Should I enclose my rear wheel?

[sofadriver]

OK, I get it now.
I'll give it a try on my spare wheel.
Like Tauruck said - how will I know if I don't try it.

[tauruck]

I've been working on some wheel discs for 15" car wheels.

They will be Carbon fiber examples, light weight, no corrosion
and will look good.

Maybe you should do something similar using glass/epoxy?.

I know there is very little similarity between bicycle racing
and LSR but it says something when they use disc wheels
for better aero.
Prof. Joe Katz wrote in his book Race Car Aerodynamics" that covered wheels work best
but were not always the answer for auto racing due to brake temps.
He says wheels discs reduce drag by 16%.

From some of the posts above disc wheels work but you have to make
"one" change at a time. With a totally new bike how will you really know???.

[sofadriver]

I've been working on some wheel discs for 15" car wheels.

They will be Carbon fiber examples, light weight, no corrosion
and will look good.

Maybe you should do something similar using glass/epoxy?.

My buddy told me I should stop into the local bicycle shop. They do all that hi-end road racing bicycle stuff. Those guys are really into wheel discs. I'll check them out on Monday

[wobblywalrus]

It would be easy to test the aero on these things.  Put the bike on the center stand.  Run it in fifth gear and hold a peacock feather near the wheel.  Do it with and without the covers.  The setup that produces the least feather flutter is the best.

Keep in mind that the bottom of the wheel travels at 0 mph compared to the ambient air.  it is the friction drag that is manifested by turbulence around the spinning wheel that is a concern.   

[sofadriver]

 it is the friction drag that is manifested by turbulence around the spinning wheel that is a concern.  

Exactly.
Since my wheel is inside the tail there's not much aerodynamic drag on it (air coming past it) so reducing the drag generated by the (6) spokes could really conserve some power. Remember the old stationary exercise bikes that used air for resistance? I'll work on this.

Now I'm thinking about streamlining the front 6 spokes, too.

[kustombrad]

I'd set it up just like the "9mph" bike. Set everything on kill and go get the record. I would look for EVERY aero advantage I could get, unless you're just going out for fun! 

[sofadriver]

I'd set it up just like the "9mph" bike.

I think I agree (but I'm not real sure)

[sockjohn]

That first cover is two pieces riveted together so the inner circumference will fit inside the gap between the spokes and the spoke flange.  The Triumph is sorta weird in this way.  The spokes on the back wheel on that side are all "inside" style spokes.

The three spools stick through the spokes and they are located so the cover is positioned exactly right.  The spokes keep the spools fixed so the covers will not turn.

The wheel is balanced without the edges being taped to the rim.  There is enough room for me to squirrel the weights inside and to stick them to the rim where needed.  The edges are taped after the wheel is balanced.

Tech would be a problem if the tape held the covers on.  They are securely locked in place without the tape.  It is simply there to keep the salt out of the space inside the covers.

I do not know anything about water or laser cutting.  The covers are cut using tin snips and pounded flat on an anvil with a rubber hammer.  Do not use a metal hammer.  It will spread the aluminum out when hit and the dang covers will never fit. 

Lots of people plastidip wheels just for looks. I suppose that plastidip would hold up to the salt longer than the tape if it can hold up on daily drivers.

Just another way to skin the cat.

[Frank06]

wobbly: how thick (thin?) is the aluminum on those covers?  I like 'em!

thanks,
Frank

[bones]

Hey Sofa
  I had an aero guy from the local university come round and have a look.-- I could only get him once.

He said-- If the wheel was closely and totally enclosed it would be better with spokes.The disks will have more drag due to
the surface area
   Discs will work better in our case with the wheels being as open as they are.
  I'm going to put discs on the rear of the busa engined bike.

     cheers  Bones

[sofadriver]

Hey Sofa
  I had an aero guy from the local university come round and have a look.-- I could only get him once.

He said-- If the wheel was closely and totally enclosed it would be better with spokes.The disks will have more drag due to
the surface area
   Discs will work better in our case with the wheels being as open as they are.
  I'm going to put discs on the rear of the busa engined bike.

     cheers  Bones

I'll be interested to see your method.

[wobblywalrus]

There are a few topics on this forum about enclosing the rear wheel.  One asks me the gage of aluminum I used for the covers.  I cannot find the topic.  The answer will be here.  It is 0.020 inch aluminum from Ace Hardware.  This alloy is in the 2000 series, I think, and it is susceptible to salt corrosion in the form of pitting.  Right after I get home from the race I untape everything and wash the wheels, covers, etc with lots and lots of cold water.  No pits at this time.  There are aluminum alloys with more corrosion resistance.  One of my future project is to get 0.020 thick sheets in them for this work. 

[Scottie J]

There are a few topics on this forum about enclosing the rear wheel.  One asks me the gage of aluminum I used for the covers.  I cannot find the topic.  The answer will be here.  It is 0.020 inch aluminum from Ace Hardware.  This alloy is in the 2000 series, I think, and it is susceptible to salt corrosion in the form of pitting.  Right after I get home from the race I untape everything and wash the wheels, covers, etc with lots and lots of cold water.  No pits at this time.  There are aluminum alloys with more corrosion resistance.  One of my future project is to get 0.020 thick sheets in them for this work. 

How did you go about fabbing the discs themselves?  This is something I am interested in too, and there is an Ace Hardware 1 mile from my house. 

[wfojohn]

Wobbly wrote:
It would be easy to test the aero on these things.  Put the bike on the center stand.  Run it in fifth gear and hold a peacock feather near the wheel.  Do it with and without the covers.  The setup that produces the least feather flutter is the best.

Keep in mind that the bottom of the wheel travels at 0 mph compared to the ambient air.  it is the friction drag that is manifested by turbulence around the spinning wheel that is a concern. 

~~
Reading Wobblys' comments made me wonder if applying a scraper near the bottom rear of the fairing  (think automotive crank scraper method) would eliminate some turbulence and keep the salt build up less? Scraper angle and possibly a 3/8" of soft foam attached to the ground side of the scraper would keep salt build up off the scraper or to a minimum. Foam velcro'd to our motocross helmet and visor helps shed the mud buildup when riding/racing in wet conditions. Just a thought......

[wobblywalrus]

Posts 11, 12, and 13 show the covers being made.  The big circles were marked on the aluminum using a carpenter's trammel.  Google "General No.520 Precision Trammels."  These are a good tool for any fabricator.  They clamp onto a 3/8 x 3/4 bar so use of a long bar will allow a big circle to be scratched out on the metal.  The outer edge of the cover is just large enough to overlap the wheel rim so the tape will attach to both the cover and the rim.

In my case, the covers were made along with a spat in front of the rear wheel and some changes to the front of the fairing and the tail skirting was also cleaned up, aerodynamically.  It is hard to say if the wheel covers did anything for aero.  Too much other stuff was done, too.

My guess is if the wheel has aerodynamically inefficient spokes, like some one piece wheels, it might make a significant difference.

That scraper idea, or a brush alongside the wheel, might work, too.