BikeTechReview.com

  • Increase font size
  • Default font size
  • Decrease font size
Home Forum
Welcome, Guest
Username Password: Remember me

Box rim rear vrs any reputable disk, bike no rider
(1 viewing) (1) Guest
  • Page:
  • 1

TOPIC: Box rim rear vrs any reputable disk, bike no rider

Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26942

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
I was hoping to find some windtunnel data that compares a box rim wheel with any of the mainstream reputable disks with the test on the bike with no rider. I had constructed my own disk with a spooked wheel two years ago and took it to the windtunnel last year. I had thought that I would have been able to use one of the zipp disks at the windtunnel to compare against but was not allowed to. I was thrilled with the actual results and want to get a idea on how it stacks up against the industries bests.

thanks
Jason

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26947

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
No box section wheel results vs a disc wheel while installed in a bike, but, there is 3-spoke vs discs in a bike here:

biketechreview.com/store?page=shop.produ...5&category_id=10

..also, wheel alone data here:

biketechreview.com/store?page=shop.produ...2&category_id=10
-kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26950

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
Yeah it seems I'm out of luck I've searched my heart out, just wish I had known to bring a borrowed disk to test.

whats the trick to attaching the file by the way, I was going to attach my windtunnel data but it seems to be evading my capabilities.

thanks
Jason

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26951

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
here are the allowed file types for attachments:

zip,txt,doc,gz,tgz

if it is something other than that, email me, and I'll make something work for you.
Attachments:
-kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26953

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
yaw angle drag(watts)

20.0 147 119


15.0 143 120


10.0 135 120


5.0 128 113


0.0 125 116

-5.0 127 114


-10.0 132 114


-15.0 136 112


-20.0 138 109
first colum is yaw angle, second is the spoked box rimmed rear, thrid is my homemade disk aka the "chunky churner", due to its lumpy appearance and 7pound mass.

For an average savings of 17.6 watts between all the yaw angles I was definetly pleased, it was certainly worth the effort. Note wheel was made by filling a spooked easton wheel with insulation foam than layering fiber glass on top.
Last Edit: 5 years, 6 months ago by howardjd.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26954

  • lanierb
  • OFFLINE
  • Fresh Boarder
  • Posts: 3
  • Karma: 0
HED has aero data on their website. Go to the page for the Stinger disc: www.hedcycling.com/stinger/default.asp?content=Disc and click on the tab "Aero Data".

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26955

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
Thanks apreciate it, don't really know how I over looked that. Thought I had checked all the manufacturers sites throughly. Now depending on how the test was done Im either just pleased or really darn pleased with my results. Im assuming it was at 30mph and that it was done wheel only. My test was done on the bike which for the rear wheel makes the savings less significant, true? Their test for thier best disk averaged 19watts savings over all the yaw angles, with my disk weighing in at 17.6 watts avg savings between all the yaw angles. Now I'm guessing a standard OE wheel would be similar to the box rimmed powertap rear I used. Well regardless I know the "Chunky Churner" definetly shaves a good deal of watts. Wish I had the bucks to test my other two creations, one of them being a 12 pound disk I named the "Air Hammer" which has a much more textured rough surface than any of the disks available.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26959

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
beta      translational watts @ 30mph?
                 wire wheel                  chunky churner
                 
20.0              147                              119    
15.0              143                              120
10.0              135                              120
5.0                128                              113
0.0                125                              116   
-5.0               127                              114
-10.0             132                              114
-15.0             136                              112
-20.0             138                              109


thanks for this. to help place these numbers in context, could you also post more information/pictures of the setup and experimental methods?

Your description of the chunky churner reminds me of a test we did here in SanDiego with a summer science camp. They covered wal-mart helmets in play-dough and measured axial force before and after - there were chunks of watts saved in this exercise for sure!
-kraig

Last Edit: 5 years, 6 months ago by kraig. Reason: fix code table formatting

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 6 months ago #26960

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
The test was done at the A-2 windtunnel in charalotte. It was done by comparing a rear wheel exchange between a spoked powertap rear with the 'chunky churner" at a sweep of -20 deg to 20deg in increments of 5deg's. So wheel on bike no rider. And the test was done at 30mph. I'll tell you one thing it was a lot of fun goning and wish I had the money to make more trips! There is so many types of test I want to do I'd need to be a millonaire to keep up with them.

The wheel was constructed of foam and fiber glass over top a stiff guaged easton rear wheel. After layering the fiber glass on top of the foam the surface had come out fairly lumpy and rough, all though I wanted rough I was unsure about the lumpy. I then took the wheel in to show a bike mechanic at Cycles de Oro greensboro, named Charles, the wheel. He had previously worked in a wind tunnel testing stuff for race cars and when he saw the wheel he said the texture would work great, I trusted him at left it be. He is also the person whom informed me of Mosers huge wheeled bike and Sosenkas 3.2 kilo rear, and hence why the disks weighs 7 pounds. After putting the finishing touches on it I put the disk through some test runs, I only have a power tap so I could'nt use power to test the wheel. I tested it against a tri spoke rear using perceived exertion and determined is was a least equally as fast possibly more, and that the wheel was more ridable for me. I raced on it at three races, one being a 28 mph ten mile time trial at the lowes motor speedway which claimed the 20-24 age group record for a time, then at two triathlons. The second triathon was Augusta 70.3 and a race I was trying to turn pro at, at mile I think 40 my bike got stuck in the big ring(56) and I was forced to pedal at a super low cadence going up the hills and then sustained a groin injury. Even limping to the finish of the bike and then dropping out of the race I still averaged over 25mph on the bike and the fastest split in my age group. It will be 2 years ago this september and I'm still trying to recover from the injury(oseitis pubis).

The attachement is a photo of the chunky churner before paint job and after, the white blades look pretty cool when the wheel gets going.
Attachments:
Last Edit: 5 years, 6 months ago by howardjd.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26963

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
howardjd wrote:
The test was done at the A-2 windtunnel in charalotte. It was done by comparing a rear wheel exchange between a spoked powertap rear with the 'chunky churner" at a sweep of -20 deg to 20deg in increments of 5deg's.


Cool - did you measure side force and roll moment at A2 as well (these are standard measures at other tunnels, so I thought I'd ask)? -> both of those might be of interest considering your hypothesis mentioned in the other thread. If those quantities were measured, maybe you could share those results?

How many spokes, what rim, and what tire/size were used on the powertap wheel? What tire/size was used for the chunky churner? Were the same cassettes used for both wheels?

what bike were the wheels tested in? did you control for crank and pedal position? if the tire diameters were different, did you control for seat tube/tire spacing?

So wheel on bike no rider. And the test was done at 30mph. I'll tell you one thing it was a lot of fun goning and wish I had the money to make more trips! There is so many types of test I want to do I'd need to be a millonaire to keep up with them.


Having limited funds is good for clarifying what is/is not worth testing, IME.
-kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26965

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
The control spoked wheel 32spoke with a mavic open pro rim and had a serafas seca 700X23 tire the Chunky Churner had a Zaffro Slick 700X23.
Neither Side force nor roll( I'm guessing this is watts to spin?) were measured. I did ask about watts to spin but that data was unavailable.
Crank and pedal position was controlled for.
The test was done on a P-3 with a Hed Stinger on the front.
Due to the nature of the Churner it had to sit about 5mm farther back then the spoked wheel.
Cassettes were the same.
Really wish I would have brought my Trispoke in to test against!

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26966

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
howardjd wrote:

Neither Side force nor roll( I'm guessing this is watts to spin?) were measured. I did ask about watts to spin but that data was unavailable.


Thanks for the additional info. Did you do any repeats to see how repeatable the balance and the protocol was?

Tires can be a biggie, but, it sounds like the comparison you did shows that the chunky churner produces less axial force than the wire spoked wheel on the A2 balance. Why didn't they report side force or roll moment? (Roll moment is the moment about the longitudinal axis of the bike, and not the moment about the longitudinal axis of the rear hub).

Does the watts to translate of your setup, in general, seem high to you? Was data corrected for beta, and strut tares removed? Photos showing the two setups might go a long way in shedding light on this topic.
-kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26967

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
Hm I'm not sure about all those things. What is Axial force? Beta? Strut Tares? I have a video of the test I can email along with the full spread sheet of info I received with my visit If I could get your email. This was the only test I have done at the windtunnel as I'm out of the service and in school and no longer have a source of income. I had to use savings to do that test and was considering another but decided against it because of the cost. I most likely won't be able to go back until I'm employed again. I'll call the windtunnel and ask them if these other controls in testing your talking about are used. Oh yeah as far as repeats it seems that for each angle two data points were taken and averaged.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26968

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
I do suppose the watts to translate seems a little high for the bike by itself. With me on the bike at 30.4 mph at -10deg yaw there was 420 watts of drag, no aero helmet, normal cycling shorts and a short sleeve under armor shirt, and with the churner. I'm 190 pounds 5' 11'' just to give some perspective on the drag.
One thing that interested me about the test was how for the Churner between 0 - 20 deg yaw the wattage dipped a little from zero deg came back up a little then leveled off, then for 0 to -20 deg the wattage actually decreased as the yaw angle increased. But for the spooked wheel the wattage steadily increased from zero degrees out to both 20 and -20 deg. Could this suggest a lift effect?

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26969

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
Here's some photos of 20deg for both set ups.
Attachments:
Last Edit: 5 years, 5 months ago by howardjd.
The following user(s) said Thank You: kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26970

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
howardjd wrote:
Hm I'm not sure about all those things. What is Axial force? Beta? Strut Tares?


axial force: one of a few, limited pet peeves - "drag" is a wind axis coordinate system term. axial force is a body-axis coordinate system term. since we care about resistive forces not in the wind axis coord system, but rather, in the body axis coordinate system, the force we are interested in talking about is axial force and not drag. this matters when discussing crosswind resistive forces.

Beta: this is the angle between the direction of travel and the apparent wind vector.

strut tares: opinions vary on whether or not to include the support structure when reporting axial force. I could go either way, it's just helpful to know how the data are being reported to help put things in context.



I have a video of the test I can email along with the full spread sheet of info I received with my visit If I could get your email. This was the only test I have done at the windtunnel as I'm out of the service and in school and no longer have a source of income.


Thank you for your service! Send me what you feel comfortable sending to kdubenterprise at roadrunner dot com.

I'll call the windtunnel and ask them if these other controls in testing your talking about are used. Oh yeah as far as repeats it seems that for each angle two data points were taken and averaged.


Any word from the tunnel? I guess I was thinking about repeatability not in terms of intra-run repeatability, but rather, inter-run repeatability (i.e, take the wind down - take the bike out of the fixture, put the bike in the fixture, then take the wind up and re-take data).

Here's some math on the topic of balance uncertainty (and a bit of repeatability):

biketechreview.com/performance/testing/4...d-tunnel-uncertainty

and some nuggets on year over year repeatability for a wheel I've tested in multiple tunnels over the last 10 years:

biketechreview.com/blog/repeatability-an...ego-wind-tunnel.html

When it comes to a static assembly like a riderless bike, what you are describing (two runs per beta within a setup) could be accomplished by just taking a longer duration sample (ergodicity, I think is the fancy term that circles around this topic a bit). What was the time period over which the two data points you mention averaged over (5 seconds, 10 seconds, 60 seconds?)?
-kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26971

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
thanks for the pics of the setup - go chunky churner, go!

<edit> were the cranks and pedals really kept consistent between runs? I ask, simply because the pictures suggest otherwise.</edit>
-kraig

Last Edit: 5 years, 5 months ago by kraig.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26972

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
howardjd wrote:
Could this suggest a lift effect?


curvature...and in this case "dish" of the rear wheel can impact the symmetry of things, I reckon.

<edit>lift is a wind axis term...I think you are referring to a reported reduction in axial force because the sideforce (wind axis based) to drag ratio is favorable.</edit>

-k
-kraig

Last Edit: 5 years, 5 months ago by kraig.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26973

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
The cranks were held constant I forgot that 20 and 15 had to be redone for the chunky churner becuase the technician noticed the cranks were out of place.
Attachments:

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26974

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
The wheel is asymetrical due to being constructed from a spoked wheel, the crank side is more flat while the opposing side is more lenticular.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26975

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
howardjd wrote:
The wheel is asymetrical due to being constructed from a spoked wheel, the crank side is more flat while the opposing side is more lenticular.


yup, that was what I was getting at. in the facility you tested in, which side of the chunky churner (cassette side vs non-cassette side) is windward for a positive beta?

thanks for the data in the spreadsheet you sent offline - I didn't see the runs where the cranks were misaligned - did they provide these data with misaligned cranks for you?
-kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26976

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
Non cassette side windward for positive beta. The trials with with the crank out of place were removed.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26979

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
howardjd wrote:
Non cassette side windward for positive beta.


it's tough to put what I am seeing into proper context - there does appear to be asymmetry in things with both wheels, but that could be due to many things outside of rear wheel geometrical asymmetry.

I'd agree, though, that the churner has lower axial force than the wheel you tested against. As an aside, I tested wheel covers quite some time ago at a different facility (roll moment and sideforce were measured as well):

biketechreview.com/component/content/article/49-kdublog/490
-kraig

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26980

  • howardjd
  • OFFLINE
  • Senior Boarder
  • Posts: 41
  • Karma: 0
Yeah I really wish I would have brought a borrowed disk or took my trispoke in to test against so I would have a better idea on how my wheel stands. Once I have a source of income I'll probally be back to do that and test my other two creations.

Re: Box rim rear vrs any reputable disk, bike no rider 5 years, 5 months ago #26981

  • kraig
  • OFFLINE
  • Administrator
  • Posts: 3285
  • Karma: 4
howardjd wrote:
Yeah I really wish I would have brought a borrowed disk or took my trispoke in to test against so I would have a better idea on how my wheel stands.


Without additional information, odds are that it is likely aerodynamically similar to a wheelcover - it could be significantly worse than that on th road (based on your description), though - depending on the use-case.
-kraig

  • Page:
  • 1
Time to create page: 1.13 seconds

Poll

Which type of tire is more aerodynamic?