How to fix a cracked bike frame: welding aluminum

[@davidtomlinson5017]

I have worked around welders for years, so I automatically turned my head to avoid looking at the arc in your video!

[@CoolBikeProjects]

😉, good thing the iphone footage clips at a certain brightness or we’d both be in trouble.

[@Gallardo6669]

@@CoolBikeProjects arc light on an LCD is simply white light, nothing more. Not brighter as the sun light standing right in front of the actual welding action

[@xd1be9nb7v]

yo, are you serious? you're now viewing it from an lcd screen...😅

[@MxCraven]

I definitely think we should be welding our frames back together more often. Quality aluminium welders are hard to find, but for steel bikes there's a lot of people out there who can do the work. It's much better to repair than to throw away, and you come away with a story to tell.

[@CoolBikeProjects]

Agreed! I totally get the need of manufacturers to want frames returned for warranty work, but most of the time we were instructed at the shop to destroy them or throw them away.

[@MxCraven]

@@CoolBikeProjects Yeah, it sucks that parts just get destroyed. Carbon is especially bad for this, as it's just plastic really, and incredibly difficult to find a place that can repair it unless you know an F1 team or something

[@chrisallen9154]

Quality welders are not that difficult to find. Too many people are unwilling to pay appropriately for the work that is requested. My tig welder does not get turned on until my hourly rate is discussed and minimum is one hour. Many people do not understand that preparation is part of the job and I do my own preparation. Not comfortable having people tell me they have done the preparation.

[@rosomak8244]

Yes. In esp. we should weld where there is an obvious design mistake like in this case.

[@thefranconian6087]

Very curious to see how this works out. I found a thrown away GT Tempest and after breaking it down and cleaning the frame, I found a stress fracture in the front headset tube from the top going down about an inch and a half long. The frame is hanging in my garage as I wasn’t sure if worth having a professional try to re-weld, figured that’s a high stress area. Thanks for posting this, can’t wait to see more.

[@MrStingraybernard]

I’ve Tig welded for 29 years and also mountain bike ,the location of that crack and nice fix shouldn’t be a problem riding that bike ,like he said it’s not a high stress location on that frame

[@CoolBikeProjects]

Thanks Ron!

[@nickmassey9104]

One thing I learnt early on with alloy welding .clean clean .deep filling area to sink the weld into . I've seen similar cracks 9n cheap frames with long posts fitted when the bikes landed on the seat and it's bent the seat tube .Great skilled welder . to repair alloy frames cos how many times have we heard" its broken its scrap "👍

[@CoolBikeProjects]

Great point!

[@miguelelasmar]

It also looks kinda cool as the welder left it.

[@velowelder6333]

Nice job, I’ve been doing this for over 25 years it’s always more fun fixing frames than making new production frames. 6061 alloy is more forgiving than the 7005 alloy especially Easton 7005 “varilite” tube sets were notorious for cracking in non welded areas.

[@rolobotoman]

Do you think broken aluminum drop outs could be saved without heat treatment? Somone has a real nice bike with such a break near me. I could do the welds nonprovlem, but I'm not sure it would just not rip off at the haz after jumping a sidewalk.

[@velowelder6333]

@@rolobotoman yes you can, just let it rest for at least 30 days, at least that’s what I do at work and nothing comes back.

[@rolobotoman]

​@@velowelder6333 For real?! never eared of letting alu welds rest.. but I only built heavier duty stuff. poor man's heat treatment I guess. I'm really tempted to try! The place it's broken is solid (not hollow), and I think I could beef it up with more material. Thanks! getting advices from people who actually do the thing vs forum nay sayer is invaluable.

[@velowelder6333]

@@rolobotoman we used to heat treat repairs but would get warping problems from previous heat treatment “memory” my college instructor and metallurgist is the one who suggested the 30 day annealing time and it has worked for us for over 15 years. I’m not an expert but this is what has worked for me and my company. Btw. I work on 7005 series aluminum using 5356 alloy if that helps. Good luck to you.

[@dahemingway76]

Where are you guys based? I have a Mountain Cycle San Andreas with a crack on the main frame around the swing arm pivot weld and running up the side of the monocoque, told its 6061 Solution tempered. Trying to work out best bet at a weld repair, any ideas?

[@johnnydoe66]

I am a bit skeptical about repairing an aluminum frame due to how metals can become fatigued, especially where this cracked. A chromoly or steel frame would be a better option for welding in my opinion. In aircraft maintenance, we stop drill cracks with a 1/4" minimum drill, anything larger typically would require an Engineering authorization. I have had three frames crack, all aluminum, along welds.

[@CoolBikeProjects]

Great insight John. The welder commented how thin the metal was, but felt confident the crack would not spread. It should be a good experiment!

[@johnnydoe66]

@@CoolBikeProjects Hope it works out, but I would keep an eye on the top tube and seat tube junction, and maybe the downtube near the head tube.

[@mazdarx7887]

Yea, there is a lot of ideas and opinions like that going around to the point it's gospel. I'll take a pro welders word over internet opinions any day. A lot of "cyclists" and "bike mechanics" think they are dealing with cutting edge technology, but they don't realize there is not much out the simpler than a bike , well, maybe a hammer

[@daddyshrek2295]

technically you can repair it but it needs to be heat treated afterwards, which costs a lot as you need an industrial grade oven

[@CoolBikeProjects]

I am learning more and more about the process. As I understand it, the strength loss from welding can come down to a number of factors including the filler material used, the type of tubing (6061) and how quickly the welds cooled. I'll be talking with the welder soon to get more info on it. Thanks for your insight as this is all new to me.

[@daddyshrek2295]

@@CoolBikeProjects i'm glad you're doing these experiments though, perhaps one day there will be some breakthrough that makes aluminum frame repair more accessible to the average biker so that people can have the same ease of mind with alu frames as they do with steel frames

[@danchambers1350]

@@daddyshrek2295 7005 frame material get close to this. 5356 filler and will naturally age back close to original strength after 2-3 weeks at room temperature. Artificial ageing in an oven is more consistent, but not absolutely necessary (6h at 90° C, then 4h at 150° C). Sadly, this was a 6061 frame, so now 50+% weaker in the repaired area than it was before the failure. This could have been addressed with some reinforcement and a relocation of the dropper hole to the neutral axis of the tube.

[@ScrubsIsee]

@@danchambers1350I had also opted for a relocation of the hole and mayba adding an inforcement sheet / aluminium part. There was a reason the fram cracked at that spot. Anyway I like the repair effort, as it shows that you can save a cracked aluminium frame.

[@brianpham2584]

Wow, IR enabled routing and boost is pretty modern these days. I wonder if quality control is also a part of it outside of user error.

[@CoolBikeProjects]

The shop I picked it up from are pretty sure the guy rode the bike pretty hard. I don’t think it was a quality control issue but who knows?

[@3clubforever]

That’s pretty common for frames to crack on the seat tube when there is a cut out. I would definitely close the entire hole. So much downward force on the cranks pulling on that tube

[@shanefuller8907]

Great to see a fix. We throw away far too many things, if it get's another few years then great.. Just need to look at some poorer country's to see that everything can be given another chance at life.

[@miltonbeasley6575]

Welding .... it's like sewing with 🔥 FIRE 🔥 😃

[@Gallardo6669]

Welding light on an LCD display is just white, not brighter as the sun as being at the spot. Alu without heat treatment of whole piece always carries possible surprises for future

[@BoonMountainBike]

That's pretty cool. Brought back memory when I broke my BMX bike and they welded it together with a square metal. Looks so ugly. My dad was like "it's fixed"🤣🤣

[@CoolBikeProjects]

Awesome!

[@miltonbeasley6575]

Good of your dad to try and help .. even if It was a little ugly

[@CoolBikeProjects]

You’re not ugly Milton 😂

[@simonm1447]

I once (as a teenager) welded V brake sockets (by myself with a simple stick welder) on an old steel road bike. The brakes were excellent afterwards, unfortunately the fork was weakened after the welding, and broke at 30 km/h +. I flew 5 meters through the air, but wasn't hurt, the bike almost hit me then because it was also flying through the air. Since then I avoided any welding on bike frames ;-)

[@markusilomaki8922]

From the bottle cage mount bolts it looks like the seat tube is also slightly bent. Should be ok for moderate trailriding though after the fix 👍🏻

[@CoolBikeProjects]

Yes the bend is actually designed that way on many modern hard tails in order to accommodate a larger wheel. It allows for a shorter wheelbase while getting the seat angle correct.

[@markusilomaki8922]

@@CoolBikeProjects You are right 👍🏻 it is in the original design as well, so all should be well, no geometry changes. Fracture not in a location that would cause catastrofic failure if it refractured so thats a good thing. As it is a burly frame it should come out as a good bike for trail riding! I would ride it 😀

[@CoolBikeProjects]

Thanks Markus!

[@alanhowson2270]

How did this work out?

[@christiantabangay3202]

man I really need a ting welding my self I have this project bike and the joints at the seat post part have holes in them caused by rust found a real aluminum old bike that I wanted to build my self this is good video 🚲👌💪🇵🇭👍❤️

[@BradleyJohnston_Realtor]

I’d love to get my old Gary Fisher Rig frame up and running again. It has a crack in the seat tube just above top tube junction near weld. Anyone you can recommend? I am in Central Texas

[@CoolBikeProjects]

Sorry no connections down in Texas

[@BradleyJohnston_Realtor]

@@CoolBikeProjects I found someone, thank you.

[@TeeLichtet]

Doesn't aluminium need to be heat treated after welding?

[@daddyshrek2295]

yeah, that would be the proper procedure but it's really costly

[@danchambers1350]

6061 requires a multi-stage cycle to restore strength: 30 minutes at 530C. Quench in water or water/glycol. Align within max of 8 hours. Artificial age 8 hours at 175C.) 7005 will naturally age at room temperature close to original temper in 2-3 weeks, but an artificial ageing is preferred for a more consistent result (6h at 90° C, then 4h at 150° C). Sadly this was a 6061 frame...

[@kevinharrison5620]

LOL, you people really believe bike manufacturers do this with their frames? Keep dreaming.

[@snoopy10411]

How much does that cost to sand blast and rewelded and painted by a professional vs buying a new frame?

[@CoolBikeProjects]

I only speak for this project really. I paid the welder $50 for prep and reweld. If I do a single pass powder coat it’s about $100-$125 for the frame to be sandblasted and powder coated.

[@dustinbird2090]

@@CoolBikeProjects I saw others here in the comments and another bike frame builder channel mention heat treating after a welding. I'm not very familiar with the level of risk or cost to benefit of heat treating in this situation. Is this a consideration you guys are taking into account? Subscribed and hoping to hear an update after the frame has seen some miles put on it. 👍

[@johngonzalaw795]

Make a follow up video. I would have filled the dropper hole for redundancy

[@CoolBikeProjects]

Will do. That is part of the experiment. Thanks for watching!

[@Kinnup7]

Was that follow up video ever made? I have an interest in understanding this outcome and the long term prospects of this repair.

[@AndrewRasmussenRides]

@@CoolBikeProjects how's this 2017 Felt? frame repair experiment going? Can't find the follow-up. Failure is still worth documenting - very good for credibility too.

[@alexsheehan4617]

Really cool video! I am curious about one part - I've heard that aluminum bike frames need to be heat treated after they're welded in order to bring them to full strength. Are you planning to do that for this frame also and if not, how much weaker do you think the frame would be approximately?

[@CoolBikeProjects]

Yes in the ideal world heat treatment would be nice, but not possible for most of us. No idea on the loss in strength, but obviously a bit stronger than riding it cracked :)

[@Exstaz]

How did you do the hardening? T6 hardness are pretty common and will be gone after you weld the frame.

[@richardwales58]

I think it was caused by the haz zone making it brittle when they welded bottom bracket shell in the factory as I’ve had two frames break there

[@hellcat553]

Does tig welding safe in 7061 aluminum because i have one but tiny crack in chainstay welded part in the bottombracket area

[@paulsweeney5642]

My alu frame cracked at seat tube/head tube. I had it welded this summer and have been riding since then. Not felling so confident now having read some of of these comments.

[@CoolBikeProjects]

I hear ya, each of us need to be in charge of our own safety. if you don't feel safe riding it then please don't. My take on this video project was seeing if it was possible to salvage a frame that would have otherwise gone to the trash pile. As many others have pointed out an aluminum frame that has been compromised and then repaired should not be ridden rough. Best wished Paul!

[@berniemac8413]

@@CoolBikeProjects so how is the frame holding up? Do you have an update or a video on the situation?

[@grantchandler8294]

Aluminium frame can be welded but to get original strength they need to be heat treated again otherwise they will crack next to the weld. I certainly wouldn't weld a frame especially if the crack was in a high stress area

[@puniwhalelover]

So how's the bike doing now :) ??? I also have a cracked frame, right below the headset :/ I always wondered if that could be fixed and safe to ride..

[@CoolBikeProjects]

Been saving up for a couple parts to build this back up. I will put out an update video when it is done. Thanks!

[@BradWadeNL]

As someone who has welded before, I'm very curious of the outcome of this experiment. In order to keep your favourite frame alive, voiding the warranty is sometimes the answer. Here is a wonderful example: kzbin.info/www/bejne/fobUfqWFpNdor8k&ab_channel=Spindatt

[@bob-ny6kn]

... aaand ACTION! "How to fix a cracked frame. Take it to a professional." Fin.

[@CoolBikeProjects]

Ha ha, sometimes that is the answer although I do hope we made it informative.

[@RobertJones-ew8fz]

Is there a follow up video yet?

[@CoolBikeProjects]

No follow-up video unfortunately, the cost of getting the bottom bracket replacement hanger and other parts was prohibitive for the project. I finance the projects one bike at a time and couldn’t keep holding up funds for it.

[@JohnPilling25]

As a metallurgist - yes I have a Ph.D. in that area - who has worked in the field of mechanical behaviour of metal and particularly aluminium alloys for 40 years I would have thrown the frame into the recycle. The tubing you’re welding is heat treated and cold drawn and very thin. When you are welding it you are destroying all that processing which makes it strong. You are replacing a wrought material with a casting. The weld itself will not be thick enough especially after you grind the area down to make it smooth. Just look at the thickness of the welds holding the frame together - they are thick because they have much lower strength than the tubes and need all that thickness to carry the imposed loads. Just recycle the frame.

[@CoolBikeProjects]

Hi John, Thanks for chiming in on this. Lots of great comments from welders and metal workers. I have been saving up for some parts to rebuild this bike. As stated in the video I will not be taking this on anything serious and will not be passing this on to anyone else. I think the question of repairing bicycle frames is common because so many have seen videos on rebrazing and repairing older steel frames. Aluminum is something I wanted to dive into because repairs are almost unheard of. I'm guess I'm learning why :)

[@JohnPilling25]

@@CoolBikeProjects steel is much more versatile. Brazing is much lower temperature than welding and one is not actually melting the steel. Also brazing is carried out at the ends of the tubes which are much thicker than the middle because of the butting/profiling of the internal tube wall. The brazing temperature will soften the steel slightly but will not re-heat-treat it as welding does. Welding thin sections can also introduce horrendous residual stresses due to contraction in the weld itself as it solidifies and cools. Welds need to be stress-relieved and I don’t often see people doing that - especially on KZbin. I would be very reluctant to repair a carbon frame as well. Once the fibres have been snapped one would need an equivalent thickness of patch to allow the new fibres to bridge the gap and carry the loads. As the resins are thermosets it’s impossible to get a good chemical bond between the old and new resin - the weak link is the resin - Again, I’d just throw the carbon frame away. - I have been doing structural engineering with carbon for the last 20 years and when repaires are needed to carbon reinforced structural parts the design of the patch to bridge the load is quite complex. I know - too much materials science. In summary - you can straighten and braze, even weld steel subject to a few caveats but aluminium and definitely carbon frames should be destroyed & recycled.

[@simonm1447]

@@JohnPilling25 It seems there are carbon repair shops in UK (and probably somewhere else too), GCN made a couple of videos about them. Recently a 787 was hit by lightning and had a hole burned into the carbon fuselage, I'm curious how they repair this since they can't just replace a skin panel like on a conventional aircraft but replacing the segment would mean taking the whole fuselage apart

[@JohnPilling25]

Repair is complex - airplanes generally replace the entire panel - others use tapered repairs where the area around the hole is ground away very wide and new layers are added, each larger than the previous allowing shear to transfer the load gradually to the original laminate..the patches are cured under vacuum.

[@simonm1447]

@@JohnPilling25 the 787 has no conventional panels riveted on frames and stringers ( unlike the A 350), they use one piece barrels. The whole fuselage is just made of 4 barrels.

[@probhatshil5123]

My driver side dropouts was bennd how can I fix it

[@onelove8062]

Would you take it on a 10,000 mile tour after one such weld??? Thanks

[@CoolBikeProjects]

Yes, but I can only speak for this weld project where I saw the work being done.

[@tessar7228]

Hi, I ahve a bike I love but the frame needs ammending to make it a stepthough. I need a professional so I dont lose structural integrety. Can you help?

[@CoolBikeProjects]

Sorry Tessa, I took this to a professional welder, and as described in the video, this is purely an experiment. I would suggest you contact someone locally to see if it’s even a viable option for your frame situation.

[@fr0xk]

The bike "FELT" it

[@keichannnn]

reinforce with smaller tube inside

[@pinatabloom]

Hey sorry if this has been covered, but ive read a lot that after welding alu it has to be heat treated? Just got a nice frame with a little crack in it.. id like to keep it though it seems like a headache, id be stoked to bring it back to life! My friend is a welder, i can ask him to use this method.. but how do we heat treat it/strengthen it once drilled/cleaned/welded? Liked one post in the comments about a bike that was so broken but they kept bringing it back! Cheers

[@CoolBikeProjects]

Hi there @pinatabloom, this ended up being a bit of controversial experiment. If you read through the comments there are number of welders and machinists that have chimed in with strong feelings and some sound advice. Most of their comments lean towards the need for heat treatment after welding, which would be nearly impossible for most people due to resources. I felt comfortable doing this as a personal project. I believe the welder did a great job with it, but It is not something I would suggest for most people unless they are wanting to experiment and are okay with the risk of having a frame collapse while riding. Not a pretty picture. I'll leave it at that. Thanks for watching!

[@pinatabloom]

Sweet as. 30 day cool off period sounds like the go!

[@denissavgir2881]

What welder machine is that?

[@CoolBikeProjects]

Not sure brand welder he was using. I had my brother film this part for me.

[@bikinglikebecker]

Shouldn't he be pumping boron gas through the frame tube he is welding?

[@danchambers1350]

Hmmm: Pretty dangerous advice and some glaring omissions here. A professional welder, certainly, and no blame on him for the work. He did what he was asked to do, and did it well, but there's more to be addressed. Full disclosure, I weld and repair aluminium bike frames for a living. -No mention of the need to post-weld solution heat treat/quench/align/age a 6061 frame. -Approx 50% drop in tensile, yield and fatigue strength in the area if not treated. Results can vary, but only in the worse direction. -No reinforcements made to address the original failure source. -A hole on the side of a seat tube is a huge stress raiser, given the side loads in that area. Should be on the front (neutral axis), if anywhere at all. -Welds finishing on the highest stress edges, should be reversed direction. Start at the edge, finish on the solid.

[@CoolBikeProjects]

Hi Dan, I appreciate the extra insight you given here. Our follow up video will address some of theses issues. Hopefully the disclaimers given throughout the video emphasized the need to have a professional involved and that this is not recommended or endorsed by frame manufacturers.

[@benscott6266]

How did I not find you earlier. I have a cracked intense uzzi. I have had it welded but now I need it heat treated. Do you know anywhere where I could get it heat treated?

[@Kinnup7]

@@CoolBikeProjectslooking forward to seeing your follow up video

[@danielakerman8241]

I would not have a ton of confidence in that. Aluminum does not react to welds and heat the way steel does. My understanding is that aluminum is weakened through this process, whereas steel is not.

[@Veganarchy-Zetetic]

Shame nearly all bikes seem to use aluminium frames now then. I can't even find an ebike with a steel frame :(

[@hinz1]

Likely twist and bending from pedaling. Bike frame has very little strength, laterally.

[@geewillikers5342]

I know a welder, but he’s not serious. Makes inappropriate jokes, etc. would he be ok for a job like this?

[@ronrambo7834]

nice quality tig job "nickels"