4x4ord wrote:
transamz9 wrote:
4x4ord wrote:
justme wrote:
The problem will be vibration and welds could fail if not engineered properly. So be ware.....
I am am a descent welder .... I can't recall having a weld break ever. However I am concerned enough about the welds holding the hitch I build onto the trailer's frame that I plan to have my nephew, who is a professional welder, do that part of it.
I've pretty much decided to use 5x5x1/4" square tubing for my hitch. I'll have two 4x2 receivers spaced 4 feet apart to attach the bike carrier. Additionally I will fabricate a 2x2 receiver in the center of the 5x5 for double towing. If I'm going to remove the nice hitch currently welded on this trailer I might as well replace it with one that is certain to be sufficient.
The tongue weight of my bass boat is 500#+-. The rear cap on my rv is a full cap that goes all the way down to the bottom of the frame rails. The ball on the hitch is about 16" from where it attaches to the cross member. I used two 3" structural channels that I welded together to make a 3"X3" square tube. I forget the lb per foot the channel was but the gauge is 3/8" thick. It is attached to the frame rails with 4"X4"X1/4" angle 3' long on each rail. I welded 1"X1"x1/8" X-bracing all the way up to the rear most axle to help the frame rails take the side to side loads. I know 500 pound tongue weight is not 800 pounds but it is a 5,000# boat yanking on it too. This is the second rv I've towed this boat with. 9 years with no problems.
The 800 lbs on its own doesn't concern me too much. The two things about my application that cause me to be a little precautious are: that the frame rails are 6 feet apart and the 800 lbs has 5 feet of leverage working to twist on the hitch. That works out to 4000 ft lbs of torque on the hitch. If the ball of a trailer hitch is 16" from the cross member and a 3000 lb tonge is placed on it the cross member ends up with 4000 lb ft of twist on it. With my limited knowledge of things, I am confident that 5x5x1/4 wall tube will be able to handle the load, but without having an engineer's involvement I would not be comfortable going any less.
I believe if it were me an I was going to carry something like that I would take the twisting force out of the equation by having two cross members. The receiver's capacity would be my bigger concern. I'm assuming that the motorcycle is longer than 6'. Can you bring a receiver straight out from each frame rail and run the cross member across between the two receivers to allow for a 3rd receiver for a trailer?