The quill posts were a short-lived "aero" invention from the 80's, I think. A nifty idea, but probably not the most practical.

Ok, for the Suntour Quill that I have, see the marked up image. There is a nut at the bottom, and a cam lock at the top. That cam lock must be accessible for it to work, and thus limits how far the post can be inserted.

Seatpost_Marked.jpg

As fietsbob mentions, some quills may have a bolt straight through, or you could make one, although installation could be a pain unless you had a seat with a center hole, and a seatpost that also was also open on top. Vintage Campy Post?

Looking at your seat cluster:

Seatpost Mod.jpg

If you cut just above the top of the locking mechanism (A), you'll gain a little bit, and that would be easiest if it is enough. No harm just cutting at (A) now before you do anything else. Perhaps some touch-up paint?

If you cut just above the top tube (B), you gain the most, but you loose the lock. And, thus the "quill" post. However, you should be able to move the lock below either the chainstays or the top tube (blue circles). My guess is that hitting somewhere in the middle of the seatpost would be just fine.

I have never seen a seatpost locked like that, but I can only guess what I would put inside of the tube. A nifty idea. It should make it easy enough to move, although I'd probably make a spacer, then ream or hone the locks inside the seat tube to the proper radii for the final tube mounting position.

If you slam the seat to near the lowest possible point, you may choose to also lower the top tube as you've thought about to aid with getting on to the bike, getting off, and stopping. But, it all depends on what the "captain" and passenger are comfortable with.

I don't know about knees and seat adjustment. I have always adjusted the seat on a road bike so that if I put my heel on the pedal then the leg should be 100% extended, or nearly so at about the 7:00 position forward. And then I get pretty full motion of the knees with a forward posture. I currently have the boom a little long on my trike, and it still seems rideable. I do use cleats for foot/shoe placement on the pedals. I assume I could ride a seat a little high. Actually, the seat on my funny bike is, or was a little high, and I have been angling the seat nose down a little to compensate, but that is also a pretty unique bike. Anyway, it sounds like you're pretty close on the seat height.

Nonetheless, the bike needs to be comfortable to ride.

OK, Stage one will be to just move the clamp to the underside of the top tube. I want to keep it as high as possible so that it will be easier to clean up the weld inside the seat tube. It will also then be possible to move the top tube down below it in stage two if needed. I had first thought of making a pattern of the hole required in the seat tube and cutting the hole. I would then remove all remnants of the original part of the seat tube from the clamp tube and weld it onto the new location. However, it may be better to not cut the hole in the seat tube, do the weld, and then use a round file, die grinder, etc. to cut out what ever part of the seat tube that protrudes into the clamp tube? In either case I would insert the aluminum seat post in just barely past the weld area to act as a heat sink and backing bar.

I was going to say braze in a sloping top tube then the seat stays can be cut and bent down .
or add a stub , back to where they are, just far enough above the wheel.

Thanks for the photos of the seat binder. Almost exactly as I had imagined (and drawn above).

How is the new seat height?

Since you're considering more work on the top tube, I'd move the seat binder under the seat stays. That is a good solid place for it anyway.

It looks like that was brazed together, so you should be able to pop it apart pretty easily with a torch, and without damage. Then you can braze it back in place, and the adjustment should be good.

I like your idea of finishing the cut with a file, or even drilling it out, but I'd probably do the initial cut through the tube before brazing the bracket on, at least to get it roughly down to size.

Why did you drill a hole in the side of the seat tube? Are you thinking of mounting the bracket on the side, rather than in front or behind the post? That would be an odd solution, although it should work as long as the legs don't rub on it. The old QR stuck out a little anyway.

If you braze, you won't have to worry as much about heat distortion and penetration through, and it should be easier to work in tight spots. Oh, also, brass can contaminate your tig welds.

If you leave the seatpost in, I'd find a junk post at a local bike recycler/co-op.

The owner actually cut the seat tube off before bringing it to me to see if lowering the seat would be sufficient. She also drilled the holes with the intent of pinning the post at the correct height, but stopped short of drilling the post.


Since I have no torches or brazing experience, tig welding is my only option. That is one reason for putting it on the front of the seat tube. If I were to put it on the rear, I would have to lower it a fair amount to give myself room to work. That would not be a problem in itself, as the seat post is 12-3/4" long, but the farther down the tube I go the harder it is to clean up the weld. Once I get the clamp tube removed and cleaned up I will decide which location works for me. I don't think putting it on the front side would create an obstruction.


I'd like to thank You all for the sound advice you have given me so far.

A number of years ago I received a "mention" and wondered what it was. I asked one of the moderators and got a "I don't know" answer. So I didn't worry about it.


Now that it seems that I've gotten more mentions without knowing it I'll just continue living like before. Sometimes a bit of ignorance is OK. Andy.

Well this is some of the finer welding I've done! And by that I don't mean best, I mean I had 2.5x cheaters in my helmet and wore 3x reading glasses. I did have the seat post in just past the weld area, and after every 3/8" of weld I would spin the seat post to cool the weld and make sure it wasn't seized in place. I did only drill a 3/8" hole in the seat tube before the welding. After the weld, I opened up the lock tube with a die grinder and smoothed the inside of the seat tube with a tiny drum sander on a die grinder. A little de-burring with a chainsaw file and that's as good as it gets.

It looks nice. I assume the fully assembled photo is holding the post.

I'd probably plug weld the hole, but then you'll have some reaming to do, hopefully not too bad. I've never welded with aluminum behind my welding, but perhaps that would help, although filling a hole is different than simple welding.

Once you get done massacring the fame, you should send some photos to Bilenky.

You will need a pretty long seatpost if somebody ever chooses to raise it, but I suppose they can deal with that later.

I was going to plug the holes for them ( I punched a couple of 3/16" diameter blanks out of the seat post offcut) which I was going to fuse in place, but ran out of time because the owners wanted to come and pick it up. Copper is a better weld backer, but aluminum works pretty well. The seat post is plenty long at 12-3/4". In the pic it is inserted to just below the lock mechanism. I believe this is all the massacring that may be necessary (hopefully!).


For some reason this site will not let me post some pics? Anyways, it looks like they could have almost 8" of seat tube sticking out if they wanted.

Thanks a million for all your advice and thank you Greg for doing all the research, development, and then the actual modification...Just got back from taking the bike out for a 2 1/2 hour ride and it is like a new bike - the bike seat can get low enough now that there's no knee strain, the seat is solidly locked into position, can be adjusted as needed - the Stoker, absolutely loves it, loves the feeling of being able to move freely and to chat within hearing range while we are cycling - gear changing, brakes, and steering had become too much on the recumbent trike, now by working together on the tandem we are back cycling as a team. Thank you so much Greg for taking on the modifications and for everyone in this forum for your advice. Happy Cycling!!