Hairline stress crack in alloy tank

Previously david_veevers wrote:

Hi,

On Sat I changed gave the bike a bit of a service, oil, plugs, carb clean, while doing so I noticed the fuel line was looking a bit worse for wear so replaced it. Once all backtogether I noticed a fuel leak, I tracked it down to the tank itself

Can anyone in the SW recommend anyone to repair a hairline fracture in my alloy fuel tank?Failing that, has anyone used the brazing rods you can get on ebay, HTS 2000 or Durafix I think, would they do the job?Cheers,Dave

Yes Dave mate you need some plastic padding Liquid Metal this will do the job , this resistant too oil and petrol, and will not crack or shrink , it will take heat up to 300 f so give some a try out and stop that leak, yours anna j

Previously david_veevers wrote:

Hi,

On Sat I changed gave the bike a bit of a service, oil, plugs, carb clean, while doing so I noticed the fuel line was looking a bit worse for wear so replaced it. Once all backtogether I noticed a fuel leak, I tracked it down to the tank itself

Can anyone in the SW recommend anyone to repair a hairline fracture in my alloy fuel tank?Failing that, has anyone used the brazing rods you can get on ebay, HTS 2000 or Durafix I think, would they do the job?Cheers,Dave

That weld right next to your finger is a heli-arc weld (or TIG). It is the way alloy parts are put together. Note that the fracture occured at the transition from thick to thin metal. That is typical. It would look ok if the weld were extended to include the crack. Of course you have to mount the tank to avoid any vibration at the mounts to avoid this happening in the future. I prefer a good weld to a patch but it is a lot more expensive.

There are many welders in the services section if you choose to do that. Unfortunately you have to click on every single name to find out what region they are in.

Be sure to practice on something unimportant and, above all, don't blow yourself up.

With the repair by welding of any crack, it is important to drill a small hole at each end to stop further crack propogation due to stress concentration.

David. I see you are in the SW. Is Cornwall too SW for you? Weldspray Engineering, near Liskeard, can weld absolutely anything. They have done several ali welding jobs for me over the years, with no problems. Their number is 01579 342299.

BTW, a method of clearing petrol fumes to make it safe for welding is to put a tube over another vehicle's exhaust, place the other end of the tube in the empty tank, fire up the engine and run it for a few minutes. It is then safe to weld. It is a trick I learned in race paddocks, when a repair is needed to be carried out quickly. Usual disclaimers apply......

Cheers. Ian

It is indeed possible to purge the inside of the tank with argon but that is very expensive. Exhaust fumes are free. Argon is used for purging bicycle frames and stainless tubing for perfect welds inside and out.

Specialist Welding

Tel: 01235 820821 - Mereditch Barn Hanney Rd, Steventon, Abingdon, Oxfordshire, OX13 6AW. Worth a call, not far from Swindon,Repaired a damaged Dommie 99 crankcase for me for very little money and did a brilliant job.

Previously charles_bovington wrote:

With the repair by welding of any crack, it is important to drill a small hole at each end to stop further crack propogation due to stress concentration.

Not so as the act of welding will fuse the aluminium and remove the stress concentration. It would be necessary if epoxy was used.

BTW it is misleading to introduce the term "brazing" into the discussion. One cannot braze aluminium.

Previously david_veevers wrote:

Sorry, but why can't you braze aluminium?

By definition brazing is the act of joining 2 pieces of metal together with a melted filler material. Soldering is very similar but the filler metal is at a lower temperature.

Welding is the act of fusing together metals by melting the metal and a filler material.

You just need to find the right filler metal that will stick to the aluminium.

I withdraw my comment. I learnt that brazing was a lower temperature process using a spelter filler. Having just had a look at the interweb I can see that contemporary usage is much the same as you describe above. Although I am not sure that the distinction you make between welding and brazing is observed.