Time for an update....
The boom for this toy was plastic so it had to go.....I'm using a metal boom for the Huina 1580, it's a little longer but should be fine.... to replace all the plastic gears and drives I'm using 35Kg continuous rotation servos....Got them all from Aliexpress.... I didn't take a lot of pictures because folks like Wes Scheideman at Scout works RC and John Gibbs at Huina exclusive have been doing these for years and have some really good videos so I'll just give a quick overview of what I did...
This is the boom and servos.
These are the screw drives that you put on the servos....they are up-grade pieces for the Huina 1580
A straight on view of the screw drive and servo
The drives fit the servos pretty tight, all you have to do is shove the screw drive on then drill a hole thru the servo splines using the hole in the screw drive for a guide...
there are 3 lengths typically the long one for the boom, the medium one for the stick and she short one for the bucket....But then you have the issue of the bucket drive or the stick coming out ( I didn't use limit switches)
I bought 2 sets ( well actually a bunch of sets ... you never know) then use the two longest ones for the boom and stick and the medium one for the bucket.... you still get the full range but the screw drives can't come out because the boom comes to it's travel limit first....
You just have to pay attention and not over drive them or you will tear something up....I got steel roll pins cause simple m3 bolts don't cut it if you get heavy handed
I'll get a shot of the boom assy when I get it all together....