Seat tube sleeve question

[Shawn Pedersen]

I have a few questions about sleeving a seat tube. I have made a few odd choices with this frame and hoping to get some feedback on the best next steps. I've gotten some great local help here from a buddy but we want to see what you guys think. I searched this site and some others and didn't really find anything that addresses my question.

I have one of the Nova dropper seat tubes for a 31.6 dropper. It has an OD of 33.5, and wall thickness of .9mm. I took a 36mm headtube and turned it down on my lathe to a final OD of 34.9 so I could run a standard seat clamp. The sleeve now has a .021" wall thickness. We're thinking that is going to be a bit too thin to try to braze without a bunch of distortion since I'd like it to drop about 3" from the top of the st.

A couple of routes I'm considering going are just ditching the sleeve and brazing on a binder bolt and moving on or maybe just silver brazing on enough of a sleeve to sit under the clamp so it is covered (say 10-12mm like 18bikes did in this thread http://www.velocipedesalon.com/forum...sts-32854.html), but I was hoping to have the sleeve continue down far enough that I can also attach the seat stays to it since this Nova tube is so thin! Brazing the seat stays on over a sleeve that has been silver brazed presents another issue I assume.

The other question is this thin seat tube ended up with some raised material in the seat tube that needs to be reamed out where the top tube joins. I was surprised how much the metal pulled. I don't recall anything out of the ordinary about brazing the fillet (too much heat etc). Is it OK to ream the tube and assuming I don't cut through if it gets too thin? Are there guide lines on how much one should or shouldn't ream a tube. If you run your finger down and feel a high spot at the join, does it fail the finger test?

I'm also trying to work around items that I already have like a Thomson 31.6 dropper so shimming to 30.9 or whatever is not ideal.

Next go around I'll definitely not use the Nova tube. I'll be using a pre bent thicker wall 34.9 tube from Walt.

Thanks for your help, Shawn

sleeve 1.jpg sleeve 2.jpg

[Rody]

Shawn,

The issue is not the NOVA tube, but the process you have choose to employ.

To gain the benefit of a sleeve, it must extend from the top of the seat tube -> below the top tube, creating a thicker section that allows for support of the seat post internally, and the top tube and seat stays externally. Fabricating this "spine" of the frame first is the most efficient process, protecting against distortion and limiting post fabrication reaming.

As for resources, you need to mine the wealth that has been shared previously.

Steve epitomizes the sleeved style you are striving for, see how he does it here... coconino cycles custom bicycles 928 774 7747

As an alternative method, utilizing your lathe, you can create a seat tube insert topper that provides a different aesthetic as well, seen here... Groovy Cycleworks 330-988-0537: Creating the spine of the frame...

Both will yield the results you desire; a strong frame that will provide longevity, accuracy, and little post fabrication cleanup.

cheers,

rody

[Shawn Pedersen]

Thanks Rody! I appreciate your info. Your blog kicks ass....so does Steve's :) This thread here on VS really made it all sink in for me. http://www.velocipedesalon.com/forum...mer-35657.html

I may have to call in sick for the next few days to take a break and read your entire blog :)

As for this frame. I'm perfectly happy just putting in a few rides on it and starting over. SO much learned. You guys are an invaluable resource for new builders. Thanks again.

-Shawn/Seattle