Help S.Oz.S. My Oz has suffered a serious injury

[Thunderchild]

Saturday while riding back down one of my favorite local single tracks, I was out of the seat and noticed that my seat suddenly moved to the right a bit.  I immediately thought that my seat tube had become de-laminated.  Upon examination, my seat tube was still in the frame, but had sheared off at the top where the seat post clamp attaches!!!!   The remainder of the seat tube is firmly attached to the frame.  I will post pictures tonight.  I didn't know the tube had a shoulder.  The thickness of the tube inside the frame is thinner than the top portion that the clamp attaches to. 

O.K. I hope your minds are all working on how I am going to fix it.  My Thoughts:  Have a machine shop carefully ream out the remaining tube in the frame and have a new tube insert made, stainless or aluminum?  Use appropriate epoxy to hold the tube in place. 

Any other thoughts.  Has this happened to anyone else.  Lastly check your seat tubes! 

Thunderchild

[shovelon]

What a bummer. I recall Simon said something about this. I have heard of the seat tube delaminating. I also have noticed that the insert wall is paper thin at the bottom.

If the insert was reamed out, could an insert be made for a 26.8 post? That would thicken up the insert. I would make it from 7075 alum, which the machine shop would enjoy, and the strength is comparable to 304 SS. McmasterCarr has a great deal for small lots of 7075 alum. A 12 inch piece, 1.25" (31.8mm)diameter, part # 90465K15,  is book listed at $23.87. Most others have a minimum charge of at least $50. I make sure I ask McMaster for a certificate of conformance for your machine shop to verify.

Terry

[IMO]

Sounds like you need an insert with a fairly substantial shoulder on it. From your description it sounds as though the original ones are .3- .6mm walls inside the frame, with 1mm -  1.5mm of metal outside the frame the clamp fixes to. Then the 1.5mm section has fatigued and detatched from the thinner lower section. The lower section being bonded in with Loctite  / Araldite  epoxy, so removing it will be a right P.I.T.A.

I have a no ideas on an easy fix. MAchine down a large billet of ally to make a flanged section, with a 27.2mm??? insert then bond the whole thing in. you might need to source some thick walled tube and get the thing turned down, I would increse the length of the clamping area if you can .

Willbe checking mine closely, aamoi , did you run your seatpost the full lenght of the insert, so it poked out the bottom ??
Mine doesnt, and it only goes about 2inches into the frame , and I'm sure its not right

[Simon]

Okay this is an easy fix.
I have a drawing available that I drew up (all measured from an origonal) take this to a machine shop and have
this made then  just re-bond it back in.
It all very simple you'll soon be back on the trails.

Okay not so simple now as all my drawings in the in the files section and my gallery have all gone 
That appears to be everything, seat insert,sealed bearing conversion,floating brake system and aluminium s/arm conversion etc, not sure I have any of this backed up 

send me your email address and I'll send you the drawing this I know I still have  .

Simon 

Forgot to mention I just got a hacksaw blade and put that through the stuck in tube then re attached the blade to the handle, then I very carefully cut a series of slots (about 4) down to the thin insert (go very carefully). Then I kept working penetrating fluid around the insert and with a flat bladed screw driver and a hammer carefully tapped the top edges of the inserts in towards the centre until they broke away from there bonding,it didn't take long.
Make sure you clean up everything and de grease before bonding in the new insert. 

[Simon]

Here you go,just had to host it somewhere else first.
Obviously make it from Aluminium 
Simon.

[Thunderchild]

Great information all.  Thanks for the drawings and the removal idea Simon.  Obviously, I am not a metallurgist, but tell me why aluminum would be better than stainless steel?  Wouldn't stainless steel be more durable and fatigue resistant. 

IMO, I had the seat post all the way through the tube with just a bit of seat post showing at the bottom until last month.  Last month my friend re-fit me to the bike and I raised the post up a bit so the bottom of the seatpost was just a 1/4 to 1/2 inch from the bottom of the tube.  I also have close to 9000 miles on this frame. 

Thunderchild

[Simon]

Stainless would probably be fine as long as it compresses okay without to much effort enabling you to clamp your seat post,
if it doesn't then you've gone to all that work only to find your unable to clamp your post without having to use excessive force on the seatpost clamp.

Aluminium is what was used from stock and I think you may of answered your own question why yours failed,
maybe you need to purchase a slightly longer post so you can ensure you have it going all the way through.

Good luck

Simon.

[Old Proflexer]

Great fix Simon - appreciate all you do -

OP

(good karma stroke for simon)

[shovelon]

Great information all.  Thanks for the drawings and the removal idea Simon.  Obviously, I am not a metallurgist, but tell me why aluminum would be better than stainless steel?  Wouldn't stainless steel be more durable and fatigue resistant. 

IMO, I had the seat post all the way through the tube with just a bit of seat post showing at the bottom until last month.  Last month my friend re-fit me to the bike and I raised the post up a bit so the bottom of the seatpost was just a 1/4 to 1/2 inch from the bottom of the tube.  I also have close to 9000 miles on this frame. 

Thunderchild

What seat post are you using. I find that carbon ones flex the top part of the clamp.
In fact I had to clamp extra hard on carbon to prevent slippage. Have since stuck with my Thompson on my Oz.

Terry

[shovelon]

Great fix Simon - appreciate all you do -

OP

(good karma stroke for simon)

I agree. Would never have thought of peeling from inside.

What gets me is the super thin wall.

[Thunderchild]

Shovelon, I have a used a K2 alloy seat post since I built up the Oz. 

A couple of more questions. 
1. Anyone care to comment if it would be an improvement to increase the height of the thicker section of the seat tube above the frame? 

2. Any down sides to machining the tube from existing tubing?

Status of Oz surgery.
My nephew is a Die Machinist and is dropping by tonight to look over the severed part.  He might be able to make the part for me for material costs only.      He was impressed with the drawing and the suggestion for alloy 7075.  Thanks Simon and Shovelon.  If he makes it, we should be able to turn a few more if anyone wants an extra.  Just expect to pay for material costs and maybe shipping.  My nephew is one of us as he owns a Disco Monkey that I helped him build. 

On another note, I started to build up my old 5000 frame to ride until the Oz is all better and found the already discussed cracks on the back of the seat tube by the water bottle mount.  The search for a local aluminum welder begins.  Simon, didn't you post a few pictures about welding a 5000 seat tube?  I searched but couldn't find it.  Anyone know the title or where it is? 

Thanks
Thunderchild

[Simon]

 

A couple of more questions. 
1. Anyone care to comment if it would be an improvement to increase the height of the thicker section of the seat tube above the frame? 

 

I wouldn't of thought so, the extra length may give more leverage,just my opinion no actual proof either way on this.

Simon.

[shovelon]

Shovelon, I have a used a K2 alloy seat post since I built up the Oz. 

On another note, I started to build up my old 5000 frame to ride until the Oz is all better and found the already discussed cracks on the back of the seat tube by the water bottle mount.  The search for a local aluminum welder begins.  Simon, didn't you post a few pictures about welding a 5000 seat tube?  I searched but couldn't find it.  Anyone know the title or where it is? 

Thanks
Thunderchild

That was mine. 

http://idriders.com/proflex/smf/index.php?topic=2850.0

[Thunderchild]

Pictures of the broken seat post are posted in my gallery.  My nephew machinist came over tonight to examine the Oz.  Here is the plan.  I am going to move to a 25mm or 25.4mm diameter seatpost and increase the wall thickness of the seat tube.  I will have the part made per Simon's drawing with the inside diameter adjusted for the 25mm seatpost.  Thomson's lists a 25 mm on their website; I will find out tomorrow if they have any in stock.







Thunderchild

[Thunderchild]

Oz seat tube update.  I have my machinist lined up.  Once the 25.0 Thomson seat post is in, he will begin.     

Damn hard tail has reminded me that I am not as young as I used to be.  Like I needed another reminder.  I miss my Oz!!

Thunderchild