Scott 3200 Tailwheel Shimmy Adjustment

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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby Bruce Fenstermacher » Thu Dec 31, 2009 6:48 pm

Adding the shackle will fix a chain cut to short as long as it is not cut way to short. :wink:

Also I've found shackles to be about 1.5 times in length of some chain links allowing for in effect a half link adjustment for those of us over complicating this installation. :roll:
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby CAVU Mark » Fri Jan 01, 2010 2:46 am

Posting in Tailwheel Springs and Chain Kit area now. viewtopic.php?f=2&t=7028
See latest post for pictures.
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby jezzicaz789 » Fri Jan 29, 2010 1:33 pm

N1478D wrote:My tailwheel shimmy went away when I replaced the old tire and tube with new ones. However, for those that might still have the problem, I found this in the Cessna Service Information Summary ( 1946 thru 1962 )
Date: 10-24-50
"We have had some reports on Scott pneumatic tailwheels shimmying. The Scott 8" pneumatic tailwheel is designed with a friction type shimmy dampenenr. This friction is regulated by 3 small compression springs inside the upper casting. If the main king pin nut becomes too loose the shimmy dampener effect will be lost. When the shimmy occurs, it is recommended that the large nut be tightened in increments of 1/6 of a turn until the tailwheel starts to bind when rotated by hand. Then back off 1/6 of a turn for correct tension on the shimmy dampener. The king pin nut is on the underneath side of the lower housing directly above the tire. This procedure will definitely assure that compression springs in the dampener are acting against the friction dampener disc. We recommend a tire pressure of 30 pounds on both the 140 and 170 for the 8" pneumatic tailwheel. When connecting the springs and chains on this assembly, it is recommended that the stretch in the springs be from 1/8 to 1/4". The springs used with the 3200 assembly have a high tension rate and if stretched to any extent on assembly the mechanism may not release easily. No slack should be left in the chain and spring hook-up when both sides are connected."


Thanks you for the post.
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby minton » Fri Jan 29, 2010 6:54 pm

For you grease monkeys.

Over greasing of the axel can cause you to force the axel bearing seals from their seats. This will allow the bearing to remain static (not retate) while the wheel rotates. This in turn will wear the bearing seal seat to the point where the seal will not have any "meat" to seat on when you try to reseat it. :? With wheel halves @ $98.00 these days you might reconsider this "over greasing" practice and look at removing the wheel and hand greasing the bearings or a light greasing with a bearing greaser. There is a aftermarket seal available that seams to better handle greasing made by Alaska Bush Wheel. It more resembles a typical seal and seats better. BUT, if the damage is already done I don't know if the new style seal would fit up in any exhisting wear areas.

I have heard of some trying to build up the worn areas with a welding/machining process. This can be problematic first, due to the wheel being a "Cast" product of unknown alloy (Can crack out the wheel) and second the old FAA "Repair approval" for such a process. :cry:
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby minton » Sun Jan 31, 2010 10:01 pm

George,

You know, It would'nt be a bad research project for someone with time on their hands to seek out such products as over sized bearing races and "shim rings". Not only for tailwheels but Cleveland wheels as to change over from 11/4 inch to 11/2 inch axels. :D

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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby GAHorn » Mon Feb 01, 2010 12:40 am

minton wrote:George,

You know, It would'nt be a bad research project for someone with time on their hands to seek out such products as over sized bearing races and "shim rings". Not only for tailwheels but Cleveland wheels as to change over from 11/4 inch to 11/2 inch axels. :D

Minton


Great idea, Minton! Let us know what you find! :twisted:
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby Joe Moilanen » Mon Feb 01, 2010 2:18 am

gahorn wrote:Another method is to install a stainless "cup shim" such as is commonly used to shim wheel bearings inside wheel hubs which are frequently submerged such as boat/marine and amphibious equipment. I do not know of any specifically in this size, but a machine shop can likely produce one by enlarging the hub and mfr'g a shim.
Alternately a substitute bearing with greater O.D. might be incorporated. I do not know of any one having sought approval for this, however.


The seal cups on my wheels have always been a little worn. When I replace seals I put the seals in a press and when you compress them just a little, they expand just enough to make them snug. I also use a little bit of Locktite when installing. When you grease them, use a hand grease gun and just do it real sloooooow until you see grease starting to ooze out from around the axle. One hard pump with a grease gun will pop out even a good fit, especially if the grease is cold and thick.

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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby minton » Mon Feb 01, 2010 9:44 pm

HAR HAR :mrgreen:
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby azmuth1 » Mon Feb 08, 2010 12:11 pm

Do the pins come with the shackles or are the pin purchased separatly?

Looks like a good solution.

There is also a good video on youtube about the adjustment of Scott tail wheel springs.

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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby GAHorn » Mon Feb 08, 2010 4:59 pm

azmuth1 wrote:Do the pins come with the shackles or are the pin purchased separatly?

Looks like a good solution.

There is also a good video on youtube about the adjustment of Scott tail wheel springs.

J. Edmund

Unless someone (like you) identify what "pin" you are discussing... we cannot assist you very well. There are no "pins" sold with the shackles I illustrated earlier.

If the video to which you refer is the one we've already discussed in these forums (you didn't identify which video)... then it is NOT a good video at all. It's got serious errors, as already discussed.
re: viewtopic.php?f=2&t=6896&p=60842&hilit=soooo+sorrrryyyy#p60842
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby minton » Wed Mar 03, 2010 10:46 pm

The pins required are either AN393-_ or MS20392-_C in the appropriate lenth.
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby minton » Fri Apr 02, 2010 8:12 pm

UPDATE: Bushwheels sells the retrofit seals. I just installed a set on my (somewhat) worn wheels (seal seat area). They fit up fine with plenty of meat for the seal to seat. You have to remove the small seal spacer ring meant for the old type seal.
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby DaveF » Mon Dec 16, 2019 5:21 am

Reviving this thread ...

The past few years, when I've disassembled the tailwheel at annual, I've been finding one or more of the pressure plate pins broken. That must mean excessive friction between the pressure plate and bakelite thrust washer. So I assume I've set the king pin nut too tight, but I use the Cessna procedure shown earlier in the thread -- tighten to just binding, then back off. Maybe I'm using the wrong grease? I usually use a moly disulfide EP, and don't add any between annuals.

At $58 a plate, this is an annoying problem. This time I'll try a looser adjustment, but I don't want side-play in the bearing.

Any other suggestions welcome!
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby gfeher » Tue Dec 17, 2019 11:48 am

Dave, as long as your grease is rated NLGI #2, which is the rating of it's consistency/thickness, it should work. I use the tightening procedure in Cessna 10-24-50 S.N.L., which I think is the same procedure you mentioned, and I have not had a problem. Since I began using that procedure about 5 yrs ago, I've not had the shimmy problem that was there when I bought my plane. But heck, try a different grease and see if that helps. For what it's worth, I use Lubrimatic Marine Corrosion Control Trailer Wheel Bearing Grease, which is excellent for this application.
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Re: Scott 3200 Tailwheel Shimmy Adjustment

Postby 170C » Tue Dec 17, 2019 4:15 pm

I have just replaced my original (1980) Scott 3200 with one donated me by a fellow 170 member. As far as I know the only time my unit had been apart prior until now was 10-15 yrs ago when the steering arm was replaced by my then IA with a heavier unit (maybe a 3200-A) steering arm. While I have annually added grease, it has never been disassembled! That's correct. No previous AP/IA's ( I have used at least 8 different ones in two different states) have ever disassembled, inspected or replaced any parts except as noted above. Some uTube videos say to do so every annual and some forum posters say to do so also. What is correct? (My thrust washer had two pins broken. Other parts were worn, but not broken. Seems not bad for 39 yrs of use.)
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