Matco Tailwheel setup properly

[Jerrytex]

So I hate to start another thread on this subject but I am battling a severe shimmy issue and I looking to see how others have successfully made the matco TW work properly.

I have the 8" single arm Pneumatic TW.

Basically I had a moderate shimmy after about 10-15 landings. The TW was slightly used when I installed it on my build, but in great shape. I went ahead and disassembled, cleaned and set the pre load. Did a few landings with no issues then I had a severe shimmy as if the TW was free castering, or the entire tail fell off the plane...... at that moment I felt that either was possible.

I contacted Matco and verified that the geometry was correct, and I was advised to tighten and preload the springs. I had run the springs a little looser on my previous plane with no issues and I set up my new plane the same way. Well after tightening and setting up as per Matco, that caused a whole new can of worms. Now the TW wouldn't break loose at full rudder deflection, and I noticed that the springs really pull hard on the rudder horns. I bought the 25 degree wings and installed them. After adjusting the wings (grinding) I got the TW set to where it breaks loose at full rudder defection, and both sides break with about the same amount of force.

So....on a saw horse, at full deflection of the rudder, there is slight resistance needed to break the TW into free caster. Maybe 3-5 pounds of force. On the ground, when I push the plane sideways, it is very easy to break the TW free into free caster. In addition, I can pull the plane by the prop and get the TW to break free just by pulling on one blade and pushing the other.


It seems to me like it's a bit too easy to break free? According Matco the spring preload increases the force needed to break the TW free, but I really don't like how hard it pulls on the rudder horns if I go any tighter.

I have a brand new 3 leaf spring from kitfox installed.
The geometry is correct according to Matco and from what I see.
I replaced the tire (haven't tried it with the new tire yet)
Also replaced both sealed bearings in the TW. (one had a rough spot)

I am curious to know if others have had similar issues?

Curious if this is similar to how others have theirs set up?


Thanks in advance.

[avidflyer]

I think a big cause of shimmy is the vertical axis it not correct. Meaning the spring is straightened out, either under load or permanently. I would try the new three leaf spring and see how it does. I have the same tailwheel on my Avid MK IV and my Kitfox 4, and it works great on both of them. JImChuk

[efwd]

I admit, I replaced my tailwheel at 25hr when I nearly ground looped. Used the entire width of a 70ft wide runway. First found the Right side, then the Left before I was able to stop it. It was all my fault for rigging the Matco as you would the Scott. Loose springs. The Breakaway force you describe that you currently have is very much the way my current TW works.
It was recommended, by several, to get the compression type springs instead of those sent with the kit which are the tension type. I have no idea how that would impact a shimmy, it probably doesn't but some much wiser folks suggested it.

[Jerrytex]

Thanks Jim and Eddie.

I do have the new spring installed and we have double checked the geometry and it's correct.

Matco feels like the shimmy was caused by the "loose" chains, so now that I have them tighter, I am hoping that it will solve the shimmy.


My main concern now is the rigging. Sure would be nice if the flash videos that Matco has worked.....

Eddie, did you have to go to the 25 degree wings? I found that I could make the 45 degree wings work with looser chains, but with the chains tight, there is no way. It would have to bend something before it would go into free castering.

[efwd]

No. Recall, I have an AB (Scott) tailwheel now and that has slack. I had never made the Matco tight as its design requires. At the time, I had every intention of going the route I have now anyhow (T3 with the AB tailwheel) so I jumped off the Matco immediately and ordered my new setup that day after nearly groundlooping. I only discovered that I had set them up wrong when I went to Airventure and spoke with the Matco folks there two months later.