Columbus Neuron tube - orientation

[Mark Walberg]

I crashed my old DeRosa from the mid-80s, built with SLX tubes. I hit a curb. Front triangle is toast. Top tube lug ripped right through at the tube junction! Amazingly, the fork is OK- minimal straightening required. Now that all my bones are mostly healed, I'm putting a new front triangle on. I brazed on the top tube yesterday. There are no pins in these DeRosas by the way.
I have a Columbus Neuron 28.6 mm tube that I am going to use to replace the down tube. There is almost nothing on the internet about these Neuron tubes. They have elliptical butting. I'm not sure, but I think they might also have asymmetric differential butting where where one side of the butt is longer than the other side of the same butt (like Nemo tubes).
The tube has a small tab on one end, located on the inside of the 0.9 mm part of the butt. The butt is 0.9 mm on the thicker part and 0.7 mm on the thinner part of the butt. Does anyone know rest of the anatomy of the butts in these Neuron tubes? Are the butts on both ends the same length? Are the butts asymmetric and, if so, how does the tab tell the orientation of the asymmetric butts? Which way should they go in?
Thanks, Mark Walberg

[Andrew R Stewart]

Mark- You need a butt gauge... Andy.

[Mark Walberg]

Thanks Andy. I found your posts about your gauge and the pictures in your photo stream. This is very helpful.
By the way, I have found you Frame #830 pictures immensely instructive. I really appreciate your efforts in posting all those pictures. The comments along with the pictures are really thoughtful and informative.
Thanks!

Mark Walberg

[Andrew R Stewart]

Mark- Sorry to be close to snarky in my reply. I wish I had the answers you're looking for. Thanks for the pat on my back. Andy.

[edoz]

Are you saying that the wall thickness is not consistent on the ends? I have no answers for you, but I'm curious because I didn't know anyone butted tubes that way.

[Mark Walberg]

Hi Eric, There are two asymmetries to the butt, I think.
First, the inside of the butted end is oval, not circular. This makes the wall 0.9 mm on the thck part and 0.7 mm on the thinner part, with 0.5 mm wall in the mid tube between the butts.
Then, the second asymmetry is that the butt is longer on one of the 0.9 mm walls than it is on the other, so you end up with a butt that is shaped kind of like this,======\ instead of this ======|, where the line shows where the end of the but is toward the middle of the tube. There is a better drawing of this at the web site Columbus Nemo 747 Steel Tubing Drawn Exclusively for Torelli!

I'd never seen a butt gauge before, but that would let me figure out where the butts are. Again, thanks Andrew. I truly didn't notice any snarkiness -- I just appreciate the good advice.
-Mark Walberg

[edoz]

Thanks for the explanation, and the link. That's definitely interesting, I learned something about tube history:)

[Scheisserad61]

Don't overthink all this - the longer sections of the .9 butts go on the BOTTOM of the downtube and the TOP of the toptube at the headtube end. Just like many long-point lugs have the points oriented. The .7 areas go on the sides of the joints. The idea was to have the thicker material resist the INLINE stresses from braking and potholes and cobbles, and bunny-hopping / whatever.

Just get the headtube butts oriented properly and don't worry about the other (lower stress) ends at the BB and Seattube. The engineers (and marketing people) at Columbus have already figured that out for you, and I kinda can't remember that end. I prolly have the old Columbus and Nova catalogs around buried under my collection of Juggs and Leg Show magazines, but I doubt that I have the time or energy to dig them out.

The Neuron and Genius and Nemo tubesets were among the last dying gasps of Steel tubing being innovated/marketed for the high-end market. The early - mid 90's were not a good time for any of the "traditional European" steel tube mills. It wasn't long before all the R&D went into Aluminum, Titanium, and then Carbon Fibre. When you combine that with the entire bike industry moving halfway around the globe, well - it is a wonder that we have as many choices in steel tubing as we currently do !

[Mark Walberg]

I can't see which side of the butt is the longer side, or even if there is a longer side.
Sighting down the tube, I can see the butt, but not well enough to tell if there is a long and short of it.
As Andy says, a butt gauge will tell me what I need to know. I need to build one.
If someone knows whether the little tab is on the long side or the short side, that would help, until I build the gauge.
Thanks, Mark

[Mark Kelly]

Get a small weak magnet and a bunch of business cards. Place the tube with the axis horizontal and stick a card to the bottom of the tube at the heavy wall section with the magnet. Now add another card beneath the first, then another and another until the magnet doesn't hold. Count how many cards this took.

Now move to a lighter wall section and do it again. The number of cards should be distinctly lower because the net permeability scales with thickness. With a bit (or a lot) of patience you could use this to find the butt ends on each side.

[afwalker]

blogger-image--2068529745.jpg
I thought it was a fun and easy project to make a checker.
Just 2 rods parallel. I used hex steel and drill rod, a 1" piece of square tube.
The stand kind of works, still have to hold the tube being measured.
Do like the other Andy says, make a checker:)
I bet the card trick works though.
cheers
andy walker

[bellman]

Handy little tools indeed but I think to get maximum inyouendo out of it, Dazza would refer to it as a 'butt toucher' :-)

[afwalker]

I was trying to avoid the subject, just called it a checker.
But you could use a feeler gauge!
cheers
andy walker

[afwalker]

It also may have to do with the orientation of the tube itself...
not imposing my values here, but maybe the tube doesnt feel like getting checked right at the moment.
cheers

[Andrew R Stewart]

Like Richard S says. You've got to show the tube who's the boss! Andy (who knows to treat his wife better then he does his tubes).

[Mark Walberg]

Mark- You need a butt gauge... Andy.

Thanks again, Andy, for the excellent advice.
I made a "Butt Feeler" and mapped the butts in my Neuron tube.
The gauge works well. It would work better if the bottom rod was a lot longer to hold the other end of the tube, but it works fine.

Anyway, I know where the butts are now.
I also found that the thick/thin differential wall thickness of the butt is not made just by an oval inside diameter.
The thick part of the butt wall is more like a tongue of thicker wall on each side.
I tried to take a picture of this to show it. Each tongue is only about 10% of the circumference of the tube.
So, it is kind of like a built in lug point. The location of the tongue is at about 7:30 on the picture here.

DSC_2029_332.JPGDSC_2030_333.JPGDSC_2034_336.JPG

I was surprised to find that the thick part of the butt is not the same at both ends of the tube, but is rotated 90 degrees.
In other words, if you place the thicker butt walls in a vertical orientation at the bottom bracket, then the thick parts of the butt at the head tube will be right and left.
Which way would you place these -- right left at the head or at the BB?

I found an old post on the net that was referring to the Genius tubes that also have a small alignment tab at one end:

If that alignment is right, then it would make the head tube butt right-left and the BB butt vertical.
What do you guys think?

thanks again.
Mark Walberg

-------post found on web below-------
Re: [Frame] Columbus Genius

On 7/6/2011 2:14 AM, David Benson wrote:
> Can someone refresh my memory regarding Columbus Genius?
> Am I correct in thinking that the alignment tabs
> <http://www.flickr.com/photos/bishopbikes/4164284223/> indicate the long

> side of the differential butt at the front end of the tube?
> Thanks
> DB
> True Adventures of the Retro Grupetto
>
according to the columbus spec sheet
top and downtube: tabs facing on the inside against the headtube
seattube : tab facing right in line with the derailleur tab
--
mvg
Marten Gerritsen
Kiel Windeweer
Netherlands