A swing set question
I'm building an all-cedar "swing fort" from blueprints I purchased online. I'll try my best to briefly describe it before asking my question. It's 5 feet by five feet, with six posts cemented in the ground. There is a post at each corner, with a post halfway between the corner posts on either side, which supports the swing beam. The swing beam is a 4x6, and sits on top of the two middle posts, which are 4x4. The swing beam overhangs on either side of the posts, and this is where the swings hang from. Sorry, it's difficult to describe without pictures!
The posts support a fort and is bolted together in various places and seems very sturdy. My only real concern, and the topic of my question, is how they want the swing beam attached. The swing beam sits on TOP of the two middle poles, and is supposed to be held on by four triangle brackets, one on either side of both posts. These brackets are 1/8 inch steel and 15x15 inches, so they seem pretty heavy duty. I understand the reasoning of putting the swing beam on top, for the downward strength, but I can't help but think that the side-to-side motion of the swing could loosen the brackets. My nightmare is that swing beam falling off.
My brother is going to school to be a carpenter, and he's seen the plans and says "if they're designed by an engineer, they must be fine." part of me wants to believe this, but something is just giving me the heebee-jeebees about the way they want the swing beam attached. Do you have any thoughts on this?
I'd be happy to post a link to the plans I bought, which shows a picture, but I got kicked off of a different forum with this same question, and I assume it's because I posted the link and they thought I was a spammer. If you have any other questions about this, please let me know. Basically, the bottom line is that I just want it to be safe for my kids!