Posted January 14Jan 14 So, last night I was testing out a new vacuum engine design. It was an inline 2 cylinder, with 4x4 pistons and 3 stud stroke, and had a new base and supercharger design. The supercharger had only one rotor(most have two) in an effort to save more parts and to not use up all the engine's power. I was running the engine at full throttle with a tiny Shark household vacuum and was measuring the RPM's with my tachometer. It redlined at about 2350 RPM, then slowed to 1800, and slowed even more to 1000, idled a few seconds around 650, and died. I tried turning the flywheel to restart the engine but it was stuck. After taking the engine apart, I discovered one of the pistons was stuck to the cylinder wall. It took a few blows against the Lego table to separate the components. There was a gouge in the piston, and an orange smear on the cylinder wall from one of the plates which I made the piston from. I'm pretty sure the two parts were joined by a sonic weld from the engine's vibrations and some heat from friction. Well, at least the new supercharger worked. Has this happened the anyone else before? What might have caused this, and was it really a sonic weld? I'm Interested to hear your feedback! Here's a link to some pictures on Bricksafe: https://bricksafe.com/pages/LegoLord1880/vacuum-engine-sonic-weld
January 15Jan 15 Author How do I keep this from happening again? I thought using 40t gears as cranks would make them act like a counterweight.
January 15Jan 15 Author The thing is I don't want to use lubrication anymore. I've had some bad experiences with olive oil leaving a residue that would gum up my pieces. If I remember right my dad still has some silicone oil that he used to put on his guns to prevent rust. Or maybe I can devise some kind of air cooling system...
January 16Jan 16 there's a reason all high speed moving parts in this world are lubricated and also why "oil-less" compressors don't last all that long. Lubrication isn't just about making parts slide across one another easily - it's also about removing heat, to either keep the dimensions of the parts in spec or to stop the lubricant itself from disintegrating. For amusement and learning though, hit youtube for "stir friction welding" as that's effectively what you're doing to those poor cylinders.
January 16Jan 16 The best fix has been given to you. Many have reported issues with silicone oil. These are plastic pieces, not steel gun parts.
January 17Jan 17 13 hours ago, Lego Tom said: The best fix has been given to you. Many have reported issues with silicone oil. These are plastic pieces, not steel gun parts. Issues with silicone oil?
January 17Jan 17 7 hours ago, allanp said: Issues with silicone oil? https://www.eurobricks.com/forum/index.php?/forums/topic/200685-lubricating-sticky-turtable/
January 18Jan 18 On 1/16/2025 at 4:05 AM, LegoLord1880 said: The thing is I don't want to use lubrication anymore. That''s fine - just don't complain when the parts weld themselves together. The only other way to get around it is to make the parts (piston and bore) so loose that you won't have much if any compression at low speed. For what it's worth, the start of this almost exactly parallels your description in the first post of the seizing of two parts at high speed with inadequate lubrication. (gets harder to spin, slows down etc etc) This last longer because it's rolling rather than sliding like the piston in the cylinder but the concept is still the same. Edited January 18Jan 18 by bonox
January 18Jan 18 16 hours ago, Lego Tom said: https://www.eurobricks.com/forum/index.php?/forums/topic/200685-lubricating-sticky-turtable/ Ah right, thanks for that. I'll have to check the MSDS for any silicone oil I have, or have used. It's a good way of seeing what harmful ingredients it may contain. Thanks again for pointing that out.
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