Arc welding a bicycle frame

[oz.]

I suggest you wear a full face helmet. I've had stem's breaking on me where there seemed to be nothing wrong. These weren't cheap stems either. Fibreglass is not that strong. About a third of your bodyweight is transfered on to the handlebars and this increases as you get out the saddle and twist the bars. Also as you go over even the smallest of bumps the weight is increased massively for a split second.

I know it's good to have faith in your own work but there is a point where you have to step back and listen to others telling you not to do it. A face full of floor is not a happy or pretty exprerience, and can be severely worsened if you wear glasses.

 

[GeorgeB]

I've had stem's breaking on me where there seemed to be nothing wrong. These weren't cheap stems either.

I seldom associate what you pay with what you get. Many expensive cycle parts are made from aluminium or carbon fibre, they cost a fortune, and yet there seem to be more reports of components failure than with old fashioned steel frames. At least I know how carefully I lashed the stem and handlebars together, and I don't expect it to come apart in a hurry.

On the subject of my arc welding on the forks, is the effect of heat anything like the treatment given to hacksaw blades? The blades sometimes snap. Is brittleness the price paid for hardness?

 

[hotrodder]

Is brittleness the price paid for hardness?

Very generally yes

Many expensive cycle parts are made from aluminium or carbon fibre, they cost a fortune, and yet there seem to be more reports of components failure than with old fashioned steel frames.

'Light, strong, cheap. Pick any two' is a popular saying.

Factor in the trade off between strength/hardness and ductility/brittleness and it (hopefully) should be clear that lifespan is a different thing altogether i.e. These lightweight expensive components you don't understand... if all the excess material has been engineered away to make the thing as light as possible how could it possibly take the abuse that a cheap, way overbuilt, heavy steel component can. When things are engineered close to the limit something as simple as a deep scratch in the wrong place can be all that's needed to start a crack. The closer to the limit the part has been engineered the less material there will be for the crack to consume before the part breaks i.e. once damaged you have less time to find the crack before it breaks

This is why some of us will throw away a pair of bars and stem after a crash even if they 'look' OK or throw them out regardless after a few years of use. This is why i carefully polish out any nicks or gouges in cranks that have clobbered a rock on the trail. They didn't cost a lot because they'll last forever, they cost a lot because any and all excess weight has been engineered out of them making them more fragile (for want of a better word) without loss of strength

 

[the snooper]

i think ive found george it appears his handlebar repair did fail and he obviously was lying injured for some time before being found by a passer by

 

[chunkolini]

Well spotted,
I was about to revive this thread and see if George is still eating without a straw. looks as though he could do with a square meal though.

Chunko'.

 

[GeorgeB]

Well spotted

Yes, well spotted or drafted. Which was it? Either way, it made me smile.

I'm sorry but the bike hasn't hit the road yet. I need some additional parts and, in the meantime, somebody kindly gave me another bike. Now I'm in a dilemma. I'd set my heart on putting the welded bike through its paces but it seems daft to ignore a bike which is less risky.

 

[the snooper]

eveing george i spotted the picture, not my work and take you own advice dont ignore the less risky bike

glad it made you smile

 

[syborg]

judging by your comments my custom bike frame may have to be rethought,lol
i was hoping to weld loads of different bits of bike together to make a hybrid, only for cruising about the village mind. maybe not now,lol

 

[chunkolini]

syborg, have you started your own bicycle thread? if not do so now!

Bicycle threads can be so interesting. At least to sad nackers like me. A hybrid, I have made a few hybrids, well maybe mongrels, a bit inbred even.

Dont butt weld your forks, or dropouts, no glue and it might be fine. Always have one operating brake and a cameraman on hand. Oh and and idiot to test drive it, I usually fill that role.

Chunko'.

 

[GeorgeB]

Several months' ago, in view of all the sceptics and doubters, I used part of my old bike frame - the bit just under the saddle - to make a garden tool. I simply flattened out the tube and then butt (arc) welded it to a piece of mild steel plate. The hoe has been in use countless times and I often use it like a pick-axe to break up the soil. The weld shows no sign whatsoever of breaking so I suggest it bodes well for arc welding a bicycle frame.

I think the crux of the matter is that mild steel frames - nothing fancy - like I guess this frame probably is - can be welded. But 'special' higher carbon steel bicycle tubing would probably not last long if welded. If only there was a simple method to ascertain the 'weldability' of a given piece of steel, where it's not marked and is a bit of an unknown.

 

[Chickenjohn]

very good, but how does your bike perform on the road??

 

[Drains]

You'd better look at this cyborg
http://www.rat-patrol.org/RPUK/RatPatrolUK.html
Nothing to do with me, blame Chunko'

Top stuff. Makes me guffaw every time I look.

And Chunko looks so mean in that CCCP t-shirt. Wouldn't want to meet him in a pub car park when the chains come out.



And just to straighten things out George, the site is full of pictures of Chunko and his pals sitting on strangely demented constructions they have fashioned from old frames and stuff they've dragged out of skips. Some bits may even have been welded together with Wolf arc welders (even though they wouldn't admit to going so low, so it's not mentioned on the site).

All the best!

Si

 

[GeorgeB]

very good, but how does your bike perform on the road??

As I think I mentioned before, I was given another bike which was ready to use, so the project on the welded bike was put on hold. It's not yet finished and certainly hasn't been used. I hope to start using it at some point, though.

It may sound daft, but I'm so frustrated at not being able to test the forks and handlebars, that I may start by using the handlebars on the present bike, removing perfectly sound handlebars, just in order to see what happens with the ones I re-bonded back together.

 

[GeorgeB]

Some bits may even have been welded together with Wolf arc welders (even though they wouldn't admit to going so low, so it's not mentioned on the site).

Chunko - are any of those bikes welded together rather than braised? If so, why the dire warnings when I try to weld bits of my bike frame?

 

[chunkolini]

Last time I braised a bike frame the gravy was lovely.

A mix of brazing and Mig welding.
I would use Mig aboe arc welding. Mig can be turned down low and is easily controllable, arc welding is a bit violent for thin tubes. But Tallmartin uses it. Then again he is a Lgend.

Dire warnings? why/

What you were planning was well dodgy. The welds on the dropouts you were looking at were tiny welds onto areas that had already been welded on. I have made my own dropouts, pieces of 3mm plate with deep slots, welded onto tubes that had liners pushed up inside them and welded ito place at the bottoms along with caps. The load is spread arpound so many areas that it is over safe.

Or forks? I have used old fork ends pushed up inside tubes by around 3", a lap weld around the end of the outer tube and maybe a couple of small plug welds through the outer tube into the outer wall of the donor fork.

 

[chunkolini]

Ha! I just edited the post above to explain what was going on in it. and lost it.

Chunko' on Godzuki dropping into the 20 foot bomb hole, jumped out the other side, railed the berm, survived the doubles and fell of into the nettles because he was laughing too hard.
In the past we had long forks fail downhill racing, they sag because the welds are not in critical areas, ie lap welds near the crown and fork bottom but not on the bits that kill you when they fail. The failure mode is an elegant sagging motion, not Kertwang.
the fork on the tall bike is also triangulated everywhere, because the loads must be massive, a steerer stem up the bottom of the headtube, triangulates to the top and bottom of the forks and looks damn cool.

I used a decent donor frame for the front end, as this was designed by engineers for racing off road. Luckily I had access to a pile of ex race frames, this one, a Kona Cindercone had the back end trashed by an idiot jumping it.

Getting off topic.

Think can this kill me if it breaks? if it can, think of at least two ways of preventing it.
As you get better at it it becomes easier. I suppose I am licky this stuff suits me.


My first bike build. Indestructible, all triangles, ok the forks sagged after bunnyhopping and jumping. But nobody has ever crashed it.

George your mission is to build a tall bike or chopper and race it in next years Clunker Classic.

Chunko'.

 

[GeorgeB]

What you were planning was well dodgy. The welds on the dropouts you were looking at were tiny welds onto areas that had already been welded on. I have made my own dropouts, pieces of 3mm plate with deep slots, welded onto tubes that had liners pushed up inside them and welded ito place at the bottoms along with caps. The load is spread arpound so many areas that it is over safe.Or forks? I have used old fork ends pushed up inside tubes by around 3", a lap weld around the end of the outer tube and maybe a couple of small plug welds through the outer tube into the outer wall of the donor fork.

Thank you for your latest suggestions but I'm now a bit confused. I thought the warnings earlier in this thread were largely based on the brittle nature of certain bike frame steels made from high carbon steel. If we assume my frame is mild steel what's the difference between welding my forks and welding part of a car for an MOT, in terms of safety and risk of failure? I think Drains said my fork welds did not look likely to fail. I agree, of course. They are not tiny welds - they are over-size. My forks are also not likely to encounter the massive forces probably transmitted through your over-sized, very long, custom forks and other aspects of your special bikes. You've reassured me that my forks will probably be OK, subject to some simple tests like riding off plenty of kerbs before I go very far on an open road.

 

[syborg]

syborg, have you started your own bicycle thread? if not do so now!

Bicycle threads can be so interesting. At least to sad nackers like me. A hybrid, I have made a few hybrids, well maybe mongrels, a bit inbred even.

Dont butt weld your forks, or dropouts, no glue and it might be fine. Always have one operating brake and a cameraman on hand. Oh and and idiot to test drive it, I usually fill that role.

Chunko'.

oh chunko. i was then mixing up the p38 body filler to hold my yolk tube onto the main crossbar, ********!!! its gone hard now,lol

na mate, im keepin the main rear end and fron fork assy and just tweeking the main crossbar and down tube. but also gonna be doin a custom seat job and gonna be making some very shady steel gas pipe handlebars

might got for a set of them trike type chopper bars but i,ll see how fussy im feeling once i get my slitting wheels out,lol

as for the cross bar....ive found some solid 22mm rebar with the ribs, might use some of that as a novelty and i know that wont give up the ghost too quick,lol just gonna have to make sure i get some good clean strong welds on it, this frame cut pretty easy with a hack saw and it turns out its a "murray" bike, so 99.9% sure its just mild steel, the wheel mount brackets are kinda slid up the frame tubes then welded so mildsteel is me first bet.

find me tread under arc welding as ive already started chopping and get the job goin

peace

syborg

 

[GeorgeB]

I just did a bit more arc welding in connection with one of my bicycles. I decided to move from indexed shifters on the handlebars to manual shifters mounted on the frame - much simpler, with less to go wrong. The only problem is that I haven't seen any manual shifters manufactured to fit relatively large diameter aluminium frames. The manual shifters I've seen are sized to fit traditional steel frames. I decided to try and enlarge the harness by adding four new sections of steel (from an old lawnmower body). It's no thicker than car bodywork and I used the arc welder because I like the more precise control I have over the tip of the rod, compared to the large head of a MIG welder. TIG would be ideal, I guess, for quite delicate work like this. Here's a before and after photo, showing the increase in size of the harness. I'll tidy it up a bit before fitting it to my bike.

 

[chunkolini]

Looks effective.
Watch out for overtightening it and squishing the tubes, not a problem on cheapo frames, but better ones are stupid thin.
I did once help a mate to squish his stays using jubilee clips t hold a luggage rack.

Chunko'.