pic: DeWalt drive base: side module

[Greg Needel]

Originally Posted by AdamHeard

3/4" diamater shafts will definately be strong enough; especially if they are steel. Depending on the size of the pin you're putting through, aluminum should be just fine. Either way, 3/4" is kind of heavy though. I guess you don't have much of a choice w/ the current interface with the dewalts though.

[note] this is not picking on adam I am just using it as an example [/note]

There are alot of things that go in to the"strength" of a material in an application. Just saying that it will be strong enough shouldn't really cut it when contributing to a design.

As an example when you are talking about strength it is obvious that you are referring to not failing during application, but in what ways is the part strong enough. Are you concerned with the torsional strength to make sure the shaft wont twist off? What about the bending stresses of this kind of loading And don't forget to take into account the stress concentrations caused by the pin slot and the fatigue strength due to alternating loading...What about the shear strength of the pin itself?

I guess my point is there is alot more that should go into the design of a system like this, and just making wild guesses could cost you in the end. If you under design something you can get a failure and if you over design you have wasted weight and real estate for this mechanism.

Now I realize that 95% of the teams out there probably don't do/ know how to do any of this math and just throw stuff together (I know I have fallen to the same fate from time to time) but in the off season when we have plenty of time for this kind of top level design. I urge everyone to open a book or ask someone who knows for help on these problems rather then taking the "backyard engineering" approach and just winging it. Same goes for those offering suggestions on design to be able to backup your suggestions with some theory. Remember there are teams who live and die by the advice given on these boards and you want to make sure that they are given correct information.