ebike4healthandfitness
10 kW
- Joined
- May 19, 2012
- Messages
- 756
That Electrom is nice. I like how it takes off so smooth as well.
thanks, yes it's coming along nicely.ebike4healthandfitness said:That Electrom is nice. I like how it takes off so smooth as well.
BalorNG said:Interesting thread, lots of good points.
Problem is, however, that one should first read this article and think REALLY hard:
https://motochassis.com/Articles/Aerodynamics/AERO.htm
Basically, 'partial' fairings work very poorly (or even increase drag) - only if your position is truly horrible to begin with - which is the case for a bicycle/motorcycle to be fair.
To *streamline* something imply a fairing that allows *pressure recovery* - as in 'smoothly parting the air in front and converging it in the back'. Partial* fairings do not really allow that, even those that have converging tail section, AND if your ride is stable in high crosswinds it can only mean one thing - the farings is not very effective - a highly streamlined bike is like a wing put on it's side and will inevitably create considerable 'sideways lift' that has significant propulsive component, by the way, but creates even more lateral push that destabilizes that bike and creates a toppling moment proportinal to speed and angle of apparent wind and hight of your CP.
There can be interrupts in the fairings, but they need to be small, and the converging tail needs to be really large to work given imperfect form... it also allows to shift CP rearward, away from steered wheel and therefore decrease the lever side force has on your *trail* lever arm to affect steering directly (very nasty phenomena).
If you want a moto fairing that truly works as intended (decreses your 'MPG' equivalent) and are 'more or less pratical' - look at Vetter fairings .
http://craigvetter.com/
You should still build a bike *around* a fairing by going very low or even zero 'trail' and using other means of getting return-to-center force, preferably a virtual pivot steering, but given previus threads I don't find that eb4hf will understand what I'm even talking about
Otherwise, you can expect only a small effect at best and if your bike have high CRR tires (moped/moto) - even less, because it will be swamped by rolling resistance, but all things that Chalo bought up - weight/bulk/noise/possiblity of damage and if you build it from 'many layers of carbon/kevlar' - COST - are still in effect.
Using a combination of front and rear fairngs AND a flexible lycra sock between them (F40 recumbent, faired LWBs) do work much better than the sum of the parts, but exacerbate 'rider cooling issues' (not a problem on motobike I presume), create significant ingress-egress issues and looks, well, dorky... and still works way from perfect.
I have some ideas how to work around that by using partial and *wearable* fairings that would eliminate the 'ingress/egress' issues by upping the dork factor to eleven but I'm way past caring about that
ebike4healthandfitness said:BalorNG said:Interesting thread, lots of good points.
Problem is, however, that one should first read this article and think REALLY hard:
https://motochassis.com/Articles/Aerodynamics/AERO.htm
Basically, 'partial' fairings work very poorly (or even increase drag) - only if your position is truly horrible to begin with - which is the case for a bicycle/motorcycle to be fair.
To *streamline* something imply a fairing that allows *pressure recovery* - as in 'smoothly parting the air in front and converging it in the back'. Partial* fairings do not really allow that, even those that have converging tail section, AND if your ride is stable in high crosswinds it can only mean one thing - the farings is not very effective - a highly streamlined bike is like a wing put on it's side and will inevitably create considerable 'sideways lift' that has significant propulsive component, by the way, but creates even more lateral push that destabilizes that bike and creates a toppling moment proportinal to speed and angle of apparent wind and hight of your CP.
There can be interrupts in the fairings, but they need to be small, and the converging tail needs to be really large to work given imperfect form... it also allows to shift CP rearward, away from steered wheel and therefore decrease the lever side force has on your *trail* lever arm to affect steering directly (very nasty phenomena).
If you want a moto fairing that truly works as intended (decreses your 'MPG' equivalent) and are 'more or less pratical' - look at Vetter fairings .
http://craigvetter.com/
You should still build a bike *around* a fairing by going very low or even zero 'trail' and using other means of getting return-to-center force, preferably a virtual pivot steering, but given previus threads I don't find that eb4hf will understand what I'm even talking about
Otherwise, you can expect only a small effect at best and if your bike have high CRR tires (moped/moto) - even less, because it will be swamped by rolling resistance, but all things that Chalo bought up - weight/bulk/noise/possiblity of damage and if you build it from 'many layers of carbon/kevlar' - COST - are still in effect.
Using a combination of front and rear fairngs AND a flexible lycra sock between them (F40 recumbent, faired LWBs) do work much better than the sum of the parts, but exacerbate 'rider cooling issues' (not a problem on motobike I presume), create significant ingress-egress issues and looks, well, dorky... and still works way from perfect.
I have some ideas how to work around that by using partial and *wearable* fairings that would eliminate the 'ingress/egress' issues by upping the dork factor to eleven but I'm way past caring about that
You claim a person should use zero trail in order to keep their bike from being affected by crosswinds....but even the author of the first link (which I quoted below) claims he has a confounding factor of increased lateral stiffness of his new suspension which he believed is the reason for the reduced suspectibility of the crosswinds.
"In 1986 I converted a Gold Wing from telescopic forks to one of my "hub centre" front ends, for its owner, Wayne Boys. After he had had it for a while we discussed the various effects that he noticed in normal riding, many observations were as I had expected but I was a bit surprised when he pointed out that it was far more stable in gusty side winds. At first I thought that this was probably just due to the greater lateral stiffness of the new suspension, which is generally more stable anyway. But a bit more thought as to the differences between the two setups, shed a bit of light on why they should behave so differently under these conditions. There seemed to be three main differences, in addition to the stiffness already mentioned ;----- 1. 16" wheel instead of 19", 2. Less trail, 3. A 17 rake angle which needed zero offset between the steering axis and the wheel centre-line to achieve the desired trail. It can be argued that all three of these changes work toward improving the performance in gusts."
Not convincing evidence to reduce trail to very low or zero. His theory needs more work and investigation which would include an experiment to isolate variables.
BalorNG said:Basically, you need to understand what trail *really* stand for, not just lines on paper, and what it does your bike is subjected to considerable impulses of lateral force - can be easily tested by having someone prop up the bike w/o holding the bars and giving the bike a sideways shove. The steering will inevitably point in the same direction - that's what trail does.
ebike4healthandfitness said:That is not trail, that is wheel flop.
Chalo said:ebike4healthandfitness said:That is not trail, that is wheel flop.
No, it's not.
ebike4healthandfitness said:Chalo said:ebike4healthandfitness said:That is not trail, that is wheel flop.
No, it's not.
If a person is pushing on his bike with a certain lateral force and the front wheel ends up turning in the direction of the lateral force that is is caused by wheel flop.
Not all bikes will do that, but bikes with high wheel flop will.
Chalo said:ebike4healthandfitness said:Chalo said:ebike4healthandfitness said:That is not trail, that is wheel flop.
No, it's not.
If a person is pushing on his bike with a certain lateral force and the front wheel ends up turning in the direction of the lateral force that is is caused by wheel flop.
Not all bikes will do that, but bikes with high wheel flop will.
The steering force will happen even if the steering axis is vertical and there is no wheel flop. That's how you turn a shopping cart. Trail is the lever by which you move the wheel's angle.
Ride more. Build more. Tell other people how it is a lot less.
Frank said:I still ride with a 40 year old Zzipper on my road bike. It's worth two gears and is extremely light.
Frank said:I also used to ride with some of those mylar wheel discs on the rear wheel (until they got ripped during a move). I tried them on the front wheel but when a gust of wind almost blew me off the road I changed my mind, lol.
Chalo said:I have already discussed flop with you in another thread. I understand it from observing it for myself. But that's not what we're discussing. We're talking about how steering trail allows crosswinds to steer a faired bike. Flop allows the force of gravity to steer a bike once the steering angle departs from center. That's different.
Trail is the lever that converts a sideways force into a steering input.
Chalo said:We're talking about how steering trail allows crosswinds to steer a faired bike. Flop allows the force of gravity to steer a bike once the steering angle departs from center.
ebike4healthandfitness said:Chalo said:We're talking about how steering trail allows crosswinds to steer a faired bike. Flop allows the force of gravity to steer a bike once the steering angle departs from center.
Trail is what resists crosswinds steering the bike.
In that Foale article (Balor linked) he attributes the reduction in trail, reduction in wheel size and elimination of fork offset as part of the reason the motorcycle became less resistant to crosswinds. However, it is very obvious any contribution from those changes was due to the much greater reduction in wheel flop that was made. (Trail was reduced, but wheel flop was reduced by a much greater amount than trail was.)
MoneyPit said:Frank said:I still ride with a 40 year old Zzipper on my road bike. It's worth two gears and is extremely light.
I just found mine cleaning out the back bedroom over the weekend. Sent it straight into storage. Mine is a *really* old one that predated the handlebar rods and fit over top of the brake hoods on ram-horn style road bars. You velcro'd it on and pretty much rode on the drops only, which kept you in a tuck. It was the smaller of the two sizes shown above. And yes it was a freaking miracle for drag reduction. Worth two gears? That sounds about right. I rode with mine on downhills in the Lower Sierras and you could well exceed what was otherwise terminal velocity for a road bike. Into the mid-sixties instead of the mid-fifties. Needless to say once you started rolling, on 700x20C analog racing bike tires you tried very hard to never touch the brakes.
Everything was great until you spun around a corner and experienced a crosswind, which would always take you within a hair of having the handlebars torn right out of your hands. It was terrifying, but you ride like that for the adrenaline so it didn't stop me (being aged 16-18 didn't help). That and the inability to comfortably lean on the hoods were the 'only' drawbacks.
Frank said:I also used to ride with some of those mylar wheel discs on the rear wheel (until they got ripped during a move). I tried them on the front wheel but when a gust of wind almost blew me off the road I changed my mind, lol.
oh my god I had totally forgotten about those. Mine were some kind of rigid plastic that clipped to the spokes. the fact they didn't flex with the wheels at high speed and rattled a lot was one issue, but the whole barn door thing was the dealbreaker. I can remember leaning waaaay over to one side trying to keep from getting blown off the road ripping down the Los Laureles grade and that was the last time I played with those.
Nowadays, I think motors take the place of the benefit of fairings at the kind of relatively low speeds ebikes achieve.
BalorNG said:ebike4healthandfitness said:Chalo said:We're talking about how steering trail allows crosswinds to steer a faired bike. Flop allows the force of gravity to steer a bike once the steering angle departs from center.
Trail is what resists crosswinds steering the bike.
In that Foale article (Balor linked) he attributes the reduction in trail, reduction in wheel size and elimination of fork offset as part of the reason the motorcycle became less resistant to crosswinds. However, it is very obvious any contribution from those changes was due to the much greater reduction in wheel flop that was made. (Trail was reduced, but wheel flop was reduced by a much greater amount than trail was.)
If you say one thing about eb4hf, one thing only - is that that he can be relied upon
Chalo said:Excellent low center of mass handling qualities:
[youtube]5UBWTshFEIg[/youtube]
ebike4healthandfitness said:BalorNG said:ebike4healthandfitness said:Chalo said:We're talking about how steering trail allows crosswinds to steer a faired bike. Flop allows the force of gravity to steer a bike once the steering angle departs from center.
Trail is what resists crosswinds steering the bike.
In that Foale article (Balor linked) he attributes the reduction in trail, reduction in wheel size and elimination of fork offset as part of the reason the motorcycle became less resistant to crosswinds. However, it is very obvious any contribution from those changes was due to the much greater reduction in wheel flop that was made. (Trail was reduced, but wheel flop was reduced by a much greater amount than trail was.)
If you say one thing about eb4hf, one thing only - is that that he can be relied upon
Balor, your recommendation for zero trail set up in bicycles to resist crosswinds is absurd just like your previous idea that low center of gravity hurts stability in single track vehicles.
Hopefully we don't have to go 10 pages in this thread like we did the other one so you can figure it out.
I mean seriously it is just common sense that you need to do some more reading when you thought the vehicle shown below poor handling was due to low center of gravity.
Chalo said:Excellent low center of mass handling qualities:
[youtube]5UBWTshFEIg[/youtube]
In contrast, just look at how the Electrom (which is also low center of gravity) in it's YouTube videos handles so beautifully in comparison.
BalorNG said:ebike4healthandfitness said:BalorNG said:ebike4healthandfitness said:Trail is what resists crosswinds steering the bike.
In that Foale article (Balor linked) he attributes the reduction in trail, reduction in wheel size and elimination of fork offset as part of the reason the motorcycle became less resistant to crosswinds. However, it is very obvious any contribution from those changes was due to the much greater reduction in wheel flop that was made. (Trail was reduced, but wheel flop was reduced by a much greater amount than trail was.)
If you say one thing about eb4hf, one thing only - is that that he can be relied upon
Balor, your recommendation for zero trail set up in bicycles to resist crosswinds is absurd just like your previous idea that low center of gravity hurts stability in single track vehicles.
Hopefully we don't have to go 10 pages in this thread like we did the other one so you can figure it out.
I mean seriously it is just common sense that you need to do some more reading when you thought the vehicle shown below poor handling was due to low center of gravity.
Chalo said:Excellent low center of mass handling qualities:
[youtube]5UBWTshFEIg[/youtube]
In contrast, just look at how the Electrom (which is also low center of gravity) in it's YouTube videos handles so beautifully in comparison.
To be frank, 'zero trail' is likely not optimal as well, but extremely short is likely the way to go, and you want a steering damper to accompany it... you want it anyway!
As for common sense and figuring it out... let's just say: LOL.
And judging fine nuances of steering based on a few youtube videos is SO rational and scientific )
ebike4healthandfitness said:Comparing the Electrom to that sloppy handling low racer is anything but fine nuances. It's a night and day difference in stability.
BalorNG said:bicycle 'rideability' is combination of interacting/conflicting factors that are hard to disentangle and need either extremely good knoledge of theory, or a lot of MINDFUL practice, preferably both.
ebike4healthandfitness said:Here is what I see:
1. We know the new suspension has increased lateral stiffness.
2. We know the new wheel is smaller which reduces trail and wheel flop. The smaller wheel also presents a smaller surface area for crosswinds to work on.
3. The new fork has no offset which increases trail and somewhat increases wheel flop.
How are we getting the idea of zero trail from the above info? If anything the trail reduction is probably very small because the removal of fork offset is going to cancel out a good amount of trail reduction brought about by the reduction in wheel diameter. If anything I see this an being an experiment in reducing wheel flop, reducing wheel surface area for the wind to act on coupled to a suspension with increased lateral stiffness. The trail reduction is almost laughable compared to the impact of those other three factors.