NR Trail Rat --> LED mod

[MMACH 5]

First off, I'm really not lazy or trying to get others to do my homework. I have been researching this for over a week, but I'm not an electrician. All the information out there has been really overwhelming, so now I just need someone to tell me exactly what I need to buy for this conversion.
I've asked at some lighting and electronics forums, but I really think they are tiring of my ignorance.

I've got a NR Trail Rat Select, so it runs a 15w halogen off of a 4.0 Ah-6 Volt NiMH battery. The problem is that my commute is anywhere from 1.5 to 2.5 hours, each way. This thing conks out at just under an hour and a half. I don't need the full brunt of the 15w halogen except on the parts of my commute where there are no street lights.

In an effort to extend the run time and possibly drop my backup light, I'd like to change out the halogen bulb for a Cree XR-E. If I can hook this up with a dimmer switch, I can run it at half or 1/3 power for most of my commute and just kick it up to full power when I need it.

Here's what I know I need to buy, so far:
1. RC helicopter engine heat sink
2. 1/2-inch copper end cap
3. Cree XR-E LED emiter

Here's the stuff I'm getting conflicting info on or I'm just not clear which option to buy:
1. A reflector (I want one that will focus the light on a fairly narrow area)
2. An optic of some sort (this is different from the reflector, right?)
3. A BuckPuck (there's a slew of options here. I think I need the 6v/350 mAh setup) which side of the circuit board does this wire into?
4. A circuit board (is this where the "dim-ability" needs to be?)
5. An external switch (or can I modify the Trail Rat's "On/Off" switch and make it work as a dimmer?)

Thanks

[VaughnA]

If you don't need the 15w power and just need a bit more run time then a good interim solution is drop to a 10w bulb.

That being said, I just finished my first homebrew LED system and I'm hooked. Check out the MTBR.com bike board, there are a ton of great designs there that should answer your questions. I'll be posting my personal hack in the next couple of days.

[Pig_Chaser]

Your buck puck (or whatever driver you choose) should be capable of driving the leds at different current levels; That's where the dimmability comes into play.

[n4zou]

I am guessing you want to try and simply replace your halogen bulb with an LED and try to continue using the Battery, housing, and reflector. This is very difficult to do while providing a good beam pattern and proper voltage for the LED driver. In most cases it's easier to build an LED system from scratch. You'll need optics to match your LED. I use Luxeon Fraen Elliptical Beam Lens With Holder with a Seoul Semiconductors Z-Power LED Emitter (U-bin). The Seoul LED works perfectly with with Luxeon optics and is much brighter than Luxeon LED's. The Fraen Elliptical Beam optic lens and holder provides an exceptional pattern for road use much like motor vehicle headlights. Assembly of the heat sink, LED, and Lens holder is simple. Just drill holes in the heat sink to match the holder legs and two holes to pass the wires through to the driver. I use a little hot glue around the holder legs and heat sink to hold the assembly together allowing easy replacement of the LED when the next generation of LED's become available. Here are the links for the stuff you need to build your LED light.
Optics:
http://www.luxeonstar.com/item.php?id=462&link_str=121::125&partno=FHS-HEB1-LL01-H
http://www.electronics-supply.com/admin/images/fhs-heb1-ll01-h-l.jpg
LED:
http://www.dealextreme.com/details.dx/sku.1445
http://www.dealextreme.com/productimages/sku_1342_1.jpg
Driver:
http://www.dealextreme.com/details.dx/sku.7425
http://www.dealextreme.com/productimages/sku_7425_1.jpg
Note: This driver allows you to reuse your 6-volt battery.

The above holder, lens, heat sink, and driver will fit in a 1" PVC plumbing pipe coupler available for less than a $1 in building supply and hardware stores. Here is a photo of mine clamped to my handlebar with an EMT conduit hanger.
http://i143.photobucket.com/albums/r154/n4zou/Hpim0312.jpg

[Ngchen]

If you replace the 15 W bulb with a 10 W one as another poster suggested, you would get 2.3 hr of runtime with your current setup. Something else that you might want to consider is to get a second battery, and/or build your own long-running battery. I am under the impression that building a water-bottle NiMH battery with ultracapacity 10 Ah D cells is not that complex. That would give you 4 hrs of runtime with the 15 W bulb you already have.

[MMACH 5]

Thanks for the links and feedback on this.
Here is my modified list:

Heat Sink (http://www.tedani.com/gwehs100-heat-sink-for-em100-motor-p-148.html) (shown in OP)
Copper cap (http://www.pexsupply.com/categories.asp?cID=145&brandid=) (also shown in OP)
Cree XR-E Q5 (http://www.dealextreme.com/details.dx/sku.2394)
3W circuit board (http://www.dealextreme.com/details.dx/sku.7425)
Reflector (http://www.dealextreme.com/details.dx/sku.5960)
I will also be using a lens from an old flashlight.

My question is about modulating the power output from the circuit board. I don't really need the strobe or SOS features, just High/Low/Off. Do I need to buy a switch with on/on/off functionality or does the circuit board change modes with an on/off switch that is turned off and back on quickly?

Thanks again.

[singlespeed10]

My question is about modulating the power output from the circuit board. I don't really need the strobe or SOS features, just High/Low/Off. Do I need to buy a switch with on/on/off functionality or does the circuit board change modes with an on/off switch that is turned off and back on quickly?



The latter, the mode is changed by flicking on and off the power. This board apparently does not have a "last-used-mode" memory as some other boards do.

[n4zou]

I will also be using a lens from an old flashlight.

Thanks again.

Your beam pattern is going to be very wide if you try to use a flashlight reflector and lens and your going to hate it. At the very least order this and use it for a reasonable pattern you'll be happy with.
http://www.dealextreme.com/details.dx/sku.3257

http://www.dealextreme.com/productimages/sku_3257_1_small.jpg

[polarflux]

FYI

I picked up on this thread looking for info to upgrade my NR Trail Rat 2.0. It looks like the landscape has changed a bit since this thread was active. Cutter has a an MR 11 boost kit using a cree triple XR-E r2 binned emitter paired with an optic. The optic size is 35 mm, the same as the existing lamp in the TR 2.0 (or any other MR11 sized lighting housing). I ordered the light kit, plus a heat sink. I am not sure how it the parts will all fit into my existing light housing, but I will find a way (will post pics of the process when I get the parts). Also, the boots electronics (Fat Man) should work with the 6V battery just fine. I have not decided what current I will run the system on, but the XR-E R2s are bright enough that I can run the system at 500 or 750mA and have enough brightness for most everything and still have better battery life (and brightness) than I have now. If I do not have enough brightness, then I might use a different battery (maybe LI) and switch to a buck system. All in all, the parts that I have coming should allow a pretty straight forward upgrade to my old trailrat providing. We'll see. I'll post followup pics, etc.