Removing a crank with a destroyed thread

[Andy in Germany]

Supposed to be safer use than caustic soda.
https://www.cyclechat.net/threads/seized-seatpost-victory.228392/post-5090175

There's a few methods you could try
https://www.sheldonbrown.com/stuck-seatposts.html

I suggested the cola method in the workshop and my client's eyes lit up: "Does it go boom"?

I suspect the problem is corroded aluminium oxide because the post is alu and the frame is steel. When I try to look for caustic soda all I get is drain cleaner, although it does say that you shouldn't use it on aluminium pipes so I'm guessing that's the stuff.

 

[Andy in Germany]

I've used the pedal with a loose bolt method to free the chainset, a gear puller and as a final resort an angle grinder.
Success with all three methods, with the "trick" being knowing when it isn't going to work, stop and try another method. Only used an angle grinder a couple of times, but as with using any power tool, keeping an eye on what you're doing is important. Metal warms up during cutting, so might just free it enough to finish removal by one of the other methods.

I'm guessing cutting the crank at an angle reduces the risk to the chain sorry, frame....

 

[Andy in Germany]

Amazon has quite a selection of "three leg bearing pullers" or "three jaw gear extractors" etc.

This listing has various sizes that start at £7.55. I have no idea if any of them is suitable, but they look a bit like the one in the video

https://www.amazon.co.uk/dp/B01AGKYL30

I'll measure the crank tomorrow and look for the correct size

We've now found that the bottom bracket, a nasty plastic thing, is also rusted solid. It's not a sealed cartridge, so I'm guessing I can drill into it and break it up that way, although one of my more enthusiastic clients claims to have used a blowtorch in the past: melt both sides and hammer the axle through...

 

[classic33]

I'm guessing cutting the crank at an angle reduces the risk to the chain.

Why is the chain a problem if you're cutting the cranks.
I've put the one cut on the top, inbetween the arms, then tapped it with a hammer and chisel to finish the cut, and widen the gap to get it off the spindle.

What size angle grinder are you planning on using?

 

[classic33]

I'll measure the crank tomorrow and look for the correct size

We've now found that the bottom bracket, a nasty plastic thing, is also rusted solid. It's not a sealed cartridge, so I'm guessing I can drill into it and break it up that way, although one of my more enthusiastic clients claims to have used a blowtorch in the past: melt both sides and hammer the axle through...

Give him the job of cleaning the threads for the replacement then.

Is this the same client who wanted to know "Does it go boom"?

 

[Andy in Germany]

Why is the chain a problem if you're cutting the cranks.

Sorry, not concentrating, I meant frame.

 

[oldandslow]

Another vote for a bearing puller. The one I have came from Halfords, and can be built with two or three legs. Most cranks come off with three legs, but the odd one has chain-ring mounts or whatever in awkward places, so that you can only get two in - because of course the centre mount for two legs puts them at 180 degrees, whereas three legs are spaced at 120.

 

[Ming the Merciless]

Nuke if a bit stubborn

But make sure in Space first

 

[fossyant]

But make sure in Space first

Minor point, but valid.

 

[Cycling Badger]

When I try to look for caustic soda all I get is drain cleaner, although it does say that you shouldn't use it on aluminium pipes so I'm guessing that's the stuff.

This is what I used - available from other sellers.
B&Q Max Strength Caustic Soda Crystals

This is really not nice stuff and very much encourage anyone using it to read instructions and take safety precautions - including protective eyewear. Never pour crystals into hot water - its an exothermic reaction and can result in solution boiling and “erupting”. Hence my suggestion as a plan of last resort.

 

[C R]

This is what I used - available from other sellers.
B&Q Max Strength Caustic Soda Crystals

This is really not nice stuff and very much encourage anyone using it to read instructions and take safety precautions - including protective eyewear. Never pour crystals into hot water - its an exothermic reaction and can result in solution boiling and “erupting”. Hence my suggestion as a plan of last resort.

It is really dangerous stuff.

 

[Andy in Germany]

This is what I used - available from other sellers.
B&Q Max Strength Caustic Soda Crystals

This is really not nice stuff and very much encourage anyone using it to read instructions and take safety precautions - including protective eyewear. Never pour crystals into hot water - its an exothermic reaction and can result in solution boiling and “erupting”. Hence my suggestion as a plan of last resort.

It is really dangerous stuff.

I've found some that is sold in liquid form as drain cleaner which seems the safest option. I'll try the cheap cola first, and then get properly set up before pouring drain cleaner into the frame: It seems as @Cycling Badger said, the aluminium seat post is corroded into the steel of the frame.

I'm not worried about paint as I have to respray the entire bike anyway, and we have the necessary safety equipment at work.

I'm not in a hurry as I need to remove the BB first.

 

[Andy in Germany]

Still working backwards: does anyone have an alternative to a blowtorch to remove a cheap and nasty plastic cup-and-cone bottom bracket?attempts to remove it conventionally just broke the plastic (and yes, I was turning it the right way).

 

[Andy in Germany]

Some research has revealed that Würth make a drain cleaner which uses Potassium Hydroxide, which apparently has the same effect on aluminium, so I now have a source if/when all other alternatives fail (and I've got the BB our of the frame)