A Mag D Stubby

This one is going to a friend who wouldn't know what to do with a rechargeable battery, so it was
put together to use a D alkaline. A single mode boost driver powers an XP-G R5 at 1.2A. The heat sink
is very substantial so heat shouldn't be a problem. The driver is held in place by a retaining ring and
the whole assembly is fitted to the body tube with thermal grease and a couple of setscrews to make
sure that everything stays solid. An aluminum OP reflector rounds out the front end. Mag switches
are fine except that they take up an awful lot of space, so the tail cap was modified to take a forward
clicky. The GITD switch boot ought to make it easy to find on the night stand.























I do like the look of Stubby Mags….

That is absolutely beautiful!! I like the look and feel of 1D and 1C Mags with tailcap clickies. I suppose one day I'll have to learn to build one myself.

JB

Wow ..... Super cool :thumbsup: :thumbsup: :thumbsup:

WOW that is awesome!:thumbsup:

Nice clean build, you have some good machining skills. I really like the simplicity of using a single D cell and the reduction in size from using a tail clicky.

One thing I would say is that an alkaline cell is not the best choice for this. In this configuration, you would be drawing around 3-4A. NiMh can easily handle this but the alkaline can't. You would get very short runtimes at maximum power.

Great work :thumbsup:. Like the single D-cell idea.

rayman

Very clean. Nice work.:tinfoil:

Beautiful work!


It would be a shame if an alkaline leaked into it though

Thanks for the nice comments, gentlemen!

Monkeyboy - I agree that an alkaline isn't the best choice. If I were making one of these for a flashaholic, I'd be more inclined toward a 26500 or 26650 or NiMh. In fact, there's a new 26650, a C Mag and an SST-50 sitting on the bench right now. :devil:

Your mention of drawing 3-4A has me a bit stumped. The driver limits the current at about 1.2A and that's that. While this is at the upper end of what most folks would want to pull out of a D alkaline, it should still yield plenty of run time according to the tests here:

https://www.candlepowerforums.com/threads/64660

Having said that, I'm not very far up the learning curve on the electrical side of this activity, so all input is welcomed!

Cheers!

The question of power draw comes down to the function of the driver.

The driver will regulate current going into the LED to the 1.2 amps. In order to do this, it is pushing it through the LED at it's Vf, which is approx 3 ish volts.

Power out to the LED = Vf x current = 3 x 1.2 = 3.6 watts (approx)

The power has to come from somewhere, and that somewhere is the battery.

V battery x Current = 3.6 watts (plus additional for driver losses)

V Battery = about 1 volt, so current from the battery = about 4 amps.

In general, alkalines are not designed to provide this much current, so run time will be very short. It is a very neat project though. It is also the main reason why you see so many lights bored to run 3 x AAs in parallel as the three of them can deliver more current longer than 1 D cell, especially the Li enhanced energizers and R NiMH and NiCds.

HarryN:

I see your point. My measurement of 1.2A is at the tail cap, so isn't that all of the current that is coming out of the battery?

I do get the point about running batterys in parallel. Like this one I built a while ago: https://www.candlepowerforums.com/threads/257077

David

That's a fantastic build, really good looking mag. Well done. Can you share some more details on the tail cap switch mod, it looks very clean, nice machine work all round.

I think this is what confused us, when you wrote..

saltytri said:

A single mode boost driver powers an XP-G R5 at 1.2A.

Click to expand...

Which is not the same as ..

saltytri said:

My measurement of 1.2A is at the tail cap, so isn't that all of the current that is coming out of the battery?

Click to expand...

With 1.2A at the tailcap you would be getting around 700 to 800mA to the LED at a guess. Which boost driver did you use ??There's not many that can do that much from a single cell.

Also, how did the reflector work with the XPG? Was is better than the std mag reflector?

Thanks for taking the time to share your work.

that is great work...very nice craftsmanship.

Very nice! :twothumbs for the great work!

Nice work David! :thumbsup:

Depending on the vf of the emitter, 1.2a at the tail is likely to be less than 500ma at the emitter. Which driver are you using?

Depending on the vf of the emitter, 1.2a at the tail is likely to be less than 500ma at the emitter. Which driver are you using?

The driver is one of the "NJG" units that seem to turn up regularly from the "discount purveyors." It don't have any other identifying data except that it is rated at 1.5V to 4.5V input. It did breadboard the circuit before installing it. My bench DC supply only goes down to 1.2V but at that input I got 1.2A at the tail cap, the same as with 1.6V input. So, I figured that it would do for a single alkaline. I know it's not likely to win a prize for efficiency but the goal was to make a nice light that someone could put a WalMart battery into and be good to go.

I'm starting to get the message that there is a lot to be said for first-rate drivers like those from TaskLED and the Shoppe. Are you out there, Justin Case? You'll be glad to know that someone is listening. While we're on the subject, what would an appropriate driver be for one 26650 and an SST-50? That would be a nice setup in a body like this.

Essexman said:

Can you share some more details on the tail cap switch mod, it looks very clean, nice machine work all round.

Click to expand...

Essexman said:

Also, how did the reflector work with the XPG? Was is better than the std mag reflector?

Click to expand...

The only Mag reflector on hand that has the tube cut off is one that I tried to sputter. It was OK but more diffuse and not as bright as the metal OP one from DX. I didn't try a smooth Mag reflector. Incidentally, this is NOT the one to buy. DX has similar units that can more easily be made to fit a Mag. The ones to look for are not entirely conical (on the outside, of course). There is a section that is cylindrical, which means they can easily be held in the lathe chuck to turn off the threads (which are too big in diameter to fit in the Mag). The one I used has to be gripped by the threads in order to turn the threads off – a very ticklish operation.

Here are some photos of the tail cap.

This is very easy to do – if you have access to a lathe! Threads are cut inside the tail cap and the concave surface at the back is flattened out. Corresponding threads are cut on the end of a piece of round stock. A center hole is drilled and bored in the end of the stock and a shoulder is cut in the hole to hold the switch in place. The threaded portion is then parted off to make a disk with a threaded edge, i.e., a retaining ring. The switch is a "cheap import" that has had the threads turned off to make it fit nicely in the retaining ring. It's no great shakes but it was on hand so I used it. A McClicky can be retrofitted when I get one.

NICE BUILD!! I think if you bored it a little, and went with a 4 X AA holder with a linear or buck drive you would be able to push a little more current to the emitter.