Bellcrank puzzle

[Mark Jackson]

I am getting ready to install the bellcranks in my RV-8 wing. I reamed out the bushings with a 1/4" drill bit. Bolts go in reasonably easily. I used a 3/8" drill bit and a tap wrench to remove some of the powder coating and stuff from the WD-421 bellcranks.

Mystery - The 3/8 inch drill bit slides through the bellcrank easily. The bushing will not go through. It will slide almost all the way through easily, but then gets stuck with about 1/4" to go. It does this from either side, in either orientation. I thought the bushing was bent but the bolt goes through true. Measured the bushing and it is .375 at either end and in the middle. I thought the bellcrank itself might be bent but the drill bit slides through easily. If the welds were intruding into the barrel, it would bind as soon as I started to put the bushing through.

I am at a loss. Any ideas out there.

I uploaded a video to YouTube of the bellcrank/bushing.

https://youtu.be/oBnGC2zptB8

[Taltruda]

I would say the welds distorted the steel, and that you should use a real reamer. Drillbits don't really cut on their sides, and they bend to follow an existing hole. Bring it to a local machinist.

[Mark Jackson]

Originally Posted by Taltruda

I would say the welds distorted the steel, and that you should use a real reamer. Drillbits don't really cut on their sides, and they bend to follow an existing hole. Bring it to a local machinist.

I also measured the drill bit, it was 0.005" undersized. I ordered real high quality reamers. Expensive

[N804RV]

My aileron bell crank bushings did the exact same thing. I wrapped some 400 grit sandpaper around the bolt (no bushing) and worked it through the bell crank and tried to get it as smooth as possible. Then, I polished the bushings in my brass polisher with crushed walnut shell media. Now, they slide like butter.

Once you've got those bushings polished, protect them from any scratches or dings.

[xblueh2o]

Originally Posted by Taltruda

I would say the welds distorted the steel, and that you should use a real reamer. Drillbits don't really cut on their sides, and they bend to follow an existing hole. Bring it to a local machinist.

Had the same problem and I also assumed the welding had cause a slight distortion. Running a reamer through fixed it. Out of curiosity I did it over a white paper towel to see how much material was removed. I think there were two little flakes that fell out and a couple more that stayed in the reamer flutes. Big picture, it didn't take much to fix it. Just having the right tool.

[wirejock]

Originally Posted by N804RV

My aileron bell crank bushings did the exact same thing. I wrapped some 400 grit sandpaper around the bolt (no bushing) and worked it through the bell crank and tried to get it as smooth as possible. Then, I polished the bushings in my brass polisher with crushed walnut shell media. Now, they slide like butter.

Once you've got those bushings polished, protect them from any scratches or dings.

I did as well. Works great.

[Lars]

Adding to the chorus...

Don't forget to add a little smear of your favorite grease to the OD of the bushing. Had a bellcrank out of an RV-8 today that felt a little rough. The bellcrank was adequately reamed and the bushing was longer than the bellcrank tube (very important! Don't clamp the bellcrank between the brackets- it's supposed to rotate on the bushing, the bushing isn't supposed to rotate on the bolt- have fixed a few of those) but it was bone dry and a little corroded. Cleanup with a scotchbrite pad and a little AeroShell something or other made it smooth as butter.

[goatflieg]

Same here. Took mine to a machinist for inspection. Both the bellcranks and bushings were not straight. He touched them up, got them straight and recommended Kluber Isoflex Topas NB 52 as being the best lubricant for the application. Got a small tube from CNC Online Store. Expensive... but good stuff.

[EXflyer]

Originally Posted by Taltruda

I would say the welds distorted the steel, and that you should use a real reamer. Drillbits don't really cut on their sides, and they bend to follow an existing hole. Bring it to a local machinist.

Look at a hole drilled with a bit close its not round it is somewhat three sided that's why one should buy reamers of say 1/4/3/8 and half they are not that expensive to have around. Would think anyone building a homebuilt would own those three for sure. Saves the cost and time of going to a machine shop.

[edbooth]

Also, when reaming, pull the reamer through rather than pushing it through like a drill bit, makes a little cleaner hole...an old machinist showed me this.