Old School Headlight Housing Needs Upgrade

[boltgunner]

My 19 year-old daughter just bought her a bicycle to ride to and from work, and she opted for this headlight -

It uses 2 C cells to power it. It cannot light up much at all. I wish to gut it and keep the C cells for power, and add whatever is available (where you all come in) for the light source. Please keep it simple - now that I gave up the house and garage for single life and an apartment, my current workbench is the countertop next to the kitchen sink. :broke:

 

[BrianMc]

IMHO you should save time, effort and money and buy another light. Especially if you did not keep your soldering iron, Multimeter, files, rasps, drill, and maybe a Dremel. You will miss your vise and you may well spend more than simply buying a light.

Also I recommend searching theis forum to learn more about what you are letting yourself in for. This can become addictive. You have been warned.

I came across a blog but it would not turn up in the first three pages of several Google attemps, so maybe you'll have a go to find it. If memory serves me well, the author put a CREE XR-E Q bin mounted on a star in one of these. It was similar to the link below in general. The reflector was the heat sink to keep the LED from overheating so he had cut the back off the reflector and make an aluminum disk to fit the LED on its MCPCB. He thermal epoxied (expensive but essential for heat transfer) it to the reflector and the MCPCB the LED was on, to the disc. Two holes for leads went to his driver.

Found this link. Better than the original bulb but not by a whole lot and just general guidance to battery and approach.

http://www.howtofixbikes.ca/2007/01/white-led-vintage-bicycle-headlight-how.html

Good luck.

 

[boltgunner]

Thank you for your thoughts. In the end we will likely get a better light. I did manage to hang on to my tools, though. I may still try to tinker with this light in the mean time - apartment living is so boring so I have to find something to make with my hands to help keep my mind useful.

Isn't it true that LEDs have a narrow beam, and that placing just any LED into a reflector doesn't assure superior performance, since most of the output goes straight ahead vs. into the reflector? Are there LEDs that have a wide beam?

 

[vtunderground]

The simplest option would be to try to find a drop-in LED "bulb" to replace the current bulb. Does the bulb have a threaded base, or a regular PR-style base? If it's a PR type bulb & has correct polarity (+ goes to the tip of the bulb) you could buy a Dorcy LED "bulb" & replace the stock Luxeon with a Seoul P4 LED. This should get you 40-50 lumens and a whole lot of runtime.

 

[BrianMc]

Good about the tools, as that is pretty much a deal breaker.

I recommend you search this forum for more detials on this 'short' summary as I am no expert, just a decent gleaner of info.

Unlike the incandescent bulb that you will remove, LED's beam over a much narrower set of angles (not backward, for example). Within Power LED's there is a fair range of beaming.

Power LEDs like the SSC P7 and the CREE MC-E have multiple dice (4): each die is its own LED. Because of the size of these and the multiple light sources, these are known as being 'floody'. That is because they disperse their output comparitively evenly from 0 to 180 degrees.

Floody beams are favored to find potholes, and not annoy oncoming motorists as much.

The XR-E R2 on the other hand, is a single small die and is known as a thrower in that the majority of its light is in a fairly narrow angle of straight ahead.

Throwers are lifesavers on fast Mountain bike descents and very handy as a high beam for roadies who hit high downhills speeds on their route/commmutes.

The XP-G a large single die, so is logically enough, both a thrower though not as much as the XR-E's, and floody, though again, not as much as the MC-E or P7.

This is a new entry as of late October and unique in its combination of beam and output per watt of power.

You can find the tech sheets for these on line and they have the light intensity by angle charts. Lower and wider is floodier, taller and spikier is a thrower. Astrodome versus Washington Monument versus a hybrid of the two in the case of the XP-G.

The physical size in height and diameter of LEDs mean different lenses and reflectors are optimal for each LED. You don't want to spread what light you will produce widely or you will just have the same weak light as the incandescent spread out side to side. You don't want a 6" hot spot either but you are not going to be too worried about optimal. Your goal appears to be a lot of reliable light cheaply using a shell and mount you have.

Moving the light source relative to the focal point of the lens can improve or worsen the light pattern considerably. So an adjustable design for mounting the LED assembly to the reflector or one you can shim/mod easily would be a good idea.

In that regard, following someone else's path is a highly recommended way to save time and money. (I assume that is why you posted). So I suggest while you wait to see if someone reading this forum has done so, you google 'Classic Bicycle Headlight LED conversion mod' (or whatever comes to mind) to see if you can find the Mountain Biker who showed beamshots and claimed using one while night trail riding and hunting. If that blog is still accessible, he had a good pattern using the original reflector. It may not be the best possible, but good enough is good enough given your needs.

Another possibility is to use a flashlight drop-in unit especially if the current reflector is deep enough that the 'pill' where the LED is mounted in the module will be the contact point for the reflector, allowing heat transfer. If the module reflector doesn't extend beyond the reflector cover/lens, you are in business. DX appears to have a following for these but delivery is usually several weeks or more. The last time I checked, the XR-E R2 modules were about $10, and the MC-E and P7s were about $25. These come with driver modules adn you battery choice must fall within their input ranges. Some are multi-mode with maybe three levels of which the lowest is close to useless for seeing to ride, and usually two flashing modes which are handy in daylight especially dim days for being seen. The Module route would take care of all but the battery and figuring out how to mount it and handle the heat. Another advantage with this is you can move it to a flashlight body and mount maybe as a backup light.

There are current threads here on using the modules, and the various LEDs, batteries and drivers. I suspect specific questions to posters in those threads to any questions that remain unasnwered after reading the thread will be fairly received and answered.

Since flashlights often have a single LED, though may are multiple, and you are going to have about the same battery storage and run time as a flashlight, so there will be good info to glean from the flashlights too. Just google in this forum.

I found 50% of the fun was figuring out what I wanted to have when I was done, figuring out the best affordable approach. Another half of the fun is in solving the niglies of the builds with the tools at hand or affordable additions. And the last half (Tappet Brothers Math), is in the beamshots and riding.

 

[boltgunner]

To vtunderground, thanks for the reply - it is a screw-in bulb.

To BrianMc, I appreciate seeing the suggested part numbers - gives me some idea where to start. There are as many solutions as there are postings, and I think I have something to go on. BTW, what is a good supplier of these parts? Also, is there some general guideline as to how much heat sink you fab for a given power consumption?

 

[BrianMc]

Suppliers:

I think there is a thread database here somehwere, if not there is one in MTB forums. As to recommendations, well how many of us have comparitive experience with them all?

From what I read here, and elsewhere, it looks like DX and Kaidomain are the low price suppliers. DX has free shipping, but you have to wait for shipment maybe longer than your patience allows. Apparently DX is decent on warranty issues, but the delays can be a bit unnerving. Haven't seen enough on Kaidomain to form an opinion, other than I did not want to trust my bike lighting to the lowest bidder, so to speak. My impreession is that they may not carry the most latest or most desireable version of some emitters.

I didn't want to spend man-weeks building my lights and have the driver be an issue. So I went with what someone in one of these forums called the 'Cadillac' of driver suppliers: Taskled. American designed, beautifully assembeled, well tested, great customization for power, battery, temperature monitoring, and very flexible in operation. They are overkill for your application, I think. Also, since one of these ($30) is half the price of a Planet Bike Blaze 2W or decent CREE XR-E R2 flashlight, and either of those would be a decent solution for your daughter's bike. I am extremely happy with my experience ordering from Taskled. If interested:

www.taskled.com

I also ordered parts from Hoffmanamps (EL34) because he had specific parts for the kind of light I was modifying. The experinece was excellent. He has the SSC P7 BIN C on a star, wiring, heat shrink, small hardware. You can also build a light by makng your own kit up using his parts if you wanted to forego the Classic Housing you have. Cost for a light kit will be $70 on up depending on what more general parts you need and which mount(s) you buy.

http://www.hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&thispage=PartsLed.htm&ORDER_ID=!ORDERID!

My last supplier I have experience with is Cutter. I ordered the soon-to-be-back-in-stock XP-G R5 and supporting lenses. They have a deal to ship free on orders of $100 or more until 01/31/2010. One item I ordered was no longer available and they changed the website to remove it as it was gone when I got the e-mail from them about the problem. Fast fix. They elected to still ship for free though the order was now less than $100 and would refund the difference. Really nice of them about the shipping. I opted to add wider angle versions of the LISA2 lenses (as I had seen no tests at that time) rather than the hassle of a credit card refund over the internet, which came to $.90 less and told them they could keep the change. The exchange rates had changed from my unrefreshed page and the rate listed on the change-order day. They ate the difference. They are not the lowest price, but they appear to have some of the best support I have seen. Good people who work hard for their (our) money, it appears. The order is expected in a few weeks. If I read it right, when the XP-Gs arrived CPF members had preorders which were late to be filled (looked like a supply issue to Cutter NOT from Cutter), but they got the better R5s instead of the R4s, much to their delight. They carry the CREE MC-E, XR-E, and XP-G LEDs, among other CREE emitters mounted to many MCPCB's. Others here also have good things to say of them, but low prices is not one of them.

http://www.cutter.com.au/index.php

One CPF members limited take/experience.

 

[boltgunner]

Can you tell me who offers a 18650 holder that I can wire to, please?

 

[BrianMc]

Since I have a battery and chargers so I didn't need any, however, the hoffmanamps site (I gave you in a previous post), is one source if you scroll down that page, there are holders, batteries, and even a charger that will save waiting for the slow boat from China for that item.
:whistle:

Googling inside the forum (the Google Search at the top of the thread) is a highly recommended way to get answers to specific questions like this one. Many questions you will have (except this one about putting an LED into a classic headlight), have been discussed here.
lovecpf

For example, a search on 18650 battery holder in this forum gave this thread off the top:

http://www.candlepowerforums.com/vb/showthread.php?t=209968

Which when I shot to the bottom most recent posts, seems to have a couple of suggestions.
:thumbsup:

And this a thread asking your exact question also with some suggestions was number two:

http://www.candlepowerforums.com/vb/showthread.php?t=102074

:twothumbs

We all occasionally post without thinking it through or doing our homework. I think it is a rule of the forum that each of us must design do our own research into whether your question has already been answered in this forum. That is why the old threads are searchable. If you come up dry looking for your answer, ask away! That is one reason for the current threads in the forum. However you will find few people respond to your posts, if you don't.

:poke:

See next post about your heatsink size question.

 

[BrianMc]

Now, you had a question before about heat sink size. This is one of those topics strewn throughout the forum that you could have read and still been confused about. The information is hard to extract.

This is my understanding and it may have errors. You use it at your own risk.

There is a fair discussion of heat flow in flashlights (Google it). Flashlights are cooled by your hand and bloodstream so a 10W LED flashlight at something like 10-15% efficiency is 8.5 to 9 watts of heat and about the limit of what a person can hold continuously.

The flashlight presents the thermal management problem simply. Heat wants to flow from hotter to cooler (Newton's Third Law, I think). The LED junction temperature is the hot spot and the interface with the air is the cold side. For longer life, higher light output, and more efficient conversion of battery power into light requires lower junction temperatures. Each LED has a maximum recommended temp above which its life is much reduced. Anything that reduces the resistance to that flow of heat from the LED junction to the air, allows the LED junction to be cooler for the same temperature at the air-body interface. The heat sink is not to store heat, but to transfer it to the body of the flashlight and to the hand of the user.

Bike lights have the advantage of air cooling, which reduces the outside area needed and the heat sink size to keep LED junction temperature in operating range. Cyclists can run the body of their lights to 'too hot to touch' at a red light, for example, then cool it off again once rolling. I have seen recommendations of about 7 inches of finned heat sink per watt for LED's in house lighting where there is no air movement and maybe a shade or housing messing up air flow. I also saw an estimate of 2-3 inches per watt for bike lights at 10-12 mph or less and to allow for minimal increased temps at red lights. The MagicShine has about 1 inch of body per watt of heat, and though it has a decent sized heat sink/pill, it does not have a lot of contact area between them to transfer heat to the body. Several people have triple or quad 3 watt CREES or 10 W P7's in MR11 housings with about 1" of area per watt but with better heat sinking to the body. This appears to be about as low as you can go with current LED's. Since LEDs last tens of thousands of hours, whether designs with 1" per watt air interface damage the LED at speed on a bike, is not clear. They are certainly lasting months and even years. Their light output per watt is likely closely linked to how well their heat sinks move heat into that minimal contact with the air and as important, how well that body transmits the heat to the air.

So a larger body allows for more air contact but increases the distance for the heat to go to get to the air. Air movement reduces the boundary layer insulation effect and strips warmed air away.

A bigger and better contact of the LED to the heat sink and of the heat sink to the body and of the body to the air makes for a cooler and happier LED. While silver and gold are slightly better (5% for silver over copper) than copper and aluminum in thermal conductivity, the last two are more affordable. Copper has about a 60% higher conductivity than aluminum so is often the metal used in MCPCBs. It is heavier and more expensive. Anodized aluminum is better at transfering heat to air than polished aluminum which is better than copper. Steel, which is likely what your Classic Light's shell is made of, is about 60% less conductive than aluminum and chrome finishes are even less effective at transfering heat to air than bare copper. You have so much area though, and that is not a big issue. The comparitively poor conductivity in the steel and its thin guage means it won't spread the heat out as well as if it had been thicker aluminum.

Thickness helps to a point of diminishing returns. For a pill in a flashlight the rule of thumb is that the thickness should be between 1/4 and 1/2 of the distance of the LED to the body. In the case of the big ol' light you have, that would be ridiculous. It is a long way from the LED to the shell in your light, which is why another person used the aluminum refelector to move the heat from the MCPCB to the shell of the light. This may be adequate at 50-75% of maximum current to the LED which would reduce the amount of heat generated, and so the amount to move.

So the amount of heat (and light) you produce affects the amount of heat sink you need to transfer the heat.

So there are a lot of variables going in to the size of heat sink needed. It is not a simple question. The desire to have smaller, lower mass lights with more light and higher wattage are in direct conflict with each other and this makes bike LED lights fascinating.

Guides to heat sink design in CPF (IMHO):

1. Shorter thermal paths to the air are better but you need 1-3 inches per watt of contact to the air flow for a bike light.
2. Thickness helps up to a point, which maybe around 1/4" to 1/2" thick regardless of light diameter (from designs seen).
3. Metal-metal interfaces are best. Fewer interfaces is better. Thin layers of thermal compounds are best. So a milled single block of aluminum body/heatsink with the LED's soldered or fastened using minimal thermal compound or paste for the thinnest layer (1/1000 of an inch of so) to a polished area of the heat sink, is best.
4. Air is very bad in the thermal path as it is an insulator. Thermal grease is used to displace air for the sink-body contacts and can be used for MCPCB heat sink contact. Thermal grease is about 100 times worse than metal wheras air is about 100 times worse than thermal grease in thermal conductivity. Since resistance is conductivity times thickness, thinner is better. Polished contact points help in getting thinnner thermal compound layers and increasing the metal-metal contact.
5. Copper is a better spreader but seems most effective closer to the LED early in the spreading of the heat. Cheap plumbing copper pieces as compared to making something like them from aluminum stock, means that copper pipe caps are popular for one-off heat sinks for hobbyists, even if heavy.
6. Small lights make the above more important. In larger lights just getting heat from the LED to the body is enough of a problem.

I guess your light's shell is 3-4" in diameter and 4-5" long. That would be about 20 to 30 square inches not counting the bezel, which connects only at hinge and latch. I think your design issue is how to get the heat to that shell and into it not as much on optimal thickness or size of the sink. Cost of course is always a factor. So you have to balance cost, what you can build, optimal methods, and the amount of heat you need to manage.

Hope this helps. I also hope more experienced hands will correct me where I have erred.

 

[boltgunner]

Can I successfully power the SSC-P7 with the two C cells presently in the headlight housing without any driver?

 

[John_Galt]

No. You'll need some sort of Boost driver to raise the voltage.

If you went with two CR123 (inexpensive online, much better choice of battery, much more compact) you could buy a decent 2CR123 light and transfer the head into the light. You wouldn't be able to run it on high output without some sort of heat path to the housing, but you would be able to wire it so that it would work in the light.

 

[Linger]

Yes with a serious boost driver, but why?
Think, two 'C' alkaline cells have limited power available. You can try to drain it all at once (pulling 2.4A for a P7) but the result may be as useless as the stock model.
I suggest a more realistic approach - if she's cycling it would probably be good if the cells lasted for a little bit.
I took a 2C Cateye handlebar light, that had a 2.4v PR bulb, and modded it to a modest output led, still running off the 2C and the stock switch. I added a boost driver and an xre Q5 on a metal track (as a heatsink and support).
The driver is
http://www.dealextreme.com/details.dx/sku.10084
I used a Q5 i took from a light I upgraded, of course you could use any higher flux emitter (rebel 90 or 100, seoul P4 U2 bin, cree xpe/xre/xpg of Q5 flux or higher)
This driver has bright, low, and somewhere in there is a 'blink' mode which is fantastic making yourself visible (not strobe which is useless for cycling).
As I wanted a light would make the user visible, I didn't include an optic or reflector: the emitter sits up close to the stock lens, the result is a very visible unit that provides enough light for mild urban riding.
For cycling, aim at a long enough run-time to be useful. 2C's is plenty of power (especially if you use nimh cells) for a casual / transport rider. The high output cycling lights (2.4A and higher) come into play at higher speeds: if you're going to be as bright as a car headlight you've gotta be travelling pretty quick for people to respect you. Otherwise your daughter won't use the light b/c it's too bright and she feels it draws way to much attention when she's just peddeling along.

 

[JB01245]

Here is one that I just did

 

[znomit]

Sweet!

Driver?

 

[boltgunner]

JB01245, that is JUST what I wanted to do! :twothumbs

I basically have the same light housing!

I want to know PLEASE exactly what parts you used and where you got them!

I think this will take care of the daughter's night riding, which is usually for about an hour and is through neighborhoods, no off-road banzai riding, just mild aerobic riding!

:thanks:

 

[boltgunner]

:wave:JB01245, yer phone's ringing...

 

[JB01245]

boltgunner, sorry I haven't responded back, been super busy building lights and dealing with the family. Let me see if I can't draw up a quick schematic of what I did. I was able to maintain the functions of the original switch, so middle LED alone, upper LED alone, or both LED's at once. I used an older Kaidomain driver that I had laying around. The toggle switch originally controlled the ground loop. I reveresed that so that the toggle switch now controls the positive and the terminals coming off of the 3 way rotatary switch on top controls the ground loop.

 

[Steve K]

Re: Here is one that I just did

The light certainly looks nice. How did the beam work out? With the lack of any optics or lens, my guess is that isn't something that would be used to see the road.. ?

Similarly, how hot are the LEDs getting? The reflector might(?) be aluminum and capable of getting some heat away from the LEDs, but it's trapped in a steel housing, and steel is not a good thermal conductor. Of course, it's powered by a 9v battery, which isn't going to provide enough power for a significant bike ride anyway.

Any beamshots or run time data?

thanks,
Steve K.

 

[boltgunner]

JB01245, any progress on the plans/parts list? THANK YOU!