Head tube rings

[Larry James]

Hey Folks

Wanted to get your opinion on when you add head tube rings. On my last frame I add them after the frame was all tigged up. I'd like to do then first but was afraid the heat from tigging would melt the silver. The bottom of the down tube would approximately be 5-10 mm from the top of the head tube ring.

[Mark Bulgier]

Are the rings decorative?  ‘cuz you can probably just leave them off.  Ironically, brazing the rings weakens the steel (assuming regular Cr-Mo), so if you braze rings on, then you need them.  If you don’t then you don’t. 

 

Anyone here ever had a headtube on a TIG frame fail for lack of a ring?  Anyone?  Didn’t think so.  I expect the HT with rings is probably a little stronger, but if the HT without them is strong enough then putting them on is optional.  It’s OK with me if you just like them (or the customer expects to see them).  They weigh next to nothing and don’t hurt anything.

 

I only made a few with thin (~0.9 mm) HT and no rings, and most of those were track bikes, so it’s a small sample size, but no problems from it.  On road and even MTB I liked to use a ring on the bottom and none on the top, sort of splitting the difference.  I brass-brazed ‘em (‘cuz brass is my default unless there’s a reason for silver), and got the brass to wet on the TIG bead and a little onto the DT, sort of a micro-fillet there.  I had a theory it would improve the fatigue endurance compared to a bare TIG weld, but I have no test results to prove it.

 

Next question, why is the DT hitting so high up on the HT?  Unless you need the DT to be extra high (like for a suspension fork maybe?) then it’s a little more structurally efficient to have the DT hit the HT as low as possible.  I’ll admit, the difference is slight, and a bike where the DT hits too high is not going to ride any worse.  It’s just theoretically a tiny bit heavier and a tiny bit weaker.  But it looks inefficient to my eye, and so the look is my real reason for not doing it that way.

 

Mark Bulgier

Seattle

[Daniel J Niedziocha]

I have not seen a frame fail due to lack of head tube ring, but I have seem a headset fail due to lack of ring.  The headtube was extremely thin walled and the bike was a rigid singlespeed that received frequent poundings through the woods.  The headtube eventually hammered through the bottom cup.  Check the link to see for yourself!

https://flic.kr/p/e8Ez7p

Dan

[Mark Bulgier]

OK I'll admit, that qualifies as a reason to use a ring -- on the bottom anyway.  Not going to happen on the upper headset bearing, right?

Mark Bulgier
Seattle

[Jon Norstog]

I used rings over a 1.6mm Columbus HT for years on BMX bikes and the like.  More recently I've been using machined headtubes I get from Doug Schneider.  I will sometimes use a ring on the bottom of a road bike, for instance when the HT is 1.25" x .035" and I'm not joining the frame up with lugs. 

To each his own.

jn

"Thursday"

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[Andrew R Stewart]

I’ve seen more then a few BMX/freestyle/street/jump bikes have their lower head tube ovalize from the stresses they saw. Most all were TIGed and had no rings. Andy.

 

Andrew R Stewart
Rochester, NY USA

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[tomm]

A structural reaction, a view that short ht's abet this along with using ball-bearings for the lower set of bearing vs sleeve bearings.

The principle is that the balls are cupped arcs of transfer at the ball surface-contact of stress slammed sideways vs a cylinder, the modern plastic has a very low friction under load at low rpm.

I'm so out there have plans for a hotend to use of a good bearing material in 3d-printer, lathe or mill to print bearings in place, santa??.

cheers, tom

[Jon Norstog]

"

I’ve seen more then a few BMX/freestyle/street/jump bikes have their lower head tube ovalize from the stresses they saw. Most all were TIGed and had no rings. Andy.

 

Andrew R Stewart
Rochester, NY USA"

I've done thaT myself to see if it could be done. It can.  So I have consistently reinforced that area of the frame. Have never had a BMX or any other bike come back to me for a ratted out headtube.

jn

"Thursday"

[Larry James]

Mark, I'm going to be using True Temper 44mm headtube with rings from Solid bikes. I don't think I need the rings with that tube, but to be honest I like how they look to I will be adding them. I was hoping to add them first, but it sounds like they need to go on after I'm done welding the head tube. And like it was said they weigh next to nothing and add a little bit of insurance.

Larry

[Andrew R Stewart]

Tomm- I never felt that headset friction was that big a deal as long as it still turned with CONSISTENT friction and the friction wasn’t too great. But what I highly dislike is slop in my steering (like a lose bearing). As I suggested any stiction would be bad for steering ease. A difference between constantly rotating bearings like hubs and the headset is that the headset isn’t turning in the same direction always. It starts and stops as it swings back and forth. Are your mentioned sleeve bearings free of stiction? How about free of slop? I have experienced nylon sleeve bearings before, all be it poorly made ones, and noticed both slop and stickness at the same time. In the end forces are not any differently loaded into the bearing elements. Are your sleeve bearings able to spread these forces over enough frame material surface to lower the peaks enough to eliminate distortions? Andy.  

 

Andrew R Stewart
Rochester, NY USA

 

From: tomm

Sent: Wednesday, December 23, 2015 8:45 PM

To: Framebuilders

Subject: Re: [Frame] Head tube rings

 

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[tomm]

Not having built one the caveat up front.

I've dealt with IGUS sales people over time only two knowing Campy, they felt after a brief 'break-in' stiction would be in the ballpark of Campy by using balls on the upper, not equal, yet not worse & "should be better" than most sealed-bearings, so, they should not prevent no-hands riding the question being answered.

Having grown up with non-sealed headsets, they ping to become "indexed steering" from a dent in the lower races, this a lack of "rpm". The lower headset bearings are to reduce deformation at high stress, stiction improves using thrust bearings, they carry vertical load so have a lip and are self-lubricated, stiction is less than ceramics why the company switched.

Anyway, it solves the slop problem, once installed they are lifetime, they won't wear out afaik for most riders, the upper bearings should be normal ball-bearings they don't get the high stress impacts so haven't researched replacing them, don't think sleeves are better there & may affect no-hands riding.

When adjusting old style headsets, when out-of-round they became critical as you mention, thus suggest measuring that with calipers to check that as the cause.
-tom

[Ken Cline]

tomm -

Fabricating a bearing yourself only makes sense if your goal is complete self-sufficiency (and even then you'll need the materials). Otherwise look at off the shelf composite ("sleeve") bearings. Different shell materials are available and the nomenclature seems to vary, but the inside layer is teflon (or similar polymer, sometimes with lead), which coats the metal shaft during break-in, producing a self-lubricating low friction interface.

If the manufacturers are to be believed, stiction is not a problem (e.g. SKF promises "virtually no stick-slip").

> Anyway, it solves the slop problem, once installed they are lifetime, they won't wear out afaik for most riders

Alas, TANSTAAFL. In my experience, these bearings pack out and start to rattle. Not a problem in heavy duty platform pedals. Slightly irritating in the suspension arms of my old Titus. But in a headset? No thanks!

[Andrew R Stewart]

Tomm- please feel free to bring to market a better headset and all. After over a hundred years and thousands or smart people before us you’d think things were pretty sorted out by now. please prove this wrong. Andy

[tomm]

Sure thing Andy, if you can explain the 1-1/2" steerers on road bikes any other way than lack of stress surface area in bearings due to 4" ht's let us know, they can't be more aero than 1".

My napkin says I can use a 1" steerer by switching to a thrust sleeve bearing on the lower for the same ht height, plug it into your software see what you get, I mainly use Comsol when I want a study this doesn't need one too blatantly different.

-tom

[Ewen Gellie]

Larry,

 I've been told of the Columbus 1.1mm head tube flaring on some road bikes under hard use, by Darrell of Llewellyn Bikes here in Australia. So a lower reinforcement HT ring will lessen the chance of that. I TIG my frames then solder on the ring afterward. I've made frames without for myself, and with for customers. Never had a HT flare. I use 1.6mm wall HT for off-road use. Larry,

[Ewen Gellie]

Hi Mark, that's pretty daring advice. None of the full-time framebuilders I talk with see things so black and white. The rings will reinforce the headtube. Yes, head tubes flare. You just need to find and ask the right people who pay attention to these things. The framebuilder needs to make a decision based on rider weight, usage, track record of breaking stuff. Stupidly rigid carbon-fibre forks will hammer a frame far more than most steel forks more commonly used in the past. So that's a thing now too. 

How much is this reduction in strength of the head tube from brazing that you mention..?  (and does that apply on main frame tube joints too?  :)    )  I can put a number on it, since the Bontrager article gives Brinell hardness test numbers as affected by the heat of TIG and brazing. I read it as creating a 5-10% reduction in strength during extended brass fillet-brazing. So that's pretty small. Which makes sense considering all the other brazed joints on a frame. Heavy riders, and rigid, stiff carbon-fibre forks will make a reinforcement ring more necessary. What a shame to have a frame's HT flare, disappoint a customer, come back for repair, repaint, etc. etc. for the sake of a HT ring. 

Cheers,

Ewen

Mark Bulgier wrote:

Are the rings decorative?  ‘cuz you can probably just leave them off.  Ironically, brazing the rings weakens the steel (assuming regular Cr-Mo), so if you braze rings on, then you need them.  If you don’t then you don’t. 

 

Anyone here ever had a headtube on a TIG frame fail for lack of a ring?  Anyone?  Didn’t think so.  I expect the HT with rings is probably a little stronger, but if the HT without them is strong enough then putting them on is optional.  It’s OK with me if you just like them (or the customer expects to see them).  They weigh next to nothing and don’t hurt anything.

 

 

Larry James wrote:

[Mark Bulgier]

Yeah I didn't  say that right -- it's not black and white.  I would always take "rider weight, usage, track record of breaking stuff" into account, sho nuf.  As I said further down (if you read that far), I mostly left the rings off for track bikes.  I would never leave them off for off-road or for heavy riders or guys who like 'air', dropoffs & such.

The only head tubes I saw that wallowed out at the bottom had rings!  Of course almost all bikes do have rings (unless they have thick head tube), so that's not very good evidence...  But mainly this one batch of Bridgestones that had copper-brazed head lugs (yes commercially-pure copper, not alloyed with anything).  They were furnace-brazed with a super slow cooling cycle, as annealed as steel can be.  Other than those I have to say it is pretty rare on quality road bikes, and rarer if they're TIG – compared to fillet brazed.  Big fillets soften the steel more than TIG does.

"You just need to find and ask the right people who pay attention to these things."  Hey, I wasn't exactly sleep-walking during my 20 years as a full-time pro framebuilder. My eyes were open.  I actively sought out and studied failed frames whenever I could.  That's one advantage of doing frame repairs -- you get to see other people's screw-ups.

But there was a builder around here who used tapered steerers (on tandems) way back in the last millennium, when pretty much no one did, he made them himself.  To use a big headset for 1-1/4" steerer at the bottom with 1" at the top, he pushed a mandrel into the bottom of the HT, expanding it. (His shop was next-door to a tube forming company.)  He started with thin HT (.035" 4130 I think), and I wouldn't be surprised if it got even thinner from being expanded, never measured it myself though.  No rings, and no problems (that I know of*) -- and remember, this was on tandems.
*But if they were failing, I would have heard the gossip for sure.  I know of at least a few of those still being ridden hard.

-Mark

[Cliff McLeroy]

I'm chiming in late here but I would definitely silver the rings on after the tig. If the tigging ovals the HT a bit you can give it a squeeze back to roundness before doing the rings. If it were me I'd make the ring go all the way to the tig fillet. You can get also miter it a bit to fit in the crotch, and then taper it down to the front. To me it's worth the extra strength and adds a bit of thoroughness to the appearance of the bike.

-Cliff