On a standard e-bike, you can get to 30 mph with 700 watts output power. Now reduce the the usual cross-sectional area by 3 to get a bullet-like enclosed recumbent and improve the coefficient of drag by a factor of 5 from the usual Cd=.9 of a bike, and this enclosed recumbent requires roughly 15 times less power to go the same speed. Since P ~= velocity^3, then going 70mph only requires 700*(70/30)^3/15 watts(Original_power*transformed_ratios*any_relevant_ratios) or about 600-700 watts (or <1000 watts for generality) with the stream-lined bullet enclosed recumbent. Add in a 3000+ watt RC motor with the proper gearing, and you got it made! Assuming fairly flat travel between two points, your standard 40 mile battery can now go more than 100 miles(well... that should be calculated). Couldn't you get somewhere on the highway system with that set-up?
The push for 70 mph.
- Thread starter swbluto
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Zoot Katz
100 kW
Sure. But I'd want SLAs, and lots of them, low down, just to keep from getting blown off bridges in a cross wind.
Put an aero-disc on the front wheel of a light weight pedal powered bike to get an idea of how much fun you can have with gusts.
Sam Wittingham has already done 81 MPH without a motor mainly by employing aerodynamics to gain efficiency.
That was under ideal conditions on a closed course.
Traveling seventy mph on a highway inside a coffin just doesn't appeal to me.
Cars are coffins.
Put an aero-disc on the front wheel of a light weight pedal powered bike to get an idea of how much fun you can have with gusts.
Sam Wittingham has already done 81 MPH without a motor mainly by employing aerodynamics to gain efficiency.
That was under ideal conditions on a closed course.
Traveling seventy mph on a highway inside a coffin just doesn't appeal to me.
Cars are coffins.
dogman dan
1 PW
Why not convert an ICE bike, and build an emotorcycle, that is designed for 70 mph? Have you ever experienced high speed wobble? I watched a bicycle frame flexing 3 inches once.
safe
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Sam Wittingham did 80+ mph in essentially a "tube". (not practical for the real world)
All racing organizations end up with some baseline rules for the limits of practical aerodynamics. These are the rules for the upcoming TTxGP at the Isle of Mann for 2009:
19. Streamlining
The streamlining of solo machines must correspond to the following specifications. Feet forward configurations within the criteria listed below are permitted.
a. Air foils or spoilers may only be fitted on solo machines when they are an integral part of the fairing or seat. They must not exceed the width of the fairing nor the height of the handlebar. Sharp edges must be rounded off with a minimum radius of 8mm.
b. Any part of the streamlining which faces rear wards, must be finished with rounded edges of 3.5mm min. radius.
c. The rider must be completely visible from either side. Except; riders hands and forearms which may be obscured by bodywork. The depth of the seat base can be as deep as the seat hump permitted on a motorcycle (150mm.) and the riders hips may be obscured to that extent.
d. The front inclination where the number plate is fixed must not exceed an angle of 30 degrees to the rear of the vertical.
e. The ground clearance of a solo vehicle when loaded must not be less than 100mm.
f. No part of the bodywork to contact ground up to normal racing motorcycle clearance
g. Bodywork may be no wider than 1m at any point.
h. Bodywork may not protrude further forward than 50mm in front of the front wheel
i. Bodywork may not protrude further rearwards than 200mm beyond the rear wheel
j. Bodywork must not be higher then the rider's helmeted head behind the rider.
k. Bodywork must not be higher than the rider’s shoulders in front of the rider.
l. Total side area behind the rider must be at least 20% greater than total side area in front of the rider.
m. Mirrors are optional. But if fitted then the Mirrors should be shatterproof and fold back without damage when the vehicle is on one side. The mirrors retain there normal configuration when vehicle is upright.
n. No movable or fixed aerodynamic devices (i.e. Wings, aerofoils) other than the basic body shape.
o. ALL MACHINES must have handlebars with a minimum width of 450mm.
History
There's a reason that road racer motorcycles look the way they do. There was a long testing period where the first motorcycles were shaped like airfoils and had many accidents as they got blown off the road by cross winds. For reasons of safety the current form has evolved and the limitations forced onto the designers actually make sense.
Sometimes the smartest thing is to accept past experience because there's a reason for things ending up the way they did... :wink:
The biggest problem is cross winds. Basically you want to allow just enough of a shape to recapture the aerodynamics of the worst part of the bodies shape and not much more. It's the side cross section area that you need to worry about.
My goal is to have a bike that handles well at speeds of 50 mph and above. (which I've already done) I'd rather have a good handling bike with "less than ideal" aerodynamics than one where I'm going to have difficulty negotiating a tight corkscrew in a track. I'm kind of against speeds going much above 50 mph if you have to sacrifice handling. :|
Don't forget we are supposed to stay under 1000 watts input and 750 watts output if we are talking about "ebikes". That's another thing to factor into the equation...
All racing organizations end up with some baseline rules for the limits of practical aerodynamics. These are the rules for the upcoming TTxGP at the Isle of Mann for 2009:
19. Streamlining
The streamlining of solo machines must correspond to the following specifications. Feet forward configurations within the criteria listed below are permitted.
a. Air foils or spoilers may only be fitted on solo machines when they are an integral part of the fairing or seat. They must not exceed the width of the fairing nor the height of the handlebar. Sharp edges must be rounded off with a minimum radius of 8mm.
b. Any part of the streamlining which faces rear wards, must be finished with rounded edges of 3.5mm min. radius.
c. The rider must be completely visible from either side. Except; riders hands and forearms which may be obscured by bodywork. The depth of the seat base can be as deep as the seat hump permitted on a motorcycle (150mm.) and the riders hips may be obscured to that extent.
d. The front inclination where the number plate is fixed must not exceed an angle of 30 degrees to the rear of the vertical.
e. The ground clearance of a solo vehicle when loaded must not be less than 100mm.
f. No part of the bodywork to contact ground up to normal racing motorcycle clearance
g. Bodywork may be no wider than 1m at any point.
h. Bodywork may not protrude further forward than 50mm in front of the front wheel
i. Bodywork may not protrude further rearwards than 200mm beyond the rear wheel
j. Bodywork must not be higher then the rider's helmeted head behind the rider.
k. Bodywork must not be higher than the rider’s shoulders in front of the rider.
l. Total side area behind the rider must be at least 20% greater than total side area in front of the rider.
m. Mirrors are optional. But if fitted then the Mirrors should be shatterproof and fold back without damage when the vehicle is on one side. The mirrors retain there normal configuration when vehicle is upright.
n. No movable or fixed aerodynamic devices (i.e. Wings, aerofoils) other than the basic body shape.
o. ALL MACHINES must have handlebars with a minimum width of 450mm.
History
There's a reason that road racer motorcycles look the way they do. There was a long testing period where the first motorcycles were shaped like airfoils and had many accidents as they got blown off the road by cross winds. For reasons of safety the current form has evolved and the limitations forced onto the designers actually make sense.
Sometimes the smartest thing is to accept past experience because there's a reason for things ending up the way they did... :wink:
The biggest problem is cross winds. Basically you want to allow just enough of a shape to recapture the aerodynamics of the worst part of the bodies shape and not much more. It's the side cross section area that you need to worry about.
My goal is to have a bike that handles well at speeds of 50 mph and above. (which I've already done) I'd rather have a good handling bike with "less than ideal" aerodynamics than one where I'm going to have difficulty negotiating a tight corkscrew in a track. I'm kind of against speeds going much above 50 mph if you have to sacrifice handling. :|
Don't forget we are supposed to stay under 1000 watts input and 750 watts output if we are talking about "ebikes". That's another thing to factor into the equation...
Drunkskunk
100 GW
I think the answer here is Yes, this could be done.
But who would realy want to?
Not me, not on bike components anyway. Not on a public highway.
But who would realy want to?
Not me, not on bike components anyway. Not on a public highway.
HAL9000v2.0
10 kW
I did 69,6 mph with 6,125kw on wheel and 7,125kw surge from batt on regular MTB.
John in CR
100 TW
dogman said:
How long did it take your pulse to return to normal?
Regarding the topic, my speed loving days are past, so I don't even want to go 70mph on a motorcycle. 0-40 or 45mph and 45-0 in the shortest time, are where my interest lies.
John
dogman dan
1 PW
About as long as it took to change my underwear. I was on the shoulder, right of the stripe but on pavement going down a big steep hill just north of Santa Fe NM, doing close to the speed of the cars, 55, when a truckfull of drunk indians decided to fun with me an run me into the dirt shoulder at about 50 mph. Man that bike frame went crazy till I got it back on the pavement. I've had some other occasions on real motorcycles, at about 90 mph. Once the right harmoics get started it's quite a ride. But just imagine hitting a stray 2x4 in the roadway at 70 mph with bike tires and spokes. No thanks.. It's not that it can't be done, just that you can really wish you hadn't tried. Anybody seen the world speed record downhill mtb holders crash? Pretty good, doing, I dunno 90 mph or more, and his frame just cracks in half. Great slow mo of him eating the dirt with his face at that speed. 
safe
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Given that we are restricted to 1000 watt input or 750 watt output (for the most part) and if you require all the safety rules for cross winds that limit the amount of aerodynamics the chances are that 45 mph is about the top speed you are going to get.
If the rules restrict the aero, then the top speed is narrow...
I too want to keep the top speeds down. Ebikes are not eMotorcycles and 70 mph is a little much unless you are on a downhill.
45 mph on the flat is roughly what my new project is estimated to do while still staying within the "Street Legal" power rules. (obviously the gearing isn't legal because the gearing is supposed to force you under 20 mph)
If the rules restrict the aero, then the top speed is narrow...
I too want to keep the top speeds down. Ebikes are not eMotorcycles and 70 mph is a little much unless you are on a downhill.
45 mph on the flat is roughly what my new project is estimated to do while still staying within the "Street Legal" power rules. (obviously the gearing isn't legal because the gearing is supposed to force you under 20 mph)
lepton
1 W
This may be the video you're talking about: http://www.youtube.com/watch?v=Swq9hBdvkKU
Scary stuff.
I've spent a lot of time around 40 MPH on a full suspension mountain bike frame. At those speeds I wear a full face helmet and motorcycle jacket, but it's still a dangerous thing to do. These days I cruise at 30, and rarely go faster.
70 is plenty possible, but as has already been said, it's sooooo dangerous...
Scary stuff.
I've spent a lot of time around 40 MPH on a full suspension mountain bike frame. At those speeds I wear a full face helmet and motorcycle jacket, but it's still a dangerous thing to do. These days I cruise at 30, and rarely go faster.
70 is plenty possible, but as has already been said, it's sooooo dangerous...
Jozzer
100 kW
Please, get a motorcycle!
I regularly do 70mph on mine, and cant imagine doing it on any smaller vehicle safetly. I'm not that faint of heart, but IMO more than 40mph on even the most stable bike is really asking for trouble and pain.
70 on a nice motorbike however should be tried once or twice in a lifetime
I regularly do 70mph on mine, and cant imagine doing it on any smaller vehicle safetly. I'm not that faint of heart, but IMO more than 40mph on even the most stable bike is really asking for trouble and pain.
70 on a nice motorbike however should be tried once or twice in a lifetime
safe
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This is what these record setting bikes look like on the inside. From a practical standpoint I really don't see being able to handle turns very well with such a machine, these are strictly for going in a straight line.Most of the fun is in the turns...
dogman dan
1 PW
Yeah, what he said. Go for it if you want to, but forget about something like that for street legal.
And yup, that is the video. On the stupid people kiling themselves shows, the quality is much better, and they slow mo it for you. Ouch! Those speed leathers are usually just a thin layer of plastic, I hope he at least had some thick longies underneath!
I also think about 40 mph is the top safe speed for most bike frames, wheels, etc. Custom stuff, like Safe builds is another story, and with the right tires and such could haul ass safely. If the fun is in the fabrication, great, but I just shudder to think of going out to mix with traffic at 70 mph on any kind of bicycle wheel and tire. Sooner or later there will be crap in the road and dodging it may be riskier than hitting it. My point is stock bikes are designed for this, and there is still plenty of fun fabrication in converting them. Just more practical when your done, especially since it has a vin number.
And yup, that is the video. On the stupid people kiling themselves shows, the quality is much better, and they slow mo it for you. Ouch! Those speed leathers are usually just a thin layer of plastic, I hope he at least had some thick longies underneath!
I also think about 40 mph is the top safe speed for most bike frames, wheels, etc. Custom stuff, like Safe builds is another story, and with the right tires and such could haul ass safely. If the fun is in the fabrication, great, but I just shudder to think of going out to mix with traffic at 70 mph on any kind of bicycle wheel and tire. Sooner or later there will be crap in the road and dodging it may be riskier than hitting it. My point is stock bikes are designed for this, and there is still plenty of fun fabrication in converting them. Just more practical when your done, especially since it has a vin number.
Good points about the practicality of it. I guess multiply the effective drag area by 3 to account for "basic safety"(such as the tires and suspension for tackling road debris and some sort of steering( My small 8" scooter wheels almost just ran over a piece of concrete larger than a 2x4 last night and that was scary... but I had lights and it's not motorized), but not necessarily avoiding getting squashed by a distracted zombie-fied humvee driver) and you can still get to 70 mph for ~2000 watts. I guess that isn't too impressive, but getting to high speeds and having a reasonable distance doesn't necessarily cost a ton in energy(and the subsequent batteries needed to store that energy), which can make the package cheaper by a factor of 3-5 compared to an electric Harley or other conventional electric bikes. But I'm not sure what the cost of modern fabrication techniques are to get a coefficient of drag down to <.2, so that point may be moot. I'm pretty sure many buyers won't pride themselves on buying the Aptera for the sticker-price, as compared to other available electric vehicles.
safe
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This is what motorcycle road racing looked like in the beginning.
Notice that they used a fully aerodynamic design back then.
I think what is needed is that people take several parameters:
Rules about motor power - 1000 watts input / 750 watts output Rules about aerodynamics - Limits on the amount of coverage. Rules about pedals - You have to have working pedals....then take those parameters and just see how far you can push the technology to reach a maximum top speed. If you set the rules right then the top speed will be limited by practical reality. (street legal means 20 - 30 mph for most people anyway)
Link
1 MW
Yeah, I wouldn't be trying for 70 on even the hardiest of bike frames, fairings or no.
Ground > my face.
à ² à ²¿_à ² à ²¿
...
à ² wà ²Â
Ground > my face.
swbluto said:
à ² à ²¿_à ² à ²¿
...
à ² wà ²Â
safe
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It really all has to do with wheelbase. Think about if you had a bike that was ten feet long... at 70 mph it would handle really slow and be stable, but then that same bike might have trouble turning. So it's more about a "correct" answer than anything else.Link said:
From my experience with the subject (of which have been at it for 20+ years now) you need about a 52" wheelbase to effectively "solve" the worry about high speed (70 mph) for a bicycle. Most bikes have a wheelbase of about 46". So to get to where you need to be for proper handling it only requires another 6" longer wheelbase to get there.
The 46" wheelbase is for the larger bikes, but the BMX bikes start out at less than 36" so back in the old days when I was doing the Gravity Bikes my first innovation was to stretch the wheelbase to about 48". That completely solved the problem of high speed instability.
Actually the full story on that is this local Road Racer (retired) owned a machine shop (1978?) and I would go over and hang out and asked him the question of what I should do. He was the one that suggested trying a much longer wheelbase.
Rick Schell
http://www.rscycles.com/rebuilding_companies.htm
http://en.wikipedia.org/wiki/1965_Grand_Prix_motorcycle_racing_season
(his specialty all the way back then was cranks)
http://www.two-stroke.com/mailing-lists/gp125/msg08222.html
dogman dan
1 PW
That bike in the pic looks like it could handle 70. Very interesting point about the wheelbase. Wouldn't suprise me at all if the bike in the pic had about the same wheelbase as a steet motorcycle. Cool the way it allows you to tuck behind the handlebars instead of in front of em like I used to in downhill races with freinds. We used to just about grind noses on the front wheel looking for a lower tuck.
I don't think you need harley wheels and tires to be safe, just something that can handle running over a chunk of semi tire without shredding. I keep looking at enduros and street bikes in the 125-250 cc range as interesting bikes to convert. Like with car conversions, smaller, lighter, and maybe even slower, will save a fortune when it's time to buy the battery.
Reading again, maybe we all kinda missed your point in the original post, and focused entirely about a higway vehicle. Reading again, I see you may have really been making a point about efficiency, rather than speed.
I don't think you need harley wheels and tires to be safe, just something that can handle running over a chunk of semi tire without shredding. I keep looking at enduros and street bikes in the 125-250 cc range as interesting bikes to convert. Like with car conversions, smaller, lighter, and maybe even slower, will save a fortune when it's time to buy the battery.
Reading again, maybe we all kinda missed your point in the original post, and focused entirely about a higway vehicle. Reading again, I see you may have really been making a point about efficiency, rather than speed.
The original streamlined bike road racers had one common complaint, "aerodynamic improvements are very hard on the brakes".
A very telling statement and probably part of the reason for stringent rules at least historically.
I use to be the VP for the IHPVA (human power) and it was constantly a battle to keep rules out. It was really organized under the premise of no rules leads to innovation. When drugging became an issue, the IHPVA had suggestions of a Top Fuel Category to allow chemically motivated riders a platform, especially since many were doing it anyway. But since the goals of the organization were also about healthy living, it was nixed.
But interestingly, the theoretical top speed for a human was 75mph in the 80s.
Here is an example of a bicycle set up for high speeds. Essentially setup to do 150MPH but got the wobbles I believe at 143MPH, mostly due to road conditions.
http://www.youtube.com/watch?v=Py94okBKDU0
A very telling statement and probably part of the reason for stringent rules at least historically.
I use to be the VP for the IHPVA (human power) and it was constantly a battle to keep rules out. It was really organized under the premise of no rules leads to innovation. When drugging became an issue, the IHPVA had suggestions of a Top Fuel Category to allow chemically motivated riders a platform, especially since many were doing it anyway. But since the goals of the organization were also about healthy living, it was nixed.
But interestingly, the theoretical top speed for a human was 75mph in the 80s.
Here is an example of a bicycle set up for high speeds. Essentially setup to do 150MPH but got the wobbles I believe at 143MPH, mostly due to road conditions.
http://www.youtube.com/watch?v=Py94okBKDU0
dogman said:
Well, in a way, both. I'm not necessarily a speed demon for the sake of speed but I do like to minimize my time spent doing something uninteresting, like say, driving. But, increasing aerodynamic efficiency also has that ability to cut-down on the overall power and energy requirements, which can drastically cut-down on the cost needed to go a certain speed or a certain distance. Sure, you can spend 3x-5x the amount of batteries to go the same speed the same distance for on a more conventional vehicle, but I was last told that batteries are pretty expensive...
(And, driving a "high-way" rocket like that would be kind of cool for those longer distances. But, unfortunately, I can imagine a few idiotic drivers having a knee-jerk "(S)he's not one of us." reaction and trying to run you over to show you their dominating authority in an attempt to force conformity. So, there's still yet that primal nature of some humans that's going to be a threat on the highway.)
Link said:
I'll attribute you as my inspiration. Btw, where'd you get those characters? It doesn't seem like my charmap has those particular ones.
Link
1 MW
By "bike frame", I really mean like something I can walk into your average store and buy. Bikes made for that sort of thing are a different story, of course, though I'd still wonder how good an idea that'd be around traffic and with 40+lbs of electric whatnot on the bike.
Internet. I'm pretty sure they wouldn't be on a normal North American character map, since I think they're Arabic or something.
swbluto said:Link said:
I'll attribute you as my inspiration. Btw, where'd you get those characters? It doesn't seem like my charmap has those particular ones.
Internet. I'm pretty sure they wouldn't be on a normal North American character map, since I think they're Arabic or something.
safe
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I made and attempted to make a business of selling those back in about 1985 or so. They didn't sell very well because they really only worked well on a downhill and also in those days you needed to spend money to advertise (there was no internet) so it got to a point where I just didn't see any way to get it going and gave up on it.skydog said:
Now I see the value of the aerodynamic form and how it can be integrated into an ebike to come up with something really interesting.
safe
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dogman said:
That's how I see it.We should be permitted a certain set of rules that make going fast pretty hard to do. The aerodynamics are limited, the power is limited, and you need to maintain the ability to be a bicycle and pedal, but after that it's up to the designers to develop the fastest bike given the restrictions.
A last restriction needs to be that the bike handles well... the tracks need to be set up to resemble a typical suburban street with pretty tight corners. Any machine that can't turn is useless and pointless to develop. (these record setting recumbents are sort of a dead end as far as design goes because they are impractical)
Rick:
That is too funny.
I too produced a bicycle fairing for the market in 82'. I sold about 50 of them until my mfg ran into a bad batch of Lexan and gave up.
It was a free form blown Lexan that resembled a 1/2 sphere. On a conventional 10 spd it was quite effective. I ended up modifying the original mold and it was used on some Bonneville canopies, Vetter High MPG bikes and some ultra-light aircraft. But really the cyclist market wasn't that receptive.
I do disagree with the idea that the HPV extreme aerodynamics is a dead end. The european mkt. of street worthy Velocars is one example. (The EV1 is another). Although these are much slower,their performance capabilities are a direct result of older record setting vehicles like the Vector.
But I also believe that we have not seen current available technology incorporated into the high speed aero bikes.
Active aerodynamics will incorporate dynamic body panels that change shape as necessary. Also altering the boundary layer, especially in the tail section, with tiny vacume pumps through a porous body panel can retain the boundary layer longer and then redirect the air to other area like behind the wheels. This could yield a significant performance gain not only for top end vehicles but also for practical vehicles in day to day use.
That is too funny.
I too produced a bicycle fairing for the market in 82'. I sold about 50 of them until my mfg ran into a bad batch of Lexan and gave up.
It was a free form blown Lexan that resembled a 1/2 sphere. On a conventional 10 spd it was quite effective. I ended up modifying the original mold and it was used on some Bonneville canopies, Vetter High MPG bikes and some ultra-light aircraft. But really the cyclist market wasn't that receptive.
I do disagree with the idea that the HPV extreme aerodynamics is a dead end. The european mkt. of street worthy Velocars is one example. (The EV1 is another). Although these are much slower,their performance capabilities are a direct result of older record setting vehicles like the Vector.
But I also believe that we have not seen current available technology incorporated into the high speed aero bikes.
Active aerodynamics will incorporate dynamic body panels that change shape as necessary. Also altering the boundary layer, especially in the tail section, with tiny vacume pumps through a porous body panel can retain the boundary layer longer and then redirect the air to other area like behind the wheels. This could yield a significant performance gain not only for top end vehicles but also for practical vehicles in day to day use.
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