+20 year old donuts (1966 M20E)

[carusoam]

Great update Gert!

If you are working with @M20Doc... that might be helpful to the Mooney mite community as well...

The mites have no rubber donut supplier...  so a few hundred owners could really use some help... their donuts are similar, just different...

Best regards,

-a-

[Guest]

Here’s what the Mite discs look like.  I found and paid dearly for this NoS set.

Clarence 

[carusoam]

@Gert have a look at Doc’s post above...

-a-

[vorlon1]

11 hours ago, Will.iam said:

Reviving this subject. Did anybody test these on their plane yet? $60 per donut including shipping sure beats $130. Mine were replaced in 2007 so I’m over due. 

Mine are original from 67,  so I'm over due also. Months ago I offered to test and pirep, but got no response.

[Will.iam]

On 3/24/2021 at 9:36 PM, vorlon1 said:

Mine are original from 67,  so I'm over due also. Months ago I offered to test and pirep, but got no response.

That’s not very encouraging. Hope this isn’t like the all the other promises that never come to fruition. 

[Yetti]

@Gert how is disc production going.   Seems like some folks are ready to purchase.

[vorlon1]

Waiting on his "official" word, but he recently wrote me stating that his web site is open for business...

https://avunlimited.co/

[cliffy]

Checked out his web site- interesting- he should do very well

[carusoam]

https://avunlimited.co/shop/
 

Right to the .050 amu price point...

-a-

[Trenta]

Just did mine in October. Not because they weren’t to spec just because I thought it was a good idea. It had been 25 years on the mains and 30 on the front. I wouldn’t replace until they are on the verge of being out of spec. The difference between 30 year old pucks that haven’t started cracking and still in spec vs new ones is so negligible. I couldn’t tell you I noticed a difference. 
 

-Trent

[Ck2uam]

We just finished ours. Mains easy. Too easy! Nose, well not so much. But I built a compression tool that goes on the hangar floor with two tapcons. Safely and easily makes pinning that collar bolt a breeze. And a turnbuckle to finish the job. I’m in Vero Beach, FL. It’s yours to borrow if anyone ever needs one. anvilair@hotmail.com

Edited June 13, 2021 by Ck2uam

[carusoam]

Great pic… now with gravity….  

-a-

 

[Ck2uam]

Thanks carusoam. 

[vik]

Anyone is interested in purchasing shock disks from https://avunlimited.co/ to combine shipping? Looks like shipping is fixed at $200/order. The shipping charge makes sense as shipping from SA with a courier delivery (with tracking number) can be expensive unless you are a big commercial outlet. I need to replace all shock disks in my Mooney, so I am considering to order.

[Gert]

Hi Members

The high shipping cost is driven by the volumetric weight of the discs. The discs weigh but 2.33kg  for a stack of 11 but the volumetric weight is 5kg. DHL also slaps on a heavy surcharge during covid times. We are in a Lockdown Level 3 situation in South Africa and strict sanitising protocols apply which also drive costs up.  

If there are any members with contacts at USPS we might be able to ship to a central drop-off point and distribute internally with USPS. The next batch are being manufactured and delivery will start by 21st June Covid willing. My experience with dealing with USPS was to say the least, like getting my teeth pulled.

That being said, I still can keep the cost of these disks at approximately 50% below what is available elsewhere. Members must please look on the AVUnlimited website for the pdf link to download the detailed drawing and instruction sheet.  This sheet must be completed, signed and emailed to me. This will answer the FAA Owner Produced Part Regulation, FAR 21.303(b)(2). The original form must then be handed to your AMO as source document. The AMO must then note the replacement parts as Owner Produced in the airframe logbook and attached the form.

Members can order their discs in advance as I manufacture in relatively small batches(400 disks) at a time. The stock runs out fast.

If any members have questions or queries, please email me at gert@avunlimited.co

[carusoam]

Gert,

Thanks for sharing the details…

Any headway on the Mite sized disks?  (I know somebody will ask…)
 

Congrats to vik on his first post…

Best regards,

-a-

[Guest]

On 6/3/2021 at 10:08 PM, Trenta said:

Just did mine in October. Not because they weren’t to spec just because I thought it was a good idea. It had been 25 years on the mains and 30 on the front. I wouldn’t replace until they are on the verge of being out of spec. The difference between 30 year old pucks that haven’t started cracking and still in spec vs new ones is so negligible. I couldn’t tell you I noticed a difference. 
 

-Trent

The only issue is that with lighter models the discs never compress below limits.  They just get harder.

Clarence

[Shadrach]

9 hours ago, M20Doc said:

The only issue is that with lighter models the discs never compress below limits.  They just get harder.

Clarence

I am replacing my original discs this week. The date code is from 67. They are not hard nor cracked and still meet limits specified in the MM. However, I noticed on a cold winter day that they failed to meet limits by a considerable amount if not given at least a half hour to expand when on Jack’s. This was not the case when I jacked the plane up earlier this week. I’ve not made replacing them a priority because they continued to meet specs and do not visibly exhibit any signs of age. I can say this for almost all of the rubber on my airplane save for the behind the panel vacuum lines on a PC system which seem to last about five years. All of the PC boots as well as the step actuator are supple and flexible. Having the airplane hangared its whole life is the only thing I can think of that accounts for this. 
 

I wish I had a press so that I could measure the compressibility of the old donuts versus the new.  Time will tell how the new ones behave in cold conditions but I don’t expect to feel much difference during taxi or when landing

Edited June 18, 2021 by Shadrach

[Hank]

1 hour ago, Shadrach said:

I wish I had a press so that I could measure the compressibility of the old donuts versus the new.  Time will tell how the new ones behave in cold conditions but I don’t expect to feel much difference during taxi or when landing

When you take them off, place a stack of old ones beside a stack of new ones. Cold weather is when old donuts show up as a  problem, the gear won't raise after takeoff.

[Shadrach]

2 hours ago, Hank said:

When you take them off, place a stack of old ones beside a stack of new ones. Cold weather is when old donuts show up as a  problem, the gear won't raise after takeoff.

Where is the squat switch? My gear extends to full travel in winter it’s just that the discs don’t expand to fill the gap for at least 10mins maybe more.

[Hank]

Just now, Shadrach said:

Where is the squat switch? My gear extends to full travel in winter it’s just that the discs don’t expand to fill the gap for at least 10mins maybe more.

Mine is on the left main, up inside the wing. You should see a small tab to one side of the gear leg, which presses on the switch. If the pucks are hard and compressed, the tab won't reach.

[Shadrach]

16 minutes ago, Hank said:

Mine is on the left main, up inside the wing. You should see a small tab to one side of the gear leg, which presses on the switch. If the pucks are hard and compressed, the tab won't reach.

My gear has big bar between the seats… no switch in the mains.  I’m still trying to get my head around the how compressed pucks keep the gear from extending off a squat switch. The pucks only affect the gear in compression not in tension. The gear swing arm should extend to full travel regardless of the puck condition.

Edited June 18, 2021 by Shadrach

[Vance Harral]

38 minutes ago, Shadrach said:

I’m still trying to get my head around the how compressed pucks keep the gear from extending off a squat switch.

Below are photos of the mechanism in the left main.  In the annotated photo, the electrical switch is outlined in red.  It is a spring-open, push close switch.  The spring is quite firm.

The switch is actuated by the rocker arm outlined in green.  When the disks are compressed on the ground, the forward arm of the rocker is pushed up by the rod outlined in blue, and the aft arm pushed down, such that the aft rocker arm loses contact with the switch.  The spring-loaded switch opens, which breaks the circuit that allows the gear to retract.

At takeoff, the pucks expand, which moves the rod down, in turn moving the forward arm of the rocker down.  This is supposed to push the aft arm of the rocker up to push against the spring-loaded switch, thereby closing it and allowing the gear to retract.

As I said, the spring in the switch is quite firm.  The weight of the wheels pulling the rod down is insufficient to close it.  The mechanism only works if the expansion of the pucks pushes hard enough against the swing arm to draw the rod down with enough force - through the rocker - to push the switch closed.

 

 

Edited June 18, 2021 by Vance Harral

[Shadrach]

1 hour ago, Vance Harral said:

Below are photos of the mechanism in the left main.  In the annotated photo, the electrical switch is outlined in red.  It is a spring-open, push close switch.  The spring is quite firm.

The switch is actuated by the rocker arm outlined in green.  When the disks are compressed on the ground, the forward arm of the rocker is pushed up by the rod outlined in blue, and the aft arm pushed down, such that the aft rocker arm loses contact with the switch.  The spring-loaded switch opens, which breaks the circuit that allows the gear to retract.

At takeoff, the pucks expand, which moves the rod down, in turn moving the forward arm of the rocker down.  This is supposed to push the aft arm of the rocker up to push against the spring-loaded switch, thereby closing it and allowing the gear to retract.

As I said, the spring in the switch is quite firm.  The weight of the wheels pulling the rod down is insufficient to close it.  The mechanism only works if the expansion of the pucks pushes hard enough against the swing arm to draw the rod down with enough force - through the rocker - to push the switch closed.

 

 

Thanks Vance!  You exceeded expectations with your explanation!  That makes perfect sense. That must be one stiff spring. Wheels, tires, cast iron disc and brake caliper is a fair amount of weight.

[Vance Harral]

44 minutes ago, Shadrach said:

That must be one stiff spring. Wheels, tires, cast iron disc and brake caliper is a fair amount of weight.

It's stiff enough that I can't easily push it in by hand, at least not in the installed location.  The other thing is that if you look closely, you'll see the forward arm of the rocker is a little shorter than the aft arm.  So the force exerted by the discs and the gear swing arm is mechanically attenuated.  i.e. i takes even greater pressure on the forward side of the rocker to close the switch than it would if you pushed it directly.

The whole mechanism is bulky and somewhat Rube-Goldberg-ish.  I'm not sure why it was designed this way, except to guess that it's "industrial strength" because it is situated in a relatively harsh environment