Lately, it has seemed I can't get to the point of starting up my little engine, that it's one step forward, one step back and I'm redoing the same things over and over again. Last week I said "tomorrow" I'd make a replacement crankshaft throw to replace the one that has been giving me problems for weeks. The next day I thought it might make a nice accent to make it out of some brass I have, so that was a few hours. It had to be 1/4" thick to fit where it goes, and I had some junk 1/2" thick brass I've had around for years and used to make test cuts on. I thinned it down to 1/4" and was able to make a replacement fit in the space I had. Because of a few factors involved with thinning the brass and proofing the CNC file, it took two afternoons to make this one.
With that pin at the top moved over to the brass one and once in place on the engine it looks like this. (BTW, I don't know why I didn't take off that piece of tape before taking the picture, but I'm not going to bother to edit it out.).
Today, it was running again (on my Ryobi drill) for another half hour.
As you can tell, while it's moving, one can tell that there's something colored differently that's spinning, but that's about all.
What's left? I need a couple of inches of fuel line from the tank to the carburetor. I need a little mount for the fuel tank; it should be around a half inch or so higher than the carb so that the fuel flows without a fuel pump. I need to get a set of points for the engine and hook up my electronic ignition. I can get it to run with the electronic ignition spread around on the bench, but a box for it seems like a good idea. That gives some way to move it to the next model that needs one.
How do I start it? A lot of engine modelers make something to go on the shaft that my drill is driving in this video, so that they can use a mating attachment on the drill to crank over the engine. At least one modeler I've spoken to got a rubber pinstripe/decal eraser like body shops use and that created enough friction to start the engine just by holding it against the flywheel. The little oddity here is that the engine is intended to run with the flywheel turning counterclockwise viewed from the side the drill is on. That makes the drill chuck want to come loose and the same thing will happen when it's holding a starting attachment but the rubber wheel will be spinning clockwise.
With that pin at the top moved over to the brass one and once in place on the engine it looks like this. (BTW, I don't know why I didn't take off that piece of tape before taking the picture, but I'm not going to bother to edit it out.).
Today, it was running again (on my Ryobi drill) for another half hour.
As you can tell, while it's moving, one can tell that there's something colored differently that's spinning, but that's about all.
What's left? I need a couple of inches of fuel line from the tank to the carburetor. I need a little mount for the fuel tank; it should be around a half inch or so higher than the carb so that the fuel flows without a fuel pump. I need to get a set of points for the engine and hook up my electronic ignition. I can get it to run with the electronic ignition spread around on the bench, but a box for it seems like a good idea. That gives some way to move it to the next model that needs one.
How do I start it? A lot of engine modelers make something to go on the shaft that my drill is driving in this video, so that they can use a mating attachment on the drill to crank over the engine. At least one modeler I've spoken to got a rubber pinstripe/decal eraser like body shops use and that created enough friction to start the engine just by holding it against the flywheel. The little oddity here is that the engine is intended to run with the flywheel turning counterclockwise viewed from the side the drill is on. That makes the drill chuck want to come loose and the same thing will happen when it's holding a starting attachment but the rubber wheel will be spinning clockwise.
Looks like you got rid of the "wobble".
ReplyDeleteAre you running this dry, or have you put a bit of oil in the cylinder?
Are you running this dry, or have you put a bit of oil in the cylinder?
DeleteI'm running it with a drop or two of oil everywhere. The engine is actually designed with little cups in a bunch of places that are supposed to have a little oil in them. Most people just leave a hole there and put a drop or two before cranking the engine over.
Little oil cups? That's cool!
DeleteHow did you make that pie-wedge shaped CAM thing? I'm having trouble picturing a mill operation or lathe operation that would give you that.
ReplyDeleteMadRocketSci
Trying to picture how to machine that smaller radius.
DeleteThe easy way - CNC. I even had a CAM program write the file as what they call waterline cutting. It just cuts the outline in thin layers.
DeleteI made both the old and new ones that way, but had neglected to leave a comment in the file saying what cutter I used. My hangup was verifying it was what I thought.
I didn't think of trying to rewrite a code that would create the shape on my own until I was finishing up. Back when I did the exhaust cam, I wrote a post on programming that part manually. Here, if you want the geeky details.
What sort of CNC mill do you have?
DeleteAlso, what turntable do you use when cutting the gears?
MadRocketSci
I used my Grizzly G0704 that I converted to CNC as a major project before I retired. A very long explanation is in my page on the subject, but it's a 1 HP, 4-axis, milling machine.
DeleteI also have a smaller envelope Sherline milling machine that I started out with 15 years ago as a surplus "CNC Training Center" from the school district across the state in Tampa. I increased its work envelope and replaced the stepper motors and controller it had. It's also 4-axis, but 1/10 HP.
The crankshaft throw was done on the big one, but would it would fit either one.
As for the gears, these were bought from Stock Drive Products. I haven't tried to make gears, yet, but it's a just matter of time before I take that on. The big consideration there is getting the cutters since you can end up needing many of those.