Landracing Forum
Tech Information => Aerodynamics => Topic started by: augidog on July 20, 2018, 11:26:34 AM
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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.
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You might consider a seat/tailpiece. Close the hole in the air smoothly. Could be a problem with your engine placement, though.
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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.
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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
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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.
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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.
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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.
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have You looked at Recumbent bicycle fairings ? The are very long and about rider wide ?
Just thinking.
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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.
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Mayoman did answer your question in his final sentence. He just offered up some other suggestions.
Wayno
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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.
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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.
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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.
:cheers:
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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
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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.
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I still think you need to go back to first principles.
POSITION of the rider.
Fashioning handlebars that will allow the rider to lay flat, back horizontal, feet on the pegs, hands close together (like a praying position) will give you more aero benefit than a fairing.
Why would you streamline a barn door?
The front wheel would be an additional opportunity - but secondary to position. KISS - Keep It Simple Stupid - should be the goal along with low drag.
Rollin Free (?) had it figured out long ago - but that was really extreme.
Good luck on your venture.
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:dhorse: :dhorse: :dhorse:
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The "Pantani" position is how we used to decend long hills. Of course, I was 19 back then and could actually assume and hold that position. Still have the chamois with a hole in the rear from getting a little to close the the rear tire.
John
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I still think you need to go back to first principles.
POSITION of the rider.
Fashioning handlebars that will allow the rider to lay flat, back horizontal, feet on the pegs, hands close together (like a praying position) will give you more aero benefit than a fairing.
Why would you streamline a barn door?
The front wheel would be an additional opportunity - but secondary to position. KISS - Keep It Simple Stupid - should be the goal along with low drag.
Rollin Free (?) had it figured out long ago - but that was really extreme.
Good luck on your venture.
Thanks for your encouragement, MAYO', and please believe I am not disagreeing with you.
This particular project started with an existing bike, an existing engine, and an existing rider. It was my job to cobble them all together into a safe entry that would pass tech. Trust me, we KNOW we're far from optimal for LSR. The best-but-joking advice I got was in an email "make your rider smaller" but alas we can not. This adventure is all about my good friend hearing those magical words "the course is yours."
In his full leathers, and Snell helmet, and considering he has to keep his feet on the pedals, Jimmy can lean forward only a bit, nothing like a regular bicycle tuck, and the adjustments accommodate that. If you're having a hard time picturing our limitations, put your full USFRA motorcycle gear on, and then try to handle your pursuit bicycle.
All of this is exactly why I asked the question... considering how inefficient our bike and rider position is, would a fairing help? Now I know the answer is no, and I'm good with that. Jimmy will still have fun, and I still get to try to tune for top speed. Nobody loses with this endeavor.
If ever I find myself in a position to build a 50cc LSR bicycle from scratch, well, everything you say would apply, plus I'd start with a skinny little rider who practices yoga. I don't know, but maybe that's you? ;)
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Mayoma, AKA, Dick Keller (think Blue Flame rocket car) is the right size for a small liner but don't call him skinny unless you are ready to fight (lol).
I get it, augidog, you guys are just trying to have a little fun and add a bit more history to an already storied bicycle. But when you ask aero questions of this group, you will get responses from vastly experienced and successful racers. They know only one thing and that is how to go fast and make fast vehicles go faster. You will always get way more good information here than you can ever use. Take from it what you want and thank everyone for what is left. This is a great group of people and they are always willing to help.
John
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I'd suggest using a flatter stem to lower the bars. Only when you get over about 15 mph will the drag effects start to kick in. You are really limiting the amount of power you can put into the pedals sitting with your butt back and your legs and arms all forward. If no changes are made I would start the run out of the saddle to get more efficient power transfer to the pedals. And add some mini toe clips without straps to help keep your feet on the pedals without trapping them. Once you get up to speed to use the motor you sit down and tuck.
Some interesting stuff on tuck positions in the vid. Maybe you can apply some of this even though you would be in leathers.
https://www.youtube.com/watch?v=VYAjF4Niz6E
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Mayoma, AKA, Dick Keller (think Blue Flame rocket car) is the right size for a small liner but don't call him skinny unless you are ready to fight (lol).
I get it, augidog, you guys are just trying to have a little fun and add a bit more history to an already storied bicycle. But when you ask aero questions of this group, you will get responses from vastly experienced and successful racers. They know only one thing and that is how to go fast and make fast vehicles go faster. You will always get way more good information here than you can ever use. Take from it what you want and thank everyone for what is left. This is a great group of people and they are always willing to help.
John
considering the shape I'm in, Mr. Keller, I meant skinny as a compliment. I do appreciate the experienced input, and my apologies to the group if it appeared otherwise. I had a question, I needed an answer, and I don't react well to "you should" especially when I can't...when I was on the road, I'd hit local taverns, eventually someone would say "you should"...
I'd put my arm around my new beer buddy and say "you should build one however you like" :cheers:
(after a lifetime as a mechanic and then computer tech, and 25 years on the internet, I've learned to say "what I would do" instead of "you should"... it's subtle, but makes a big difference)
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I'd suggest using a flatter stem to lower the bars. Only when you get over about 15 mph will the drag effects start to kick in. You are really limiting the amount of power you can put into the pedals sitting with your butt back and your legs and arms all forward. If no changes are made I would start the run out of the saddle to get more efficient power transfer to the pedals. And add some mini toe clips without straps to help keep your feet on the pedals without trapping them. Once you get up to speed to use the motor you sit down and tuck.
Some interesting stuff on tuck positions in the vid. Maybe you can apply some of this even though you would be in leathers.
thanks for that. I've attached a pic of my fasted position during testing in 2008, apehanger bars pointed forward, but doggone it was pretty hard to get down there, hold position, and then get back up. I couldn't breath all folded up like that, and handling was horrible. The next one shows fastest position ever with my 32cc at sea level, 38mph, but no way I could do that with the leathers and Snell helmet.
In the "World of Speed" forum I break down the mechanics of the bike this year...human/electric/gas in progression until it's engine-only. Pedaling is not much of a chore really, but in keeping with the spirit of "Motorized Bicycle" the pedals work and we'll use them at least minimally.
By the way, we learned a hard lesson that year about building at sea level, and then trying to tune for the salt lake. We bought some VP Racing "C50" for the 47R, and hope it will help at elevation.
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Since once you get to speed is engine only, can you put little pegs on the back axle and move your feet back off the pedals? Can't go to full "Rollie Free" but maybe that would help streamline a bit.
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Since once you get to speed is engine only, can you put little pegs on the back axle and move your feet back off the pedals? Can't go to full "Rollie Free" but maybe that would help streamline a bit.
that is an option everyone wanted to vote "yes" on, until Pete (our electric-drive guru) mentioned that the freewheeling pedals will likely want to spin in the wind. It could be risky trying to get your feet back on them, perhaps catastrophic if you miss and a boot hits the ground. I need to get Jimmy back to his girlfriend in one piece, or she won't let him come out and play anymore.
This discussion has really fired me up to WANT to build a LSR-purposed Motorized Bicycle...something I could ride myself, even with my poor health. I don't know if I'll ever get to, but if I do it would be way different than this one, which is my everyday road bike.
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I know consensus is that the little fairing is useless, but one person mentioned it may help mask the center clutter. I taped the lens and installed it temporarily. By leaning forward and tucking his elbows, Jimmy can put the chin of his helmet a few inches above and behind the top of it. I'll Dremel off those bottom "ears" if I have to, but before I do I would greatly appreciate feedback on this option as pictured.
I know we're not near what you folks are used to dealing with, but we really do want to "represent" as well as we can with our entry. To us, that means not falling down, not falling apart, and not using any more track time than our slower speed requires.
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? some sort of "pedal lock" to prevent free wheeling? but I understand that issue which crossed my mind but was unstated.
In the absence of wind tunnel, coast down testing can be used. Do you have a nearby hill? Standing start at the top, drift to the bottom. Check time or speed or something at the bottom. Change configuration. Repeat. I don't know. Worth a try.
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? some sort of "pedal lock" to prevent free wheeling? but I understand that issue which crossed my mind but was unstated.
In the absence of wind tunnel, coast down testing can be used. Do you have a nearby hill? Standing start at the top, drift to the bottom. Check time or speed or something at the bottom. Change configuration. Repeat. I don't know. Worth a try.
we're using a Bafang BBS02 mid-drive, it incorporates the bottom-bracket, chainring, and cranks, into one assembly, and drives a 6-speed cassette on the rear wheel. Both the rear wheel and the pedal cranks freewheel independently, devising an autolock that doesn't mess with something else, we can't think of anything.
I'm in Oregon, we have hills everywhere, but we also have a secluded level mile nearby. Road testing of the drivetrain begins soon, and if we can get away with enough runs I'll certainly be able to make some comparisons.
As I read this before submitting, I wondered if a couple zip-tie "tails" could stop and hold the cranks yet not hinder pedaling. Only on one side so the position is predictable. Dang, jacksoni, you might have prompted a solution, thanks!
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Jack/augidog:
Coast down results can be achieved as easily as coasting down a hill to a dead stop, mark the position, make a change, then repeat. If you coast farther with a change, that is an improvement. Uncontrolled, variables will be wind fluctuations, road variances (try to use the same path), possible differences on how you start and traffic going the opposite direction. Still, coast down can tell you a lot. Do several runs of each configuration and average distances from a fixed position.
Augidog, pay attention to wheel bearing condition and setup. Run them a little loose, maybe with just a tiny bit of play and use very thin synthetic oil instead of grease.
John
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Jacksoni/augidog:
Coast down results can be achieved as easily as coasting down a hill to a dead stop, mark the position, make a change, then repeat. If you coast farther with a change, that is an improvement. Uncontrolled, variables will be wind fluctuations, road variances (try to use the same path), possible differences on how you start and traffic going the opposite direction. Still, coast down can tell you a lot.
Augidog, pay attention to wheel bearing condition and setup. Run them a little loose, maybe with just a tiny bit of play and use very thin synthetic oil instead of grease.
John
distance traveled, that's an excellent testing method, I like it.
Our hubs are Sturmey-Archer drums, with high-end shielded bearings, treated with a dab of Kable-Ease graphite. They roll forever. The wheels are built using NOS "Hap Jones" 10G motorcycle spokes, by Jim "The Wheelmaster" Burkman in Auburn WA. Anyone using spoked wheels, on anything, you can't go wrong with Jim and his father Morrie. Yes, that's a plug for a sponsor and a good friend.
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better check the rulebook on taking your feet off the pedals....
Motorcycles are required to have only ONE set of pegs/pedals and your feet have to remain on them during the run......safety issue
Good luck with all this,,,,,, all motorcycles evolved from motorized bikes,,,
Smitty
Red Baron Race Team
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better check the rulebook on taking your feet off the pedals....
Motorcycles are required to have only ONE set of pegs/pedals and your feet have to remain on them during the run......safety issue
Good luck with all this,,,,,, all motorcycles evolved from motorized bikes,,,
Smitty
Red Baron Race Team
Well, that settles that. Personally, I'm relieved we can't do it. Thank you, Smitty, and an extra thanks for your historical observation.
Our Honorary Sponsor is The George A. Wyman Memorial Project, and we are running to raise awareness for this great cause.
http://motor-assisted-bicycling.1062526.n5.nabble.com/George-A-Wyman-1st-Across-America-f5710342.html
Our rider, Jimmy, models the latest in Wyman bling...the dartboard's regulation size & height, so you can tell he's not exactly aerodynamically correct for this mission.
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The bicycle is running 130 course at WoS. Therefore there is no class rules and no recognized record as we know it.
Motorcycle rules do NOT apply.
DW
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The bicycle is running 130 course at WoS. Therefore there is no class rules and no recognized record as we know it.
Motorcycle rules do NOT apply.
DW
Actually, DW, they sort of do...the safety-related ones, at least. Our rider has to have approved motorcycle gear, the bike has to have positive cutout for electric motor and gas engine. I even offered to install a lanyard, but was told we could do without. We have to pass tech for common sense construction, etc...so, I am totally ok with "feet stay on pedals" as fair enough to be able to participate.
When I was working things out with Dan Wright, before approval in 2008, he said "The salt hurts no matter what you fall off of."