Etymology of ratha, as battle-car

There are pictorial motifs which link an 'endless-knot' motif and a
'battle-car'. On one pictorial, the knot appears right in the
centre, just above the chariot in motion.

In this context, the following Sanskrit lexemes seem to be relevant:

krandas = battle cry; grantha = knot (which word later gets used for a
script in India; kiranti = knot in Tamil). Can these phonemes,
krandas, grantha explain the 'ratha' in Sanskrit?

I shall be grateful for info. on cognate forms in IE for semantic
sets: battle, battle-car, battle-cry, knot.

Or, is rad- just relatable only to rota- wheel?

Thanks.