Hi Guys
I've been working on a system to negate the need for magnets but still retain the benefits of their anti backlash and quick disconnect properties. I saw a post a while ago where a maker had used strings to hold the effector and the rods together. Heres what I've come up with :-
I chose to use Spectra line (100lb breaking strain) and springs. The springs came in a box of assorted springs from Ebay. I modified my J Head effector and the CP III rod carrier to have 8mm 'cups' to accept some 8mm stainless steel ball bearings I found on Ebay that have a 4mm diameter hole, or socket, drilled in them to a depth of 4mm. The aluminium tube I already use for the magnetic rods on CP III have an ID of 4mm and I sourced some 4mm brass tube to act as connectors between the ball bearing and the rod ends. I secured it all with a dab of CA but as it's all held in tension it's not really required (makes assembly easier though).
Components :-
[attachment 37309 20140727_083344.jpg]
Assembly :-
[attachment 37310 20140727_083419.jpg]
[attachment 37311 20140727_083437.jpg]
I tied a loop of Spectra 130mm long to the end of one of the springs and secured the loop knot with a dab of CA. I also covered the knot with a bit of heat shrink sleeve but it's purely cosmetic. I used a small length of coffee stirrer stick to ensure the loops on each of the three springs were the same size :-
[attachment 37312 20140727_083751.jpg]
[attachment 37313 20140727_084201.jpg]
The end effector has a hole in the face between the rod 'cups' through which I passed the end of the loop of Spectra. There is a hole on the under side that accepts a small self tapping screw and the loop just goes around the head to secure the string to the effector. The carriage end of the spring has a small piece of stainless steel wire that passes through the hole in between the rod carriage rod 'cups' and is simply bent, once passed through the hole, flat to form a hook. The wire needs to be quite stiff to hold the tension. I used aircraft locking wire.
[attachment 37314 20140727_084505.jpg]
Once the effector is 'strung' you can pull against the tension of the spring to insert the rods. Each pair will hold firmly but a single rod will pop out if you let go. It's a bit tricky but once you get the hang of it it goes very smoothly.
[attachment 37315 20140727_084719.jpg]
The end result is a VERY firmly attached effector :-
[attachment 37317 20140727_084822.jpg]
I am so pleased with this arrangement that it's going to be my standard method going forwards. All the new parts are drop in replacement for the standard Cherry Pi III so if you want to convert it's really easy.
STL Files
[attachment 37318 MiniVWheelRodCarrierNonMagneticx3330.32P3T3BPLA.stl]
[attachment 37319 ZProbeEffectorJHeadNonMagnetic.stl]
I hope you find the above useful
Regards
Andy
I've been working on a system to negate the need for magnets but still retain the benefits of their anti backlash and quick disconnect properties. I saw a post a while ago where a maker had used strings to hold the effector and the rods together. Heres what I've come up with :-
I chose to use Spectra line (100lb breaking strain) and springs. The springs came in a box of assorted springs from Ebay. I modified my J Head effector and the CP III rod carrier to have 8mm 'cups' to accept some 8mm stainless steel ball bearings I found on Ebay that have a 4mm diameter hole, or socket, drilled in them to a depth of 4mm. The aluminium tube I already use for the magnetic rods on CP III have an ID of 4mm and I sourced some 4mm brass tube to act as connectors between the ball bearing and the rod ends. I secured it all with a dab of CA but as it's all held in tension it's not really required (makes assembly easier though).
Components :-
[attachment 37309 20140727_083344.jpg]
Assembly :-
[attachment 37310 20140727_083419.jpg]
[attachment 37311 20140727_083437.jpg]
I tied a loop of Spectra 130mm long to the end of one of the springs and secured the loop knot with a dab of CA. I also covered the knot with a bit of heat shrink sleeve but it's purely cosmetic. I used a small length of coffee stirrer stick to ensure the loops on each of the three springs were the same size :-
[attachment 37312 20140727_083751.jpg]
[attachment 37313 20140727_084201.jpg]
The end effector has a hole in the face between the rod 'cups' through which I passed the end of the loop of Spectra. There is a hole on the under side that accepts a small self tapping screw and the loop just goes around the head to secure the string to the effector. The carriage end of the spring has a small piece of stainless steel wire that passes through the hole in between the rod carriage rod 'cups' and is simply bent, once passed through the hole, flat to form a hook. The wire needs to be quite stiff to hold the tension. I used aircraft locking wire.
[attachment 37314 20140727_084505.jpg]
Once the effector is 'strung' you can pull against the tension of the spring to insert the rods. Each pair will hold firmly but a single rod will pop out if you let go. It's a bit tricky but once you get the hang of it it goes very smoothly.
[attachment 37315 20140727_084719.jpg]
The end result is a VERY firmly attached effector :-
[attachment 37317 20140727_084822.jpg]
I am so pleased with this arrangement that it's going to be my standard method going forwards. All the new parts are drop in replacement for the standard Cherry Pi III so if you want to convert it's really easy.
STL Files
[attachment 37318 MiniVWheelRodCarrierNonMagneticx3330.32P3T3BPLA.stl]
[attachment 37319 ZProbeEffectorJHeadNonMagnetic.stl]
I hope you find the above useful
Regards
Andy