Main Tailspring Dilema

How to keep the Cessna 170 flying and airworthy.

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j3pup
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Main Tailspring Dilema

Post by j3pup »

I recently purchased a new main tailspring from Spruce part#0542106 as the IPC page 54 shows that serials 20806 and up should get part 0542106. (My Serial # is 20949) When laying my springs side by side the new one is too skinny and the old one was notched out in places. Also the channel that receives the spring on the Scott 3200 tailwheel is wider than the new spring. Does anybody know why the spruce spring wouldn't be as wide? Was this an L-19 tailspring on my machine? Do they have the wrong tailwheel on it? Picture attached...
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Tailwheel%20Bracket%20IPC%20pg%2054.JPG
IMG_0276.JPG
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GAHorn
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Re: Main Tailspring Dilema

Post by GAHorn »

The Spruce spring should be exactly the same width as all the springs above it.

Someone has "jury-rigged" your old spring to fit. (It was not the correct part and you're danged-lucky it hadn't snapped on you where it had been machined.)

The tailwheel in the illustraton is the Scott 2000 tailwheel. If you look further in your IPC you'll see where the 3200 is also illustrated. It makes no difference which tailwheel you have...they both use the same (Spruce) spring. (Spruce's spring is actually a Univair PMA'd spring...exact copy of the original Cessna spring.)

In other words you have the correct spring. It's probable that PN 0442011-3, spacer, item # 4, Fig 94. {Pg 154) is what you need to mate the Scott 3200 to the spring. When you look at that Pg 154 illustration l think you'll see what will clear this up for you. (The 3200 tailwheel fits wider springs, which apparently someone installed and then modified to fit the rest of your tailwheel brackets/springs. They should have kept the original spring (or installed a Spruce spring such as you have) and installed a spacer when they converted from the 2000 to the 3200 tailwheel.)
click to ENLARGE
click to ENLARGE
'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. ;)
j3pup
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Re: Main Tailspring Dilema

Post by j3pup »

This all makes complete sense now. FYI the spacer for adaption to 1.5" runs for $35 bux at spruce, where if you are converting to 1.25" it is $9 bux. (makes no sense to me) One more question the picture shows the spacer with the prongs facing down, I would think they would go underneath the spring facing up no?
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GAHorn
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Re: Main Tailspring Dilema

Post by GAHorn »

No. The spacer fits up into, and reduces the grip of the tailwheel casting. (It fits over/around the spring.)

While you're at it... call Air Repair, Inc in Cleveland MS and order PN 0642105 tailwheel eyebolt to replace the AN 7-20A bolt that holds the tailwheel on. That way you'll have a tail tie-down ring.
Ask Pete Jones if he also sells that spacer. I'll bet he gives you a nice discount since you're now a 170 Assocn' member.
'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. ;)
j3pup
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Re: Main Tailspring Dilema

Post by j3pup »

Will do, thanks so much!

Randy
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GAHorn
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Re: Main Tailspring Dilema

Post by GAHorn »

Be careful Randy. Check to see if you also need item #3, bushing, PN 0442011-2. Looking at your pic of your old spring, whoever was manufacturing parts to their own design may have not realized they also needed that bushing to neck the tailwheel casting down to 7/16" to fit the bolt.
'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. ;)
j3pup
Posts: 190
Joined: Sun Nov 01, 2009 11:53 pm

Re: Main Tailspring Dilema

Post by j3pup »

Will do, I have been pulling all kinds of non AC bolts and screws out of this airplane all over. A previous owner must have owned a hardware store. The good news is when we get done with it, I will have most every bolt replaced and know what I have.
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n2582d
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Re: Main Tailspring Dilema

Post by n2582d »

I bought the tiedown eyebolt from Air Repair. Then upon trying to install it I discovered that someone had previously installed a 1/2" bolt instead of the 7/16" bolt and bushing (#3 pictured below) which is called for in the IPC .
Tailwheel bushing.jpg
So I ordered the bushing pictured below from Air Repair.
Bushing p/n 0442011-2
Bushing p/n 0442011-2
Now I assumed the bushing would be long enough to fit through the leaf spring, spacer (p/n 0442011-3), and the Scott tailwheel bracket assy. (Scott p/n 3216/ Cessna p/n 0442010-6). But it is not long enough to fit through all three items, only the spacer and tailwheel bracket. So I assume that my leaf spring hole diameter is incorrect at 1/2". Is the correct diameter for this hole 7/16"? The other question I have concerns the washers. It appears that the top washer(s) (7A in the IPC) also fits around the bushing as it is 1/2" I.D. Here the diagram shows one washer on top but calls for two. And then on the bottom of the bolt it depicts two 7/16" washers (item # 7) but calls for 12 in the text. What's up with that?
Last edited by n2582d on Mon Jul 11, 2016 6:24 pm, edited 2 times in total.
Gary
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GAHorn
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Re: Main Tailspring Dilema

Post by GAHorn »

As discussed elsewhere, the IPC is not an approved document and sometimes has errors.
The AN7 bolt is INDEED a 7/16" bolt. The O.D. of the bushing is 1/2", and that is why one of the washers depicted is an AN960-810, to accomodate excess length of the bushing. (The bolt should clamp the tailwheel bracket to the leafspring...not only the bushing.) There are only two AN960-716 washers (on the bolt being discussed), and those are used to adjust for length of the bolt.
'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. ;)
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n2582d
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Re: Main Tailspring Dilema

Post by n2582d »

George,
I guess I didn't make myself clear. My main question has to do with the length of the bushing. Should it be long enough to go through the bracket assembly, spacer, and the spring or just the bracket and spacer? My bushing is not long enough to go through all three items and my guess is that some previous mechanic drilled out the spring to accommodate an AN8 bolt. Could you (or someone) tell me what diameter the hole is in the aft end of the tailwheel leaf spring--7/16" or 1/2"? Either the new bushing I bought is too short or else--and I'm guessing this is my problem--the spring's aft hole has been drilled from the original 7/16" dia. to 1/2" diameter.
Gary
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DaveF
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Re: Main Tailspring Dilema

Post by DaveF »

Gary,

I found the exact same thing when I replaced my main spring leaf. The new spring had a 7/16" hole that the existing 1/2" bolt wouldn't fit. There was no bushing in the bracket and the old spring had been drilled out to 1/2". The bolt should be an AN7, not an AN8.

Dave
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n2582d
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Re: Main Tailspring Dilema

Post by n2582d »

Thanks Dave. Time to go shopping for a tailspring.
Gary
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Bruce Fenstermacher
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Re: Main Tailspring Dilema

Post by Bruce Fenstermacher »

How timely. Taxiing for departure from my home base grass strip to relocate to my home public airport for some maintenance, the bolt that holds the tail wheel to the sprint broke.

I was able to scrounge about with the local mechanics to come up with a fresh AN-7-20A, some AN960-716 washers and a new castle nut. I'd noticed the new washers were smaller than the one under the bolt head and for a split second I thought I should make sure the new standard AN washers I was using were bigger than the bushing in the tail wheel and just then with a big buzzing one of those big green head horse flies landed on me requiring a swat, and that thought was gone.

So here I am feeling really good that that bolt didn't last for one more takeoff which meant that I was going slow enough and on grass to not cause additional damage with the Scott 3200 flailing about at the end of the chains. And how I got that fixed and even had enough time to calmly, and with out breaking a sweet, replace both rudder pedal return springs with new. And I didn't even disconnect the rudder cables in doing so.

But now I've got to go back tomorrow and jack up and remove the tail wheel and replace that nice new AN960-716 washer with the nasty old AN960-816 I luckily still have in my pocket. :roll:
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Bruce Fenstermacher
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Re: Main Tailspring Dilema

Post by Bruce Fenstermacher »

Now I'm rethinking this. Do all Scott 3200 have that 1/2 bushing? I think mine did but it didn't stick out the top and would not require a AN960-816 that would fit around it. Wouldn't it then be OK to use a AN960-716 which fits the AN7 bolt?

Actually I can't remember any 3200 brackets with a bushing sticking out the top. :?
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GAHorn
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Re: Main Tailspring Dilema

Post by GAHorn »

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.
'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. ;)
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