Picture of Lifters, Flat, DLC, Roller

[corn_flake]

I was at engine shop today.  The guy was nice enough to let me have few used lifters.  The one with dark tint is with DLC coating.  Notice the uncoated version already have rust developed.  All three lifters were in an engine for unknown number of hours.   I was impressed with the fact that DLC looks almost new.  

[carusoam]

Nice pic, flake!

How is the surface of the roller cam follower?
 

Any idea what engine they had been in? Lycoming or Continental?

Best regards,

-a-

[corn_flake]

I have no idea.  Since I was there to pick up fuel servo, and the shop guy went on and on talking about DLC that solve all cam issue in a Lycoming motor, I asked if I can see the real deal.  He took me to a box a soon-to-be-discarded bin and there we have it here.   

[ArtVandelay]

Nice pic, flake!
How is the surface of the roller cam follower?
 
Any idea what engine they had been in? Lycoming or Continental?
Best regards,
-a-

I think they’re Lycomings, I thought Continental used barrel style lifters, Lycoming used mushroom style. Not sure if that’s true for all.

[Guest]

Most Lycoming engines use the styles shown above. There are a few Lycomings that use a barrel lifter, the famous H2AD in the 172, and the Seminole.  Small Continentals use the mushroom style, while larger ones us the barrel style.

Clarence

[Bartman]

I considered going with roller lifters and and exchange, but after looking into the DLC coated lifters I chose to go that direction with a new Camshaft. Unfortunately my A3B6D engine was removed on 1/31 and shortly after all of my components were sent out to specialty shops the Pandemic hit. Due to unexpected delays at specialty shops and COVID-19 slowing everything down it took a while for all of my engine components to finally come back back in one place.

Planning on beginning installation tomorrow morning  

[N201MKTurbo]

I wonder what the time in service was for the three lifters in the picture? The DLC and roller lifters can't be more than a few years old, the one on the left could have been in service sense the 60s.

[Mooney in Oz]

What is DLC?

[corn_flake]

Diamond Like Coating

[Paul_Havelka]

Technically it’s Diamond-like carbon. It makes a surface harder, slicker and more wear resistant. The friction coefficient against polished steel, camshaft lobes, is fantastic. Been used for years on razor blades, gun parts and many other applications 

Edited May 22, 2020 by Paul_Havelka

[jetdriven]

The DLC lifters can’t get corrosion because they’re not showing any exposed iron. 

[rbridges]

1 hour ago, jetdriven said:

The DLC lifters can’t get corrosion because they’re not showing any exposed iron. 

Is it just a coating?

[Andy95W]

So why doesn't Lycoming put the DLC on the camshaft lobes?

[aviatoreb]

What does DLC mean?  Acronym for...

[Bartman]

16 hours ago, Andy95W said:

So why doesn't Lycoming put the DLC on the camshaft lobes?

They can’t make them too good or they can’t sell parts. LOL

[Hank]

1 hour ago, aviatoreb said:

What does DLC mean?  Acronym for...

 

23 hours ago, Paul_Havelka said:

Technically it’s Diamond-like carbon. It makes a surface harder, slicker and more wear resistant. The friction coefficient against polished steel, camshaft loves, is fantastic. Been used for years on razor blades, gun parts and many other applications 

Reading comprehension is apparently not sufficiently emphasized these days  . . . . .  War Eagle, Erik!!  

[aviatoreb]

52 minutes ago, Hank said:

 

Reading comprehension is apparently not sufficiently emphasized these days  . . . . .  War Eagle, Erik!!  

....oh - I found it!

Darned Luxurious Conditioning.  Thanks corn_flake!  Thanks for nothin' Hank?!

[jetdriven]

22 hours ago, Andy95W said:

So why doesn't Lycoming put the DLC on the camshaft lobes?

IDK, likely so the DLC lifters are backwards compatible with all cams. And it’s not cam lobes rusting and taking out the lifter, it’s the other way. 

[Andy95W]

7 minutes ago, jetdriven said:

IDK, likely so the DLC lifters are backwards compatible with all cams. And it’s not cam lobes rusting and taking out the lifter, it’s the other way. 

I’m sure you’re right.

Still can’t understand why a 1960’s camshaft and lifters can still be good but new ones spall after 400 hours even when flown regularly.

[carusoam]

I gave up on understanding why the 60s cams were so resilient...

I just want to know how to buy one...

In the event for my forever plane isn’t an O... and scales down to an E...  

 

For the Tribologists...

Harder materials have a tendency to wear out the softer materials... (Not an issue if oil is always present)

The larger the difference in hardness between the two parts, the greater the wear... (Important for oil free parts)

The closer the hardness is, the less wear occurs... (Oil or no oil)

The engine owner will want to select the hardness to preferentially select Saving the hard to reach cam over the easy to replace cam followers...
 

All that background leads to the question...

How hard is the DLC compared to the cam lobe surfaces?

Keeping the follower surface from pitting is probably the most important part...

once the follower surfaces become irregular... the oil film, no longer provides enough lubrication...

The lobes are doomed after the oil film breaks down...

PP thoughts only... not a tribologist... or materials scientist...

Best regards,

-a-

[jetdriven]

49 minutes ago, Andy95W said:

I’m sure you’re right.

Still can’t understand why a 1960’s camshaft and lifters can still be good but new ones spall after 400 hours even when flown regularly.

We are doing the annual on my friends 1987 201. 2000 hours, airframe and engine. Guess what,  his “washed filter” metals are lower than mine and his cam and lifters are still good. Never had a cylinder off. Somewhere after 1991 or 1993, is the problem.  
My old boss’s Arrow also had a 1987 Mattituck field overhaul. It was running  great until last year, it was still running great, but he decided to overhaul it because it had 2200 and it was that old.

[Nukemzzz]

We use DLC coatings a lot in our designs at my day job. 

DLC is an extremely hard coating so it wears slower.  Beyond the anti-corrosion benefits, it also lowers friction between the two parts and friction plays a big part in spalling. It does this by causing the two parts in contact to no longer be metalugically similar. Steel on steel under high contact loads has an adhesive component to the Friction because the two parts want to fuse together. This is how galling occurs.  DLC on steel breaks this tendency.

DLC coating isn’t cheap, and it’s tricky to only coat specific regions of a part.  A camshaft lobe is only under high load on the outer base circle so this is the only region that would benefit.  It would be nearly impossible to only coat those regions and so the tappets are coated instead.  It would be a waste of money to coat the whole cam and coating both part provides no benefit.  It would probably make things less robust.

This isn’t a trouble free solution. It’s very tricky to get the coating to adhere and then to survive high temps. But, if done right it’s hard to beat. 

I’m about to put these DLC lifters in my A1A.

Edited May 23, 2020 by Nukemzzz

[glafaille]

On 5/22/2020 at 6:13 PM, Andy95W said:

I’m sure you’re right.

Still can’t understand why a 1960’s camshaft and lifters can still be good but new ones spall after 400 hours even when flown regularly.

Many industries have been negatively affected by mounting EPA regulations enacted over the past several decades affecting the use of certain chemicals and procedures used in the manufacture of all sorts of products.  Companies are forced to alter their products to comply.  It would not surprise me to learn that engine manufacturing is one of those industries.

The unintended consequences of government regulations are rarely considered  or reported.

Edited May 24, 2020 by glafaille

[Andy95W]

Or they were just trying to save a buck by changing to a cheaper process or supplier.

[N201MKTurbo]

Let’s see, DLC can crack letting corrosion in. Spalling is caused by sub surface cracks. How would DLC stop this?

how does DLC hold an oil film?  Does the oil bead up on it and run off or does oil wet DLC?

These things are never as cut and dried as a lot of people think.