Which tail spring do i need to get?

How to keep the Cessna 170 flying and airworthy.

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Which tail spring do i need to get?

Postby suntiet » Sat May 12, 2018 7:45 pm

So i have done as much research as i can, It is a 48 170 rag-wing. There is only four leafs in the tail spring. Do i need the spring for a B model? I am installing a baby bush-wheel and thought it would be a good idea to replace the tail spring and i just don't want to order the wrong item.

https://www.aircraftspruce.com/catalog/ ... 0twspr.php

Seam that this would be the correct one but it says it is 2 inches wide and mine is only 1 1/2?

thanks for any and all help.
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Re: Which tail spring do i need to get?

Postby Bruce Fenstermacher » Sat May 12, 2018 9:09 pm

Are you asking what spring of the 5 you should have you are missing? I'd say the top spring part 0442107

Screen Shot 2018-05-12 at 5.03.53 PM.png
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Univair list it here: http://www.univair.com/categories/cessn ... -gear.html

Spruce may also have it if you ask as they resell Univair parts.
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Re: Which tail spring do i need to get?

Postby c170b53 » Sat May 12, 2018 9:14 pm

I have a new one if that’s the one you need at a 170 assn donation price
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Re: Which tail spring do i need to get?

Postby suntiet » Sat May 12, 2018 9:53 pm

PM Sent
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Re: Which tail spring do i need to get?

Postby suntiet » Mon May 14, 2018 4:26 pm

here are some better pictures

I can't tell if the top shorter spring is there and just inside and i cant see it or what. If i get the five spring set from Spruce it should work?
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Re: Which tail spring do i need to get?

Postby gahorn » Mon May 14, 2018 4:33 pm

Just to clarify this a bit...
The ragwing models with the steel "box" tailwheel spring bracket originally was equipped with 5 springs, PNs from bottom to top are 0542106, 0542105, 0542108-2 0542109-2, and 0442107. (The 170A with the same box bracket replaced that top spring with a hard-rubber spacer. It's possible you have had your assy modified to match the 170A installation. If so, you now have a choice as to follow the later 170A installation or return to the original 170 method. I'd keep the later one, personally.)

The 170B did away with the steel "box" bracket and used a larger aluminum "alligator mouth" bracket. This was to avoid the cracking which is more common to the smaller box bracket.

Spruce, as a reseller of the springs PMA'd by Univair, offers the bottom MAINspring which bolts to the tailwheel assy as an individual part..... OR...alternatively they sell the entire STACK of springs. I can not recommend anyone replacing their entire stack unless there's obvious damage or corrosion. Those upper springs will usually outlast the pyramids... It is the bottom MAINspring, PN 0542106 which I recommend replacing every 500 hours/cycles as it is the spring which commonly breaks after around 700 hrs (by a survey taken years ago.)

The spring PN0542105 which is the one immediately above the MAINspring will have a sharp edge which will rub a stress-riser onto the top of the MAINspring causing it to fail at that point. (I consider it a good idea to "radius" the lower, trailing edge of that particular spring 0542105 with a file and emery to reduce that possibility.) The result will be a tailwheel assembly which, captured by the steering chains/springs, will flail around and beat the rudder to death. You can see this many times evidenced on the flight-line by the number of lower rudders which have damage and/or repairs to that area.

It is far less expensive to replace that $100 MAINspring, PN 0542106 every 500 hours than to repair that rudder.
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Re: Which tail spring do i need to get?

Postby suntiet » Tue May 15, 2018 12:24 am

Has anyone ever heard of a "heavy duty" tail spring?

The local parts people said they have one of those in stock, about $30 more than the one spruce lists, although for Alaska that about right for the same part?
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Re: Which tail spring do i need to get?

Postby gahorn » Tue May 15, 2018 4:04 am

It's probably an L19 spring, which is slightly thicker than one for a 170. I'm going to recommend you forget that idea. It will create an installation problem because of it's thicker dimension and it doesn't do a thing for you other than be too stiff for the 170 weights. IMO.

(I've go two of them sent to me by Members who wanted me to see how an L19 spring breaks just the same as the correct 170 part.)
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Re: Which tail spring do i need to get?

Postby n2582d » Tue May 15, 2018 4:49 am

The Alaska guys seem to be unanimous in their recommendation for the heavier duty L-19 tailspring. Assuming you could get it to fit, my concern would be how your early box style bracket would handle the L-19 spring. With a heavier spring more of the pounding the tailwheel experiences would be transmitted to the tailcone structure. Maybe your plan to install the Baby Bushwheel will help in this regard. Something on your "to do list" might be a conversion to the later style "fish mouth" bracket as outlined in SK70A52-4. The second page there has a good illustration of how the 170A tailspring - and maybe yours??? - is set up. For what it's worth, my new main tail spring from Aircraft Spruce measures .312" thick while my old L-19 spring measures .350" thick.
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Re: Which tail spring do i need to get?

Postby suntiet » Fri May 25, 2018 6:04 pm

Got everything install, put a whole new set of standard springs and the new tail wheel setup, Night and day difference in ground handling.

Changing to the new style tail wheel bracket is on my to do list. Any idea where to get the kit and/or parts?

Thanks for all the help.
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Re: Which tail spring do i need to get?

Postby gahorn » Wed May 30, 2018 9:09 am

suntiet wrote:Got everything install, put a whole new set of standard springs and the new tail wheel setup, Night and day difference in ground handling.

Changing to the new style tail wheel bracket is on my to do list. Any idea where to get the kit and/or parts?

Thanks for all the help.


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'53 B-model N146YS SN:25713
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