Tail wheel shimmy

[68niou1]

Ok guys- need some help here. There has been a a few landings now where it feels like I have a flat tire, just recently I figured out it was my tail wheel. I have a Matco single arm with the new KitFox triple spring and it only seems to happen on pavement. Is there something I should check on my tail wheel? The tire is a little worn- would that cause it? Any suggestions would be appreciated. I do prefer wheel landings vs. three point- maybe I'm doing something different:D

Thanks,

Scott

[GMKman]

Not sure if this the problem you're having but when I owned a Glastar tail dragger, the tail wheel would shimmy when the springs started to "sag" hence changing the caster angle of the swivel bearing. A wedge shim or re-arching the spring would fix it. That's assuming the bolts are tight and the bearings are not bad.
I hope that helps.
Brad.

[dynomike]

I battled a shimmy for a hundred hours in my avid ,I took only a quarter turn on the big nut to preload the joint .cant feel the pressure difference in the rudder pedals but no shimmy in three hundred more hours.

[PapuaPilot]

There has been a lot of discussion on this forum about tailwheel shimmy. If you search this you will find lots of ideas that will help you.

[Jono]

Lots of good stuff can be found on this forum.
My understanding is shimmy is usually
1. Angle wrong (sometimes because leaf springs have sagged
2. Lose chains

Could the leaf spring be sagging changing the angle slightly and also loosening the chains?

Jono

[jiott]

I had the shimmy problem, most likely due to sagging of the 3-leaf spring from rough dirt on/off airport strips. Tried tightening the big tailwheel nut and then the springs-helped a little but no real solution. Was going to have the leaf spring angle reset by a spring shop, but decided it would just happen again for the same reasons. I bit the bullet and installed the Grove solid aluminum spring and no shimmy ever since.

[68niou1]

There has been a lot of discussion on this forum about tailwheel shimmy. If you search this you will find lots of ideas that will help you.

I always look first. 4 threads specific to tail wheel shimmy is not a lot- and every one said re arch the spring(mine have less than 50 hours on them)

I have tightened the mount bolt, but I don't run my chains tight. The weird thing is it does not happen every time- that's why I was asking flying style?

Thanks,

Scott

[herman pahls]

What do you suspect was the solution?
The rigidity or the angle of the tail wheel, or both when you went with the Grove tail spring?

[PapuaPilot]

I upgraded to the Grove single leaf and have not had a shimmy since. My shimmy happened when I was doing my gross weight/aft CG Phase 1 testing. The problem was the angle due to the heavier tail. I have not had a problem since.

FYI when I experience the shimmy I learned to unload the tail by pushing forward on the stick or by doing wheel landings and holding the tail off as long as possible. Mine didn't do it every time either, it showed up when the chains were loose, aft CG and especially doing 3 point landings that were a little hard.

[jiott]

My experience was somewhat similar to Phil's. I have the ABW tailwheel which is quite heavy. I really don't know for sure, but I suspect the success of the Grove is both things: stiffer so it doesn't sag so much, especially over time, and the angle is somewhat better.

[Dick B in KY]

Had the same problem with my SS7. Tightened up the main pivot nuts on the tailwheel, problem solved. Be sure to grease the pivot bolt grease fitting also.

Dick B

[Wheels]

I had shimmy on my maul tailwheel, but when I went to the pneumatic wheel the shimmy went away. Also had a shimmy when I had a heavy cargo bag on the J-3. Lighter load, less shimmy.

[68niou1]

Update- tightened the nut a quarter turn, regreased the bearing and problem solved. Hopefully this helps someone else in the future. Thanks again for all the help!

Scott

[JohnB]

Hey, can we get an update from those that have switched to the grove aluminum tailwheel spring since it's been a year since these posts.
Are you still happy and the shimmy monster is still at bay?

After over 2 years with the 3 leaf spring, I just had my first experience with a severe shimmy and I didn't like it much. Thanks to the posts on this forum, I checked the pivot angle and sure enough I have negative caster when loaded down. Looks like the grove spring may be the answer.

[PapuaPilot]

I have not had any shimmy problems since upgrading to the Grove aluminum spring. That was about 75 hours ago when I installed it.

[jiott]

I am also happy with the Grove spring; it took care of my shimmy problems. It also helps to check and maybe tighten that nut once in a while.

I started with the 3 leaf spring and it was fine for about 2 years; then shimmy started showing up and seemed to get worse and worse. As John said, the caster angle had slowly changed, probably from a few hard landings/rough runways over the years. The Grove spring seems to hold its shape better. I think the factory should change the 3 leaf spring to give it 5-10 degrees more bend in order to allow for some settling especially with heavy loads over time. In my opinion, the Grove spring could also use about 5 degrees more bend. The way they are now is just too close to the proper caster angle. I know of no downside to a little more than enough caster angle.

[JohnB]

Thanks for the updates.
Looks like I'll be giving Kitfox a call today and lightening the old wallet.

I operate off of a grass strip so the old tail spring has gotten a good workout and has apparently decided to relax a bit.

Thanks for the suggestion Jim. I snugged up the steering chains yesterday and will snug up the pivot nut today. Maybe that will get me through until the new spring gets here.