Tailwheel Springs - Continued

[dkenney1]

Thank you everyone for the information and advice. Old man winter is reluctant to loosen his grip here in western NY, but we went to the plane today to do some cleaning and get some pictures. Based on my search of previous threads on this website I saw one with a picture of the spring assembly and it looked like a rubber tube enclosed all the springs where the rear bracket attaches to the airframe. Based on the pics I attached it seems odd to me that mine has a gap between the top spring and the airframe, does that seem correct? The gap is created by a 4" long chunk of rubber about 1/4" thick that appears to resemble a cutout of a truck mud flap. Between the bottom frame and the bracket is a very thin piece of rubber. Perhaps the two rubber pieces should swap locations?

Based on your advise I confirmed no wrinkles in fabric or anything appeared loose. Set the tail on padded saw horse and tugged on everything and nothing seemed loose or made noise. I disassembled and checked all three holes and no elongated holes, everything threaded easily and no looseness or stripped threads. Opened inspection plates and looked with mirror and crawled down the fues (not fun when you're 6'3") and all welds looked solid and no visible corrosion.

Again any ideas or thoughts on the above questions would be appreciated. It seems a crime that I have not flown it since December 20, but everytime I have time it's snowing, unplowed runway and/or windy.

Thanks,

Darrin

[Pearson]

Re: Tailwheel Springs - Continued

Darrin, in the two pictures you posted two things stood out to me. Where the tail wheel mounts to the spring it appears the mount is askew. It looks like the bottom of the mount isn't flat up against the spring where the two surfaces meet. Could there be some sort of dirt, foreign object, or something else between the two that is keeping it from mating up squarely with the spring? Also, it looks like the tire is not parallel to the two sides of the fork. Is the axle bolt crooked or something. The spring looks like it is correct. The problem, from what I can tell in the pictures, appears to be with the tail wheel itself. Maybe you could use a tapered shim to get the mount squared up with the spring.

[Hank Jarrett]

Re: Tailwheel Springs - Continued

I agree with Richard that the wheel looks angled from the spring, which could make control "interesting". I can't make it out in the photo but the middle leaf spring IS NOT supposed to attach at the front bolt! The attached photo is how the springs are mounted according to the factory drawings.

Hank

[PA1195]

Re: Tailwheel Springs - Continued

I'd have an A&P take it apart and examine the spring, clamps, rubber spacers, and tailwheel assembly. That's unless you'd rather do it with oversight. There may be worn parts in need of repair or replacement.

I've had and maintained nine of these Scott tailwheel assemblies and over time they tend to wear. Where the tongue attaches to the spring wears (it's softer than the spring) and can allow the tailwheel to twist relative to the spring's axis both longitudinally and laterally. A U-shaped shim between the tongue and spring can correct that loose interface. The bolt hole in the tongue can wear and be re-bushed. The axle bearings can wear either between the bearing cone and it's race, or between the outer race and wheel rim. That can allow the wheel assembly to shift relative to the fork. There are replaceable wear spacers in the locking assembly between the fork and tongue, and the bolt that attaches the two requires periodic tightening as the spacers and parts wear.

As noted the springs need to be bent correctly and can either straighten longitudinally or twist laterally with use and abuse. Ideally the tailwheel fork to tongue mating surface should be parallel to the ground for best turning performance. As the springs straighten over time or heavy loads carried the tailwheel tends to tip from an ideal position.

With all that rubber one side may have compressed more than the other.

I'd also have an A&P check the longerons and vertical post for correct alignment. It's not that hard to twist a fuselage when the tailwheel hits an abrupt stop in sharp turn, or during a wind event when tied down at the tail spring.

Gary

[Guest]

Re: Tailwheel Springs - Continued

Do you have a spring adapter in the tailwheel to adapt a 1-1/2" spring to your 3200 tailwheel that normally takes a 1-3/4" spring?

I bet that you do not.

Dave

[Guest]

Re: Tailwheel Springs - Continued

The rubber spacers that you have are a bit thick and may also be contributing to the problem

[PA1195]

Re: Tailwheel Springs - Continued

Do you have a spring adapter in the tailwheel to adapt a 1-1/2" spring to your 3200 tailwheel that normally takes a 1-3/4" spring?

I bet that you do not.

Dave

Here's the spacers referred to: http://www.univair.com/categories/ti...selling&page=3

Measure the spring's width, then the width of the mating surface of the tailwheel tongue. If different (like 1/4"-1/2") then a spacer is required. If close, a thin shim can be fabricated shaped similar to the spacers.

Gary

[Robert Lees]

Re: Tailwheel Springs - Continued

Another thing that looks askew is the steering arm attached to the rudder. It looks bent, as if at some point in history, the tailwheel has come off and the whole weight has come to bear on the steering arm. Further, 3 bolts is not the norm.

HTH,
Rob

[Bonanza91K]

Re: Tailwheel Springs - Continued

Darrin,

I looks as though the adapter that goes between the spring and the tailwheel is missing or there is some airframe damage. I'm going to the airport this morning and will compare mine to yours. Spring mount, rudder arm, tailwheel mount, etc. The rudder arms are very weak and I broke two of them off at the stems. Cheap castings. I made a forges aluminum shaft and welded it to the arm and problem fixed.

Jim
F21 - Baumann floats, Trickair skis
Penfield, New York

[dkenney1]

Re: Tailwheel Springs - Continued

Thank you everyone for your comments and advice. I finally got a break in the weather to go fly and all of it had to be from pavement. Whatever is going on with the tailwheel does not affect the handling of the plane adversely at all. Most of landing rollout I don't need to do anything with rudder pedals to stay on centerline with yoke full aft. I put the tail on saw horses and first made sure everything was tight and not rattling around, nothing budged. Took leaf springs off and no elongated holes, threads on bolts good and tighten. Took tailwheel off spring and the spacer/adapter IS there. It looked on one side slightly worn or marks on it and did not fit as tight in tailwheel as I would expect. When assembled on spring it's very tight though. I ordered a new one anyway to be safe. The channel on the tailwheel it fits in looked fine after cleaned it up.

Robert, to your comments, I tried to measure the steering arm and my son came up with taping paper on piece of plywood then tracing the arm on the paper (held the wood against the arm) then he folded the paper in half to see if the drawn arms overlapped and they did perfectly, so they are not bent (not bad for 11 yr old). Also what do you mean that three bolts is unusual? The manual I have shows one large bolt at front of springs that goes into the airframe, and two on either side of springs that hold a bracket that goes around the springs.

Speaking of that bracket it is NOT symmetrical. The bottom is slanted slightly and the tops were screws go through not even by about 1/8". I'm thinking that's the problem and or the bottom of airframe is not level and that's what bent the bracket when tightened down?

This link will take you to an image of similar setup. He calls the bracket I refer to as a clamp. http://www.taylorcraft.org.uk/scott-tailwheel1.jpg The picture shows rubber that wraps around all springs at the clamp, I just have a 1/4" hard rubber at top of spring between airframe and spring and there is some space between sides of leaf spring and clamp/bracket. Also his bracket doesn't look perfect either. The other thing I noticed is the middle spring just aft of the forward bolt is cut or has a gap. Mine is a solid piece for all three springs. Also his middle spring has an elongated hole at the forward portion, mine is same size through all three springs.

Overall the Tcraft is proving to be a good learning experience for me and now my son also. My 84 year old father enjoys it too, so yesterday three generations enjoyed flying and figuring out the trusty old bird, and that's why makes them so great, right?

Thanks,

Darrin

[PA1195]

Re: Tailwheel Springs - Continued

I'm not sure how Taylorcraft designed the assembly, so my comments are generic to that installation. Every tail spring I've had has had solid springs typically three to four. The front holes were typically round, and any elongation of one or more was where it attached to the tailwheel. I assume to allow for differential vertical movement of one or more around the attaching bolt.

That U-clamp is critical whether it's Taylorcraft or other manufacture. They can stretch, bend, crack, and eventually break depending on how much side stress the tailwheel has been subjected to. They can be replaced by new (bought or owner built part) providing the material is strong. I've also had the clamp replaced by two long bolts holding a flat plate under the lower most spring. Any side play between the bolts and springs can be reduced by sliding steel tubing over the bolts. An A&P would know what's best.

I prefer minimal side play between that U-clamp and the tail springs. Rubber spacers are sometimes used, but a tight fitting clamp is best.

Between the upper spring and tail post some manufacturers install a sacrificial aluminum plate, others use tough rubber cut from a tire sidewall or other material that has imbedded threads to help retain its shape.

I've had that spacer you've ordered for the tailwheel tongue wear, and in doing so it can in turn wear the softer aluminum of the tongue. Make sure it fits snugly in the tongue with little potential for movement. Have an A&P look at the assembly if not sure.

While the wheel is off clean, inspect, and lube it. The internal spacers, pin plate, locking mechanism sprag, springs, and wheel bearings should get a good inspection. Again if not sure about component wear have it examined by an A&P.

[Robert Lees]

Re: Tailwheel Springs - Continued

Hi Darrin: my responses to your post:

...Robert, to your comments...Also what do you mean that three bolts is unusual? The manual I have shows one large bolt at front of springs that goes into the airframe, and two on either side of springs that hold a bracket that goes around the springs.

I meant 3 bolts holding the steering arm inside the rudder spar. 2 is normal (3 might indicate some historical damage requiring a 3rd bolt to "tighten things up". See attached photo.

...This link will take you to an image of similar setup.

That's my photo!

...Also his bracket doesn't look perfect either.

OK, so it's bit rusty...no-one's perfect!

... The other thing I noticed is the middle spring just aft of the forward bolt is cut or has a gap. Mine is a solid piece for all three springs. Also his middle spring has an elongated hole at the forward portion, mine is same size through all three springs.

Now we're getting to interesting stuff. The middle leaf spring either needs a slot OR a "gap". That's why the photo that you posted is in two parts, it shows the alternatives.
Otherwise the flexing (and sliding) of the leaf springs will shear the bolt as quick as a Aussie can shear a sheep.



Which reminds me of a joke: Posh English gentleman driving in the Aussie outback stops next to an Aussie Farmer. "I say", he says, "are you shearing that sheep?"
To which the Aussie replies: "No, fook off and find yer own"

[dkenney1]

Re: Tailwheel Springs - Continued

Hi Darrin: my responses to your post:


I meant 3 bolts holding the steering arm inside the rudder spar. 2 is normal (3 might indicate some historical damage requiring a 3rd bolt to "tighten things up". See attached photo. My A&P commented on same thing at pre-purchase inspection and found that in 1958 and later (memory) it was a common retrofit during restoration. Last summer I went to a tailwheel fly in and found 3 other Tcrafts with it. Always good to have a spare nut. I have logbooks to day 1 and nothing on accident, but that doesn't mean someone didn't note an incident, or over the years and 3 restorations parts were not used from something else I suppose.


That's my photo!

OK, so it's bit rusty...no-one's perfect! I tell my wife that often


Now we're getting to interesting stuff. The middle leaf spring either needs a slot OR a "gap". That's why the photo that you posted is in two parts, it shows the alternatives.
Otherwise the flexing (and sliding) of the leaf springs will shear the bolt as quick as a Aussie can shear a sheep.



Which reminds me of a joke: Posh English gentleman driving in the Aussie outback stops next to an Aussie Farmer. "I say", he says, "are you shearing that sheep?"
To which the Aussie replies: "No, fook off and find yer own"

I will leave your sheep alone, your tailwheel however...... LOL

[Mike S]

Re: Tailwheel Springs - Continued

Just to be clear, on the forward mounting point there is meant to be no rubber pad between the leaf springs and the longerons?
I ask because my old leaf spring set had two layers of rubber--about a 1/2"--at that point and another three layers of rubber back at the clamp. Incidentally, my tailwheel was askew just as Darrin's.