Aerodynamics

[Modbikemax]

Nice. In the end there is no substitute for good gear. I have read the same about the limited benefit of flattened spokes.
I think they improve their performance by using fewer spokes too. My. Mavic wheels only have 12 spokes. I notice yours only has a few spokes per wheel.

My idea will require testing and in the end the added weight will probably negate the benefits.
However the modifications make the spokes over 7mm wide and about 2.5mm wide and reduced drag can be achieved by increased aspect ratio, the ratio of width x length. That's why long and skinny is more aero than short and fat.
So there is some promise in getting some result.

Plus it allows the use of some colour to, hopefully, make it look cool.

 

[tahustvedt]

It'll make the bike more visible too. Making something yourself is fun no matter how efficcient it becomes. Good luck with your testing.

Here's my current project. I'm sick of my car and want something comfortable to ride to work and the shop in winter. It's not the perfect aerodynamic shape, but it should be easy to get into and out of, and should be reasonably aerodynamic compared to a bicycle. I also want it to be simple to build so that I don't have to make giant molds. It's a work in progress. I'm drawing and changing every day. I hope to finish it by spring. It'll be slightly bigger than the usual velomobiles.

 

[speedmd]

Nice looking bike.

Great page to help compare some options. http://www.southampton.ac.uk/~aijf197/Wheel Aerodynamics/Results and Discussion.htm
As you can see, less spokes is certainly faster, but certainly weaker. Not much to gain for a commuter. If there is some prize money, then a different story.

Some on shapes.

 

[LockH]

Folks... re the aero part... PEP store has one of these:



So... parachute breaking anybuddy? Or wind sailing if goin same way etc.

 

[DrkAngel]

Couple aero-dynamic representations and subsequent drag.

Most interesting, to me, was that a half sphere produces less drag than a sphere! ... ?

 

[speedmd]

Half sphere has a cleaner separation of flow on the back half. Only a relatively minor improvement.

 

[LockH]

More aerodynamics re bicycle
[img]http://i1367.photobucket.com/a...res/Albert_Joseph_Penot_zpsd08b882b.jpg[/img]

http://endless-sphere.com/forums/viewtopic.php?f=12&t=8099&start=700#p766887

 

[Modbikemax]

I see there are several manufacturers of disc wheel covers and some simple DIY examples mainly used for bike polo and track racing. I might give that a go, it looks easier and possibly more effective.

http://www.ebay.com.au/itm/221463068189?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

 

[John in CR]

Disc covers on a hubmotor wheel means less cooling for the motor.

 

[Modbikemax]

Disc covers on a hubmotor wheel means less cooling for the motor.

I don't see it being a problem, it is very under stressed now, even going up long hills at full throttle it gets only slightly warm.
I would leave the flat sides exposed and the stator is bolted to the forks through the axle which acts as a heat sink for the windings.
I think it would make almost no difference.

 

[speedmd]

Discs on the front are crazy dangerous in even slight cross winds. You will get yourself killed. Don't waste your money looking for tiny advantages at the expense of safety. Even on the rear they get the bike to dance around and become a hand full when out in the open breezes.

 

[bowlofsalad]

Disc covers on a hubmotor wheel means less cooling for the motor.

I don't see it being a problem, it is very under stressed now, even going up long hills at full throttle it gets only slightly warm.
I would leave the flat sides exposed and the stator is bolted to the forks through the axle which acts as a heat sink for the windings.
I think it would make almost no difference.

Almost no difference.

The only difference which makes no difference is no difference. Do you have a temperature sensor in your hub?

 

[John in CR]

Disc covers on a hubmotor wheel means less cooling for the motor.

I don't see it being a problem, it is very under stressed now, even going up long hills at full throttle it gets only slightly warm.
I would leave the flat sides exposed and the stator is bolted to the forks through the axle which acts as a heat sink for the windings.
I think it would make almost no difference.

I can just about guarantee the difference in heat dissipation is more watts than the disk will save in mechanical effort, though that is apples and oranges. It may not be not enough for a failure, but a higher temperature is guaranteed, which means more resistance in the windings and lower efficiency. Do you wear something to make your legs an airfoil shape? I'm sure that would have greater effect. What about an aero helmet like track racers wear, or a tailbox shape for your back and rear to improve the separated flow as well as give you some extra storage space as an aero backpack? Those will all make a marked difference and none of them come with the significant risk of side wind steer. If it successfully made the front match and look as good as the rest of the bike, then sure, but I question whether it would look better than spokes with some rim and spoke coloration.

Maybe I'm just jaded because I tried some cheap covers for a 20" that didn't work out.

 

[veloman]

I use a slim fitting backpack (dueter race) and it does help a little. There are motorcycle backpacks that are good for this too.

 

[Modbikemax]

So far I have found that Most things which are considered common knowledge in the area of cycling have more to do with myth than fact. Shaved legs and Lycra to mention a few.
I am sure if I was racing a twitchy front wheel might be an annoying problem but I doubt it will kill me. Before I spend up on a commercial product I might make one out of cardboard and test the myth. It is more likely to be useless than deadly.

I am running a stock motor/controller setup and even after vigorous use is no more than body temperature.
I have a temperature calibrated hand, if you look closely you probably do too.
40 degrees is hot to touch and 50 you can't hold your hand on. I have been around electronics for a long time and I was surprised the thing didn't get much hotter. Your average pool pump motor runs hot enough so you can't hold your hand on it and those thing last for years running up to 8 hours a day.
Things would be different if I start to sting it up a bit but in the stock condition I consider it pretty bullet proof. And that's the whole point of this bike, to see how well it can do with a stock motor.

 

[Chalo]

So far I have found that Most things which are considered common knowledge in the area of cycling have more to do with myth than fact. Shaved legs and Lycra to mention a few.

FWIW, shaved legs are about seeing how badass your leg muscles look (which could in fact make you faster if you are using pedal power) and about not having hair in your road rash to impede healing. Lycra doesn't flap, which is better aero (compared to baggy clothes) than anything you can do to the bike itself.

I don't shave my legs because I find it more than enough hassle just to shave my face, and I don't wear lycra shorts much because they don't have pockets. Plus I just ride slowly almost all the time, which means any aero aids would tend to be insignificant.

 

[Modbikemax]

I'm told if you shave your pubes it makes your dick 'look' bigger, but it doesn't make it bigger
Wearing Lycra makes you look like a cycle racer, but it doesn't make you one.

Check this out its a hoot

http://www.aliexpress.com/item/size-700C-FIXED-GEAR-wheel-cover-pvc-sealing-cover/990598293.html

 

[Hornet dave]

Im guessing most ebikers are sitting in a mostly upright position for comfort purposes. Also, im guessing ebikers as a whole tend to go at faster speeds than your normal commuter or recreational rider. That would mean ebikers would have more aero drag from the riders torso than other types of riders. So it seems that a device which minimizes torso drag would be beneficial to those ebikers who desire range or speed.

My thought is a jacket or backpack of some sort, worn by the rider, which acts as an afterbody fairing. It would have to taper iowards the rear, and extend a couple feet behind the rider. Prototyping could work with a ratty old jacket, duct tape, and some cardboard or coroplast. It would also look dorky as hell but imagine if 30 mph could be had for the same power as 20 mph; a 4500 mile trip would go a lot quicker.

 

[Frank]

I still have the Zzipper I bought 30+ years ago for my road bike which helped go faster for the same input (me). I used to ride with a rear wheel cover which helped a bit but the front wheel cover I tried got taken off pretty quickly after a cross-wind changed lanes for me.

 

[speedmd]

Agree, try the cardboard front covers before spending $$$ on them. You will see for yourself as I found out if the winds are out. I was lucky and only ended off the side of the road and not into head on traffic. If the roads are bumpy the bike gets pulled out from under you very suddenly also. Not any faster if your sitting out the ride waiting for the winds to die down. What ever you do have them easily removable as it is a long learning curve to master riding a front disc.

Agree also on dropping your head and torso. Center bars and a low position will make more difference than anything you can do to the bike.

 

[DrkAngel]

The rather flat chest-torso of an athlete puts a cyclist at a severe aerodynamic advantage!

Advantageous would be a a protruding beer belly ...
Lacking that ...
Mounting a ¼ or ½ keg on the front of your bicycle as a partial air dam would give a decided AA (Aero Advantage).
And should, over time, help produce the desired beer belly.
There is evidence that some surface texture does reduce aero drag.
So ... a big bare hairy beer belly might be an excellent model for aero effectiveness!

The ultimate unassisted eCyclist form, however, might be a severely pregnant female with long flowing hair.
Long flowing hair should moderate rear turbulence nicely ... ?
Or hair could be "producted" into an effective tail form!

 

[John in CR]

I'd argue that the beer belly isn't of help, since sitting upright is a tremendous aero drag. On a related note bending forward into a tuck may make the beached whale quite aero, since this beached whale has had his ebike over 100mph, something the skinny guys have yet to manage.

 

[veloman]

Lycra is no myth. Many good reasons for it for the cyclist who doesn't mind the look. It IS significantly more aero, probably worth a 10% increase in speed, maybe more if you have baggy clothes on. I don't normally wear lycra on my ebike, but I always do when i go road cycling. It's also a lot cooler since it doesn't hold heat in, and is very thing, and moisture wicking.
On my ebike, I like wearing my semi fitted Greg Norman synthetic polo shirts. With a backpack on, it's not a big drag, and I look normal, and they are good for hot weather. Shorts are gym shorts in the summer, like mesh. I prefer a non-baggy casual clothes look anyway, so for on the ebike, I don't change much. I just stay away from anything baggy.

Leg shaving is mostly tradition. But a lot of roadies who don't race, we don't shave our legs. I use to, when I raced every weekend. It's really not about aero.

Position on the bike is the biggest thing. And I've YET to see anyone in person on ebike who rode in a slightly aero position. Comfort is more important than battery range. On my fairing ebike, with the low seat, my power consumption is drastically lower at 25+mph. But I can't pedal unless I stand.

Get a recumbent or time trial bike if you want aero and ability to pedal.

 

[veloman]

It would also look dorky as hell but imagine if 30 mph could be had for the same power as 20 mph; a 4500 mile trip would go a lot quicker.

You will need a faired recumbent to achieve that much of a reduction. Making a typical upright cyclist aero is mostly a dead end. The best that can be done is do what I did an put the seat as low as possible, and far back, make a front fairing with sides, and stretch out in a tuck. Can't pedal though.

 

[DrkAngel]

30mph seems to be a break point.
A lowered tuck position is more ... efficient, than sustainable assist from a "proper" pedaling position.