It is actually. The spline shaft moves forward and back there is the draw bar screwed in it and the hydraulic piston at the back pushes whole shaft with draw bar forward to release the tool and compresses that big ass spring.
the hydraulics pushes on that shoulder between splines.
Picture attached shows whole draw bar spline spring assy.
not sure either i think a lot of the bits and pieces makes for easier construction when it comes to making it if you have some high end tools to build it with. the down side to something complex like this one is all the small pieces have to be about as perfect as you can make something so all the error does not stack up and defeat all the effort to make something precise. sometimes simple is good less to go wrong
i guess if you have things like oilers for bearings ,thru spindle coolant and hydraulics you need seals to keep everything separated and the complexity go up pretty quickly as a result.
this spindle makes mine look like a 1st grade science project
40 tapper on the spindle ? i can see going hydraulic on a draw bar above a 30 tapper since they take well over 2500 psi of force. seems like every size up roughly doubles the draw bar forces needed.
it is 40 spindle. Well it is semi simple while I have it here in my hands.
You have to remember that it has internal hydraulics that is where all the complexity actually is.
There is only one magic I can not crack and it has two pistons inside acting kind of against each other.
The spindle part is fairly standard and simple, three bearings shaft and housing(bearing sleeve).
All that is pressed into the main housing, which I think is not so stupid since you do all the bearing preloads and assembly outside and press whole assy into the main body.
The rest is the hydraulic tool change stuff.
when I have a minute I will try to draw the hydraulic bit since the photos can be hard to decipher.
oh and the hyd pressure it swallows minimum 80bar so about 1160psi that is the minimum tool release pressure I think it runs at about 100 - 120 but have not measured it exactly and not sure how that translates to draw bar force. When I have a minute I can calculate the piston area and calculate force.
i want to say a 40 taper needs somewhere around 2500 lbs of force. but that's just ballpark. here is a pdf from nsk is has a lot of design info on machine tool spindles maybe it will help. the second covers draw bar forces and spindle tapers.
the first thing that came to mind about your mystery was some kind of fluid spring for preload' i think spring loaded preloads are covered in the one pdf it might shed some light? i think its used in high speed applications? but if you read through the pdf files you can get more information. they were informative enough for me to save them for reference.
Just to let you guys know I have a victory spindle is all together and it runs like a charm. Have not run it to the max rpm yet (bit of a chicken shit and want all the grease to settle)
So all good thanks for all the help and advice.
i think a lot of the bits and pieces makes for easier construction when it comes to making it if you have some high end tools to build it with. the down side to something complex like this one is all the small pieces have to be about as perfect as you can make something so all the error does not stack up and defeat all the effort to make something precise. sometimes simple is good less to go wrong