What I needed was to carry my bikes on my camping trailer but still be able to access my camping gear. The racks also needed to be demountable as I use the trailer for logs, materials, trips to the tip etc.
O.K. So I decided to go for a pair of Thule 598's from Roofbox, as they were the only ones specifying 20kg/bike, and had adaptors for square bars.
I got the local blacksmith to make me 4 of these:
and 2 of these:
The lower mounting holes of the brackets are fitted to the trailer chassis, the upper two were drilled through the side and all were fixed with 8mm ss bolts with penny washers on the inside to spread the load. Used nylock nuts for anti vibration security.
The pin through the bracket, with R clip, secures the bar leg in place.
So I now had me a trailer with a 'roof rack'. There was about 2mm of front/back play in the front bar, but this dissappeared when the Thules were fixed in place. There was no lateral movement as the wooden spacers behind the bracket, make the legs quite tight. Some silicone spray helped getting the legs in and out. I expect the wood will compress/wear after a few uses, if it does I will replace with hardwood. The spacers are there to allow the tarpaulin to fit in place
I had ordered adaptors for square bars, these fit around the bar and easily clip into place. They can be 'handed', so fit either side.
Minus batteries etc. the bikes aren't too bad and the lift isn't very high (even for a short arse like me).
When I first put the bikes in place the racks held them well. But I gave the trailer a few heavy sideways pushes with my boot and there was a lot of lateral movement relative to the trailer. So I made a padded wooden brace to fit inbetween the saddle stems. Then, using ratchet straps, I pulled the left bike to the right, and the right bike to the left, so locking them together.
Now, when I 'push' the trailer sideways, the bikes move with it but not relative too it, so removing strain from the rack and fixings. The brace is crude but is held in place by the straps pulling the bikes together. I'll be putting some sort of safety cable on it before venturing on the motorway.
Next step is to hitch the rig up to the car and drive it round some dodgy Welsh roads and see how it does. I'll post any mods I have to do.
Hope this helps someone else.
Ben