Self-Adjusting Spine Support

[jck57]

Top and side views of cradle upright. All dimensions in inches. I hope Mr. Mano, my H.S. drafting teacher doesn't see this.

[jck57]

... slot that is the width of the bearing (plus enough for a washer on each side)? ...

It gets better. Because one side of the bearing is restrained by the groove in the cradle, we only need one washer - for the side of the bearing opposite the cradle. This eliminates the pesky clearance problem so we can make the cradle rabbet deeper.

[jck57]

Specs for a bearing pocket like in the previous post. For an axle of 5/16-18 threaded rod, 1.5" long. One flat washer. Dimensions in inches. Rabbet that goes with this setup should be .25" deep. Thanks again to dpc.

[jck57]

Bought 50' of this:

http://www.ebay.com/itm/3-16-x-50-Premium-Jet-Black-MFP-Sheath-Bungee-Shock-Cord-Made-in-the-USA?item=160764826880&cmd=ViewItem&_trksid=p5197.m7&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D4%26po%3DLVI%26ps%3D63%26clkid%3D8203048849500264412#ht_1305wt_1165

It's thicker/stronger so it doesn't need doubling. Anybody wants some let me know.

[daniel_reetz]

Another way to do the wing bearings. I cut 5/16-18 threaded rod 2" long and then cut screwdriver slots but extra long set screws like this are available retail. With full size nuts the groove that the bearings ride on could only be about 1/8", which would work but a little deeper would be better so I ground some nuts down to about 13/32" OD. Anybody know of ready-made nuts like this?

IMG_1064.JPG

{/quote]

I found the studs here.

I feel a bit dull - regarding dpc's idea:

I'm curious as to why you're using a bored hole around the bearing instead of a slot that is the width of the bearing (plus enough for a washer on each side)? If used a slot instead you won't need any nuts at all. Those CNC machines make pretty accurate cuts.

How is the stud/threaded rod retained? Just screwed into the wood/compression fit?

[dpc]

How is the stud/threaded rod retained? Just screwed into the wood/compression fit?

From looking at the photo of that setup, you can see the thread marks on the plywood as the threaded rod was pushed into the slot, so I think it's just a press fit. There's no force trying to pull the rod out of the slot, so you won't have to worry about this happening.

I guess you could put a screw with washer near each end of the rod and that would keep it from ever falling out. If it were me, I'd just use a small squirt of hot glue or silicone sealant on the rod and be done with it. It's not like that bearing is ever going to wear out and need to be replaced.

[daniel_reetz]

Yeah, I see it clearly now and I agree, it will never need to be replaced. A dab of glue would fix it forever. I'm working very hard right now to lower the overall cost of the machine, and saving on fasteners and specialty parts is a big part of that. Thanks.

[jck57]

I pushed them in with a vise. If you make the groove .28" and press them in they will be there until you seriously attack them with prying tools.

[M@rtijn]

Would it be an idea to have Magnet Strips / Flexible Magnetic Grip Rubber strips on the cradle to prevent the book from moving and being able to lock the cover down with some metal corner cubes or small plate? Any cover size can be clamped this way and improve grip when placing several strips on each side. I don't know if the magnetic strips are strong enough to hold the cover down. Also the thickness of covers vary. I haven't tested it yet, so I can't tell if it will actualy work. See the attached image.

Another or even better suggestion would be by cutting a slot across on each side (similar applied to the large brace for moving the camera sideways) and having two small bolts with spacers left and right for holding down the cover.

[dpc]

If you had a cradle surface that had any sort of mild adhesive qualities (i.e. rubber tool box liner), you could use a velcro strap or maybe even some of that bungie cord to keep the cover pressed against the cradle and you shouldn't need the hold down screws.

Ideally, you could use a nondestructive adhesive like the credit card "booger" mastic glue (booger glue), or the silicone-based material they are putting on those new lint/pickup rollers I see on the infomercials (Schticky Roller) and you won't even need the strap to hold it against the cradle.