Amateur aerodynamics
- Thread starter Jim Gerwing
- Start date
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John Tolhurst
Zen MBB Master
transition from body to fairing
I have a selectable screen orientation, so no worries.
I see what you are aiming at. The difficulty is always the transition from the body to the tail fairing. Or from the helmet. On the RAAM bike you may have noticed we put the bottle cages right ont he back of the headrest, and the headrest cushioning without gaps to the body.
I have a selectable screen orientation, so no worries.
I see what you are aiming at. The difficulty is always the transition from the body to the tail fairing. Or from the helmet. On the RAAM bike you may have noticed we put the bottle cages right ont he back of the headrest, and the headrest cushioning without gaps to the body.
Jim Gerwing
Well-Known Member
Commentary
Two features that bear explanation:
A) From Eric (I believe) I covered the rear wheel in storm door, heat shrinkable plastic made possible by virtue of using the braking surface on the rims which are freed up by the disc brakes. One draw back is the space left open near the hub on the brake side due to lack of clearance by the caliper housing which I have a work around planned for the next version. I have not experienced a performance benefit yet but neither a detriment. It makes a cool sound when I glance off small rocks.
B) From Fred (I believe, Flinstone) I used double layered cardboard to fashion my first ever tail box complete with internal bracing. No aerodynamic penalties (or benefits) incurred but I did discover a very quick method of turning a chick magnet into an object of scorn and derision. I am encouraged, though, as I have for my next post tail box 2.0, a quantum leap forward in cardboard construction.
Two features that bear explanation:
A) From Eric (I believe) I covered the rear wheel in storm door, heat shrinkable plastic made possible by virtue of using the braking surface on the rims which are freed up by the disc brakes. One draw back is the space left open near the hub on the brake side due to lack of clearance by the caliper housing which I have a work around planned for the next version. I have not experienced a performance benefit yet but neither a detriment. It makes a cool sound when I glance off small rocks.
B) From Fred (I believe, Flinstone) I used double layered cardboard to fashion my first ever tail box complete with internal bracing. No aerodynamic penalties (or benefits) incurred but I did discover a very quick method of turning a chick magnet into an object of scorn and derision. I am encouraged, though, as I have for my next post tail box 2.0, a quantum leap forward in cardboard construction.
More!
Have you considered fairing the entire rear from the bottom of the seat to the top of the headrest?
Have it taper together a foot or so past the rear wheel. That would give you lots of space to put all the sponsors names that will be clamoring to support you and this aerodynamic marvel of modern technology.
And it might make you go faster too!
Have you considered fairing the entire rear from the bottom of the seat to the top of the headrest?
Have it taper together a foot or so past the rear wheel. That would give you lots of space to put all the sponsors names that will be clamoring to support you and this aerodynamic marvel of modern technology.
And it might make you go faster too!
bladderhead
Zen MBB Master
It is an Australian bike.
It is an Australian bike.
It is an Australian bike.
Andrew 1973
Zen MBB Master
^ win
Good one.
Good one.
Jim Gerwing
Well-Known Member
Tail box 2.0 released!
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Charles.Plager
Recumbent Quant
Find yourself a good hill and
Find yourself a good hill and a GPS (maybe a smart phone). Ride to various speeds and coast from a given point. You can solve for your CdA (and rolling resistance) of your different setups and that will give you some real feedback as to how much different tail boxes/fairings/aero helmets/wheels are working for you.
Find yourself a good hill and a GPS (maybe a smart phone). Ride to various speeds and coast from a given point. You can solve for your CdA (and rolling resistance) of your different setups and that will give you some real feedback as to how much different tail boxes/fairings/aero helmets/wheels are working for you.
randyspann
Well-Known Member
But Charles -- In this case
But Charles -- In this case the hill would go up! Maybe he would roll backwards!
But Charles -- In this case the hill would go up! Maybe he would roll backwards!
Jim Gerwing
Well-Known Member
Aero update - a bad idea
Well, not necessarily a bad idea but I now know of an aero addition that doesn't promote 'dynamics'.
The major problem seemed to be the fairing of my body to the added back piece. As well, one aero site I visited suggested as a rule of thumb that whatever width you present to the direction of travel, you need at least 3X the length to the point where the separated air comes back together (aspect ratio). As the title of the thread suggests, I am not an aero dynamicist, but after attempting to fill the space between body and arms with foam, I gave it up and faired the underside of the seat back to the trailing edge of the back wheel which seems to add no harm (testing in progress) and, this is bad science, I know because I am adding another variable, I 'storm-doored' my front wheel as well. (Which I tested tonight in more environmental wind than what I would have considered ideal) The results tonight were inconclusive but encouraging. I'll report after a fair trial. As for the back piece, poor showing.
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Well, not necessarily a bad idea but I now know of an aero addition that doesn't promote 'dynamics'.
The major problem seemed to be the fairing of my body to the added back piece. As well, one aero site I visited suggested as a rule of thumb that whatever width you present to the direction of travel, you need at least 3X the length to the point where the separated air comes back together (aspect ratio). As the title of the thread suggests, I am not an aero dynamicist, but after attempting to fill the space between body and arms with foam, I gave it up and faired the underside of the seat back to the trailing edge of the back wheel which seems to add no harm (testing in progress) and, this is bad science, I know because I am adding another variable, I 'storm-doored' my front wheel as well. (Which I tested tonight in more environmental wind than what I would have considered ideal) The results tonight were inconclusive but encouraging. I'll report after a fair trial. As for the back piece, poor showing.
Jim Gerwing
Well-Known Member
Front wheel covered
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Jim Gerwing
Well-Known Member
Commentary on front wheel cover
My photography skills are also amateurish. I attempted to get a background and light exposure that would show off the sheeting. My apologies for the distortion but the pic does show the nice taught fitting over the spokes. You can see the valve-stem access. What you can't make out so well is the cardboard (cereal box) center 'halo'. Where this halo ends I put a cardboard hub on the inside of the spokes to prevent a large gap and possible 'parachuting'. Whether or not this is a potential/actual effect, I don't know, I'm an amateur working on intuition. When I put the wheel back on, I had an issue with the placement of my computer magnet but this was easily remedied with a slit, repositioning and a piece of tape over the incision.
In terms of performance, one must be very careful with crosswinds and, in particular, gusts. I have been using this in low wind conditions but buffeting from large traffic requires attention. This cover seems to have a greater effect on aero benefits than the rear cover.
On a side note, I shaved my legs and arms, and bought a skull cap to cover my ears. So, take note, you are dealing with an amateur and an 'enthusiast' as they say in England.
Slipping the surly bonds of earth...
JG
My photography skills are also amateurish. I attempted to get a background and light exposure that would show off the sheeting. My apologies for the distortion but the pic does show the nice taught fitting over the spokes. You can see the valve-stem access. What you can't make out so well is the cardboard (cereal box) center 'halo'. Where this halo ends I put a cardboard hub on the inside of the spokes to prevent a large gap and possible 'parachuting'. Whether or not this is a potential/actual effect, I don't know, I'm an amateur working on intuition. When I put the wheel back on, I had an issue with the placement of my computer magnet but this was easily remedied with a slit, repositioning and a piece of tape over the incision.
In terms of performance, one must be very careful with crosswinds and, in particular, gusts. I have been using this in low wind conditions but buffeting from large traffic requires attention. This cover seems to have a greater effect on aero benefits than the rear cover.
On a side note, I shaved my legs and arms, and bought a skull cap to cover my ears. So, take note, you are dealing with an amateur and an 'enthusiast' as they say in England.
Slipping the surly bonds of earth...
JG
marshall2389
Guru
sweet! Looks good
sweet! Looks good
sweet! Looks good
Jim Gerwing
Well-Known Member
Video
Try Jim Gerwing on Facebook. '56km/hr' works on my desk top (but not my iPad because it doesn't support adobe flash player).
That's 56k per hour (instantaneous) not 56km in one hour.
JG
Try Jim Gerwing on Facebook. '56km/hr' works on my desk top (but not my iPad because it doesn't support adobe flash player).
That's 56k per hour (instantaneous) not 56km in one hour.
JG
Jim Gerwing
Well-Known Member
Front fairing
My first front fairing is barely visible on my Facebook video. I tried another idea on the weekend but it was a disaster except that I got a new idea. See below. If the shape turns out, I may use it for a fiberglass version.
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My first front fairing is barely visible on my Facebook video. I tried another idea on the weekend but it was a disaster except that I got a new idea. See below. If the shape turns out, I may use it for a fiberglass version.
