Lens & O-rings for the MDX?

NutSAK

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The o-ring sits between the rim of the reflector and the lens. However, you only need the oring if the lens sits lower than flush with the brass rim of the module. There is some variation in the depth of the reflector rim in the modules. If yours sits deep enough that your lens doesn't sit "proud" of the rim, use the oring. If the lens protrudes beyond the rim, you don't need the oring.

The idea is that the lens seals against the gasket, not the brass rim of the module.
 

NutSAK

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I took a quick pic of my EDC VME to illustrate. See how the lens protrudes from the rim of the module? This one doesn't have the oring, nor does it need one. Adding an oring in this case will only serve to space the module farther away from the head opening, which is not a good thing. This lens will seal against the gasket perfectly fine.

49967427466_d6bf84565c_k.jpg
 
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thermal guy

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This makes sense. But I always use that O-ring for a bit of extra protection. Although In a elzetta it gives you more of a gap as the head will not screw down as far.
 

NutSAK

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Using the o-ring when you don't need it will make the beam more ring-y, as you will be blocking more of the spill at the head opening. The farther the reflector is spaced away from the head opening, the greater amount of the beam you are blocking, just the same as the large lens vs small lens discussion in the 16.5 head above.

The oring can also be used to increase the head thread gap where needed, as you mentioned, but I would only use it if the head bottomed out at the threads.

16.5mm heads were set up this way for years (gasket, lens, no o-ring) without any detrimental effects that I'm aware of.
 
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Whitelight1

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Using the o-ring when you don't need it will make the beam more ring-y, as you will be blocking more of the spill at the head opening. The farther the reflector is spaced away from the head opening, the greater amount of the beam you are blocking, just the same as the large lens vs small lens discussion in the 16.5 head above.

The oring can also be used to increase the head thread gap where needed, as you mentioned, but I would only use it if the head bottomed out at the threads.

16.5mm heads were set up this way for years (gasket, lens, no o-ring) without any detrimental effects that I'm aware of.

Thanks for the info and the picture. After re reading everything you wrote, I guess it would be a good idea to buy and swap out the lens that came with my MDX heads for a smaller VME lens. I will order a VME gasket kit once he gets some stuff back in stock.

I called and talked to Cathy about a week or so ago about when the 16650 bodies might be in stock. She thought they might be at the powder coaters, but when she checked she said it is going to be a couple weeks because they got a new "machine" and is trying to figure it out. (Just in case anyone is wondering why there are almost no bodies in stock, that could be the reason) I was thinking about a 16650 with a E2XT to go on it.
 
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