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DoESLiverpool / Tosca

Machinekit-powered polargraph drawing robot
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Design and build two sets of "corner pulleys" #13

Closed amcewen closed 8 years ago

amcewen commented 8 years ago

The motors and spools sit on the floor and the thread then loops over some "pulleys" (they'll likely just be eyebolts) in the top corners of the drawing area.

@DefProc used eyebolts on a laser-cut wedge for the TLRN to good effect, so we should build something similar to hold the two threads for the polargraphs.

amcewen commented 8 years ago

A pack of 10 M6 eyebolts http://www.ebay.co.uk/itm/160870170069 has been ordered, should be arriving on Tues 23rd.

DefProc commented 8 years ago

Ah. I have some spare On 20 Feb 2016 15:29, "Adrian McEwen" notifications@github.com wrote:

A pack of 10 M6 eyebolts http://www.ebay.co.uk/itm/160870170069 has been ordered, should be arriving on Tues 23rd.

— Reply to this email directly or view it on GitHub https://github.com/DoESLiverpool/Tosca/issues/13#issuecomment-186626128.

goatchurchprime commented 8 years ago

Might need these to be real pulleys that introduce less friction into the system. There is a huge difference in force pulling in and letting out, and it's the letting out that's critical to the speed. The string needs to run easily when the gondola is put into falling mode.

amcewen commented 8 years ago

The eyelets have arrived and are in the Tosca storage box.

DefProc commented 8 years ago

The braided fishing line is UHDPE, so it should provide it's own bearing surface, so it's unlikely to significantly reduce the amount of friction in the system (although there is some wear, so for ultimate longevity, pulleys are technically better).

What's the requirements for mounting the top brackets? Self-adhesive pads onto a painted/glass surface? Screws and rawl-plugs into a drilled hole in blockwork?

How many strings do you need to control? The current implementation seems to have two per motor. Is that just because the motors are mounted to double pulleys? Will you switch to a single line? _(The 0.45mm line _is* strong enough)*

amcewen commented 8 years ago

The two strings help with the stability of the gondola, so we're sticking with two string option.

In discussions today we reckoned that the current TLRV versions are working well, and we won't know any more about how they need to be attached until we've had the site visit (issue #19), but then might just need to get a copy of the files and cut a second set.

DefProc commented 8 years ago

Ok, they are designed for a single centre screw mount, but could be adhesively mounted is the base surface is good enough On 27 Feb 2016 19:13, "Adrian McEwen" notifications@github.com wrote:

The two strings help with the stability of the gondola, so we're sticking with two string option.

In discussions today we reckoned that the current TLRV versions are working well, and we won't know any more about how they need to be attached until we've had the site visit (issue #19 https://github.com/DoESLiverpool/Tosca/issues/19), but then might just need to get a copy of the files and cut a second set.

— Reply to this email directly or view it on GitHub https://github.com/DoESLiverpool/Tosca/issues/13#issuecomment-189703860.

amcewen commented 8 years ago

The Knut polargraph will be mounted on the window, so we should be able to reuse the existing mounts with some command strip (I've bought some, it's currently on my desk though I'll stick it in the Tosca box in the workshop)

For the main Tosca polargraph, @epsaul, presumably we can just add some eyelets to the top corners of the drawing board?

amcewen commented 8 years ago

We're going to use the eyelets chased into the drawing board, so this is now sorted!