Oil filter warning

[kmer]

I'm inclined to believe that the flat ring would seal better.

I apologize in advance for disagreeing.

Assumption: The rubber has the same properties in both rings.

The picture shows cross sections of the o-ring and flat-ring style seals in their normal state and in their deformed state (exagerrated). Note that the flat ring corners would have a tendancy to maintain their 90 degrees. The rubber bulges at the sides and while the top and bottom compensate causing those surface to have less resisting force. Now your sealing power is divided equally in two between the inner and outter edges.

I doubt it matters anyway with the amount of force being applied. The point is -- o-rings are probably better. They use o-rings as head gaskets, but I don't recall seeing any that were flat.

 

[fixcnc]

I also like the flat ring better.

 

[kmer]

I also like the flat ring better.

How come?

 

[LazyBastard]

The flat ring won't deform like that, its in a slot that holds the sides in. There is a larger sealing surface area on the flat ring... not only because its flat, but because its just WAY BIGGER.

 

[fixcnc]

as long as the flat ring is contained it "must" conform to the shape it is contained in.

 

[kmer]

The flat ring won't deform like that, its in a slot that holds the sides in. There is a larger sealing surface area on the flat ring... not only because its flat, but because its just WAY BIGGER.

Yeah, I forgot about the slot. Good point. But still, the part that is above the slot must deform, so the drawing would only apply to that portion.

As for the larger sealing surface .... the clamping force required to achieve the same psi on the seal surface is higher when the surface is larger. Assuming the same clamping force on both, the larger surface would have less psi (and less resistance).

 

[LazyBastard]

There's a couple of things to consider here;

1) Your deformation is in the wrong direction. There would be higher pressure at the center because there is nowhere for the rubber to deform to. You can test this by squeezing a piece of rubber in a vise.

2) Even if it did deform as you suggest, that would effectively be TWO rings instead of one. Ever look at a marine oil seal - they're double ridged.

3) Surface area is more important than pressure. Our goal is to make *contact*, not squeeze the crap out of it. Spec on most cars is "touching + 1/2 to 3/4 turn", which is *hand tight*.

4) The never stick out of the slot that far. When you crank them down, even by hand, the amount it sticks out becomes zero, so pressure is even everywhere.

 

[STAIN]

oil filter

Hi newbie here. I am a Toyota mech.and have been for 15years. Toyota uses o-rings on there filters and when installed correctly they never leak. I have seen many flat type seals leak, more so in extreme cold temp.---10below or so. during cold snaps I will see 3 or 4 a week. Just another piece of info--- cut open a fram or carquest filter sometime and compare to a yammi, toyota, wix or napa premium filter somtime and then tell me if the savings is worth it . I know I won't put one of those on my new RX1

 

[kmer]

There's a couple of things to consider here;

1) Your deformation is in the wrong direction. There would be higher pressure at the center because there is nowhere for the rubber to deform to. You can test this by squeezing a piece of rubber in a vise.

2) Even if it did deform as you suggest, that would effectively be TWO rings instead of one. Ever look at a marine oil seal - they're double ridged.

3) Surface area is more important than pressure. Our goal is to make *contact*, not squeeze the crap out of it. Spec on most cars is "touching + 1/2 to 3/4 turn", which is *hand tight*.

4) The never stick out of the slot that far. When you crank them down, even by hand, the amount it sticks out becomes zero, so pressure is even everywhere.

1) It's not wrong. Try squeezing a block of soft rubber between flat sheets of lexan. Put oil on the block and watch as the oil disappears from the edges first and collects in the centre. Then tell me where there is more force.

2) Agreed, you would have two ridges. The marine seals are still round though, emulating two o-rings not two ridge-rings.

3) Pressure is still important. Without it the ring wouldnt do its job.

4) "Zero" stick out is inconsistent with your point 3). That spec would be more 'touching plus 3/4' turn.

So then, why is it there are so many applications for O-rings if flat rings are better and not just cheaper?

The only ones I can think of for flat-rings are:

* Oil filters
* Canning Jars
* Garden Hoses

 

[kmer]

Re: oil filter

Hi newbie here. I am a Toyota mech.and have been for 15years. Toyota uses o-rings on there filters and when installed correctly they never leak. I have seen many flat type seals leak, more so in extreme cold temp.---10below or so. during cold snaps I will see 3 or 4 a week. Just another piece of info--- cut open a fram or carquest filter sometime and compare to a yammi, toyota, wix or napa premium filter somtime and then tell me if the savings is worth it . I know I won't put one of those on my new RX1

Welcome to the forum.

There is usually a good reason folks like Toyota and Yamaha do things differently than the others - like o-rings. I bet you could tell us about numerous others. 8)

:ORC

 

[RedRX1]

I spent years as an engineer studying/designing seals. Without going into detail, there is no doubt that oring shaped seals are better than lathe cut square seals, lathe cut are much lower cost and therefore used more often. That being said, the problem is most likely not the shape, it is either compression set characteristics with the particular elastimer used or surface finish on one of the surfaces or even cleanliness of the surfaces when the filter was installed.

Aslo, too much force on a rubber seal, especially a square cross section shaped seal, leads to failure as the rubber starts to crack.

 

[kmer]

More uses for flat rings....

* Blenders
* Cheap flashlights
* Leaky thermos lids
* Antique syringes

Uses for o-rings....

* Hydraulic hose fittings
* Inner seal on the RX-1 jackshaft
* Engine Head gaskets
* Pressure washer fittings
* 12' diameter concrete manhole sections
* Modern syringes
* Really good diving watches

 

[kmer]

I spent years as an engineer studying/designing seals. Without going into detail, there is no doubt that oring shaped seals are better than lathe cut square seals, lathe cut are much lower cost and therefore used more often. That being said, the problem is most likely not the shape, it is either compression set characteristics with the particular elastimer used or surface finish on one of the surfaces or even cleanliness of the surfaces when the filter was installed.

Aslo, too much force on a rubber seal, especially a square cross section shaped seal, leads to failure as the rubber starts to crack.

Okay so square seals are easier and lower cost and it's not 'shape' related.... then all they have to do is change them to a better elastimer then there would be no need for o-rings.

 

[RedRX1]

I really doubt the design is a problem here, its probably cleanliness or manufactured quality

 

[kmer]

I really doubt the design is a problem here, its probably cleanliness or manufactured quality

Agreed. There shouldn't be a big problem with using square seals in this case.

Sorry, the last few pages here were just about whether or not o-rings were 'better' than 'square'. You even agreed that o-rings are better. The only thing that could possibly be different between them is 'shape' though. I don't see any other explanation.