Cessna 172 - How to replace steering rods?

[German guy]

Our new to us 172G suffers from quite severe shimmy, with worn bushings in the torque link identified as the main cause. I therefore ordered a torque link kit, a shimmy damper kit and new rod ends from McFarlane. Additionally, I also ordered new steering rods, also from McFarlane, to get the entire system in a like new condition.

So, tonight I spend quite some with an A&P trying to figure out how to remove the steering rods, however without success. We removed the cover underneath the pedals, gained visual access to the bolt and the nut which attaches the steering rod to the linkage, the space is however too tight to turn the nut.

Is there a trick? Can access be gained by removing the rubber boots?

 

[Dan Thomas]

Our new to us 172G suffers from quite severe shimmy, with worn bushings in the torque link identified as the main cause. I therefore ordered a torque link kit, a shimmy damper kit and new rod ends from McFarlane. Additionally, I also ordered new steering rods, also from McFarlane, to get the entire system in a like new condition.

So, tonight I spend quite some with an A&P trying to figure out how to remove the steering rods, however without success. We removed the cover underneath the pedals, gained visual access to the bolt and the nut which attaches the steering rod to the linkage, the space is however too tight to turn the nut.

Is there a trick? Can access be gained by removing the rubber boots?

The boots might be shot anyway. And there should be an access hole in the belly under the control column that gives some access. None of the stuff up front in there is easy to get at.

The biggest cause of nosewheel shimmy is a dynamically imbalanced nosewheel. If any get balanced, it's always a static balance, which does not address dynamic imbalance. When you buy new tires for your car, the tire shop does a dynamic balance; they stopped doing static balances 40 years ago but aircraft shops still think the static balance is fine. I have stopped shimmy numerous times by dynamically balancing that wheel, and once converted an old balancer to fit the aircraft wheels, but am in another shop now and back to doing it by hand, which takes some doing.

There's another thread from about three months ago on this issue. It's worth reading.

Dan

 

[German guy]

Hello Dan,

Thank you for your response.
I'll look into the dynamic balancing of the wheels.

I removed the cover of the access hole, still no access to the steering rods, though.

The rubber boot were apparently recently replaced, I would therefore rather drill out the rivets, which hold them, only if I know that this allows me to replace the steering rods.

 

[Tom-D]

The rubber boot were apparently recently replaced, I would therefore rather drill out the rivets, which hold them, only if I know that this allows me to replace the steering rods.

Removing the boots won't get you in.

make a special wrench.

wait until you try to put it back

 

[German guy]

Removing the boots won't get you in.

make a special wrench.

wait until you try to put it back

I was afraid that this will be the case. I'll ask McFarlane if they are willing to take the steering rods back.

 

[Tom-D]

I was afraid that this will be the case. I'll ask McFarlane if they are willing to take the steering rods back.

Be patient, you can do this. But it is very seldom the rods need replacement. and they never are the cause of a nose wheel shimmy.

 

[Tom-D]

When you believe you need a tire balance try this, raise the tire wheel off the ground and spin it up with a hand drill and a wire brush.

If it shakes, you should get it balanced.

 

[Silvaire]

The steering rods are not a source of shimmy and do not prevent shimmy so honestly you may as well return them. Wheel imbalance is usually the initial culprit but not long after signs of shimmy begin you end up with worn torque link bushings and shims. Also the hole in the lug that the dampener rod end bolt goes through as well as the dampener body mounting lug get worn out. These are more difficult to address as there are no bushings in those mounting lugs.

 

[German guy]

I sent an e-mail to McFarlane earlier today, asking whether I could return the steering rod. I just wanted to have them replaced, because I thought it would be a good idea to overhaul the entire steering system. I now however think that it is probably not worth the pain.

Tomorrow, I will (hoping the machine shop managed to replace the torque link's bushing by then) put everything back together and do some taxiing.

Even if the shimmy is gone, I will also try the wire brush trick to figure out whether dynamic balancing will be needed.

 

[OkieAviator]

A few months ago we rebuilt the dampener, used the McFarlane scissor bushing kit and put on some new boots. Didn't touch the control rods and it all turned out fine.

 

[German guy]

Today, I picked up the scissors with the new bushings from the machine stop, installed them, overhauled the shimmy damper and replaced the rod ends.
Afterwards, I did some taxiing around our airfield, at different speeds, and also tried to provoke shimmy - nothing, zero, nada!


I hope that our A&P will sign off my work on Monday, so that we can get her back in the air.

Next, I'll try the wired brush test on the front wheel and also use the opportunity of the front wheel being off the ground to check / correct oil level in the front strut.

We also want to get the prop dynamically balanced, I feel that it vibrates a bit too much. I will have to look into the headset jacks, as I often can't hear the co-pilot and as there is also quite some noise. Right now, I am thinking about replacing the old headphone jacks and to install a nice PS engineering audiopaneld instead of the old KMA24 and the Sigtronics intercom.

Regards,

Oliver

 

[iflyvfr]

Today, I picked up the scissors with the new bushings from the machine stop, installed them, overhauled the shimmy damper and replaced the rod ends.
Afterwards, I did some taxiing around our airfield, at different speeds, and also tried to provoke shimmy - nothing, zero, nada!


I hope that our A&P will sign off my work on Monday, so that we can get her back in the air.

Next, I'll try the wired brush test on the front wheel and also use the opportunity of the front wheel being off the ground to check / correct oil level in the front strut.

We also want to get the prop dynamically balanced, I feel that it vibrates a bit too much. I will have to look into the headset jacks, as I often can't hear the co-pilot and as there is also quite some noise. Right now, I am thinking about replacing the old headphone jacks and to install a nice PS engineering audiopaneld instead of the old KMA24 and the Sigtronics intercom.

Regards,

Oliver

Aaah, the joys of new airplane ownership, and the expense! Good luck Oliver!

 

[German guy]

Aaah, the joys of new airplane ownership, and the expense! Good luck Oliver!

Thank you.
So far, it actually hasn't started too bad. I just shouldn't have ordered the steering rods. If I am lucky, McFarlane takes them back, even though we already opened the plastic bags in which they came in.

Technically, the radio / intercom issues and the vibration from the prop are the only things which have yet to be fixed. Neither of them is however urgent.

Other than that, we want to work on the cosmetics, as the paint, particularly on the horizontal surfaces, has become dull. Martina yesterday began to polish the cowling. Even though she just polished it by hand, using Meguiar's Ultimate Compound, she was able to completely remove the chalky surface of the paint.

The picture doesn't the improvement full justice - the strip in the center of the cowling shows the original condition of the paint, the parts left and right of it what it looked like after some polishing:

I believe that with the electric polisher we will be able to restore the the paint back to a very good condition.

 

[Dan Thomas]

A few months ago we rebuilt the dampener, used the McFarlane scissor bushing kit and put on some new boots. Didn't touch the control rods and it all turned out fine.

Yeah, but. If that nosewheel is still dynamically imbalanced, the new hardware will be shot after a while. Replacing that stuff takes out only a part of the play in the system. There are wear points that cost a lot to fix, like the nosewheel fork and steering collar, whose little holes for the torque link bolts get wallowed out due to shimmy forces. Mechanics often don't tighten those bolts properly to pinch the spacer bushings so that they don't move, and the fork and collar lugs get worn holes and little depressions worn into them on the inside where the spacers chafe against them. Only fix is new, expensive parts, that then get worn again with an imbalanced nosewheel.

The problem is the lack of a balancing machine built for small wheels. Dynamic balancing machines aren't cheap, and the low production volumes of an aircraft balancing machine would make them even more expensive.

See this thread: http://www.pilotsofamerica.com/forum/showthread.php?t=80029

Dan