Oversize tailwheels

[Bud Hartman]

Has anyone had any difficulty after installing an Alaska Bush Tailwheel. This is going on a PA18 with 26" tires.

 

[DW]

Buy one you won't be sorry.

 

[OLDCROWE]

I did it (with appropriate supervision) and my lack of mechanical skills is legendary!

 

[mvivion]

There is a good possibility of tailwheel shimmy on pavement if the tail spring isn't set up about right. You want the pivot pin on the tailwheel pretty much vertical when the tail is on the ground.

Remember that tail springs flex with loads as well.

With a well set up tailwheel, you shouldn't have any problems, but shimmy can be an issue with big tailwheel tires.

MTV

 

[72A]

I found that by tightening my springs by 1 link on each side it stopped the shimmy I had. I love my big tail wheel.

John Pex
72A
Chugiak AK

 

[hottshot]

There is a good possibility of tailwheel shimmy on pavement if the tail spring isn't set up about right. You want the pivot pin on the tailwheel pretty much vertical when the tail is on the ground.

Remember that tail springs flex with loads as well.

With a well set up tailwheel, you shouldn't have any problems, but shimmy can be an issue with big tailwheel tires.

MTV

Mike--

You want the tailwheel to have a 5 to 7 degree positive caster angle with the tailwheel on the ground so when you load you DO NOT go past vertical with the pivot bolt see below

http://akbushwheel.com/TailwheelTechnicalInfo.html

Also a very good artical on Steve's web page (Where I stole the Photo)


Also we just finished the PMA on oue new Husky Tail Spring and hope to add the Cub to the approval in the future as it will help the Cubs as much as it has helped the Husky

http://akbushwheel.com/HuskyTailspring.html

 

[Steve Pierce]

I think the tail springs Wup is referring to will make Pawnee springs obsolete. I would have tried it this weekend but the two bolt bracket that attaches the spring to the rudder post is different on the Piper than the Husky parts I had. All my Piper brackets are for the 1 1/4" tail spring. Anybody know what a Pawnee spring weighs?

 

[mvivion]

Wup,

You are correct. What I was trying to say was the vertical axis should be set up so it never goes past vertical. There I go communicating again.

Tailwheel shimmy can be a deeply moving religious experience, and is to be avoided like the plague if at all possible.

My point was simply to get someone who knows their stuff to set up the tailwheel properly.

I like the idea of the new spring set. My 170 has an L-19 main leaf substituted for the Cessna Main leaf, and the little guy left off. It works SOOOO much better than any C-170 spring and steering setup that it's not even funny.

Good spring geometry is really important, and often overlooked.

MTV

 

[16-bravo]

what kind of difficulty are you referring to? I run the baby bush in the summer, and absolutely love it. It does steer a little harder, and is noticeable as far as weight goes, but I would not trade it for anything in the soft dirt, or the ruff stuff. And as far as the extra weight goes, it does allow you to stand on your brakes a little more. As far as the steering goes, I am thinking about running it with no springs(free spooling). If anyone has any ideas on that, please let me know.

 

[Icarus]

Last Pawnee 4 leaf springs I weighed were 6.5 lbs according to my notes. Like Mike V said geometry is important to flat an angle & they may allow the tailwheel / springs to smack the bottom of the rudder to much & they stiffen the tail. Also beware rebending them at the local spring shop they become brittle and Break!!

 

[On Patrol]

Steve,
I twas my understanding that the Pawnee spring with the added weight aft was a positive due to the PA18 forward CG. That is what I was told when I did it so it makes me and Excerpt on this post
John

 

[DW]

I have re-bent springs in the past and never had one brake "yet" but they do lose the arch faster after a re-bend. My 2 cents is if they're weak and losing arch throw them away and buy new ---they don't cost that much.

DW

 

[supilot]

Does anyone have the part # or know where to find the two bolt bracket that attaches the Pawnee leaf spring to the rudder post on the Supercub? Thanks

 

[Icarus]

The only part number I have seen is 5/16th plate from Stoddard's

 

[spinner2]

I have a ABI 3200B (baby Bushwheel) on a Pawnee spring. I opened the two bolt holes in the tailpost that retain the spring to accommodate the wider Pawnee spring and -5 bolts. For the bottom plate I used 1/8" thickness 4140 that is 1" wide and long enough for matching holes for the -5 bolts. It hasn't loosened.

I really like the tail wheel on the rough stuff when taxiing. My springs and chains are attached but loose enough that I don't get rudder feedback. Steering while taxiing is often with brakes.

I never have had a shimmy issue while taxiing, but that is always at very slow speeds. On landing the tail doesn't come down until nearly stopped and on takeoff it isn't long before it is up - so the main issue, as I see it, is how rough is the ground you'll be taxiing on? If it is very rough you'll appreciate the big tire on back.

 

[Icarus]

That is normal having to ream out the fuse tail pad holes to 5/16 th inch I believe thats why Univair / Stoddards lists the part as 5/16th plate. If you use Wipaires 2000 lb kit you have to ream out the plate or use Univair's part I think they are bout $12

 

[cubscout]

The Piper p.n. for the shallow-u-"Clamp assembly, Tailwheel Spring for the two-hole tailspring attach is 64487-00; the matching "Pad, tailwheel spring" that goes between the top leaf and the sternpost is 64086-00.

Univair normally has these in $tock.

And let us know how she turns out, eh?

Thanks. cubscout

 

[supilot]

thanks for the replies. i had a 5/16" plate/bracket fabricated at a metal shop, but decided i wanted a certified part. aircraft spruce didn't know what a PA25 was. i talked to stoddards, whom were helpful, but they sell exactly what i had made...still not certified. i called univair and they were helpful. they had the certified bracket buried in their warehouse somewhere...they had to do some digging, but found one i guess.

i never had shimmy issues until i was at gross weight with my stock leaf spring. once unloaded it won't shimmy.

 

[behindpropellers]

There is a good possibility of tailwheel shimmy on pavement if the tail spring isn't set up about right. You want the pivot pin on the tailwheel pretty much vertical when the tail is on the ground.

Remember that tail springs flex with loads as well.

With a well set up tailwheel, you shouldn't have any problems, but shimmy can be an issue with big tailwheel tires.

MTV

Mike--

You want the tailwheel to have a 5 to 7 degree positive caster angle with the tailwheel on the ground so when you load you DO NOT go past vertical with the pivot bolt see below

http://akbushwheel.com/TailwheelTechnicalInfo.html

Also a very good artical on Steve's web page (Where I stole the Photo)


Also we just finished the PMA on oue new Husky Tail Spring and hope to add the Cub to the approval in the future as it will help the Cubs as much as it has helped the Husky

http://akbushwheel.com/HuskyTailspring.html

Wup-

What is the width of the new Husky tailspring? Now we start putting husky parts on a cub

 

[westwind]

I had my bbw taken apart and overhauled, I will have to check to confirm just what all they did to it, but it works amazingly well now...
Prior to overhaul it didn't steer very well at all ....

It is certainly is the product of choice for off airport ...

 

[Steve Pierce]

1 1/2" if memory serves correct. I have three at the hanger so I will make sure. The Husky originally had a Super Cub spring if I have my facts straight. They were made by Univair for Aviat but like all the other springs they lost their arch. Bill Duncan kept getting tailwheel warranty claims from Aviat because they were bending the steering arms. They blamed the steering arm but the problem was the geometry of the Husky tail spring. Bill developed a spring with a different temper for Aviat that holds it's arch. Also, the arch is correct when totally loaded and should stay that way. After rearching my own for several years I'd rather buy from Bill and not have to buy from Univair and rearch prior to install.

 

[FdxLou]

I have a BBW and Husky Tailspring (from ABW) on my Smith Cub. All my shimmy problems went away...just as Wup predicted. Empty it was OK...loaded it shimmied. Now all is good.
So far I have 100hrs on this setup...including a trip out West to JC. Could not be happier. The Duncan Clan came through again!!

Lou

 

[akmarty]

Resurrecting an old thread with this question…

1- Is the stock spring (ABI 3 leaf) arched correctly for tall gear/big tires/BBW out of the box?
2-How would a Husky spring improve the geometry/ride? Other mods required? Paperwork requirement for a Husky spring on a PA-12?

My spring was re-arched to restore stock geometry (after a wicked shimmy on landing) but was back flat after less than 10hrs flying. Pretty sure it’s shot. 1996 vintage I think.

My PA-12 configuration:
3” extended PA-18 gear
31” ABW
PA-18 tail feathers
BBW tailwheel

Thanks

 

[Steve Pierce]

The last ABI tail spring I used had the proper arch and has held that arch since install, several years ago. I know they had issues securing a vendor at one time. The Univair Pawnee spring would have the proper arch on installation but would loose arch on a heavy Super Cub within a year.

The Husky spring is different from the PA18 spring. From memory I think I had to shim it.

This thread is 15 years old and lots of things have changed. I bet there is a more current tail spring thread.