Spa Cycles Tourer 540- frame alloy info for repair

[kitaan]

Hi everyone,

My stepson has been happily cycling to school for the last three years on his Spa Tourer 540. At the last service the mechanic pointed out a hairline crack where the bottom bracket meets the down tube.

I have some experience TIG welding light gauge tubing so I feel confident repairing it if it isn't an exotic/ heat treated steel.

I'm not sure what the frame alloy is as there are no labels and I haven't been able to find any information on this model online (we bought it second hand). I am assuming Chromoly 4130 but does anyone know?

I have tried calling Spa a couple of times but haven't been able to get through. Their warranty is also only valid with the original purchase documentation.

Thanks!

Felix

[rogerzilla]

540 is just the frame size in mm. The main frame is probably Reynolds 725 but the other tubes may be unbranded chromoly.

I'm not sure I'd bother welding it as it's quite likely to crack again due to the extra metal acting as a stress raiser, and the tubing was probably already overheated at that spot. If you just want to get another year out of it, maybe.

[gaz]

As rogerzilla says, Reynolds 725.

[531colin]

I think it’s the 3 main tubes which are 725.
I’m on the phone just now, there is a website called “torch and file” which is a good source of information such as what Reynolds make in the various tube sets and wall gauge etc.
The bottom bracket shell is likely to be Cromo made in the Far East, I thinnk.

Edit…. Might it be kinder to braze a repair by building up a fillet or brazing on a patch?

[kitaan]

Ah I was hoping that wasn't the case.... but credit to Spa for using good steel. Thanks everyone for the quick replies.

With the different steels of the frame and bracket shell, I'm inclined to take Colin's suggestion and TIG braze a big fillet in a few passes, minimising heat and using pulse. I have some silicon bronze TIG brazing rods to hand and will preheat a bit with a gas torch. Any other advice welcome.

You can hopefully see it here (I don't seem to be able to upload images so I have linked):

https://drive.google.com/file/d/1mMxdnK ... sp=sharing

Thanks

[rogerzilla]

That should be ok with a brass fillet. I thought it would be one of those corkscrew cracks you often see at the base of the seat tube.

[KM2]

Could it be that it falls under …..items away from home…. and therefore insured under your house insurance?

[kitaan]

That should be ok with a brass fillet. I thought it would be one of those corkscrew cracks you often see at the base of the seat tube.

Thanks. I've got silicon bronze rather than brass- any reason that won't be suitable?

[kitaan]

Could it be that it falls under …..items away from home…. and therefore insured under your house insurance?

Ha well let's see how the repair goes!

[rogerzilla]

That should be ok with a brass fillet. I thought it would be one of those corkscrew cracks you often see at the base of the seat tube.

Thanks. I've got silicon bronze rather than brass- any reason that won't be suitable?

I'm afraid I'm not a brazing expert. Silver braze aka solder is the kindest to tubing but isn't generally used for fillets.

[fastpedaller]

I'm slightly shocked as i have a Spa Tourer - have to give it a once-over, as I wouldn't have expected a crack on a Spa steel frame. Having seen the photo it appears the tube has cracked in the heat-affected zone...... is this a rare occurrence in a welded steel frame? I appreciate lugs and brazing are much less likely to lead to a problem. I understand 725 and other modern Reynolds alloys are more tolerant and can therefore be welded, which was not possible/recommended with 531.

[hamster]

I'm slightly shocked as i have a Spa Tourer - have to give it a once-over, as I wouldn't have expected a crack on a Spa steel frame. Having seen the photo it appears the tube has cracked in the heat-affected zone...... is this a rare occurrence in a welded steel frame?

Tens of millions of TIG-welded MTB frames since 1985ish show that this is very rare.

[rogerzilla]

I've seen more photos of cracked steel or Ti frames (the supposedly everlasting materials) than any other material.

Ti is especially treacherous to weld correctly, snd cheap Ti is highly likely to crack within a few years. Steel is easier to weld but you still get the odd bad frame, and thin-walled tubing is less forgiving than the gaspipe they use on Apollos or Universals. Unless you see the discolouration of the frame before it's been blasted and painted, you have no idea if it was locally overheated.

My theory is that the fatigue limit only gets you so far; an overheated joint means the metal starts off weaker, and the kind of life a bike frame leads means it gets occasional overloads that may exceed the fatigue limit locally, like hitting potholes with a heavy rider in the saddle.

[Brucey]

a fellow forum member kindly gave me his similarly broken Spa touring frame. I planned to weld repair it, but with a twist. The twist would be to excavate a hole between the BB shell and the DT using a die grinder.

I would aim to do the repair via MIG welding, using what I call the 'burst' welding strategy. This breaks up the usual HAZ microstructure, perrnitting much of the GCHAZ to be backtempered. The bottom bead of the weld should be slightly positive and free of undercuts, because this part of the weld is exclusively made via conduction limited melting. The weld top bead would be dressed via grinding in the usual way.

The hole would allow an internal reinforcing sleeve to be assembled in situ from ~3 pieces which would then be welded to one another. Finally the sleeve can be bonded into position using epoxy resin.

Hopefully the repair will be much stronger than it was originally, and the frame won't break there again.