vee_dub

Hey' all,

I bought a second hand Columbus Zonal tubing frame for relatively cheap prices. Unfortunately it have ugly welding on it. Just wondering is there any possible way to hide those ugly weld before I respray it??

CHeer,
Dub.

PS: the frame been stripped and ready to paint except wanting to get rid of ugly welds.

potus

you could apply bondo to give it a fillet-brazed look

vee_dub

thanksss

bikejack

Yeh fill it and sand it smooth, anything else is asking for trouble.

Nessism

Edit: this post references dressing the welds on a steel frame. When I posted this I didn't realize we are talking about an aluminum frame. Considering the heat treatment present on many aluminum frames I don't think it's a good idea to go grinding on the welds. Fill them and sand is as far as I'd go.

As long are you are not digging down into the weld and removing structural material you can do weld clean-up using a file. My first custom frame was from a guy that used a combination of MIG and TIG depending on the joint. He used quite a bit of filler on his joints which made them lumpy. I used a small triangle file to smooth the lumps down on the welds and the frame came out great. Key here is to make sure to NOT take metal off the tubes (undercutting) and again, don't dig down and take tons of metal out of the welds so as to affect the structural strength of the weld. For remaining low spots in the welds you can fill them with a little JB Weld or Bondo.

Good luck.

vee_dub

thanks for the advice guys..
yer i am going to fill it up and sand it smooth....filler primer then paint..

I realised there are few scratchs here and there on the carbon rear stay... Looks like its clearcoat cause onlyt he shine is off..just wondering is it possible to sand it down abit then respray with clear coat?

Cheer,
DUb.

PS: Sorry for asking so many questions.....just want to build a nice frame. My first attempt.

seeker333

won't the bondo crack around the bb-seat tube area?

NoReg

I use 5 minute epoxy and microballons if any further thickness is required. I have some welds that have been out of doors for years and there isn't any sign of cracking even with our winter cold and hot summers.

seeker333

I'm unfamiliar with microballoons - I'll have to investigate sometime when opportunity arises. Thanks for the tip.

Dr.Deltron

Start by cleaning with PPG DX330 wax & grease remover.
Then spray epoxy primer.

NOW you can use hi-build primer or Bondo.

Sand with 220 grit and then 320 for smoothness. Re-clean.

Final complete coat of epoxy. Do not wait too long before spraying color, as you will have to scuff the whole thing before proceeding.

Color at will!

Clear the whole thing*, carbon stays and all!

*For the carbon stays, scuff the carbon lightly (it has clear over the carbon already)with FINE Scotchbrite pads and clean with DX330 prior to clearing.

Should be good to go!

vulcan

be careful of bondo, it has talc in it. (like baby powder, read "absorb moisture")

When painting cars we stay well away from name brand bondo.

I think one name is snow white body filler, I don't think it has talc in it.

NoReg

Microballons are micro glass/phenolic ballons that look like a powder, and can be added to epoxy, etc..., to create syntactice foam. All that means it that you end up with a product like the epoxy used here, that also has lots of little (too small to see) bubbles in it, and is therefore lighter than epoxy, easier to sand, bulked up, etc... Often you have to add small amounts of thickener to the epoxy also, but that seems to be unecesarry with 5 mins, since they are already pretty thick. Any boatshop supply should sell you some balloons, and you will need so little they might just scoop you a sample.

cs1

Seems like a lot of work to smooth a joint. How does Cannondale get their beautiful joints? Being a large manufacturer, they can't spend as much time as we're talking about in a production situation. Yet their joints look like they were fillet brazed. I can't see mass produced frames being fillet brazed. It's way too costly.

Tim

Nessism

Cannondale sands there welds to smooth them out - must like steel frameuilders when they fillet braze. Lots of hand labor.

DannoXYZ 

The thing with the Cannondale frames is that they're welded up with extra material with the grinding & smoothing in mind. You can't take a frame that has minimalist welds and start grinding away, you'll leave too little material in the weld itself. Also polishing and smoothing out the surface after grinding/smooth is imperative in order to not cause stress-risers that can result in premature failure.

potus

cannondale uses a two pass weld. the second pass smooths out the weld, you can read about it here:

https://toolingandproduction.com/arch...602welding.asp