The choice of beamer depends on the type of condenser (and reciprocally). The fundamental parameter is Throw Ratio (TR). See beamer page for more details

See simple mechanical assembly

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Wide Throw Beamer

TR<1.5 use 50mm without additionnal lens

the easiest to make using 3D printing. Model is here:

http://www.thingiverse.com/thing:1863766

The 50mm LSS-BLOC: click here for the mounting in video ! (without 3D printing)

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Standard Beamer

TR>1.5 use Heligon or 50 + add lens or simplified condensor unit

mounting in video : HERE

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Experimenal

If you want to build your own condensor: click here (Better than with a camera lens if your beamer has a long throw lens)

 

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Rodenstock Heligon Notes

If you are lucky enough to have a Rodenstock Heligon 75mm:
(They are the best!)

front view

rear view

we can seen 2 different kind:

• without removable lens (and without housing)
• with a removable rear lens
  

The first type Heligon is more interesting, without removable lens, because it's possible to keep the entire field while maintaining it close to the beamer

In the case the objective lens is removable, the latter lens is a divergent, that extends the focal length back (like a barlow).
If we really wanted to place the heligon near the beamer, it's possible to remove the rear lens, but with a high chromaticism. 
If you prefer to preserve the superior optical quality of Rodenstock, it will be necessary to pull the block 10-15 cm from the beamer to obtain a complete field