Tube replacement

[mayan42]

After finishing frame number 1, an un-planned incident resulted in a dent in the downtube (long story here http://www.velocipedesalon.com/forum...ned-35413.html)

So, I thought I’d document the replacement of the downtube here, from a complete newby perspective. After a bit of advice on the above thread, I went for it, and here are some of my findings and thoughts, plus a few pictures.

My starting point was a finished frame (lugged, brass brazed) with a 3 inch section cut out of the down tube.

DSC_2895.jpg

Plan A – Melt the brass out, and pull the tube out

I plastered a lot of flux all over the head tube / down tube joint and then went to work with the torch, trying to heat the entire downtube segment so I could pull it out, leaving the headtube and lug untouched. After blasting the head tube lug with full heat for aeons, the end result was a black ugly mess, with maybe half a pea sized blob of brass sitting 0.5 cm down from the lug point.

Result – 0 / 10

DSC_2896.jpg

Plan B – Cut the tube right down and then melt / peel off the segments from the inside of the lug (courtesy of bencooper)

So, I cut off most of the tube, leaving about an inch to grab hold of and went to work with the hacksaw to cut a notch down the tube to the lug to act as a weak starting point. Then focused the heat on the inside (ie the dead tube) and with the pliers tried to peel off the tube. A got a few chunks off this way but found it hard to remove the sections of tube closest to the headtube – because of the way the headtube curves it makes it really hard to get in close without damaging the headtube. For the BB / downtube joint I got maybe half of the lug clean

Result – 3 / 10 (casulties included one screwdriver, two small files and a pair of pliers all of which got melted / bent during the heating stage)

DSC_2898.jpg

DSC_2900.jpg

Plan C – grind the tube out from the inside

With the bottom bracket / downtube joint, this worked really well, as you can get un restricted access right down into the lug. So using a combination of grinding and sanding attachments on the drill head, plus files and sandpaper, I went through the down tube, back to the original lug. This was cool cos you eventually grind through the silver tube back to the gold brass and then through that to the silver lug again so you have a brilliant visual indicator of your progress. With the head tube, again, the restricted access proved really tricky, and I couldn’t get a power tool in close enough, so still had a significant chunk of the remaining tube inside the lug. This was incredibly slow..

Result – 6 / 10 (casulty - one dead drill that I seemingly burnt out whilst doing the bb)

DSC_2901.jpg

Plan D - ?????

I was out of plans at this stage, the bb lug was clean and ready to go, but the head tube lug still had a significant chunk of the old tube in it, with no way to get purchase on it to pull it out whilst hot or to grind / file / sand it out. At this stage I’d been fairly brutal with the frame, putting a huge amount of heat into both joints and some fairly harsh grinding and physical treatment of the frame, so I wasn’t entirely sure of any structural damage I’d caused….so I felt from here on I really didn’t have anything to lose…so… I cut the tangs of the head tube lug and filed / ground the lug / dead tube flush back to the head tube. This resulted in a reasonably (!!!) flat base on which to fillet braze the new tube. My fillet brazing is very much in the beginner stages, and the result looked a lot like lumps of chewing gum holding the tubes together….but the tubes were held together, at least for now.

Result – short term - 10 / 10. Long term – to be determined….

(picture taken before brazing)
DSC_2922.jpg

I’ve built the frame up and taken it for a very gentle, very short spin and I didn’t die in a horrific accident, and I had a really good look at all the joints after I disassembled the frame again. So, it looks like its holding up for now.

DSC_2930.jpg


Things I’ve learnt –
* Removing a tube is 10000000000 x times harder than putting it in there in the first place
* Its next to impossible (for me) to get an area the size of a typical lug up to temp at the same time
* My joints were actually pretty dam good. During this I got to see the inside of the joints, which is a pretty good deal, and they looked great, brass all round and full penetration – this confirmation of the original build made the whole exercise worth while (nearly!)
* Removing a tube is really really hard
* Did I mention how hard it is to remove a tube?


Thanks to all for the advice in the original thread. The frame is now drying after being painted (rattle cans in the shed) and I’ll ride it gently with the full knowledge that its a complete and utter bodge and with the expectation of a failure at the some point in the not too distant future.
I’ve ordered tubes and lugs for frame numbers 2 and 3 (and for anyone who read the original thread –I’ve ordered the tools to finish the frames myself as well!!)

[e-RICHIE]

You should have removed the lug from the head tube (very easy) rather than remove the tube
from the lower head lug atmo. Replacing the lug and tube is then very easy. Think it through atmo.

[mayan42]

Ha ha ha,
As soon as you say it, its incredibly obvious!!! So obvious I cant believe I didnt think of it....
Next time!!

[e-RICHIE]

Ha ha ha,
As soon as you say it, its incredibly obvious!!! So obvious I cant believe I didnt think of it....
Next time!!

Next time ask.
And then take the direction atmo.
There will be a next time.

[duanedr]

You should have removed the lug from the head tube (very easy) rather than remove the tube
from the lower head lug atmo. Replacing the lug and tube is then very easy. Think it through atmo.

A friend gave me a mid 90's Bianchi with a buckled down tube and I thought I'd try to replace the DT. More for the learning than to ride it - it appears the frame is still slightly twisted from the crash. I did in fact take the lower headlug off. Eventually. I wish I could say it was part of my logical and well thought out plan but, I'd be lying. I messed up the downtube so badly the lug distorted so, I just worked my way deeper into the frame. The DT at the BB is ovalized (and the lug is obviously as well) so, I'm hoping I can order a standard down tube (whatever size) and squash it to fit that lug and I'll add a new lug to the headtube joint to fit the round end. I hope it wasn't a proprietary sizing... If it is, what are my options? New BB or cut off the lug socket and fillet the DT at the BB?

Glad to hear you had a similar experience and learning!

In Way Over My Head
Duane

[afwalker]

Thank you Mayan42 for sharing your experience.
I've tried removing tubes and they are dang hard! Makes one appreciate how well silver is at holding it all together. Maybe try a rosebud.
Thanks eRitchie you always make it look easy! Those multi-thousands of frames you've made are the envy of us all.
eRitchie does have some photos sets of his frame repairs, I've seen a couple and it still belies the effort involved.
See if you can catch the subtleties in this great set oops atmo - - a set on Flickr
cheers
andy walker
Walker Bicycle Company | | Walker Bicycle Company
Flickr: afwalker's Photostream

[e-RICHIE]

Thank you Mayan42 for sharing your experience.
I've tried removing tubes and they are dang hard! Makes one appreciate how well silver is at holding it all together. Maybe try a rosebud.
Thanks eRitchie you always make it look easy! Those multi-thousands of frames you've made are the envy of us all.
eRitchie does have some photos sets of his frame repairs, I've seen a couple and it still belies the effort involved.
See if you can catch the subtleties in this great set oops atmo - - a set on Flickr
cheers
andy walker
Walker Bicycle Company | | Walker Bicycle Company
Flickr: afwalker's Photostream

Thanks for finding that - I knew I had a similar series cached. That some good shit right there atmo.

[Andrew R Stewart]

It's been said by far more experienced guys then i that you learn much more from your mistakes and the attempts to make them good. Also repairing frames. Andy.

[NBC]

duanedr....

that bianchi you have, might it be one with columbus max tubing ? i know there were some, but don't ask me about model names etc

NBC

[NBC]

e-richie..

are those the royal eisho lugs that were talked about in a thread a few days ago ? i like them :)

were they the same lugs that nagasawa used also ?

thanks

NBC

[devlin]

I'm just about to do this with a top tube. I have been going over it in my head trying to remember all the advice I've learned on here. I decided in the end the easiest way was to completely remove said tube and lug. The seat cluster is a different case. I have fast back stays, should I unbraze those and remove that lug as well?


Edit: It's seems from Richies pictures I may not have to. Time to get stuck into I suppose!

[duanedr]

duanedr....

that bianchi you have, might it be one with columbus max tubing ? i know there were some, but don't ask me about model names etc

NBC

the Columbus sticker says SBX. I haven't heard of it before.

[e-RICHIE]

e-richie..

are those the royal eisho lugs that were talked about in a thread a few days ago ? i like them :)

were they the same lugs that nagasawa used also ?

thanks

NBC

No - these were Otsuya parts atmo.

[MrkiMedo]

With the bottom bracket / downtube joint, this worked really well, as you can get un restricted access right down into the lug. So using a combination of grinding and sanding attachments on the drill head, plus files and sandpaper, I went through the down tube, back to the original lug. This was cool cos you eventually grind through the silver tube back to the gold brass and then through that to the silver lug again so you have a brilliant visual indicator of your progress. With the head tube, again, the restricted access proved really tricky, and I couldn’t get a power tool in close enough, so still had a significant chunk of the remaining tube inside the lug. This was incredibly slow..

So if I understand correctly, you have used bronze with lugs with first frame? How did that go, and would you recommend it to some other beginner? Usually people recommend using silver on first frames since it is easier to flow into the lug.

[mayan42]

So if I understand correctly, you have used bronze with lugs with first frame? How did that go, and would you recommend it to some other beginner? Usually people recommend using silver on first frames since it is easier to flow into the lug.

Yes, I used SIF bronze 101 filler with a cast lugs and the lowest grade of columbus tubing.
As I understand it, (and I'm happy to be corrected here by someone who actually knows what they're talking about...) silver flows a lot better / smoother ie it "wets out" better and at lower temps.
Brass is much better at filling bigger gaps but flows slower and at a higher temp.
The big thing here is "fills bigger gaps" , my mitres were OK, but almost certainly not perfect. But also of major consideration for me at least is the cost, I'm guessing silver is at least 10 x the price of brass.

My experience, it went fine, but I dont have a huge background of experience. What I can say is that when using silver for the brazeons like cable guides, bottle bosses etc, it felt more graceful, artisitic, composed, and gentle, compared to the slightly agricultural feeling of the brass - I'm sure a lot of this is me learning heat control, after all, its the same process just at higher temp, and I'm probably not yet as comfortable working at those higher temps.

Before the incident that caused me to replace the down tube, I was confident in the structural integrity of the joints, based on being able to observe brass pulled through to the other side of all the joints. Whether I over -heated the tubes in the process of brazing is another question, and presumably one that will only be answered over time due to an decrease in fatigue resistance

[mayan42]

Sorry, that was a long reply, and I dont know if it even answered your question!!
Would I recomend it to another newbie?
Yes, if you are on a budget and arent 100% confident that your mitres and lug fit up is 100% perfect
No, if you have no worries about budget and have perfect mitres and lugs

[wort]

When I first got my torch, I got an old damaged lugged frame from the local Bike Collective, and used my torch to attempt to disassemble it. I was amazed at how much heat it took to get the main tubes to come out of the lugs (I am pretty sure this frame had been brass brazed, not silver), but I feel like it allowed me to get more familiar with my torch. (And it was fun!)

[MrkiMedo]

Sorry, that was a long reply, and I dont know if it even answered your question!!
Would I recomend it to another newbie?
Yes, if you are on a budget and arent 100% confident that your mitres and lug fit up is 100% perfect
No, if you have no worries about budget and have perfect mitres and lugs

Thank you for your reply the length was justified :)

I was under impression that bronze+lugs is off limits for beginners, and your example has proved that it can be considered.

[MrkiMedo]

When I first got my torch, I got an old damaged lugged frame from the local Bike Collective, and used my torch to attempt to disassemble it. I was amazed at how much heat it took to get the main tubes to come out of the lugs (I am pretty sure this frame had been brass brazed, not silver), but I feel like it allowed me to get more familiar with my torch. (And it was fun!)

That brings me to second question. I have collected few frames that I got either for free, or nearly free, that I hoped to use as source for practice material. What is the best way to chop the frame to get as many usable practice parts. Is it realistic to expect that lugs can be saved and used for practice?

Here is the best looking one from my scrap collection (it has broken seat tube):

1zxwc2u.jpg


others are of much lower quality.

[Gattonero]

Thanks for finding that - I knew I had a similar series cached. That some good shit right there atmo.

Thanks for sharing, is great to see how you work, albeit only on pictures