Manny66 

So I have a Mondia from the 70's, Ive had it since 1981 and was my main bike when I was a teenager. A few years later I slammed int the rear of a pickup truck while riding and totaled the forks and creased the Head tube. Fast forward to 2018 and Ive finally decided to repair it for sentimental reasons.
I just had the original chrome stripped to be able to repair and braze in a new head tube.

Question 1, after the chrome was removed I noticed the rear dropouts look like the brazeing material is a little thin. Theres a clean gap between the dropout and the chainstays as if the joint is not totally filled completely with brazing rod., would rebrazing this area to fill the fine gap be a typical move, or is it fine and be should it be left alone?

Question 2. I already have replacement tubing and will be cutting the head tube in the center, heating up the lugs and removing the leftover tubing ,and installing the new tubing ,I will be heating the lugs up to reform the lugs to close as possible to original and installing the head tube and silver brazing it. I have Never made a repair like this but think I am in the right direction. Am I correct on this procedure or am I leaving something out??

Manny66 

Another view of the Droputs

Manny66 

The Damaged Head Tube.

Manny66 

And another shot.

Andrew R Stewart 

I'd be tempted to grind out the HT from inside the lugs. This frame is seeing enough insult to give it one more, the high heat level to pull a brassed tube out.

Since the drop outs have survived 40+ years I suggest leaving good enough alone. Andy

unterhausen

It's really hard for me to tell if there is a problem with the dropout. I would have it media blasted.

I agree with Andy. The likelihood of removing that head tube without injuring the lugs is slight. I'm sure the filler is brass. Doesn't take long to remove a head tube with a dremel. A sanding drum is my choice.

fietsbob

dropout likely , has to be removed, metal surfaces cleaned up, then re brazed..

Manny66 

So I got some progress done on the frame.

Manny66 

To This.Took a cut off wheel to it

Manny66 

grinded the inner tubing ,heated up the thin leftover and they slipped out.

Manny66 

Now all I have left to do is file everything down tighten the gaps ,make sure its clean ,and get it ready to braze. I practiced on a old univega frame before i tried it on this as I just played it by ear. So far so good.

Nessism

Be sure to check alignment of your new head tube to the rest of the frame before brazing it in place. I'm going through a down tube replacement right now and the head tube was out of alignment after removing the damaged tube. I aligned the frame to put the head tube straight and now I'm working on installing the new tube.

unterhausen

nice

Andrew R Stewart 

This is the moment to clean up the lug points too. Andy

Nessism

Did the lug pull away from the down tube thus creating a gap where the arrows point? Might just be the photo of course; it seems the focus was on the tool box instead of the frame. Anyway, if the lug did move I think that should be fixed before fitting the new head tube.

unterhausen

I would put money on the gap being a preexisting condition. And I don't gamble

Manny66 

No, the camera angle only gives that impression. The down tube didnt move at all.I was surprised how easy the head tube came off. I did as suggested, I grinded the tubing from the inside and thinned it down as much as I could without damaging the Lugs. As soon as I put the torch on it the pieces slid out to the ground,only one spot I had to use pliers as I didnt want to over heat the lugs. Everything came off clean. The new head tube slid right into place without any force or pressure. I need to find my thin barrel fine sanding attachment to give it a good cleaning.

mech986 

Any updates on your Mondia? Not much time to have it ready for Eroica, will you be coming and will you have a backup bike if the Mondia isn't ready? (paint and such)

Manny66 

Well Im going to braze it up this weekend because Ive been strapped for time, I want to make sure its as straight as I can get it so I expecting to dedicate a few hours to it.

As far as the L'Eroica ride, I have a spare Vintage Moser
bike that I can use but with all the rain here in the L.A. area and long work hours, I havent gotten as much riding in as I'd like. I could do the distance but I know i will be suffering with all those hills. Im still debating.

Nessism

Okay then, the gap was there from the beginning as unterhausen suggests. Even though the bike covered many miles (with the gap) before the damage I'd have a hard time putting it back together that way. Most likely it wouldn't matter but just knowing it's there would drive me crazy.

unterhausen

I would fill it when brazing the head tube in. Like should have been done in the first place. That area needs to be heated anyway, since the air will blow out.

dsaul

You'd be really bothered by my 88 Schwinn Prelude, on which the tubes were just square cut and inserted into the lugs. At least on the bottom bracket where they can be seen.

unterhausen

I wish I had saved the pictures someone took of the mitering on bikes of the '70s. They mostly removed enough material so that the tubes would fit in the lugs with no gaps at the shorelines. Part of the "magic" I guess. This included some fairly high-end bikes. This mondia is really good in comparison.