When we had our HTT, I had a Swagman Platform-Style 2 Bike Rack for 2" Hitches or RV Bumpers Swagman RV and Motorhome Bike Racks S64663
Swagman 2 bike platform rack on the rear, I also had a 2 bike one mounted on the tongue. When we purchased our new TT two years ago I wanted to carry up to 4 bikes off the rear of the TT. The Swagman rack is one of the only racks truely rated for RV use, and is very solid and absolutely does not bounce like other racks. I purchased a second Swagman RV 2 bike platform rack and planned to attach both the racks on one tube sticking off the rear of the TT.
Step one, have a welding shop weld on a 2" receiver hitch to the rear frame of the TT.
Step two, remove the bike racks from their mounting tubes and install on one single longer square tube.
To complete this task, I purchased a length of 2" square tubing, I purchased 48" of 3/16" wall thickness tubing. The original tubing off the Swagman rack was 1/8". I figured the extra length sticking out would need a stronger tube. Original tube is on top, new tube on bottom of pic.
I then determined how far the tube would stick in the receiver, I slid it in as far as the reciver extended under the bumper of the TT, maximizing the surface area of tube to receiver contact. I then marked the hitch pin location and drilled a hole in the tube, same size as the Swagman original tube. I then purchased a nut the same thread size as the Swagman hitch pin bolt
and welded the nut to the inside of the tube. This now closely mimics how Swagman built their tube. The tube actually bolts into the receiver, almost removing all up and down motion when towing.
I had to next determine the length of the new tube. I wanted to minimize how far the bike rack stuck off the back of the TT. I inserted the tube into the receiver, installed the bolt, and slide one bike rack onto the tube. I then put a bike on the rack and slid the rack into a position that allowed about 3" between the TT back-wall and bike handle bar. I then marked the place where I would need to drill a hole for the rack attachment bolt. Next I slid the second bike rack on the tube and positioned bikes on the rack to determine how far apart the racks would have to be and still have pedal and handlebar clearance. I ended up with 17" center to center between racks. I tried to minimize the distance, and I have to move the bike wheel trays side to side to get all the bikes to fit. If I had to do it again I would make the distance 18".
I then marked the hole for the second bike rack retaining bolt and also marked the length to cut the tubing to. I ended up with the tube being 35" long, you length would vary depending on receiver location. I cut the tube, drilled the holes, and gave the tube a coat of paint.
The final assembly resulted in a bullet proof, no bounce rack. I did add a U style anti-rattle device to remove the last little bit of up and down movement of the rack.