Main Tailspring Dilema

How to keep the Cessna 170 flying and airworthy.

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Bruce Fenstermacher
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Re: Main Tailspring Dilema

Post by Bruce Fenstermacher »

gahorn wrote:The bushing is 7/16 ID and 1/2 OD, therefore cannot penetrate the spring, and (depending on bolt and adaptor) may need the 816 washer. Not all,..but most.
Yes I understand that now. But will the standard AN960-716 with an outside diameter somewhere in the neighborhood of .75" verses the outside diameter of the 816 of .875, be enough claiming area. Certainly the 3/4" diameter washer won't be immediately pulled through the 1/2" hole but 7/8" would be better.
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GAHorn
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Re: Main Tailspring Dilema

Post by GAHorn »

N9149A wrote:...Yes I understand that now. But will the standard AN960-716 with an outside diameter somewhere in the neighborhood of .75" verses the outside diameter of the 816 of .875, be enough claiming area. Certainly the 3/4" diameter washer won't be immediately pulled through the 1/2" hole but 7/8" would be better.
It's what is specified by Cessna. The 816 washer accomodates the bolt/bushing ID, not OD (neither will be "pulled thru" the hole...but if you are worried about "spreading the wealth"...then you might wish to consider a AN970 (wide-area type) type in lieu of a AN960 washer.)
'53 B-model N146YS SN:25713
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Sask170b
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Re: Main Tailspring Dilema

Post by Sask170b »

Good Evening ..I have a question as I'm running into the same issue. I am installing a new spring stack using a Air Repair Inc. provided tie down bolt and bushing to attach the Scott 3200 Tailwheel head to the main spring with the spacer. I installed the bushing first in the 3200 he'd by gently tapping into place, placed the spacer which slid over the 1/2 O.D. bushing and went to affix to the main spring only to find it would not mesh with the main spring because the bushing was of a larger diameter than the main spring drilled hole. I was a bit disgruntled as I worked for a bit to get the spring stack in place and clamp and bolt all other parts in place. I have disassembled all parts and think my only option is to drill out the main spring to 1/2 I.D. to accommodate the bushing and the 7/16 eyebolt. It seems to me that it would make sense to have the bushing continue through all three parts i.e.: Tailwheel head, spacer, and main spring to prevent bolt shear? You can see from the pictures that there is enough bushing length to extend into the main spring if it was drilled out? Can I get some feedback. Will there be enough material at the end of the main spring if I have it drilled 1/2 I.D. Thanks Mike
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c170b53
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Re: Main Tailspring Dilema

Post by c170b53 »

I'll look at mine Mike, but I'm back to work for 4 days tomorrow, so it will be awhile before I report back. I replacing the control horn on my rudder and shimmed the rudder bearing blocks today. Spent most of the day on my hands and knees looking for dropped bolts. Getting the rudder hinge points right might be one of worst jobs on this plane. By day's end the rudder was all hooked up, but it took all day.
I also replaced my main spring (remembering to radius the end of the spring above the main spring) this spring :D and I don't recall anything special about the bolt in question which attaches the tail wheel to the spring. So having read this entire post a few times over, I think Bruce figured it out awhile back(help me out here Bruce :) ). I know I've never drilled out the main spring to accept a .500 bolt and I'd advise against it. So I'm guessing possibly there two types of yokes for the 3200. One uses a longer bushing than the other with the longer bushing gap above the yoke and a washer(s) are used to take up the gap. My 3200 is not like that, a 7/16 bolt goes through the casting, through the spring adapter and then through the spring.
This bolt does take a pounding, and although I'd like to get a bolt that has tie down provisions, I'll stick to the basic bolt.
I find that this bolt will neck after a while which will loosen the grip on the spring and it will show up as relative movement between the parts. At this point I'd rather just replace the bolt, as by the time you discover the movement, likely the bolt's shank will have been scored, and its strength compromised.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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Bruce Fenstermacher
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Re: Main Tailspring Dilema

Post by Bruce Fenstermacher »

I've not ever seen a bushing protrude past the casting of the 3200 tail wheel. And so I'd cut off the bushing flush, not drill the spring. Wouldn't hurt if the bushing was long enough to hold the spacer but it is not necessary and contrary to what I'd be expecting and will make no difference in performance.

Your bolt will still come loose and the 3200 swivel slightly on the main spring just like everyone else, as the 3200 vs spacer vs spring is not a precision fit.

A bonus of the L-19 ring bolt is you can easily see the bolt has rotated by the rings misplacement from the direction you installed it.
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Re: Main Tailspring Dilema

Post by Bruce Fenstermacher »

Revisiting this entire thread, and review and refresher of the IPC, yes indeed the IPC calls for an AN960-816 under the head of the bolt which will go around the bushing should it protrude out the top of the 3200 casting. And so from the evidence in print I'd say it most correct if the bushing is left long it be out the top of the casting and not longer than the thickness of a AN960-816

I still never recall seeing a bushing that wasn't flush top and bottom and so that is how I'd have cut it before I looked at the IPC. :roll:
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gfeher
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Re: Main Tailspring Dilema

Post by gfeher »

Bruce's last comment about what the IPC shows is consistant with my recollection from when I changed my main leaf spring two years ago. Sask170b, your bottom photo shows that your bushing is flush with the top of the casting, when it should stick out from the top the thickness of the washer that goes under the bolt head (when using the stock bolt). In other words, that washer goes around the bushing at the top. So, the bushing sticks out the top of the casting the thickness of the washer and out the bottom the thickness of the spacer. When the bushing is positioned like that I think you will see that when the spacer is on the bushing, the bushing is flush with the bottom of the spacer and the main leaf spring does not need to be drilled. In any event, do not drill the leaf spring, it is spring steel. If you are going to cut anything (which you shouldn't need to) trim the bushing.
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
Sask170b
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Re: Main Tailspring Dilema

Post by Sask170b »

Jim, Bruce and Gene ..Thank You for your feedback much appreciated. (Mike)
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Re: Main Tailspring Dilema

Post by c170b53 »

Sorry Bruce, I guess George figured this out awhile ago :D
Jim McIntosh..
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GAHorn
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Re: Main Tailspring Dilema

Post by GAHorn »

Been out on a long trip and just catching up .... Keep in mind the L-19 eyebolt has a longer shank than the original AN bolt specified for this installation.
The many complaints about it loosening up are partly because this greater length is not accommodated for with an additional washer which is needed to allow the nut to torque properly. Adding an additional washer or two will allow the bolt to be properly torqued and should relieve the "loose" bolt complaints.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
Sask170b
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Re: Main Tailspring Dilema

Post by Sask170b »

Thank You All for the feedback. I did get the bushing sleeve pressed up into the head casting so that it extended above the casting the width of the 1/2 inch I.D. washer. This worked and I mounted the tailwheel assembly utilizing the L-19 Eyebolt and torqued ... however ran into another issue regarding Tailwheel centring that I will have to ask advice on in a separate post. Mike .
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n2582d
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Re: Main Tailspring Dilema

Post by n2582d »

I recently came across this website which has a better copy of the L-19 IPC than Air Repair. It also has the L-19 Maintenance Manual. (Some of this might be worth adding to our maintenance library given the similarities between the L-19 and the 170). Before you go and figure out how to attach rocket launchers to your wings take a look at chapter 4, section VI. On page 4-60 it says if this bushing that the eyebolt goes through "is not flush with bracket, spot face or grind to make flush and coat with primer." For the L-19 with the higher gross wt. they give the following caution: "Do not substitute AN960 type washers for washers, p/n AN122585 or 0642162-1 ... Use washer p/n 0642162-1, as required, under washer (14) for bolt grip." I'm guessing the AN122585 or 06642162-1 are hardened steel washers. They also call for torquing the eyebolt anywhere between 600-700 inch-pounds, depending on whether or not it has 2800# setup.
Gary
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