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I watched over the shoulders of the mechanical engineers at FLIR back at the turn of this century. At that point, AutoCad (I think that's what they were using) had a finite element analysis that couldn't quite accurately predict the frequencies of resonance of a structure, but they'd get them...

@BaronJ : You're assuming I'll make the big flat first, and then machine the rest. I'll think about whether that's the right approach. I had been thinking that I'd machine the little flat first, then the cone, then I'd glue the thing into a fixture with conical holes in it and finish off the...

LibreCAD is a fork of QCAD that was undertaken when the QCAD folks abandoned their open-source branch. It's what I use on my Linux machine for 2D drafting. I find it adequate, but it could have more features. I use FreeCAD also, but I find it's a steep learning curve -- it seems to be a...

FWIW, the included angle doesn't have to be exact -- 20 - 25 degrees is fine. I'm not a machinist, I have no pride to uphold in that regard. I just need surfaces that are flat and polished, and a conical section that fits a conical hole.

Here's an idea of what I'm making. Half inch diameter, 104 degree included angle on the conical part. Our optics guy has repeated to me enough times that a 40 degree included angle is insane, and I finally heard him -- so that'll change. But this should give an idea of the workholding...

Oh, thank you. I was not looking forward to the necessary web searching to find a document like that.

I should have done my web search first -- isopropyl alcohol removes hot glue. I'm still concerned about the strength of the bond, but -- hmm.

How strong is the bond? Could I glue them in and then run a milling cutter across the top? I assume "meths" means methanol -- that should be compatible with polycarbonate.

It was our optics guy who came up with the name. Don't ask me. Drawing to follow.

Not a model engine question, but for work: I need to make some little (about 1/2 inch in diameter) "chicklet" prisms that fit into cone-shaped holes, don't stick out much, and have nice flat, sloped faces on the outside. I'm planning on machining a sloped flat on the end of a rod, then cutting...

Mechanical governors can be more complicated than they appear. But the ones in hit & miss engines are pretty simple in operation, getting you down pretty much to the mathematical complexity of the thermostat in a stove. I love that article, BTW. I want busts of Newton, Maxwell and Einstein in...

Just like building a physical model of a generator (see how I'm trying to pull the thread back on track?) You need to decide which parts you want to model accurately and which parts you don't care about, which parts will just naturally work and which parts you need to have to change because...

The big thing about any kind of simulation is that you have to either know what the simulator is doing under the hood, or have a good idea of what you should see. Because sometimes they go crazy. Just trusting the simulator sometimes gets you garbage. (And I've used FEMM -- it does its job...

The mounting features of the block are finished. If I got my math right, then that screw in that hole, tightened on the post that holds everything together, should clear the 3/16" shaft by 0.01". If not -- there's cutting tools. The hole was cut by first using last month's setup to drill a...

@trlvn : I've always wondered why the "fancier" steels had the rep for not taking as keen an edge. Now I know!

"Are you a regular C/L flyer? Any preferences?" I fly stunt in the US Pacific Northwest. I'm not sure if you're familiar with the AMA events, but I fly in Expert. I have been placing in the middle of the pack, but I'm currently working at a startup, and haven't practiced in a good long while.

If you're a courageous teacher, on the first few flights put the handle in your student's hand, then grab that assembly with your hand and fly the plane through your student's hand. When you feel they've got the hang of it, let go, lie down, and watch how they do. If your hands aren't big...

I second the recommendation that you get help learning to fly. Much as it pains me -- if you don't already have experience with engine handling, you should learn to fly on a plane with a factory engine. The pool of people willing to help you with engine problems will shrink dramatically if you...

Could you make a small-bore pressure gauge that just directly screws into your spark plug hole? Or cheat: hie thee to the nearest auto store, buy an el-cheapo tire gauge and replace the business end with something that screws into your favorite size spark plug hole. I'm not sure of the...

Hey Brian: I'm not sure if this is useful, or if there's a way to make a formal test out of this, but with a model airplane engine I rotate the prop through a compression stroke and feel how long it holds compression. It's all touchy-feely, but it's worked well for me. I'm just going to tell...