Have you ever been driving in the car and made a turn.....

.....with all the windows closed and helium party balloon floating on a string. Turn to the left and the balloon will lean INTO the corner. The static air inside the cabin has inertia so it piles up very slightly to the right of the cabin giving a differential air pressure which the balloon feels.

I saw this from the Space Needle.

Looks like maybe where a contest should be in Howard’s backyard.

Before you get any of these make sure you have 4-40 taps, both left and right.  They come untapped and the rubber is very hard, much harder that a DuBro.  They will not self thread using a bolt.  The hole is deep so you can tap it a full 1/2".  Once tapped, links are very easy to turn with just enough hold to keep them from rotating on their own.  I tested one with only 4 turns in the threads and it held for as hard as I could pull on the pushrod.  In my bag of 10, all 10 of the balls were tight and very free.  In my last bag of DuBro about 1/2 were too tight to use.

Ken

Just curious, does anybody make a 3.75-40 tap just for ball links?

     Take a 4-40 bolt and using the thinnest cut off wheel you have, cut a flute the length of the threads. Two or three is our call. Taper the end a tiny bit and you have a tap that will work in wood, plastic and and can chase existing threads in anything. I have never tried cutting new threads in aluminum or brass. It may make the threads in the ball link body a bit more snug. Threads on things like push rod ends, wheel spokes and such are not cut with a die. They are rolled in a series of sharp wheels and that is what raises the threads above the diameter of the rod they are made in. I wish I had a dollar for every time some one came into the hobby shop I used to work at and asked for a die to make threads on push rod ends longer!! I know a guy that had a small machine for rolling threads and I'm trying to see if he'll part with it just because it's the only one I've ever seen!!
  Type at you later,
   Dan McEntee

Another good approach for children's trainers is dispense with threaded fasteners and use rubber bands.  Put dowels in place of the bolts and provide an anchor rod behind the engine mount.

A broken gum band can cut your losses.

From the looks of the glow plug fins it worked. 

From Tom Dixon        Re: “Joe Nall”

The Joe Nall gathering/contest is coming up shortly.  I plan to be there late Thurs. morning, May 16th through late Fri. pm May 17th.

I will have several planes for sale, with, or without engines, and also a bunch of recently “rescued” engines, all in excellent condition.

If you are interested in acquiring any of these, please call.  It’s too much to list here.

Tom Dixon
770-592-3279
315 Santa Anita Ave.
Woodstock, Ga 30189