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Thread: PA-18-95 leaf spring sprung

  1. #1

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    PA-18-95 leaf spring sprung

    Seeking options:

    Took off the Maule tailwheel and installed a Scott 3200. Added a couple pounds but a much better tailwheel IMO....
    Current setup is a three leaf spring with a single bolt hole for the tailwheel attach...1-1/4" width.

    As you can see from the side view, it looks like my leaf springs are sprung! The tailwheel is only about 3" form the bottom of the rudder and the negative angle is a bit too much. Crude measurement with an iPhone app puts it about 12 degrees...I seem to remember between 0 and 5 degrees is about right?!?! I just installed it today and haven't even taxied it around yet but I'm not expecting good performance as is.

    Is there a different part number set for the maule vs. the scott setup??

    I've heard of re-arching these things and not opposed to that, although its hard to determine just how much it needs...
    From my "minimal" research here, I guess on can cold bend these things back into shape which, to me ,seems like an easy way...

    I could buy a new set from univair or ABI but looks like $450ish for that option...not ideal

    I did notice a new Titanium single leaf option from ABI that looks promising, though outlandishly priced...would be cool though. prob save a little weight back there and simplify things, but not worth 2 grand.

    Also seems like others are moving away from the traditional spring setup in favor of the latest tailwheel suspension systems that I'm not all that familiar with...maybe there's a surplus of good used spring sets out there that somebody would part with...though, I'm guessing that they are mostly 1-1/2" setups. Could use those I guess, but complicating the issue with other parts and more weight for my 90 horse cub.

    Thanks for any wisdom!

    Click image for larger version. 

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  2. #2
    fancypants's Avatar
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    Here's an image of two sets of brand new springs placed on top of a flatbed scanner. The Univair set of 4 is on the left, and the ABI set of 3 is on the right. ABI was from before the Airframes purchase, so I don't know if they've got anything comparable now. Interesting to note the difference in arch between the two.

    https://i.imgur.com/Uatw5y0.png

    I'm running the Univair springs on my PA-18-95. I rarely notice any shimmy. Only when three-pointing with a larger person in the back seat. There was a lot of shimmy before I changed out the old springs for new. Haven't bothered re-arching the old ones yet.

  3. #3

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    I wonder if a few washers under the tailpost might fix it until your next annual? If there is a leaf spring shop near you that makes truck springs, they should be able to rearch the spring for about $50.

  4. #4
    RaisedByWolves's Avatar
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    Quote Originally Posted by supercub1999 View Post
    I wonder if a few washers under the tailpost might fix it until your next annual? If there is a leaf spring shop near you that makes truck springs, they should be able to rearch the spring for about $50.
    Phenolic block under the pad where the two bolts go will help for the time being


    Sent from my iPhone using Tapatalk

  5. #5
    Steve Pierce's Avatar
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    I would install the ABW tail spring and forget about it. You might get by with the Univair spring for many years but they do seem to loose their arch over a few years depending on your tail weight. You can also re-arch your 1 1/4" spring which will work fine but they do twist more that the ABW or Univair Pawnee spring which are wider.
    Steve Pierce

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  6. #6
    KJC's Avatar
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    Throw that old one in recycling or the trash. You want this:
    Click image for larger version. 

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    They work really well. Replace the pad and bolts while you at it and grease in between the springs before you assemble them. They move and the grease helps prevent from rusting. The spacer in the Tailwheel head gets removed. You’ll be much happier.
    PA-12 N418BS

  7. #7
    fancypants's Avatar
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    For posterity, here's some info I got from Univair a few years back:

    What I found is that the three leaf spring set-up was used on Cubs serial number 1 – 1706. Serial numbers 1707 and up use a four leaf set-up.

    The three leaf stack uses one p/n 12567-4, one p/n 10999-3 and one p/n 10999-5. And it uses the 30531-00 bracket.

    The four leaf stack uses two p/n 12567-4, one p/n 10999-3 and one p/n 10999-5, plus the 30531-02 bracket, which is one inch deep.
    Note that you've got the three leaf stack on there right now. If you go to the 4 leaf Univair stack or the Airframes/ABI 3 leaf, you'll need the deeper 30531-02 bracket. Which is now apparently selling for $100. My junk pile might soon be a retirement pile.

  8. #8
    Kodiakmack's Avatar
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    I'm on board with what others are saying. I had a shimmy, ordered the univair springs and they came out of the box with insufficient arch to appreciably change the castor angle. Put the ABI on with their bracket and I now have great castor and no shimmy for a couple years. Don't hesitate to spend $$ back there.
    HAVE FUN. DON'T DIE.

  9. #9

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    I bet they dont charge you 30 bucks to bend all of your springs, mine has lasted 5 years now on re arch. Here is a video of a guy arching large truck springs with a exhaust pipe bending press at a muffler shop
    https://m.youtube.com/watch?v=HImEhw1UUoQ

    If you really want a new spring, I had a quote of 80 bucks to make a 3 leaf spring from scratch out of 1 and 3/4 inch flat spring, that was the shop that re-arched my spring for $20. I tried the original one they re-arched first and it fixed my earthquake on tail touch problem, so I saved 60 bucks.
    Last edited by supercub1999; 09-11-2022 at 10:45 PM.

  10. #10
    cubdriver2's Avatar
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    Switched to a single shock T3 on my little SC 5 years ago and love it. Never going back to a spring

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  11. #11

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    Quote Originally Posted by cubdriver2 View Post
    Switched to a single shock T3 on my little SC 5 years ago and love it. Never going back to a spring

    Glenn

    That looks like a good tailwheel, but doesnt it raise the tail about 6 inches higher than the stock leaf spring and scott 3200 setup. I cant stand blowing through climb speed on the takeoff roll trying to get the plane off the ground and cant because the tail is too high.
    Likes RaisedByWolves, hotrod180, DENNY liked this post

  12. #12

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    Google search tailwheel spring arch and found this, I would not bend too much the first time, might not need as much as the guy here did. Walk into a spring shop and ask them if they will put a little more arch in your spring, they will give it back to you in 5 minutes with a nice new arch and probably say no charge or give me 10 bucks. Mine is still going strong now and its been years since I rearched it


    Quote Originally Posted by jeremygerhold View Post
    Ok fellas here's my update looked at my logbooks looks like they replaced the tailwheel spring 3 years ago with a new univair one. So what I did was bend it down 1 1/2" down and went and flew the pacer. The plane did great no shimmy.
    Last edited by supercub1999; 09-12-2022 at 10:26 AM.

  13. #13
    cubdriver2's Avatar
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    Quote Originally Posted by supercub1999 View Post
    That looks like a good tailwheel, but doesnt it raise the tail about 6 inches higher than the stock leaf spring and scott 3200 setup. I cant stand blowing through climb speed on the takeoff roll trying to get the plane off the ground and cant because the tail is too high.
    Raised mine about 3" unloaded but will compress over 4" if you over rotate. 3200 is overkill and too tall on these planes that's why I run an API 6131 or Lang or Scott 2000

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  14. #14

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    I run a 4 leaf Univair with my big tire in the summer and a 3 leaf Univar with my Scott 3200 in the Winter/Spring. When I was doing a lot of tailwheel first landings I was able to screw up both in only one year. It only takes about 20 min with a press to re arch them. I even did it once with just a vice and very large crescent wrench. Now I protect my tailwheel only have to re arch every 3 years or so. I have a template I made off a new Airframes spring and use that when I re arch the springs. If you have the time and a simple press with a 4 -5 inch steel pipe it is just time. Having said that just buying a new one and be done with it is not a bad plan. Airframes used to be out the front of my hanger I remember years ago walking over to see them inspecting the arch of every spring that came in from a vender. They had quality control issues and did not want to send out anything that was not right. DENNY
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  15. #15

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    Thanks for the info guys

    I ended up removing them and cold bending a little more arch in each spring using a vise, crescent wrench and a cheater. Turns out it wasn't very difficult to bend them...which is probably an indication of wat will happen later, but for now its sitting up correctly and I'll keep an eye on it. I'm guessing I'll end up with the new ABW springs at some point.

    Aaron
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