Would roll cage tubing, 1.75 x 0.120 be adequate for safety stands?
Trent
It is probably adequate, but I prefer ΒΌ" wall (.250") to be "safe"... the 2" X 2" X .250" square tubing is heavy and cumbersome, but it does give me the warm fuzzys when I am underneath to know that I have 8 of these in place. The Harbor Freight 2" hitch extensions that are 12" long work great and are cheap, especially with a coupon...
2" Receiver Extension (http://www.harborfreight.com/class-iii-12-in-x-2-in-standard-receiver-tube-69879.html)
Don
Don,
Thanks.
I was browsing Craigslist and found those in the local area.
Trent
Don, I noticed a posting from you regarding proper placement of the supports but have been unable to locate it again, related to bulkhead stress. Could you repeat it or provide a link to your post? Seems like pretty important info when I read it initially. Thanks.
Chuck,
My recommendation is to use one per air spring and I found that a length of 12 inches is doable, and that is what I use now. I could actually get 12.5" in there with patience, but 12" is way better than the 11" I originally used. I place the stands on the lower "H" frame member adjacent to the air spring. If you are trying to open or close the gap for repair, then things are a little different. Here are a couple of threads that I have posted in about that process. I have posted about the topic several times with either "frame blocks" or "safety stands", and maybe other terms as well.
BULKHEAD repair parts checklist (http://www.foreforums.com/index.php?topic=24354.msg190482#msg190482)
Wyatt's Rear Bulkhead Horror: (http://www.foreforums.com/index.php?topic=22399.msg170545#msg170545)
Bulkhead Separation - Planning for the Worst (http://www.foreforums.com/index.php?topic=23330.msg181095#msg181095)
Don
There is a sticky about working safely around your Foretravel that includes some pictures of some adjustable stands. I had eight of them made for me by a local guy, thinking that I'd be able to put them in by all air bags at once. Unfortunately, I can't even get them in by some of the air bags. I'm thinking that for serious work underneath I'll need to raise the coach all the way up, then place the stands.
In a perfect world with perfectly square and parallel end cuts, perfect bearing surfaces, perfectly axial uniform loads on the round tubing it is probably OK. A 21,000 lb rear axle load distributed exactly to four points would be 5250 lbs compressive load per corner. A 1.75" dia x 0.12" wall in a perfect world would support about 13,000 lbs. A 2x2x1/4" receiver tube will support over 38,000 lbs.
These will rarely fail in pure compression but almost always due to side wall buckling or lateral bucking. The 2x2 square tube is much stronger in this regard. I have 8, carry 4.
When my life is at risk a safety factor of five is desireable. So I would not use the smaller round tube. A big square tube give you lots of extra capacity for everything that is less than perfect and will be more stable.
Roger