stanwax
Rob's Homebrew - Magmounts the next generation
Hi All
As you have seen in my post about the work on my RGB projector I have taken my magnetic adjustable mounts to the next level. They were initially discussed here
http://www.photonlexicon.com/forums/...ead.php?t=2529
Now I have had the opportunity to see what can be done with them and to see how they can be improved I have made a few mods to them to come up with the design you can see in the images below.
The main two areas that is improved with these mounts have been aired before but I have developed the ideas a little more therse are the incorporation of magnets sunk into the uprights to allow a much closer fit of the fixed and adjustable section, and the use of ball bearings not only at the pivot point as previosly used but now also on the ends of the adjustment screws. In the original design I drilled a slight recess in the green PCB material used for the moveable section and used a bench grinder to put a slight point on the ends of the screws. This was OK but as I couldnt grind them perfectly and consistently - the points were invariably off centre - they tended to shift the movable section around as you turned the screw. This put a jump into the adjustment which was not good. I then reverted back to plain screws but they had a tendancy to try to thread themselves into the the recess in the PCB material.
I decided I need a bearing for precision so the ball bearing came in. I thought at first of glueing them to the end of the screws and then putting a brass insert into the movable section to provide a seat. Then I thought why not fix the ball bearing to the moveable section and put the recess in the screw. As Stevo-o pointed out in the post about the projector you can see the recess in the end of the screws on the pics. I didnt however get the recess central in the screws which caused me to go back to the jump in the adjustment. So I went back to plain screws which work just fine.
The only downside with these screws is that they are 0.5mm pitch thread which though works does not give the fine adjustment I would prefer. I will get some slightly bigger finer threaded screws at some point but until I have a tap that matches they will stay as they are. I could make the screws but my lathe wont do threads as fine as I need and I'm not well practiced in cutting threads yet so off the shelf they come!
The other main difference between these and previous models is the fact that I have now made the fixed section as tall as the moveable part. This has allowed me to put the adusting screws further appart which makes for finer adjustment and the whole thing looks better and more substantial.
You may also note that there are less magnets in fact now only 3 per mount. A pair at the bottom near to the pivot - this is the most important position, and one on the moveable section behind the ball bearing for the top adjustment. This provides just enough pull to keep the screw and the ball bearing snug as you adjust.
The 2 identical mounts I used for the dichros in my projector were made together and in the pix you can see threaded holes one each at the top and bottom. This is where the 2 fixed sections were screwed together while machining and drilling to ensure they were clones.
The optics I use are Edmund 12.5mm dichros so I bored 16mm holes through the fixed section then milled a 45 degree lead in and out to give the maximum area for the beam to pass.
Just to prove how unsophistcated these are, the upright fixed sections are cut and milled from new Ally but the base is a piece I liberated from an old electrical distribution consumer unit I binned last year. I got some nice brass and copper parts from it too.
Finally I wanna just say that I make these parts rather than buy them for one reason only - no its not cos I'm a cheapskate, though this may be true
The pics below speak for themselves in the main but are as follows :-
first image - front and rear views of the complete mounts minus the optics.
second image - this shows the mating faces with one of the pivot magnets and the ball bearings.
Third image - just a close up of the 'inside' of the upright.
Forth image - installed adjusted and in action. Yes the top screw of the left hand mount is behind the other mount - hence the nut on the screw so I could turn it - though tonight I have just made a little brass lever to go on it so its even easier to adjust now.
Hope you like 'em and hope I havent waffled on too much - If I have and you have drifted off - WAKE UP ! (I bet I know someone who has a smiley for this
Rob
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Originally Posted by Buffo
HA-ROFL!!!
