Just completed a tailwheel rebuild and installation of new tail leaf springs as well as steering chains and springs. Took care of tailwheel shimmy.
One problem I've still got is that I have better turning responsiveness when turning to the right. Left turning takes full rudder, is less responsive than right turning, and generally requires some brake. Turns to the right work just fine. It's got my mechanic and me stumped.
We set spring tension as shown on prior links in the TIC170A site. This seemed a bit too tight and we were concerned about unneccessary stress, so we added one more link. We've counted the number of chain links to make sure we've got the same on each side.
Could the rudder cable tension be a cause? Any other thoughts as to why turning is better to the right? (P factor can't be that much of an influence at taxi speed and if anything should cause better left turning tendency)
Kyle, you don't say which steering springs you installed. (There are some types advertised as being "tuned" to different frequencies, whatever that means.)
Try switching them from side to side and see if the problem follows. One might have greater tension than the other.
Also, you might confirm you have the same rudder deflection angle on both directions Left/Right, 16-degrees +/- 1-degree. (Check rudder rigging info in your Owner's manual.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
We installed new tension springs and sash chain from Spruce (after reading the pro/cons of the compression springs on this site).
Will also check rudder rigging. I'll have to check my owners manual - had looked in the 100 series service manual but had not checked the owners manual.
Once again I know I've seen this post subject before, but can't find it in the search feature, so I thought it would fit here. I have a broken link in one of my steering chains. Before the safety wire breaks I need to replace the chain and while looking in the Spruce catalog I saw a kit for compression type steering springs vs. the original tension springs. As is, my steering chains are tight enough that I almost strum a tune on them. They seem way too tight. What is the proper tension on these chains at rest and with the tail off the ground? Would it not be better to have the compression type springs with just a very small amount of tension on the chains in order to reduce wear and stress on the overall tailwheel system? Or does having the chains guitar-string tight help guard against wheel shimmy?
I don't think the chain tension has much if any to do with shimmy. Tight steering chains will give you real responsive tailwheel steering. I feel it will also result in increased wear of the other parts involved due to the constant pressure on them. When adjusting the chain tension,be sure to check it with the t/w both on the ground & off. I use sash chain from "Homeowners Airmotive". Cheap & readily available.
Shimmy can be caused by the t/w kingpin nut being too loose. It's up under the t/w fork above the tire. Tighten til it binds,then back off a flat. Shimmy can also be caused by incorrect caster--the kingpin should be at least vertical,preferably leaned back at the top. Don't know a better way to describe it. As an old tailspring fatigues,the tailwheel caster begins to sag to a trailing position which can cause shimmy. In that case,a new tailspring can eliminate caster-caused shimmy as well as the increasing chance of the spring breaking,causing the t/w assembly hanging from it's shiney new chains to whip the lower rudder into jelly.
As Eirc said I also use sash chain which is available locally and is the same chain you'll get in the kit. I've bought the kit. The compression springs don't seem to be the popular spring for most but some people like them. I don't use them.
Your chain should be slightly loose with weight on the wheel. The main spring pulls the wheel further away form the fuselage and tightens then in the air.
The best way to adjust them seems to be to raise the wheel off the ground letting it hang. Adjust the chain till it's snug. If you find you need a half link as I did, make the chain short and then slightly squeeze several of the links at the loop end to lengthen each one till the chain fits snug. I got this tip from someone here on the forum perhaps the old forum. It works well. A little squeezing over several links makes a big difference so don't over do it.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Squeezing the chain links is a good trick,but it's like losing your virginity--once you've squeezed them, they can't go back to how they were. So buy some extra chain. Another trick if you're having trouble getting the left & right chains tensions to match is to buy two different pitch sash chains--the same number of links will result in different lengths.
I run the compression springs on mine.They seem to be getting a bad rap from most everybody. I like them because if they aren't as likely to come unhooked from the chains if extra slack developed. Also a spring breaking would not result in loss of steering as would a tension spring.
I realize that both are remote possibilities but I like the compression springs anyway.
In another post I related how my tailwheel chain got hung up on the bolt that keeps the tail leaf springs together, causing the tailwheel to cant to the side. This caused some very interesting landings until I gave up and investigated. I figured if this could happen once then it would surely happen again, so I eliminated one link from each side. I wouldn't classify it as "guitar string tight" but they are pretty tight. As a side benefit I noticed a very positive control improvement on landing. I have not flown since then (my airplane is in the middle of a rebuild), but my mechanic replaced the rudder horn and didn't think the tension was a problem.
Just a little food for thought.
David
Although "approved" designs may sometimes inconvenience us (and our pocketbooks) when they need repairs,...making changes to the approved design isn't always as good as it may at first appear. (And it may actually end up costing far more when it fails than the original design.)
Whenever we contemplate changing an original, approved design, it's important to consider all the implications of that change. (And just because it's sold in an aviation catalog doesn't mean it's actually good for all airplanes or even good for specific airplanes. The compression-spring set-up is specifically designed for the very sturdy tailwheel steering arms of Maule airplanes, not Cessna's.)
Shimmy can occur for several reasons including loose steering chains.
The sash chain should be just-taut, and it should be adjusted taut with the tailwheel on the ground (like when you'll find tailwheel steering important) and not in the air (when it makes no difference at all.) The airplane landing gear adjustments (all 3 wheels) should be made at 2,000 lbs, with an approximately centered CG.
Both compression and tension springs will increase resistance as they are actuated throughout their design-range of motion, but compression springs, once at or near their limit of motion, very suddenly become completely rigid and will accept no more movement at all. Any further motion will result in unacceptable loads on connected equipment. It can result in damage.
Tension springs will readily accept the extra extension caused when the tailwheel descends in flight. (Compression springs will not.) With compression springs a mechanical failure which results in the failure of the tailwheel to unlock, and even a healthy tailwheel with a properly working "detent" pawl, will result in more stress applied to the rudder/horn and rudder-stops, and the more likely damage will occur to the rudder circuit cables, pulleys, and pulley brackets. In other words, instead of a cushioning effect from the original tension springs, rudder application will subject the rudder components to increasing abuse from ever-stronger compression springs.
Tailwheels will never be as positive steering as nosewheels, so don't expect to neatly manuever around on the ground with rudder alone, without some assistance from braking. If your system isn't working satisfactorily, then it needs service, and I wouldn't recommend changing to compression springs.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
So George if I adjust the chain just-taut while the wheel is on the ground to get the best tail steering response and I'm useing tension springs. You don't think the extra tension when in the air causes wear on the rudder horn and tail wheel steering arm? I've seen some of these horns and stering arms sorn near in half buy the chain attachment link.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
I didn't say that things mechanical would never display wear from use. (The use of AN115 cable shackles with AN100 Thimbles and AN393 pins will alleviate the wear on the airframe parts.)
If you imagine that tension springs place a burden on the system, then just think about what compression springs do.
The very purpose of the tension springs is to allow for the tailwheel drop when airborne. They're not there for steering purposes.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
Vic
N2609V
48 Ragwing
A Lanber 2097 12 gauge O/U Sporting
A happy go lucky Ruger Red label 20 ga
12N Aeroflex
Andover NJ http://www.sandhillaviation.com
Very good, clear photo of your tailwheel setup. Now, what is the aircraft just beyond your 170? Just beyond that Red PMA's devise (aka: milk crate; I use them also. Grin!)
That would be one of the globe swift projects yet to be started. there is one also that is just about completed, real sharp. There is also a cub that got flipped in a wind storm that we restored, you can see the picture of MeeToo Aviation's Swift. http://www.sandhillaviation.com/swift.html
Vic
Vic
N2609V
48 Ragwing
A Lanber 2097 12 gauge O/U Sporting
A happy go lucky Ruger Red label 20 ga
12N Aeroflex
Andover NJ http://www.sandhillaviation.com
