Rod End Bearings

[Luked 71]

I'm working on my control system, and trying to find the rod end bearings I need. I found this picture in one of Doug's for sale posts. The parts I'm interested in are the ones that are circled and labeled "see SB #6".

I'm not sure where to get Hiem FRE-48 or FRE-49 bearings or even how to find the specs on them. I'll probably end up using Aurora bearings, but I wanted to know what Avid and Kitfox used just for comparison. I just don't know how to find any info on these. Anyone know another part number for them?

 

Thanks,

Luke D.

[EDMO 1078]

Luke,

     I would have to go measure mine, but I think they are both 3/16 rod ends - 49 male and 48 female - don't remember the thread size, but think  3/16, (10-32) by looking at bolt and nut sizes on drawing.

EdMO

Edited 17 Jul 2015 by Ed In Missouri

[Luked 71]

Hi Ed,

 

Thanks for your help. I should have explained my question better. You are right that they are 3/16" bore, and shank. I'd like to know the Hiem part number to look up though because those two rod ends (male and female) need to have a certain amount of misalignment angle capability because of the way the control column rotates.

[EDMO 1078]

I cant help you with the Heim numbers - IMO, get as much play as you can.

Ed

[Luked 71]

Well, I went ahead and ordered a bearing from Spruce to try out. It's the Aurora GMM-3M-470. It's their "General Aviation Precision" bearing. Has 3/16" bore, and 1/4-28 shank. The key is that it has 17 degrees of misalignment motion. If I have one of these on each end of a pushrod, I get a total of 34 degrees in rotation. I plan to set my stops at 30 degrees total rotation. I just got one to check it out. I'll eventuatlly need 4 total. I'll let you know how it works.

 

Oh, I forgot that I was going to put a link to their catalog:

 

http://www.aurorabearing.com/pdf/aircraft.pdf

Edited 17 Jul 2015 by Luked

[Dusty 126]

Does your project have a"rotator"where it couples to the bellcrank ,this should negate the miss alignment issues?

[IFMT 36]

Make sure the jam nuts are put on the right way (flat side to the jam) and are tight to prevent the thread from becoming the rotation point. When I first got my Avid this was all  funky. Also make sure you have full stick travel left to right. The tie rods can easily catch in the control column tube if not fit just so. Cheers.

[Luked 71]

Does your project have a"rotator"where it couples to the bellcrank ,this should negate the miss alignment issues?

 

Good catch Dusty. I know what you are talking about. I am actually designing my own control system, so it's a different situation. I had the stock system though (sold it to another builder), and remember that the bearings they used had a lot of misalignment motion.

 

IFMT, thanks for the heads up on the jam nut. This will be important with the setup I'm planning because if the jam nuts get loose, it could rotate and wear on the treads like you say.

[dholly 718]

Pretty sure I have this info at home. Look at the pull sheets I posted in the Avid+ forum, they may have a better description.

[Luked 71]

Thanks Doug. I took a look. Unfortunately the pull sheets just have the Avid part number, but not much description otherwise. Looks like Avid called them F-38 and F-39. It does show that they are 3/16" x 3/16".

 

I think the point Dusty made about the swivel at the bellcrank may mean that the parts the factory used won't be what I'm looking for anyway. I think the parts I had just happened to provide extra motion. I think I'm on my own.

[tcj 150]

I can't follow what you mean by "misalignment angle capability because of the way the control column rotates".

 

The male and female rod ends that are screwed together and connect the aileron bell crank to the control stick  have a narrow shoulder around the ball so they can rotate with up and down elevator input.

 

Here's a couple photos showing them.  There was a guy posted on the old Kitfox list forum about rebuilding a kitfox.  He installed the wrong rod ends here...ones with the wide shoulder that are ment to just push/pull not rotate too.  The connection broke on about his second or third test flight.  he was able to land using just rudder and elevator inputs.

Edited 18 Jul 2015 by tcj

[IFMT 36]

Looks like there are different bell crank systems out there. Mine has a swivel right at the bell crank. My picture is poor but maybe you can see it.

[EDMO 1078]

The aileron bellcrank on my KF1 & 2 was made different than either one posted - don't have a photo right now - The one tcj posted looks like a stronger part.

When my KF2 was in an engine-out hard landing, the rod end like IFMT shows broke at the threaded end which goes thru the bellcrank - that is only a 3/16 shank.  Mine were square tubing, and made like tcj posted, but with the shank going thru the bellcrank like IFMT posted.

EdMO

Edited 18 Jul 2015 by Ed In Missouri

[Luked 71]

Hi tcj, your pictures are exactly what I remember seeing somewhere. A lot of what I've seen look more like the picture IFMT posted with a swivel or rotator at the bellcrank. If you have that, it doesn't make as much difference what rod ends you have. I'm curious what kind of rod ends are in your picture, and where you get them (manufacturer and part number).

 

On most of the spec sheets for rod ends that I was looking at, they have an angle specified that they refer to as the misalignment angle. It's basically the angle that the ball can rotate inside the housing. That was the best I could think of the describe what I was meaning, but it's exactly what you described. The bearings I'm thinking of have a narrowing housing so the ball can rotate farther.

[tcj 150]

The rod ends in my pictures do not have any markings on them.  The Kitfox part numbers are 93001 for the male and 93002 for the female.  Kit plane manufacturers keep those outsourced part numbers pretty close to the chest.

The measurements are:

Overall Length of the female 1.75 in.  (1 and 3/4)

Diameter of Head .75 in. (3/4)

Thickness of Head housing at the outer edge .125 in. (1/8)

Ball hole .1875 (3/16)

 

The third rod end in my pictures...on the rod in the control column that connects the sticks together is Kitfox part number 93003 (FRE-48).  That FRE-48 matches the female rod end number you have circled in your first post.

The measurements of it are:

Overall length1.375 in (1 and 3/8)

Diameter of Head  .625 in. (5/8)

Thickness of Head .25 in. (1/4)

Ball hole .1875 in. (3/16)

 

In the Aircraft Spruce catalog there tables with measurements for the various rod ends.  Realizing my measurements are crude and they may be off by a few thousandths but I can't find any close to my measurements.  They all seem to be larger.

[Luked 71]

tcj, thanks for taking the time to do the measurements. After a little bit of looking, I think I have found a very close Aurora bearing. The male would be the CM-3, and the female would be the CW-3. The "mis-alignment angle" on these is 20 degrees. Thanks again.

[Dusty 126]

Kf 3&4 are similar to the last photo,I would want to be sure there is no rotational strain on the other type.

No ailerons=bad day!

[Luked 71]

Just a followup to this thread. I ordered the Aurora GMM-3M-470 General Aviation - Precision bearing. Here is a picture:

 

 

I took the picture on a printed protractor. The specs say it can go to 17 degress, but I would say it looks like it can actually go to about 20 degrees. That's about where the small "shoulder" on the ball hits the outer race. Definitely safe if all you need is 17 degrees.

 

I tried ordering the CM-3, but neither Spruce or Wick's had it. It looks like you can get it on Amazon of all places (seller looks like Aurora), but I didn't really think I needed to order one since I'll probably be using the style in the picture. It does look like the CM-3 has quite a bit less material surrounding the ball. It seems to allow more freedom of movement though.