Coast Down testing with Larry Oz!

[LarryOz]

I did some coast-down aero testing over the weekend. 5 bikes: RAAM V20 w/reg handle bars, my Frankestein bike (Thom's rear frame, V20 front drive, Kent's railgun seat, and my stubby bars), Thom's complete ES (elegant solution - MBB), Arrowhead, and my Red V20. The test suite: I coasted down the little ramp you see on the back of my trailer that I place at the end of the road, then about 50 feet down the road I put a piece of tape. This is where I started each lap when crossing over. The course was a quick 4-5% downhill, followed by a shorten uphill, then another 3% or so downhill. I stopped the lap when passing another piece of tape on the road. Total length: about 0.20 miles. Max speed close to 30mph. I ran between 10-12 runs for each bike. Same wheels and tires on everything except the Arrowhead since they would not fit. Nice because no cars going up and down, way in the trees so hardly ever any wind, and a nice hill to coast and turn around after. The Frankenstein won out, but they are so close it is hard to tell by how much. Interesting because it conflicts slightly with my speed and wattage testing on my local track. I guess I need to start building my windtunnel now.

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[Gary123]

If u come to CMS wed. Which bike

 

[RojoRacing]

Coast down doesn't take into effect the extra drive train drag of the arrowhead ether. Also is it ever dry in your area?

 

[LarryOz]

Coast down doesn't take into effect the extra drive train drag of the arrowhead ether. Also is it ever dry in your area?

True - It is virtually impossible to testing all aspects in one test. Same issue with a windtunnel. There are also more subtle differences like delta between feet and hips, and how easy or hard it is make power in different positions. The combinations are almost unlimited really.
Dry here - not this years. I feel like I live in a rain forest lately. About the wettest summer on records. Lately it has been raining 2 or 3 times a day. It is crazy.

 

[LarryOz]

If u come to CMS wed. Which bike

I think I will re-build Frankenstein and also being the Arrowhead and see how I feel when warming up with them on the race-track. During my sprints back up the hill during my coast down tests, I noticed that it seemed like I could make substantially more power on the Arrowhead. I also rode it on the Northbrook velodrome at 30+mph for 20K, so chances are I can do the same close to the same thing at CMS, maybe even faster. 31.84mph is the all time fastest time on the track. Wow - I doubt I can go that fast in the condition that I am in, but I'll give it all I got and see where I land.

 

[Apollo]

During my sprints back up the hill during my coast down tests, I noticed that it seemed like I could make substantially more power on the Arrowhead.

The Arrowhead is the only carbon bike in the test. Carbon is known for being an efficient material for power transmission, despite the less efficient RWD drivetrain. It could also be the position is just better suited to your particular physiology.

BTW, if the Arrowhead was tested with the HED wheel in the photo (28 spokes is significant drag), it would be at a competitive disadvantage to the other bikes sporting dual disc wheels. How'd you think it would fare if it had a disc up front?

 

[LarryOz]

BTW, if the Arrowhead was tested with the HED wheel in the photo (28 spokes is significant drag), it would be at a competitive disadvantage to the other bikes sporting dual disc wheels. How'd you think it would fare if it had a disc up front?

Rear: tri-spoke in my testing was pretty equal to full covered disc. Front: They are aero spokes and about 80mm disc fairing. To be totally fair, when I have the time I will try and fit my Boyd (with full cover) on the back (means swapping out the brake which is no small feat!), and using a front with full disc cover, and then run the test again - with one set of wheels, and the the other. I am trying to get my hands on a 650 latex tube and need than to make the tube/tire combo equivalent. The current 650 front is at least tubular which has better rolling resistance.

 

[ed72]

Pretty sure 650 latex tubes do not exist on the market. You could cut and glue a 700c as some do.

 

[tiltmaniac]

Clearly you have to get a whee outfitted with these: http://road.cc/content/news/149414-introducing-spoke-fins-swivelling-fairings-your-spokes

 

[Gary123]

More testing Larry.

 

[ratz]

BTW, if the Arrowhead was tested with the HED wheel in the photo (28 spokes is significant drag), it would be at a competitive disadvantage to the other bikes sporting dual disc wheels. How'd you think it would fare if it had a disc up front?

There's actually a lot of test results floating out there that suggest 90's are faster than discs in most out door conditions. Once there is a cross with the solid disc advantage evoporates; Been trying to get Larry some 90's but all I have to loan him are ones that need tubes.

Next up add in Tubes. Testing here seem to show the Corsa and the fusion out performing the Pro One. Good thing I'm slow and it doesn't matter to me too much to test.

 

[Apollo]

Rear: tri-spoke in my testing was pretty equal to full covered disc. Front: They are aero spokes and about 80mm disc fairing. To be totally fair, when I have the time I will try and fit my Boyd (with full cover) on the back (means swapping out the brake which is no small feat!), and using a front with full disc cover, and then run the test again - with one set of wheels, and the the other. I am trying to get my hands on a 650 latex tube and need than to make the tube/tire combo equivalent. The current 650 front is at least tubular which has better rolling resistance.

Hi Larry,

I wouldn't worry too much in trying to find a 650C tubular with latex tube. Tubulars are different enough that riding one with a butyl tube in and of itself won't make a huge difference in rolling resistance. I have 30 years saddle time worth of tubular experience. The difference is primarily in the weight, which is nominal at best unless you're a gram counter. Clinchers are an entirely different matter that opting for a latex tube has more merit. I won't discuss the clincher/tubular debate any further because it's extremely contentious over here, but will conclude by saying that a Continental Sprinter in 650Cx22 size (actual inflated width is greater) is more than sufficient for your tests and available at a reasonable price.

Do you already have a front spoke cover for the 650C wheel or will you be making one? If I had that front 650C HED, I'd relace it by removing every second spoke and convert it to a 14-spoke wheel. 16-spoke 700C wheels have been a standard of sorts for about a decade (Zipp) and a 14-spoke 650C wheel should be just as strong, probably stronger.

 

[LarryOz]

I wouldn't worry too much in trying to find a 650C tubular with latex tube

I was just trying to find a latex tube for them GP4000 tire to mount on another wheel that has a full disc cover. From what I understand most tubulars have latex tubes away. As Bob pointed out, 90 are almost better than full disc cover, except in a total no-wind situation (when does that ever happen?)

 

[LarryOz]

More testing Larry.

I need to stop testing and start racing!

 

[Gary123]

I think your testing helps your racing an vice a versa

 

[Charles.Plager]

The Virtual Elevation (with a power meter) can do a good job of estimating aerodynamic drag and taking power train losses into account (although you won't be able to disentangle power train and rolling resistance).

Roll downs do tell you a lot about aerodynamic drag (and even rolling resistance if you know the elevation profile and have the full track saved).

My biggest suggestion for roll downs is to do multiple runs (while pedaling backwards).

 

[LarryOz]

My biggest suggestion for roll downs is to do multiple runs (while pedaling backwards).

Agree - but won't that make me go backwards back up my hill!

 

[Apollo]

As Bob pointed out, 90 are almost better than full disc cover, except in a total no-wind situation (when does that ever happen?)

I totally agree and wouldn't recommend anyone trying to ride with a disc wheel up front on the road. The other bikes in the test had them and this was only a suggestion to even out the test field. No biggie.

 

[LarryOz]

OK - Testing phase #2.
I took a couple of suggestions from the peanut gallery (I mean that in a nice way!)
I threw in a test with an upright "DF" bike with aero drops out front. Tested with hands on outside drops, then on aero drops.
I also re-tested the Arrowhead with the Tri-spoke wheel in the back and the 24-spoke bladed front (for control set), and then I put same drive full disc covered wheel in back, and installed a full front disc in the front. Results were that Arrowhead was quite a bit faster with the full disc wheel upgrades. As in nearly 20 feet in only 0.20 mile coast down at an average speed of about 21.50mph. That figures out to 100 feet per mile, or 1.89 miles for a Century. Might be bad math, but in my book that calculates to about a 2% gain in speed. To get a 2% gain in speed just by riding harder, that would equate to 8% more power. So if you are talking about something in the range of 200 watts to go a certain speed, it would only take 182 watts to go the same speed by switching out these wheels.

 

[LarryOz]

An aside: This was this first time I have ridden an upright bike in probably 2 years. I am so amazed how how easy it was to make watts in the upright position. Al I had to do was breath and I pushed 200 watts. 3oo felt as easy as making 200 on recumbent. And climbing was so crazy easy and fast. I hit 500-600 watts just pedaling up the grade without even trying to kill it. Next goal: figure out how to make this power on the Cruzbike!