Retro-fitting discs - is this correct?

[Frankd3000]

Well, I just sold some car stereo equipment, so it looks like the disc upgrade is going to happen sooner than I had hoped. [smiley=nod.gif]

The plan, for my 3000; install Avid mechanical disc on the Noleen CrossLink fork and same for the rear.

So, my thoughts on this are to machine the brackets at work, one for the front and one for the rear. What i'd like to know is what you guys normally do to "get things right". Do you put the wheels on, mount as much as you can and measure the living daylights out of everything??

Also, I know i'm putting a 160 mm on the rear, but I haven't decided on the front as of yet. I'm tempted to go with a 200 mm (and logic would dictate such), but I don't think I need that much. I'll have to see about this. Research abounds!

In the meantime, i'm thinking it would be possible to make the front adaptor so as to have it adjustable for any size disc. Whatever the case i'm adamant on having this piece welded onto the fork leg (I know a REALLY good welder, so it won't get messed up).

Comments, suggestions, anything would be appreciated. (other than to go hydraulic - NO!!!)

PATIA!

[Frankd3000]

And yes, i've looked at ALL the pics. Every single one.

[will]

Hmmm... that welder can do some great work but that thin wall tubing will develop some large grain structure in the process. If you're able to relieve the fork with some annealing afterwards, it may be just fine.
Remember, you'll be welding on the "corner" since the tabs line up nearly flush with the inner face of the fork leg.
I'm sure it'll be fine.
BTW, I'm 100% with you on the mech brakes. I've had it with hydraulic leaks on my bike and riding buddies walking it downhill.

Cheers,
Will

[Frankd3000]

I guess I shoulda mentioned that...... I was thinking on doing exactly what Old Proflexer had in his article with fitting to a Carbon fork - only by way of welding.

It would be an opportunity to allow for disc size flexibility, but more importantly, it would also be a way to keep from having all the welding located in one general area. Having it sperad around in the same manner that OP has I THINK it shouldn't be a problem.

Thanks for the tip, Will. I'll have to discuss this with my welder. I might have an annealing process available through work, but I have NO idea what it consists of. (anything to do with heat treating?)

[Old Proflexer]

something tells me that if you put a welding torch to that ultra thin aluminum on the leg - you'll soon be looking for another leg if you still want to use the rest of the fork.

IMHO - take the anodizing off under the plate size you want and bond the two together with my now outdated instructions in the 'how tos' -
i went thru this mental exercise many years ago.

measure the width of a leg, measure the width of the dropout where it enters the leg, subtract one number from the other and divide by two and you'll see what i mean.

[Mr.Ed]

 Annealing is heating and holding at a certian temperature and cooling at a certian rate. Mostly used to soften materails,or change properties in another way. If you do not anneal after itis welded, I would think you ste yourself up for cracking and premature failure.

I love my avid cable disc's, with the full metal jacket sealed system. Control-a-mania !!

[Mr.Ed]

Oh, and personally, I would'nt weld it  !!!...

One mistake and like OP said, you be searchin' for another leg..

[shovelon]

Andrew,

Do you  know the alloy to the aluminum? If it is 6061 you will have to do a full heat treat and temper. If it is 7005 you can weld and stress relieve as it will self harden.

Go to www.novacycles.com for weld procedure for 7005 alum.

Terry

[Frankd3000]

No no, no mistakes allowed. Not with my toys. Seeing as how there's already enough negativity (NOT meant in a bad way!!!) I think i'll look into two other options then.

Machined, bolt-on bracket - machine something that goes around the leg and use bolts to secure it. I can make the fit precise enough that I hopefully wouldn't have any problems with vibrations.

    and/or (but probably "and")

OP's bonding method - i'm not a big fan of bonding, but i'll give it a try. I haven't had enough experience with this type of holding method, so this is why i'm so leary. Yes, I fear the unknown (is it such a crime?). If anyone feels the need to chime in with the strength of the bonding now would be a reaaaaaally good time.

Funny thing - I just know that all this work will be worth it..... right? (the laziness in me speaking up)

I'm not a welder, so can someone please explain to me why this is acceptable when the forks are being built, but not now? The drop-outs, brake posts and tops are all welded, so...... what am I missing here?  [smiley=blankstare.gif]

THANKS for the replies, guys!!!! Appreciated muchly. Worse case scenario, if I don't feel comfortable with it i'll just stick with the V-brakes. Nice as discs are, I can live with V's. I have had the habit of making things difficult for little/no reason in the past and don't want to introduce this bad habit into my biking.

[shovelon]

Weld away my man!

Here is the lowdown. Here in the Americas we weld 6061 day in, day out. The sequence is clean, fixture, and weld. Some preheat may be necessary. But your 6061 will be annealed in the heat affected zone by the welding. Find a heat treat company to bring back up to T6. This will cost approx $100 bucks or so. Foes, Intense, and some other high end companies do this because they can pass the cost to you.

7005 alloy on the other hand is a proprietary material owned by EASTON. They have Alcoa extrude it for them for arrow shafts. It welds like a dream and is self heat treating. The only thing left to do is stress relieve, and this can be done during powdercoat. So you can see why 7005 works out so good for the Chinese and Taiwanese factories. Easton makes a royalty on every bike they make. The boutique builders like Foes and such can't crunch the numbers out so they stick with the 6061 alloys.

So if your legs are 7075, you are in luck. No heat treat required. In fact, if you let the leg sit for 30 days to work itself out the stresses, you will be fine.

The cheater method of welding 6061 T6, is to tack your mount on. Fill a large bucket with cold H2o. Weld the mount all around, and as soon as you let off the torch quench that hot weld in the cold water. You see, welding T6 generally drops the weld area to about T-0, then bounce back to T2 as it cools. But at this low temper it will not want to age to T6. By water quenching, it can go back up to T4. And at T4, the ageing process can proceed, right  back to T6 in a matter of about 6 months. The heat  treaters do this same proceedure but to expedite the ageing they store in liquid nitrogen for a couple of days.

So weld away.

Terry

[rapiddescent]

If I was doing it - which I wouldn't after seeing one crosslink leg catastrophically distroy itself in testing - than I would manufacture a sleeve and then weld an IS2000 configuration onto the sleeve.  The sleeve can be bolted onto the leg with small M5's with a nut inside.

The sleeve would have to take some thinking because of the D-profile of the fork leg but I'm sure you'll manage.

callum

[Old Proflexer]

i think you'll find many modern bonding materials such that the aluminum will rust before the bond fails.


i wouldn't take a torch to that paper thin aluminum on the leg and feel confident riding it -

i looked at making a sleeve as internal support when making my first few units and do some sort of riveting but couldn't get it a properly shaped piece inserted in the two holes in the lower dropout and situated internally to work properly.  after that, had my conversations with girvin, he indicated i seemed to him mentally unstable for even thinking such with the aluminum and suggested the much stronger carbon legs.

[Frankd3000]

OP, i'm still playing with this idea. Albeit, i'm just a little distraced with the Cloud Nine thing right now.

Can you shed a little more light on this for me, please? I already openly admit that I have very little bonding experience, and this lack of experience has me .... scared, really.

Would you think that one combination lends itself to greater strength over another? (ie al legs versus carbon, and bonding strength as a result)

PATIA! Your experience with this is invaluable knowledge to me.

[rapiddescent]

The carbon legs are FAR stronger than the aluminum legs.  Before disk brakes were popular quite a few people bent the legs in simple over-the-bar accidents with V-Brakes.

Proflex did test a disk brake repeatedly on one of their rigs before moving over to Vashon Island WA and successfully destroyed the forks resulting in HOPE (UK) being asked not to sell D-Clips for disk brakes.  I also destroyed a set doing the same thing.

I prefer OP's idea of bonding the sleeve rather then putting holes in it.  I would run the sleeve quite high up the leg - they used to bend just below the lower eccentric link so I'm not sure what you would do - run the sleeve higher or indeed much lower (to reduce the arc of force on the leg).  The D-shape should stop it from sliding round the leg.

callum /rd s

[kiwi]

if you take a lower link bolt out frank you will see how thin the legs actually are,i would spread the weld over a lot of area to lower the stress,and see if you can trasfer some of the load onto the dropout..
I would bond i think cos you can use the whole area of the bracket for bond not just the circumference of your bracket where it actualy touches the fork leg,