Options for sliding mechanism of lens carrier plate on 11x14 DIY

[LarsAC]

Hello,

I am in the midst of building an 11x14 camera (god knows who planted this crazy idea into my brain). I've got some basic parts done, among them a base board and a slider plate as a lens carrier.

My first idea was to use rails from a drawer as a sliding mechanism when moving the plate back and forth while focusing. However, they don't seem rigid / stable enough at 400mm extension.

A simple option that comes to mind is are beams with a groove mounted left / right and a tongue on the base board (like Pali did on his 11x14).

On ebay I found rather cheap linear bearings (for building e.g. 3D printers or CNC machines) like this.

Has someone tried some of those for the above purpose or in general and can report about stability / durability?

Any other ideas ?

Many thanks,
Lars

[LabRat]

First, all of the options you listed add quite a bit of weight... The traditional approach works well by having a smooth lockable slide/surface that mates well with another... If hardwood is carefully polished/fits, it slides well, but even better is polished hardwood that moves against smooth aluminum, where the friction is very low... (Plastics, too...)

Test the friction of traditional materials first, before trying to fix an issue that may not exist later...

Steve K

[Jac@stafford.net]

Wood against wood, properly waxed works very well. I prefer Maple for those parts.

A possible issue with the metal or composite slide rails is locking them down without damaging them.

Very best of luck with your project!

[John Layton]

I investigated various ball slide-rail systems years ago (for 4x5 and 5x7 cameras)...had planned to attach focus racks to these and use preload springs on focus shafts to apply some constant braking force on the system - with final lock achieved (as I do currently) with non-coaxial shaft clamps. This would avoid the need to apply clamping force/friction to the rails directly and thus protect them from damage. But the more I thought about the ball slides...the more they did not make sense. Too heavy, too expensive for those that offered decent specs.

But there are some quite sturdy double extension ball slides for drawers...and I could envision at least further investigating the incorporation of these into an ULF camera. The trick would be to truly incorporate them structurally... so they would not become redundant, while still adding in some means of pre-loading the system to keep it appropriately dampened. Then again...the beauty of the wood on wood or metal on metal sliding contact in a more "conventional" sliding slot system is that the mechanism itself is both self dampening and incorporated directly into the structure of the camera itself.

[LarsAC]

Thanks for sharing your experiences. Will try to make a sliding mechanism with a groove and some waxed wood. Probably the easiest.

Lars

[el french]

I don't think the Mgn9 linear slides would be too heavy. The only real problem is the quality control on these rails is really bad. I'm using some rails made by STAF that are really nice, but they cost 10 times as much

[radii]

I don't know to what overall level of quality you're building your camera, but I'd say that those ebay linear bearings will be more than adequate.
A difference between a low cost bearing from china versus a high end one from Korea or Germany might be noticeable when compared side by side, running freely. Once they're under load however, in a low tolerance requirement operation such as a view camera (vs computer chip assembly for example), the differences truly don't matter anymore.
I've used both types and there are a myriad of other mechanical issues that come up, before the quality of the linear bearings becomes an issue.