Monday, August 29, 2005

An Idea

Sometimes I take a perverse approach to problem solving - this may be one of them.

For simplicity I'm using threadless steerers and headset. No steerer to thread, less fuss about steerer length - it all sounds good. But, then you have to use a stem which clamps around the steerer and provides the backing against which the headset is adjusted.

Well, I generally think that a traditional quill stem is more attractive and provides me with a better fit by letting the handlebars sit up higher. Yes, I would put a ton of spacers on the steerer and then flip the (aheadset style) stem at an upward angle - but that seems unattractive to me.

My first thought was just to create a clamp around the steerer against which to adjust the headset. That could work, and would allow me to put a quill stem inside the steerer. I may still do this.

But I've been thinking, and may have a better (but not perfect) answer. It seems to me that I should be able to get a piece of 28.6mm outside diameter tubing that has a reasonably close fit telescoping over the steerer. In fact, I've purchased a piece of straight gauge CroMo which should do fine.

This tubing should fit easily into seat lug, where it can be brazed into place to form the quill. Another piece of 28.6mm tubing can be brazed to the front of the seatlug forming the extension. At the bottom of the quill, a clamp can be brazed on. Then we cut a slot on either end of the quill (with a round hole at its end), and our stem can fit over the steerer while clamping on at the top and bottom.

The effective length of this stem is limited by the length of the steerer. That is, if the quill is longer than the steerer, then its clamp won't grab the steerer. This is apt to allow a little bit of play back and forth as one rides. So, we're going for effective clamps at each end of the quill. Hopefully there will be enough steerer for this to work.

At the point, we need to miter the end of the extension and braze on a short tube that will be the handlebar clamp. Slit this tube after brazing on the actual clamp and we almost have a stem.

The points on the lug (that I'm going to use), which are in front and back of a seatpost, are now in our way. At least I don't want to keep them there where they'll pierce any flesh that falls on top of them. Also, the top of the quill is open. So, now we file off the the points, leaving the opening with a smooth convex curve (from side to side) above the quill. If this piece doesn't look too goofy, we should have a nice (possibly new style) of stem to try on our bike. Soo..... I better get this finished too before I take everything over to the painters.

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