There are many variables that could be causing it (Jody mentioned spring geometry). My months of trial and error (and finally success) is one of the many variables you can consider.
I have the Scott 3200 tailwheel. I had a shimmy bad enough to disconnect both of the extension springs when I landed at Sun 'n Fun last year. That also ate every ounce of tread off the tire requiring a tire change during the show. Not the greatest of timing.
While at SNF I took a look at the Decathlon on display. It had a Scott 3200 as well and I quickly realized a difference - the extension springs were direct connect between the rudder horn and the 3200 on the Decathlon. Basically no additional links. As a result, the springs were under some preload on the Decathlon removing any slop.
I purchased new springs and eliminated any additional links that I previously had and the shimmy was gone. It was more of a challenge to get the springs on without the links, but it did resolve the shimmy in my case. Pics below. Just one more variable to consider. Good luck!
My old setup after landing at SNF (notice the tread is gone!). Also notice I had a link between the 3200 attach point and the spring:
The Decathlon setup (notice no links attached to the spring):
There is a partial answer on our FAQ page, https://www.americanchampionaircraft.com/faqs. The first step is looking at the geometry but the dynamics of the entire system play a role as well. We are are eager to approve the Supercubs North T3 system - there are still some design adjustments being made to adapt the T3 to the Citabria, Decathlon and Scout.
Hi Jody: Looks like a little bit of positive casting my help. Thanks for your feedback.
Yep, what Jody said.
I also installed all new leaf springs (3)
Compared them to my old ones and they were ⅝" different in the bend.
The new ones raised the tail just a bit to create the perfect geometry in the above post.
Shimmy gone!
There are many variables that could be causing it (Jody mentioned spring geometry). My months of trial and error (and finally success) is one of the many variables you can consider.
I have the Scott 3200 tailwheel. I had a shimmy bad enough to disconnect both of the extension springs when I landed at Sun 'n Fun last year. That also ate every ounce of tread off the tire requiring a tire change during the show. Not the greatest of timing.
While at SNF I took a look at the Decathlon on display. It had a Scott 3200 as well and I quickly realized a difference - the extension springs were direct connect between the rudder horn and the 3200 on the Decathlon. Basically no additional links. As a result, the springs were under some preload on the Decathlon removing any slop.
I purchased new springs and eliminated any additional links that I previously had and the shimmy was gone. It was more of a challenge to get the springs on without the links, but it did resolve the shimmy in my case. Pics below. Just one more variable to consider. Good luck!
My old setup after landing at SNF (notice the tread is gone!). Also notice I had a link between the 3200 attach point and the spring:
The Decathlon setup (notice no links attached to the spring):
There is a partial answer on our FAQ page, https://www.americanchampionaircraft.com/faqs. The first step is looking at the geometry but the dynamics of the entire system play a role as well. We are are eager to approve the Supercubs North T3 system - there are still some design adjustments being made to adapt the T3 to the Citabria, Decathlon and Scout.