Romisen RC-T6 helmet light

[uhg_]

Hi,

Here's some more info sharing in the spirit of giving back to the community.

This was my first attempt at converting a torch (flashlight) into a usable bike (helmet) light, much inspired by a former MTB pal (thanks Gregor for, literally, helping me see the light!). Actually, these photos document both the original conversion of a Romisen RC-T5 (4 Cree XR-E Q4s) and the subsequent upgrade to the light engine and head of an RC-T6 (6 Crees).

I think this project pretty much maxes out the power that can be handled by this type of light (the internals are not ideally designed for heat management). But the lamp still has good heat transfer, merely gets lukewarm at full blast during cool weather riding and lights up the trails like a miniature sun - at a fraction of the price of comparable commercial systems. I am very pleased with the result.

All the parts layed out, before getting gooed/glued up. Had a shorter, fatter lamp body custom machined from aluminium. The head will still fit and run on the original body: but with the new, more powerful (Shark) driver, it will mucho rapido suck the life out of normal batteries!

Sigma Sport helmet mount: looks flimsy but in reality works really well

Test fit of the light in the mount. Looking good.

Epoxied together a contact pad for the lamp positive voltage spring plus a power plug holder, and epoxied those plus the power switch in place inside the new body. A veritable epoxy feast!

The RC-T5 light engine before modification

Ripped out the original driver/PWM combo (pictured) and replaced them with a Shark 1 amp boost driver

The four Crees rewired in series. Ran them with a somewhat sluggish 12V Nihm, ensuring that the driver would always be in boost mode and thus stay in regulation (i.e. Vin < Vf)

The finished item mounted on the helmet ... and ready to Rock'n'Roll. Choose an alu body so it would aid in cooling: it would be nice to loose the added weight, but so far this hasn't been a practical problem.

Moving on to the Romisen RC-T6 upgrade. Crees rewired in series again and custom "pill" cut from some copper tubing.

This time used a blue Shark with premounted Remora UI board. Covered the inside of the "pill" with Artic Silver epoxy to prevent short cutting the electronics: then potted the pill with tons of Artic Silver heat paste to conduct the heat away from the Shark. Also gooed the H... out of the rest of the head. (Apparently, Artic Silver is slightly conductive and Artic Alumina would have been a better choice. Learning never stops!)

Testing driving my nice, new lamp with my equally nice, new 14.8V Li-ion bottle battery. Very nice!

RC-T6 beamshot app. 1.2m from wall

For comparison Ultrafire R1 single rebel, single CR123A beamshot (wall)

Trail beamshot: Romisen RC-T6 (helmet mount). This light rules!

For comparison Ultrafire R1 single Rebel, single CR123A beamshot (trail)

 

[SkipH]

Since I'm the 1st to post after you started this thread.....

I can see only 2 of your pictures...the one of the 1st light mounted on the helmet, and the battery 'bottle' connected to the 2nd light.

So, at least for me, the picture links don't work.

:sigh:

 

[uhg_]

Apologies, seems there is an issue with my image host. Try here:

http://picasaweb.google.com/ulrik.gade/RomisenRCT6FlashlightMod?authkey=JIL7yLhTx78#

 

[bstrickler]

Holy crap!

Where did you get the helmet mount and how long did it take you to do all that?


Also, can you put up a parts list for us? I've been looking into doing a helmet mount, and I really like that idea.


For the aluminum heatsink, another thing you could've done for heatsinking, is use an aluminum rod, whatever diameter you need, then use a lathe to carve out a cavity for the shark and to let you stick the head of the T6 into, then lathe some fins into the aluminum to aid moreso in cooling.

~Brian

 

[uhg_]

Think I got the mount at www.bike-discount.de but it should be readily available anywhere they stock the Sigma Sport PowerLED, for which it was conceived. But any old mount you can get your hands on will probably do the job.

Having learned by doing the project, I now think I could probably complete it in a few hours, excluding milling of the custom body. However, in reality it took much longer than that.

I unfortunately have zero metalworking skills, and might kill or gravely injure myself just by attempting to switch on a lathe! Otherwise, I'm sure there would be no end of ways to improve this design.

I'm a bit tied up so can't provide a detailed parts list, but the pictures should give you a pretty good idea. Bought the torch and the clicky switch at dealextreme.com, the Blue Shark converter board and the Artic Alumina thermal epoxy at the Sandwhich Shoppe (http://theledguy.chainreactionweb.com), the battery (a 14.8V, 7.2 Ah Li-ion) at batteryspace.com, and the rest from either local electronics/hardware stores or by scavenging old junk I had lying around. Beware shipping and customs costs if you live outside the US, as these can quickly add up: batteryspace will ship with (slower but much cheaper) USPS rather than UPS if you explicitly ask them to.

One change I would make today would be to use a better connector, e.g. this one from batteryspace:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2898

Have fun!


PS: Running with a fresh charge, the lamp won't dim completely in between flashes in SOS mode, but the other modes work just fine. A small quirk caused by the high initial voltage on a freshly charged Li-ion battery, and compensated for by running the electronics more efficiently than with e.g. a 12V battery. A non-issue for me, but something to take into account.

PPS: Remember to take all necessary precautions when working with Li-ion batteries, as they may explode and/or burst violently into flames if mishandled. See e.g. the safety and handling instructions at batteryspace.com.

 

[bstrickler]

I can't find the helmet mount anywhere. I won't need the bike light, which is all I'm finding, but I don't feel like spending $160-$170 on a light I'm not going to use, just so I can use the mount. I tried looking on the website you gave me, but I can't find where the helmet mount is. I can probably make my own mount, though. Shouldn't be too hard.

~Brian

 

[uhg_]

This is the one I've got, at 4.95 Euro:

http://www.bike-discount.de/shop/k491/a8496/helmhalterungsset-fuer-power-led-black.html?mfid=8

I think they impose a 50 Euro minimum order limit, and you of course have to add shipping costs, so this may not be practical for you. But at least that should give you an idea. And as you said, there are mounts aplenty in the world (also check e.g. batteryspace.com, chainreactioncycles.com, niterider.com, jensonusa.com).

One further note: Use heavier gauge wire than that provided with the Sigma mount, which isn't really spec'ed for currents much above 1A (the lamp pulls around 2A at full throttle with a 12V battery) - especially if you extend the lead to reach e.g. a battery in your jersey pocket. I like the leads from batteryspace.com I referered to in my previous post but am sure there are other good options. And make sure the leads and connectors from the battery to the lamp match - on another recent project of mine, batteryspace were very helpful about custom fitting a connector to the battery that I preferred over the stock option.

 

[bstrickler]

This is the one I've got, at 4.95 Euro:

http://www.bike-discount.de/shop/k491/a8496/helmhalterungsset-fuer-power-led-black.html?mfid=8

I think they impose a 50 Euro minimum order limit, and you of course have to add shipping costs, so this may not be practical for you. But at least that should give you an idea. And as you said, there are mounts aplenty in the world (also check e.g. batteryspace.com, chainreactioncycles.com, niterider.com, jensonusa.com).

One further note: Use heavier gauge wire than that provided with the Sigma mount, which isn't really spec'ed for currents much above 1A (the lamp pulls around 2A at full throttle with a 12V battery) - especially if you extend the lead to reach e.g. a battery in your jersey pocket. I like the leads from batteryspace.com I referered to in my previous post but am sure there are other good options. And make sure the leads and connectors from the battery to the lamp match - on another recent project of mine, batteryspace were very helpful about custom fitting a connector to the battery that I preferred over the stock option.

After getting a better look at it, I'm thinking I can make my own helmet mount for the light, so I'll skip that part for now, lol.

I was planning on using at least 14g wire, and RTV'ing the hell out of any areas that can pose potential shorts (or figuring out how to add O-Rings). I always have my dad, who's been doing electronics/machining/other crap for 30+ years now, so if I have any questions when building it, I can seek his help, lol.

~Brian

 

[uhg_]

Good luck