heat cycling

[Doc Brown]

Originally Posted by SS109

Sorry Doc. Wasn't trying to upset you or anyone else. I think maybe a little was lost in how I worded things. That said, we cool!

No problem SS109, everything's fine

Originally Posted by Jakobi

https://www.youtube.com/watch?v=c2eWHNSaSZU pSSST!!! the barra!

What do you think on the matter Doc?

I like to keep things simple..

Buy quality parts, measure tolerances on assembly, throw it together.
Run to test for leaks, etc. Short test ride using some load on acceleration and deceleration to start bedding rings, and then ride it as per normal.

As said its very hard for me to explain complicated things in English. However, some people say they run in their engines other's say that was usually done in stone age and it's not necessary anymore as materials and tolerances are so much better today. Let's leave that open and everyone should decide for himself.

Concerning different materials it is well known that they have different thermal expansion coefficients hence tolerances may vary a tiny bit.

Additionally, and that is not common knowledge many materials come from the manufacturer and their molecular structure is not finally directed (hope thats the word). Hence they have internal stresses that will go away during the first heat cycles. The molecular structure gets its final condition and will remain like this until the end of the life cycle. That especially applies for any casted materials but also to forged pistons and other components.

I am not so sure if I found the right words. Till today I haven't found a good technical dictionary, something that covers especially automotive and scientific phrases and vocabulary...

[(F5)]

The piston get quite hot as there is a fire burning above it.
The watercooled parts are quite held around 60 to 70degC in light to mid use, and the rest of the engine doesn't get much hotter. Too hot to hold onto, but not hot enough to burn you.

So how much is this heat treatment happens in ally or steel at 80degC?

[Doc Brown]

The engine, abused in hard enduro gets far hotter than 80 degrees, sometimes over 120.
However, I can't answer your question. Sorry.

[swazi_matt]

i think the real-world benefit of heat cycling is to check that everything has been put together properly to avoid any real damage (so not really heat cycling, but more a careful test run). I have seen national races where they have replaced the engine in the pits and the warmup was from there to the end of the pit lane then full taps and the engine was fine for the remaining 200km desert race

[Jakobi]

Originally Posted by Doc Brown

No problem SS109, everything's fine



As said its very hard for me to explain complicated things in English. However, some people say they run in their engines other's say that was usually done in stone age and it's not necessary anymore as materials and tolerances are so much better today. Let's leave that open and everyone should decide for himself.

Concerning different materials it is well known that they have different thermal expansion coefficients hence tolerances may vary a tiny bit.

Additionally, and that is not common knowledge many materials come from the manufacturer and their molecular structure is not finally directed (hope thats the word). Hence they have internal stresses that will go away during the first heat cycles. The molecular structure gets its final condition and will remain like this until the end of the life cycle. That especially applies for any casted materials but also to forged pistons and other components.

I am not so sure if I found the right words. Till today I haven't found a good technical dictionary, something that covers especially automotive and scientific phrases and vocabulary...

just heating and cooling a piston is not gonna keep you from seizing.

you must have lubrication.
you must have clearance.

run em' tight they stick.....run em dry, they stick. clearance is the thing to watch. most guys grab a piston and shove it in the bore....yep it fits. when you get into bigger bores you need bigger clearances. a little money spent on mics will pay for itself in spades.

The piston changes with use. Run one long enough it wears out, it stresses, it fails. I disagree that once a break in is done, the piston is good to go. Tighter tolerances need a little more mechanical sympathy during break in.

[(F5)]

So not the 3-400degC usually used for heat treatment? Must be a special Luke warm treatment process. You then can quench it in liquid of 80degC..

You probably think I'm a dick right now, but sometimes you have to reevaluate Its always been done this way practice and ask Why?

[Doc Brown]

Originally Posted by Jakobi

just heating and cooling a piston is not gonna keep you from seizing.

you must have lubrication.
you must have clearance.

run em' tight they stick.....run em dry, they stick. clearance is the thing to watch. most guys grab a piston and shove it in the bore....yep it fits. when you get into bigger bores you need bigger clearances. a little money spent on mics will pay for itself in spades.

The piston changes with use. Run one long enough it wears out, it stresses, it fails. I disagree that once a break in is done, the piston is good to go. Tighter tolerances need a little more mechanical sympathy during break in.

All you say is 100% right and I fully agree with it. But it has nothing to do with heat cycling or the effect that heat has to different materials.

[Doc Brown]

Originally Posted by (F5)

So not the 3-400degC usually used for heat treatment? Must be a special Luke warm treatment process. You then can quench it in liquid of 80degC..

You probably think I'm a dick right now, but sometimes you have to reevaluate Its always been done this way practice and ask Why?

Its not my fault if you don't understand the difference between heat treatment of metals and the effect that heat cycling has to metals that never have been heat treated.

[(F5)]

Is that somewhere near the harmonic convergence plateau where the aura aligns?

[Jakobi]

Originally Posted by Doc Brown

All you say is 100% right and I fully agree with it. But it has nothing to do with heat cycling or the effect that heat has to different materials.

I don't think anyone here is arguing the point that heat can change the structure of metals. More to the point, what question are you asking?

A forged piston has seen some heat already, both during forging, during, machining, finishing, etc. And will surely see more in use. Is there a specific break in time which leads to optimal structure? At which point does it go beyond optimal and fatigue? How does this matter to us?

I don't care about heat cycling specifically. That happens when I ride. What I care about is a proper warm up, an adequate cooling system with no leaks, no air leaks etc. From there once I've confirmed the engine is sound after any work my focus moves into generating enough load to sufficiently bed the rings in.

How are airplane engines broken in? Some good reading on the matter if you go looking.