LED Light Conversion Part 3

Back in November of 2017, I wrote a post on converting an old Soubitez halogen headlight and a tail light to LEDs. The details are here. I was dissatisfied with the performance of the resulting conversion and over the next year attempted to find low cost and low complexity means of improving the results which are outlined here in a post from December of 2018. The results were improved but in my conclusion I commented, “The changed front reflector is a considerable improvement in beam shape but the 140 Lumen output of the LED may simply be too low for serious use. The up side is that things are better and still look period correct.” However, “better” is not the same as satisfactory. The beam intensity was still too low and the headlight beam itself did not fully cover the immediate path ahead because it seemed biased to the left.

My immediate thought was that if 1W and 120-140 Lumens of the Nicelite LED insert is good then double that should be much better and would still leave plenty of wattage to run the taillight. When I again consulted the Nicelite product page for dynamo lights, I found the following products:

None was of greater than 1W unless it had DC or some other polarity issue. Puzzled, I wrote Nicelite/Reflectalite and received a courteous and prompt reply explaining that older, traditional type lights such as I was converting were made with largely or completely plastic housings often with a small brass bulb mount or an entirely plastic mount. These designs lacked sufficient metal to act as an adequate heat sink for an LED of greater than 1W capacity. Higher output conversion LEDs such as a 2W would simply overheat, fail and, quite possibly, melt the the light housing or reflector. He went on to share with me that there were no plans to produce a higher powered LED conversion either now or in the future. So much for more Lumens from the current Soubitez reflector and housing.

Since more light was not an option, better focused light seemed to be the only route to improvement left. The problem with the Soubitez headlight was that the mounting base was plastic unlike the earlier Soubitez which had a crimped metal mount as shown in the photo on the right. The TA rack mounted on the C 37 attached to the Mafac Competition pivot bolts but did not have a mounting attachment rod with which to attach the light itself. That job was handled by a cro-mo custom made lamp bracket as seen in the photo. Unfortunately, the bracket did not fully clear the support rod of the TA rack and the result was it slightly tweaked the alignment of the lamp from straight ahead to a leftward bias. That was not a problem with the original chrome Soubitez shown in the photo as the steel mount was easily twisted to align straight forward. Unfortunately, the larger lamp with its black plastic mount was twisted left and this was wasting useful light and it could not be bent to align straight forward because the cro-mo mount was too strong to bend without damage. Realistically, I either had to replace the large Soubitez with another steel based lamp or change the TA rack/bracket arrangement to retain the reflector.

A search for a used, NOS or contemporary headlight that had a steel mount provide fruitless. The ones available had lens like my original, chromed, poorly performing Soubitez or had plastic bases like my large Soubitez with the added disadvantage of requiring a ground wire connection and attachment rather than the single wire with frame as ground format of older headlights. Since it did not look possible to find an alternate lamp, it seemed I would need to find an alternate rack on which to mount my current lamp. This was no small issue.

The original rack was made by TA in France about 35 years ago. It is steel wire, brazed together and then chromed. The racks are excellent for supporting handlebar bags on randonneuse bicycles without using special braze-ons and command used prices of at least $50 US if in good condition. Not only are they still in demand, they are found in multiple different formats some of which are rarer than others and therefore pricier. The photo to the left is my then current one showing the mounting struts and brake center bolt attachment point. There are two other models in that style and they differ by having a dropped strut that hangs down on the left side of the rack to permit the attachment of a headlight. They differ in that one version has a brazed-on threaded M5 socket which permits a light to be bolted directly on along with an anti-vibration washer to prevent slippage. This can be seen in the photo to the right.

I have used this type before on a Peugeot PF 40 and the mounting is simple, robust and secure in normal use. The wire mount is flexible enough to allow bending to fine tune headlight alignment but stiff enough to avoid vibration in the light field when riding at night. This was the version I was looking for when I decided to look for an alternate TA rack based on my previous experience with the Peugeot and the ease of mounting. Checking on line with both EBay and vintage bike stores, I found prices for poor condition racks needing re-chroming at around $60 -70 US. Good condition racks ran up towards $100 US. This was not the solution I had anticipated when trying to solve my headlight problem.

An alternative TA rack looks the same with the dropped headlight support rod but it lacks the braze-on M5 screw mount. Instead, the L shaped rod is plain and unthreaded like the example seen to the left. This requires a special clamp on style of compression mounting that allows the light to sit above the rod but which does not seem as secure a mount as the threaded version. This format looks like it will rotate if the headlight is too heavy or not tightened down thoroughly. Searching on line with EBay reveals that the rod type are in the $55 – 90 US range which was even worse.

Thankfully, the problem was solved through a contact on Bike Forums who had a front TA rack with light mounting post for half the price of the commercial offerings and in very good condition. Furthermore, the post was already threaded with an M5 thread for the previous owner’s application. A price was agreed on, PayPal payment made and the rack delivered by mail.

A quick clean with Autosol and the rack was shining. An attempt to quickly remove the previous TA rack and mount the new one failed because the fender mount at the fork crown required attention and alignment so up on the work stand and then finished. Once the rack was mounted and the nuts and bolts all tightened down, I trial fitted the Soubitez headlight to the mounting strut on the rack. The threaded area accommodated the mount but there was no room for jam nuts or the outer Nylock that was needed to hold the Soubitez in place. The thread needed to be extended.

Out came the tap and die set as well as the cutting oil. A trial fit confirmed that the thread was M5 so I assembled the M5 die to the handle, lubed the die, the threads and the chromed rod and carefully threaded the die onto the rod. The fit was much smoother than the dry trial fit and the die cut into the chromed rod readily, to my surprise. The original thread was about 1/2 inch long (1 cm) so I doubled the thread cut to just over an inch or slightly more than 2.5 cm. Once the swarf was cleared and the tools put away, I brass brushed the threads on the rod to clean them and refitted the two inner jam nuts to act as a stop. I added an anti-rotation washer, the lamp and then another washer and the 10 mm M5 Nylock nut. Everything bolted up perfectly and there was a slight excess of threads. The details are in the labeled photo to the right. I tested the light with the generator and the front and rear LEDs lit up exactly as they should and then, later, did a preliminary lamp aiming and adjustment.

With the new TA rack with the drop strut mounting rod, the aim of the mounted light was directly toward the front with no lateral offset to the left. Once weather permitted, I took the bike out on exactly the same bike path as previously had been the case. Riding showed a tight beam that had little throw to either side and lit the path from edge to edge. The Soubitez lens and the aligned bracket, refreshingly, put the light where it needed to be.

Conclusion: The light beam realignment provided by the new TA rack bracket allows the most effective use of the light available. The light remains bright white and is highly visible from the front and the rear stand-light functions very well. This is probably the best it will get with upgraded period technology and is now satisfactory for normal riding in level or slightly rolling terrain. Fast downhills? Still not recommended.