Hardening camshafts

[smpstech]

Hi all,

I am starting to progress along on my 2 cylinder engine build. I have a question regarding the camshaft though. I plan on making it out of either O1 or A2 tool steel. I was wondering how important it is to harden the metal on this scale. It seems to me that tool steel is already quite hard and the valve springs used in model engines are not very stiff, so the wear should be minimal and therefore hardening not required. I ask because time is of the essence in this build and I am running out of it. If I harden the steel it is only going to add time to where I will also need to setup one of the CNC mills to grind the camshaft, which is simply not possible with the current time frame.

 

[Mechanicboy]

In generally no necessary to harden the camshaft. The steel is hard enough. The risk is the camshaft can be bended by hardening process.

 

[gbritnell]

I make my camshafts from W-1 drill rod. It's a little easier to cut then O-1 and certainly a lot easier to cut then A-2. I machine and polish it and make my lifters from the same material but harden them. You never want 2 pieces of the same material rubbing against each other. Some of my engines have almost 100 hours of running time on them with negligible wear on the lobes. If you were to harden the cam you would need to leave stock on it and grind it to the finish dimensions because it will warp a little. The only other option for hardened lobes is to make them separately and pin them to the shaft. This procedure works for simple cams but gets kind of complicated for multi-cylinder engines.
gbritnell

 

[stevehuckss396]

I use O1 for all my cams big and small. My lifters are 12L14.

 

[Mechanicboy]

I has 4 stroke gas engine, the cam was made of high tensile steel (never hardened) and lifter of cast iron. No problem with abration since there is enough oil present.

 

[John Rus]

For an enigne with generous lobe surfaces and low power output you can get away without hardening, but it will last longer if you do.

Cheers,
John.

 

[BronxFigs]

While we are on the subject.... is it "better" to have hardened lobes and "softer' lifters? My logic is this: Wouldn't it be easier to re-machine the lifters as opposed to remaking a more difficult, camshaft that has excessive wear on the lobes? Would using different materials like, e.g. .... O1 for the shaft and 12L14 for the lifters be just as effective?

Or is this a problem rarely seen in model engines? Just asking.


Frank

 

[stevehuckss396]

Wouldn't it be easier to re-machine the lifters as opposed to remaking a more difficult, camshaft that has excessive wear on the lobes? Would using different materials like, e.g. .... O1 for the shaft and 12L14 for the lifters be just as effective?

Or is this a problem rarely seen in model engines? Just asking.


Frank

That's my theory. Lifters should be softer than the cam. The reality of it is, for the few times they get run a year and the 3 lbs of spring pressure they see, as long as you make them out of any steel and they get proper oil, they will outlast who ever builds them. Were not driving them back and fourth to work. Like George said, "You never want 2 pieces of the same material rubbing against each other"

 

[Till]

I didn't look up what you 2cyl engine is made for. For RC planes, boats or cars I recommend to heat-treat the cams. Same for piston rings. If build to run occasionally on exhibitions heat-treatment is not necessary.

 

[smpstech]

That's my theory. Lifters should be softer than the cam. The reality of it is, for the few times they get run a year and the 3 lbs of spring pressure they see, as long as you make them out of any steel and they get proper oil, they will outlast who ever builds them. Were not driving them back and fourth to work. Like George said, "You never want 2 pieces of the same material rubbing against each other"

That was my theory. I am planning on making the valves and camshaft out of O1 and the "lifters" out of brass. It's a very simple flathead engine, so the camshaft acts directly on the valves, and the "lifters" will really just be a small piece of brass that will press fit over the end of the valve and also retain the valve spring.

 

[John Rus]

My other thought on soft lifters is the wear is consistent along the whole cycle of the valve where as if the cam was softer the outer most lobes would see the most wear and have inconsistent valve movement.

Soft lifters would be my choice,
John.

 

[stevehuckss396]

That was my theory. I am planning on making the valves and camshaft out of O1 and the "lifters" out of brass. It's a very simple flathead engine, so the camshaft acts directly on the valves, and the "lifters" will really just be a small piece of brass that will press fit over the end of the valve and also retain the valve spring.

You might be happier with bronze

 

[John Rus]

+1 On bronze.

John.

 

[BronxFigs]

Thanks, for addressing the questions about hardening, lobe/lifter wear, heat-treating, and general theory, etc.

Re: #8.....
Steve, you are so right....these model engines will outlast all of us. But, it would be nice if future admirers of all our creations would think that we were clever engineers who used the correct material selection for a given part. : )


Frank