Important - suggestions / help required!

[Sprucey]

Well, I have finally located the source of the creak in my Oz frame / drive chain.

I thought the BB may be loose so I check tightened it, only to find the whole aluminium bottom bracket shell sleeve is now rotating in the frame!

It's not disastorous as the bike is still rideable but the play will only get worse with use.

So, I am looking for suggestions on the best way to fix it - the bike has already had a warranty claim on it so that is not an option - I also want to keep it going - I like riding it!

I have tried to tap it sideways with a hammer (sorry, a knockometer!) and it does not move - it is simply twisting at this stage. It looks like the sleeve does not hace flanges on it - the outside edge is flush fit with the hole in the frame?

My initial thougts are not to remove it but to drill two holes each side on the top and two more underneath and fill the cavity around the sleeve with epoxy adhesive through some sort of injection gun. Adhesive in through one whole, air out the other until the adhesive runs out of all holes. That way the outside of the sleeve would be incased in adhesive and should not budge.

Possible problems:-
1) cannot etch/treat the surface of the sleeve and inside of the carbon BB cavity to achieve a good bond?

2) It will add weight - however, correct choice of adhesive and filler/thixative etc should keep that as low as possible. It may help stiffen up the BB area of this frame - I have always thought it very flexy sideways.

3) It may weaken the frame in that area but I think 4  x 5mm holes, back filled with adhesive should be OK.

I would welcome your thoughts /comments about this problem (sorry, "Opportunity"!)

Has anyone else had the same problem? Has anyone had cause to remove the sleeve or seen it's construction? I have looked at the exploded diagram PDF of the Oz and it looks simple enough.

Sprucey

[will]

Ouch...
I've always feared the metal - composite interfaces in any machinery. (Including some of the stuff my Co. builds in the HVAC industry.)

Here's my 2 cents (tuppence?) on the issue: I like the idea of drill it and fill it. One problem is that it's going to create a severe shearing point load on the resin plugs. If you go this route, you'll want some fibers in your plugs instead of pure resin.

Perhaps more effective than the plugs might be a thin layer of epoxy inserted between the sleeve & the frame.

Actually... you could drill your holes, plug the internal outlet, squirt the resin/fiber into the hole, rotate the loose sleeve to smear the epoxy in between the layers, and repeat.

JB Weld has an aluminum impregnated version that may work... I'll bet you know some boat builders that deal with aluminum & epoxy joints.

Or, you could sell me your Oz super cheap [smiley=groucho.gif]

TTFN

[Sprucey]

Hi Will,

nice try and tuppence wouldn't buy it! ;-)

You are right about the fibres - that was always my intension - fibres for cross linking/sytrength, micro balloons for volume and colloidal silica for "stickiness"

I like the idea about rotating it to get it wet/coated.

the problem with rmoval and re-insertion is that I think it's only in contact with the frame in three places - the two side mouldings and the centre spine contact area - only a few sq mm of contact area. Filling the void with epoxy mix would link it to the inside faces of the frame (if I used enough mix)

Thanksa for your comments. I am not going to rush this - have just done a 2 hour ride this evening on it and it's still good.

Sprucey

[Frankd3000]

Drill one 4mm or 5mm hole through the frame at the bottom of the bottom bracket, then nut-n-bolt it in place. Use Ti hardware if you're that concerned about weight. Back it up with epoxy.

I don't know if/how this will affect the strength of the carbon in that area - just a shot, really. Look to the simplest solutions first.

[Carbonman1]

Hmmm,  I'm always sorry to hear of bond failures in unlike materials.  I guess with time and vibration some will give in.  If it were my frame, I would remove that sleeve and give it a thorough cleaning and inspection in prep for a rebond.  Injecting a viscous epoxy into the void wolud use a huge amount of material, and the carbon dust from drilling could inhibit positive bonds.  With the bb shell out of the frame, you can do a better job of bonding it than K2.  Rotating the coated sleeve and applying the bonding agent to the trailing surfaces to make sure of a good seal, should yield great results.  If you still like the drilling idea,  there may be some more fluid adhesives that may flow to all the surfaces that you want .   My two cents,  good  luck on it though...

[Carbon_Kiwi]

this is kinda related - my seat post sleeve did this very thing [quite a while ago now] i managed to pull it out of the frame a resonable amount [not all the way mind] and re-bonded. granted - not the same kind of torque as a bottom bracket shell, but it hasn't budged since...
it is disconcerting when this kind of thing happens, but hey - how many frames can you fix at home with some glue [in many cases]

[Frankd3000]

it is disconcerting when this kind of thing happens, but hey - how many frames can you fix at home with some glue [in many cases]

So THAT'S why they call it BondFast.

(ba-doom boom - tshshshsh) [smiley=laughing.gif]

[Sprucey]

Thanks for all your comments guys.

On reflection, I think that removing is probably the best bet - as Carbonman says, I can clean and prep it and clean out the inside of the frame before re-inserting and bonding.

I just need to get the correct epoxy glue to bond the carbon frame to te alloy sleeve.

I will look at it over the weekend and report on progress next week.

Sprucey

[Carbon_Angus]

Mark, good luck and this might be an on going problem with the carbon frame as we put more and more miles on them (mine is vertical in the garage at the moment, though) , so if your fix ix a success it should be archived somewhere here.

Just be sure you don't mess with the threads, there is not much there to begin with and they can strip, so just be extra careful upon removal and reinstallation. (I'm sure you already are)

It's my opinion that the main pivot  and not the BB is where all the flex comes from, but if you notice your fix makes it stiffer, I wanna know that, too.

[smiley=beer.gif]

[shovelon]

Sprucey,

So while it is out, could you draw up measurements on this thing and take some pics?

Would be a good idea to have a spare bb shell or 2 if the threads fail. I would be willing to give it a go.

Terry

[Simon]

Mark
if you need a hand with ANYTHING give me a shout.
Simon.