Arc welding a bicycle frame

[Drains]

If they had MOT's for bikes...

 

[squazy84]

im guessing this is a wind up yea?if not well its your train set but i suggest you just buy a second hand bike, i dont know maybe build what you want just dont ride it lol

 

[Chickenjohn]

I used aralidite to glue together the split. I also spread some resin around the handlebars, to see if it prevents them turning. The existing bolt now provides insufficient pressure to stop rotation. Once it's set, I'll use wire and/or fibreglass to lash together the handlebars and the main part of the broken stem.

I was going to try TIG welding until someone said it's the wrong type of aluminium.

has to be a wind up, did the thread start on April 1st by any chance???

 

[shenion]

TIG weld alumininum with what welder?

 

[GeorgeB]

Here's a photo of a plate welded in pace by Raleigh or their suppliers between the rear forks on my mid-1980s donor bike. What I'm saying is that welding must be OK for this type of frame, or Raleigh would never have risked it.

 

[Chickenjohn]

Maybe you could just fibreglass the front forks as well!

 

[chunkolini]

Hmm,no contact from George, do we assume he is in bed eating through a straw?

How is it going George?

Chunko'.

 

[GeorgeB]

Hmm,no contact from George, do we assume he is in bed eating through a straw? How is it going George?

Thank you for your interest. A few days ago I posted a photo of the handlebars, joined together with fibreglass but there was virtually no interest or comment within 24 hours so I deleted the photo since it's not directly welding related. I assumed this thread had finally run its course. The handlebar repair may seem a bit odd but I'm very confident the joint will not break.

Without wanting to go as far as destructive testing, do you know of any simple tests I could run on the welded front forks, either before the forks are mounted back in the frame or after the bike is rolling again? Perhaps there aren't any, and any extra stress could just increase the risk of the forks snapping at an unexpected moment.

 

[chunkolini]

Take it out for a gentle ride and have a look, keep checking it, when you forget to check it they are probably safe. First rides on home built bikes are exciting.

Chunko'.

 

[Mike Brass]

Without wanting to go as far as destructive testing, do you know of any simple tests I could run on the welded front forks, either before the forks are mounted back in the frame or after the bike is rolling again? Perhaps there aren't any, and any extra stress could just increase the risk of the forks snapping at an unexpected moment.

You could try setting up an easy deflection test for the fork, you don’t have to over load the fork just take it to a point where you’re happy with it.

Mount the fork in a horizontal position on a good sturdy bench via the steer tube (I tend to use two pipe clamps) with the curve of the legs pointing up.

Using an old axle and 4 nuts: bolt the axle in place by sandwiching the drop outs between the nuts one either side then make sure they are as tight as you can get them.

You just need a strong rope or steel cord to make a stirrup for you foot or to hang weights off. I would expect a fork to handle 85kg at least with deflection in the legs without folding or showing any signs of cracking.

Personally I’d put the forks in the bin and find an old set of Steel hybrid forks off ebay for a tenner. I’ve worked in the cycle industry for over 10 years and seen people try what your doing. You might be lucky and it might hold, or you could be like one of my ex customers and end up under a bus, its not worth the risk.

Lets put it another way would you weld the suspension springs of your car because you wanted to make it higer….. No. Effectively that is what you are doing the fork is a flex zone of a bike its designed to have natural compliancy, so those fork legs were cold dawn over 30 years ago then heat treated to give it is natural suspension.
So Arc welding it has changed the properties at the highest point of stress on the fork. Plus you wont know if the fork has started to rust inside, or what type of life the fork/bike had in the past or if it has been crashed and you have fractures in the metal.

I don’t wont to sound like some idiot who’s posted for the first time, I came on here to looking for recommendation for Arc welders for my home projects, but what you are doing is really not worth risking your life

 

[oilcooled :)]

when u were extendiing the forks you could have cut them and used two plumbing fittings the brass ones, i had to say it, i would look funny. did u ever see this lads
http://www.scribd.com/doc/5300347/Safety-at-work-awards


very funny

 

[GeorgeB]

You could try setting up an easy deflection test for the fork, you don’t have to over load the fork just take it to a point where you’re happy with it.

Mike - thank you for a helpful post and welcome to the forum. I might try loading the forks with up to about 100Kg on a test bench, or just take it easy for several hundred miles, riding on cycle paths rather than the road, so I minimise my chance of falling under a bus.

Do your comments about natural compliancy and cold-drawing apply to bog standard mild steel forks? I hoped I'd get away with this modification if the forks are nothing fancy, whereas if they are made of high carbon steel, I gather the forks are far more likely to crack.

I don't see the risk as anywhere near the same as welding the suspension springs on a car.

 

[Mike Brass]

With regards to the forks its an If, but, or maybe, any curve steel fork has some type of natural compliancy it will act like the leave spring of a truck, and more so with older forks, because of the work load of the fork in its life time and the driffent forces it is subjected to the curved blades develope more flex.

Even being a mild steel fork the blades would have been drawn, you'll probably notice that they are tapered. Chances are the material being a cheeper theres probably no internal butting or thining of the walls so the straight gauge of the steel helped with the welding.

For me its a big risk I began brazing my own frames about a year ago, and I've had problems with my joins using quality materials, dont get me wrong i'm no master welder/fabricator, it just to big of a risk, I love building and moding retro frames. but what your trying to do I realy think your better of scouring ebay for cheap parts, rather chancing your face

 

[GeorgeB]

I've had problems with my joins using quality materials

I'm sure you're right and, therefore, I wonder what you make of my handlebar repair. The stem was cut open so I glued it back together and wrapped the area with fibreglass. I am adamant this will hold but I don't think many other people would be so optimistic. I hope to report back in two or three years and say you were all wrong regarding the various repairs to my bicycle. If anyone wants to speak out now and express confidence that none of these repairs will fail inside 3 years, please speak now.

 

[gavuk]

The life of the bike will depend greatly on how often and how hard you ride it George .......be fine if left in the shed .......as many have already said ...it may well last ,,,not many of us would take the risk though......good luck ...

 

[oilcooled :)]

hw many weekly miles will it do roughly?? will you be doing any wheelies or bunny hops or anything like that haha

 

[the snooper]

well George you can definitely say that none in the world (and be very very confident about it) has a bike like yours.
the cost of the glue and fibreglass used to fix the handlebar must have cost more then a replacement stem.

 

[Mike Brass]

Bin it........... Dont ride it. If the stem has been cut theres nothing stopping the bars from rotating in the stem, the fiber glass is just holding the bars in place.

Ok Basic handle bar physics; You'll have to excuses me I'm in "training" for my stag do on Friday so I'm a little bit blurry at the moment.

The stem and bars look like there of an Old drop bar, Drop bars place your upper body weight in front of the stem increasing the pressure excerted on the clamp creating a canti-lever effect. Those stems just about worked when you tightened that single bolt to just before the thread striped anyway.

Your handlebars take so much force when riding, under breaking the force from your upper body weight can easily double when sitting. If you stand up and pedal say up hill, the side-to-side deflection and upper body forces increase big time. Fibre glass is inherently brittle the bond will break and dump you over the bike.

 

[GeorgeB]

hw many weekly miles will it do roughly?? will you be doing any wheelies or bunny hops or anything like that haha

Good question! I reckon I'll cycle roughly 25 miles a week on average on normal roads and cycle paths. I won't be trying any cross country routes, let alone wheelies or anything,

I trust the surface area contacted by the resin will stop the handlebar rotating relative to the stem.

 

[chunkolini]

Keep us posted.
I have the straws ready for later.
Good points about the glass fibre and metal, Mike.
Stag do? good luck.

Chunko'.