Thursday, April 12, 2012

Raleigh-style headset mounted lamp bracket

While I patiently wait for the Bici Lux Nº58A prototype to arrive from Australia, I've had some time to work on my wife's 'new' Raleigh Sprite Mixte. Her 1966 Superbe was heavy and very beaten up, so I decided to replace it with my Mom's mid 1980s Raleigh Sprite, which had been languishing in the garage for the better part of two decades.  It cleaned up beautifully and the paint on the frame and fenders still looks great, with only a few scuffs and scrapes and no rust.  I upgraded it with a new wheelset, including a Sanyo H27 hub dynamo from the nice gentleman at  Long Leaf Bicycles.  Despite the restoration being more of an upgrade to modern parts, I wanted to use an original Sturmey Archer lamp set (upgraded with modern LEDs, of course, both front and rear, and a standlight).  My wife's old Raleigh Superbe had one of the nice Heron-style headset mounted lamp brackets.  These are plentiful and can still be purchased as NOS:




Original Raleigh Heron bracket


A few weeks ago I finally got around to mounting the lamp set and started by popping off the stem, placing the bracket in the headset stack and slipping the lamp's bracket over the Heron mount. But, lo and behold, the bracket was too short, resulting in the butt of the lamp jammed up too close to the stem's handlebar mount.  Turns out, the later model Sprite's used the modern forged aluminium quill stem, which is shorter and stubbier than the older chrome plated stems.  The stubbier geometry was the problem and the original Heron bracket simply wasn't long enough.


Since the bike itself was free (thanks Mom!), I decided it would be worth investing a bit in getting the perfect lamp mounting solution. To accomodate the 700c wheel size, I'd already had a custom drop bolt for the rear brake machined anyway, so why not go to the trouble of custom fabricating another part?  If that's not true love, I don't know what is.  


I've been busy designing a sheet metal bracket for my headlamp prototype, so I thought I'd have a go at making a longer Raleigh-style headset mounted lamp bracket.  My limited manufacturing experience has been restricted to CNC machining, so sheet metal design was new to me.  Essentially, you design a flat part and then modify it by bending.  If, like me, you're using cheapy prosumer CAD software, then the fabricator needs to 'unfold' your part to get a flat 2D profile again, which now accounts for the deformation caused by bending.  This unfolded profile is laser cut and then bent on a press brake.  Here's what I came up with:


First, the 2D profile:






and after bending and rendering:


The lightening bolt is, perhaps, an unnecessary frill, but I was inspired by the old JOS logo and couldn't resist.  For fabrication, I used a nice place in Scarborough that was one of the few places that was happy to do a single piece for a reasonable price (in this case, I got two as they were unhappy with the forming marks on the first one they fabricated).  Half of the places I emailed never got back to me, so kudos to Questa Design for working with the little guy.  Here's the custom bracket compared to the original Raleigh Heron bracket:


Custom long bracket and Raleigh Heron headset mounted lamp brackets
Here it is mounted on the headset:




And with a vintage Sturmey Archer headlamp:






All seems well, although I need to get it chromed first before I finalize the installation.  The only thing I'm a little worried about is how easily it will get knocked out of alignment. The orignal bracket had a keyway that interfaced with a groove in the fork thread to prevent rotation.  The Sprite's fork thread has no such groove, so the only thing preventing rotation is the headset nut.  Hopefully a bit of Loctite or maybe even a rubber washer will prevent unwanted rotation of the bracket.

2 comments:

Joey Korkames said...

I've been using through-hole eyelets on my custom racks and head/tail-light brackets since I've had lots of bad experiences with the square-rail handlebar brackets that are the new "standard" with aftermarket plastic lights. They are as strong as this metal rail, but add an un-needed axis of lateral rotation that you have arrest by over-tightening the mounting bolt.

I actually fitted one bike and light in the past with a "weaver" rail, which is normally used for mounting scopes and lights to guns. I like your retro rail much better!

Rob said...

I like your design I would personally mount a bit higher on the clamp so if bumped it wont ding underside of lamp body, also is better for it to move side ways if bumped.