Amateur Aerodynamics for Silvio

[Andrew 1973]

Inspired by Jim Gerwing's thread about his Vendetta and my idle hands, I decided to try my hand at making a disc wheel cover for the Silvio. Made of poster board and duct tape and secured to the rim with vinyl electrical tape, it's a cheap five-dollar experiment. I haven't ridden with it yet, but I plan to take a run this evening.

alt="The original Duck Disk"

I ran short of black tape and had to finish with yellow. The vinyl lettering came from the art supplies drawer and I didn't have enough letters to use one size of type. Finally, the NGK sticker serves to cover the valve stem access port.

The yellow duck tape manufactured by 3M is lighter than the black Duck brand tape. The lighter tape makes for a disc cover that better conforms to the wheel dish. The other side has a cover made with two layers of Duck brand tape and is not as easy to work with.
alt="Duck Disk Detail"

Each disc cover is made with a layer of poster board sandwiched between two layers of duct tape for durability and hopefully water-resistance. If it doesn't last, it was, after all, a five dollar project at best.

 

[Jeremy S]

Andrew, I guess this means

Andrew, I guess this means you sorted out your cracked weld on the boom?

The cover looks great! Very professional.

 

[Andrew 1973]

Yes, Jeremy

I got the boom repaired, but had offers of support from the good people of Cruzbike. You can't beat the customer service of a small company where the people backing the bikes are just as passionate as us as cyclists too.

Thanks for the compliments. Let's see if it works and can help me shave off a few seconds here and there. I am planning to ride a flat, fast century next month and want to set a personal best.

 

[Bruce B]

Nice Job On The Wheel

Andrew,

Supporting that disc covered wheel are polished seat stays. I have not seen that before!

 

[Andrew 1973]

thanks, bruce

Ah, I was trying to keep the polished bits my secret until I was done. That came out of having to strip the boom for a repair and thus stripping the paint. I played with the idea of polishing the aluminum rather than repainting. PAINTING would have been easier! The Silvio had a filler applied to the welds to smooth them and it is a bear to remove. It's not like Bondo, but more similar to JB Weld or Lab Metal. There isn't much filler applied and the welds are really beautifully executed, but the hardness of the filler and the way rhat it gets into the tiny recesses of the welds makes mechanical removal almost impossible. Chemical removers barely affect it either.

In hindsight, I just would have repainted the boom and left everything else alone.

 

[Charles.Plager]

Ok. Now you've got to post

Ok. Now you've got to post pictures of the entire bike...

 

[Andrew 1973]

first i need to clean her up

Hey Charles,

One just can't post a pic on here; remember that Ivan set the bar for Silvio photos.

 

[Ivan]

C'mon Andrew! ?Thats a good

C'mon Andrew! ?Thats a good looking wheel...no it looks incredible for only $5! How did she fare on her run?

 

[Jim Gerwing]

I tip my hat to you

And show us a picture of the dark side.

 

[Andrew 1973]

Results so far

There is a short, not steep hill near my house that I used for a roll-down test. With a mild headwind, I was able to hit a maximum speed of 38.67mph. I really figured that I would have topped 40mph, so the first test was a disappointment. I am working on a plastic version now for the front wheel, but it won't likely be ready in time for me to test it today. I do attend the local shop's ride tonight and have had no issues keeping up with the B group. This might be a good time to see if there is a perciptible gain from the Duck Disk™. I am hoping to run a sub-five hour century next month and finding an aero advantage would help. Maybe afterwards, I can justify getting a Vendetta or the next generation Silvio.

 

[Charles.Plager]

What kind of roll down speed

What kind of roll down speed do you get without the disk?

 

[Andrew 1973]

I am sure I 38mph without the disk

I may be wrong, but I am sure I hit 38mph without the disk cover.

 

[Andrew 1973]

Front Disk

I used some plastic sign blanks that I purchased from Lowes to make a front disk cover. This method was much faster to produce. The sign blanks were $2.08 apiece and I required four sheets to make two disk covers. The pieces were cemented together with an all-purpose plastic cement used for plumbing purposes. The cement cured within minutes and the disk covers are held to the rim with vinyl tape.

Tonight during the group ride, I was able to coast down my "test hill" at a maximum speed of 42.34mph. This makes the front disk cover seem promising in gaining an aerodynamic advantage. Steering was only mildly and occasionally effected with a slight buffeting that was not at all disconcerting.

 

[Jeremy S]

Once again, very slick

Once again, very slick looking (and apparently slick riding too).

 

[Andrew 1973]

Thanks Jeremy

I had to do something with all of you riding around on your 2.0 Silvios. It's not a perfect solution, but so far I am having fun with it.

 

[Charles.Plager]

For what it's worth:
Andrew,

For what it's worth:

Andrew, you should do repeated runs down the hills with different conditions. Can you borrow uncovered wheels so you can play mix-n-match? I'm now getting curious here!

 

[Andrew 1973]

you're correct, charles

I have a wider set of wheels on my Cannondale Quick, but the 32 ? 700 tires are as much of an issue as is the 9 speed Shimano cassette since I am running 10 speed Campagnolo.

Probably the only way for me to test it is to do three consecutive runs with the disk covers on, and then remove them an do another three and take the averages from each set of runs. If nothing else, I will have one heck of a hill repeat workout.

Does anyone know how I can determine the elevation of my test route without having a Garmin or fancy software on a fancy smart phone?

 

[Charles.Plager]

RideWithGps.com should

RideWithGps.com should work.

I didn't suggest taking on/off your covers because I didn't know how much work it would be. That would be the best "only the covers has changed" test.

 

[Ted]

Crosswind effect?

Anyone have an idea as to how much a crosswind would affect the handling? I'm doing 500 mile RAAM qualifier next month and would love to try these covers. However, if there is a stiff crosswind ...

 

[Charles.Plager]

Anyone have an idea as to how

Anyone have an idea as to how much a crosswind would affect the handling? I'm doing 500 mile RAAM qualifier next month and would love to try these covers. However, if there is a stiff crosswind ...

One advantage that MBB bikes have over RWD bikes is that we also use our legs to help control the steering. I would think (but have NO experience here) that this would help somewhat (to even quite a bit).