Tail Wheel Spring Leaf

Mike Smith · Post by **Mike Smith** » Thu Aug 07, 2003 3:52 am

Rudy,
That's what I started doing a few weeks ago. It has made a tremendous difference! I don't think I've had tailwheel shimmy/vibration since I went to wheel landings. It seems that letting the tailwheel down gently at a slower speed makes all the difference in the world. And I seldom need more than 1/2 of the runway available even at the shortest field I've landed at (2500' turf).

Mike
1950 C-170A

zero.one.victor · Post by **zero.one.victor** » Thu Aug 07, 2003 5:14 am

I generally wheel land also. But even if you three-point,if you feel a shimmy going on you can often make it quit by unloading the tailwheel a bit (forward stick),or just turn it into a wheel-landing type roll-out.

Eric

Post by **GAHorn** » Fri Aug 08, 2003 12:45 am

A correctly rigged and maintained tailwheel will not shimmy. The cables should be properly rigged, the chains should be taught, the main spring should be unmodified, the tw innards should be in good condition (including the thrust-plates), and the tw should be inflated to 34 psi.
(Forget all that stuff about bending the mainsprings, the angle of the tw-post, etc. etc. Most folks have got that issue wrong. The tailwheel post should have no negative caster at all. With everything in good condition it should have positive caster (which is what many folks incorrectly imagine causes shimmy. Then they start all those nutty home-remedies, most of which do not work, or if they actually do change the shimmy, do so because they've increased friction in the spindle due to improper loading.)
New main tw springs will place a positive caster to the tw thrust-plate turntable. Do not place "bends" into your new mainspring. Not only is that an unapproved alteration of the part, it also destroys a perfectly good part. (IMHO and in the O of the mfr.)

The following illustration has been added.

zero.one.victor · Post by **zero.one.victor** » Fri Aug 08, 2003 4:33 am

George,please define what you mean by "negative" and "positive" caster. From what I've read, the angle of the tailwheel kingpin should be raked top aft/bottom forward,if it is raked the other way then it will shimmy. Like if the tailspring is fatigued & sagging.
Yes/no?

Eric

Post by **GAHorn** » Sat Aug 09, 2003 2:58 pm

You are correct, Eric.