Jim - two of the channels "converted" to an I beam 4 in. high, 1.584 * 2
inches wide with a flange thickness of .296 inches and a web thickness of
..184 * 2 in. and 16 ft long showed a max stress of 25064 psi & 1.281 in.
deflection with a 2000 lbs center loaded weight. You didn't use the
"uniform loading" option, by any chance?

Hul

Jim Wilkins wrote:
"Hul Tytus" wrote in message
news
Jim - for the free center 16 ft version, take a look at an I beam
with the
two channel (4 all total) pieces within it in place of the 3/8 in.
center
support. Cleareance on the bottom could be a problem and the lack of
a
horizontal surface on the inside of the I beam flanges too. But an I
beam in the center gives a greater strength for the greater
stresses. You
could get a 6 ft I beam and make it even longer...

Hul

I bought a 3.5' length of W6 x 9 (?) for the purpose when I got the
channel. This morning I used the 25% Labor Day coupon on another HF 1
Ton Push Trolley which fits pretty well on the 4" channels with the W6
sandwiched between. Spacing the channels 3/8" apart moves them off the
lower web fillet. The flanges are parallel, not tapered. It helps to
finally have all the pieces to play with.

I get a maximum stress of 17.5 KSI for a W6 x 9 16' long, center
loaded with 2000 Lbs, compared to 12.5 KSI for two parallel 4"
channels. I could abut the upper channel flanges and reinforce the
tension side joint with a splice plate, then struggle with moment of
inertia calculations for the combination.
thanks
-jsw