The constant throwing of tracks was becoming an issue. Having read lots of threads and ideas on other sites I went through each of them one by one. This is my conclusion.
The tank is big, and has a long hull with a big wheelbase (same as the Abrams). Fitting metal tracks, wheels, idlers and sprockets adds stress to the hull. This causes the hull to flex. To get the correct tension on metal tracks, I think pulls in the adjuster and the gear box so causing the track to run out of alignment. I have never run mine with plastic tracks so cannot comment. Or the original Heng Long metal tracks it came with.
Two things seem to be common. The terrain the tank is run on and scale appearance.
One thing I did come across is a lot of is people in America, who battle their tanks, and are less bothered about scale appearance run, metal road wheels, sprockets, idlers, with plastic tracks, on hard packed dry dirt. They drive the
out of them without any issues. Fit metal track and they cause a ruck of issues. I wanted more scale appearance so opted for metal tracks with rubber pads. I also run on a more muddy, gnarly, moist terrain. My solution to the de-tracking issue was to get everything in alignment. This involved running a straight edge along the wheels and filling where required to get the road wheels in line with the sprockets and idlers. A pair of drive shaft bearings were installed, and drive sprockets were purchased with guide rings. A frame was made to stop the hull flex. This stopped the tensioner from flexing outwards and kept the hull from flexing. I also installed harder springs in wheel position 1, 5, and 6.
I don’t think this is just a problem with Heng Long Challenger. I have been in communication with a person, who is building a 1/6 scale Challenger who has the same issue with tracks.
Idlers built with 4mm nuts and bolt, supported inside by the aluminium frame. This IMHO, stops the idlers bending outwards, so helps the tensioner to do its job.
