different piston design for IC engine

Discussion in 'General Engine Discussion' started by camnefdt, Feb 10, 2013.

  1. Feb 10, 2013 #1

    camnefdt

    camnefdt

    camnefdt

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    I am yet to build my first anything on a lathe or milling machine, but am a super technically minded young individual driven by mechanics and general engineering.

    At the moment i am busy designing out a long term project for one day when i have the experience and money to invest in such a project.

    The question i have is, has anybody considered using a more modernized design for a piston over the good old straight long cylinder?

    something along the lines of this. . .
    Piston_Minardi_1.jpg

    This one is from an F1 car but the concept is there.

    So has anybody tried one of these for a scaled IC or even considered doing this before?
     
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  2. Feb 10, 2013 #2

    stevehuckss396

    stevehuckss396

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    I think myself I will stick to the long cylinder. Stuff like you show are designed for minimum friction and flat out performance. They are also designed to last one race and get tossed out. As my engines are not designed to go real fast I will most likely stick with what I see in production engines that are designed to run for hundreds of thousands of miles.
     
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  3. Feb 10, 2013 #3

    MuellerNick

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    F1 budgets are so low, the have to save material wherever they can to cut costs. :)


    Nick
     
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  4. Feb 10, 2013 #4

    wildun

    wildun

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  5. Feb 10, 2013 #5

    Swifty

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    I can see that type of piston works, but goes against design principles where the piston should be at least as long as it is in diameter, preferably longer. This is to stop the piston cocking in the cylinder.

    Paul.
     
  6. Feb 11, 2013 #6

    camnefdt

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    you are 100% correct in saying that this is purely a performance 'mod' piston. But in recent times, similiar designs (not as narrow) are being used in production performance cars purely for the fact that they weigh less and have less friction.

    wildun
    i dont plan to take shortcuts to achieve my goal, will start off with basics and make my up from there, i just love learning about new things mechanically and as a challenge to myself, am designing out a purely performance V8 to be actually used in a RC car (a project that is still many many moons away :p, but an eventual goal)

    I am going over every single inch of the engine with a fine tooth comb to come up with the BEST possible engine with crazy performance and reliability.

    Swifty
    As a rule 'they' say as long as your skirts of the piston are roughly half your piston diameter there should be no cocking in the cylinder. they are also done with the top of the piston perfectly round, and down at the skirts it is slightly oval to help stop the cocking in the cylinder and for expansion.
     
  7. Feb 11, 2013 #7

    Lew Hartswick

    Lew Hartswick

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    For a couple years now the engines have to last for two races plus the practice and
    qualifying. (F1 the only auto racing) :)
    ...lew....
     
  8. Feb 11, 2013 #8

    trumpy81

    trumpy81

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    You have to remember that F1 engines are at operating temperature before they are even able to be started. They would disintegrate if started from cold, such are the tolerances of the components.

    Such a piston in a model engine could easily 'twist' within the bore, and this is often the reason behind the extended skirts. Although in a lot of model engine designs I have looked at, I'm sure their pistons could easily be reduced in height without too many ill effects. Any offsetting of the crank to the cylinder center line will normally use an extended piston skirt to combat the increased piston to cylinder pressure. The premise being that the load is spread over a larger area and with greater moments of inertia.
     
  9. Feb 12, 2013 #9

    wildun

    wildun

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    CAMNEFDT,
    Desigining something of your own is a great project, designing the best solution for achieving "crazy performance and reliability" in a model (RC) car possibly would not be by using a V8 engine! - I think you will find that a fairly high performance single cylinder two stroke engine and properly designed exhaust chamber would beat it hands down, both in the power to weight ratio, the outright power and the cost, (unless cost is no object).
    Then, in the reliability stakes..... what if the engine seizes and/or breaks one of those rods you so lovingly fashioned, or bends the beautiful big long crankshaft you spent a month making? ... in the case of the two stroke, probably a reasonably simple repair and back in business!
    Point is, what do you want? - to be a draughtsman/designer and let your mind roam free? to have fantastic performance - with a model V8??, To have a very reliable and competitive model car- with a model V8? - to be a competent machinist to make all this come about?
    That's what I meant when I said earlier, "one step at a time" and I'll add a bit more "everything starts with a dream, but for the dream to come true it needs to be tempered by reality".

    Still, no harm in dreaming - I always did, but I have also faced all the realities (and disappointments )through my forty something years in engineering, - don't lose the dreams, but pace yourself and remember, learn only one discipline at a time - but keeping the others in sight - good luck and do well.:)
     
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  10. Feb 12, 2013 #10

    Goldflash

    Goldflash

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    I would buy a copy of "Modern Engine Tuning by A Graham Bell". Read up on piston design , Bore to Stroke Ratio , Connecting Rod Ratio to Piston Stroke.
    Forged pistons versus cast pistons , port design and cylinder block design and crankshaft design camshafts etc etc etc . This book is a bible if you are building a 4 stroke or modifying a 4 stroke engine. Better to make a single cylinder engine that you can keep making changes to so you are able to achieve quantifiable results first me thinks.
     
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  11. Feb 12, 2013 #11

    hi speed scrap

    hi speed scrap

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    Last edited: Feb 12, 2013
  12. Feb 12, 2013 #12

    Till

    Till

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    A high performance V8 engine with the necessary singleplane crankshaft will lack the beloved bubbling sound.
     
  13. Feb 12, 2013 #13

    camnefdt

    camnefdt

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    Hi guys thanks for all the replies and criticism, its always valued by such a novice as me. :)

    would just like to point out that i am aware that something engineered to the level of the F1 piston, is waaaaay overboard for a scale model V8. I was just using that as a reference point to ask the question whether anybody has tried using these type of pistons as apposed to the regular old straight cylinder.

    please also be aware that i will only be attempting the V8 in no less than 10 years and in that time will be doing lots and lots of experimenting and tinkering on single cylinder and other various IC engines to test out different designs and see what works and what doesn't.
     
  14. Feb 12, 2013 #14

    wildun

    wildun

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    That's the story, - good on ya mate! :cool:
     
  15. Feb 12, 2013 #15

    Niels Abildgaard

    Niels Abildgaard

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    Here is an idea for a piston/conrod assemblycompared to a more conventional type

    junkers_for_ny_smart.GIF

    junkers_smart_stempler.jpg
     
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  16. Feb 13, 2013 #16

    camnefdt

    camnefdt

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    niels

    thats exactly the type of idea i had, nothing overly engineered, but reduces the weight and friction of the piston, allows for better response on revving the engine and possibly better performance too.

    have you at all tried incorporating that design into an engine as of yet?
     
  17. Feb 13, 2013 #17

    FannBlade

    FannBlade

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    Hope to see your engine build soon and good luck with your venture.
    F1 engines are the Holy Grail of engineering....my absolute favorite Motorsport. 18000 rpm and staying together defies all inertia logic.
     
  18. Feb 13, 2013 #18

    canadianhorsepower

    canadianhorsepower

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    specialy a four strokes:fan:
    but the stroke is only 1.6 inch and bore max at 3.8
     
  19. Feb 13, 2013 #19

    camnefdt

    camnefdt

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    thanks, i am only 21 and start my career on Friday :D from there i plan to save up and get my first lathe or milling machine within a year a 2. Once i get that, nothing will be able to hold me back as i build up a nice workshop and begin messing around with various engines and other projects iv got on mind :)
     
  20. Feb 13, 2013 #20

    Entropy455

    Entropy455

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    Just a bit of discussion-

    F-1 engines run high compression, at very high rpm. Rules of F-1 racing limit engine displacement. Thus engineers are forced to make modifications elsewhere to increase power output – via increased rpm, increased compression, increased volumetric efficiency, etc. Extreme rpm operation requires minimizing rotating mass, minimizing reciprocating mass, and minimizing friction-surface areas. The baby piston skirt will minimize mass and cylinder-wall drag forces, however the tradeoff is accelerated piston skirt wear, and the design requirement of larger rod-stroke ratios. Also note that light-weight engine parts are usually the first to blowout when an engine falls slightly out-of-tune (aka detonation).

    There was a rather heated discussion a few years back (on another forum), with regard to aluminum connecting rods for racing applications. At the time, aluminum rods were becoming a popular upgrade for street-driven (and occasional drag-strip driven) muscle-car engines (454s, 455s, 460s, etc). Here’s the problem - aluminum will work-harden and fatigue with use - and with enough cycles, aluminum rods WILL ultimately fail – as many weekend racers have discovered by punching holes in their engine blocks at half-track. Another guy reported throwing a rod simply by starting his aluminum-rod engine in freezing weather.

    The original thought was that because Top Fuel engines utilize aluminum rods, they must be the best choice for a street/strip engine also. The problem is that Top Fuel rods are aluminum because they can absorb the traumatic impulse events of burning nitro-methanol, whereas 4340 rods cannot. It is the work-hardening properties of aluminum that makes the rods able to absorb the trauma – and is also why Top Fuel rods are replaced every 3 to 5 races. . . .

    Point being – just because a technology is good for F-1 race cars and/or Top Fuel dragsters, does not mean it’s good for all race engines, or basic engine building in general.

    The old checker cabs were notorious for running 500,000 to 1,000,000 miles between engine rebuilds. Why? The answer is because of well designed “heavy-duty” parts that are moving relatively slowly.

    I’ve got a marine diesel engine with 14,000 hours on it, and it’s still running strong. Ask yourself this question – what would the power returns be, or fuel-efficiency returns be, by installing baby-skirt pistons into this marine diesel? Answer: it would likely be virtually immeasurable power returns on the dyno, and the engine would certainly not last for 14,000 hours of heavy-load usage.
     

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