Carb spring collar mystery?

[T. Cotten]

Folks,

A great many DLX Schebler and Linkert carburetors have low-speed needle spring collar seats that appear "eroded."
Attached is a comparison of two M352 carburetors, with the eroded example to the left.
352SEAT.jpg
Other models shown below.
Is this a common casting fault? What else could cause this problem?

Please remember that the collar must move freely upon the seat!

Thanks in advance,

....Cotten

[Robert Luland]

Tom, any reason why you couldn't use solder to build up that area and mill it flat again? Being that the body is brass, solder seems to be a perfect mate. Bob L

[T. Cotten]

Bob!

Ordinarily I just mill it enough to provide a surface for the collar to ride upon.

But the mystery remains as to how it occurs.
If it truly is "eroded", then solder won't last long either.

...Cotten

[exeric]

Does the collar show similar wear ?

[T. Cotten]

Folks, Sorry for the late reply again,

But I must jump from one confuser at the shop to see if there is a response,
jump home to my wife's laptop for a quick text response, or boot my semi-ancient Compaq on dial-up to post a photo.

And yes, collar wear occurs, but perhaps one percent of the occurrances of the seat erosion.CLLRWEAR.jpg
The nickeled-but-slightly-dished DLX seat in my previous post implies that this is a casting problem.

Considering the exquisite detail that the rest of Schebler and Linkert castings exhibit, I find this anomally to be disturbing.

...Cotten

[ricmoran]

Tom, that looks like a corrosion issue. What metals are contacting one another?

[T. Cotten]

Rick!

The body is bronze varying from brassy to red.
The collar is brass, nickle or cad plated to begin with.

I am leaning towards a casting fault, based upon the dished Schebler seat in my previous post, which retains its fragile plating.

Although the M352 in my previous post is an extreme example, the problem is very, very common.

Since the collar is a metering orifice for air, one would presume that a decent seal beneath it would be important.
If the collar cannot slide freely, the needle will rub within the orifice, enlarging it.

....Cotten

[ricmoran]

Tom,

Do you see a varying amount of metal erosion on the carb body with the 3 different metals used for the collar? Is their a spring that rests on the collar or what rests agains the collar? Also, the needles play into this as well.

With a heated atmosphere going to cold when the engine is shut down, various metals that are used with the components can set up a flow of electrons due to the devloping condensation at the substrate and the reactivity where the weakest metal will loose substrate in the assemebly. The cororsion attack can be highly localized as well.

All metals excpet the most noble will corrode. There are various forms of corrosion, pit corrosion is one form of this.

When you do a teardown to the carb body, do you see anything that appears to be a flush or flat surface that is a darker color than the carb metal? Then once cleaned, the residue that has been pressed into the metal is gone revelaing what you are seeing? If so, the flush/flat surface seen prior to cleaning could be due to corrosion by product of the spent metal that is held tightly in place by the componenets while assembled.

You have to remember these parts are old and even brass, bronze, nickle and cad plating do corrode, much slower and less than carbon based metals. If there is a spring in the assembly, this aids in setting up a highly charged corrosion cell, the spring corrodes and leaves oxides at the surface of the metal of the spring, and so will the other next up the scale of weaker metals in the assembly over time.

As you already know, corrosion does not take a logical path to the eye, however corrosion will deform metals in various ways and sometimes, that way can be unique to a particular assembly. As mentioned pit corrosion can be highly is highly localized, where in one area the corrosion looks deep, and in other areas it mishapes the metal and largley due to batching process of the molten metals.

In a study doen for USMC regarding brass and it's habit of corrosion in the form of pitts, there is great difficulty in isolating and then removing carbon from the batch process. Carbon tends to isolate itself within batching and once cooled and formed into as an example copper pipe, causes leaks in copper pipes due to pure carbon being reactive to copper and extremely difficult to slow/halt the corrosion issue.

Pit corrosion is often confused with crevice corrosion and with that the two can be in one locale hand in hand so it makes it difficult to analyze which is which unless looked at under highly magnified scope.

Horizontal pit corrosion leaves a deep cavern like hole, where the surface appears normal but inside it looks like a christmas tree profile. Over time, once the metal surface is left without support, the surface can weaken and collapse. At the surface it looks like a cupped form, but then there is also wide and shallw pit corrosion that looks again like a cup with an irregular cup like indentation.

There are many forms of pit corrosion, narrow & deep, eliptical, subsurface, undercutting, subsurface horizontal already mentioned and vertical found within the micro structural orientation of metals and within the cross section of the shape of pits.

This type of corrosion has plagued the nuclear energy and power plant industry for years as highly noble metals are used within the build, but still, corrosion takes it's toll.

Another form of corrosion found is crevice attack under serrated washers with the use of 304 stainless of both the flange, fastening assemblies. This takes the form of the washer itself on the metal of which it is mounted and can be used as an example of reactivity of the various metals used in various assemblies.

If you were to find the issue on new manufactutered carbs, or OEM packed and not used carb, then the form of attack or the lack of proper manufacture could be ID'd.

If anyone out there has a OEM unused carb in it's original container that would aid in isolating the issue.

Until that happens I would suspect that corrosion is the issue at hand.

Also looking at the bottom of the collar, does the metal it rest against look like the contact area of the collar, but somewhat mis - shaped?

[T. Cotten]

Rick asked:
>Do you see a varying amount of metal erosion on the carb body with the 3 different metals used for the collar? <

To be more clear,
The only material that the collars are made of is brass, either nickel plated or cadmium plated.
And neither plating ever survived on the bottom.

>Is their a spring that rests on the collar or what rests agains the collar? Also, the needles play into this as well.<

Yes, however the spring rarely marks the top of the collar.
The needle hopefully is not in contact with the collar orifice.

>There are various forms of corrosion, pit corrosion is one form of this.<

No pits are visible under an eye loupe.
It appears either eroded by abrasive flow, or cast that way.

>When you do a teardown to the carb body, do you see anything that appears to be a flush or flat surface that is a darker color than the carb metal?<

The browning of the bronze is uniform with the rest of the body.

>Then once cleaned, the residue that has been pressed into the metal is gone revelaing what you are seeing?<

There appears to be nothing embedded into the metal.
I shall have to take my stereoscope apart to get a closer look.

>If anyone out there has a OEM unused carb in it's original container that would aid in isolating the issue.<

Only if we find one that is dished!

>Also looking at the bottom of the collar, does the metal it rest against look like the contact area of the collar, but somewhat mis - shaped?<

The worn example in my previous post is a unique example, caused perhaps by a fatigued spring.
Nearly all others, including those found upon dished seats, need only be scrubbed upon some newsprint to bring its bottom to luster.

There are other mysteries about the collar as well.

....Cotten

[ricmoran]

Tom,

I'll do further research with the corrosion manuals we use for our business to try to gain better understanding of what is occuring IF corrosion is the cause. At this point I still suspect this to be the case but have to dig into the reference books on this to better understand what is going on.

On the collar, what does the side that rests against or faces the carb look like? Does that part look fresh, or is there wear/erosion in those areas with the collar?

[T. Cotten]

On the collar, what does the side that rests against or faces the carb look like? Does that part look fresh, or is there wear/erosion in those areas with the collar?

Rick!

Once again,
nearly all spring collars show no wear or damage on their bottom which rests upon the seat, even when the seat is dished.
It is merely a flat, machined surface.

The unique worn example in my previous post appears to have suffered from vibration due to a weak spring.

Please note that no where else on bronze carb bodies does such 'damage' appear, even where dissimilar materials are involved.
(For aluminum bowls and potmetal venturies and bodies, however, corrosion is a serious problem, but nearly always where water would settle.)

....Cotten

[ricmoran]

Tom,

So far, this could be considered:

http://en.wikipedia.org/wiki/Fretting

One point to consider is that I would suppose you see this condition on a few, not all carb bodies. With that, if the years were known for this condition & who was inspecting these for acceptance - QA and what was the criteria too? If that could be understood, & another parameter could be considered, how was the market treating the manufacturer of these parts? If the times were lean, acceptance critera/standard may have been lowered, thus accepting parts that could be sloghtly flawed but good to be used for many years without problems, but not meant to go decades.

The machined surfaces were enough to provide perfomrance but over time, corrosion conditions made an already bad condition worse.

Small trace amounts of corrosion affect parts, possibly curtailing longer life, but yet remains acceptable to the manufacturer as the knew the customer would get the years out of their product.

This happens more frequently than many would like to accept, when it comes to the bottom line, management makes decisions that are geared towards profit, where is the balance point?

For the carb bowl and where water settles I would recommend use of a product known as CarWell CP-90 or Rust COP.

This product has been in use by the military for over a decade and has proven to be the winner in research of perfomance by the military in the category of what is called COTS -consumer off the shelf products. For venturies, since these experience a high flow of air, and sometime moist humid air that can be combined with various chemicals from the atmosphere - erosion corrosion comes into play here, the product would be pushed in performance. Application should be perfomed once every 6 months or in harsh conditions 4 months, depending where/location/evironmental conditions of operation of the engine occurs.

With this product, allowing a 24 hour set time allows the metals to absorb to the substrate, then isolates anode/cathode and reduce rate of corrosion up to 95% - tests performed by US Army Tank and Automotive Command says 92%, test by US Naval Surface Warfare Center state a 95% efficacy in reduction of corrosion. Field tests were conducted for many years for co-oberation of lab tests and the results speak for themselves.....we've perfomed over 90,000 applicaitons to tactical equipment and show the fleet of several thousands pieces of equipment is being preserverd in this harsh climate of Hawaii - 4.5 pH rainfall as water combines with volcano sulfuric dioxides, and also with chlorides from the Pacific Ocean which travel inland several miles from wave and 20 - 30 know wind activity along thge NE facing shore line.

Since Rust COP is a petro based product, highly refined and can be painted over as well, any excess drawn into the engine would not damage anything, some smoking would occur as the excess would be burned of during combustion.

The most difficult condition to gain protection is erosion type corrosion, and this is seen many times inside intake manifolds that have lost good surface to the combination of fuel/air mixture while traveling at many different speeds through the intake system and into the combustion chamber.

[billpedalino]

Cotton - STEREOSCOPE!!!! Boy, that takes me back to my early days of surveying class at Brooklyn Poly!!! - We used them for Photometry and used WWII Army Corps instruments for instruction. I would love to look through YOUR tool collection!

[T. Cotten]

Bill!

I also have a fiber-optic-illuminated arthroscope for inspecting the needle seats, courtesy of a dumpster-picking associate with a Knuckle.

My stereoscope is just a little Tasco that I have had since I was ten or so.

Neither one work with my camera,.. yet.

....Cotten

[ricmoran]

Going to try for images close up? Would like to see what is going on at the surface as that I think would tell the whole story.