SHAW 431-9 FUEL CAP CONUNDRUM

[DCarlton]

Hello again.  The locking tab on one of my shaw fuel caps is popping up after putting a drop of oil on the bearing surface to make it easier to operate.  Since then, I've disassembled the cap and cleaned it.  The fluorosilicon o-rings and Marsh bearing washers are relatively new.  Regardless of how I adjust the nut (tight / loose / in-between), it pops open on it own.  Anyone able to resolve this?  I'm wondering if the bearing surface on the locking tab has become too worn or too rounded.  Thanks. 

[N201MKTurbo]

If you dress the bottom of the tab with a file, it should fix it.

[DCarlton]

1 hour ago, N201MKTurbo said:

If you dress the bottom of the tab with a file, it should fix it.

I did that once a few years ago.  Is my objective to round the edge more or less?  Was also wondering if it was already rounded too much.  Thanks.  

[N201MKTurbo]

2 hours ago, DCarlton said:

I did that once a few years ago.  Is my objective to round the edge more or less?  Was also wondering if it was already rounded too much.  Thanks.  

I would round it less. You need to look at the line from the pivot down to the flat with the tab closed. There needs to be flat on that line or it will pop open.

[Fly Boomer]

15 hours ago, DCarlton said:

The fluorosilicon o-rings and Marsh bearing washers are relatively new.

Did you pay ~$70 each for those Marsh rings?  I try not to whine about the cost of parts, but I have four caps, and it seems excessive.

[DCarlton]

11 minutes ago, Fly Boomer said:

Did you pay ~$70 each for those Marsh rings?  I try not to whine about the cost of parts, but I have four caps, and it seems excessive.

Yep.  Got tired of fighting the caps.  I've tried to recondition them, lubricate them, etc.  Not sure the washers are worth it yet or if they will last.  I've only installed one on the cap I'm having trouble with.  Just got them.  I have three caps to juggle to find the two best.  Gonna try the recommendation to dress and flatten the bottom of the locking tab next.  

[Fly Boomer]

3 minutes ago, DCarlton said:

Gonna try the recommendation to dress and flatten the bottom of the locking tab next.  

Please report back.  I too have a spare (5th) cap, but that's mostly to get me out of a jam if one breaks or somebody leaves it on the wing.  I have one that doesn't "pop up" all the way, but it doesn't lock entirely flat either.

[DCarlton]

1 minute ago, Fly Boomer said:

Please report back.  I too have a spare (5th) cap, but that's mostly to get me out of a jam if one breaks or somebody leaves it on the wing.  I have one that doesn't "pop up" all the way, but it doesn't lock entirely flat either.

Will do.  I actually had to use my spare the other day to fly.  Been carrying it around for years.  

[Yetti]

1 hour ago, Fly Boomer said:

Did you pay ~$70 each for those Marsh rings?  I try not to whine about the cost of parts, but I have four caps, and it seems excessive.

https://www.amazon.com/O-Rings-Fluorosilicone-Seals/s?rh=n%3A16413611%2Cp_n_feature_seven_browse-bin%3A5485467011

[Fly Boomer]

55 minutes ago, Yetti said:

https://www.amazon.com/O-Rings-Fluorosilicone-Seals/s?rh=n%3A16413611%2Cp_n_feature_seven_browse-bin%3A5485467011

These are the Marsh rings we were discussing

https://www.marshbrothersaviation.com/products/shaw-aero-fuel-cap-washers

[Yetti]

12 minutes ago, Fly Boomer said:

These are the Marsh rings we were discussing

https://www.marshbrothersaviation.com/products/shaw-aero-fuel-cap-washers

If it's adjusted properly you should not need that.  The O rings on the shaft should prevent water intrusion.   but if you feel the need HDPE sheet and exacto knife should have you going.    https://www.amazon.com/Density-Polyethylene-Standard-Tolerance-Thickness/dp/B0070Z8PDW/ref=sr_1_2?crid=3MEVJOPLHL7H8&dib=eyJ2IjoiMSJ9.nqtE7lGqNuaPmPfS2B_ipA4dZAJMDcF_mvn3aMBMJA0PiM5-PDmAev4qo6Q7JhyZHdyJ_Tr5w25TwgCIK2ShbDrJzN_ZHqh2-XHY3at_JHfszyvdSSHr7pwRcW9WStgMSSz5jwZjg_9yNGHv6MI1cN-GOquGny3QJNM2uurqfAbJIGBrtJaS16ZSyX5qxRAlezP9yUJvZTz4ubKtkq0W1k8ZGO8pXMCITte4HS7dYQM.GoWziuZIfEnEW8Tor4rro9Smvl06mczWPQ6G_AOuEV4&dib_tag=se&keywords=1%2F16%2Bhdpe%2Bsheet%2Bblue&qid=1721843532&sprefix=1%2F16%2Bhdpe%2Bsheet%2Bblue%2Caps%2C283&sr=8-2&th=1

[M20F]

$2 at THD, this dude is a total idiot…

 

[DCarlton]

16 hours ago, N201MKTurbo said:

I would round it less. You need to look at the line from the pivot down to the flat with the tab closed. There needs to be flat on that line or it will pop open.

Filed and dressed (flattened) the bottom of the locking tab as recommended (see pic).  Worked like magic.  Thanks!  Mooneyspace rocks.  

[N201MKTurbo]

 

5 minutes ago, DCarlton said:

Filed and dressed (flattened) the bottom of the locking tab as recommended (see pic).  Worked like magic.  Thanks!  Mooneyspace rocks.  

Glad to hear it worked out. I would paint it to keep it from corroding. 

[DCarlton]

2 hours ago, Yetti said:

If it's adjusted properly you should not need that.  The O rings on the shaft should prevent water intrusion.   but if you feel the need HDPE sheet and exacto knife should have you going.    https://www.amazon.com/Density-Polyethylene-Standard-Tolerance-Thickness/dp/B0070Z8PDW/ref=sr_1_2?crid=3MEVJOPLHL7H8&dib=eyJ2IjoiMSJ9.nqtE7lGqNuaPmPfS2B_ipA4dZAJMDcF_mvn3aMBMJA0PiM5-PDmAev4qo6Q7JhyZHdyJ_Tr5w25TwgCIK2ShbDrJzN_ZHqh2-XHY3at_JHfszyvdSSHr7pwRcW9WStgMSSz5jwZjg_9yNGHv6MI1cN-GOquGny3QJNM2uurqfAbJIGBrtJaS16ZSyX5qxRAlezP9yUJvZTz4ubKtkq0W1k8ZGO8pXMCITte4HS7dYQM.GoWziuZIfEnEW8Tor4rro9Smvl06mczWPQ6G_AOuEV4&dib_tag=se&keywords=1%2F16%2Bhdpe%2Bsheet%2Bblue&qid=1721843532&sprefix=1%2F16%2Bhdpe%2Bsheet%2Bblue%2Caps%2C283&sr=8-2&th=1

I'm just guessing but it may be Delrin (or something like it).  I wanted to try the Marsh washers since they are "self lubricating".  Figure the caps might operate easier and more consistently without a lot of fuss.  I'm keeping my metal bearing washers just in case.  

[DCarlton]

Just now, N201MKTurbo said:

 

Glad to hear it worked out. I would paint it to keep it from corroding. 

Yep.  One little thing at a time.   

[geoffb]

I need to get around to making some replacement levers.  Dressing the bottom works a bit, but ultimately you'll lose clamping and there's no way to adjust for the loss of lever thickness.

[Skates97]

On 7/23/2024 at 9:20 PM, N201MKTurbo said:

I would round it less. You need to look at the line from the pivot down to the flat with the tab closed. There needs to be flat on that line or it will pop open.

I had the same thing. Took a file and flattened off the bottom of the tab to take the round out and they easily snap closed and stay that way now.

[Yetti]

On 7/24/2024 at 3:54 PM, DCarlton said:

I'm just guessing but it may be Delrin (or something like it).  I wanted to try the Marsh washers since they are "self lubricating".  Figure the caps might operate easier and more consistently without a lot of fuss.  I'm keeping my metal bearing washers just in case.  

I would probably go with HDPE since they make gas cans out of it.    Both seem to be similar.   https://www.xometry.com/resources/materials/hdpe-vs-delrin/

[DCarlton]

23 hours ago, geoffb said:

I need to get around to making some replacement levers.  Dressing the bottom works a bit, but ultimately you'll lose clamping and there's no way to adjust for the loss of lever thickness.

and the center pins corrode.  

[geoffb]

Pins would be easy, it's a single setup in a turning center.  Do folks need pins?

[N201MKTurbo]

It doesn't seem like making replacements would be hard. They could easily be made on a CNC. The originals look like an investment casting which wouldn't be that hard either.

But to do it right would require a PMA and there is an overhead associated with maintaining and setting up an operation to manufacture them under PMA. 

What is the market for these? they last just about forever. And used ones are easy to come by. 

I think it is one of those things where after setting it up, you may end up selling 10 or 20 a year. Even at $1000 each, you couldn't pay a single employee to do the manufacturing, shipping and receiving, accounting Etc...

[EricJ]

Could 3D print everything, too.    This cries out to be OPP. 

 

[DCarlton]

5 hours ago, N201MKTurbo said:

It doesn't seem like making replacements would be hard. They could easily be made on a CNC. The originals look like an investment casting which wouldn't be that hard either.

But to do it right would require a PMA and there is an overhead associated with maintaining and setting up an operation to manufacture them under PMA. 

What is the market for these? they last just about forever. And used ones are easy to come by. 

I think it is one of those things where after setting it up, you may end up selling 10 or 20 a year. Even at $1000 each, you couldn't pay a single employee to do the manufacturing, shipping and receiving, accounting Etc...

Yeah.  I posted this on another thread, but I just purchased a used spare cap from BAS Parts, for $100 and it works better than my two original caps and the center pin isn't corroded.  New o-rings and it's good.  

[geoffb]

On 7/29/2024 at 10:15 AM, N201MKTurbo said:

It doesn't seem like making replacements would be hard. They could easily be made on a CNC. The originals look like an investment casting which wouldn't be that hard either.

But to do it right would require a PMA and there is an overhead associated with maintaining and setting up an operation to manufacture them under PMA. 

What is the market for these? they last just about forever. And used ones are easy to come by. 

I think it is one of those things where after setting it up, you may end up selling 10 or 20 a year. Even at $1000 each, you couldn't pay a single employee to do the manufacturing, shipping and receiving, accounting Etc...

Yes, you could bang these out a small cnc center.  I haven't finished a model, but I don't think you'd have 5 minutes of machine time per. 

I think you'd go the owner produced part route.