Progress and Setbacks
Over the past few days, I’ve been doing quite a bit of machining and assembling. I’ve made a reasonable amount of progress, and also discovered a flaw with my parts, so I thought it was time for an update.
I’ll start with the good news first. I’ve fully finished making the flywheel, and mechanically, it performs even better than I expected. I was a little worried that the precision required to locate the standoffs so that they are exactly tangent to the steel mass ring would lead to some difficulties, but I think my machining setup was fairly solid, since everything fit together almost perfectly. I had to file the bearing holes in the Lexan plates a bit since they were a little undersized, but the bearings are nice and tight in there now. I was also initially worried about issues that may arise because my flywheel is spinning on a stationary standoff rather than an actual shaft — this is a design choice I made to save money and to make the engine simpler/easier to assemble. Luckily, the bearing and standoff fit together perfectly, and the flywheel assembly as a whole spins really smoothly now. I honestly couldn’t be happier with how the flywheel has turned out. Here’s a video of me giving it a spin:
On to the not-so-good news. The piston seal I purchased doesn’t fit properly in my piston chamber. It’s made of plastic, and it’s just slightly oversized. I noticed this earlier, but I hoped that once I had machined the piston head plates and made a solid piston head, I’d be able to force it into place. I’ve made the piston head now, and it definitely still doesn’t fit. Even if I could somehow force it in now, there would be too much friction between the chamber walls and the piston seal, so the piston head probably wouldn’t be able to move very well. I considered a few solutions — filing the piston seal down might help it fit, but that would damage its ability to seal properly. There’s also a black rubber o-ring within the piston seal, so I thought about taking it out and stretching it to use as a seal instead. However, it has a square profile, and would probably result in too much friction between the piston head and the chamber.
The best solution for this problem is to buy a new piston seal. This time, I’ve decided to get a rubber o-ring to act as the seal so that it can squeeze into the chamber, even if it is a little oversized. This new o-ring will have a round profile, so there shouldn’t be too much friction between it and the chamber walls — it’s a seal made for dynamic motion like this. I’ve ordered it already, and it should be here soon. In the meantime, I’ll continue machining and assembling the remaining parts.
Since the new piston head will be thinner than the old one, the piston cylinder’s maximum length has changed slightly. I’ve updated the Desmos graph in post 8 to reflect this.
Update: The o-ring arrived! This already looks like it should work better than the old seal.
I’ll start with the good news first. I’ve fully finished making the flywheel, and mechanically, it performs even better than I expected. I was a little worried that the precision required to locate the standoffs so that they are exactly tangent to the steel mass ring would lead to some difficulties, but I think my machining setup was fairly solid, since everything fit together almost perfectly. I had to file the bearing holes in the Lexan plates a bit since they were a little undersized, but the bearings are nice and tight in there now. I was also initially worried about issues that may arise because my flywheel is spinning on a stationary standoff rather than an actual shaft — this is a design choice I made to save money and to make the engine simpler/easier to assemble. Luckily, the bearing and standoff fit together perfectly, and the flywheel assembly as a whole spins really smoothly now. I honestly couldn’t be happier with how the flywheel has turned out. Here’s a video of me giving it a spin:
On to the not-so-good news. The piston seal I purchased doesn’t fit properly in my piston chamber. It’s made of plastic, and it’s just slightly oversized. I noticed this earlier, but I hoped that once I had machined the piston head plates and made a solid piston head, I’d be able to force it into place. I’ve made the piston head now, and it definitely still doesn’t fit. Even if I could somehow force it in now, there would be too much friction between the chamber walls and the piston seal, so the piston head probably wouldn’t be able to move very well. I considered a few solutions — filing the piston seal down might help it fit, but that would damage its ability to seal properly. There’s also a black rubber o-ring within the piston seal, so I thought about taking it out and stretching it to use as a seal instead. However, it has a square profile, and would probably result in too much friction between the piston head and the chamber.
The best solution for this problem is to buy a new piston seal. This time, I’ve decided to get a rubber o-ring to act as the seal so that it can squeeze into the chamber, even if it is a little oversized. This new o-ring will have a round profile, so there shouldn’t be too much friction between it and the chamber walls — it’s a seal made for dynamic motion like this. I’ve ordered it already, and it should be here soon. In the meantime, I’ll continue machining and assembling the remaining parts.
Since the new piston head will be thinner than the old one, the piston cylinder’s maximum length has changed slightly. I’ve updated the Desmos graph in post 8 to reflect this.
Update: The o-ring arrived! This already looks like it should work better than the old seal.