Aerofairing and fuel consumption on an Enfield clone

[Sibbo]

I've been reading with considerable interest the fuel consumption figure people are achieving from the Yamclones , they are truly remarkable ! I'm still on the look out for an Enfield to build on .

It seems to me the only way of improving on consumption figures and speed is a fairing .

I recently bought an old copy of ''The Classic Motorcycle '' ,July 1992 with a story about the original Royal Enfield factory fairing , the Dreamliner . Most people will find the 50s styling a bit hard to take but the overall idea is very interesting . It was mounted on a 350cc petrol Bullet ,which IIRC put out 13 hp .Not really comparable with a 9 hp diesel but closer than most comparisons .

Here is a table from the article .



and a photo of the fairing .



It would be a lot of work to build but it might add 15 km/hr to the top speed and reduce fuel by 25% .

BTW .I'm not sure if this is the right place for this post but as it relates to fuel economy , perhaps ?

[Sibbo]

The type of fairing this gentleman has built would be the optimum but on a normal upright bike , especially one with tank and standard frame it might be difficult to arrange ,particularly the getting on and off part.
http://www.velomobiel.nl/allert/Recumbe ... orbike.htm

Here's a rough sketch of a fairing of his type expanded to fit around an Bullet .It's big and cross winds might be fun .

[Stuart]

In my experience owners of the smaller diesel bikes suffer less from wind resistance and more from straight lack of power. Tackle those long, drawn out hills and you end up falling back and back and back. I like the idea of the fairing and it would surely help on the straight but the added weight (along with touring luggage?) would cripple the ride.
Far better to work on getting more from the engine. I used a small device in the fuel with put the Cetaine rating up (tin pellets in a steel cage - http://www.broquet.co.uk/). Worked well as it just bubbled away in the fuel cos I didn't always do too many miles on it at some times of the year. Also turned the fueling screw up a touch

[Sibbo]

Yes ,a few more hp would be the ideal but using the ones available as profitably as possible seems good too .I take your point about weigh but modern composites are far lighter than the 50s versions .Wind resistance is felt most on a machine without much power , if it had the power to muscle through , there would be no problem .

On this site .http://www.velomobiel.nl/allert/Recumbe ... orbike.htm,the builder makes it pretty obvious that wind resistance is the BIG one .....although I agree about hills ! But for me 90% of my riding is on flatish roads .

He has got 80 mph out of a 125cc Honda step through ! and 200 mpg at 50 mph .

[Stuart]

Don't forget we have limited revs! 3800rpm = 68mph - if you can pull that. Realistically I could achieve 55mph on a 350 diesel Bullet most of the time. The hills got me don't to 40mph if that.
But yes, a lightweight fairing would be good. As long as it was super lightweight

[Crazymanneil]

my 2p

http://www.youtube.com/watch?v=VbdkZB9-Sd4

N

[Sibbo]

my 2p

http://www.youtube.com/watch?v=VbdkZB9-Sd4

N

Yep ,the Rolls Royce version of the Allert ! Very nice indeed ,an excellent job of fairing .

[Sibbo]

Don't forget we have limited revs! 3800rpm = 68mph - if you can pull that. Realistically I could achieve 55mph on a 350 diesel Bullet most of the time. The hills got me don't to 40mph if that.
But yes, a lightweight fairing would be good. As long as it was super lightweight

My thinking is that with a decent fairing you don't spend as much power pushing air out of the way and could gear quite highly ,enough to pull 110 or 115km while using 3rd as the around town and up hills gear .

This chart illustrates the point well ,from the Allert page .

[Sibbo]

I'm posting this to try to illustrate the amount of hp that goes into pushing air out of the way on a standard unfaired motorcycle.This is the calculator I've been using http://ecomodder.com/forum/tool-aero-ro ... stance.php
It's particularly good in that it gives the percentage of power that goes into aero and rolling resistance .


This chart are the numbers I used for a diesel Enfield ,a drag coefficient of .8 which is about right ,engine efficiency of .3,weight is for bike and rider ...220 kg /484 lb ,frontal area 8 squ foot .




This the results page ,at 45mph 89% of power is going into moving air out of the way and 17% is going to rolling resistance ...moving us along .The rest rolling loses. .At this rate we are getting 135mpg US or 1.75 l /100 km.


If we could somehow reduce the drag coefficient to the same as a car .3 the fuel consumption at 45mph would be .77 litres /100km or 305 mpg US and our lousy 10hp would give a maximum of 80 mph .Amazing stuff !

[snoopy]

There are all the other factors to consider, you tip the bike over and $$$$ to repair.

You can no longer take it off-road or even trail riding which the Enfield with the diesel is great at.

You've seen my fairing, that keeps the bike roughly at 60-65 by reducing the biggest part of the bike drag - the riders chest. The cone I put on the front where the headlight was made no difference at all. The engine simply has no power. Gotta live with it.

BTW 160mpg is enough. Stop being greedy.

[Sibbo]

There are all the other factors to consider, you tip the bike over and $$$$ to repair.

You can no longer take it off-road or even trail riding which the Enfield with the diesel is great at.

You've seen my fairing, that keeps the bike roughly at 60-65 by reducing the biggest part of the bike drag - the riders chest. The cone I put on the front where the headlight was made no difference at all. The engine simply has no power. Gotta live with it.

BTW 160mpg is enough. Stop being greedy.

Yep ,it would be a compromise but I prefer trial Yamahas off road

10 hp is enough to go quickly if you don't spend it pushing air out of the way .

[Sibbo]

I was doing a couple of calculations the other day .

The car I drive is a 1980 Mercedes 240 D, a diesel 4 cylinder with 65 hp and weighing 1.4 ton .
The power to weight ratio is the same or worse than an Enfield mit 10hp diesel wieghing 220 kg with rider.The Merc will do 130 km /80mph ,a clone in standard sit up bike form ,50 to 55mph .80 to 90 km .

The only real difference is the drag of the standard bike versus a car ,even a boxy 30 year old one .

[Sphere]

I think that the Innova has comparable topspeed, and the fairing cuts fuel consumption in half. A 10hp dieselbike with a fairing to guarantee 60mph on the flat is a nobrainer.

[coachgeo]

...

boy I would hate to wreck in that thing. When your body flops off a bike some of the forces applied to you in the accident are transfered to sliding energy across the ground. Not good for skin but better for internal organs assuming proper gear and how good you are at body surfing. Of course being good at avoiding head first pavement diving helps too.

in that get up..... looks like you would come off the bike still but, not as easy and not as early. Could be good or bad. Also as your lauched.... would the front or rear body panel act as a blade that will if not decapitate you; bisect top half of your body from the lower half.

[XLerate]

I think farings & such are very practical. Just a word of caution on any thoughts of home built aerodynamics.

There's no question of the effects of aerodynamics & streamlining on vehicles. One must be more than careful that the same aero effects don't cause unwanted lift. Whether air foils, tunnel effect or an aero enclosure, if lift is accidently caused the results can be disastrous & deadly.

http://lsrdeaths.webs.com/191039.htm

Above link: In 1937 Britain's Eric Ferinhough attempted to regain his Land Speed Record on a supercharged Brough Superior motorcycle. It ended in tragedy when he suddenly left the track at 170 mph. The resulting crash threw him 30 yards, he later died from injuries. Look closely at the pictures at the link above & see the opening at front fender aero, and at rear fender leading edges. No real surprise he became airborne with those lifting scoops at that speed!

Above link: In 1938 AutoUnion was trying for the Land Speed Record in their aerodynamic streamliner driven by Bernd Rosemeyer. The entire body was enveloped in hand-hammered aluminum panels, similar to an airplane. They made a mistake in overlapping the sheets from rear to front. This meant the sheet's leading edges were exposed & rivettted down, while trailing edges were overlapped.

At speed a tire & wheel disintegrated and air then caught under the leading edge of a damaged frontal sheet which began to peel back. This unexpected aerodynamic lift catapaulted the car into the air and it cart-wheeled end over end at well over 250 mph. Rosemeyer lost his life in the crash. Some witnesses of the time said the aero body sheet tore loose first, and as car lifted the tire was cut, blew and wheel was thrown off. I believe the wrong car is pictured on the 'Speed Record deaths' page, should be the Hans Stuck Sr. Type C car at this link:

http://en.wikipedia.org/wiki/Auto_Union

Do be careful?

[Sibbo]

Thank you sir ! I do intend to be careful and am trying to analyse the forces involved . Getting down thrust forward doesn't seem too difficult .The thing that is most difficult to work out is the side thrust from an apparent wind ..... save a side wind of 20km 45 degrees off the nose generating a side lift .Not so bad if it's constant but the fun would really start with the turbulence from a passing semi trailer (tractor trailer? ).I'd tend to go off the road rather quickly .

The only solution I can see to the side lift dilemma is to spoil the curve , generate some separation and so spoil the lift .

There seem to be very real limitations to the efficiency an amateur can achieve if he is going to ride on the public road . A 25% increase should be safely achievable though .

On the other hand have you seen this ? http://www.velomobiel.nl/allert/Recumbe ... orbike.htm

[oldbmw]

I advocate using a proper fairing for touring, ideally the old avonaire full fairing type. My old Triumph 500 ( bit modified would give over 100mpg back in the sixties and had a good top speed.

The best you can get these days is the old avonair handlebar fairing, it protects your upper body and face whilst reducing drag. Now marketed by Sprint manufacturing. Well worth the money. picture of it fitted to my bike in czech republic out side the Church of Bones Kutna Hora, last year.

[Sphere]

Larry, your fairing strikes me as something that makes riding a naked bike more comfortable, and less so making the profile more streamlined? Or am I mistaken?

[coachgeo]

I... picture of it fitted to my bike in czech republic out side the Church of Bones Kutna Hora, last year.
...

any better pics? not having a mental picture of what that thing looks like makes it very hard to see with it being black and shot next to a black car. The two of the same color mask the shape of the fairing.

[Crazymanneil]

This is an interesting video...

http://www.youtube.com/watch?v=Kt6f8w2DOlg

Neil

[coachgeo]

This is an interesting video......

[elmer fud on] vewy vewy intwesting [fud off]

[XLerate]

Searched for some pages with pics of Avonaire fairings. Apparently the handlbar type mentioned above was less common than a full front fairing from what I found. They were made by Sprint in England. Some pics at these pages:

http://aatherton05.home.insightbb.com/F ... naire.html

http://www.vintagebmw.org/v7/node/5225

[TedV]

I looked real close at the Avonaire fairings and the teardrop panniers like on the BMW in the link when thinking of improving my CB250. Only problem, all the fairings were too big for the little CB.

In the USA, take a look at readily available fairings at http://www.airtech-streamlining.com/ They even have some vintage dustbin fairings.

[Sphere]

Frontal view stolen from Larry.

[oldbmw]

larry_fairing.jpg

Frontal view stolen from Larry.

Same trip, picture taken in the French Alps just before the climb up to Mont Blanc.

The fairing is great, your entire upper body including hands do hot suffer from any wind or driven rain. Makes riding much less tiring. I do prefer the full fairings but this is the only one still available. you can order direct from Sprint, or from the BIC.

Thanks Sphere.

I thought the early near view pictures taken in a picturesque village may have been deemed inappropriate

[Sibbo]

I travelled 300 km today on the freeway and unfortunately a diesel Enfield ( which is the bike I'm moving towards) would be impossible in a standard form. This image is a screenshot of a page from this site.http://ecomodder.com/forum/tool-aero-ro ... stance.php
If I plug in the aerodynamic efficiency (drag coefficient) of a Toyota Corolla ...about .34, I can get 121km/hr or 75mph from 8hp. I'm never going to get that kind of drag coefficient from a road rideable bike but it is an indication of the theory . Have a play with calculator and see how close it comes to your bike's performance .Try a drag coefficient of around .9 for an ordinary sit up bike. That gives 55mph from a 9hp diesel.
http://ecomodder.com/forum/tool-aero-ro ... stance.php

[Sphere]

In practice, I am getting the same speed against the wind in 3rd as in 4th (65-70km/h). I have been waiting for a day without wind for a bit now, to see what speed I can achieve with just riding wind. I'm sure being 6'5" doesn't help, but some sort of fairing certainly would. If you can choose a different chassis, try getting one with a fairing. I haven't found a viable option yet (shipping it in from the US isn't viable).

[Sibbo]

6'5" is going to give you a very big frontal area ! That is in the calculator too.

It is nearly impossible to buy a decent aero fairing .Almost everything on the market is either not very effective from a drag perspective or just designed to look good for boy racers.

[Sibbo]

The 1950s Dreamliner was fitted to a 13 hp 350 cc Enfield.It gave another 10mph top speed and 25% better fuel consumption .