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Posted by chriscase [76.212.214.3] on Saturday, June 23, 2012 at 20:32:29 :
In Reply to: Re: Crossmember may be the weak point? posted by Desoto61 [98.166.17.169] on Saturday, June 23, 2012 at 19:36:55 :
know from dyno runs that full throttle is only pulling with about 100#. (126# torque on a tire 18" radius = 84 pounds of pull. That is why 5,000# trucks seldom climb out of a dyno. Your welds only need that as absolute strength. A bead around a 2 1/2" tube is 10" long by 1/8" thick, min, so has 1 1/4 square inches. The weld filler you are using is good for 60,000 psi tensile strength, at 1.250 square inches, or 75,000# total. Vs 100# of pull- oops your Cummins is 300 lb/ft, tire 18" radius, so call it 200# pull. Guzinta 75,000 gives a safety factor of tree hundred and seventy five. A poor solder joint is probably adequate. ;^0
Now, extending the hitch a foot or so, and with a drop hitch downward a like amount, will add lots of bending torque. So, tongue weight of maybe 750#? If you don't think the 375x safety factor is enough for your crappy welds, add the plate to the inside like I suggested.
Remember, I play an expert on the interwebs, but You are the nuculy-ear engineer. Go an engineeratate.
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