After a few years of pushing really hard on the trim wheel of my C180, I decided to take apart the sticky horizontal jack screws and get them dialed in for years of silky smooth action in the future.

I have found a few less than desirable conditions in them, but close inspection reveals that they are in pretty decent shape.

One thing that I found is that the sprockets that are connected at the base of the jack screws have a little wobble to them. Accurate measurements were taken using multiple methods in our machine shop that indicate that none of the parts are even slightly out of round, which would suggest that they are not worn.

One thought is that the jack screw assemblies rotate slightly about the base in a vertical plane, but the bicycle style chain is designed to transfer motion that is limited to a horizontal plane. This wobble could be intended to prevent binding in the drive system. Do any of the Skywagon gurus here know if this looseness is part of the original design?

It is a pretty significant effort to pull the jack screws out and replace them, so I'd rather not do it again at any time in the near future. I intend to reinstall them perfectly and within tolerance.

Scolopax wrote:After a few years of pushing really hard on the trim wheel of my C180, I decided to take apart the sticky horizontal jack screws and get them dialed in for years of silky smooth action in the future.

I have found a few less than desirable conditions in them, but close inspection reveals that they are in pretty decent shape.

One thing that I found is that the sprockets that are connected at the base of the jack screws have a little wobble to them. Accurate measurements were taken using multiple methods in our machine shop that indicate that none of the parts are even slightly out of round, which would suggest that they are not worn.

One thought is that the jack screw assemblies rotate slightly about the base in a vertical plane, but the bicycle style chain is designed to transfer motion that is limited to a horizontal plane. This wobble could be intended to prevent binding in the drive system. Do any of the Skywagon gurus here know if this looseness is part of the original design?

It is a pretty significant effort to pull the jack screws out and replace them, so I'd rather not do it again at any time in the near future. I intend to reinstall them perfectly and within tolerance.

Scolopax, I can't answer your question, but have you searched the forums on the 180/185 Club website? There have been a couple of extensive discussions about the jack screws recently and over the years that would give you an amazing amount if information if you want to take a look.

CapnMike wrote:

Scolopax wrote:After a few years of pushing really hard on the trim wheel of my C180, I decided to take apart the sticky horizontal jack screws and get them dialed in for years of silky smooth action in the future.

I have found a few less than desirable conditions in them, but close inspection reveals that they are in pretty decent shape.

One thing that I found is that the sprockets that are connected at the base of the jack screws have a little wobble to them. Accurate measurements were taken using multiple methods in our machine shop that indicate that none of the parts are even slightly out of round, which would suggest that they are not worn.

One thought is that the jack screw assemblies rotate slightly about the base in a vertical plane, but the bicycle style chain is designed to transfer motion that is limited to a horizontal plane. This wobble could be intended to prevent binding in the drive system. Do any of the Skywagon gurus here know if this looseness is part of the original design?

It is a pretty significant effort to pull the jack screws out and replace them, so I'd rather not do it again at any time in the near future. I intend to reinstall them perfectly and within tolerance.

Scolopax, I can't answer your question, but have you searched the forums on the 180/185 Club website? There have been a couple of extensive discussions about the jack screws recently and over the years that would give you an amazing amount if information if you want to take a look.

This inquiry on BCP will either make the case for or invalidate "the club". Trying to avoid rejoining, as the exclusive club attitude is not what I really wish to associate myself with.

Scolopax wrote:

CapnMike wrote:
Scolopax, I can't answer your question, but have you searched the forums on the 180/185 Club website? There have been a couple of extensive discussions about the jack screws recently and over the years that would give you an amazing amount if information if you want to take a look.

This inquiry on BCP will either make the case for or invalidate "the club". Trying to avoid rejoining, as the exclusive club attitude is not what I really wish to associate myself with.

I hear you. That hoity-toity crap isn't my bag either, but after looking through those archives on a couple of Skywagon issues, I've decided that I'd gladly pay double the annual membership to have access to the information.

I think if I replaced mine, I'd go with the stainless steel ones that McFarlane is selling now. How is the roll pin that holds the sprocket to the shaft. McFarlane uses a little bigger roll pin since it fails or backs out, you have a problem.

The original Cessna actuators use a 3/32" roll pin to attach the sprockets and retaining collars to the screw bars. These pins are critical as the front of the stabilizer would detach from the airframe if they failed.

http://www.mcfarlane-aviation.com/Produ ... mber=1111&

The original Cessna actuators use a 3/32" roll pin to attach the sprockets and retaining collars to the screw bars. These pins are critical as the front of the stabilizer would detach from the airframe if they failed.

Anybody ever seen this happen?

I've rebuilt several jacks crews on both 180's and 185's, the wobble you mention was on all of them, and I left them like that....but more often than not, the bearing in the left hand jack screw is shot... If your rebuilding after a shear pin failure in the front (due to bad bearing), cable rigging is critical to avoid cable binding issues. Equally important is correct cable tension when done. A properly overhauled trim system will provide a smooth, buttery feel and won't creep in most turbulence...Joe

Guy I bought my 53 from says he rebuilt the jack screws & installed new boots in 2011. Trim is smooth on the ground, and trimming nose up in flight, but trimming nose down in flight is stiffer than hell. Is this normal due to the air load on the stabilizer?

My 62 model is nice and smooth both ways. The clicker gives it some resistance, but it is definitely not stiffer then hell.

Trim is smooth on the ground, and trimming nose up in flight, but trimming nose down in flight is stiffer than hell. Is this normal due to the air load on the stabilizer?

Mine is like that too. I just let go fo the yoke to neutralize pressure and then it goes pretty easy---don't want to break the roll pin in the trim adjustment wheel.

Not sure I under stand the loose sprockets from the original post here.Are you saying the roll pins are tight in the shaft but the sprockets are loose on the shaft and the roll pins. Seems if the sprockets are loose then it wouldn't be a snug fit for the bearings in the bottom bracket and the horizonal stab would have up and down play.

I rebuilt the jack screws on mine a couple years ago. I could hardly turn it by the time I finally fixed it. I replaced every little part I could and basically just reused the jack screws themselves. The jack screws are just about the only expensive parts and the rest wasn't too bad. Once you get the jack screws out, rebuilding them isn't too tough. By the way, the little roll pins don't retain the stabilator. There should be a physical stop at the front that will stop the stabilator from rotating up too far no matter what fails on the jack screw. It's basically a bracket that bolts in above the leading edge. You would need multiple failures for the stabilator to depart. The trim is butter smooth now.

Wayne

Edit: By the way, I've heard that when the screw and barrel on one of the jack screws comes completely unthreaded, it makes it very difficult to trim and can be indicated by a need to unload the stabilator in flight slightly to make it easier too trim. You can't see it because of the boot but, of course, that means only one jackscrew is holding the stabilator down. While the bracket will keep the stabilator from departing if that one jackscrew fails, it will still give you one hell of a pitch down and would not be fun. If your trim isn't trimming very easily, dig into it and find out why.

Help!!!! Maybe there's someone out there who's had this problem. Screw Jacks.
1961 Cessna 182D. This plane sat for a couple years before I bought it and had a annual done. The nose trim wheel was locked up at annual.
AP was able to get some oil in there and it became free but only to Trim UP. It trims up easily but when returning to neutral trim and going to down trim the trim wheel loads up and stops, NO DOWN TRIM. If you put pressure on the down trim wheel it stops When you back it off towards neutral you hear a little THUMP in the tail.
It's almost like cocking a guns hammer then backing the trim wheel to UP fires the gun, poor example I know.
How is it possible the trim wheel works freely and fine for nose up but totally stops for nose down, my AP and IA are stumped ??

Bob W wrote:Help!!!! Maybe there's someone out there who's had this problem. Screw Jacks.
1961 Cessna 182D. This plane sat for a couple years before I bought it and had a annual done. The nose trim wheel was locked up at annual.
AP was able to get some oil in there and it became free but only to Trim UP. It trims up easily but when returning to neutral trim and going to down trim the trim wheel loads up and stops, NO DOWN TRIM. If you put pressure on the down trim wheel it stops When you back it off towards neutral you hear a little THUMP in the tail.
It's almost like cocking a guns hammer then backing the trim wheel to UP fires the gun, poor example I know.
How is it possible the trim wheel works freely and fine for nose up but totally stops for nose down, my AP and IA are stumped ??

Sounds like there’s a corroded section on the threads. The “thump” is it coming unstuck when you back off the tension. I’m guessing it’s time to dig in, disassemble the tail and fix it properly.

Your toes are going to curl when you see how much Cessna wants for a barrel/screw kit. Macfarlane kit is better and cheaper.

Thanks so much for taking the time to reply to my question.
I doubt the screws are worn as they only have 2700 hrs TT. Corrosion must be the issue and I've seen those aftermarket kits and yes that's the way to go.
Somewhere here I read a post where a guy removed his tail feathers and serviced his trim jack screws. His comment was, it wasn't that big of a deal. If the tail comes off I'm go to document the whole process and post something here so others can see what their dealing with. My curiosity is growing and I almost can't wait to see those mysterious hard to get to screw jacks.
Maybe someone else on here will comment on their experiences with early Cessna trim screw jacks.

Be sure to photo the way the jackscrews are rigged; the manual for my 1958 C180B had it exactly backwards.

jrc111 wrote:Be sure to photo the way the jackscrews are rigged; the manual for my 1958 C180B had it exactly backwards.

Actually, the later years AMM has a better procedure than that early 100 series AMM. Thanks for all the great photos JCR111. I love the '59. Best year!

Thanks, C180_Guy! (Just in case there’s some confusion, my C180 was made in mid-Dec 1958 but under the serial number block which defines it a C180B, which is considered as 1979 model).

Problem solved. I went to the airport Friday afternoon 6/19/20 to finish my Flight Review with my instructor and the plane wasn't in it's tie down it was over in the maintenance hanger. Ummm, my A&P had taken it back in to address the trim problem but had not started working on it yet. So I left and went home thinking it would be another dead end.
About 4:30 my phone rang and it was him, expecting bad news I sat down. He asked me how I was doing and I replied you tell me, he responded with your doing very well, trim is working fine now. He flew the 182 and it now has full up trim travel and full down trim travel. The old girl is going in Monday for new tinted windscreen, windows and new paint. It's a very exciting time.

Good deal! Did your mech say what the matter was?

Hey Bob W.....how about some info re your solution, fix or maintenance event....when you seek help it would be nice to hear the result....