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-   -   Project 100 (custom enclosed Honda C90 targets 100 mph vmax and 100 km/L FE) (https://ecomodder.com/forum/showthread.php/project-100-custom-enclosed-honda-c90-targets-100-a-18216.html)

visionary 07-19-2011 04:15 PM

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

The principle project objective is to create a vehicle that has a maximum speed in excess of 100mph, can achieve 100mpg+ at its cruising speed of 70mph, from an engine displacement of 100cc.

EDIT
So here is a concept sketch for the project. On the basis that a picture is worth a thousand words, it should make it easier for anyone to understand what I am aiming for.
http://ecomodder.com/forum/member-vi...eptsidesml.jpg


EDIT – Provide an Index
The thread has become so large that it takes serious commitment to read in full. So for the casual reader I have compiled an index


See some youtube video of the semi-finished vehicle.
Airfield shakedown
http://ecomodder.com/forum/showthrea...tml#post337981

Slow speed stability tests
http://ecomodder.com/forum/showthrea...tml#post312801


Postings about targets
Plans for gearing http://ecomodder.com/forum/showthrea...tml#post258994
Frontal area calcs for drag http://ecomodder.com/forum/showthrea...tml#post260523



Postings about build process (with images)
Carburettor mounting http://ecomodder.com/forum/showthrea...tml#post267792
Steering design http://ecomodder.com/forum/showthrea...tml#post272973


Contributions by notable experts
Craig Vetter – scepticism about C90 power http://ecomodder.com/forum/showthrea...tml#post261934

Kraig Schultz – helpful advice
http://ecomodder.com/forum/showthrea...tml#post337998

Paul Blezard – opinion about goals and discussion with Cedric Lynch
http://ecomodder.com/forum/showthrea...tml#post335913



Insightful comments by forum members (there are many and I will note and credit as many as possible in due course)
Frank Lee – opinion on aero design
http://ecomodder.com/forum/showthrea...tml#post259197



I have done enough research to believe that these targets are possible, although they will be difficult to achieve. I will hamper myself further by choosing to run exposed wheels, which is a personal choice, as I don’t like the “dustbin” fairing style. I think it is important to ensure that the vehicle remains “cool” if it’s ever to be widely accepted.

Many years ago I was inspired by Amory Lovins’ Hypercar principle, then quickly realised that one of the biggest drawbacks would be congestion, which is already a major source of waste. Since then I have worked on “single person vehicles” as a part of the solution. I have already produced a full size prototype vehicle with single track and fully enclosed bodywork, which I will call an “internal motorcycle”. This initial vehicle is a pure “proof-of-concept” prototype and has no chance of being acceptable for road-testing on the public highway. Therefore I intend to use “Project 100” as a spin-off, which allows me to complete lots of road testing, without worry about registration and the fear of arrest, much as Craig Vetter does.

I have chosen to start with a Honda C90 “cub” as a donor vehicle, due to its high production numbers, horizontal engine design and low capacity. I will fabricate a new frame that allows recumbent seating and cover it with my prototype bodywork.

I would very much welcome all comments and opinions (positive and negative) as I document the project. This forum contains many wise voices and I am a firm believer in “the wisdom of the crowd”, and how that can provide a better outcome.

jkv357 07-19-2011 04:32 PM

Should be an interesting and challenging project!

Keep us up to date on your progress and post some photos as you go.

EDIT: I assume you've seen this nicely done aero project - http://ecomodder.com/blog/diy-aero-f...cycle-214-mpg/


Jay

visionary 07-19-2011 05:01 PM

1 Attachment(s)
Now that I have identified the objectives, let me explain how I hope to achieve them. - your thoughts are welcome!

initially I have purchased a Honda C90 cub, with a view toward using the engine/gearbox and registration particulars.
I have started fabrication of a tubular spaceframe "chassis" which allows the driver to sit low down between the wheels with the same driving posture as a sports car.
I'll post some images because there's too much to explain
But my aim is for 0.60msq frontal area, a cd of 0.17 and with 10hp I think 100mph should be possible
Here is donor vehicle shot and next post will be fabrication images

visionary 07-19-2011 05:07 PM

Yes Jay
Allert's work and the "buzz" on this forum is what convinced me to divert away from my "top-secret" prototype and make an everyday vehicle.
I only wish Allert continued his story and kept us up to date. His project was so well documented that it became an inspiration for me. I only hope I can do half as well

visionary 07-22-2011 05:02 PM

2 Attachment(s)
So here is my first project update. Images are of the Honda C90 motor, which I am using and the rear wheel/tyre & swing arm.
Motor first. I bought a blown motor (seized big-end) to use as a dummy for fabrication purposes. I’ll swap it for my good unit when I strip the bike apart, but I don’t want too much stuff apart at once. I’m using the electric start version as kick starting will be impossible with the motor mounted below the seat and fully enclosed by chassis and bodywork. The starter adds a bit of height to the assembly but without a purpose built unit I don’t think I can do any better. The carb needs to be remounted – eventually I will go to fuel injection but in the short term I will cut-and-shut the inlet manifold to create a lower profile. This part will sit just below the bend in my knees, so it can be a bit higher than the seat base.
The rear wheel assembly is from a Kawasaki ZR750, no idea what year, I just bought it from a motorcycle breakers because I liked the fat 160 rear tyre. Despite the difficult aims of this project I continue to make compromises because this thing has to look “cool”. I know mass and drag penalties will come with this set-up but running around on skinny tyres could kill the attractiveness of the finished article.

Craig Vetter has a point about the best vehicle being your first choice, and for me there is great appeal in a “good-looking” machine. In the few weeks that I have had the C90, my eyes have been reopened about the practicality of motorcycles. Although I have always considered myself a “biker” the truth is that I have not used a bike as regular transport since my teens. They make great toys but no way would I choose one over my car for anything but a “fun” journey.

visionary 07-31-2011 05:18 PM

2 Attachment(s)
Update 002
So the latest update is on the first stages of the chassis construction (two images attached) which shows the dummy engine mounted and the rear swing arm attached.

The “mini-trestles” are fabrication support and ride height (150mm) blocks, the spaceframe material is 20x20 ERW steel box section and as pictured is in “tack-up” condition prior to TIG welding. It will of course be fully triangulated when finished, what you see are the basic “planes” of the design. This is the centre or lower chassis, one of three “modules”, the other two will be the front and rear sections.
Further news concerns the C90 which I hate riding. It all works quite well and I’ve used 3 or 4 tank fulls of fuel, so I can confidently quote a current 133mpg(imp), which is some compensation for the hardship I have to endure while riding it. This mileage has all been completed without using “dual carriageway” roads, so lots more stop/start than ideal and lots of WOT trying to maintain a reasonable pace to match other traffic. Anyway, at least it already does 100+mpg (part of my project objective), now I just need to make it do 100mph.

jkv357 07-31-2011 06:22 PM

Thanks for the updates, looks like it's coming along nicely.

What was it about the C90 that made it such a pain to ride - low power?

Do you have a design set for the body?


Jay

visionary 07-31-2011 06:54 PM

Hi Jay - lack of power certainly takes the fun out of motorcycling! Other critical "hates" are poor comfort (sore backside after 45minute commute) and weather watching for journey planning. The real issue is that I prefer my BMW for speed/comfort/practicality & aircon and it makes for a more versatile experience - the only downside is 32mpg @ £6.00+ / gallon.
Next post I'll put up some full-body renderings!

Boreas 07-31-2011 10:06 PM

Very interesting. Looking forward to more.

theycallmeebryan 08-01-2011 01:36 PM

Very interesting project. It seems like you have all the necessary resources to finish the project. Good luck, I'll be following your progress. Please update as much as you can.

visionary 08-28-2011 04:27 PM

Update 003

So here is a concept sketch for the project. On the basis that a picture is worth a thousand words, it should make it easier for anyone to understand what I am aiming for.

http://ecomodder.com/forum/member-vi...eptsidesml.jpg

The “sketch” is done in photoshop with actual photos of each of the major components (inc driver) laid over a CAD drawing to ensure scale remains accurate. I have left the body transparent so the internals can be viewed. I will post a plan view and front & rear views when I complete them. The size and approximate mechanical layout are all fixed at this point, but styling issues can be changed in the final bodywork. I would like to hear any comments about the body shape and its probable Cd, I am aiming for less than 0.2.
Since this project as all about aerodynamic performance to achieve the goals, any suggestions would be welcome.

visionary 08-28-2011 05:53 PM

Update 004
Although progress over past couple of weeks has been slow, I have made some decent steps forward. Firstly I won an e-bay auction for a Honda CBR600 frame, which I decided would make the perfect front –end for the project. The twin disc and decent telescopic forks will make a substantial improvement over the C90 drum and leading link set-up. Here are the parts cut ready for fabrication.


http://ecomodder.com/forum/member-vi...tion-04sml.jpg

Secondly, I have arrived at a reasonable solution for the rear spring/damper unit which I am mounting in the lower body section. Initially it seemed to conflict with the location of the intermediate shaft, but I have been able to fit both items.

http://ecomodder.com/forum/member-vi...tion-03sml.jpg


The intermediate shaft is needed to align the engine gearbox sprocket with the chain to the rear wheel. When centralised, the engine is too “slim” for the 160 rear tyre, and the chain dimensions would require custom sprockets making. I have solved this problem by driving the intermediate shaft (loose awaiting final machined spacers before welding) with a standard C90 chain and two engine sprockets. The original Z750 front sprocket is then fitted to the intermediate shaft and drives the stock chain and rear sprocket.
This allows more opportunity for gear ratio alteration to match the std 3speed box and target top speed. It also allows the opportunity of fitting an additional drive source (eg: electric motor) to further improve efficiency – but that’s more than I want to take on at present

Frank Lee 08-28-2011 05:59 PM

It looks nice. Quite the change, from C90 to CBR600- must be one hella change in the performance parameters? Seems that front end would be overkill (heavier, mismatched wheels) if the rest of the machine is still all based on C90 bits?

visionary 08-28-2011 06:11 PM

Hi Frank - yeah you are right about the mismatch. I know the front end (CBR600) and rear swing arm assy (Z750) are more than whats needed but I still want decent brakes on this thing! I'm hoping for about 130kg which is 45 more than the stock C90. if it does hit 100mph I want to feel safe - the C90 brakes and suspension are so inadequate (even for 50mph) that I have no choice but to upgrade
I could have spend weeks trying to find lighter parts but these came up cheap!

Patrick 08-28-2011 07:19 PM

Quote:

Originally Posted by visionary (Post 258475)
Update 003

So here is a concept sketch for the project. On the basis that a picture is worth a thousand words, it should make it easier for anyone to understand what I am aiming for.

http://ecomodder.com/forum/member-vi...eptsidesml.jpg

The “sketch” is done in photoshop with actual photos of each of the major components (inc driver) laid over a CAD drawing to ensure scale remains accurate. I have left the body transparent so the internals can be viewed. I will post a plan view and front & rear views when I complete them. The size and approximate mechanical layout are all fixed at this point, but styling issues can be changed in the final bodywork. I would like to hear any comments about the body shape and its probable Cd, I am aiming for less than 0.2.
Since this project as all about aerodynamic performance to achieve the goals, any suggestions would be welcome.

Are you going to use outriggers like the E-tracer for when you're stopped?

JasonG 08-28-2011 07:35 PM

Might I suggest fully enclosing the rear swing arm and tire ?

visionary 08-29-2011 07:36 PM

Replies
Patrick - for my main prototype (dont forget this is just a spin-off project) I found a more elegant solution to the outrigger problem but it is not perfected yet. For this vehicle I will start with a simple movable body section through which I can extend my leg(s) when needed
JasonG - I'm agonising over that point. I know I really should but I also like the look of an open wheel. Reading other threads there seems to be a big question about sidewind stability, which I'm sure will be worse with a fully integrated body enclosure of the rear wheel. I could make a section that moves with the swing arm (like a "super hugger") and try that but it will be one of the final jobs on the list. But I do intend making the exhaust muffler as a deflector to clean-up airflow to the rear tyre (theres a new kawasaki does something similar) and energise the wake with exhaust gasses.
Thanks for your interest guys - I would love to hear more opinion
Pete

Quasimoto 08-30-2011 01:29 PM

Quote:

Originally Posted by visionary (Post 251585)
So here is my first project update. Images are of the Honda C90 motor, which I am using and the rear wheel/tyre & swing arm.
Motor first. I bought a blown motor (seized big-end) to use as a dummy for fabrication purposes. I’ll swap it for my good unit when I strip the bike apart, but I don’t want too much stuff apart at once. I’m using the electric start version as kick starting will be impossible with the motor mounted below the seat and fully enclosed by chassis and bodywork. The starter adds a bit of height to the assembly but without a purpose built unit I don’t think I can do any better. The carb needs to be remounted – eventually I will go to fuel injection but in the short term I will cut-and-shut the inlet manifold to create a lower profile. This part will sit just below the bend in my knees, so it can be a bit higher than the seat base.
The rear wheel assembly is from a Kawasaki ZR750, no idea what year, I just bought it from a motorcycle breakers because I liked the fat 160 rear tyre. Despite the difficult aims of this project I continue to make compromises because this thing has to look “cool”. I know mass and drag penalties will come with this set-up but running around on skinny tyres could kill the attractiveness of the finished article.

Craig Vetter has a point about the best vehicle being your first choice, and for me there is great appeal in a “good-looking” machine. In the few weeks that I have had the C90, my eyes have been reopened about the practicality of motorcycles. Although I have always considered myself a “biker” the truth is that I have not used a bike as regular transport since my teens. They make great toys but no way would I choose one over my car for anything but a “fun” journey.




With all the unsprung weight you're adding I believe you'll have a hard time meeting your goals.

Patrick 08-30-2011 01:55 PM

Quote:

Originally Posted by Quasimoto (Post 258746)
With all the unsprung weight you're adding I believe you'll have a hard time meeting your goals.

Unsprung weight? It looks to me like the additional weight is all sprung.

Visionary - I suggest you move the engine over and back and eliminate the jackshaft. That will reduce weight and driveline losses. Also, you could go with a pull-start system like the California Commuter used. They adapted a lawnmower pull starter to turn the kick starter. That should save you some weight in the electrical system (smaller battery, no starter motor, no solenoid).

Quasimoto 08-30-2011 02:13 PM

Quote:

Originally Posted by Patrick (Post 258754)
Unsprung weight? It looks to me like the additional weight is all sprung.

Actually, you know not of what you speak. Unsprung weight is all of the motorcycle that is not supported by the suspension, such as the wheels, brakes, tires, etc. Check it out.

Patrick 08-30-2011 02:20 PM

Quote:

Originally Posted by Quasimoto (Post 258756)
Unsprung weight is all of the motorcycle that is not supported by the suspension, such as the wheels, brakes, tires, etc. Check it out.

Exactly my point. So where's all the unsprung weight he's adding?

Quasimoto 08-30-2011 02:29 PM

1 Attachment(s)
Quote:

Originally Posted by Quasimoto (Post 258756)
Actually, you know not of what you speak. Unsprung weight is all of the motorcycle that is not supported by the suspension, such as the wheels, brakes, tires, etc. Check it out.

wheels, brakes, tires, etc

Patrick 08-30-2011 03:18 PM

Quote:

Originally Posted by Quasimoto (Post 258760)
wheels, brakes, tires, etc

You mean in comparison to the original Honda 90 motorcycle? Then yes, there might be some additional weight there. But it might not be all that much. The rims are aluminum instead of steel, same with the swingarm. The brakes are disks instead of drums and might(?) be lighter or about the same. The big difference is probably the tires.

So why do you believe that the additional unsprung weight, if there is any, will prevent him from reaching his goal? Because of the additional rotating mass that has to be accelerated on every takeoff?

visionary 08-30-2011 03:54 PM

Replies
Quasimoto – to be honest, until you mentioned it, I hadn’t put much thought into “unsprung weight”, although it’s a subject I’m very familiar with. My best guess is that of the 45kg increase only 10kg will be unsprung. The bigger (heavier) tyres and brakes are only about 5kg per end, and it’s a necessary evil as I must improve the spec to make it suitable to use at the higher speeds. But think of this – why will this significantly impair my ability to reach the 100mph target? Unsprung weight will play no part in straightline performance, its major effects will be shown on “ride and handling” and even then the better tyres brakes and dampers should outperform the stock C90 kit.
Patrick – yeah, the “jackshaft” was an unintended consequence, and I acknowledge that it will reduce my driveline efficiency, but its there now and fabrication has finished with reasonable solution, so I’ll stick with it! But if I posted images and weights, I would be interested in how big you think the losses will be. My stock motor gives (supposedly) 7.5hp, and I’m aiming to up this to 10hp to reach the 100mph target – would another 0.5hp cover the losses?
On the starter thing – I bought the “electric start” version of the C90 already, and I plan to keep the original charging system and battery on the revamped vehicle.

Thanks to both of you for your input! Let me have more, particularly on the aero and body design side. This project is all about how you can take a low power vehicle with a modest top speed and make a “fast & frugal” motorcycle – and aero is the key!

Patrick 08-30-2011 10:06 PM

Quote:

Originally Posted by visionary (Post 258784)
My stock motor gives (supposedly) 7.5hp, and I’m aiming to up this to 10hp to reach the 100mph target – would another 0.5hp cover the losses?

I don't know how much the losses would be, but I'm sure that industrial pillow blocks soak up at least some power. Here's a site with some parts that might help you boost your engine's power output: POWROLL PRODUCTS FOR THE HONDA CT, CL, SL, ATC, S90

Quasimoto 08-31-2011 10:06 AM

Quote:

Originally Posted by Patrick (Post 258774)
You mean in comparison to the original Honda 90 motorcycle? Then yes, there might be some additional weight there. But it might not be all that much. The rims are aluminum instead of steel, same with the swingarm. The brakes are disks instead of drums and might(?) be lighter or about the same. The big difference is probably the tires.

So why do you believe that the additional unsprung weight, if there is any, will prevent him from reaching his goal? Because of the additional rotating mass that has to be accelerated on every takeoff?

Exactly, even with the proper gearing; that small motor will be straining against the additional rotational mass of the large rotors, wheels, and tires.

Patrick 08-31-2011 10:12 AM

A random thought on gear ratios
 
The top speed of the motorcycle is what, about 50 mph? So if you gear it to a new top speed of 100 mph your acceleration will be much worse. Add in the additional weight and it will probably be a real dog off the line. Also, first gear is going to be way too tall, so you will probably be slipping the clutch a lot. You might want to throw some kevlar clutch plates in there when you have the engine apart for the hopup so that you don't keep frying the clutch. Barnett Performance Products INDIVIDUAL KEVLAR FRICTION PLATES from RJ SPORT & CYCLE Honda CT90~q=fitaa9013zzisidaa5zz~r=bidaa140zz~

Quasimoto 08-31-2011 10:18 AM

[QUOTE=visionary;258784]Replies
Quasimoto – to be honest, until you mentioned it, I hadn’t put much thought into “unsprung weight”, although it’s a subject I’m very familiar with. My best guess is that of the 45kg increase only 10kg will be unsprung. The bigger (heavier) tyres and brakes are only about 5kg per end, and it’s a necessary evil as I must improve the spec to make it suitable to use at the higher speeds. But think of this – why will this significantly impair my ability to reach the 100mph target? Unsprung weight will play no part in straightline performance, its major effects will be shown on “ride and handling” and even then the better tyres brakes and dampers should outperform the stock C90 kit.

Since the total unsprung weight includes the lower fork legs, front fender, brakes, rotors, axle, wheel, tire; the rear swing arm, brakes, rotors, axle, wheel, and tire; It would be my guess that the total increase would be closer to 36kg unsprung. But of course I don't have the parts to weigh, so am only guessing.

jkv357 08-31-2011 10:31 AM

Quote:

Originally Posted by Patrick (Post 258893)
The top speed of the motorcycle is what, about 50 mph? So if you gear it to a new top speed of 100 mph your acceleration will be much worse. Add in the additional weight and it will probably be a real dog off the line. Also, first gear is going to be way too tall, so you will probably be slipping the clutch a lot. (SNIP)

Getting both reasonable (usable) acceleration and a 100 MPH top-speed at the same time is going to be difficult. Especially with added weight.

I don't know that you would even have the necessary amount of power (with full streamlining) to achieve 100 MPH from that engine without significant modifications - even with proper gearing.

Patrick 08-31-2011 05:44 PM

Idea for gearing.
 
You could try a Trail 90 (CT90) engine with the dual-range gearbox. It's supposed to have a 1.89:1 ratio to the countershaft when in low range. Then you could gear up the final drive to 2X and achieve the 100 mph top speed while in high range (1:1 ratio). Supposedly these are shiftable "on the fly." You would have an 8-speed gearbox, in effect.

visionary 08-31-2011 06:20 PM

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 08-31-2011 06:30 PM

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

Patrick 08-31-2011 06:50 PM

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 09-01-2011 02:03 PM

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

Patrick 09-01-2011 07:52 PM

2 Attachment(s)
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 09-01-2011 08:27 PM

1 Attachment(s)
I forgot to add - smooth wheel covers.

Frank Lee 09-01-2011 10:15 PM

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! :eek: 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! :eek: ) 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 09-01-2011 10:45 PM

Quote:

Originally Posted by Frank Lee (Post 259197)
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 09-01-2011 11:05 PM

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

Patrick 09-01-2011 11:16 PM

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?


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