Motorized Bicycle, hoping for mid-50mph, fairing question.

[augidog]

Try as I might, I can't find any data beyond sales hype which may or not be true.

Our bike, and rider position, is pretty clunky. Unfortunately, we can't do anything about it, we are working with what we have...which is an upright road bicycle, and a middle-age overweight rider in full leathers.

Given the parameters, we're looking at fairings. We have two options on hand, and would appreciate feedback. Please refrain from speeches about what we "should do"...we know our entry isn't optimal...we just want to be as fast as we can be, but be safe.

Our first option is a lexan bubble, made for bicycles. It's 27" wide, 17" high, but only about 6" deep. In a perfect straight-ahead world it could be helpful, but I'm worried about how a cross gust (head or tail) could affect steering stability.

Option two is a small scooter "headlight fairing." 13" wide, 12" high, 12" deep. It actually has a good shape, but there isn't a lot of coverage. My experience with this fairing has been good. I can lean down just enough to put the chin of my helmet right above the windshield.

The question is will the small fairing, at speed, help (at least minimally) with a slip around our riders body, or is it just sitting there doing nothing? The other question is, how safe or unsafe would the large lexan bubble be on the salt?

Thanks in advance for any experienced input.

[tortoise]

You might consider a seat/tailpiece. Close the hole in the air smoothly.  Could be a problem with your engine placement, though.

[augidog]

You might consider a seat/tailpiece. Close the hole in the air smoothly.  Could be a problem with your engine placement, though.

I agree on both counts, the most significant being we don't have a good way to mount rear effects.

Do you have any thoughts about the fairings we have to choose from? Don't worry, you can't hurt my feelings if you're just being honest and share what you know.

[Rex Schimmer]

You might consider covering the upper half of the front wheel, as that is the part that is making the most drag and you could even consider going with one of the older style racing 3 or 4 spoke carbon fiber racing wheels, they are pretty much out of style now but pretty aero. If you need one my son, Duke, has one in his stash of bike racing stuff. Also consider adding a tail fairing to the riders helmet (don't know if this is legal) and also a back hump in your riding leathers, also go to some sort of aero shape for the front forks.  Check into some of the tech info on road racing bikes as they larger teams spend lots of time in wind tunnels looking for small aero improvements. Almost any fairing of the front of the bike to get the air to flow over and around your rider should be helpful. If your only power is the rider than going to ceramic bearings in the wheels and the crank gear could be worth the cost.

Rex

[augidog]

You might consider covering the upper half of the front wheel, as that is the part that is making the most drag and you could even consider going with one of the older style racing 3 or 4 spoke carbon fiber racing wheels, they are pretty much out of style now but pretty aero. If you need one my son, Duke, has one in his stash of bike racing stuff. Also consider adding a tail fairing to the riders helmet (don't know if this is legal) and also a back hump in your riding leathers, also go to some sort of aero shape for the front forks.  Check into some of the tech info on road racing bikes as they larger teams spend lots of time in wind tunnels looking for small aero improvements. Almost any fairing of the front of the bike to get the air to flow over and around your rider should be helpful. If your only power is the rider than going to ceramic bearings in the wheels and the crank gear could be worth the cost.

Rex

the only one of those (valid) points I can address/change is the front wheel cover. I will work on that, using a backwards fender.

There is a 47cc engine and belt-drive mounted above the rear wheel.

I am seeking specific feedback about the two fairings in the picture. I'm concerned the large one is too broad and flat, and could be unsafe. I'm dubious about the small ones effectiveness.

[MAYOMAN]

You need to go back to the basics. The most important factor in minimizing aero drag is rider position. Using the time trial bars like tri-athletes will optimize the drag with arms extended forward (like a downhill skier) and back flat. Next most important is the wheels. Solid disk wheels or deep section carbon tri-spokes are quite low drag over any spoked wheels. Finally, the frame built up of aero cross-section tube rather than round tubes completes the ideal bike. The motor then will be tucked in behind the riders butt out of the air stream. The attached pursuit bike of mine is an example. A fit rider can easily reach 40 mph on this machine. Forget the fairing - won't really help much.

[augidog]

You know...I'm just gonna come out and say it.

Yes, it's a forum, and yes, opinions are bountiful. Everything everyone is saying would be perfect advice, if the question was how to start at the beginning of a motorized bicycle project.

BUT...just suppose for a second that we WANT to run THIS bike, which we like a lot, because we want to see how fast we can make THIS bike go on the salt, with the parts we have on hand, or can make with our tiny budget...we've paid the same price for the 1-mile track as everyone else, and like everyone else our main goal is to have as much safe fun as possible.

So, do you think one of THOSE fairings, on THAT bike, with a big rider wearing full motorcycle safety gear, will make a difference or not? Thanks in advance for any direct answers.

[SPDRACR]

have You looked at Recumbent bicycle fairings ? The are very long and about rider wide ?
Just thinking.

[augidog]

have You looked at Recumbent bicycle fairings ? The are very long and about rider wide ?
Just thinking.

yes, we have, they're pricey...the one we already have is like a sideways version. I have considered trimming it to use vertically, but it's still pretty "flat" IE it doesn't have much wrap around the edges.

[Elmo Rodge]

Mayoman did answer your question in his final sentence. He just offered up some other suggestions.
Wayno

[Eddieschopshop]

Personal opinion without facts. Unless you can really have yourself up close to that fairing it will do more harm than good.  Glad I am on the long track.

[Interested Observer]

Vortex shedding off the sharp edges of the bubble might produce more drag than just letting the air flow over the (somewhat streamlined) rider. 
Not sure where the scooter unit would be mounted but it might be better than just having the steering head and other tubulars exposed to the wind.  However, the two “ears” on the bottom corners look like drag producers.
Shrouding the front of the front wheel may be a good drag reducer, but also liable for trouble in a crosswind.

[augidog]

Thank you, folks...and that means you too Mayoman. I did take note of your opinion on my fairings. Thanks, Elmo, I deserved that.

OK, so no fairing, and just an old guy with a leatherclad paunch. At the least, I know he'll be smiling, so long as the bike gives him 6 hassle-free runs.

"Glad I am on the long track." Hey now, we'll only be a couple minutes, and I don't expect we'll be leaving any bits and pieces laying about. I did just fine in 2008, and nobody seemed to mind having us around.
  

[ggl205]

Augidog, IO came very close to something you can do to your bike that should make a measurable difference. There are an enormous amount of wind tunnel tests conducted over the years that universally show marked aero improvement by using an aero front wheel. That HED three spoke Mayoman displayed on his pursuit bike is  not that expensive when purchased used and would help a great deal. If you don't want to buy a new wheel, you can get big moon discks for your current wheel. Only downside is what IO said and that it will be harder to go straight in a cross wind. But of all the singular aero improvements a bicycle benefits from, an aero front wheel is the best.

John

[augidog]

Augidog, IO came very close to something you can do to your bike that should make a measurable difference. There are an enormous amount of wind tunnel tests conducted over the years that universally show marked aero improvement by using an aero front wheel. That HED three spoke Mayoman displayed on his pursuit bike is  not that expensive when purchased used and would help a great deal. If you don't want to buy a new wheel, you can get big moon discks for your current wheel. Only downside is what IO said and that it will be harder to go straight in a cross wind. But of all the singular aero improvements a bicycle benefits from, an aero front wheel is the best.

John

I picked up on that, plus I've seen some demos. I'm going to start with a backwards fender, and try shielding the wheel about halfway to the axle.