Stupid pushrods.

So I've been working on the aileron pushrods. The big ones were pretty easy, even figuring out how to get six rivets evenly spaced around the circumference (that's 19/32, by the way). But the smaller ones... Grrr.

I got the 4130 tubing cut, trimmed, cleaned up just fine. Of course the ends won't fit. OK, no problem, I chucked them in the drill and used some 150 grit to turn them down a little. I was going for a "very snug" slip fit, but as it turns out I undershot a little. They're more of a hydraulic press fit in the ends of the tubing. Of course by the time I figured that out, they were in far enough that they were not coming out for any more turning.

Since I don't have a hydraulic press, I used two blocks of wood with holes drilled to protect the threaded studs, and a 2# plastic dead blow hammer. They're in there and they're not coming out in this lifetime.

So now the ends are in and it's time to put in the rivets, which I am convinced are pretty much unnecessary. I'm using a C-frame to set them. The first time around several of the shop heads were badly clinched (tail offset to one side of the hole). I drilled them out and re-set new rivets, half of which were just as bad.

It seems to me that a -12 rivet is a little long for this job. Is it acceptable to use a -11 rivet instead? Is there some secret to getting these done right that I'm missing? This is starting to tick me off a little, and I've used my last -12 rivet.

Try using squeezers to set the rivets.

A trick to use in getting the hole spacing even

... is to wrap a strip of paper around the tube and then mark where the overlap is.

Then, using a rivet fan - the adjustable rivet spacer, if you don't have one it's really a good tool to have - use it to evenly mark the correct number of holes between the start and end, keeping in mind that the first hole is the same as the last hole when wrapped around the tube. Then put it back on the tube and mark the positions to drill. Done!

No measuring required at all.

When you get to that point ...

It is time to take a breath, remove yourself from the aggressive one track implementation mode and let you mind broaden the possibilities a little. Several times during the 8 years of building our RV-6A that saved me from brute forcing into trouble. Several times I had to carefully think out a plan for accomplishing a task with subtle difficulty that I didn't give proper credit to initially. Several times I had to make up my own tools for a one time application or modify store bought tools and very carefully implement the plan. There was always a solution and it was up to me to find it.

Rivets. When I was still working for a living I was talking with one of the mechanical engineering supervisors who had build a Jeep for his son out of aluminum. It was his own design I believe and it was powered so that his young son could drive it. In passing he made the comment "one of the best tools I ever bought was a rivet cutter from Aircraft Spruce." Until that point I was using drawing callout rivets or going up or down in size to fit the needs of the assembly. In the standard drawing notes where I first worked after getting out of the Air Force (McDonnell Aircraft - F-101B) there was an allowance for going up or down in fastener length to accommodate tolerance buildup etc. so I knew that the proper length rivet is more important than having the exact part number rivet as specified on the drawing. Before I started building the plane I went to Van's school in North Plains, OR and the instructors (familiar names like Scott McDaniel and Ken Scott) educated us on riveting: If the rivet is too long it will tend to clinch over instead of setting properly; if a rivet is bad evaluate whether it is necessary to remove it or whether the effort to achieve cosmetic perfection will put the assembly at risk for no physical benefit; if it is necessary to remove the rivet use the proper drill size to remove the manufactured head and punch to drive out the shank (all done carefully, carefully). As I proceeded through the build I did run out of proper sized rivets and I placed several orders for specific part number replacements. From the friendly ME supervisor at JPL i took i a look at the Aircraft Spruce catalog and ordered a rivet cutter and 1/4 lb of 1/32" and 1/8" diameter rivets with flat heads and round (universal) heads of sufficient length to cover any possible needed length. I got my 4 bags of rivets and never again ordered a special rivet when I did not have the proper length. You should not blindly comply with a drawing callout for fastener length when the application clearly shows it is too long or too short.

I found that when something doesn't seem right it is time to step back and give it a little thought because I'm approaching it wrong. I applied that all the way through the build and tried to achieve the highest degree of excellence that I could achieve in every task for it's significant part of the whole airplane but with intense focus on the specific task at hand. I entered the judging at Sun 'n' Fun and AirVenture in 2005 and didn't get so much as an ataboy but I just passed 1,000 flight hours in the plane last week and I know it is a good one.

Don't let it grind you down.

Bob Axsom

Check the length of exposed rivet protruding on the side opposite the head, if it is overly long, it is more likely to bend over, or "clinch". If the next size shorter is a little (emphasis on "little") short, remember that this particular rivet is loaded in shear, and there is virtually no tension on it, like there is in 99.99% or more of the other rivets in the airplane, so about all the shop head has to do is keep it from falling out. The front section of the Van's directions (Section 5, I think) tells how much each diameter rivet should protrude prior to driving, though you probably know all that given your stage of construction. Also, as mentioned above, sometimes it is easier to get a good alignment on the rivet with a squeezer than with the gun and bar. My .02 dollars worth.

Weld them...........

Weld!

I know you think they are tight enough with the press fit to stay put forever.....they are not!!! In time they will move if not rivited or welded. I prefer welding but your choice!!

JB Weld Annular Space

One of the problems with these push rods is that the middle part of the rivet is not constrained in the annular space inside the threaded end. I filled this area with JB Weld to hold the shaft of the rivet straight and once the JB Weld set, drilled the hole through now solid material. I think Tony Bingelis had a sample picture of this situation in one of his books.

mike newall said:

Weld them...........

Click to expand...

I wish I had. Too late now. Powdercoat and primer on the parts, and there is no possible way those ends are coming out. Ever.

I've got things good enough to clean it up, shoot some primer on the ends and call it good. There are rivets in place -- not all of them looking all that perfect, but serviceable and secure. I'm moving on.

Timely thread

as I was at the same point today. I read all of the related posts to that point in the day, shortened my rivets, squeezed them and they still clubbed to some degree. I sent a pic to my tech counselor and after his review, I built on. I would like to think that if I were to do it over, I would have someone Tig weld them, but I'm probably stubborn enough that I would keep squeezing them. I like the idea of using JB weld in the open space to support the rivet-maybe on my next build!

There is another thread that suggests setting them with a ball peen hammer....After clenching them with a squeezer, I used a shorter rivet the next time and tried the hammer method- not perfect but good enough.

jmbaute said:

There is another thread that suggests setting them with a ball peen hammer....After clenching them with a squeezer, I used a shorter rivet the next time and tried the hammer method- not perfect but good enough.

Click to expand...

That is the method I've used on several non-RV pushrods. The clench is just to keep the rivet from falling out of the hole. All the "problems" stated in this thread are cosmetic, not structural.

If you weld...

If you weld them be sure to protect the threads and a vent hole should be drilled. After welding the tube should be oiled inside and then the vent closed with the proper rivet.

I went with riveting over welding. I didn't want to risk the heat of the weld changing the characteristics of the metal tube/threaded end. Probably overly cautious, but the riveting went smoothly.

I measured equidistant rivet hioles by wrapping a piece of blue tape around the rod, marking where they overlap and measuring on a (horrors) metric rule in millimeters. Easy to divide by the number of holes to be drilled. IE, what's 3 1/2" divided by 6 vs 90mm divided by 6?

Calipers

I set the end of the tube(s) vertically on a piece of paper and traced the OD onto the paper. Then I took a double sharp-pointed /screw adjustable caliper and walked it around the circle. I made fine adjustments until the last point landed on the starting point with the requisite number of hole marks (i.e. 6 holes requires six walking points around the circle....When the last point matches the starting point, you have equally spaced points around the circle.) It usually only takes three or four trips around the circle until the fine adjustments make the last point land on the first point. Once the spacing is established, mark lines radially to the circle, put the tube vertically on the paper and transfer the marks to the tube. Voila, your tube is marked for equally spaced rivets. Now flip the tube over and mark the other end!

As for the rivets, I used an Avery C-frame and the second rivet set that comes with it that fits into a rivet gun. The C-frame keeps this long set exactly in alignment and allows for extra control so the set stays on the rivet. Just hold the tube tightly with your other hand so it doesn't rotate. Also, ensure the other end is supported so that the rivet is kept aligned with the set.

Well, I managed to get them done - if not completely to my satisfaction, to the point where they are serviceable and not too ugly. I'm moving on.

I don't know if JB Weld would provide any real benefit. If the rivet shank expands much when it's set, it it seems to me it would most likely just crack the epoxy. Maybe I'm wrong. Anyway, if I build another RV (ain't happening!) I'll have them welded.

After struggling with the same I reordered two more with the rod ends I had mine welded and put one rivet as a safety measure. They worked out beautiful
Smilin' Jack Hunt