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Scott 3200 Taiwheel refurbishment

I need to take the time to cover some more common issues, wear items etc to add to these videos. Hopefully have time in a few weeks.
 
Thanks for the links Steve, and if you can those other videos would be great.

We thank you for your time and knowledge sharing.


I need to take the time to cover some more common issues, wear items etc to add to these videos. Hopefully have time in a few weeks.




Sent from my iPhone using Tapatalk Pro
 
I was hoping that one of the assembly videos might have a secret, cut-and-dried method of adjusting the bottom nut.
I've always had to rely on trial-and-error,
too loose and you got shimmy and too tight and it didn't want to steer well or kick out to full swivel.
I've been counting how many turns to full tight before disassembling,
then tighten to the same point when reassembling after cleaning & inspecting.
Just did that with my C180: it was one full turn looser than full tight.
But got a little shimmy after reassembly, so pulled the wheel back off & tightened that nut 2 flats worth.
Seems to have done the trick.
 
I was hoping that one of the assembly videos might have a secret, cut-and-dried method of adjusting the bottom nut.
I've always had to rely on trial-and-error,
too loose and you got shimmy and too tight and it didn't want to steer well or kick out to full swivel.
I've been counting how many turns to full tight before disassembling,
then tighten to the same point when reassembling after cleaning & inspecting.
Just did that with my C180: it was one full turn looser than full tight.
But got a little shimmy after reassembly, so pulled the wheel back off & tightened that nut 2 flats worth.
Seems to have done the trick.
The shimmy is because of your head angle not the tightness of the nut. You are keeping it from shimmying by making it harder to swivel. On Cubs I set it up loose so it is easy to turn and break over. It is all by feel for me.
 
You are just masking the problem.


I was hoping that one of the assembly videos might have a secret, cut-and-dried method of adjusting the bottom nut.
I've always had to rely on trial-and-error,
too loose and you got shimmy and too tight and it didn't want to steer well or kick out to full swivel.
I've been counting how many turns to full tight before disassembling,
then tighten to the same point when reassembling after cleaning & inspecting.
Just did that with my C180: it was one full turn looser than full tight.
But got a little shimmy after reassembly, so pulled the wheel back off & tightened that nut 2 flats worth.
Seems to have done the trick.
 
So you're both saying that the tension on that nut doesn't matter? I don't buy that.
I have enough experience with 3200's to know that head angle is often the cause of shimmy,
but also enough to believe that the tension on the kingpin nut can be & often is also a factor.
BTW this is a 10" 3400-series t/w on a C180, & the t/w head angle is fine.
I don't think I've ever seen a C180/185 stinger that put an 8" or 10" t/w at a shimmy-inducing trailing angle.
 
Sure, the head tension will help but if you had a good caster angle it would not shimmy. Post a picture of the head angle when loaded at the point that it shimmies.
 
The torque on the swivel bolt is to preload the bearing. The drag that's felt when trying to swivel the tailwheel is a function of the five (or whatever number you like to use) springs that apply pressure against the thrust washer, up inside the tailwheel head.

Web
 
So you're both saying that the tension on that nut doesn't matter? I don't buy that.
I have enough experience with 3200's to know that head angle is often the cause of shimmy,
but also enough to believe that the tension on the kingpin nut can be & often is also a factor.
BTW this is a 10" 3400-series t/w on a C180, & the t/w head angle is fine.
I don't think I've ever seen a C180/185 stinger that put an 8" or 10" t/w at a shimmy-inducing trailing angle.

I don't have the big tail wheel but the only time mine has ever had a shimmy was when it was a bit low (but didn't show it) on tire pressure.
 
50psi on the 10" t/w tire, good angle.
I'll get a pic of the angle later today.
Not much you can do if the angle is trailing,
never heard of re-arching a stinger like you can a leaf spring.
 
The torque on the swivel bolt is to preload the bearing. The drag that's felt when trying to swivel the tailwheel is a function of the five (or whatever number you like to use) springs that apply pressure against the thrust washer, up inside the tailwheel head.

Yes, but tightening the kingpin nut also compresses those springs.
Don't know any other way to do it, except maybe add spacers to each spring--
like adding washers to an oil pressure relief plunger.
Maybe the springs are weak?
Tailwheel is an XP Mods, installed about 7 years ago--
not that long, so I doubt it's the springs.
 
The only way to adjust spring tension is to go to all five springs or remove them one at a time until it feels right for your operations. The few thousandths of an inch that you might be able to compress the bearing by over torquing it will have a negligible affect on spring tension. Any drag added is the result of excess pressure on the bearing.

Web
 
Sure, the head tension will help but if you had a good caster angle it would not shimmy. Post a picture of the head angle when loaded at the point that it shimmies.

My baby bushwheel head is pretty loose, breaks free really easy. I did what bushwheel bill said and added a block between the spring and fuselage and the angle is good. It never shimmy’s.


Sent from my iPhone using Tapatalk
 
Bill got a big truck mud flap and cut a bunch of spacers out of it for that purpose last time he was here.
 
I was hoping that one of the assembly videos might have a secret, cut-and-dried method of adjusting the bottom nut.
I've always had to rely on trial-and-error,
too loose and you got shimmy and too tight and it didn't want to steer well or kick out to full swivel.
I've been counting how many turns to full tight before disassembling,
then tighten to the same point when reassembling after cleaning & inspecting.
Just did that with my C180: it was one full turn looser than full tight.
But got a little shimmy after reassembly, so pulled the wheel back off & tightened that nut 2 flats worth.
Seems to have done the trick.

you NEED TO ADD more shims under your bearing if tightening the nut stops swiveling on a cessna style scott
 
Sure, the head tension will help but if you had a good caster angle it would not shimmy. Post a picture of the head angle when loaded at the point that it shimmies.

Here's a pic of the tailwheel angle, parked in the hangar.
Same load as usual for day-to-day local ops, minus the pilot.
Tailwheel head angle looks about level or maybe even leading a little (vs trailing).
Camera (phone) is flat -- on the floor, atop a 4x4 block.

tailwheel angle.jpg
 

Attachments

  • tailwheel angle.jpg
    tailwheel angle.jpg
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Here's a pic of the tailwheel angle, parked in the hangar.
Same load as usual for day-to-day local ops, minus the pilot.
Tailwheel head angle looks about level or maybe even leading a little (vs trailing).
Camera (phone) is flat -- on the floor, atop a 4x4 block.

View attachment 44344

Pretty flat but not practiocal to change without replacing the stinger. If tightening the pivot works I would go for it. Easier to fix with spring arch on a Cub.
 
That stinger is $2200.
If replacing mine is the solution,
I think I'll continue to mask the problem.

I think it's just an adjustment thing though--
so far no shimmies, after tightening the kingpin nut 2 flats worth.
 
Something else to consider. I used to work on an ag plane that needed a specific brand/model of tire on the tailwheel. The tire was one of the styles that had a flat face across the tread instead of the more typical rounded type. Any other tire and the tailwheel would shimmy badly no matter the load on it.

Maybe this install would respond to another tire?

Web
 
The shimmy is because of your head angle not the tightness of the nut. You are keeping it from shimmying by making it harder to swivel. On Cubs I set it up loose so it is easy to turn and break over. It is all by feel for me.
That works great except for a cub type aircraft that has a 200+# tail weight, and then all bets are off. 3" extended gear and a short mount and 31" tires causes all kinds of things to break, like the pins on the thrust plate, the fork casting where the pin for the lock spring goes is broke, everything wants to come loose! My taylorcraft weighs 68# and I dont break anything, but tripple that and you will find all sorts of problems if you fly a lot and your tail is heavy. Tim
 
I am not having those issues. My head would get loose on the spring but I solved that with a 2 bolt head. Rearched springs at the truck spring shop and shimmy went away even when loaded heavy on asphalt.
 
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So you're both saying that the tension on that nut doesn't matter? I don't buy that.
I have enough experience with 3200's to know that head angle is often the cause of shimmy,
but also enough to believe that the tension on the kingpin nut can be & often is also a factor.
BTW this is a 10" 3400-series t/w on a C180, & the t/w head angle is fine.
I don't think I've ever seen a C180/185 stinger that put an 8" or 10" t/w at a shimmy-inducing trailing angle.
then you have not spent enough time in Alaska, they get bent up there all the time...
 
I am not having those issues. My head would get loose on the spring but I solved that with a 2 bolt head. Reached springs at the truck spring shop and shimmy went away even when loaded heavy on asphalt.
Owner bought a 2 bolt spring, I tried to get them to convert from Nyloc to castlated nuts, changed the angle, went from 3 springs to 5 and still will get a shimmy after about 10-30 hours out from the annual. Every year it is a thrust plate replacement due to broken pins, if I leave the king pin nut with any looseness, instant shimmy. I have had the kingpin caster angle anywhere from 0 degrees to 15 positive with leaf spring changes and it will still shimmy with weight on the tail. I am to the point that a really heavy tail will just do that.

I have another customer with a tailwheel that is 240+ and the king pin came loose from the main casting, that was a NO GO and it needed a thrust plate. One of the thrust plane pins was missing, i think there was some owner maintenance going on with it, but I will have it fixed next weekend.
 
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