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Re: Ah, *THAT* was what was coming

PostPosted: Wed May 07, 2014 12:21 am
by see3d
Do the bearings have to be lined up so that the strings are exactly vertical between them? If the bearings could be pushed together (in the X plane), and the strings angled a bit between them, they would not take quite as much extra width.

Would you preload the bearings if you have a double bearing?

I kind of like the V groove, well not exactly a V, since there is a flat bottom. The flat needs to be very concentric and the string no so big that it does not touch the bottom of the groove.

Would a wobbly single bearing introduce positioning errors?

Re: Ah, *THAT* was what was coming

PostPosted: Wed May 07, 2014 12:32 am
by Nicholas Seward
The string has to be vertical.

What do you mean preload?

One wobbly bearing will mess it all up but it should be easy to find problems bearings.

Re: Ah, *THAT* was what was coming

PostPosted: Wed May 07, 2014 1:16 am
by see3d
I was thinking some kind of very thin springy material like a wavy washer between the two bearings inner races at the post, but perhaps there is not enough room between the bearings inner races because the outer races are pushed together.

Hmmm, I wonder if a magnetic preload of a single bearing is possible? Perhaps a bit too exotic for this simple machine.

Re: Ah, *THAT* was what was coming

PostPosted: Wed May 07, 2014 2:01 am
by Nicholas Seward
The act of the string trying to pull between the 608s should do a decent job of removing the play from the bearings. (I could never get the string to actually slip between.)

If I go with the single bearing with the integrated groove the play should be axial and that shouldn't matter.

Either way, the tension in the string should remove any play that matters.

Re: Ah, *THAT* was what was coming

PostPosted: Wed May 07, 2014 5:55 am
by Dpharris

Re: Ah, *THAT* was what was coming

PostPosted: Mon May 19, 2014 2:41 pm
by cdsteinkuehler
Any progress on a design update? How is the first prototype working out after getting some hours on it?

I'm heading to Corporate HQ next week and will have access to several laser cutters. I want to try and cut a few sets of panels while I'm there. I'll do at least one set of the original design (probably more unless cut time is really long), and would love to cut a new version prototype design as well! :)

I also just got a decent CNC router I can probably press into service to cut out some panels, but it really looks like they want to be cut with a laser.

Re: Ah, *THAT* was what was coming

PostPosted: Mon May 19, 2014 4:58 pm
by Nicholas Seward
I only have about 40 hours on the proto but it shows no signs of needing any maintenance except a little string tensioning.

The new version is mostly set in my head which is the hard part. Now I need 4 hours of free time to turn that into a model and then a few days to find mistakes. Before you posted I had already given myself a deadline of this coming weekend so I will see what I can do. BTW, the new design will use around 24 625vv's. I hope to have some early renderings soon.

Re: Ah, *THAT* was what was coming

PostPosted: Mon May 19, 2014 6:08 pm
by cdsteinkuehler
No rush on my account, but if I can't cut material next week it might be a month or so before I get a chance to use the laser cutter again. But it's not like I don't have enough other projects to keep busy! :)

Re: Ah, *THAT* was what was coming

PostPosted: Mon May 19, 2014 7:24 pm
by Nicholas Seward
Well, if you are brave then I am going to take advantage of getting you to do some testing. It will be very likely that I will have the design done but I will have done no physical testing by next week.

Re: Ah, *THAT* was what was coming

PostPosted: Mon May 19, 2014 7:46 pm
by cdsteinkuehler
I'm brave, particularly since the material is cheap and I only have limited access to the laser cutter.

I can't commit to making a working mechanism, but if I manage to get the laser cutter functioning properly (there are several available, all typically in various states of [dis]-repair) I can at least report if the pieces fit together as expected. :)