The nagging worry of breaking a tailwheel leaf spring prompted me to look through the logs to see when the main leaf spring was last changed and inspect my tailwheel overall. I found no log entry for a leaf spring change. So I decided to order a new main leaf spring to be safe.
Upon inspecting my tailwheel, I found what looks like a broken end on the second longest leaf spring. My thinking is this broken, ragged edge would degrade (a new) leaf spring as the two fret.
Univair sells the main Leaf spring for $95 and the complete spring set for $207.
I plan to order a new spring set U170AB and tailwheel spring connector kit U3239A.
Are there any other parts that normally should be replaced at this time?
Any other recommendations?
Thanks, JP
Be sure to read the vrs posts and you will get some good guidance on changing your springs. Especially be sure to file the bottom end of the leaf where it sits on the main spring (as mentioned in the posts) to prevent a stress riser. That is where they break. In some post George Horn mentioned putting some Teflon tape between each spring. The springs do move as you can tell by looking at yours. When this happens there is some fretting and it appears as rust. I believe George's suggestion to use the Teflon tape to eliminate some or all of that action. It is a problem which is most noticeable when the tailwheel bracket and springs are painted white. I have the tape, but haven't installed it. I finally painted my tailwheel assembly & springs black to make them look better.
In addition to what's said above, I'd replace all bolts, nuts and washers (including the U bolt) with new. Its cheap insurance. When you are changing the leaf springs, you may find some minor discrepancies from what's in the IPC. For example, on mine, the bushing on the main spring at the tail end is flush with both sides of the spring. So I do not need to use the large AN960-815 washer, only the AN960-716 washers -- with one under the head and THREE under the nut. In addition to the obvious hardware, you'll need to remove the 8 (4 on each side) AN3 bolts on the sides of the channel (Item 8 of Fig 29 of the B Model IPC) to get the springs out of the fuselage end. The IPC lists them as AN3-4A, but mine were/are AN3-5A to allow for washers under the head and nut. Don't forget to clamp the springs together before trying to remove them (and before loosening any of the hardware) - a 3" C clamp works perfectly. When everything is loosened, just gently wiggle the springs vertically, and they should slide out fairly easily.
While you are at it, you might as well disassemble, clean, inspect and repack the tail wheel assembly/spindle (Tail Wheel and Fork Assembly). It's not difficult and doesn't take long. Especially inspect the kingpin for cracks and wear. There are posts about failures of them.
When you place the new main leaf spring in the tail wheel/fork assembly, check to see if the spring can be moved sideways any amount in the spacer (Item 4 in Fig 94 of the B model IPC) of the tail wheel/fork assembly. It should be tight. If there is any side movement, you may need to replace the spacer, which should hold the spring tight. It's only about $6 from Air Repair (p/n 3241-3S) (as compared to about $55 from other sources), so you may want to have one on hand in advance.
When installing the AN6-22A bolt through the channel, spring stack, etc at the fuselage end, I suggest that you have on hand another long AN6 bolt (such as an AN6-43A) to insert from the bottom (nut end of the hole) to line everything up before inserting the AN6-22A and its washer from the top, as there is not much clearance above the bolt and it can be difficult to insert the bolt all the way home. (You can't really tap on it from the top). (You need a longer bolt when inserting it from the bottom because the nut end is recessed in the fuselage.)
Since you need to remove your steering springs to change your main leaf springs, you may want to add shackles between the rudder tabs and the steering springs. They make removal, reinstallation and adjustment of the steering springs and chains a snap (shackles: AN115-21; clevis pins for them: AN393-11/MS20392-2C11)
I just went through this, so this info is fresh in my head. After replacing my main leaf spring, I found out that my new one can rotate slightly in my spacer, so I ordered a new spacer from Air Repair. I'm just waiting for it to arrive any day now.
I'm planning to do this to mine soon also. I want to change everything from the fuselage down to the ground. I figure since Ill have it jacked up and torn apart, why not throw in a new tailwheel assy too.
170C wrote:.... In some post George Horn mentioned putting some Teflon tape between each spring. ....
That was a short-term experiment which was not successful. The tape extruded-out and became useless, in my experience. It looks like Aryana had better results.
'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.
Woo- Hoo! Got my new TW parts in yesterday. I put a 1/64' radius on the lower trailing edge of each spring to minimize fretting, sanded, cleaned and primed the springs last night. I'll paint them tonight and hopefully install them Friday (with a little help from the local mechanic).
Sounds like a fun project.
For the eye bolt, Is that a stack of washers in the bag or is that one really thick washer?
Don't forget that lower shackle guard when putting it all back together
Sounds like a fun project.
For the eye bolt, Is that a stack of washers in the bag or is that one really thick washer?
Don't forget that lower shackle guard when putting it all back together
bagarre wrote:Sounds like a fun project.
For the eye bolt, Is that a stack of washers in the bag or is that one really thick washer?
Don't forget that lower shackle guard when putting it all back together
Its a stack of washers for the eye bolt. Some folks have reported running out of bolt threads when torquing the eye bolt - so an extra washer may be needed.
Thanks for the reminder about the lower shackle guard.
OK. Yeah, I have two washers under mine. Coudlnt tell if it was a spacer or something.
As an additional paranoid step, I put some torque seal on the bolt head so I could easily see if it rotated as part of my pre-flight.
A bit late but if you look closely at your original springs you will see the main and the second longest spring are the same thickness and they are both thicker than the top two. The top two are original thickness. The bottom two are the thickness commonly attributed to an L-19 part. I suspect your old second spring is a broken off old main spring which would account for that ruff end "cut".
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
piclr60 wrote:I had trouble finding that u-bolt. Was that from Air Repair also? What was the part number for them?
Thanks
Brad
PN 0642133
'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.
