DIY: 20x24 build: re-iteration

[mdarnton]

As soon as I post that about helical multiple-thread lead screws, ads start showing up in my browser because of my search. This one sounds particularly interesting. It sounds like it's 8mm travel per turn, just the right length, price is right:
http://www.banggood.com/3D-Printer-3...h-p-980650.htm
or, longer:
http://www.banggood.com/900mm-Lead-S...-p-993963.html

Apparently they're used with stepper motors in CNC type machines.

[Bernard_L]

Hm, thanks. These are actually heaviest cabinet rails i could have find I tested it yesterday with heaviest lens i got - 36inch Cooke, it didn't seem to go funny much, but it could be b/c my bellows just didn't go as far ( i do have plans to add intermediate frame to allow for more than 37" extension - whole thing can extend to about 48-52" as far as hardware
But i get what you saying - i was thinking about making extra layer on the bottom to make center to be more sturdy anyway - adding extra extendable rails under the base, might be an idea there. Got to think on prototype..

For a moment though - there is always Alex T. solution with Bogen's extendable support for heavy lenses

Sorry I wasn't clear. I do not question the rigidity of your horizontal bed. My concern is with the front standard (vertical), more precisely, the mechanical linkage that should ensure that it's perpendicular to the camera bed. That linkage is made by two pieces of plywood held together by two pairs of rather small metal angle brackets. You might of course make these more massive, but you will gain a lot more rigidity with a pair of diagonal bars running from the mid-height point of your front standard to the camera bad; inclined at maybe 30° from vertical. It's a basic principle of mechanical design that a triangulated structure is more rigid mass-for-mass. Other view cameras are often built that way, and you would benefit even if you do not want to implement fron tilt (which would be an easy fringe benefit).

Again, congratulations.

[SergeiR]

Ah! Front standard itself. Yeah. that one is a bit questionable, you absolutely right. Additional angled support indeed would help. Need to find good place for slotted aluminum (i tried to do it myself, and failed miserably.. makes me miss days of middle school, when i had access to all the milling/lathe machinery..)

[SergeiR]

As soon as I post that about helical multiple-thread lead screws, ads start showing up in my browser because of my search. This one sounds particularly interesting. It sounds like it's 8mm travel per turn, just the right length, price is right:
http://www.banggood.com/3D-Printer-3...h-p-980650.htm
or, longer:
http://www.banggood.com/900mm-Lead-S...-p-993963.html

Apparently they're used with stepper motors in CNC type machines.

Thank you for links!.

Yep, i got one of those cool acme-threaded (i know official name, thanks Randy M ) for me New Year present. Unfortunately i don't have secondary support for it, or secondary nut And local stores.. well.. no help, at least all the usual hardware places i checked.

[mdarnton]

It evades me why you would need two nuts, but if you do, you could buy a 6" threaded rod+nut from the same source, for about six dollars, and throw away the second rod. But it seems like you only have one thing to move here--the front standard--and the front and back ends of the rod would be the anchor points that don't move. So at most you'd need a machinist to grind a neck on either end for the fixed bearings at either end--one longer to stick through the back for the knob attachment, to use this type of rod, then hook the floating nut to the front standard.

Acme is only that particular square thread shape--that description doesn't include the multiple-thread/high pitch speed attributes of the rod.

[Tin Can]

Seems a few of us are building cameras.

I am trying to build an 11x14 with only hand circular saw, jigsaw and hand drill.

I am going to worry about the fine focus adjustment last.

I have little to show now, but expect real progress in 2 weeks when parts come.

Code name 'Tinkertoy Camera' as it will be modular construction that can be easily changed and have very little wood.

The second iteration will have no wood.

Maybe

[Lachlan 717]

As soon as I post that about helical multiple-thread lead screws...

Look for 4 and 5 start screws.

The higher the number of "starts", the greater the lead travel.

[Tin Can]

Look for 4 and 5 start screws.

The higher the number of "starts", the greater the lead travel.

Exactly. I also think we need a way to use it for a short distance, by the 1/2 nut or something, so we hand move approximate focus and then shift to fine focus.

[Lachlan 717]

Exactly. I also think we need a way to use it for a short distance, by the 1/2 nut or something, so we hand move approximate focus and then shift to fine focus.

Building that design now on 8x10" and 7x17" cameras!

[Tin Can]

Building that design now on 8x10" and 7x17" cameras!

And?

I will show mine in a couple weeks.