Welding a steel rod in mid-air

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neb

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#228862 25-Jan-2018 23:41

I've been doing some work in Africa, and part of it involves helping fix a windmill water pump, for which the steel rod that connects the windmill to the pump has snapped. It's currently jury-rigged using a clamp to hold the two snapped parts of the rod together:

but it really needs to be welded. Problem is it's in the middle of nowhere and there's no easy way to haul a TIG welder up there, let alone power it.

Any ideas on how to deal with it? If it wasn't vertical I'd say thermite welding, but I can't imagine how you'd contain it rather than just having a melted puddle dripping down the rod...

TLD

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#1946934 26-Jan-2018 00:37

Can you sleeve it? There looks top be room for one. Replace with scaffold pole? Sleeve it with scaffold pole. Excuse the very rough sketch, but I am in the middle of swapping everything to a new computer. But if you could use an angle grinder to make a half round key-way in the sleeve and use a bit of small round bar (a bolt) as a key, or two keys would be better, four U-clamps might withstand the torque.

If you are going to weld it, then maybe stick (old fashioned arc) would be better than MIG

Many years ago I welded the two inch solid shaft from my dad's big farm roller using an AC hobby welder. I used high chrome rods after grinding a full depth V on each side. Luckily I was too young and inexperienced to know how unlikely it was to work, as it is still holding 50 years later as far as I know. I doubt I would attempt it now with the same kit. If you could sleeve it, then you could maybe bronze weld the sleeve to the shaft. I notice you mention TIG in your post. Does that mean it is stainless?

Trevor Dennis
Rapaura (near Blenheim)

neb

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#1946937 26-Jan-2018 00:47

Ooohh, interesting, thanks! I'll suggest that when I next get out there (it's a two hour drive away) and report on how it goes.

In the meantime, any other ideas are welcome, it's all number 8 fencing wire repairs so the more options there are to try, the better.

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#1946955 26-Jan-2018 07:14

Use gas rather than TIG to weld it? Maybe with extra long hoses so you don't need to haul the bottles up the windmill?

Thinking bigger picture... why did the shaft snap? If you weld it, will that weaken the shaft so that it will just snap again? Even if you reinforce the weld, will it snap again, in a less accessible place? Maybe engineer in some kind of breakable link, which can be easily reset/repaired (e.g.weld flanges to the two ends of the broken shaft, and bolt together with bolts a bit weaker than the shaft)?

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#1946988 26-Jan-2018 09:08

TLD:
Can you sleeve it? There looks top be room for one. Replace with scaffold pole? Sleeve it with scaffold pole. Excuse the very rough sketch, but I am in the middle of swapping everything to a new computer. But if you could use an angle grinder to make a half round key-way in the sleeve and use a bit of small round bar (a bolt) as a key, or two keys would be better, four U-clamps might withstand the torque.

I think the shaft goes up and down rather than rotating so your idea would work without the keys.

Aredwood

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#1947017 26-Jan-2018 09:52

I reckon gas weld it as well. But still difficult on a vertical shaft.

If obtaining acetylene is difficult, MAPP gas with pure oxygen is almost as hot.

Definitely consider bronze welding it as already mentioned. Especially if the steel is quite thin.

And there is always the real bush welding method, DC arc welding using car starting batteries as the power source. 4WD websites should have more information on that method.

kotuku4

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#1947037 26-Jan-2018 10:50

There are portable generator welders, petrol or diesel. The work well in remote situations. Buy or hire.

A long tube sleave with plenty of overlap. Could use very small indents/notch of the shaft and use bolts and nuts fixed on the sleeve to lock in place. And or weld the sleave to the shaft, taking care not to overheat and weaken the shaft at the welds.

TLD

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#1947153 26-Jan-2018 13:44

You are not going to do a decent job fusion welding with gas. It will definitely be better to provide some sort of overlap to the joint. Bronze welding thick walled sleeve over the butted ends of the shaft would work, but you would need to put lots of holes in the tube/scaffold bar, and fill with bronze weld. Do the top of the sleeve to the shaft first, as this will get heat into the shaft. If there is any sort of wind or air movement, screen it to stop it dragging heat away.

With the top of the sleeve to shaft welded, then work down the holes. The holes need to be a compromise in size so that they will let you get heat to the shaft without weakening the sleeve. I might even fit the sleeve and center punch the center of the hole locations. Remove the sleeve and tin the shaft. I don't know how experienced you are and don't want to teach you to suck eggs, but the secret is to not get it too hot. That will cause oxidation and the brass rod will not stick.

The main problem everyone is having is not knowing what facilities are available either on site, or to be transported there?

Mains Power?

Oxyacetylene?

Arc welder and whether MIG, stick, and how powerful?

Is there someone reliable on site to give you an accurate diameter of the shaft?

Are there workshop facilities either on site, or at the staging post?

If you are the person who they expect to make this fix, then you need information. You might be able to take components out there with you like high tensile bolts you could drill and run through sleeve and shaft. If you knew what the lifting weight of the shaft was in its upward stroke, then you could work out what hardware you'd need to do a non-welded fix. I'm thinking it would be the weight of the lower part of the mechanism, plus a few gallons of water, so maybe 25kg. A couple of good quality 8mm bolts could manage that in shear, so four high tensile bolts 8mm x 75mm (a guess from the picture). A decent cordless drill./ Spare batteries, and half a dozen good quality drill bits. Take a sleeve pre-drilled sized according to the information they will provide you with, and you are good to go.

Trevor Dennis
Rapaura (near Blenheim)

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neb

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#1947377 26-Jan-2018 22:58

frankv:
Use gas rather than TIG to weld it? Maybe with extra long hoses so you don't need to haul the bottles up the windmill?

Thinking bigger picture... why did the shaft snap? If you weld it, will that weaken the shaft so that it will just snap again? Even if you reinforce the weld, will it snap again, in a less accessible place? Maybe engineer in some kind of breakable link, which can be easily reset/repaired (e.g.weld flanges to the two ends of the broken shaft, and bolt together with bolts a bit weaker than the shaft)?

It goes up and down, so it's only vertical motion that needs to be dealt with. It's unclear why it snapped but probably because stray cattle knocked some heavy item onto the base and blocked the motion of the reciprocating pump, so it gave way at the weakest point.

I'll see if there's access to a gas welder. It's mostly a case of finding a solution that can be implemented given the available equipment, TLD's one is looking the most promising. The reason for thinking of electric was dealing with gas up a rickety tower, but long hoses as you say might do the trick.

frankv

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#1947524 27-Jan-2018 13:36

neb:
frankv:

Use gas rather than TIG to weld it? Maybe with extra long hoses so you don't need to haul the bottles up the windmill?

Thinking bigger picture... why did the shaft snap? If you weld it, will that weaken the shaft so that it will just snap again? Even if you reinforce the weld, will it snap again, in a less accessible place? Maybe engineer in some kind of breakable link, which can be easily reset/repaired (e.g.weld flanges to the two ends of the broken shaft, and bolt together with bolts a bit weaker than the shaft)?

It goes up and down, so it's only vertical motion that needs to be dealt with. It's unclear why it snapped but probably because stray cattle knocked some heavy item onto the base and blocked the motion of the reciprocating pump, so it gave way at the weakest point.

Right. But the principal still applies, otherwise your fix will only work until the next stray bullock walks into it. Perhaps, as part of the fix, transport in and install some fencing.

gzt

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#1947563 27-Jan-2018 15:22

Bullocks may enjoy scratching on that fence. That may be challenging.

tripper1000

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#1947585 27-Jan-2018 16:30

If getting heavy stuff up the tower is a problem and getting welding gear at all is a problem, could you thread the rod ends with a die and wind them into a pre-repared threaded sleeve? It's a solution that you could take out there in a shoe box.

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#1947628 27-Jan-2018 21:33

TLD:

If you knew what the lifting weight of the shaft was in its upward stroke, then you could work out what hardware you'd need to do a non-welded fix. I'm thinking it would be the weight of the lower part of the mechanism, plus a few gallons of water, so maybe 25kg. A couple of good quality 8mm bolts could manage that in shear, so four high tensile bolts 8mm x 75mm (a guess from the picture). A decent cordless drill./ Spare batteries, and half a dozen good quality drill bits. Take a sleeve pre-drilled sized according to the information they will provide you with, and you are good to go.

I think this idea may be your best bet.

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#1947629 27-Jan-2018 21:34

Is the current jerry rig not working?