The Cessna 120-140 Association Forum

Hey gang, having an issue with the tailwheel chain. It catches on the nut of the leaf spring bracket. I’m not sure how it’s getting slack enough to catch…

Happy to attach more pictures if needed. I’m a new 120 owner and still learning.

CESSNA SERVICE LETTER SLN-01 suggests that you turn those long AN3 bolts upside down so that the nut is on top and the head is on the bottom.

You can find that tidbit in one of Neal's articles
viewtopic.php?f=10&t=134

I also put the chain spring attached to the arm of the tailwheel rather than up by the rudder horn. Yeah, not Scott approved but less to get tangled.

Thanks. I’ll get those swapped around and consider the spring relocation. I’ve seen others do that too.

Any idea why the chain seems to have extra slack (pictured in the last image) sometimes? I’ve noticed it will happen when I start to push the plane backward into the hangar. It always tightens up, but seems like it shouldn’t be that loose.

Any idea why the chain seems to have extra slack (pictured in the last image) sometimes? I’ve noticed it will happen when I start to push the plane backward into the hangar. It always tightens up, but seems like it shouldn’t be that loose.

Here's what Neal had to say on the chain tension for the 2000/3-24B Scott tailwheels. I have a 3200 so the chain springs and tension are a whole different animal. I'd probably confirm you have the correct coil springs and that maybe they might be a little tired? Univair has the 2134 springs
https://www.univair.com/tires-wheels-br ... ng-spring/

Your last pic makes it look like your tailwheel rubber is wearing on one side more?

The hard-tired Scott 3-24B (now the model 2000 which uses the 2134 spring set
per the I-115 bulletin) is to have 25 to 30 pounds of tension in the spring/chain by cutting off enough
chain links to stretch the springs one inch.

I’ve ordered new springs from Univair. The left rudder has seemed a little less effective than the right and the spring looks a little more stretched. So, tired springs definitely tracks.

Is that uneven tailwheel wear a symptom of tired springs? Or something else. It does seem to be getting uneven…

The steering arms on your last tailwheel pic appear to be tilted, coinciding with the tire wear. Perhaps there is something amiss in how it all connects to the tailwheel bracket. I don't immediately suspect it has anything to do with a tired chain spring.

It looks like your plane is relatively level so I'd concentrate on how the leaf springs fit into the bracket. Could be worn or lack of abrasion strip, or worn or lack of the rubber bumper at the front of the leaf spring set, you won't know till you take it all apart for inspection. I've never seen the leaf springs twisted enough to cause that amount of tilt.

You could put a level across the lower door openings in the cockpit to check how level the plane is side to side, then check the level of the tailwheel bracket, may give you a clue.

If you do disassemble, it would be a good time to replace the nuts/bolts. I've heard that 500 hours on the leaf springs is a good time to replace at least the main leaf spring.

If I wiggle the arms, there’s a small amount of play in this bolt/plate. I don’t think that would totally level it up, but I wondered if it needed to be tightened.

Thanks for the tips! I’ll get my local mechanic to take a look and we’ll see what’s up.

By the way, flipped those bolts around and it taxied around without an issue this afternoon.

For entertainment...the additional attached pdf file is from an old catalog

Item 7 is what controls the side to side slop.

Take the wheel and tire off and flip it so the wear evens out...

I have a Scot 3200, so different tail wheel. But my spring attaches to an eyelet bolt that also holds the rudder cable. Basically, this moves the cable outboard about a half inch, maybe an inch on each side.