Help/advice on titanium frame modifications.

[bicycletricycle]

I just got a really cool titanium spectrum. Like many modern frames it has no provisions for down tube shifters. Perhaps this is silly but I am considering getting down tube bosses welded on, if I did this I would also be interested in having the water bottle riv nuts replaced with welded in jobbers.

I am in Rhode Island so a variety of Boston based builders come to mind, the frame was made at Seven but I have no idea if they would be interested.

Any advice/experience with this sort of thing would be appreciated .

[Kontact]

Seven may agree to do the bosses, but they don't do welded bottle bosses because they think it increases the likelihood of frame failure.

A problem either way is if the tubes are butted, and whether then are thick enough to weld to. When Merlin was making bikes with DT bosses, they were the ones butting the tubes, so the butts may have extended past DT boss location.

Another issue is whether the inside of a used bike's downtube can be cleaned sufficiently to insure no contamination. The primary downside to ti frames is weld pollution leading to cracking - I don't think I've ever seen a ti frame failure that isn't on or near a weld.

There are so many old Ti frames out there with DT bosses for cheap if you don't have a hangup about 1" steerer tubes.

[m_sasso]

I think I would be more inclined to use a clamp, I like DT shifters, most of my 9 bikes use them however unless it is a lifetime frame I wouldn't make non engineered modifications to the middle of a Ti tube.

If I was paying to send the frame back to the original builder, likely would be a different story.

[eddief]

and within budget:

http://urbanvelo.org/problem-solvers-downtube-shifter-mount/

https://problemsolversbike.com/products/shifters-derailleurs/downtube_shifter_mount_-_31244

[longlist]

why not use these. i have them on my gt edge titanium frame.
http://www.cycle-frames.com/bicycle-frame-tubing/NOVA-LEVER-BOSS-KIT-FOR-AL-FRAME.html

[David Kirk]

I doubt you'll find anyone excited about welding bosses to the DT. They so often lead to DT failure.

dave

[cadence90]

bicycletricycle, you're a designer and also an excellent machinist.

What about fabricating a milled alu downtube double cable stop, as Scapin do, but modified to incorporate standard downtube shifter bosses, and then riv-nutting or screwing the piece to the down tube rather than risk post-fab welding the bosses themselves?

https://bikerumor-wpengine.netdna-ssl.com/wp-content/uploads/2013/01/Scapin-Style-cable-stop.jpg

Something that would in effect combine into a single piece the Scapin base and the alu bosses that longlist posted above.

Just an idea; it could be a fun project.
If you could make one, it would certainly be more elegant than those clamp-on ones.


I doubt you'll find anyone excited about welding bosses to the DT. They so often lead to DT failure.

dave
Dave, would that idea (screwing/riv-nutting a machined "bridge") work?
.

[Kontact]

While I would be loath to do it to a Spectrum frame, you could also just install one of these after modifying it to suit the tube diameter:

http://www.cycle-frames.com/bicycle-frame-tubing/NOVA-LEVER-BOSS-KIT-FOR-AL-FRAME.html

http://www.cycle-frames.com/bicycle-frame-tubing/images/P/201628.jpg


(Sorry, didn't see longlist's prior post.)

[zennmotion]

Bar end shifters>DT shifters. IMO. Back in the day they weren't as popular because of the extra cable and housing length made them feel a little more vague than DT shifters. But with modern compressionless housing and slick cables I've found them to be quite precise and crisp even as I have them set up for the cables to extend and exit the bar tape at the center of the handlebar. I have a set of Rivendell "Silver Brand" bar ends that I really like, with a good ratchet/friction mechanism that feels better to me than Dura Ace indexed bar ends, significantly less force on the lever to shift than Shimano clicks, and you can use them with any cassette (though 11 speed probably would be too figety) I wouldn't try to weld anything on a Ti frame, it would be stupid expensive. Bar ends are cool and still relevant, I have a tandem, a travel bike, and an all road/gravel beast with bar end shifters- simple, light, fast shifting, reliable, easy to repair/replace.

[eddief]

always wanted to try them on the road:

https://www.gevenalle.com/product/cx2/

I assume your frame is missing cable guide too?

[m_sasso]

Not particularly fond of the Problem Solvers clamp appearance or drilling holes in the frame to use the Nova lever boss set.

There are all kinds of classic clamps available on Ebay for next to nothing along with some current renditions of classic clamps.

Just a few!

https://www.ebay.com/itm/70s-vintage-Huret-downtube-shifter-clamp-mount/173329119890?hash=item285b387a92:g:RKgAAOSw7I5bAxf 1

https://www.ebay.com/itm/Huret-28-6-Shifter-Downtube-Frame-Clamp-Vintage-NOS/123027046095?epid=508610550&hash=item1ca4fbbecf:g:GhkAAOSwMqVarVpJ:sc:USPSFirs tClass!98230!US!-1

https://www.ebay.com/itm/Shimano-28-6-Downtube-Shifter-Clamp-Crown-Style-Vintage-NOS/122422520796?hash=item1c80f36bdc:g:4g0AAOSw2xRYZDP x:sc:USPSFirstClass!98230!US!-1

https://i.ebayimg.com/images/g/9QIAAOxyMxpRsiDt/s-l400.jpg

https://i.ebayimg.com/images/g/ePUAAOSwyHRavVVC/s-l1600.jpg

[bicycletricycle]

Those adapters are all ugly and not big enough for the downtube anyways. I had thought about making something aesthetically acceptable but those barrel adjuster tabs in the headtube would still make me crazy (I have become a monster)

I think I’ll end up with bar end shifters on it but I just really like using friction down tube shifters, oh well. I guess I can rejoin this century and use flipper shifters.

Lots of ti frames have stuff welded onto them mid tube, cable guides etc. do down tube shifter mounts present a unique stress riser because of their location? I remember loads of titanium lemonds breaking at that location. I forgot about the cleanliness issue on the inside of the tubes but the bike has couplers so the inside of the seat tube and down tube are accessible.

Also, almost all every fabricated structures fail at the joints. It is not unique to titanium or titanium welds although the extra sensitivity to contamination in the heat effected zone is different to other more common bicycle materials.

Hmmmm.

Perhaps I could glue some on? I wonder if that would be strong enough?

[m_sasso]

There are clamps available in 57mm, how big is your downtube?

And likely this guy can make you what ever diameter you want https://www.ebay.com/itm/MOOSE-RACING-Made-to-Order-37-57mm-Diameter-Clamp-On-Downtube-Shifters-Adapter/132602185245?hash=item1edfb4c61d:g:64EAAOSwBnZavBq S

[David Kirk]

Down tubes are put through a lot of twisting at the upper end and the welded on boss, with it's sharp corners and lots of welding make a stiff spot that the tube fails adjacent to.

Old school steel bikes had DT butts that were long and meant to deal with the stress in that area....and they were silver brazed on so the head was MUCH lower.

Serotta had a very large number of DT failures on early Ti bikes with shifter bosses. It's what pushed me to design their head tube system. Once we switched the failures stopped completely.

dave

[Kontact]

Those adapters are all ugly and not big enough for the downtube anyways. I had thought about making something aesthetically acceptable but those barrel adjuster tabs in the headtube would still make me crazy (I have become a monster)

I think I’ll end up with bar end shifters on it but I just really like using friction down tube shifters, oh well. I guess I can rejoin this century and use flipper shifters.

Lots of ti frames have stuff welded onto them mid tube, cable guides etc. do down tube shifter mounts present a unique stress riser because of their location? I remember loads of titanium lemonds breaking at that location. I forgot about the cleanliness issue on the inside of the tubes but the bike has couplers so the inside of the seat tube and down tube are accessible.

Also, almost all every fabricated structures fail at the joints. It is not unique to titanium or titanium welds although the extra sensitivity to contamination in the heat effected zone is different to other more common bicycle materials.

Hmmmm.

Perhaps I could glue some on? I wonder if that would be strong enough?

Ti fails in a very particular way starting at a single point at the joints, rather than just developing general cracking like a steel joint would.

You'd also have to sniff out the wall thickness issue - most tubing is .9, but the center of butted tubing can be .6mm.

The coupler access would help.

Epoxy doesn't love titanium, so I don't think there is enough surface area to bond a boss without a cross hole.

[colker]

Ti fails in a very particular way starting at a single point at the joints, rather than just developing general cracking like a steel joint would.

You'd also have to sniff out the wall thickness issue - most tubing is .9, but the center of butted tubing can be .6mm.

The coupler access would help.

Epoxy doesn't love titanium, so I don't think there is enough surface area to bond a boss without a cross hole.

A carbon collar wrapping the down tube could a solution. Then you would have some nice surface extension for glue and support. It could work but it sounds like a lot of work.

[Kontact]

Ideal solution: Vacuum brazing.

[bicycletricycle]

For those of you who are suspicious of titanium weld-ons in general but especially in the headtube area. Do you think the current crop of titanium bicycles with di2 ports and internal disc brake routing that use weld on reinforcements in this area are all destined to fail?

It seems to me that custom titanium manufacturers are welding more bits on the frames then they ever have before, disc mounts, internal hydraulic routing, external hydraulic routing, internal electronic cables, etc. Is this bad?

[bicycletricycle]

Ti fails in a very particular way starting at a single point at the joints, rather than just developing general cracking like a steel joint would.

You'd also have to sniff out the wall thickness issue - most tubing is .9, but the center of butted tubing can be .6mm.

The coupler access would help.

Epoxy doesn't love titanium, so I don't think there is enough surface area to bond a boss without a cross hole.


The failure mode of titanium should not be a problem. We have figured out how to weld whole bikes together out of it with all kinds of extra bits welded on for brakes and pumps and water bottles and cables. I get that the down tube on this particular frame could be too thin for this application as it was not designed to have something welded on in this particular location.

Also, the water bottle mount thing seems like a funny one, some builders do it and some don’t. Those rivenuts are great till they start to oxidize or come loose and then they can be a real pain, on the other hand, a welded in boss could lead to crack down the road. I wonder if it Is only if it contaminated or if the added stress from the change in thickness is the problem. I guess it could be both.

[VoyTirando]

Having just built a used spectrum this week, and running it through various tweaks after each ride, I for one would love to see what you've got your mitts on.

I, too, have gone though a calculus as to whether to have this frame modified: couplers, moving the break bridge for bigger tires... and thanks to the sage advice here, have accepted just letting my frame be. It's what it is. It's turned out to be a wonderful bicycle. No, it won't come to Spain, nor will it scale D2R2, but it'll do lots of other fun stuff.

Love to read all this tech info on ti fabrication. So much experience on this board.

[eddief]

are there not a ton o ti bikes you might choose that have all the parts currently attached?

[Kontact]

The failure mode of titanium should not be a problem. We have figured out how to weld whole bikes together out of it with all kinds of extra bits welded on for brakes and pumps and water bottles and cables. I get that the down tube on this particular frame could be too thin for this application as it was not designed to have something welded on in this particular location.

Also, the water bottle mount thing seems like a funny one, some builders do it and some don’t. Those rivenuts are great till they start to oxidize or come loose and then they can be a real pain, on the other hand, a welded in boss could lead to crack down the road. I wonder if it Is only if it contaminated or if the added stress from the change in thickness is the problem. I guess it could be both.

It isn't a problem - I just didn't assume you have coupled frame so the inside of the DT could be cleaned. But what I was getting at is that ti fails in a very particular way, and generally only in that way: It gets a stress riser from a spot in the weld that is contaminated and progresses from there, often in two directions. In this photo you can even see the pit that is the likely origin:

https://www.sheldonbrown.com/rinard/EFBe/tour14db.jpg

Otherwise, titanium is so flexible that it unlikely to work harden, and welding temperatures change the structure less than what happens to steel, so the HAZ is generally less damaged. So if you have a Ti frame with perfectly uncontaminated welds, the bike has a good chance of lasting indefinitely.

Bad rivnuts can be re-tightened or removed and replaced in a few minutes. I know they seem cheap, but they avoid the perils of welding and cross threading on a part you'll never see. If they corrode, the corrosion doesn't affect the Ti. They really are a more elegant solution than it may appear.

Spectrums were made by Merlin, then ABG and now Seven, but ABG is still supplying the tubesets to Seven. Merlin (and probably ABG) always externally butted the tubing via lathe turning the center section (because Tom and Merlin don't like cold working Ti), so if you may be able to measure whether the DT is butted with a caliper, and how far down from the head tube it extends. Of course, Spectrum also made plenty of straight gauge frames.


I totally get where you're coming from - I entertain the idea of sending my Calfee in for DT bosses sometimes. The companies that like to weld bottle bosses are probably not going to want to become liable for a possible future failure of your high end Ti bike, so I really think your best bet is to leave those alone and just contact Tom Kellogg about the DT boss retrofit. He should have your specific frame's data on file to tell you if there is a problem with adding the bosses and then have you send it to whoever he deems appropriate. He's an easy guy to talk to and will likely want to help you out for no more money than going to a local Ti frame guy.

Of course, someone has to come up with some Ti shifter bosses, and I couldn't find any just now. But Seven or ABG may still have some sitting around.

[bicycletricycle]

are there not a ton o ti bikes you might choose that have all the parts currently attached?

Well, I have very fussy requirements these days, no off the shelf Ti frame gets close to what I would find ideal and a custom ti frame built to my liking would be very expensive and a long wait. This spectrum is close to what I would get as a custom and so I am considering the possibility of tuning it a little bit to iron out some of its shortcomings. Not actual shortcomings just stuff I prefer.

I have to put some miles on it first to see how much I like it before I would consider getting anything done to it. In the mean time I am consulting with my friends here about implications of these kind of modifications.

So far I have learned that down tube shifter mounts are always a bad idea on titanium frames, something I don’t really want to believe and also find disappointing. If I ever do get a custom Ti frame built Downtube mounts are a must.

[Kontact]

So far I have learned that down tube shifter mounts are always a bad idea on titanium frames, something I don’t really want to believe and also find disappointing. If I ever do get a custom Ti frame built Downtube mounts are a must.

Geez, I hope not. I have them on 3 bikes.

[bicycletricycle]

Geez, I hope not. I have them on 3 bikes.

Well, hopefully they hold up better than the old serottas with DT mounts on them.

[Kontact]

Well, hopefully they hold up better than the old serottas with DT mounts on them.

Now I want to measure the butting on my Extralight's downtube.

I just took off the shifter on my Basso - they only welded the boss on the top and bottom edges instead of all the way around. That's probably a good thing, too.

[happycampyer]

I think the problem Dave was referring to was the result of having downtube bosses on frames with butting, and Legends had pretty extreme butting. I don't think bosses are an issue with straight gauge tubing. Depending on the model, the Spectrum may or may not be butted.

Regarding the water bottle bosses, I was having a Legend repaired, and wanted to have the rivnuts replaced with welded bosses (more recent Legends had welded water bottle bosses). I recall Scott Hock telling me that the holes in the frame to accept the rivnuts were too large replace with a welded boss. Not sure if that's the case with Seven/Spectrum.

[Clean39T]

Pics of said Spectrum?

Does it have purple flames?

[bicycletricycle]

Pics of said Spectrum?

Does it have purple flames?


no pics until it is built, no purple flames.

[Clean39T]

no pics until it is built, no purple flames.


Then it isn’t the one I was thinking of...

[Butch]

This is to the broader question of Di2 holes, internal routing and other weld-ons, stops wattle bottle bosses etc on titanium frames. At Moots when a change was made, ie a hole for Di2, the CEN test that we had done is as follows and is modified by the fork length for various models - road, cross, mtb.

Test Conducted
Fatigue Test With Horizontal Loads (Head Tube Test)
Test Description
Apply cyclic loading of +269.8 lb.max/-135 lb. min horizontally to front axial with pinned rear axial
Test Specification
CEN 14766 paragraph 4.8.5
Requirements
+269.8 lbf.max/-135 lbf. min (0/+ 5%)
Frequency <20 Hz
No. of Cycles: 50,000
No visible cracks or fractures and no separation of any part of any suspension system. For carbon fiber frames peak deflection in either direction from mean position shall not increase by more than 20% from initial values.

This test was effective for modifications during my decades there with avoiding failures on road and cross frames with any of the tube choices and options offered.
I will add that totally different ISO testing done on disc forks is one of the more rigorous tests done and the main reason a disc road fork weighs 30% more than a rim brake fork.

[bismo37]

You guys are freaking me out. I bought a used ti frame that I later had fender mounts brazed on the rear triangle as well as a disc brake brace on the rear stays. Am I going to die?

[FlashUNC]

My gut is that Tom and Srvrn built it to the specs to do what it's currently doing. If there were going to be DT bosses welded on or non-rivnut bottle bosses, then a number of other things might have changed in initial construction.

Not an area you want failing spectacularly on a frame and if you called to ask Tom his thoughts, I'd be surprised if he said it was worth pursuing. Enjoy it as it is.

[Kontact]

I hope the OP actually calls Tom with his serial number and gets the straight dope.