Push rod rivet indexing method

[jim_geo]

This post highlights my low tech answer to evenly spaced rivets around the circumference of our control push rods. Most of us don't have a machine shop readily available to us. If you do have a machine shop available this post may make you laugh. I don't have the tools to generate the needed indexing and had to find a way to quickly and accurately mark the proper spacing for the rivets on the push rods used on the ailerons and elevators. Although close counts I wanted this part to look as good as possible. The method I used is a draftsman's way of bisecting a line. In the first picture you can see the simple tools I used.



Start by cutting a length of tape. Masking tape would work I chose transparent scotch tape. It should be long enough to go once around and then a little more.



Mark where the end of the tape over laps itself and then remove the tape from the tube. Apply the tape on the edge of a work surface you can mark on with pencil. With a razor and straight edge cut the tape at the mark. The tape will now be equal in length to the circumference of the tube.



Extend a line up from the ends of the tape. One line for some projects may need to be fairly long as you will see. Also draw a straight line along the top of the tape and and even better a short distance beyond the two vertical lines. Remove the tape and discard it. You'll be trading it for a fresh piece.



Next comes dividing. We need eight rivet locations for the tube being shown. Aileron push rods only need six but the method is similar. The two vertical lines marked on our work surface represent rivet number one. Lay the corner of an inch rule at the apex of the horizontal and vertical lines to the right side of our project. Left side if you're left handed.



With the scale angled across the work surface find the eight inch mark and line it up on the opposite vertical line. You will need to mark a total of seven more rivets (remember both tape ends are rivet number 1). Mark off at each inch with a very sharp pencil 1 through 7



With a square, extend those lines across the horizontal. Then apply a piece of transparent tape evenly above but touching and along the horizontal line. Trim the tape ends using your square and razor at the vertical lines. With a fine point Sharpy or equivalent transfer the marks to the tape.



Take the tape off being careful not to stretch it (not a serious concern but pulling on it isn't good). Apply the tape to the tube.



This is the tube finished. The dotted line was added by me after the tape was applied in order to more clearly show the tape ends at the rivet number one location. This method gets the job done pretty well and takes only a few minutes to set up. Drilling is done right through the tape.

[captain_john]

Nice work, Jim!

I did the same job last weekend!

Wicked Stick loaned me a paper sleeve he made that essentially does the same thing only it is reusable.

Save these plans. You will need them again on the elevator pushrod too!

CJ

[Spike]

Pretty Slick !!

[cjensen]

jim, it's so nice to have thinkers around here! i would've stared at that for hours, tried something stupid, and screw it up! now, i won't have to!!

[papakeith]

Nice job. A quick question though. Why did you need to mark out the spacing on a diagonal?

[Spike]

I believe he did it that way because its an easy way to do the math. By using the ruler at an angle, he could use any arbitrary set of markers on the ruler to get an equal distribution. Otherwise he would have to measure the length of tape, divide by 8, and then carefully read and re-read the ruller to mark them properly. This way is easier and faster.

My question though is how you are going to handle the spacing offsets in the other plane?Just use a "V" wedge, a drill press, and a bit of hand/eye coordination?

-- John

[papakeith]

Well that makes perfect sense. Thanks

[jim_geo]

Well Spike, That tube is 1 ½” diameter. It's the large diameter elevator tube. I could have used a V block and that would have worked fine. In this case I didn't because I couldn't find the one I made. So I used a tall fence on the drill press, In this case anything over an inch is tall enough, and spaced the fence carefully ¾” away from the center line of my drill (half diameter). Then to the fence clamped another block of wood as a stop ¼” away from the center line of my drill. I simply roll the tube into position, line up the mark with the bit and drill my holes. Drilling the conical ends is done with the same fence but with the end stop removed. Carefully position the cone in the tube. Line up and drill the first hole then cleco and move on to the next. You can go all the way around using only two or three clecos and leap frogging them. You're also right about the reason to use well known and easy to read rule divisions. It would be a real bear to have to add 19/64” over and over. A lot of error gets built into that system no matter how careful you are. On the other hand the operator can use any divisions they like. It's also handy to work out perspective. But that's another web site.

[jim_geo]