Have only just seen this, and well, the more you know ð I don't have any of the old-type models in my collection all are the later plastic-gearbox with a roof switch type.Â
Incidentally though I think my TW 485 Series 'Tomy Express' might be the old front-switch style chassis & bodyshell married to a newer gearbox as the chassis has the old 'two children' TOMY logo stamped on it with no date, could be wrong though ð
That being said, I found the solution to intentional polarity reversal (because apparently I couldn't just do the obvious thing and use a Mr Motorman with its reverser button ðĪŠ), and that is to simply use a AAA battery in a holder because that's small enough to avoid the recessing and make contact xD
And yeah as implied I just went over to using my Mr Motorman for reversing/shunting for the sake of my sanity lol but hey, had to experiment for SCIENCE (and totally not boredom ð)
Incidentally though I think my TW 485 Series 'Tomy Express' might be the old front-switch style chassis & bodyshell married to a newer gearbox as the chassis has the old 'two children' TOMY logo stamped on it with no date, could be wrong though ð
That being said, I found the solution to intentional polarity reversal (because apparently I couldn't just do the obvious thing and use a Mr Motorman with its reverser button ðĪŠ), and that is to simply use a AAA battery in a holder because that's small enough to avoid the recessing and make contact xD
And yeah as implied I just went over to using my Mr Motorman for reversing/shunting for the sake of my sanity lol but hey, had to experiment for SCIENCE (and totally not boredom ð)
Been building Plarail worlds since 2001; Building when I can in 2023 
