Adding a braze on seat clamp for repair?

[paredown]

Another day, another project.

I purchased this Dean frame with a slightly crushed seat tube (because I thought it would be cool to have a eponymous frame:banana:). As best as I could figure, someone had fitted a seat tube clamp with an inside collar that was slightly too small, so I think a seat tube was matched to the collar ID, and then clamped down.

Result was a small crack at the base of the milled slot, and a seat tube that would not take a 27.2 post. I carefully opened up the squished tube (you can use the end of a quill stem to do this if you are careful), then a little polishing with a home-made hone, and the seat tube is fine for a post.

I then filed past the slot slightly, and drilled a round hole at end of the slot--got an idea for the size from another frame.

So--all good so far, except you can see the small crack going horizontal--about 3/16" long--located where the milled slot used to end.

For round 2--or the rousing finish--I had the thought that if you brazed the correct size seat collar on there, and recut the slot, you would limit the tendency for any further cracking. ( I don't think it would, but I thought this would be a more permanent solution.)

Anyone have thoughts or opinions?

Picture attached is from half-way through--already have a 27.2 post fitted--crack is not really visible but it is on the right side, bottom of slot. (there's lots of discoloration in the area, because the powder coat had failed)

[Pi Guy]

I bet that would work just fine, assuming we are talking about a steel Dean. Your slot may be a touch longer than the seat collar you pictured but it wouldn't be too big of a deal to brass braze an extension onto the collar and then silver braze the collar on as usual.

[Doug Fattic]

What I would do is get some 1 1/4" 4130 tubing from Airport Spruce or Wicks Aircraft that has a wall thickness of 0.058". This would be a slip fit over the seat tube. You might have to taper the bottom so it completely covers the crack and doesn't hit the top tube in the front. I would use silver to braze this tube over the upper seat tube.

Next I would fillet braze with brass a binder bolt onto the slip tube. The Binder bolt would need to be mitered to fit a little better onto the slip tube. And yes brazing the binder with brass over the tube brazed on with silver will work.

[pbarry]

I like the new collar idea. That slot is really long, maybe cut it down 1cm? Did the relief hole take out the rest of the crack?

[David Kirk]

I like the idea of combining a few of the above. I think I would -

- shorten top of seat tube about 10 mm.

- braze a 1 1/4" slip tube over the seat tube extending down past the current slot in the rear.

- cut a new slot that does not go as far down as the old slot.

- slip a DKG alloy post binder collar on and call it a day.


All that said - brazing the part you pictured on would also work as long as you can make sure that the new collar covers the crack.

Plenty of good ways to make a long term effective fix to this one.

dave

[paredown]

I like the new collar idea. That slot is really long, maybe cut it down 1cm? Did the relief hole take out the rest of the crack?
Not really, since the crack was horizontal, off the bottom of the existing slot. This picture shows the slot before I did anything to it, so it was long to begin with.

By lengthening the slot past it, I thought it would limit the tendency for it to split more...

Thanks for the help everyone--I will take that frame building class one day!

[cachagua]

And somebody spank Dean for not relieving the bottom of that slot. Don't they know better?

On another note, though -- where do you get those clamping collars? I want one for a frame I'm working on.

[ultraman6970]

U can get those seat collars in any place that sells lugs and bike tubing. Those seat collars work great.

As for the relief at the bottom of the sleet... I have a frame that is like 25 years old w/o one and no problems what so ever since I got it made.

[paredown]

And somebody spank Dean for not relieving the bottom of that slot. Don't they know better?

On another note, though -- where do you get those clamping collars? I want one for a frame I'm working on.
I never got the whole story--these Dean Culebra steel frames were some kind of joint venture with Tom Teesdale (TET)--so I don't know if he made the prototypes or made all the frames as well, or if some other shop made the steel frames. But yeah, a relief hole may have prevented the problem, even with the fail with the seat post/clamp...

I did notice that on the last iteration he had of a similar bike on his web page, he'd added reinforcing collars on the head tube, and I believe on the seat tube as well...

The collar I grabbed the picture of was from Framebuilder Supply--but I have no idea about who is the best to buy such stuff from:
https://framebuildersupply.com/products/braze-on-seat-clamp-lug-for-29-8-seat-tube-and-27-2-seatpost

[cachagua]

Thanks, I'll have a look. "Framebuilder Supply", that's a place I want to know about! Not that I'm by ANY stretch a frame builder. A tinkerer, nothing more.

[C. Matthews]

Forget the collar, do the slip tube + clamp Dave K mentioned above.