Plastic engine cams

[bmac2]

I knew that they are using a lot of plastic gears in small engines but I didn’t know that they are making the cam lobes out of plastic.

[ame]https://www.youtube.com/watch?v=iL7xWCAlczU[/ame]

Model engines (generally) don’t run under any load so with some of the filaments out there now could 3D printed gears and cams be on our horizon?

 

[t.l.a.r. eng]

One of the little 4-cycle weedeater powerheads I have has a plastic camshaft in it.

It would seem plausable if there is little spring seat pressure against the cam for our models. But as my dad always said "plastic belongs in toys" :rant:

The Briggs in the video is a classic example. There is no earthly need for a plastic cam gear in a small engine. GM used to allways say they used plastic coated timing sprockets to "limit chain noise" ?? Never heard a chain make noise with an iron sprocket. Just a classic failure point to keep economy rolling.:wall:

 

[John S]

Briggs and Scrap'em, says it all

 

[vederstein]

I'm not entirely against the idea of plastic engine components. A material, any material will have its limits. It all depends on how it's applied.

Do any of you have issues flying on a Boeing 787 because it's made of carbon fiber (which is really another type of plastic)? Most hand held drills, both high and low end, are made of plastic nowdays. The 1996 through 2006 Ford Taurus had a front suspension link made of plastic with molded in bushings. They won an industry award for the design.

A whole hell of a lot things are made from aluminum. Unlike steel, aluminum has no endurance limit (for steel roughly 1/3 of its tensile limit) so it will always eventually fatigue fail. The engineering part is using the material to meet the specifications which, cost is always a deciding factor.

I watched the video and the focus was on the plastic gears and cams. The metal push rod was bent as well. This is conjecture, but perhaps root cause of failure was further up the valve train causing the system to lock up and the sheared timing gear was the end result.

The real question is not that a plastic timing gear failed, but what caused it to be overstressed.

...Ved.

 

[Hopper]

Pretty soon, they won't have cams at all. Solenoid operated valves controlled by the ECU computer thingamee are already in use on some marine engines. Only a matter of time...

 

[skyline1]

Hi All

Having just built a 3D printer I am using it for printing low stressed structural components and the range of materials they can use is increasing all the time.

Some of the components for the printers themselves are 3D printed, indeed this is the goal of the Reprap Project to make the things self replicating.

So why not other things, and they are ideal for making foundry patterns.

Modified ones are used for printing chocolate so pattern wax is a possibility, (probably already being done)

Best Regards Mark

 

[bmac2]

Hi Mark
I know a guy that’s tried lost PLA casting with pretty good results.
This might be the ultimate for now, but I’m sure it’s well out of my price range.

[ame]https://www.youtube.com/watch?v=5pGwd0ZKuBU[/ame]

 

[skyline1]

Hi Bob

Wow that's some spectacular stuff.

Well out of my price range too but who knows, ten years down the road us hobbyists will probably have them, for reasonable prices.

3D printing seems to be the "pet technology" at the moment and seems to be really catching on.

I was thinking about using PLA as a "lost wax medium" it's melting point is quite low (it needs to be fairly low for 3d printing).

But before I do I will have to recommission my "backyard foundry" it is likely to be a fairly big job and like most I've more than enough projects on at the moment.

Best Regards Mark