Headtorches

[Kyorei]

Hi folks,

I'd like to build a headtorch from scratch, and am considering an aleph style head (probably an aleph3 or similar).

i currently use a Petzl Myo XP, that I have modified with a Cree XR/E and carclo 10199 8.4 degree optic. works well, but i'd like something with more juice.

rummaging in the parts box has given me some bits to work with -

• a 7.2V 3500mAH LiPo model helicopter battery pack
• a 1000mA buckpuck with external pot
• a Cree Q2 bin XR/E

i need to decide on a housing, and have been looking at all the McR/Aleph stuff with much interest - but some questions: i have a small lathe, and ive been looking at the McR reflectors, thinking i should be able to turn something similar up. ive looked at the diagrams for the McR 38, but have read (i think) it isnt suitable for the XR/E without modification - can anyone tell me what needs to be changed? does the reflector just need to be machined so the bottom of the XR/E's lens is level with the hole?

i'd like to use the parts i have already for this one, but may well build one for a friend from scratch, possibly based on the Aleph 3 design, adapted for a head-mount with separate battery pack - so as an exercise, if any of you folks were building a headtorch from scratch, what parts would you use? bear in mind that this has to be worn on your head - so no going overboard with heavy stuff. im thinking one or two XR/E or Seoul LEDS, a driver board with an external current adjustment pot, for full power when needed but dimmable right down for reading a book and conserving batteries. I like the LiPo heli batteries, as they dont lose charge over time like NiMH's do, and have excellent energy density - so light weight. they come in various voltage-current configurations, tho 7.4v and 11.1V are the cheapest/easiest for me to get hold of. i could always run multiple lower capacity packs in series if a higher voltage was more suitable.


any thoughts or advice much appreciated.

cheers,

ben

 

[Kyorei]

did i say something wrong? surely someone must have some advice to offer, or opinion to venture...

 

[mahoney]

I have not played with an XR-E and a McR 38. In general, you need to get a Cree or Seoul up into a McR .03" or more than a Lux. But when you do, the Cree still may not "play well" with the reflector, i.e. dark rings, etc. I have tested the Cree with the McRs 18, 16, 19, 19XR, 18S, 27L, 27XR, 19 Flood, and 20. IMO, of those, the Cree works best with the 27XR, 19, and 19XR. I really don't see enough advantage for the 27XR over the 19XR to justify the extra weight and size, but YMMV. Seoul emmitters tend to play well with all McRs, and McFlood too, if you can find one. For a close flood, the Cree works well without any reflector. I would suggest a headlamp with one emitter for spot, and one for flood, with separate controls. I'm not qualified to comment on your electrical questions.

 

[hank]

All I can think of is --- the times I've been most cooped up with headlamps have been while caving, in very tight small crawl spaces where I could not even get my arms bent to grab my headlamp until I finished wiggling past some tight stretch that might go on for ten or twenty minutes.

And those were when I was using miner's (carbide/acetylene) lamps.

_No_Way_ would I ever want to be in any of those positions with a lithium-ion battery pack strapped to my head or my tail. No. Nuh-uh.

Acetylene, already on fire, sure, but not lithium even inside a nice mostly reliable not too touchy battery case.

Nope. Outdoors, that's a different story.

 

[Kyorei]

LiPo (Lithium Polymer) batteries are much safer than the old Lithium Ion batteries that legendarily caught fire in people's laptops. in those old batteries, the electrolyte was held in a flammable liquid. in LiPo's, its held in a solid polymer. they are safer, and lighter weight (as they dont have to have a metal casing the same way LiIon's do, and are somewhat flexible.

at any rate, this torch is for bushwalking and cycle touring, not caving, so shouldnt be an issue anyway.

I assume the McR reflectors all parabolic, but just scaled differently. some shorter with larger opening - which allows more direct spill from the LED. and others deeper, so more of the light gets focussed into a beam. are any of them nonparabolic (ie not beam focussed)?

ill have a crack at turning up some reflectors on my lathe and see how i go.

cheers,

ben

 

[mahoney]

The McR's are built around several different (parabolas?) (ellipses?) designed to focus different emitters. For example, the 19, 19XR, 17XR, and 16XR share the same curve. The McR20 and, I think, the 27L share the same curve. You'll have to search the archives for the details.