# Segmented fork sleeves?



## Meriwether (Jul 26, 2007)

Hey all, 
First real post here...I am a huge lurker. I feel like I have sinned or something.
SO...I've been at this for about a year and have made two frames and two unicrown forks on my own after a short one-on-one class last May. 
I found a couple threads with advice on how to weld/braze seat tube sleeves but wondered what people's process is for doing segmented fork sleeves?

The posts talking about seat tube sleeves said to do the silver brazing _after _ welding the TT to the sleeve. But doing it that way may result in less silver penetration throughout the sleeve, not a big deal it sounds like. But what about for forks with much greater stress on the brazed sleeves? Would you braze first and then weld the legs to the crown segments or vice versa...?

The attached pics show the one I already made...and it turned out just ok. I won't be riding it much. It was a total PITA, especially to get jigged up without brazing first, but I like how it turned out at least aesthetically.

The legs are 1" x 0.035" and the sleeves are 1.125" x 0.035". I used brass but I know it didn't penetrate very far down the sleeve (my test runs got the brass down maybe a half inch on each end). I am pretty sure silver would work much better. But is it a huge problem if there's not much brass going all the way down the sleeve? Will that small gap inbetween the sleeve and the leg cause any problems?
Also, when setting it up in the fixture, I couldn't get there to be an equal amount of space on all sides of the legs -- there were bigger gaps on the back of the sleeve than on the front since it was all being held down in the fixture by a toe strap. How to fix that?

I've started on my second one, but this time I have added 'windows' to the sleeves so that it'll be easier to pull down the silver while brazing and get better coverage hopefully (see last pic). But what do you think - braze or weld first?

thanks in advance...
Whit


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## Walt (Jan 23, 2004)

*This is a good question*

I am surprised that nobody has chimed in.

-I like to weld first, then braze the top/bottom (this goes for seat tube sleeves as well). I have never had a problem doing this, though I'm sure the silver/brass is only penetrating maybe an inch at the most. Some little windows would be good to allow a bit more like you've done. Obviously the filler is only going to penetrate only as far as the flux can go, which is not going to be all that far. Nevertheless, I don't think you need much to hold everything together (in most cases, the TIG on the sleeve has locked it all together anyway and the brazing is just to fill the shorelines).

-.035" is a very loose sleeve. I usually use .058" to get a relatively tight slip-fit.

-Walt


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## Smudgemo (Nov 30, 2005)

I can't offer much help on building this sort of fork, but as for the slop between the sleeves and legs, you'll find a proper slip-fit for silver by using a sleeve of 1.125 x .058". Any tube with a wall of .058" will slip-fit over a tube that's .125" OD smaller.

Aside from the gap with .035 probably being too large for silver, it'll cost you a fortune to fill with prices where they are now.

Oops, Walt beat me to it.


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## Meriwether (Jul 26, 2007)

That makes a lot of sense about using 0.058" instead of the 0.035" sleeves. It'll add some weight but the fit will be much easier to silver braze. But yeah, with the cost of that stuff right now maybe I'll just forget this method, or stick with brass and hope it holds up! 
I'm going to finish that 'windowed' sleeved fork since it's all cut up and ready to go. I may just try and brass braze first since I tried the opposite last time and trying to get it all to stay put and aligned in the fixture for tacking was pretty funny (read...frustrating :madman: ). 

Thanks for the words of wisdom!

Whit


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## dr.welby (Jan 6, 2004)

Just a little thought experiment here:

Consider a filleted tube joint - with a root fillet depth of 3X your joint is held together by a ring of brass about 3mm thick, and nothing else.

On your fork sleeve of similar diameter tubing, you could easily get 3mm of filler penetration up into the sleeve. And you have some mechanical constraints - the joint has to fail in torsion or in the axial direction. Bending probably loads the braze very little.

So really, you probably should be more than fine by flowing in a little brass/silver on each end of the tube. ( IAMNYFD, etc )


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## Meriwether (Jul 26, 2007)

*crimp*

Nice, I like that thought experiment. I tried a little experiment of my own last night. I took my Park fork/frame alignment tool and did some tweaking on one leg (with the fork in the vise) to see where the fork would fail. See picture. It failed (bent) about 1cm below the sleeve on the 1" diam leg. It sucks to kill something that just took so long to make but it's good to know the fillet was stronger than the tube, at least on this fork.


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## Meriwether (Jul 26, 2007)

*fork update...*

I finished the fork and it turned out ok! I followed Walt and Smudgemo's advice and used a thicker sleeve to tighten the fit but I didn't have any 0.058" tubes so instead used 0.049". SO...I first welded the dropouts to the legs in the fixture, and then cut some new sleeves and used Harris 50N silver to braze them on to the 1" legs. I used about 0.4oz of the 50N...it's a relatively big gap between the sleeve and leg obviously but it flowed much better brass. Not bad, but I likely used more than I needed to (used about $14 of silver for the fork). 
Then, after I cleaned up the brazed legs, I welded the crown pieces to the sleeves in the fixture. I didn't have any problems at all with the silver doing weird things while welding like i read about in someone else's post on seat tube sleeves. I was at around 52amps for the crown piece/leg joins and 57 for the crown/steerer joins. See pics for the results (excuse my welds, still need more practice - and advice!).

Cheers,
Whit


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## Walt (Jan 23, 2004)

*Looking good!*

Some .058 will save you a lot of hassle (keeping things from coming out of alignment) and silver. Looking good, though!

Put a real tire on that darn thing now...

-Walt


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## AKamp (Jan 26, 2004)

Whit,

I can't help you at all but your fork is built similar to a Type II from Steve Potts. On his blog he shows building one and I would imagine he would answer any questions you might have. Beautiful work by the way, it looks really nice.


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## pvd (Jan 4, 2006)

Are the sleeves there to add a lot of weight to the fork or to make it look unnecessarily overbuilt? I really don't understand what these are for.


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## geckocycles (Sep 3, 2006)

It looks nice but......I wouldn't ride a .035 fork. Especially in the crown section. Remember any fork or stem failure means face on the ground!

You could tig the top first using the legs inserted partly to fixture it. After tig pull the legs out and clean, flux and then silver solder. This will also help to normalize and stress relieve the tig area. Personally I would braze the whole crown and silver in the legs. I also have brazed over the tig joints. 

Soldering the legs in first then tig would burn the solder if it was close to the tig area and if you got too much penetration on the tig it would would contaminate the tig weld.

Silver is not structurally strong filling gaps. .005" to .01" is as much as I would do. Any more than that I would braze it.

When I was building Zinn's we had True Temper do lots of stress analysis, cycle and destructive testing on different joining methods. Brazing won every time with never a joint or tube failure as far as cracking and catastrophic failure. Annealing a tig joint came in second and brazing over tig was the same as just brazing as it anneals the tig joint in the process. I was never fond of tig tacking and then brazing either although it does really aid in production but also contaminates the joint and brass flow was hard to impossible to get to flow perfectly. We never had an issue though but while I was brazing I could tell it was more difficult to sweat the joint in. I don't recall if we had True Temper do any testing on that method. I think we did and it must have tested OK as we did that allot.


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## Meriwether (Jul 26, 2007)

*rationale rant...*

The reason I am trying to build this type of fork is that I thought it'd offer more strength (but added weight unfortunately) to the crown where a rigid fork mostly flexes and fails, but also perhaps a less harsh ride because of the thinner walled 1" x 0.035" legs. I used to ride a Fat Chance Yo Eddy fork for my 26"-wheeled bike many years ago and loved the way that fork rode. Now that I'm solely riding 29ers, I felt that the sleeved-crown fork would be a way to get something more like the Yo Eddy quality ride but a bit beefier/safer for a 29er with disc brakes. The two I've built so far are definitely heavier than say Walt's segmented forks (nearly 2.5lbs for the one I just finished), and ride quality is so subjective that I'm not sure many would notice or care about the difference. But I also like the design simply because I think it looks cool. I love the look of a lugged frame or fork, but I'm not sure they are any stronger than a tig'd frame or fork, although Mr. Peterson would beg to differ.

This is NOT a new idea. I grew up seeing the Potts' Type II forks on Mt. Tam and I think that has influenced my thought process. He uses a thinner-walled leg to soak up the rough stuff brazed into a thicker crown to increase strength. Of course, there were no unicrown forks back then so the Type II was out of necessity rather than a purely functional design but it's lasted for a few decades because they ride nice and are strong as bull. Willits makes a Type II fork as well, and several other builders have done these type of forks in the past. Bronto Bikes is making a sleeved segmented fork (the UDO) which is really sweet looking.

http://www.stevepottsbicycles.com/type2.php
http://stevepottsbicycles.blogspot.com/search?q=type+II+
http://www.brontobikes.com/forks-bronto-mountain-bike.php

To answer a few questions:
Gecko - I think I didn't write in my first post but the crown sections of the fork aren't 0.035" they're 1.125" x 0.049". The lower legs are 1" x 0.035" but the axle to crown for this fork is only 435mm - so it's not a long, suspension-adjusted 29er fork that would be more likely to fail.

Walt- those Fire Cross tires are cool for a monster cross but suck for a mountain bike...they're off! They were tubeless and I ripped a hole in them on of all places the Switzerland "trail"...


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## pvd (Jan 4, 2006)

The BOI forks from Fat City used a 1" butted top tube for fork blades. RC2TT 9/6/9. I've used this blade on many segmented 450 & 470mm forks with no issue. That will give you the ride quality you liked in the Fat Chance fork. The key on these forks is to make sure the whole fork flexs. You want the blade and the strut to flex for maximum strength. Too stiff on either side initiates failures.

I'm a real hater on sleeved forks and seat tubes. I just don't see how butted tubes don't address the issue. On forks I see them as just being a huge stress riser.

For longer forks, silver braze a strut into the fork for additional support.


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## Meriwether (Jul 26, 2007)

PVD- thanks for the advice on tubes to use for fork blades. I wondered if those TT's would work, or some externally butted seat tubes (1.3/.6/.9) for blades but was concerned the 6 in the middle would be too thin. Apparently not. I have never seen that kind of bridge in the middle of the blades before, makes total sense and it's a really nice looking fork! I will build my next segmented without the sleeves. Definitely less work to build up w/out the sleeves.

Gecko- I didn't really respond to your advice on brazing the crown and then soldering the sleeves since I don't think my brazing is good enough to do it that way yet. But thanks for the words of wisdom on that. Makes sense about the silver contaminating the tig weld, best not to risk that on a fork if I don't need to! 
Also, I know this may be getting a bit off topic but since it has to do with brazing strength vs. welding strength I hope all are ok with me bringing it up. 
I've been pondering the True Temper test results for the joining methods you wrote about. I've always heard that brazing is the strongest but then remembered reading about Bontrager's test here: link (scroll down to Section II). 
I'm wondering what you thought of the graph and it's comparison to your experience with the True Temper stress tests.

Thanks everyone for the feedback, I have learned a ton.


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## geckocycles (Sep 3, 2006)

I will concentrate on the steel tig vs brazing tests on RCB. You will notice that the Tig joining methods resulting higher RC at the joint. Just measuring hardness is one thing but as you start to work the joint repeatedly that is when things start to work harden even more. This makes the tube brittle and crack. Tig bikes will generally crack at the end of the weld when it fails and a brazed bike will bend. If continued to get stressed the brazed tube will eventually crack too where it was buckled.

The True Temper tests were done by cycling the tube many many thousands of times but staying with in the yeild point till it failed. It was noted in every case that the tig welded ones tube failed where the weld material met the tube. Brazed joints with a small fillet as I do bent about 1/2" back. I used OX3 1.375" DT joined to heavy HT material for the tests. Lennard Zinn tig welded them if I recall and I did the brazing. I am not that good at tig welding as he was. I get it done but I have a much larger heat effected zone than he did when it came to tig welding. I am better now but my skills are better known in the brazing circles.

I prefer brazed joints because when I mess up on a ride I want to be able to get home and not be carrying my bike in two pieces. I have had HT's rip clean off on both AL (Crotch Rocket) and steel tig bikes (Raleigh). I have bent my share of brazed bikes but have always been able to ride home. I have done literally hundreds of repairs and found that this be the case in most all of the repairs. I like the whole number and data thing but real world results I place the most value in. Sure I have seen some tig bikes bend too but not very many. Far less that what used to be before all the cool tubing we have now that is being designed for tig welding with paper thin center sections. For me not very practical for my bike is always at the bottom of the bike pile in the back of a pickup on rough back country roads.

Chris King steel welded his frames with a torch. Both Jay Carney and I fell into the same hole in a field at a walking pace and both our bikes bent. His both DT and TT bent and mine just the TT. Jay was riding CK's world tour bike and I was riding a Mantis Sherpa. I'm sure if we were riding tig bikes we would of been carrying the bikes back home.
My VVA 26 was tig welded but I had my welder weld it and he annealed the joints with a torch. No joint ever failed. 25" frame with 25" TT and 22" long CS. The stays were segmented as all VVA's were. I lived on that bike for 3 years putting 100 mile days every day fully loaded. Raced the hell out of it too.

When I do a tig bike, I purge the tubes like I would building a Ty bike. This was also tested to be the best way by True Temper. Cut a joint apart, one purged and one not and it is very clear the difference in tube quality on the inside. I have even heard of a guy purging brazed frames. I have not tested that though but all my tubes are sealed with no vent holes except for the tig frames. The brazed frames will float wheels high in the air. I know 2 guys who lost their bikes when they filled with water and sunk nearly drowning them. One at the lake at the Clunker Classic and the other in a river crossing in the back country.


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## Meriwether (Jul 26, 2007)

Thanks for that information and experience Gecko! I'll need to digest that more, lots of stuff in there. I have cracked a couple of tig bikes (ti soft-tail, steel hardtail) but never had one fail so I had to walk home (yet...knock on wood!).

As for the fork build process, I received the below tips from someone making similar forks and wanted to share:

_Always silver in your legs into crown before the fork is assembled, any tension on the two parts will make the silver flow difficult.

.0015" to .003 " max clearance between parts for silver, absolutely clean and fluxed before silver brazing.

The beauty of silver and brass is that you get a complete bond, do not settle for a partial joint, (good enough just leads to trouble).

Make sure all flux is completely soaked and cleaned off before tig welding, any contamination to the tig weld by flux is disastrous!

Make sure you use high quality flux, ( 1650 f ) , do not overheat or burn the flux, take your time and clean everything properly. 
_


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## geckocycles (Sep 3, 2006)

There are silver alloys that will fill bigger gaps. 45% will fill bigger gaps of .005" easily.

I would have to cut it open and look to see what happens. I would probably run a ream through the tangs after tiging the crown part is what I would think would happen or open up the distortion with a die grinder and sanding drums. There probably won't be that much if you are careful with the heavy wall sleeve material. Dress the inside of the tube so there is a few thousands of clearance and that should be good enough for any misalignment issues. I guess I would have to play with it to find the best way.

My tigs run on the hotter side and not just puddled on top on the cold side. I would be leary of sucking the silver into the steel even if it never even penetrates the weld. I have seen what the insides of tigged tubing looks like even with a clean tube inside that is why I purge everything.

Any other thoughts on this?


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## Bronto Bikes (Oct 26, 2011)

.058" Sleeves with appropriate sanding on the interior. TIG welded first then brass brazed. I fuse the "blade" to the sleeve on the interior. I don't think it is necessary to draw the brass or silver all the way through the sleeve joint. If the blade is hooked at the top and bottom of the sleeve you are all set.


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## JaquesN (Sep 14, 2009)

It's been stated before in this forum that .9mm (=~.035 in) is too thin for a segmented fork.

http://forums.mtbr.com/6750183-post3.html

"I built some .035" x 1.125" tubing forks at one point (maybe 10?) and I can tell you that it's not a great idea."

Sorry if I'm missing a nuance here, and I don't want to stir up trouble, just want to learn from others' experiences. PVD was talking above about using a 1" 9/6/9 tube and Walt was, I believe, talking about using a different butted tube.


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## cataño (Sep 7, 2009)

Blade length and application are going to play a big part in what tube is appropriate for a given fork. Weren't the 9/6/9 1" tubes PVD referenced used on rigid non-sus-corrected forks for 26" wheels? A tube that will work fine in that application isn't necessarily going to be the best choice for a sus-corrected 29er fork with blades that are substantially longer.


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## JaquesN (Sep 14, 2009)

> Blade length and application are going to play a big part in what tube is appropriate for a given fork.


That's true! If I'm not mistaken, one respected member of this forum stated that he thought straight .049 was a good idea, and another stated that a 9/6/9 was a good idea. That's a big discrepancy, even allowing for a good deal of difference in blade length. PVD's point about allowing for flex is very interesting, and maybe there's no contradiction - either you build in a lot of rigidity or you build in flexibility. I'd just like to hear a bit more about it from those who have done it.

I have built only four segmented forks, so I have nothing to offer but questions. I like making them, but having one break is not the kind of learning experience I need to have first-hand.


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## Schmitty (Sep 7, 2008)

What you could do for a 26" old school geo canti braked biked (YO!) does not apply to a 29" susp adjusted disc bike.

-Schmitty-


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