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New Shimmy Dampners

Re: New Shimmy Dampners

RNC said:
Yes.

If you are blowing out shimmy dampeners there is a reason why, that isn't the fault of the shimmy dampener ;).

If you fix all those other wear parts you'll find that shimmy dampeners last a long time.
Click to expand...

I suspect the shimmy dampener was empty before I bought it. I think we missed it completely. It will definitely be fixed along with all the other wear and tear parts. Live and learn. It's almost like you need to join this forum about a year prior to purchase, just to learn all the ins and outs and quirky things with the Commander 112. This is my first aircraft purchase and I've certainly learned alot! My wallet too ;-)
 
Re: New Shimmy Dampners

And don't forget that on the original damper there's a bushing pressed into the body that receives that close tolerance bolt that holds it in place. If the bushing itself is worn even a brand new bolt will have slop in it.

That bushing isn't in Jim's kit as it's not really a user-service item. I know that Jim will press in a new one if you ship the whole damper to him.
 
Re: New Shimmy Dampners

j5gard said:
It's almost like you need to join this forum about a year prior to purchase, just to learn all the ins and outs and quirky things with the Commander 112. This is my first aircraft purchase and I've certainly learned alot! My wallet too ;-)
Click to expand...

This is so true.
 
Re: New Shimmy Dampners

Hi All,

Another important point here is that the single shear attachment of the OEM damper causes non-recoverable wear in the attachment lug that projects from the strut collar. We can press new attachment bushings into the damper lug but we can't do anything about the collar side of that joint because of the thin wall casting.

The Aerodyme PMA Shiminator attaches to the strut collar using a double shear clevis that stops the wear to the strut collar and eliminates play from any wear that has already occurred.

Re damping quality, it's not rocket science... worn OEM dampers are often down to just a few pounds of resistance (even after fresh seals and full of fluid) whereas the new PMA dampers are typ. 15 lbs. Just unhook your damper from the torque tube and stroke it to evaluate.

Jim
 
Re: New Shimmy Dampners

Folks

This is a long Thread and I didn't re-read all of the posts, but since we are discussing shimmy, are there any advantages in using a 4 ply nose wheel tire over the more common 6 ply?

On some aircraft the type certificate calls for the 4 ply nose wheel tire. My understanding is that the more flexible side walls tend to dampen the possibility of shimmy. Does anyone have an opinion on using a 4 ply nose tire on the Commander or does a 6 ply work just as well?

Regards Clark
 
Re: New Shimmy Dampners

Did a few landings today, one gave me some pretty bad shaking. Happy to find this thread and I emailed Aerodyme about the parts I need.

If I read the forums correctly I will need this first and then rebuild the Shimmy Dampener:
http://www.aerodyme.com/Service_Kits/service_kits_10.html

I already checked:
Tire pressure, was 31 PSI
Tire balance, weight was still there
 
Re: New Shimmy Dampners

JamieK said:
Did a few landings today, one gave me some pretty bad shaking. Happy to find this thread and I emailed Aerodyme about the parts I need.

If I read the forums correctly I will need this first and then rebuild the Shimmy Dampener:
http://www.aerodyme.com/Service_Kits/service_kits_10.html

I already checked:
Tire pressure, was 31 PSI
Tire balance, weight was still there
Click to expand...


First thing to do is replace the bushings on the nose scissors.
 
Re: New Shimmy Dampners

Yes it is and properly done it will correct shimmy problems probably 8 out 10.
There are other things that can cause it but this is the most likely.
 
Re: New Shimmy Dampners

Commander91gm said:
First thing to do is replace the bushings on the nose scissors.
Click to expand...

I also try and take a bit of slack out of the scissors using the thinner washers (AN960-516'L'). Jim warned not to crank down / over tighten those scissors.
When I first acquired 4JA the scissors would 'rattle' back and forth.??
 
Re: New Shimmy Dampners

I am interested too.
 
Re: New Shimmy Dampners

I am with you also

Jean-Yves from France
 
Re: New Shimmy Dampners

I'd also be interested. Your rebuild kit has works so far, but I'd replace it.
 
Re: New Shimmy Dampners

Update - just finished my annual, installed the new Shiminator, and installed both the nose scissors service kit (SK-140) and nose torque link service kit (SK-199).

Flew the airplane and no vibration when the nose gear touches down. I can feel the wheel spinning up and a tiny burble as the nose wheel makes contact with the runway. It's definitely smoother than my old reserviced shimmy dampener but I was expecting something a bit smoother i.e. no burble at all.

The problem is I don't have a frame of reference except for comparing it to a C-172 or PA-34 nose touchdown. It feels like those do. The 757/767 nose gear can bang if you let the nose drop too fast and don't fly it down to the runway. Barring flying another Commander or having a Commander pilot fly mine - what does the nosewheel touchdown feel like? Should it be as smooth as if you had a ski out there landing on fresh powder or should there be some sensation from the friction of the runway as long as it's not a side to side wobble?

Here's a link to a YouTube video I shot yesterday. I'd like to get the jury's opinion on if that looks normal to you. Thanks!

https://www.youtube.com/watch?v=Fkp8FDM36eI
 
Re: New Shimmy Dampners

Hi John,

Should be like a ski onto snow, assuming the wheel touches down parallel to the runway, otherwise there will be a correction impulse, and maybe a noticeable chirp as I heard in your video. I would suggest checking the steering rigging. Use a grease plate under the wheel, set the rudder trim neutral by counting turns, block the PIC pedals even, and check the aiming of the wheel. Adjust as necessary and make sure the cable tensions near the torque tube are stiff and balanced as you pull with your index fingers. If they pull easily and then harder, they are too loose. Call me with your results.

Jim
 
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Re: New Shimmy Dampners

jrichards said:
Hi John,

Should be like a ski onto snow, assuming the wheel touches down parallel to the runway, otherwise there will be a correction impulse, and maybe a noticeable chirp as I heard in your video. I would suggest checking the steering rigging. Use a grease plate under the wheel, set the rudder trim neutral by counting turns, block the PIC pedals even, and check the aiming of the wheel. Adjust as necessary and make sure the cable tensions near the torque tube are stiff and balanced as you pull with your index fingers. If they pull easily and then harder, they are too loose. Call me with your results.

Jim
Click to expand...

Thanks Jim! I'll get on it when I get back from my next trip. Time to go play Santa for Big Brown for a couple weeks. Merry Christmas!
 
Re: New Shimmy Dampners

Hi Jim. I’ll have a crack at that, put me down as well.
Have to work out the freight costs to OZ though
RGS
Charlie
 
Re: New Shimmy Dampners

When it all comes together just right you will not even hardly know you touched down on the mains as our landing gear is very forgiving. With regard to the nose gear - I do not let it touch the runway until the speed is bled off and gravity is doing its thing. If done right it is very smooth and no bouncing.
 
Re: New Shimmy Dampners

This thread is another example of the value of the COG forum.
At a Commander Fly In, Robin Miley checked all the airplane that flew in and almost all had warn out bushings in the front gear and steering cables out of adjustment. Shimmy was common in the Commanders at that time. Servicing the front gear including bushings, bolts and cables adjustments have taken care of all the problems but one that I know about. The front wheel mount [yoke] was backwards and caused the shimmy on that plane.
It is an easy item to check but it can be missed.
Keep us posted about what you do to fix the problem.
 
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