I doubt its the internal pressure, if it was, the engines wouldnt last very long.
The engine is the tallest part on 1/8th scale cars. With the wedge body, when one car hits another, the car that was hit probably hits the engines head, and thats when the crankcase breaks IMO.

You also have to take into consideration the inertia forces invloved, the car that is coming down the straight stops pretty quick when it hits the car other car.

It would be neat if some RC car company would be willing to donate a car to see how hard a car traveling at those speeds hits. I've heard of people breacking legs when they get hit.

I read the post to say that the other car was upside down. His car hit the upside down car. The upside down car just go punted while his car got the motor case busted. I can see this happening. The lola body leaves the engine open for direct contact. Happened to a friend with a 235mm. He hit a 4x12 board straight on at the end of the straight. His car blew a hole through the wood about 2 inches tall. The hole was too low for his engine so it tore the head and the top half of the case right off.

If an 8 lb bowling ball hit the side of a car at 70 what would the car look like? my guess is there would one hell of a dent in it.

Peter, why don't you finish the story of the weekend by including the rod that Billy broke while borrowing your .12 RB?

Tough weekend...

G/day Guys
Just some quick calcs. to dispell any internal explosion myths !
The force from dissipating the energy in a crash with a 2600 gram (2.6 kg) car travelling at 75 mph is :-
stopping in 1 sec - 9kg.
stopping in .1 sec - 88kg.
stopping in .01 sec - 888kg.
so if it hits a solid steel barrier that doesn't budge - 1000kg would be possible. Hitting another car could be anything from 50 to 200 kg of force! That's why the engines shatter.
It's also why I used to hate marshalling the straight or turn off the straight !
Regards Richard

Lol that sucks but is funny

Just talking about this aspect, an R/C could quiet easily break your leg then couldn't it... ouch...

yeah its a heck of an impact, the roll bar in front of the engine left its imprint on the head. i mean a straight line on every cooling fin, now thats an impact, oh yeah never did find that roll bar either. Peter

may be we can look at it from another angle. At 16.8mm stroke, assuming that the piston is traveling in constant speed (which it is not, as in each stroke there is a change of direction). At 35,000rpm, your piston is traveling at 70.6km/hr inside your engine. Add that to a serious impact, almost any crank case is going to crack.

Novarossi did put out a disclaimer in the Serpent Veteq days... where they did not design their engine to be part of the stress member in the chassis. If the impact is on the engine, it will give the same effect.

Hmmm.... this sounds silly, but anyone thought of installing a little roll cage for the engine....?? Some aftermarket made them for 1/8th monster truck.