It’s been a busy spring around here. Lots of activities going on and not a lot of documentation, as one would note from the lack of activity and the prevalent chirping sounds here.
My friend Alan got a taillight from this place called jitensha studio. It’s a cute japanese bicycle parts and accessories company that specializes in prominent french aesthetics. The taillight is dynamo powered, and is designed to mount on the seat tube and be visible through the seat stays. Peter Weigle does this pretty commonly with his custom builds.
My initial impression of the Kimura taillight was one of quality. It is very nicely machined, the joint where the two parts of the housing thread together barely visible. The threads are tight and there is a thoughtfully placed o-ring for weather sealing. Getting the two pieces apart is a little tricky, as the o-ring creates quite a bit of friction, and the curved smooth surfaces provide a dearth of options for grip. I find that gripping the small side with a tacky surface (bicycle inner tube, for example) creates enough friction to easily separate the two pieces. Inside is a little epoxy-encased combined LED and driver in a slick black cylinder. Compact, weather sealed, and unable to be tampered with. The top side, near the LED emitter, has an electrical contact, making the housing/bike frame one conductor, and then the little screw in the back is for conductor #2. It is all held in place snuggly when the back piece threads into the main housing. The lens itself is internally ringed for diffusion and similar to the Luxor models we like so much around here.
I hooked it up to a little dynamo tester I have (actually an ancient un-built sturmey archer dynamo hub) to assess brightness and beam shape. This light has no stand-light, and adding one is not a possibility due to size constraints. It is not as bright as I would like it to be. It produces a comfortable glow which you can look directly into without any discomfort. The lens does a good job at distributing the light from the emitter without any major hotspots. It has fairly good side visibility too, thanks to the concave lens shape.
Over all, it’s a very pretty light and one of the only commercially available options for seat-tube mount dynamo powered taillights. Its lack of a stand-light and brightness, however, limit its utility pretty severely.
Nice post! Really like those Kimura lights, but always wondered about performance. Neat to see how they get put together. Do you think the lens is injection moulded or is it machined out of a piece of translucent plastic?
Kina – This light looks very nice, but your concerns with lack of standlight and sufficient brightness are valid.
In your review you mentioned that the plastic housing is “slick” and tamper-proof. Do you think it’s possible to build a different LED and standlight into this housing?
BTW, I am a friend of Corey Thompson and found your blog through his Picasa picture galleries. I’ve been very impressed with your work retro-fitting the vintage light housings.
I’ve done a few, but nothing as clean and tidy as yours. I was cannibalizing the guts from Busch & Mueller Seculite Plus fender-mount tail lights, which are pretty bulky. This really limits the minimum size of the housing.
I’d be curious to hear your opinions on re-fitting these Kimura lights. Thanks for your time and for sharing your process.
@Jeff: If I had to guess, I would say machined, or they did a really good job cleaning it up after the molding process.
@Dan: I met you a while back while you were down in Olympia, thanks for the kind words. The electronics in this light are tamper-proof and there really isn’t enough room to add anything but what was designed to fit. Definitely no room for a standlight. I’ve had a couple conversations with Mitch Pryor of MAP cycles down in Portland about making a small run of seat-tube mount taillights like this only better. We’re still thinking about what to do about the lenses.
Yeah, the lens problem still confounds me. I’ve been tinkering with a taillight design for a while now but the work ground to a halt as soon as I started pricing out getting a red tinted lens fabricated. Even decent quality 3D printing to produce a reasonable looking finish was cost prohibitive, let a lone proper injection moulding. I wonder what Tony Pereira uses with his taillights.
Hi. The Kimura taillight is beautiful and appears very well built. I was wondering if the LED module can be replaced with a modified version of the Jan Heine/Compass Bicycles LED “bulb” designed to screw into a standard socket. It’s very small and has a small standlight capacitor. Not perfect, but adequate. From your photos it appears as though it would fit with some slight mounting modifications.
Also, is the frame mounting stud M5 or M6?
Thanks for presenting your analysis of this light, I may have to consider it for my next project.
The frame mounting stud is M6.
As for what Tony uses, I’m not sure. I think Peter Weigle uses these lights as a starting point for his designs: http://www.ebay.com/itm/Baby-Bullets-Red-Replacement-Glass-Lens-Kit-/280180820682?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item413c140aca#ht_1180wt_906
Mitch has used these lenses before: http://www.bikeworldusa.com/product_info.php/cPath/124_25_51/products_id/1288
Regarding using one of Jan’s LED retro-fit bulbs…They might work. I haven’t seen one up close, but they would have to be the same size as a normal bulb, so there would be room, if you could finangle a way to mount the bulb that was electrically isolated from the rest of the housing, which honestly sounds like more trouble than it’s worth. If you’re going through the trouble to spend this much on a taillight from japan only to tear its guts out and put more money into, maybe you should look at other options.
I’m in the process of trying to solve this lens problem, I’ll report back when I have some answers.
Hi, I’m sorry but I’m not familiar with the term stand-light… What does this mean?
Standlight: It is a feature in a lot of these dynamo powered lights that store charge while you’re riding so that when you stop and the dynamo is not outputting power the light will still shine.