Everybody knows that the headstock is the most highly stressed part of the frame right? So it needs to be stiffened. But "bracing" can actually increase the likelihood of the frame breaking if done incorrectly. With the advent of laser cut gussets you see more and more gussets that are decorative rather than fuctional. So this is a quick run through of the problems that you can cause yourself with gussets and brackets in general.

Example "A" in the illustration is about the worst way to do it. The end of the gusset is (where all the stress is) is virtually square to the tube axis when viewed from the side. All this achieves is to concentrate the loads caused by any flex right at thr point where the gusset ends. So instead of being spread over the weld fillet where the tube joins the headstock the stress is now concentrated where the gusset ends. Basically a point load, so that every time you have a slight deformation of the frame that point gets a work out which is how you get metal fatigue.

Example "B" is an improvement as the gusset is the traditional "fish mouth" shape. The whole point of this is that the ends of the gusset dont provide as much stiffness. This means that initially the tube will flex where it meets the gusset, but then the gusst starts flexing too, and the point of flex travel along the tube towards the headstock as the load increases. This reduces the tendency for the tube wall to fatigue as the point of flex travels around as the load alters, which doesn't happen in Example "A".

Example "C" is better again as the gusset is mounted tangentially to the tube which means that the tube experiences torsional loads (which its VERY good at handling) as opposed to crushing loads (which its not very good at all at dealing with). Here's an exaggerated sectional view which might make that clearer.

The left hand picture shows a tangential gusset and the right hand one a radially aligned gusset. As the tube tries to flex the radially aligned gusset will deform the tubes cross section, if the gusset is arranged like Example "A" in the first illustration this deformation will occur at the same point and if the motors a bit of a "shaker" the deformation can be caused by engine vibration. So it is perfectly possible for the frame to break simply from the vibration of the motor before it turns a wheel in anger. The tangentially aligned gusset however tries to twist the tube rather than crush it which doesn't deform the section of the tubing so badly, if at all, which drastically reduces the chances of a failure.

If you've grasped the principals of all that then it's pretty obvious that it is also better to mount tabs and brackets tangentially if at all possible. At some point I'll expand this to cover brakets and tabs too. Just don't hold your breath while you're waiting......