40mph speed secrets revealed

ah! i didnt envision it a a long taper cone my mucho ap-oligo to you mofrere

that pipe is going to work great i think. is it set up for midrange top end?

looks like it is gonna be friggin shweet (make sure you put a nice stinger on the end of that and run it mufflerless of course, wouldnt want to lose any power on that monster!

on a side note, i never even clued in to the fins untill it was mentioned, you could run into an issue there, perhaps you can ratrod up an air catch and direct it down?
 
Vertical fins cool better for slow moving engines, especially at idle. Horizontal cools better for fast moving engines.

30mph is still considered a slow moving engine.
 
that's a lot of work for just 40mph Im already there with minor piston port matching
and a very good expansion chamber Im hoping the new reed valve set up will get me to a 28 tooth rear sprocket and 50mph!
 
this motor hasn't actually run yet, but since it is a true 79cc motor, i imagine it shouldn't run too bad. where did you get your very good expansion chamber?
 
I'm just gonna stir the pot... I agree, 'that's a helluva lotta work for just 40MPH...' you'd better get at least 46MPH out of it!!! haha ;)
 
Was the spacer under the jug just to space it up some, or is it an adapter? 40mph doesn't seem too difficult, but this motor is sure to run for a lot longer than most.
 
thehatchninja said:
40mph doesn't seem too difficult...
Click to expand...

With these small engines there's a wall at about 35mph caused by the combination of a lack of torque and escalating wind resistance. The drag ratio involves some very messed up math where the resistance is squared... making every mph past 20ish harder and harder to get.

"Assuming a more-or-less constant drag coefficient, drag will vary as the square of velocity. Thus, the resultant power needed to overcome this drag will vary as the cube of velocity."

>.<

I hate math - but suffice to say physics isa ***** - it boils down to pretty much if ya wanna go twice as fast you'll need at least four times the power (more actually, a lot more as the effect is exponential - but ya get my point lol). With the speeds foureasy is already achieving it'd be actually far easier to gain significant speed by reducing resistance (like an aerodynamic shell) than tweakin' the motor any more. Honestly to get more speed he'd prolly hafta double his displacement at least, and that would only gain about 1/3 more speed... if that.
 
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you have a ten mil stroker happytime? you are my hero.... haha (no, seriousley, all you need is a top notch crankshaft assembly and you have it made!)
 
BarelyAWake said:
With these small engines there's a wall at about 35mph caused by the combination of a lack of torque and escalating wind resistance. The drag ratio involves some very messed up math where the resistance is squared... making every mph past 20ish harder and harder to get.

"Assuming a more-or-less constant drag coefficient, drag will vary as the square of velocity. Thus, the resultant power needed to overcome this drag will vary as the cube of velocity."

>.<

I hate math - but suffice to say physics isa ***** - it boils down to pretty much if ya wanna go twice as fast you'll need at least four times the power (more actually, a lot more as the effect is exponential - but ya get my point lol). With the speeds foureasy is already achieving it'd be actually far easier to gain significant speed by reducing resistance (like an aerodynamic shell) than tweakin' the motor any more. Honestly to get more speed he'd prolly hafta double his displacement at least, and that would only gain about 1/3 more speed... if that.
Click to expand...

Fo'sho'! Gear up and streamline if you really want to see a mile a minute. Also, pay up your life and medical insurances.
 
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