so I don't have any info to pass on there. Some tests were done to determine how thick of a window was needed to stop cutter teeth from the large hot saws (circular saws with a 2 foot or larger diameter mounted in a harvester head). The material thickness was 1 1/4". 

I'm in contact with a New Zealand logging company that has installed "bullet resistant" series 300 windows from Ace Security (www.acesecuritylaminates.com  1-888-607-0000 or email info@usace.com). The web site has some very interesting videos and check out the news reports. The bullet resistant windows are a lamination of glass and plastic. The glass is easy to clean and does not get scratched up like an all plastic window.

[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.


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