Saturday, February 20, 2021

A Little Shop Update

In looking back over my previous posts, I notice I never updated the stories about my little Webster Internal Combustion Engine after showing the modification I made to reduce the amount the cylinder was moving.  I concluded that story saying, "Does it work?  I don't know.  I haven't had the time to test it, yet."  In fact, it does work, as this video dated February 3rd shows.  

If you compare this to the video posted on January 19th showing the engine running for the first time, the cylinder does lots of rocking back and forth in the first video.  In this video the rocking isn't perceptible. 

Since then, I've done little with the engine and had zero success getting it to start easier and run more reliably.  The only thing I've done that had any degree of success is putting together a new way of starting the engine.  What I had been using was a compromise to get me going quickly.  One of the guys told me about his method, which involved using a body shop tool called a pin stripe eraser. These things are large rubber wheels that are literally erasers.  It works but it's very messy.  Look below the flywheel's right edge in this video, between the two clamps, and you can see a mess of yellowish powder.  That's the eraser dust. 

The way most engine builders start an engine like this is with a pair of metal parts they make.  One is made for every engine and it's left on it.   It would help me explain to put the image here first.

There are two parts.  The one on the left slides over the crankshaft and is held by a setscrew visible near the left side rim.  I've seen these called a starter spud.  It's essentially a cup; a piece of 3/4 steel bored out to 1/2" inside diameter and about 0.150" thick on the bottom.  The bottom is reamed to match the crankshaft and installed so that the crankshaft fills the reamed hole.  The piece on the right is a piece of bronze rod I bought for the engine turned down to just under 3/8" diameter on the right end.  The piece is cross drilled and reamed to a 0.125" hole for a piece of 0.125 steel rod pressed in place.  It's a tight press fit; I had to use my mill's vise to push the pin into place.

To use these, the right side (I call it the Tee) is chucked in a drill, (my line powered drills are faster than my battery powered drill) the pin fitted into the slot and the drill is run to crank the engine.  In my case, it's done from the side you're looking at, and cranked counterclockwise. 

The good news is no eraser dust messing up everything.  The bad news is I still can't get the engine to start reliably and run better. 


  1. An external starter drive, how clever! In my R/C days, we had a little hand-held electric motor with a big rubber inverted cone on the shaft. You pressed it up against the "Starting Cone" on the end of the crankshaft, and it spun the engine at well above idle speed, so they lit off pretty quickly.

    You're using what for fuel again? I think you were using "0% Nitro" model airplane fuel, but don't remember exactly.

    And thanks for the smiles today! I'm still grinning over seeing it run, and SLW thought it was a "Thumbs Up" event, too.

    1. The starting cone sounds much like the pinstripe eraser, assuming it's rubber. My battery drill runs at about 1600 RPM, while the DeWalt gets close to twice that. There have been days when I put the pinstripe eraser in the fast drill, it just started up immediately. Not lately, though.

      I'm using Coleman Premium Blend, which is still naphtha-based. Honestly, I got it because it's a quart bottle and I thought the gallon would die of old age before I used it all.

    2. OK, it's running on naphtha, and not methanol/nitro/oil.

      The starting cones were some kind of "elastomer", either natural or silicone "rubber", but it didn't have any grit in it like an eraser.

  2. Drjim, just what I thought of when reading SiG's woes. I have one of those stashed somewhere in my storages 250 miles from home.

    SiG, it still runs! That is quite an accomplishment.

  3. I spent some of the weekend in my shop also. Much less successfully though :-P. I was attempting to mill some dovetail slides for eventual CNC motion stages, but don't know entirely what I'm doing yet. Blew up the dovetail bit when it pulled into the part. 5 hours of work squaring everything up and drilling/tapping mounting holes. (waiting for new stock, a new bit.)


    1. I'm guessing this time you'll drill and tap the holes last. Just kidding. I gather you're doing this for a future CNC system, so turning the hand wheels? I've done the vast majority of my milling on CNC so I don't have much knowledge of feel of a cut before it goes Tango Uniform.

      I've never got a dovetail on the mill, so I'm not sure how you'd do it. I'd think I'd remove as much material as a I could with a square bottom end mill, then put the dovetail pretty much on the bottom of the cut and then cut in the angles one side at a time. I'd be seriously leaning on my speeds and feeds program to try and learn how deep I can cut that angle in each pass. My gut tells me every pass will be a little less material because it's loading up the cutter a bit more in every pass.

      Sneaking up on a cut might well dull the cutter more than taking the whole cut, but is it better to go dull or snap?