Maine Hunting Forums banner
1 - 2 of 2 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter · #1 ·
I have noticed a common defect in the welding of aluminum tree stands.

When welding aluminum, if you just stop it leaves a crater at the end of the weld. It is common knowledge among welders that these craters need to be filled at the end of every weld or it will crack. Leave a crater and eventually any kind of stress will crack it. This is a bad trait in tree stands and upon my inspection of several brands in a large nation wide chain store I observed it was common to several brands of welded aluminum tree stands, but particularly bad in the foriegn made stands. Pits and holes in the middle of the weld are caused by starting and stopping and coming back in to finish an incomplete weld. Each time it is started and stopped it is creating a weak or stressed spot likely to start a crack in novice and unskilled welds.

Just look for yourself. Any one who bothers to look can see it. The weld should be smooth and consistent and not look like bubble gum jammed in the corner with a tree branch.

I believe this is an attempt to be price competative. It would require stopping the robot arm at the end of the weld and filling the crater on every single weld. And this would slow down the process. For human welders there is really no excuse except a lack of skill or knowledge. The time required to fill a weld crater for an expirience and skilled welder is barely noticable and even less so on a bench set up and repeated welds of the same type.

This does not appear to me to be a brand specific defect. It was present in many brands of tree stands I observe in a retail out let just recently. Nor do I believe the failure of a single weld in any of the tree stands I inspected is likely to lead to catastophic failure but how many cracked welds will? I don't know. How many can you not notice before the last one brings on a bad end to a good hunt? I don't know. I do know as a welder there is no excuse for this. I'd never let my work out of a shop like that.
I believe this is an industry wide issue that needs to be addressed by TMA, Treestand Manufacturer's Association
http://www.tmastands.com/index.html
If you own an aluminum welded tree stand or any other product involving aluminum welds, I suggest you inspect it carefully prior to purchase or use. I've seen the same defect in many other products involving welded aluminum. If they had craters or pits in the welds, they had cracks.
This is what a crack in a weld will look like.

This may not be as obvious on your stand. Paint, corrosion, or dirt will obscure it but it is still visible. One way to make it obvious is to put stress on the stand if you are suspicious by setting it up low to the ground and step up on to it while you or some one else watches the suspect weld. If one part moves and the other doesn't then that weld is cracked. It may be either in the weld or may have cracked away from the base material. If this appears cracked I'd suggest you take a wire brush to it and clean it up. This is what has been done in the photo above. If it turns out to be good you can repaint it.
Now in conclusion, I have several tree stands. Steel, climbers, bolted and welded. Several of my own stands are welded aluminum construction and I've now inspected them all for this trait. They all have craters at the end of some welds. Many welds start and stop and have big gobs in the weld. Obvious amature hour welding. Only one stand has had any cracks and this is my favorite tree stand. It is over 5 years old and I love this stand. I've used it what would probably be a lifetime of hours for most hunters and I didn't baby it in any way. Sitting on the bar, tieing equipment to it to carry for all day trips, and using it for any other incidental need to climb a tree. When I brought it to the attention of the manufacture they bent over backwards to make it right even though this was obviously not a new tree stand and I have no qualms with the company other than I believe they need to address this issue the same as the rest of the industry does. This is a trait of a high quality reputable company. When a customer has a problem with their product, they don't make excuses. They fix it.
I ask hunters to keep this in mind when you make a purchase. Look a product over but think about the "what if" that may lay in the future and buy from a company you can trust to make it right and back up their product. I wouldn't even slightly suggest you throw out a stand with craters in the welds. I would suggest you do a good inspection on a regular basis and that you wear your fall protection equipment at all times. I know they all say to wear it but I'll be honest, I felt completely safe in this stand with out it. I've hunted for years out of this stand with out my harness. I wouldn't have done that in any other brand.
Things change.
I got lucky.
I'll never get off the ground again with out my harness on.
Not on ANY TREE STAND of ANY BRAND.
Here are independent supporting links discussing the aluminum welding process and the relevant text.
http://www.alcotec.com/ateqtrn.htm
Crater Fill Feature: Other characteristics of aluminum that can provide welding problems are associated with its thermal expansion, which is about twice that of steel, and its shrinkage on solidification, which is 6% by volume. This can increase both distortion and weld crater size. One common concern when welding aluminum is crater cracking or what is sometimes called termination cracking. When MIG welding with conventional equipment, once the trigger of the welding gun has been released, the arc is extinguished, and no additional filler metal is added to the weld pool to fill the crater. Consequently, if no further precautions are taken, a large crater will be left which will have a higher probability of cracking. Craters can be serious defects and most welding standards require them to be filled and free from cracks. Run-off tabs or other methods of locating weld craters on scrap material away from the weld are not usually practical. However, if the weld pool size can be reduced before the arc is fully extinguished, the resulting crater may be very small or almost eliminated and, consequently, the weld may be free from cracks. In the past a number of welding techniques have been used in an attempt to reduce this termination problem. Reversing the direction of travel at the end of a weld, increasing travel speed to reduce crater size, and providing suitable build-up and remolding the crater area flush with the weld surface by mechanical means are some of the methods which have been used. These methods are often difficult to control, require specialized training, and are not always successful in their objective. More recently, welding equipment has been developed for aluminum welding which has a built-in crater fill feature. This feature is designed to terminate the weld in a gradual manner by decreasing the welding current over a predetermined period as the weld is completed. This feature may be adjustable to enable the user to select the most favorable termination conditions and thereby prevent a crater from forming at the weld termination. Tests have shown this crater fill feature to be extremely user friendly and very effective in eliminating the crater-cracking problem.
http://www.lincolnelectric.com/knowledge/articles/content/alum.asp
Convex-shaped welds: In aluminum welding, crater cracking causes most failures. Cracking results from the high rate of thermal expansion of aluminum and the considerable contractions that occur as welds cool. The risk of cracking is greatest with concave craters, since the surface of the crater contracts and tears as it cools. Therefore, welders should build-up craters to form a convex or mound shape. As the weld cools, the convex shape of the crater will compensate for contraction forces.
http://www.lincolnelectric.com/knowledge/articles/content/wing-enterprises-little-giant.asp?print=y

http://www.alcotec.com/attsaw.htm

http://www.jwharris.com/welref/techguide/for_copper/filler_metal/ (see crater cracks)
Crater cracks
Leaving crater open at end of weld
Quickly reverse direction fo travel and "seal" the crater, or
Speed rate of travel approaching end of weld, reducing size of weld pool as arc is broken, or
Use runoff tabs at the end of weld.
Additional links to personel pictures of welds on stands of a different brand from the first one.





 
1 - 2 of 2 Posts
Top