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Thread: Used Rocket Giotto repair - advice

  1. #1
    Senior Member skidquinn's Avatar
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    Used Rocket Giotto repair - advice

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Ive just picked up a second hand Rocket Giotto for cheap. Seller had intermittent issues that finally hed had enough of. On initial inspection looks like a fair few of the boiler fittings have had a leak at some point. Seems strange to me that so many of these fittings will have leaked. Assuming the scale buildup is a sign of a leak, any ideas as to why so many elbow joints have given way?

    Ive attached a couple of photos.
    The culprit to me is a likely control box replacement, which Im capalble to do myself but wondering whether I should be replacing all the leaked joints as well? Im suspecting yes, although would prefer not to as Ive had issues with the elbows breaking when trying to remove them on a previous rebuild (and having to them drill them out).

    Thks
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  2. #2
    Senior Member Lyrebird's Avatar
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    I'm punting that the joints that have given way were done with teflon tape when that was not appropriate (eg parallel threaded joint). To fix the problem you will have to remove the fittings and use the sealant or washers the fittings were designed to use.

    I'd remove the boiler by detaching the second fittings as appropriate, remove the element and descale thoroughly with Lyrebird patent descaler (10 litres of water, 500 g of citric acid, 2 litres of home brand vinegar) before trying to get those fittings off.

    Another trick is to get as large a temperature difference between the fitting and boiler as you can. Use a torch to heat the boiler then put the fitting in a freezing solution (If you have access to dry ice, a bath of dry ice in metho works a treat). Unscrew the fitting before the temperatures equilibrate.

  3. #3
    Senior Member Jackster's Avatar
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    Dry ice in metho!
    Holy crap, I'm going to have to google how cold that gets...

    Also to clarify, you would need to chill the male side of the fitting, and heat the female side if doing this.
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    I've seen that in machines which receive "regular precautionary descale treatments" when they're not actually required. Boiler lives because it's thick and and pretty much everything else gets devoured by the acid mix.
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  5. #5
    Senior Member skidquinn's Avatar
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    This was actually my first thought. Particularly as the owner had said he’d had the machine serviced three times in the prior year by a mobile tech. He then proceeded to recommend not using a mobile tech....

  6. #6
    Senior Member Lyrebird's Avatar
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    Quote Originally Posted by Jackster View Post
    Dry ice in metho!
    Holy crap, I'm going to have to google how cold that gets...

    Also to clarify, you would need to chill the male side of the fitting, and heat the female side if doing this.
    1. Roughly -80.

    2. Yep.

    If Caffeinator's diagnosis is correct, which seems likely, it won't help anyway as the brass fittings will have embrittled due to dezincification.. The copper boiler survives because it doesn't have any zinc to lose.
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  7. #7
    Senior Member skidquinn's Avatar
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    Thanks mate. This is what I’m afraid of.
    I could try heating the boiler and (no dry ice unfortunately) try to cool the fittings, but may try some form of penetrant to help.
    It will do my head in if I have to drill out every broken fitting....

    Any other ideas?

  8. #8
    Senior Member Lyrebird's Avatar
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    Quote Originally Posted by skidquinn View Post
    It will do my head in if I have to drill out every broken fitting....

    Any other ideas?
    Freezer spray?

    Cut the fittings off with a hacksaw, bang an easy out into the hole to unscrew them?

    Brass cuts like butter if your tools are sharp, if you do have to drill them out maybe find a mate with a decent drill press and sharp drills the right size.
    Last edited by Lyrebird; 20th March 2019 at 07:31 PM.
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  9. #9
    Senior Member level3ninja's Avatar
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    Can you access the inside of the boiler easily (i.e. does it split in half)? Sounds like your biggest issue is the structural integrity of the elbow. If you can plug one end of it securely and then fill it with something like epoxy it should hold together a bit better to allow best case unscrewing. However this probably wouldn't work if you also wanted to heat it.

  10. #10
    Senior Member Lyrebird's Avatar
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    Interesting idea but I'm not sure it will work. Epoxy has about 1/20th the shear modulus of brass*, it also bonds to brass quite poorly.

    I use a couple of brass fittings in my bike frames, I recently had to remove one (a through axle thread). I applied mild heat to stay below the Tg of the laminating epoxy then pressed the fitting out, it came out very easily. This is despite the bonding epoxy being vastly stronger than anything you can buy at a hardware shop (Huntsman 420AB, capable of a bond strength of about 40 MPa, it's about $400 a pack) and the brass having been etched to maximise bond strength as per Huntsman's recommendations.



    * the upshot of this is that by Von Mises' equal strain criterion, the stress will be distributed to give the same level of strain. Since the epoxy strains more easily, about 95% of the stress will be taken by the brass.
    Last edited by Lyrebird; 4 Weeks Ago at 12:13 AM.
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  11. #11
    Senior Member Jackster's Avatar
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    Quote Originally Posted by Lyrebird View Post
    Freezer spray?

    Cut the fittings off with a hacksaw, bang an easy out into the hole to unscrew them?

    Brass cuts like butter if your tools are sharp, if you do have to drill them out maybe find a mate with a decent drill press and sharp drills the right size.
    Maybe if the ezyout won't get it, a adjustable reamer might be better than a drill press. The reamer should self align and stay concentric.
    Maybe a bad idea, and I can't find a reamer smaller than 6mm

  12. #12
    Senior Member skidquinn's Avatar
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    Just a quick update on this one.
    All up and running as of the weekend, and I was able to gift the functioning machine to my little brother for his 30th birthday last night. A clean up and the machine looks unbelievable. Amazing how well these things hold their gleam.

    My initial thoughts on a shotty control box was spot on once I got into it. The transformer and one of the small resistors were swollen black/brown and easily replaced with cheap parts from Element14. As for the fittings, interestingly enough none of the elbows broke but one of the copper ends from the 6mm copper pipe going from the boiler to hot water tap simply snapped off. This was a relatively easy repair with a new end having to be silver soldered on.

    There was a thick sludge (thinking sediment) in all the piping and boiler which was quite strange, but relatively easily cleaned out. I managed to get water in the element which was fixed with a dry out in the oven for a couple of hours.

    Only one thing that I didn't end up fixing and is bugging me a bit. The green light comes on quite dull when the machine is turned on cold. But then weirdly turns off once the machine heats up a bit. Thinking it could just be a faulty light but not 100% sure. Not sure if anyone else has seen this before?

    I'll get some pictures uploaded shortly



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