.. I would guess you'd pull the carb and possibly o-ring on the backplate...

Maybe next version has an oil pump and filter???..

only crank case, piston, sleeve and rod are assembled, no head button, just a special plate to hold the sleeve in.

The heat and rpm can be varied, 200c and 33,000rpm max

I dont see the point, motors run just fine the way we have been braking them in for the last 4 decades. I dont even believe in "pre run" motors, I tried one and it didnt last, so I just went back the tried and true method.

Id tend to agree with you nitro dude. To me the force on the conrod is all wrong. A conrod isn't designed to take force pulling the piston down from the sleeve it's designed to be pushed down by the ignition cycle. I really don't see the point and it is bound to be a hugely expensive service! I think I'll stick to the tried and tested process of run in bench with propeller followed by on track.

+1 No need to re-invent the wheel. But it does get a couple of cool points


Pass you soon...

I'll do break in the old way of 35yrs.

Its just another tool. Guy using heatguns and this. Heat up the whole engine to 195deg and turning it over. I normal running condition. 500 rpm's is enough. Just change direction of stepper motor. All us guys see the same thing. Tight pinch. After break-in pinch is less you don't use the heat gun anymore.

Ways of tight pinch and not using heatgun.

Its another tool, use it as is or not.

Actually the conrod does experience a very large pull force during normal running. Compression alone, and even combined with combustion are not nearly enough force to slow down the piston miving upward at 40k rpm!

Just look at a broken conrod. It is due to the bottom eye splitting open. How is that possible without a pull force?

The service is not that expensive once you factor in the fuel cost of a normal break in.

That`s why the loads endured during break-in using our method are so low, the engine is not spinning at 40k rpm. Actual real life testing shown no wear at the conrod, so no need to replace after break-in.

The splitting of the conrod is always due to fatique of the material, almost never due to stresses that are to high. And yes, it`s fatique during tension stresses.

Dont forget to put a fresh set of tyres (or better two) on the car during break-in, and the replace conrod afterwards. So with this method it is not needed to buy fuel, tyres or a conrod. Pretty cheap if you ask me.

Do not forget the wasted practise time.....

My open question is the temperature distribution. In a normal operation you will never have al constant temperature on all areas of the piston and sleeve.
The piston and sleeve are hotter on the exhaust side and on top of the piston.
I'm an engine developer for 1:1 diesel engines and our pistons are tapered in axial direction and oval in radial direction, to compensate the different temperatures. Nitro engines are produced with a pinch. During break in, the piston gets it's final geometry. If you run that process with a different temerature distribution to normal operation, the piston may get a "wrong" geometry.

Why do you think the engines are designed with a pinch? I think if there would be a constant temerature during operation, it would be easy to calculate the thermal expansion of piston and sleeve and produce the piston and sleeve with tight tolerances and no break in would be required at all.


My personal expectation is, that a well done classical break in will result in better performance than the break in dutch method.

Understand what you mean, think that the difference in temperature will be minimal due to the smal dimensions of the piston and the thermal expansion will be homogeneous. In the bigger diesel engines the heatzones will be more present and differential thermal expansion is indeed a factor.

What is the diameter of pistons you are designing?

The break-in does 95% of the work, after driving for 15 minutes the final fit is made on the engine. It`s just a easy way to get it done.

Understand were you coming from, but experience has shown a good fit of piston and liner. We have offered al our club members a free break-in and all engines are running great, they are happy..

The engines are designed with a pinch because the max. piston acceleration by 45.000 rpm is far to high for piston rings.

The calculation is indeed pretty simple and linear, bellow a .12 piston in FEM analyses. A temperature difference of 50 degree celcius for a 120 degree radial angle of the exhaust direction. You can see a resultant displacement due to thermal expansion. The difference in around 0.002 mm between the exhaust and intake direction of the piston.

Think producing a piston with a ovality of 0.002mm would be expensive. The differential thermal expansion is just not as big as we all would expect.
My expectation is that the temperature difference is a lot smaller then the 50 degrees celcius, so the expention is also a lot smaller.
The final ovality is done by driving the car the first 15 minutes.

But experience really shows more then all this discussion (saying that on a forum..lol). I would advice you al to make a small machine, it`s very easy to do and makes life easy for break-in an engine.

Remember, I`m just like you all a guy who likes to race, i like to design all kinds of machines and hop-ups for my own cars. Don`t care if i sell a lot of products or break-in engines...it`s not my job, have a normal engineering job for 1:1 models.

But i do like to defend my design on a forum...

Yeah, but we al know that's the difference between winning and finishing 2nd Roy!

Hahhahahahaha, you smartnose..
From now on you are not allowed to use my break-in machine anymore for free..even if you pay you are not allowed anymore...heee...even if you pay double you are not allowed anymore.

You are just a old dinosaur that cant handle change too fast...lol..