Project 100 (custom enclosed Honda C90 targets 100 mph vmax and 100 km/L FE)

[visionary]

Patrick - that would be a neat idea, a twin range gearbox! I had no idea it even existed, do you have any info or images?
I know I'm short on ratios - the standard gearbox is three speed, and I realise that acceleration will always be the weak point but here is what I planned.
The stock C90 is ridiculously low-geared, I often found it better to get off the line in 2nd, and at no time have I ever been more than 10mph in first. I did all the gear calcs and found that my 1st gear gives 2.2mph per 1000rpm and 2nd gear gives 3.8mph per 1000 rpm.
The new system (jackshaft & Z750 rear-end) gives 3.1mph per 1000 rpm (first gear) and 8.3mph per 1000rpm in top. This means I'm comfortable getting off the line (as its no worse than I'm used to) and the top speed goal can be reached with a slight increase in max revs from 10500 to 12100. I'm confident the rebuilt engine will manage this with ease.
Thanks for links to engine parts - if you see any more let me know

jkv357 = it's a tough challenge alright, and I didn't expect to be popping any wheelies. but I ran the numbers through the calculator tool provided on the forum and it confirmed the possiblity. The link is

http://ecomodder.com/forum/tool-aero-rolling-resistance.php?Weight=200&WeightUnits=kg&CRR=.008& Cd=.19&FrontalArea=.7&FrontalAreaUnits=m^2&FuelWh= 33557&IceEfficiency=.21&DrivetrainEfficiency=.90&P arasiticOverhead=0&rho=1.22&FromToStep=5-200-5

Thanks again - all thoughts welcomed
Pete

[Frank Lee]

I don't think the rr, frontal area, and Cd will be that low.

[Patrick]

Honda CT90 info: Honda CT90 - Wikipedia, the free encyclopedia

Long duration cam: CT90_ATC90 ST90_CL90 SL90_S90 CS90_CM91 PERFORMANCE CAMSHAFT (90/PER/CAM)

[Quasimoto]

Well Pete good luck, I hope you prove us all wrong. I can't wait to see the progress.

[Patrick]

WRT aerodynamics: I think the area behind the front wheel will act as a parachute. I would round that out underneath the cycle somewhat to give the air a smooth path. The back window seems too steep - I think you will have separation there. I would bring it up higher, tapering in from the sides and ending in a Kammback if you can't get it to a point. Also, I think the area in front of the rear wheel could be improved by tapering the bodywork in (gently) as tightly as you can get to the swingarm and the tire to reduce separation there. See the attached pic for my vision of how these mods would look. Sorry about the color match - I'm not that good with Paint.

[Patrick]

I forgot to add - smooth wheel covers.

[Frank Lee]

I don't think the area behind the front wheel is problematic as it was; for one it's already in a turbulent zone right behind the wheel and for two it won't act as a "parachute" because there is an AFTBODY right there. If anything it will be like the front of any bluff body in that air piles up into a bubble in front of it if it isn't pointy enough.

Also, I'd wager the canopy is very slender and boattailed from plan view too so it's probably just fine as it was, being somewhat steeper than "template".

PEOPLE listen up: concave pockets facing forward DON'T act as parachutes because one of the differences is, there is a ginormous AFTBODY right there. Parachute drag is from the high turbulent flow in the wake because there is no AFTBODY to promote orderly "closure" of flow.

Re: rr: Allert has a tire rr test setup and his skinny little 17" 125 tires could do no better than .17, and that was with a worn one in the test group, and that was at 59 psi. He noted that bicycle tires had HALF the rr. Yes, motorcycle and to a lesser extent bicycle tires really suck as far as r.r. It must be due to the lack of steel belted radial construction. Anyway, when playing with the EM performance calculator, it would be more realistic to plug in .15 if not .20.

With that in mind, I took the 17" front wheel off my Songi today and "chopped it" with a 20 x 1.9 freestyle tire and alloy BMX rim. Didn't weigh anything yet but the bike parts must weigh less than half the stockers. (Weighed: 10.5 lb Songi wheel and tire; 3.5 lb BMX at whatever resolution a digi bath scale has). Sorry, no objective/accurate measurement data but subjectively it made a world of difference! The steering response is phenomenally lighter and faster and the new tire has 65 psi as sidewall max vs 55 for the HEAVY but nicely ribbed original.

Combine that with the other recent mod, that of the driver's seat delete (now I sit on the BACK seat, about 12" lower than before! ) and I find myself cruising around at much higher speed yet seemingly not draining the battery pack any worse than before when I toddled around at sub-bicycling speeds.

[Patrick]

Originally Posted by Frank Lee

I don't think the area behind the front wheel is problematic as was; for one it's already in a turbulent zone right behind the wheel and for two it won't act as a "parachute" because there is an AFTBODY right there. If anything it will be like the front of any bluff body in that air piles up into a bubble in front of it if it isn't pointy enough.

PEOPLE listen up: concave pockets facing forward DON'T act as parachutes because one of the differences is, there is a ginormouse AFTBODY right there. Parachute drag is from the high turbulent flow in the wake because there is no AFTBODY to promote orderly "closure" of flow.

I guess we'll just have to disagree on this point. Go to this page and compare the "prism" to the "bullet." Shape Effects on Drag Contrary to popular belief on this forum, the shape of the front most definitely makes a difference.

[Frank Lee]

That's great but that isn't a prism shape there.

[Patrick]

Why do you think they put this nose on the Superbird NASCAR racer after extensive work in the wind tunnel: http://www.musclecarclub.com/musclec...perbird-1a.jpg

instead of the stock nose: http://www.retro.net/keywords/1970_P...d_Runner_1.jpg

Maybe the air bubble wasn't quite cutting it?