Bellcrank to aileron pushrods

Just a cautionary tale for all. I am sure most people wouldn't screw this up but I ended up with this...



When I stopped and reflected on my stupidity I realized when I drilled the pilot holes I should not have gone all the way through the tube. This made it near impossible to make sure that when I final drilled the tube #30 that the bit would follow the same exact path as the original pilot hole.

So my plan for my new parts is to just drill a pilot hole on one side of the tube, then insert the rod end, then final drill #30 all the way through the tube. It wouldn't sting so much but this is already my second pair of pushrods thanks to a even stupider cutting issue on the first set. This is becoming my white whale...

Jim

you're sure most wouldn't? I'm not!

turn off your butt kicking machine. As an amateur machinist with all the usual machinist tools (lathe, mill, indicat6ors, DRO, you name it) I can tell you that cross drilling a round piece exactly centered is NOT an easy thing to pull off. IF it were me I would drill the push rod and the insert all in one setup after centering the shaft in a Vblock and center drilling - and you probably don't have a Vblock or a center drill. That is the only way to keep the bit from wandering. Then after center drilling drill the whole assembly as 1 pc.

I would be curious to hear how others approach this.

Also, I can assure you that you are not the first guy to cut too much off a tube and end up with 2 pcs that are in total long enough for 1 push rod. Nobody who has survived one of these projects is laughing at you. Only the noobs and they will learn

Or you could just have them welded

That's what I did on my 9. Worked out great. Remove the powder coat a few inches and find a GOOD welder.

V block

sblack said:

you're sure most wouldn't? I'm not!

turn off your butt kicking machine. As an amateur machinist with all the usual machinist tools (lathe, mill, indicat6ors, DRO, you name it) I can tell you that cross drilling a round piece exactly centered is NOT an easy thing to pull off. IF it were me I would drill the push rod and the insert all in one setup after centering the shaft in a Vblock and center drilling - and you probably don't have a Vblock or a center drill. That is the only way to keep the bit from wandering. Then after center drilling drill the whole assembly as 1 pc.

I would be curious to hear how others approach this.

Also, I can assure you that you are not the first guy to cut too much off a tube and end up with 2 pcs that are in total long enough for 1 push rod. Nobody who has survived one of these projects is laughing at you. Only the noobs and they will learn

Click to expand...

That's how I drilled mine. Small, sharp pilot hole with a V-block and drill press.

I am also just about to get to this stage, and would like to understand the mistake. I am sure I would never make this kind of error though.

Now if you don't mind I have to get back to building my third aileron.

In this step you have to drill two holes 90 degrees apart all the way through the tube and the inserted rod end. I don't have a machinist vee block so I went and got a small piece of moulding from Home Depot. It doesn't have a vee but it has a channel that works pretty well. Van's directions are to drill #40 pilot holes for the 4 holes per tube, deburr, insert the rod end, then final drill the assembly #30. When I drilled the pilot holes I drilled all the way through the tube so I had two holes in the tube that should have been on a perfectly straight line. After deburring and inserting the rod end I match drilled #30. Problem is because the pilot hole was drilled all the way through the tube if I had twisted the tube a couple degrees (which there is no real good way to prevent this with my set up) from where it was for the pilot hole the new hole could line up on the top pilot but come out not perfectly in line with bottom pilot hole. That is what happened here. If you look closely at the picture you can see that there are actually two holes, the one on the left being far worse.

So basically the next time I go to do this I will drill the pilot holes but only through one side of the tube. I will deburr, insert the rod end, and then final drill #30 all the way through the tube and rod end.

There is no need to drill all the way through. Drill each hole individually. I have a V block but not a drill press so I did not want to risk having a hole that was not drilled straight through.

Tom023 said:

Ok, I'll admit I'm a noob and haven't reached this step yet. I've been looking at this thread for days and still cannot tell from the picture exactly what the mistake is you have made. Is it that the holes are off center? I can't tell from the picture. Please expand on the issue so those of us learning don't repeat the mistake.

Click to expand...

A smaller drill was used to make a pilot hole that was expected to lead the larger bit straight through. However, the tube was not positioned the same for the larger bit and it did not follow the pilot hole on the other side of the tube.

As I suggested below, there is no need to drill all the way through with either pilot or final size bit.

If you have a drill press I would suggest drilling all the way through with the final #30. If you don't do that then there is a pretty high chance that your two holes will not line up to run the rivet through both holes.