After quite a bit of testing and destroying carbons with various footings shooting them into a length of angle iron I had driven into the ground with a post driver, I came to the following conclusions which ended up being about the same as Ashby's. I could have saved a bunch of time and money had I just took his advice:)
First, it is important that the insert stays put and does not drive into the carbon shaft upon impact. If it does, it then becomes a simple machine being a "wedge" and therefore will split the end of the shaft very easily. Of the many readily available products I've tried, I settled on using JB Weld slow cure steel epoxy which has proven to me to work exceedingly well.
Second, no matter how well you epoxy the insert into place within the carbon shaft, it needs to be brass as the aluminum insert will easily crush on hard hits. No matter how fixed in place the JB weld holds the aluminum insert, when the insert begins to crush and shorten in length, the material increases in width and again becomes a simple machine becoming a wedge which will split the carbon. The brass insert holds its shape and does not crush like aluminum on hard hits.
Third, if you use a brass insert and properly epoxy this insert into place with a good slow cure epoxy, the insert will become one solid unit with the carbon shaft for the length of the insert. The insert will not become a wedge within the carbon and the carbon will not split. Any footing material added, be it internal or be it external, will need to be longer than the insert itself to be effective. Even then, if the footing has an abrupt ending shoulder, you will be limited in strength as you will continue to have a weak point directly behind this abrupt shoulder. Therefore, having the footing with an abrupt shoulder merely moves the weak point behind the head/insert further back onto the shaft.
Fourth, if you use an internal footing which ends with a gradual taper, and you epoxy the leading edge into place along with the brass insert, you will then see the following two benefits:
1. you will maintain a smaller overall shaft diameter compared to adding an external sleeve.
2. having the internal footing ending with a gradual taper eliminates the abrupt shoulder and allows a hard hit to be absorbed over a longer section of shaft which eliminates the weak spot.
As to the collars, I do not see how they would be of any benefit if used with a brass insert that is properly epoxied into place being that the collars are shorter in length than the insert. I can see some benefit if using an aluminum insert, but even then, I do not see how they can prevent the aluminum from crushing on hard hits. I'd suggest switching to a brass insert and an epoxy such as slow cure JB Weld if you are having any breakage issues and dumping the aluminum insert all together.
As to the original question, I do not see anyone coming out with the many needed combinations of internal footings during these hard financial times. I can see possibly something coming out for a singular specialized carbon shaft, but not something for all the combinations. Maybe I'm wrong and before too long we'll see something like this being readily available as are inserts today, but I have doubts.
Otherwise, use brass and use the technique of applying an internal light coating of slow cure epoxy into the shaft deeper then the insert is long. You also apply a similar light coating onto the brass insert. When installed and fully seated, a small amount of epoxy will push ahead of the insert base making a small tapered shoulder that will feather down to the coating you applied internally. I've experimented with this a bunch to include cutting the shaft to inspect the epoxy feathered taper, and I have found this alone can help eliminate the abrupt shoulder that creates a weak spot. Not as strong as adding the tapered internal foot, but much stronger than just gluing in the insert with an abrupt shoulder.
Best,
DB
Topic: manufactured- footed carbons update? (Read 940 times)
