@johnb you’ll need someone better informed that me to give you a definitive answer! The BT-5 is known as a ‘light tank’ so I am guessing the need to spread the weight across a larger surface area may not have been so critical and tracks could be periodically dispensed with. It may have travelled somewhat like an ‘armoured car’. So possibly, when covering some distance on road and solid ground the advantage may have been to gain some speed by removing tracks, and upon arrival at the point of combat to put the tracks back on as the need to go onto more challenging terrain arose.
I believe this was part of the original rationale for light tanks, designed using the Christie suspension style after WW1, when they had tended to be pretty slow and suffer track failure even when in non-combat situations.
From what I know (searching photos of the BT-5) many of the BT series of tanks used this system, and it was also used on T-34s. I’m pretty sure though, that the T-34 never went without tracks as it had gained significant mass compared to earlier forms.
I’m sure someone will be able to correct me!
@lgardner Louis - as a Tanker what is your take?
