Brand new at this please help !

[fastman614]

Taper41,
The East Coast Timing Association is running an event several times a year in Ohio... on a paved airport runway... One mile of acceleration.... Look them up on the homepage of Landracing and contact them... I am pretty sure that they would be able to accommodate you and your interests in this topic

[dr j]

LSR Guys and Taper41,
I am very impressed with many of these posts describing in a relatively concise manner the thought process behind a team building an LSR Project (especially Hotrod Larry's posts).  Excellent work.
Taper, the problem with looking at existing records and thinking about the physics is that each record is the sum of all the problem solutions chosen and instituted by that team based on its available money and skillsets.  Virtually every LSR team is filled with Gearheads and almost never will you see and Aerohead (except when Bowhunting .  Also virtually every decent size town will have a dynomometer for testing power but only a few places in the country have a wind tunnel.  So most teams are going to push the power aspect of the class engine with data on a dyno and few are going to have the skills to do any more than some basic aero improvements based on seat of the pants ("That looks fast")  More people will be able to buy engine performance parts than will be able to make custom fiberglass shells and fairings. 
As for comparing aerodynamic improvements to power gains I will tell you about my personal experience at ECTA paved standing one-mile at Maxton NC with a small (250cc 4-stroke) bike.  I spent months designing and building a fiberglass tail based on what I thought looked fast within the rule limitations.  And indeed it gained me about 5% topspeed.  According to the rough formula of the cube root of the power increase equals the speed increase if CdA is constant then that 5% was the equivalent of a 15.8% horsepower gain.  Most power gains are on the order of 3%.  So that one aero change was the equivalent of adding 5 power gains.   Of course then I added 50% power increase with Nitrous oxide and indeed the formula held with a corresponding 14% speed increase to 131mph.  So the bottom line is that I think most teams leave a lot on the table for improving their CdA but it is somewhat black magic. 

[Stan Back]

I enjoyed reading your racing story in a recent Bonneville Racing News -- that was you, right?

[dr j]

I enjoyed reading your racing story in a recent Bonneville Racing News -- that was you, right?

Yes, that was me.  Thanks Stan.  I was very happy with Bill Hoddinott's writeup.  This LSR stuff is truly addictive as I have shifted to building two different bikes now.  More when I am further along and in a different thread. 

[taper41]

LSR Guys and Taper41,
I am very impressed with many of these posts describing in a relatively concise manner the thought process behind a team building an LSR Project (especially Hotrod Larry's posts).  Excellent work.
Taper, the problem with looking at existing records and thinking about the physics is that each record is the sum of all the problem solutions chosen and instituted by that team based on its available money and skillsets.  Virtually every LSR team is filled with Gearheads and almost never will you see and Aerohead (except when Bowhunting .  Also virtually every decent size town will have a dynomometer for testing power but only a few places in the country have a wind tunnel.  So most teams are going to push the power aspect of the class engine with data on a dyno and few are going to have the skills to do any more than some basic aero improvements based on seat of the pants ("That looks fast")  More people will be able to buy engine performance parts than will be able to make custom fiberglass shells and fairings. 
As for comparing aerodynamic improvements to power gains I will tell you about my personal experience at ECTA paved standing one-mile at Maxton NC with a small (250cc 4-stroke) bike.  I spent months designing and building a fiberglass tail based on what I thought looked fast within the rule limitations.  And indeed it gained me about 5% topspeed.  According to the rough formula of the cube root of the power increase equals the speed increase if CdA is constant then that 5% was the equivalent of a 15.8% horsepower gain.  Most power gains are on the order of 3%.  So that one aero change was the equivalent of adding 5 power gains.   Of course then I added 50% power increase with Nitrous oxide and indeed the formula held with a corresponding 14% speed increase to 131mph.  So the bottom line is that I think most teams leave a lot on the table for improving their CdA but it is somewhat black magic. 

wow, really , so is what your are saying , that aerodynamics and drag are the most efficient way to increase your speed?

[taper41]

Is there anything that is just as efficient as aerodynamics if money wasnt an option

[fastman614]

Taper41,

You said-
wow, really , so is what your are saying , that aerodynamics and drag are the most efficient way to increase your speed?

That pretty much summarizes it, yes.... but without the REAL ability to have REAL data, most of us do use "seat of the pants" for aerodynamics... and, sometimes we get really lucky ... other times - not so much...

I don't know if any "do - it - yourself" aerodynamics design software exists that can be bought (for, say, $50.00) into which we can put several pictures of our cars, input certain dimensions and, "by magic", the software will tell us the frontal area and Cd of a given vehicle.... as well as helping us to design "better aerodynamics" with the same program.... (hmmmm - even $150.00)

[fastman614]

Is there anything that is just as efficient as aerodynamics if money wasnt an option

The only think I can think of is going to the moon - where there is no atmosphere to cause aerodynamic drag.... is it a practicality to create something like that on the surface of there earth?.... 

[rgn]

in a perfect world where traction was not a problem, when trying to reach top end speeds, is it more advantageous to have the streamliner equipped with 4 wheels like a tradition car or 2 wheels like a tradition motorcycle, lets keep the wheels all at the same with for either vehicle for a controlled variable and say that both liners have the same weight and power along with same dimensions. theoretically wouldn't the motorcycle style have a lower drag thus  enabling it to reach higher speeds.

This is an interesting topic Taper, thanks for putting up this question.  Reading through the post was both intriguing and interesting on many levels.  Using the scientific method in relation to your question, one could answer in the following way:

Question: (As above).


Hypothesis: (One would be to say)

Where two vehicles are identical in every respect, in a test environment where traction is not a factor, with the only difference between the two vehicles being that one vehicle has two wheels, and the other four wheels.  The two wheel vehicle would have a higher top end speed because of lower drag


Test Your Hypothesis by Doing an Experiment:

Two identical models in a wind tunnel, (traction is not a factor, only drag)

Collect your measurements and analyze them to see if your hypothesis is true or false:(Theoretical outcome): 

Common sense/physics, would suggest that a smaller cross-sectional area (due to less wheels) will result in a lower drag coefficient and as a result a higher top end speed.


Communicate-Publish your Results:(Theoretical finding): 

The two wheel vehicle has a higher top end speed because of lower drag


Taper, I think that the two prime factors that relate to a LSR vehicle are those of traction and drag.  Omitting either from theory serves little purpose.  Cheers

[taper41]

Fastman i understand what you are saying but this is more.of.an interesting discussion about physics than anything else and im learning

Given the same size tires dr.j how much more stable is a vehicle that is the
 same size and weight that has 4  wheels rather than 2 in theory would it be 50 percent

[taper41]

in a perfect world where traction was not a problem, when trying to reach top end speeds, is it more advantageous to have the streamliner equipped with 4 wheels like a tradition car or 2 wheels like a tradition motorcycle, lets keep the wheels all at the same with for either vehicle for a controlled variable and say that both liners have the same weight and power along with same dimensions. theoretically wouldn't the motorcycle style have a lower drag thus  enabling it to reach higher speeds.

This is an interesting topic Taper, thanks for putting up this question.  Reading through the post was both intriguing and interesting on many levels.  Using the scientific method in relation to your question, one could answer in the following way:

Question: (As above).


Hypothesis: (One would be to say)

Where two vehicles are identical in every respect, in a test environment where traction is not a factor, with the only difference between the two vehicles being that one vehicle has two wheels, and the other four wheels.  The two wheel vehicle would have a higher top end speed because of lower drag


Test Your Hypothesis by Doing an Experiment:

Two identical models in a wind tunnel, (traction is not a factor, only drag)

Collect your measurements and analyze them to see if your hypothesis is true or false:(Theoretical outcome): 

Common sense/physics, would suggest that a smaller cross-sectional area (due to less wheels) will result in a lower drag coefficient and as a result a higher top end speed.


Communicate-Publish your Results:(Theoretical finding): 

The two wheel vehicle has a higher top end speed because of lower drag


Taper, I think that the two prime factors that relate to a LSR vehicle are those of traction and drag.  Omitting either from theory serves little purpose.  Cheers

Thank you for putting it in a hypothesis for me , one thing i dont understand is why traction on any surface is just as important as drag at higher speeds.
i understand the concept of acceleration and can see why traction would be important in that perspective, but i thought the faster and faster you go the less importance traction has, especially if you have any amount of distance to reach the limit of your vehicle

[manta22]

You still have to overcome aerodynamic force (drag) and the only way you have to do that is by the tire(s) pushing against the salt surface-- traction. The faster you go, the higher the drag force becomes, too.

[taper41]

manta this is wear i get totally confused !

common sense says that 4 tires are always going to have better traction than 2 if the same tires are being used.

so with that said 4 tires also theoretically creates a more drag and always will

so its a double edge sword which i dont get , a two wheel liner will be more aerodynamic and a 4 wheel will always have the better traction pushing against the drag from which it creates?

do you see what i mean

[dr j]

wow, really , so is what your are saying , that aerodynamics and drag are the most efficient way to increase your speed?

Taper-
Your questions usually have several assumptions to keep things simple so mine will too.  I will assume your question continues to relate to a streamlined or partially streamlined class where changes in aero are permitted by class rules.  But realize that in LSR many classes have major restrictions on aero changes in which case your best chance to get an aero advantage is in deciding which model of bike/car to start with.  Now it is my observation that if your question pertains to current or recent streamliner teams then they have put in such an investment of time/energy/money that they do their homework on aero and likely will have used a wind tunnel so there is little left to improve on.  But if we are talking about us mere mortals in Partial Streamlining bike classes then yes.  Because remember that we usually start with production bikes.  Tests in magazines often quote performance and power numbers but never quote Coefficient of Drag.  So most fairings are designed to look fast and sexy so that the bikes will be sold.  or they are designed to effectively protect the rider from wind and rain.  Drag is a minimal thought to Marketing but they do care about horsepower numbers and 1/4 mile acceleration because that sells bikes.  As a result usually power gains from stock HP will be in 3-5% range for cams, high compression pistons, exhaust pipes etc.  But those are easy to buy and perform for the average person.  Aero changes from stock can make a much bigger increase in speed but are much more involved and it is custom work depending on the fit of the bike and rider.  And again there is that knowledge void.  I agree with Fastman that I would love to buy a computer program that could predict drag changes based on pictures and then modified on paper rather than wind tunnel time where you need options to compare effects of changes.

RGN- Remeber that as Blue and other Aero guys keep telling us cross sectional area does not equal drag.  For instance in my case I did not change my frontal area but merely improved the air closure and it markedly helped.  I think what we all need is a personal dyno with wind tunnel attachment....

[Glen]

Taper, you really started something. Hope it's getting you the answers you wanted, We are a diverse bunch of people in LSR. That's whats so neat about LSR.