Disclaimer... There may be some errors in my ways and I took a simplified route to get here.
So be nice if you catch a fuck up. I'll make it up in detention.
I was thinking about what actual loads were on the wall and ramp and chainfall for the tractor
lift/storage I posted about. According to the specs the mower weights 490lbs and is 68in overall.
Obviously this is simplified as the full load is spread out over the span of 4 tires and not a single
point load.
The unistrut pivot is 55 inches or so above the floor and the ramps are 90 inches long.
With some good ol' trigogenometry on the calculator I come up with the cable seeing 301lbs
static load and the wall seeing 237 lbs horizontal load spread out over 4 2X6 studs.
Also, another thing to take into consideration is the mount I made for the snatch block in the center stud.
That cable is loading the stud toward the mower and the ramp is pushing the stud away from the mower. Close to net zero load.
The hand winch is rated for 1600lb
I'll get better pictures of the set up later this week.
Now the simplified horizontal load. Again, taking some liberties because it's already been
2-3 hours of fartin around here. I came up with this.
Using a calculator for two static loads on a beam the results showed 277lbs on the unistrut
bolted to the wall and the CHAINFALL is only seeing 212lbs. Well under the 2000lb rating.
I weight just under 250lbs and I would stand on that unistrut beam all day long drinking beer.
The beam the chainfall is mounted to was recovered from an old mill building and we got it
at a salvage yard for old lumber.
6" x 10" and and the chainfall is bolted 28 inches from the vertical wall. 212lbs is like extra dust
to that ol' girl.
If, on the odd chance structural integrity becomes questionable, you can always beef up existing framing with some angle iron and then you can park a howitzer up in that nook. That's my hillbilly math and I'm stickin to it. Ohio Guy
ReplyDelete250 lbs? Sir, I've got you beat by over 100 lbs ;)
ReplyDeleteThen again, I'm not this adventurous any more...
I remember the chain fall having an angle to it. Did you account for that? Your load will have a vector off of vertical at the back. Not trying to be pedantic here, just accurate. Cosine theta is a stone cold bitch. The unistrut isn't the weak spot, the fasteners in shear are. But spread out over that length, you are handling that easily. Reminds me of statics class and Mr. Copenhaver. Or Mr. Copenstabber after you got your bleeding test back. Nicest executioner you ever met. Navy pilot, carrier rated, WW2. Great man, tough professor.
ReplyDeleteI have a square tube in the ceiling joist in my shop that spans 3 joists. I use it with a couple deadmen to pickup things to put on skates. Lots of old tech works just fine, even in these days of idiocy...
Snatch block?
ReplyDeleteIzzat like a chastity belt?
You should take the arm & moment of the ramps into account when considering the stresses on your unistrut fasteners. That 245 lbs at the rear wheels is effectively considerably more load due to the distance from the wall. Your chainfall mitigates that added stress to a degree, but it’s still there.
ReplyDelete