L-19 Leaf spring installation

[flyingredyeti]

That looks like a typo, given the exploded parts diagram. I would say, with no further information to go on (because it's too late for me to be doing further research today), that the intended quantity is 1.

[toms170b]

Very interesting debate. I can't wait to see how it shakes out. I actually had both the L19 and 170 springs in the shopping cart and decided to check our forums before deciding. My bird is somewhere in between. It has the eye bolt with a thicker main leaf with one of the minor 170 leafs removed to accommodate for the thicker main. There have never been any issues with performance, shimmy, no stress concerns, etc. But the springs are old and I want to change as a precaution. When I went to order replacements I realized I had one less leaf. Took a lot of looking but I did find the missing leaf. Dad has it on the cultivator of the old Farmall Super A. Checked the Farmall records. It was accomplished as a minor alteration.

I have my own opinion on the key points of legality, longevity, aircraft structure stress and benefits of the thicker L19 spring, but i think I am going to watch from the sidelines and let the experts have at it.

Not to add fuel to the fire but looking at the pictures of the L19 with AN bolt and the 170 with eye bolt, the eye bolt is installed wrong. The tie down ring should be down (under the leaf) with the nut on top of Scott 3200. I realize we typically go down and back with bolts on airplanes but both the L19 and 170 parts manual show the bolt head down.

[wingnut]

Not to add fuel to the fire but looking at the pictures of the L19 with AN bolt and the 170 with eye bolt, the eye bolt is installed wrong. The tie down ring should be down (under the leaf) with the nut on top of Scott 3200. I realize we typically go down and back with bolts on airplanes but both the L19 and 170 parts manual show the bolt head down.

The IPC have numerous typos, omissions, and flat out errors of identification. As for direction of installation, this is call for entirely different thread. Illustrated Parts Catalogs are for part identification only, and cannot be used for service or assembly (please do not discuss this here, start a new thread). There are several hardware items on the 170 series that are direction critical, meaning opposite of correct would cause physical interference/contact/chaffing. I've found the eyebolt, if installed upside down as the IPC shows, will chaff on the tire. I can find no justification for installing either bolt upside down. Part catalog sure isn't approved, and upside down is not listed as acceptable data.

[Bruce Fenstermacher]

Tom,

If you have a '48, you should have 5 leaf springs total. It has and additional stubby spring on top. A and B models only have 4 total. The thicker "l-19" spring will fit,though tight, with the other 3 springs. (it is the same mount bracket as an L-19). I would think the thicker spring with just 2 other springs would be so loose as to require a space os some sort.

As for the correct orientation of the L-19 bolt with the ring, on an L-19 under the military, it is down. However most civilians place the ring on top because that more easily facilitates civilian tie downs and civilians have little worry they will be securing their aircraft to a ship deck.

[flyingredyeti]

On this discussion, I have asked for feedback from an instructor of mine, who is also an engineer. I won't bother to paraphrase his thoughts on the matter, but will simply say that he offered to bring me a photo of a similar example, e.g. what happens when a larger spring is installed on the L-19. As for my query to Univair, I have received no response yet.

[cfzxo]

On this discussion, I have asked for feedback from an instructor of mine, who is also an engineer. I won't bother to paraphrase his thoughts on the matter, but will simply say that he offered to bring me a photo of a similar example, e.g. what happens when a larger spring is installed on the L-19. As for my query to Univair, I have received no response yet.

What pray tell are you talking about when you refer to the larger spring???? L-19 spring installed on L-19???? or a larger Kenworth truck spring???

[flyingredyeti]

Honestly, I don't know. He said " Remind me, and I'll bring in a photo of what can happen when you put a larger spring on a L-19". This was in lieu of our conversation, in which he said that people will not only install the larger l-19 spring on a 170, but will also put a larger spring on the L-19. That's all the feedback I have for now. I will post more as soon as I have it.

-joshua

[DWood]

Honestly, I don't know.

If you don't know then why say it?

[flyingredyeti]

Okay, Univair got back to my request for details on the springs. Here is the first email, regarding spring dimensions:

Univair Customer Service <info@univair.com>
To *********************
Jul 20 at 1:06 PM
Dear Joshua,

Thank you for your inquiries! Upon investigating the dimensions of
these tailwheel spring assemblies, I am able to find only 1 difference
in there composition. The U170 Cessna 170 tailwheel spring set's and
the U170AB Cessna 170A / Cessna 170B tailwheel spring set's main
tailwheel leaf spring measures 0.312 inches thick. The L19TWS Cessna
heavy duty tailwheel spring set's main tailwheel leaf spring measures
0.375 inches thick. Please let me know if I may be of further assistance?

Best regards,
Mark Wiggs
Sales Representative
Univair Aircraft Corporation

[flyingredyeti]

My follow-up email:

Mark,
Thanks again for your feedback- I have a couple of more questions for you on the subject.
First, can you tell me if the U170 series main tailwheel spring dimensionally matches that of the factory model 170 springs?
Secondly, can you tell me what the difference in spring tension is between the 170 main spring and the L19TWS Heavy duty spring are?
Can you tell me the PMA # for the L19TWS spring?
Lastly, can you tell me if the L19TWS Heavy duty spring is approved for substitute installation on a Cessna 170(A/B)?
Regards,
Joshua.

. . .and the response (they were quick!):

Dear Joshua,

Thank you for your reply! Univair's U170 FAA/PMA approved tailwheel
spring set is a direct replacement for Cessna 170's. Unfortunately,
there is no published spring tension for these tailwheel spring sets.
The U170 tailwheel spring set is composed of 4 leaves and 1 plate. The
4 leaves are made from 1.5 inch wide x 0.312 heat treated spring steel
5160h/9260. The L19 tailwheel spring set is composed of 4 leaves. The
main leaf is made from 1.5 inch wide x 0.375 heat treated spring steel
5160h/9260 and the other 3 leaves are made from 1.5 inch wide x 0.312
heat treated spring steel 5160h/9260.

The L19TWS is composed of 1 x 0642101 main leaf spring, 1 x U0542105
tailwheel spring, 1 x U0442109-2 tailwheel spring, and 1 x U0442108-2
tailwheel spring. The 0642101 main leaf spring is raw material and has
no FAA/PMA approval. The remaining 3 leaves are FAA/PMA approved
tailwheel springs for C-170's, C-170A's, and C170B's.

[wingnut]

Well.......there is obviously some manufacturing tolerances in there. I've had 5 Cessna 170's and one L19 (305A) in the hangar recently; all at the same time. The most thin spring I've measured is .312 (5/16"). The thickest spring I've measured is .335", on the L19 and 4 of 5 170's. So, roughly thirty thousandths difference (1/32") and no install problems in my experience.
I would like to learn more about the "heavy duty" L19 leaf. I've not seen one yet.

[Ryan Smith]

Honestly, I don't know.

If you don't know then why say it?

Because he thinks we're all idiots.

[cfzxo]

Honestly, I don't know.

If you don't know then why say it?

Because he thinks we're all idiots.

Ryan, The saying goes something like this, If you learn from your mistakes, and I have made a few, that would put me in the geneius category. But with an open mind to make more.

[cessna170bdriver]

Honestly, I don't know.

If you don't know then why say it?

Because he thinks we're all idiots.

VERY un-called for comment, Ryan. Not at all how we want the Association to be represented.

[Ryan Smith]

VERY un-called for comment, Ryan. Not at all how we want the Association to be represented.

You're right, Miles. To Joshua and the Association - please accept my sincere apologies for my poor attitude and comments. It's not consistent with the respect I've been given by Association members and is not representative of what the Association embodies. I'm ashamed that I've been immature, disrespectful and petulant to others on this forum over the past week. I'm truly sorry.