What would be fastest?

[DanJR1]

which would be the fastest? a soapbox like the lotus' that ran at goodwood or a faired gravity bike (search google images)? its for a uni dissertation project thanks

[johnny yuma]

1.Frontal area would favour the lying down human 4 wheel capsule over the crouching on bike probably [wind resistance]
2.If tight corners are involved the 4 wheel layout beats 2 any day despite what bike people may think.[time trial or speed only the aim?]
3.Are the entries ballasted to a certain weight or not ?

[DanJR1]

im guessin the 4 wheeled vehicles would have the higher weight limit. which is obviously better

[Adam43]

The acceleration due to the gravity is independent of weight, but a larger momentum may help.

[coln72]

Where's trikes when you need him.

Dont know wha speed gravity racers would reach, but I've been involved with Human Powered Vehicles http://www.racvenergybreakthrough.net/for a few years and a decent bike would top out at 80-90km/h down any sort of decent hill. We will average around 35km/h for 24 hours of racing

[trikesrule]

Hiya Coln I'm here now. Been away racing my Gravity Racers (all Trikes x3) and my 'stock' (unfaired) Gravity Bike. Pleased to let everyone know that for the ninth year in a row I've just won again in every class. The answer to your question is the faired gravity bike would absolutely anihalate the Lotus type machine. Weight has nothing to do with it. All my gravity racers run way less kg than the rest of the field. No the big secret (and I'm about to shoot myself) is reducing frictions to the lowest financially possible. When I build a Gravity Racer one must start with their wheels / tyres / bearings / spoke tensions sorted. The person that does that (me) will always be hard to beat. After that it's finding the optimum longitudinal and height of the CofG and combining that with a decent aero package. But wait theres more. The Lotus machines (mostly 4 wheelers) would be slower through and out of any corner than a decent trike because the trick with trikes is to get them to oversteer going throught he corner and get the slingshot effect of the oversteer adding to acceleration out of the corner. This requires a driver who can actually drive not just steer. A hpv could benefit from this line of thinking too........trikes

[Al Weyman]

Good answer as always Trikes and congrats on your wins.

[coln72]

The Lotus machines (mostly 4 wheelers) would be slower through and out of any corner than a decent trike because the trick with trikes is to get them to oversteer going throught he corner and get the slingshot effect of the oversteer adding to acceleration out of the corner. This requires a driver who can actually drive not just steer. A hpv could benefit from this line of thinking too........trikes

Mmmm, a scary thought actually teaching 17 & 18 year old boys to oversteer into corners. They have enough trouble keeping it upright as it is!!!!

[Notso Swift]

Get a sailor and explain it as Tack and Jive

[trikesrule]

Not an impossible mission. Once I showed my 13 y/o (now nearly17) daughter how to do it and what line to take she makes it look easy and the boys hate her. Darn it she's mm perfect. Hard act to beat when she jumps up into my Open Class. Coln put them in a four wheeler with narrow ridge tyres (2mm) on the rear and tell them to get out there and learn to slide the back end around while gliding downhill. Their kids they'll get the hang of it pretty darn quick. Part of the sliding technique is machine set-up through tyre slip angles. My tyres (rear) are Panaracers and I machine (grind) (dirty smelly job that) the 5mm centre ridge to 1.7mm. Now on a HPV they would wear out pretty darn quick being that narrow. The front has a 4mm foot print (wide) and this set up allows the front to stick while the rear end slides around very nicely thank u. From what I've said here it should give u guys on HPV' something to think about........trikes

[coln72]

One a tight track I would play around with it, but the local one I discribe as a drag strip. Normally there is no need to back off for the corners unless someone gets in their way.

[Speedy1]

In the world of streamlined human powered vehicles 2 wheels rule
fastest speed recorded for 3 wheels is low 60 mph
2 wheels speed record is a tick under 82 mph
this on flat ground
unlimited run up
timed distance is 200 meters
records can be seen at :
IHPVA.org
recumbents.com

this past April I watched a 2 wheeled streamlined bicycle pedaled 54.9 miles in one hour at the Nissan test track in Casa Grande Arizona using less then 300 watts average power

[Notso Swift]

Actually, 300 Watts averaged over an hour is a very impressive output, far beyond the capabilities most people.

(BTW, capitals please, give the guy some respect )

[trikesrule]

Gravity power guys - no pedals thats the issue. You know - top of the hill and let em go .......trikes

[Speedy1]

take the chain off my streamlined bicycle it would be fastest in a gravity race ... I can say with accuracy
underbody airflow is vastly different between the designs and for low power vehicles, very important
true for sure, 300 watts or .4 of one horsepower is more then most humans can do
Tour de France riders are in the 400 to 500 watt range, yet it is rare to find them doing over 30 mph hour runs
this old guy is in the 200 to 250 average watts region and can do
mid 30 mph on a regular basis


point is:
what other machine can maintain 55 mph with so little input?

[johnny yuma]

Originally Posted by Speedy1

take the chain off my streamlined bicycle it would be fastest in a gravity race ... I can say with accuracy
underbody airflow is vastly different between the designs and for low power vehicles, very important
true for sure, 300 watts or .4 of one horsepower is more then most humans can do
Tour de France riders are in the 400 to 500 watt range, yet it is rare to find them doing over 30 mph hour runs
this old guy is in the 200 to 250 average watts region and can do
mid 30 mph on a regular basis


point is:
what other machine can maintain 55 mph with so little input?

Other point is: its not really a "little input" compared to gravity alone, unless you drive the GPV off a cliff.If there was a way for the human body to be horizontal (keep it clean) and steer and put out the 300 watts that vehicle would beat a bike--BUT WE ARE TALKING GRAVITY.Throw in some corners and 4 wheels always beats 2.

[Speedy1]

Smaller frontal area is always a quick path to improved performance.
Skateboard based land luges are the smallest frontal area 4 wheelers running however their cornering performance is not stellar.
The answer to this question probably resides in knowing total frontal area and body shape.
2 wheeled shape I ride is 3.75 square feet and the shape is based on a NACA 6615 laminar flow
The fastest guy at the track these days fits into 2.5 sq. ft.
Goodwood style 4 wheelers and 3 wheelers using bicycle wheels would have a hard time getting this small.
The original question is: which is faster not which corners better
Or maybe I missunderstood the question?