Non Commie Tailwheel tire

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Andy Young
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Re: Non Commie Tailwheel tire

Post by Andy Young »

Some spray silicone will help slide that all together.

Or soapy water.

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Re: Non Commie Tailwheel tire

Post by andy »

Soapy water works well. When it dries it leaves a lot of friction between the tube and the rim that resists the tire and tube spinning on the rim when inflation pressure is low.
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Re: Non Commie Tailwheel tire

Post by Spiff »

Well I have about 6 months a 50 hours or so on the new tire. Still works great! I recommend it for sure. No problems and never need to check the tire pressure.

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Re: Non Commie Tailwheel tire

Post by Andy Young »

Same experience here. I’ve also used mine in combination with a tail ski. Works great.

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Re: Non Commie Tailwheel tire

Post by andy »

I ordered one of the solid tires from Larry. Thanks for the info everyone. Has anyone put it on an ABI 3224A tail wheel? I know they are supposed to be exact replacements for the Scott 3200 except for the thicker steering arm with upward bent ends, but it would put my mind at ease if someone has actually put one on a 3224A.
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Re: Non Commie Tailwheel tire

Post by Spiff »

I have been using mine since February and so far it is still perfect. I am very happy with it. Larry just informed me that the price has gone up a bit to $100 which includes shipping. Still a good deal and a great tire. My local glider school is looking at putting one on their Piper Pawnee tow plane.

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Re: Non Commie Tailwheel tire

Post by andy »

I bought one from Larry and a new rim from Airframes Alaska. Mounted the tire on the rim, which wasn't too hard other than lining up the holes correctly. I had to work to press the rim halves together enough to put the washers and nuts on. Airframes Alaska told me that the correct torque value for the rim bolts is 90 inch pounds. They also told me to keep the cardboard gasket between the rim halves in place. Neither of those pieces of information is in the ICA. I asked about the torque value for the axle bolt and they said that there isn't one. I watched some YouTube videos of people replacing the tail wheel tire on a Scott 3200 series and it looks like you just tighten the axle nut until the wheel doesn't spin freely. Then back it off until it does. Anyone have advice on that?
Andy
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Re: Non Commie Tailwheel tire

Post by Kirk »

Andy,
I never heard of cardboard between the wheel halves but I can tell you it is a really good thing. I was out away from home base and had a flat tailwheel tire. The wheel halves were corroded together and would not release. I’ve always planned on using some anti seize compound between the wheel halves next time they are apart.

Mechanic that helped me out said that he has a section of 6” irrigation pipe bolted to his hangar floor. Wheel half fits in there then a second section of pipe is used on the exposed half to flex the two apart.

The axle nut torque you described is how I was taught to do it. Never seen anything in print though. Fun fact learned during the aforementioned event: The lug wrench from a Crown Victoria fits the ABI/Scott 3200 perfectly. It will be a shame when those start to disappear from the courtesy car inventory.

Kirk

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Re: Non Commie Tailwheel tire

Post by asa »

I've only torn apart 5-6 different tailwheels in my life, but for what it's worth, only one has had a fiber/paper gasket thing between the halves. The rest were all metal-on-metal, but not sure if they all started with the gasket piece or not.

As for the axle torque, usually anything using a castle nut and cotter pin should not be torqued, only snugged to the extent to make the system function properly, or torqued then backed off. Castle nuts are a method to have positive retention WITHOUT torque, usually used when a bolt is expected to act as a pivot point. On the axle, you want it tight enough that all bearing surfaces are contacting without slop or play, but loose enough that they move freely - this is called bearing preload. Good well-maintained bearings retain smooth operation even under high loads. However many people drag their tailwheels through hell and back, don't inspect/clean for years, and end up simply loosening the nuts to get them to spin freely rather than addressing the issue.

When you assemble everything, it's best to torque the castle nut down until the wheel won't spin, then back off until smooth operation like ABI says. The point of the initial tightening is to ensure all of the bearings/seals/washers/etc are in contact with each other. Slop is always bad in mechanical systems. This should be the same general process you use on your main wheels as well.

-asa

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Re: Non Commie Tailwheel tire

Post by Kirk »

Good info asa. Thanks

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Re: Non Commie Tailwheel tire

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Regarding adjusting the bearings (torque on axle nut) my opinion differs a bit from what has been discussed so far.

My long-standing technique is to slowly tighten the nut up JUST until there is zero side-to-side play in the wheel/bearings, then BACK the nut OFF just until the cotter pin hole lines up. This will usually yield a slight bit of play in the bearings.
Note that on Scott tailwheels, the nut will often feel like it’s tightening up while there is still significant play in the bearings, due to the distance between the arms of the yoke being greater than the total width at the bearings. You have to keep tightening beyond this point to squeeze the arms down until they contact the bearings on both sides. This can be tricky to judge exactly, so wiggling the wheel side to side while doing this (to feel exactly when the play is eliminated) helps. Some people use shim washers to take up the extra space, but I find that unnecessary.

This is how I was taught to adjust wheel bearings early in my auto mechanic career, decades ago, back when tapered bearings were common in automobile wheel hubs. I had never thought much about why it was done that way, as opposed to putting some pre-load on them, as is done, for example, on the same type of bearing (tapered roller) inside transmissions. Anyway, this discussion prompted me to dig a bit deeper. I found a nice info sheet from Timken (major bearing manufacturer) that discusses proper methods of setting tapered roller bearings for various applications. In a nutshell, it seems that wheel bearings are supposed to have a slight bit of play when cold, so that as they heat up and expand, they have the proper preload, or at least not too much. Other applications (such as transmission shafts) call for a specific preload; perhaps because, being bathed in oil, they don’t heat up and expand as much. Might also have to do with force loading vectors, etc.

I suppose it could be argued that airplane wheel bearings don’t heat up as much as auto wheel bearings, due to them not rolling for as long. If that’s true, then MAYBE they should be set with a bit of preload on airplanes. That said I’ve been doing them my way on airplanes for decades now, and haven’t had any problems.

Here’s an excerpt from the Timken sheet:


“MANUAL BEARING SETTING
Manual methods are frequently used to set bearings on a variety of equipment with low to moderate volume production requirements whereby a non- exact, primarily end play, setting range variation is acceptable. No special tooling, gauges, charts or fixtures are typically required, but assembler’s skill and judgment are necessary. For example, in the case of a conventional truck non-driven wheel with a single adjusting
nut design (Figure 3), manual setting involves tightening the adjusting nut while rotating the wheel until a slight bind is felt. Then the adjusting nut is backed off 1/6 to 1/4 turn to the nearest locking hole or sufficiently to allow the wheel to rotate freely with some minimal end play. The adjusting nut is then locked in this position. Skill and judgment are required to determine when the wheel binds slightly in rotation. The more complicated the equipment and/or the larger and heavier it is, the greater degree of skill and judgment required.”

Here’s a link to the whole 20-page sheet:

https://www.timken.com/wp-content/uploa ... hure-1.pdf

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Re: Non Commie Tailwheel tire

Post by andy »

I finally installed the solid tire from Larry on the new rim from Airframes Alaska and did a test taxi/flight. Everything worked great.Since I installed the ABI-3224A in 2008 there's always been a fair amount of slack in my compression springs with the associated loss of steering authority. However, the solid tire steers slightly better since it doesn't squash down under the weight of the tail as much. No shimmy on taxi or landing.

I noticed that the bushings on the old ABI 3224A wheel were more compressed into the rim (or shorter) than the ones on the new rim. There's about 1/4" of space between the bushing flange and the rim on each side of the new rim. At first I thought the bushings weren't seated properly but they are. Did Airframes Alaska change the bushings to give the tire more space from the fork arms?
Image

Thanks for all of the advice on the axle nut torque. It was pretty straightforward to tighten it until the wheel would no longer spin freely then back it off until it would and align the castle nut with the cotter pin hole. When you install the axle, you have to make sure that the cotter pin hole is visible and accessible from the top. Otherwise, it's too hard to install the cotter pin and you will have to back the axle out and rotate it and re-insert it since the bolt will not rotate with the keeper washer in place against one of the axle head's edges. A small x is stamped on the axle head where the keeper washer is supposed to be to help you align it right. I checked to make sure that the wheel was snug against the bearings and that the wheel would not move sideways on the bushings.

When I jacked the tail up, I found that the main attachment bolt holding the tail wheel to the leaf spring was a bit loose. I'm going to check this once a month from now on instead of waiting for the annual. The more beating your tail wheel takes, the more often this bolt should be checked.

I'm definitely ordering another one of the solid tires from Larry.
Andy
1986 MX7-180

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