Bsmet95:
Now that ToadJ mentions it, I do remember the proprietary lower flanges/rails, but it’s been a long time since I’ve dealt with one. For all my rants on rushing to computers, I would use FEA to analyze the rail flange/web detail under the trolley wheel loadings when I was producing many of these per year. And, I would probably do the same with this hanger fitting, since you are making hundred of these too. I think I would try to design at this detail, so that I didn’t have to reinforce the rail top flange. Again, I have many more questions for you than I have answers.
1.) Are the bolts 3/4", what grade?
2.) I noticed the side pls., instead of the end pls., shortly after my first post. You will have a prying type affect when you tighten the bolts down on the side pls. It causes bending moment in the bolts approx. equal to (bolt pretension)(4.375"/2 - 1.75). But, I don’t imagine you pretension the bolts to a high degree. Then you’ll have it again, likely in the opposite direction when you load the detail.
3.) I would not make the slotted holes in the beam flg. any longer than needed, you are stealing from the flg. bending strength. Punching these holes is more fatigue critical (sensitive) than drilling these holes. And, you might even consider grinding a slight chamfer around the hole edge as a burr/crack clean-up.
4.) The web/flg. weld so near these flg. bending conditions could be a fatigue problem. I would grind or nibble bevels on the rail beam web, .5 or .75" long at the upper corner, at the splice, so I could run the double sided fillet welds into a full pen. weld and off onto a run-off tab. The tab can then be ground off, eliminating the exposed fillet roots at the splice line.
5.) I would use larger, thicker, washers, and some locktite on the threads. Maybe to the point of a drilled bar above the two bolt heads on each side, at the underside of the top rail beam flg. Although, I suspect this is what you are calling a stiffener, and hoping to avoid. You might do the same thing across the hanger fitting top pl. under each pair of nuts. In each instance the idea is to rationalize a shorter bending length and/or a stiffer bending member under the bolt. The drilled bar makes sense on the rail beam flg., but a thicker hanger fitting top pl. is probably less expensive than adding the bars, but still use larger washers.
6.) Do you see any wear or beating at the tips of the rail flgs. from the trolley wheels? The real problem may be more a matter of flexibility (deflection) of the whole system at a splice, and thus instantaneous differential rail height right at the flg. tip as the trolley moves over it.
7.) Does the gimbal allow for 360° movement, or only lateral movement?
8.) I still wonder if the top pl. on the hanger fitting might not be the critical element. It’s the thinnest pl. and it is also the narrowest beam element as it spans from side pl. to side pl. Again, draw us some FBD’s of this detail, in several views.
9.) On a detail this tight and riddled with holes and load points and reaction points, it is tough to do a simple analysis, as in simple beam bending and shear stresses, etc. It can truly be said that the loads and stresses will by multi-axial within each plate, and pretty complex around so many stress raisers. If you don’t have access to FEA, and you make hundreds of these per year, maybe you could go to your local college Prof., and for a few bucks, offer this problem to one of his/her students as a term paper.
