Sextuple red build

[logsquared]

kev/rob has issues with rgb and screws

Screws suck seriously though, in torture testing my combiners, screws gave me the biggest problems. So you know what? ... i got rid of all unnecessary screws in my newer designs. As a matter of fact I have a 6 combiner with no screws except the 2 that hold it to the table and the collimator lens screws.

[LaNeK779]

Screws suck seriously though, in torture testing my combiners screws gave me the biggest problems. So you know what? ... i got rid of all unnecessary screws in my newer designs. As a matter of fact I have a 6 combiner with no screws except the 2 that hold it to the table and the collimator lens screws.

any pics of that ??

[logsquared]

any pics of that ??

Sorry man. That's top secret! Just kidding. I'll go take some.

[logsquared]

The pics are of a basic test platform. I have since expanded on the idea. Unfortunately, I had to add some screws. However, the new screws don't adjust or put torque on the mirror mounts. The only real problem I have with this extremely simplified design is metal property related. I fully annealed the brass. Annealing the brass made it too soft. This in turn makes the mounts a PITA to adjust. I should have just stress relived the brass. My newer design modification take that problem out of the equation. I will post some pics of the newer design when its finished.

[LaNeK779]

this is a new design to me!!! and i really like it!!!

i have to stop looking at pictures eventually, or else my own multi-diode setup will never start to materialise!!!

thanks for the pics mate

[Zoof]

Another seemingly large improvment would be to replace the steel screws in the kinematic mounts with brass ones, preferably of the exact same alloy. @ Edison, since you have your mounts machined, this is within reach for you.
With two different metals in them, the mounts are literally `bimetals' that are used in many applications to sense temperature. Exactly what you don't want in the projector setup.
So TEC cooling the whole setup to a set and stable temp is one option, the other is to re-engineer the components that are the cause of the symptoms. (treat the cause, not the symptom)

[MisterWilling]

Another seemingly large improvment would be to replace the steel screws in the kinematic mounts with brass ones, preferably of the exact same alloy. @ Edison, since you have your mounts machined, this is within reach for you.
With two different metals in them, the mounts are literally `bimetals' that are used in many applications to sense temperature. Exactly what you don't want in the projector setup.
So TEC cooling the whole setup to a set and stable temp is one option, the other is to re-engineer the components that are the cause of the symptoms. (treat the cause, not the symptom)

Manufacturing brass screws like that would not very economical and most the point of these build is to save money. The only reason screws are affordable is because they are massed produced, unless you are making 1000 your money would be spend on other efforts. even mass produced, the m2 set screws are relatively expensive.

[Zoof]

Manufacturing brass screws like that would not very economical and most the point of these build is to save money. The only reason screws are affordable is because they are massed produced, unless you are making 1000 your money would be spend on other efforts. even mass produced, the m2 set screws are relatively expensive.

Brass screws can be bought though. Will have an expansion coefficient much closer to the brass block than steel screw. One step further would be to match the brass of the block to the screws or even like you said get the screws made to match the block, but on second thought I doubt that level of perfection is really needed.
It all depends on how far you are willing to go to get a stable setup. I'm going to be buying brass screws to tame the kinematic mounts, though. If a couple of euros and some effort can help keep the alignment right, it will be worth it.
Seems simpler than to TEC cool everything.

[logsquared]

Even an all brass mount will most likely need temp control. Operating temps of +-10deg C or greater are not abnormal. I have found through testing that even 5deg can really throw off alignment, even with all brass mounts. I found with brass bodies and stainless screws the mounts were less sensitive to temperature. However, The brass + steel combination exhibited higher hysteresis. Meaning, they wouldn't return to exactly the same spot when brought back to the temperature where set. I also found that using aluminum instead of brass made the hysteresis problem a lot worse. This was especially true with aluminum flexure mounts. The most temp. stable mounts I have made so far are contructed of cold rolled steel.

These are just my findings with the mounts I have built and a few commercial mounts I have around. Other mount designs may not have the same problems?

What does all this mean? Clearly, I need to TEC the whole base plate of my projectors.

[Zoof]

[QUOTE=logsquared;183791].. I have found through testing that even 5deg can really throw off alignment, even with all brass mounts. ...QUOTE]

So you actually already tested the all brass set screws in a brass mount for alignment issues, and the result was not better than brass mounts with steel set screws? If so it is unexpected, and I'm very interested in hearing more about what else you tested.......