Landing Gear Shock Disks Source?

[Fly Boomer]

3 hours ago, gummirat said:

Hi All ,had a lab batch of the compound made and tested, 4300 lb tensile,600% elongation comp set 18% great numbers eh carusoam. m20doc any luck on the measurements? Kevin any luck on the print? I'm into this just south of 1k would like to see the interest or did I waste the money? Mark

 

Let's let these people know you posted @Kevin Harberg @carusoam @M20Doc

[alexz]

3 hours ago, gummirat said:

Hi All ,had a lab batch of the compound made and tested, 4300 lb tensile,600% elongation comp set 18% great numbers eh carusoam. m20doc any luck on the measurements? Kevin any luck on the print? I'm into this just south of 1k would like to see the interest or did I waste the money? Mark

 

Given the price of current M20 disks, wonder if your process can be efficient replacement for those crazy priced parts?

[gummirat]

Hi Alexz, The manufacturing process is the same. To do it would require PMA approval. Not impossible but another hurtle. Going up against Lord is like David(OMC R&D) and Goliath(Lord) if Goliath was 5ft taller and David a dwarf with one arm and arthritis. I have been trying to get this project going for 3yrs and it seems like herding cats. Mark

[N201MKTurbo]

21 minutes ago, gummirat said:

Hi Alexz, The manufacturing process is the same. To do it would require PMA approval. Not impossible but another hurtle. Going up against Lord is like David(OMC R&D) and Goliath(Lord) if Goliath was 5ft taller and David a dwarf with one arm and arthritis. I have been trying to get this project going for 3yrs and it seems like herding cats. Mark

How has Lord impeded you in getting these made?

Are you going to manufacturer them yourself, or try to find someone to make them for you?

Do you have drawings for all the parts?

Have you designed a mold? 

Have you come up with a method of injecting the liquid rubber into the mold?

If you are going to hire someone to make them for you, I would expect $20k to $50K of NRE and tooling. If not more.

[gummirat]

Turbo, no Lord hasn't done anything to me. They are a good company with the resources to do the job. I manufacture rubber parts and also consult and design. The m-18 parts are a better fit for me (Low volume, simple design). I have worked in the rubber industry for 45yrs. and 13 on my own. i work with a PMA holder on some parts so I know a little about that process. Yes, I know the tooling is expensive and certification also, hence the 2nd thoughts before doing a m-20 project.

[N201MKTurbo]

1 hour ago, gummirat said:

Turbo, no Lord hasn't done anything to me. They are a good company with the resources to do the job. I manufacture rubber parts and also consult and design. The m-18 parts are a better fit for me (Low volume, simple design). I have worked in the rubber industry for 45yrs. and 13 on my own. i work with a PMA holder on some parts so I know a little about that process. Yes, I know the tooling is expensive and certification also, hence the 2nd thoughts before doing a m-20 project.

Thanks for the info. I wasn't aware of all that. If you can manufacture the parts, I don’t think the PMA process is that bad.

[KSMooniac]

In light of the recent price increase, I think there is a big opportunity now to make the M20 versions if you're interested. I bet you could get enough pre-orders and perhaps even some money to fund tooling from our folks here, so long as you could get closer to the old price! I understand that the volume might be too much, though, and not worth the effort.

Sent from my LM-V600 using Tapatalk

[Kevin Harberg]

Hello Mark @gummirat  I will contact the Smithsonian and check on prints (I expect Firestone has the original drawings for the M18 shock discs), the 1946 design used several outsourced rubber components (including 1942-1959 Chevrolet/GM truck starter pedal boot used on nosewheel steering tube fuselage seals).

 

Edited May 16, 2023 by Kevin Harberg
Added content

[gummirat]

Hi Kevin, Thanks for doing that. I believe you are right it's proprietary to Firestone and they are gone, prints mold and all. Without a part to measure we are dead in the water. I don't believe IA/AP will install a part on someone's SWAG on how it should be and I don't blame them. As soon as the last part is installed it goes from a NOS to a used part and will be hard to sell those measurements to the powers that be. Mark

 

[Ardvark111]

I would be interested in a set of 6 as well..

Not sure what the end goal is for this right now, but if it is to get an STC or PMA  (now that the type Certificate is for sale whoever buys it can say it’s an approved part since all the data is available), those are both lengthy and expensive propositions. 
 

Personally, with the proper documentation that could come with the parts, I would say they could fall under “owner produced” or maybe look at the VARMA policy the FAA recently approved. 
https://www.eaa.org/eaa/news-and-publications/eaa-news-and-aviation-news/news/-/media/6E283E810882480CAFF007430FED9246.ashx

[gummirat]

Hi Ardvark 111, Thanks for the interest. this is how I want to proceed (VARMA) but I need a print, original or from a NOS part before I contact FSDO. there are only 6 NOS left that I know of. My machine shop owes me a favor so i can get it on the optical comparator and a print made cheap. I don't want to get rich just my cost and beer money. Mark

 

[Ardvark111]

If I had one, I’d give it to ya!

Good luck! We can use them if you can make them!

[gummirat]

Hey Kevin Harberg, any luck with the prints? Thanks Mark

[Bolter]

On 5/22/2023 at 5:03 PM, gummirat said:

Hi Ardvark 111, Thanks for the interest. this is how I want to proceed (VARMA) but I need a print, original or from a NOS part before I contact FSDO. there are only 6 NOS left that I know of. My machine shop owes me a favor so i can get it on the optical comparator and a print made cheap. I don't want to get rich just my cost and beer money. Mark

 

Mark: Not sure what your resources and strong suits are, but I have my own Solidworks license (to keep it legal) and make engineering drawings as part of my job.  If you have a sample drawing of a similar part that I can mimic, I can make a new one for you to match what you need for future steps.  We can talk details privately, but for just a few drawings, I am happy to  consider it a contribution to the community.  -dan

[gummirat]

Hi Bolter, Thanks for the offer, it's appreciated. I have an optical comparator available and the software to make the print. The issue is m-20 doc has the last 6 parts on earth and does not want to loan them out (understandable, with cost and no availability). I can have it measured and a print made in about a week (takes some time to sneak in between the regular production) mold will be about 6wks. and how ever long for approval.

[Kevin Harberg]

On 6/1/2023 at 9:59 AM, gummirat said:

Hey Kevin Harberg, any luck with the prints? Thanks Mark

Hi Mark @gummirat

An application form has been mailed to the Smithsonian and I am awaiting the quote for drawing 0662 (Pad - Lower Shock). This is a bit of a slow process as the Smithsonian only permits mailed-in applications using their approved form, and then they contact the person requesting a copy of the print. The size of the print is negotiated and a quote issued prior to payment transaction. Then they mail the print. Everything done via snail mail. At no time does the Smithsonian review the print to advise if it contains the information desired (I reviewed all available prints a second time to determine if it is the most likely drawing containing the information you require). I am hopeful but not certain that any useful data will ensue.

[gummirat]

Hi Kevin, here's to hope (fingers crossed). When I get it I 'll proceed to FSDO for approval. I hope there is enough interest to pull this off. Mark

[gummirat]

Hey Kevin Harberg, hear anything on the prints? Mark

[Kevin Harberg]

13 hours ago, gummirat said:

Hey Kevin Harberg, hear anything on the prints? Mark

Still no response from the Smithsonian. I provided eMail address, physical address, and phone number for correspondence. I hope they didn't send an untitled eMail (I send those to "Junk" and delete "Junk" on a regular basis. Wish I could discuss purchase with a "real" person via telephone. How I long for the past.

 

[gummirat]

Hey Kevin, still no response from the Smithsonian?

[Kevin Harberg]

On 7/28/2023 at 7:48 AM, gummirat said:

Hey Kevin, still no response from the Smithsonian?

Hi Mark .

I have now received the requisition forms and will be sending back to the Smithsonian tomorrow (August 1, 2023). Will DM you with details via Mooney Space. 

 

 

[thomas1142]

I got lost/confused in this thread. I have 1997 M20J, and need shock disks, will this help me?

thanks

[gummirat]

Hi Thomas 1142, no these are for the mite sorry. If I can't get some unused dimensions this project it is dead in the water. Mark

[gummirat]

Hi All, here are the dimensions I need. these were taken from Kevins old part that was approx.40yrs old. Hope the pdf opens.

Mount (2).pdf

[carusoam]

Hey all!
 

Mark’s drawing is here…

Let me invite Mark and Doc… @gummirat and @m20doc (this one requires a separate email)
 

Lots of good effort being applied to this project.

 A few things we know…(?)

1) For user produced parts… we need to be as close to original dimensions and materials as possible…

2) hard part… , rubber on its own… changes dimensions continuously over time… it slowly flows from various forces… both internal and external…  (similar to glass in old churches… yes glass actually flows, very sloooooowly)

These changes are hard to predict, and hard to tell what changed over time.

3) Modern donuts are designed in the same way as the Mite’s donuts were… to behave the same way and do the same thing… just scaled appropriately…

4) Anyone that has seen a decade old donut compared to the brand new donut…

they start out as a very flat washer shaped (or pipe shaped) items… and squeeze outwards and downwards over the years… with internal stresses also being relieved over time…

unfortunately for me… under higher weights, the Ovation squeezes its donuts about 1.5X the rate the lighter Mooneys do… on the same donuts.

5) all of the curvy shapes most likely occurred over time, under various weights, through various temperature swings…

6) For this application…

the bulk properties of the rubber are an important part… compression and rebound.

Some dimensions are primary to make sure they fit on the tube, without sliding around… not too small, not too big… pure mechanical fit.

Then there are these magical discs of metal… between the donuts.

7) the magical discs make the dimensional shifts of the rubber… much less important, and allow for slop in dimensions and donuts sliding or rotating around the tube…

 

8) If you can do computerized stress analysis on a washer shape and the fancy shape of the aged donut… you will find the edge shape effects don’t provide any support for the plane…

kind of like wing tip affects and loss of lift….

9) compression of a donut shaped object… (engineering 101) all dimensions increase outwards in the radial direction.  So there isn’t a risk of the inner diameter some how constricting under load and crushing the steel tube…

10) Stress = Force / Area…  for the donut… weight / area of the donut’s surface.

11) If you look closely… the M20B and M20V are using the same donut dimensions… (?)

12) Oddly, the nosewheel donut didn’t change characteristics when it carried an O360 or a TN’d IO550…

13) the donut limitations didn’t arrive until the long bodies came on the scene… where there is a different number for MGTW and MGLW…  this is more the entire landing gear limit, not just the donut.

 

14) next possible steps…

obtain the OD, ID, and thickness of the most original part…. Grab dozens of measurements all around… and average them…

combine with a pic…

Expect dimensions within a 1/10” for this part, is more than Mooney ever needed…

All of the other curves, bends, and bumps… are most likely the effects of time and stress…

 

15) the part was originally designed as a basic rubber pad to support a Mack truck’s engine in the mid 1900s… (possible quote from some Al Mooney history book)

Al Mooney was good at finding things that already worked, that were commercially available, instead of re-inventing the wheel…

16) Don’t forget…  the part was probably also marked on the outer side with a date code for date of manufacture… month / year.  It helps to put a line under it… so 6 and 9 don’t get confused… over the decades…  

17) Rubber chemistry… including % X-linking…

notes on cross linking… more X-linking makes the rubber harder… less X-linking makes the rubber softer, but flows more over time…

Often, X-linking in rubber, slowly increases over time… making the rubber hard, and less rubbery.

rubber that breaks down due to environmental stresses… often becomes sticky on the surface…

the amount of carbon black in the formulation also has affects on the final properties… that also include UV resistance…

18) Fortunately for MSers… Gummirat is our resident rubber technology guy!   
 

19) Looks like the pic below, indicates a donut with the following dimensions…

OD 3.25”

ID 1.0”

Thickness  1.0”

20) include the OD of the steel tube that these donuts get mounted on…

it is really important that the donut fits over the tube without being stretched to make it fit…

*******

 

Note: these are old memories of a private pilot, that once had some additional knowledge of polymers, but not a lot… hoping that this is helpful…  

Best regards,

-a-