Permatex form a gasket sealant question?

[raygreenwood]

[raygreenwood]

Ah.....its in my photo bucket. I will post them to this thread in the am. Ray

[pablovent]

In my country sold a sealant for motorcycle cases made in Brazil very similar in appearance to neoprene, smell, very similar color, but it is based on Aromatic solvent, ketones, nitrile drunk.... dark honey colour.
.

[raygreenwood]

Yes....I have seen similar. It is very close ro Indian,head brand. Actually,quite good...but not great at filling imperfections, gaps or grooves and has less flex range if needed. Very hard to remove. Ray

[madmike]

Yamabond/Hondabond/1194 ThreeBond/and Loctite Moto Seal. seals great
easy clean up ,
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[pablovent]

[raygreenwood]

So this is “A” method of putting on RTV evenly and very thin. If you don’t need it this thin….say like for cylinder base sealing….and you have patience, are diligent and clean….you can do this technique with your finger by rapidly “stippling” the surface.

So what is this and why does it work? Not to get too scientific on you….but this is what I work with for a living…. It works because virtually all of what are called “non-Newtonian” liquids or pastes (and “most” RTV are somewhat Newtonian) …..will shear thin when subjected to shear stress.

Simply put….as I roll out or squeeze out the RTV….it will drop or reduce in viscosity until it gets stable in viscosity….and will produce a film of a uniform thickness....with a fairy uniform “knap” or surface texture.

NOTE: Because these films are very thin…..and you are imparting moisture into them as you roll them out (and moisture is part of the RTV curing mechanism) they dry incredibly fast….like in minutes….not hours. So once you reach stable film thickness…..if you get lazy and slow…..as you keep rolling and the RTV starts curing….the viscosity increases and the film starts getting thicker with a rougher surface texture.


As a note….aside from the use of RTV’s by automotive manufacturers as “gap fillers” and form-a-gasket makers…wherein they inject the RTV into a groove….say in a valve cover…and let it harden….a great many OEM manufacturers, industrial RTV users etc….apply RTV either in a roll coat method to do exactly what I am doing in these pictures….or it is screen printed, gravure or flexo printed onto surfaces to get exacting tolerances and thickness.

The gist of it:

This is typically what one gets even when carefully “gooping” in on by normal methods. Careful gets you about .003” to .005” RTV thickness….BUT…because the viscosity is high and the RTV quickly “locks up” hydraulically when you squeeze the two surfaces together….the actual gap between parts can be .001”-.002” larger than it should be.

When we shear thin the RTV the total layer thickness on each part is about 1/10 or thinner than normal application methods and has a uniform texture…which is critical to getting thinnest fit.

Note: uniform surface peaks/texture fits together to crush and form a layer with many micro barriers inside the film layer to resist lateral oil flow.

Because the texture peaks are thin and of lower volume than a sheet or film of RTV, they can spread out laterally farther and thinner than a continuous film…allowing the two metal parts to get closer together before the RTV creates a hydraulic “block”.

The final squeeze together gets you an RTV layer of less than .001” thick…typically about .0005”.

Since there is less RTV to flex it is much less susceptible to vibrational flex and tearing and lateral invasion of oil or vacuum or pressure perforation

Clean case. This one was just done for the photos so I am not actually assembling and engine here. Normally I pull the dowel pins for this and tap them back in shortly before contacting the case together. You “CAN” put it on both sides of the case….but is easier on an engine case to put the crank and rods in one side of the case…and then put a double layer on the other side and then contact them.

I use a sheet of glass or Plexiglas..…the flatter the better. I put an X on the back side of the glass with sharpie so you can see how thin this rolls the RTV out.

Put a couple of stripes of RTV down.

I just used an $8 natural rubber printmaking roller (called a Brayer)…hobby lobby. Softer and harder rollers give different texture height. I have some expensive ones I don’t use for RTV. Once you start rolling the RTV….the roller will first kind of “ski” over the RTV without rolling. About 8-10 strokes and it thins enough that it starts rolling. You can buy these 1-3” wide as well so they are easy to use on a case.

Getting thinner…see the X underneath?

Thinner still and getting to the point where there are no more visible changes. Note the “X” and note the uniform texture on the RTV on the roller and glass.

So how do I know how thick this is? Because I have tools to measure it.

This is a precision coating gauge….accurate to 1 micron. You can see in the lower picture above…. the thickness….and I ran several stripes….is right at 1.8µ (1.8 microns). There are 25.4µ to each .001”….get the picture of how thin and uniform this is?

NOTE: you do not need this gauge to do this. The nice thing is that a uniform liquid or paste at a given temperature will always shear out uniformly. With no gauges you could do this with 10 different tubes of RTV on 10 different days and the film thickness will usually be within a few microns of each other.

I use the roller to transfer the RTV to the case parting line. Work quickly with frequent rolls over the sheet of glass to pick up more RTV.

Notice that I put a Sharpie mark on the bare aluminum….so you can see that the RTV is so thin and even that it’s transparent.

Note the uniform texture.

This method on both surfaces works fantastic on transmission cases. Just like adhesive…..RTV is much stronger and has greater film strength…the thinner it is (up to a point).
Ray

[pablovent]

WOW...That´s an explanation!!

[303epps]

x2

[raygreenwood]

Thanks.
Oh...forgot to mention......when the surfaces are machined well and the application is uniform and thin......this works just about as well when you coat both maying surfaces....and let it completely dry. It makes a very thin immobile gasket.

It works well enough dry that I can't quite quantify how much better bolting the two surfaces together wet works.
I'm
The real advantage of putting this on very thin and even with very fine uniform texture ....and letting it dry first before mating the surfaces..... is that the RTV does not displaced or get squeezed out....so it actually acts like a rigid gasket with a pliable surface.

To use it dry.....you do need to make sure the rolled on layers are as thin as possible....as it,will only crush down about 40% of its thickness. Ray

[MConstable]

Holy crap.
Ok then, thank you Ray!!

[mcmscott]

http://gasgacinch.com/


Or you could just use some of this.

Some one needs to get a life, Seriously
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[raygreenwood]

[Asleep@thewheel]

1500$/day!! Need an apprentice? 😁

[pablovent]

Very satisfied with the post contributions, I can see that the application technique is very important......... but of all RTV´s colour in the market, which better supports the engine oil and best metal adherence? .....Yamabond 5 is a RTV formulated???....... I have also curious about the Gasgacinch texture and components type, it is similar to the gasket indian or Permatex 2 form a gasket sealant?

[raygreenwood]

By the way...mcmscott...my apologies for the asshole comment...even though it was still delivered with a smile. I am used to your personality...no big deal. Sometimes I just pop off a bit....wine was involved.


So everyone understands what the ACTUAL point of my post was….nd there was a point....it was in response to John’s post that RTV was not to be used on the case joint… and in general…with poor/incorrect application methods..…he is exactly right. Its dangerous when its sloppily gooped on. It gets places it should not.

My point is that its not that its the wrong product...but simply that it should not be sloppily gooped on.

Those pictures came from a short proof of concept exercise back in about 2010 for one of my clients who I cannot name due to a long running Non-disclosure agreement…but suffice to say they were printing RTV’s to make case sealing gaskets for the steering transfer case of …shall we say….an earth moving machine they build...that is somewhere between a road grader and a tractor (industrial and leave it at that). That company makes sealing products for MANY automotive companies.

They did not understand why the RTV was printable one moment and not the next or the variations they were introducing due to the shear processes in printing. Roller transfer was actually one of teh simpler ways of showing shear thinning effect....instead of making a screen, plate or engraved roller to prove the point.

The VW case joint is similar in tolerances and it was on hand so I rolled out some RTV to show how the material could be manipulated. Where the conversation led to..…a series of plant visit….rheometer testing, print testing, modified RTV and material testing and changes to their proces.

I can’t show you the pictures and videos of that end of it….but “could” provide some of the data tables from the wide range of commonly available sealants and a large group of in house formulated RTV’s because the NDA on that part of the project has expired. Might have to blank out some names.

My point was…..not to say use one product or brand of RTV over another. Most (not all) RTV’s can be worked this way and virtually all are different in exactly how well they shear out and what texture and film thickness they produce.

Right now I have some pourable two part RTV that…because it starts out thinner...cannot be rolled out but can be printed. At over 800F its awesome stuff….but at over $100 a half pound….worthless to an automotive use.

Some of the suggested products like Gaskacinch http://gasgacinch.com/wp-content/uploads/2016/01/SDS.pdf and Indian head are superb….they start out thin….dry even thinner and due to the Naptha for instance in gasgacinch…are anerobic and pull themselves into microscopic fissures…awesome….but have very low elasticity and low solids and are personally not what I use for an engine case whose surface is less than perfect from years of abuse. they just do not fill gaps as well That why I use RTV’s ….when necessary.

The whole point was that with proper application....an RTV product works very well in a gasketless case sealing position. I have sealed many engine cases with RTV's. Applied properly...they do not leak.

Ray

[mcmscott]

My oppoligies for sounding like an ass hole, beer may have been involved

My theory is, if something works, why change it? I have used gasgacinch since the early 80's, without a single problem. I know it works perfect without question every time. While I might try something different on something I'm doing for myself, I only use what I know ,without question, what works on my customers cars.
You have some very educational posts, I enjoy reading them, but I "sometimes" have a rash personality
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There are no stupid questions, only stupid people,

68 Ghia
67 T-1
65 Notch
02 Mexican beetle
74 Thing
15 Long travel rail
07 Nomad
05 f-250

[PumaVW79]

Deleted (off topic)

[raygreenwood]

[mcmscott]