Tailwheel on 170a
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
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Robert Bishop
- Posts: 9
- Joined: Tue May 07, 2002 7:56 pm
Tailwheel on 170a
I'm having trouble with my tailwheel it seem that I have no control on the ground steering due to the fact that the chains are pulling up at a 45% angle or more rather than pulling forward I replaced my tailwheel spring sometime ago because they were chrome by the previous owner .Even before I change the spring it was hard to steer? Any Idea or suggestions and what angle this might be?
God speed& smooth air
You might check to see that the tail wheel main spring has not fatigued and bent. The piviot pin of the caster should be vertical. If it is angled foward you actually have to lift the tail to turn. I have the same angle you refer to and it dose not seem to be problem. If you are new to tail wheels you might check with a local with tailwheel experience. Its funny but with out any adjustments my tailwheel worked much better when I got more experience 
Bill K
Bill KPolished 48 170 Cat 22 JD 620 & Pug
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zero.one.victor
- Posts: 2271
- Joined: Tue Apr 23, 2002 12:11 am
Actually,the older & saggier the tailspring the better the steering,the chains will not be pulling up as much. Of course,the older & saggier the tailspring,the more likely it is to break & let the tailwheel assembly bop around & beat up the bottom of the rudder!
I put on the 3214T tailwheel steering arm a couple years ago,it's not the big cureall for poor steering that it's cracked up to be. But it is a lot beefier than the stock arm,something else will bend or break before it does!
Eric
I put on the 3214T tailwheel steering arm a couple years ago,it's not the big cureall for poor steering that it's cracked up to be. But it is a lot beefier than the stock arm,something else will bend or break before it does!
Eric
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Rudy Mantel
For ease of steering it's really important to have the tail wheel shaft vertical. This is accomplished by COLD bending the aft end of the long spring. As Eric said, these springs are known to break so it's a good idea to occasionally replace it with a new one.
The tension on the two steering springs (I assume those were the ones that were chromed) should be light.
Good luck-
Rudy
The tension on the two steering springs (I assume those were the ones that were chromed) should be light.
Good luck-
Rudy
The beefier Scott 3214T steering arm actually makes the steering geometry worse than the stock arm. Because it is longer (approx. 1/2" per side) than the stock 3214 arm, the springs/chain travel thru less arc around the tailwheel pivot for a given amount of rudder pedal deflection. Its only real advantage is that it is stronger. The improvement claimed by the upturned ends of the 3214T I believe is undetectible.
Real improvement in the steering geometry can be had by installing what is commonly called a "seaplane bellcrank". This bellcrank extension gives a longer lever arm to the stock rudder bellcrank, increasing the amount of chain travel for a given amount of rudder pedal travel. Originally designed so that it gave C-170 seaplane float rudders more travel when manuevering, it also works equally well with tailwheels. This extension is typically a piece of 0.125" 4130 steel 1" wide by 12" long that is shimmed below the existing rudder bellcrank. The rudder cables attach to the existing bellcrank but the bolts are longer and also go thru the extension and hold it in place. Of course the tailwheel springs and chain are then moved from the stock location (in the little steel tabs) out to the end of the extension. You will have to get new chains as you will need more length to make this change. So in summary, to improve the old style 170 steering, increase bellcrank throw with an extension and you can leave the old steering arm on, it works fine.
By the way, changing your tail leaf spring to the heavier L-19 spring will change the spring tensions and tailwheel king post angle too. Beacuase it is stiffer it behaves quite a bit differently.
Bruce Christie
Real improvement in the steering geometry can be had by installing what is commonly called a "seaplane bellcrank". This bellcrank extension gives a longer lever arm to the stock rudder bellcrank, increasing the amount of chain travel for a given amount of rudder pedal travel. Originally designed so that it gave C-170 seaplane float rudders more travel when manuevering, it also works equally well with tailwheels. This extension is typically a piece of 0.125" 4130 steel 1" wide by 12" long that is shimmed below the existing rudder bellcrank. The rudder cables attach to the existing bellcrank but the bolts are longer and also go thru the extension and hold it in place. Of course the tailwheel springs and chain are then moved from the stock location (in the little steel tabs) out to the end of the extension. You will have to get new chains as you will need more length to make this change. So in summary, to improve the old style 170 steering, increase bellcrank throw with an extension and you can leave the old steering arm on, it works fine.
By the way, changing your tail leaf spring to the heavier L-19 spring will change the spring tensions and tailwheel king post angle too. Beacuase it is stiffer it behaves quite a bit differently.
Bruce Christie
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Bruce Fenstermacher
- Posts: 10320
- Joined: Tue Apr 23, 2002 11:24 am
A friend has a 170A which came from the factory with an autopilot. Part of the autopilot appearently is a different rudder bellcrank than is normally found on a 170. This bellcrank is longer than the common one. He still has this bellcrank on the original rudder from his plane which was replaced with another because of damage. His replacement rudder has extenstions rivited on to the horn to match the lengh of the original. Of course the autopilot is long gone but the extentions are still there and that is where he hooks his chains (He didn't know any better.) This would be about what Bruce Christie is talking about. I've flown the plane and it has good ground handling. Does anyone know anything about a different bellcrank from Cessna like the one my friend has which would greatly improve the steering geometry.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
The extension was not designed to be used on wheels. If you are operating on skis and going thru the snow the extension can get bent or bend the rudder horn. Just food for thought.N3243A wrote:The beefier Scott 3214T steering arm actually makes the steering geometry worse than the stock arm. Because it is longer (approx. 1/2" per side) than the stock 3214 arm, the springs/chain travel thru less arc around the tailwheel pivot for a given amount of rudder pedal deflection. Its only real advantage is that it is stronger. The improvement claimed by the upturned ends of the 3214T I believe is undetectible.
Real improvement in the steering geometry can be had by installing what is commonly called a "seaplane bellcrank". This bellcrank extension gives a longer lever arm to the stock rudder bellcrank, increasing the amount of chain travel for a given amount of rudder pedal travel. Originally designed so that it gave C-170 seaplane float rudders more travel when manuevering, it also works equally well with tailwheels. This extension is typically a piece of 0.125" 4130 steel 1" wide by 12" long that is shimmed below the existing rudder bellcrank. The rudder cables attach to the existing bellcrank but the bolts are longer and also go thru the extension and hold it in place. Of course the tailwheel springs and chain are then moved from the stock location (in the little steel tabs) out to the end of the extension. You will have to get new chains as you will need more length to make this change. So in summary, to improve the old style 170 steering, increase bellcrank throw with an extension and you can leave the old steering arm on, it works fine.
By the way, changing your tail leaf spring to the heavier L-19 spring will change the spring tensions and tailwheel king post angle too. Beacuase it is stiffer it behaves quite a bit differently.
Bruce Christie
Tim
Bruce, I hear what you say and had been told that for ski operation, that extension would be a great idea. I will try next winter. I also saw what mit said and I don't anticipate that problem cause I have a penetrating ski for the tail.
Now, about worse geometry with the 3200A (3214T arm). One thing it fixed for me and others is the angle between the bellcrank and the steering arm is less, which means less up force on the arms. And, if, like me, you buy a new 3200 tail wheel (or 3214 arm), with the regular 3214 arm, you will find out quickly that the alloy is different and softer than on your old 3200; and if the tension springs are too stiff (or hit a hole in a turn), the very first turn you'll make on the ground will result in a severe bend (up) in that arm. I modified my new 3200 to become a 3200A and added the clevis to the horne and with new tail springs (changed all last year and the main this year), I have a good geometry of caster and have ok ground handling in summer, bleep in the snow. By the way, my main gear was absolutely out of alignment before we installed the 180 gear; don't forget that part of your steering equation.
The one thing I was told to be careful about the 12" bar is that it works great with tail ski, or on grass, sand and gravel but will bite you faster on hard top. The 170 has a heavy tail compared to a 120-140 or a Piper, it is harder to pick up and move in deep snow, doesn't steer as easy on ground, but this is all part of this breed and with differential braking and everyting rigged right, it is still a fantastic, fun plane. Any and every trick we learn on these posts are bound to get a great range of reactions; thumbs up or down. About some mods, we can't jump to conclusionn on hear say. Example: I've only had my '52 for about a year and 175 hours; my first tail dragger, I've changed, beefed up, modified all kinds of stuff to "JD" it; to make it more comfy, safe and fun for me. It is rigged beautifully and flies pretty much as expected. The most important part of the flight is taking off and landing. It slapped me on the wrist a couple of times, but so far, never bit me. I've only flown 2 more 170's: A friend's '53 with 6.00 X 6 (mine are 8.00) with pants. It is rigged well and well maintained. I found it easier to land and handle on the hard top; smaller footprint I believe makes that difference. The other bird was a 170A with Horton STOL kit and 180 gear (mine now has 180 gear too and I love it). I found the controls to be sloppy, slower and squirly on the ground. The owner thaught it was fine, it was also his first tail dragger.
What made the biggest changes for me was after months of trying all that made sense to me, picked up on and off this post, from reading and watching videos on tail dragger flying; particularly talking to experienced 170 pilots and biggest thing of all, I had the chance to fly with a friend who is a great pilot who just loves 170's and to top it off, this guy can really teach. He can pick up on the little things you do wrong or a better way to get something right, etc. He pushed the envelope on both me and the plane. I came out of it with more confidence in me and the plane. Another friend used to barnstorm with a B, back when they were new, out of a 450' grass strip; I sure paid attentionn to his take on the bird; which is one of his all time favorites. I already had alot of respect for tail draggers, cause of all I'd heard and after over 20 years of "driving" airplanes, I wanted to "fly" a 170.
So, if you haven't already done so, find an experienced 170 pilot, fly with him/her, talk to and fly with as many 170 pilots as you can, do what fits your personality and experience level on type and given conditions and have fun. JD
Now, about worse geometry with the 3200A (3214T arm). One thing it fixed for me and others is the angle between the bellcrank and the steering arm is less, which means less up force on the arms. And, if, like me, you buy a new 3200 tail wheel (or 3214 arm), with the regular 3214 arm, you will find out quickly that the alloy is different and softer than on your old 3200; and if the tension springs are too stiff (or hit a hole in a turn), the very first turn you'll make on the ground will result in a severe bend (up) in that arm. I modified my new 3200 to become a 3200A and added the clevis to the horne and with new tail springs (changed all last year and the main this year), I have a good geometry of caster and have ok ground handling in summer, bleep in the snow. By the way, my main gear was absolutely out of alignment before we installed the 180 gear; don't forget that part of your steering equation.
The one thing I was told to be careful about the 12" bar is that it works great with tail ski, or on grass, sand and gravel but will bite you faster on hard top. The 170 has a heavy tail compared to a 120-140 or a Piper, it is harder to pick up and move in deep snow, doesn't steer as easy on ground, but this is all part of this breed and with differential braking and everyting rigged right, it is still a fantastic, fun plane. Any and every trick we learn on these posts are bound to get a great range of reactions; thumbs up or down. About some mods, we can't jump to conclusionn on hear say. Example: I've only had my '52 for about a year and 175 hours; my first tail dragger, I've changed, beefed up, modified all kinds of stuff to "JD" it; to make it more comfy, safe and fun for me. It is rigged beautifully and flies pretty much as expected. The most important part of the flight is taking off and landing. It slapped me on the wrist a couple of times, but so far, never bit me. I've only flown 2 more 170's: A friend's '53 with 6.00 X 6 (mine are 8.00) with pants. It is rigged well and well maintained. I found it easier to land and handle on the hard top; smaller footprint I believe makes that difference. The other bird was a 170A with Horton STOL kit and 180 gear (mine now has 180 gear too and I love it). I found the controls to be sloppy, slower and squirly on the ground. The owner thaught it was fine, it was also his first tail dragger.
What made the biggest changes for me was after months of trying all that made sense to me, picked up on and off this post, from reading and watching videos on tail dragger flying; particularly talking to experienced 170 pilots and biggest thing of all, I had the chance to fly with a friend who is a great pilot who just loves 170's and to top it off, this guy can really teach. He can pick up on the little things you do wrong or a better way to get something right, etc. He pushed the envelope on both me and the plane. I came out of it with more confidence in me and the plane. Another friend used to barnstorm with a B, back when they were new, out of a 450' grass strip; I sure paid attentionn to his take on the bird; which is one of his all time favorites. I already had alot of respect for tail draggers, cause of all I'd heard and after over 20 years of "driving" airplanes, I wanted to "fly" a 170.
So, if you haven't already done so, find an experienced 170 pilot, fly with him/her, talk to and fly with as many 170 pilots as you can, do what fits your personality and experience level on type and given conditions and have fun. JD
It's important to remember that Cessna/Scott developed this combination after trial and error, and the solution they came up with was probably the best all-around one available.
The problem with "field" adjustments and changes in designs is that one never has confidence that the owner had a correct installation with good, serviceable equipment to begin his "experiment". There was no "control" group.
The final installation, as depicted in the Cessna IPC (Illustrated Parts Catalog) is the correct installation, and if things are in good mechanical condition, will work properly and without any "modifications" necessary. In fact, most of the modifications discussed are either incorrect, improperly documented, and illegal, or are "cover-ups" for mechanical deficiencies in the system. (Just because your airplane or your technique is difficult is less than satisfactory, doesn't mean that your system is somehow wrong. It would be better to operate another airplane, or get an experienced pilot or mechanic to operate yours, ...before jumping to conclusions.)
The so-called "T" steering arm mod, is an adaptation to this airplane of parts originally designed for the 180/185 and Ag-aircraft series that had a completely different arrangement. Those airplanes had cables, not springs and chains, which tied the steering arm to the rudder system. That cable was more robust and potentially applied more pressures to the steering arm, so the arm required "beefing up". Although that part may fit the 170 and work fine, it is not the correct part. (I'm not condemning it, I'm just pointing this out.)
The original geometry of the 170's placed the tension springs at the rudder bellcrank (either directly, or via small tabs) and then routed chains down to the steering arm. There is sufficient tension to make the chains "taut" but not so as to actually lengthen the springs. (BTW, landing gear adjustments on the 170 should be performed at 2000 lbs weight. Additional weight from aircraft loading will apply slightly less tension, and lesser weights, or an in-flight condition, will increase tensions.)
If you find that taxiing around on a large ramp, no-wind conditions, is slightly un-responsive, ...then things are probably just about right. Full rudder deflection will have only a slow and gradual turning effect on your tailwheel steering, but it will have an effect if your tailwheel is correctly mounted, and in proper condition. A 45-foot turning radius is about right. Tighter turning radiuses will require encouragement in the form of brakes. This is normal. Don't expect tri-cycle-gear ground-steering from a taildragger.
There has been much discussion of the "angle" of the tailwheel steering post. While it's true that a forward slanting "angle" (negative caster) will not steer well, it is not true that the tailwheel bracket (pn 3216) must be absolutely level. In fact, a slightly positive caster is correct, and any bending off the main tailwheel spring to change this relationship is neither necessary nor adviseable. It is only necessary that the wheel's axle be aft of the pivot. There is sufficent aft sweep of the fork to allow the wheel to properly trail. (Remember also that heavier weights will tend to "level" this pivot angle.)
If your airplane is difficult to steer, then the most likely culprits are lost steering spring tensions, improper chain tensions, bent or sagging tailwheel mainspring, and #1 on the list, improper/defective tailwheel maintenance/condition. Look at your Aircraft Spruce catalog (you DO have this valuable reference, don't you?), and don't be afraid to take yours apart and inspect it's condition. Clean it up, replace worn parts, and lubricate and reassemble it annually at least. Do not fear overgreasing your tailwheel steering/mounting bracket. Grease it until you see grease, then wipe it clean. (It's neither necessary nor helpful to overgrease your axle, however.)
My comments are meant to add a bit of "sense" to the problem. Rushing to make modifications to your tailwheel and it's steering is probably the wrong reaction to a perceived difficulty in steering. Keep in mind that this system wasn't designed to travel long distances in traffic. It was only supposed to get you to/from the runway and into the air.
The problem with "field" adjustments and changes in designs is that one never has confidence that the owner had a correct installation with good, serviceable equipment to begin his "experiment". There was no "control" group.
The final installation, as depicted in the Cessna IPC (Illustrated Parts Catalog) is the correct installation, and if things are in good mechanical condition, will work properly and without any "modifications" necessary. In fact, most of the modifications discussed are either incorrect, improperly documented, and illegal, or are "cover-ups" for mechanical deficiencies in the system. (Just because your airplane or your technique is difficult is less than satisfactory, doesn't mean that your system is somehow wrong. It would be better to operate another airplane, or get an experienced pilot or mechanic to operate yours, ...before jumping to conclusions.)
The so-called "T" steering arm mod, is an adaptation to this airplane of parts originally designed for the 180/185 and Ag-aircraft series that had a completely different arrangement. Those airplanes had cables, not springs and chains, which tied the steering arm to the rudder system. That cable was more robust and potentially applied more pressures to the steering arm, so the arm required "beefing up". Although that part may fit the 170 and work fine, it is not the correct part. (I'm not condemning it, I'm just pointing this out.)
The original geometry of the 170's placed the tension springs at the rudder bellcrank (either directly, or via small tabs) and then routed chains down to the steering arm. There is sufficient tension to make the chains "taut" but not so as to actually lengthen the springs. (BTW, landing gear adjustments on the 170 should be performed at 2000 lbs weight. Additional weight from aircraft loading will apply slightly less tension, and lesser weights, or an in-flight condition, will increase tensions.)
If you find that taxiing around on a large ramp, no-wind conditions, is slightly un-responsive, ...then things are probably just about right. Full rudder deflection will have only a slow and gradual turning effect on your tailwheel steering, but it will have an effect if your tailwheel is correctly mounted, and in proper condition. A 45-foot turning radius is about right. Tighter turning radiuses will require encouragement in the form of brakes. This is normal. Don't expect tri-cycle-gear ground-steering from a taildragger.
There has been much discussion of the "angle" of the tailwheel steering post. While it's true that a forward slanting "angle" (negative caster) will not steer well, it is not true that the tailwheel bracket (pn 3216) must be absolutely level. In fact, a slightly positive caster is correct, and any bending off the main tailwheel spring to change this relationship is neither necessary nor adviseable. It is only necessary that the wheel's axle be aft of the pivot. There is sufficent aft sweep of the fork to allow the wheel to properly trail. (Remember also that heavier weights will tend to "level" this pivot angle.)
If your airplane is difficult to steer, then the most likely culprits are lost steering spring tensions, improper chain tensions, bent or sagging tailwheel mainspring, and #1 on the list, improper/defective tailwheel maintenance/condition. Look at your Aircraft Spruce catalog (you DO have this valuable reference, don't you?), and don't be afraid to take yours apart and inspect it's condition. Clean it up, replace worn parts, and lubricate and reassemble it annually at least. Do not fear overgreasing your tailwheel steering/mounting bracket. Grease it until you see grease, then wipe it clean. (It's neither necessary nor helpful to overgrease your axle, however.)
My comments are meant to add a bit of "sense" to the problem. Rushing to make modifications to your tailwheel and it's steering is probably the wrong reaction to a perceived difficulty in steering. Keep in mind that this system wasn't designed to travel long distances in traffic. It was only supposed to get you to/from the runway and into the air.
Last edited by GAHorn on Sun Jun 19, 2005 4:33 pm, edited 1 time in total.
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Robert Bishop
- Posts: 9
- Joined: Tue May 07, 2002 7:56 pm
Tailwheel problems
Hi Geo! Maybe I;m trying to control my 170 Like a nose wheel aircraft and you are right about jumping in to fix something that might not be wrong.I can control it on the ramp and when I have to turn sharp the breaks are needed, this sounds normal from reading your comments.Thanks for the heads up . I will see about trying another 170 on the ramp before I do any Fixing 
Thanks again Bish
Thanks again BishGod speed& smooth air
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4BravoWhiskey
- Posts: 54
- Joined: Wed May 01, 2002 6:22 pm
grease
George, my only comment on your comments is that I've heard that unlike good southern cooking, you can actually get too much grease in the the tailwheel assembly, preventing the disks to lock into place when the tailwheel is straight. Of course I heard this just after pumping a good load of grease into my nearly new tailwheel assembly one day! I haven't noticed any problem though, so either I didn't overgrease it, or tailwheels are like chicken-fried steak afterall.
Jack
Jack
'53 170B N314BW
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zero.one.victor
- Posts: 2271
- Joined: Tue Apr 23, 2002 12:11 am
Scott tailwheels are like ducktail haircuts: there's no such thing as too much grease!
Another note on steering chain geometry: the Scott installation drawing for the 3200 ( Bulletin No. I-168,Scott Aviation Corporation,issue date 4-8-49,copyright 1949!) shows the bolts where the rudder cables attach to the rudder bellcrank being replaced by AN42-6 eyebolts. These are shown mounted eye down,with the steering spring hooked on the eye. This would have the same effect on geometry as the turned up steering arms on the tailwheel,combined with the turned-up arms it might actually improve steering.
I don't think I've ever seen a 170 with these eyebolts which I think is actually the "approved" method of installation,my steering springs hook onto little tabs rivetted to the rudder bellcrank inboard of the rudder cable attach. The eyebolt method would increase tailwheel travel for a given amount of rudder deflection,as well as give a straighter pull. Anybody running these eyebolts?
Eric
Another note on steering chain geometry: the Scott installation drawing for the 3200 ( Bulletin No. I-168,Scott Aviation Corporation,issue date 4-8-49,copyright 1949!) shows the bolts where the rudder cables attach to the rudder bellcrank being replaced by AN42-6 eyebolts. These are shown mounted eye down,with the steering spring hooked on the eye. This would have the same effect on geometry as the turned up steering arms on the tailwheel,combined with the turned-up arms it might actually improve steering.
I don't think I've ever seen a 170 with these eyebolts which I think is actually the "approved" method of installation,my steering springs hook onto little tabs rivetted to the rudder bellcrank inboard of the rudder cable attach. The eyebolt method would increase tailwheel travel for a given amount of rudder deflection,as well as give a straighter pull. Anybody running these eyebolts?
Eric
Tailwheel
I changed to the eyebolt system when I bought my 54 B model in '95 and added the turned up - beefed up arm assembly last year when I overhauled the tailwheel system. If there was an improvement in handling it was too subtle for me to notice but then I like the way my plane handles on the ground and in the air. It certainly did not hurt the steering and I still like the theory about the improvement in steering geometry. A 170 will always need a gentle assist with the brakes when turning beyond a certain point. Just keep the tailwheel and brakes in good condition and enjoy a wonderful airplane.
I also have a 3200A (turned up arms) and the eyebolts. The angle is definitely not as steep. I am not sure if it improves steering, but since doing that, rigging the rudder properly, aligning the mains, changing the tail springs... It tracks nicely but still nneed brake assist in X-Wind taxiing and to turn sharp. JD