Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
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.......See, that statement just baffles me. I've never encountered a team that said, "We'd turn more RPMs, but our conrods would break"......I'm aware of a motor that has a mean piston speed of 7540 fpm, 38.3 m/s. EN30B crankshaft ..... .
If you are baffled by F=ma thats an issue, as its been known since the year 1688 and if you`re going to spout engine figures like that you better have a reference for it.
Quoting mean piston speeds is fairly meaningless in terms of rod stress, as you need to know the instantanious acelleration figures over the complete crank cycle to calculate stress. This requires that you actually know what you`re doing, which is why amateurs do things like saying "these pistons are good for such and such mean piston speed", this sort of "I reckon..." design method descends from a time when people didnt have computers and didnt know enough maths to do it properly. Its ok to compare a speed increase of the same engine but gets almost meaningless otherwise as the resultant stress is dependant on rod and piston mass, bore-crank offset etc etc etc, which change radically from engine to engine.
Secondly here is a selection of scientific papers on engine design. I really think you ought to read more before you post anything else claiming to be telling others about how connecting rods impact engine performance, given that you have clearly never designed one.
I like reading your posts, I actually think the forum is honoured that you take your time. I also suspect that as complicated as your posts seem they are watered down and condensed for a lay audience.When the worlds most advanced racing engine firms have invited me all over the planet to present my engine research to their engineers, they were only iterested in WHAT I am bringing to the table and have never asked my age before inviting me to their premises, so thats a new one!
Once again you've utterly misunderstood, misrepresentated / willfully ignored everything I've told you.
If you refuse to learn or listen, there is literally nothing to be gained in continuing, is there.
When the worlds most advanced racing engine firms have invited me all over the planet to present my engine research to their engineers, they were only iterested in WHAT I am bringing to the table and have never asked my age before inviting me to their premises, so thats a new one!
Once again you've utterly misunderstood, misrepresentated / willfully ignored everything I've told you.
If you refuse to learn or listen, there is literally nothing to be gained in continuing, is there.
Well, then please make your case, rather than just throwing out a few papers that don't contradict my initial point, which was that mean piston speed is a better basis of comparing apples to oranges than rpm.
You have a reputation here for being able to explain the fine points of engine design to a barmaid (or at least, to a few history buffs), and it would give me great pleasure to see you live up to that reputation.
Thats the best I can to do in any reasonable fashion to answer your point, and if that it doesnt work for you - you`re out of luck, as to do more I`d have to design an engine with you sitting here at my PC whilst I explain it step by step.
I do not understand why you think finding a dragster engine with high mean piston speed means F=ma doesnt apply to engines. It has a redline, just a higher one than would have been possible 50 years ago.
The improvement in materials simply allows them to run more rpm and more boost, but this is simply a HIGHER limit, there are very strict rpm and boost limits even a top-fuel car is limited to.
Ok, now I can see where you're coming from, and there is very little I would disagree with in that last post of yours.