Because I have worn out several cattrax bearings (the roller wheel type) this year, I started thinking about another design with real ball bearings.
This all has to do with the fact that I have to drive a long mile through my village and I'm always in a hurry. So I tow with 40 km/h.

Anyway, using ball bearings forces you to use separate axes through the rims. Hence you need two long loading-tubes instead of one for creating a carrying construction for these axes



The trick of this design is that only one loading tube has wide rolls mounted on 18x clickroller bearings at both ends. While the other loading tube has simple rubber roll-supports which are fixed!

You maybe can see this on the photo: front tube has special rollers, backtube not.

So when you place the trax in front of your cat , you start pushing it onder the bows with the wide-rollers tube first. Pushing with your foot against the other tube will slide the trolley quite easy under your cat.
Without sliding unwillingly backwards!

For unloading the cat from the trolley, you push the cat to the front from behind. again it will roll quite controlled from the trolley.

There are two remarks: I have to fix the cat with rope to the troley (can't use cradles because of the hullshapes). But with this design you can easily change the fixed rubber supports on the backtube for cradles! Never hanging cradles again.

Second: it will cost you a few do. Special connections, converters from 50mm to 20 mm for the rimaxes. The special rollers for the 50 mm tube.