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Author Topic: Simspeed UWD LSR Design Project  (Read 17345 times)

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Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #30 on: July 28, 2019, 08:43:40 PM »
If anyone has a link to an accurate aerodynamic hp to speed calculator I'd appreciate a share.  I've looked at all I could find through Google and the results vary widely.  Do any of the calculators you've use correlate well to actual speeds of your car or bikes? I'm using the following inputs to base line this design:
Cg = .09
FA = 5.261
Weight = 4000
Speed = 600 mph

Thanks... Terry

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #31 on: July 28, 2019, 08:53:18 PM »
Hi Terry,
From a complete novice AND vintage bike rider (  :dhorse: )!!!

Was looking at this frontal forest of tubes and your narrow vision slit area, surely less than 5 degree vision cone and a recipe for no side vision at all, important if you want to foresee in good time obstacles, pot holes, barrels, cones, or whatever else delimit the course 1 or 2 seconds in front of you @ 450mph!!!

Obviously, if you go forthwith with your front driver compartment, it will solve this issue at once!!!

Does some one higher up insist on so much tubing? If you slide to a rest it's useless, if you somersault, surely you want a bit of crumble availability to absorb some of the impacts and the G forces before they get to the driver???

More to the point, is carbon fiber still a no-no in LSR circles??? An F1 driver's cage is virtually indestructible, not to mention the light weight aspect!!!



Patrick

Hi Patrick,
Yes, V.5.2 has some vision issues due to the driver placement.  I've looked at an exposed driver canopy on a mid mounted cockpit in earlier versions but here I wanted to try a sweeping body geometry.  The DIF V.5.3 above eliminates the vision problem AND reduces the FA significantly so that's what we're going with for now.

The forest of tubes was incorporated in V.5.2 because I had so much weight forward of the steering wheels and needed the stiffness the extra tubes provided.  With V.5.3 I was able to move most of that weight behind the wheels and the driver section is a self contained structure that is well supported at the parting bulkheads. 

Use of a carbon fiber tub is obviously a desirable option in terms of stiffness and weight savings.  Several LSR vehicles have used one with success.  The Ohio State BB3 electric car used an IRL tub as the basis of their chassis design rather than build their own because the crash data was already known and the cost was in their budget.  This project is based on a tube chassis because that's what I know and have experience with.  Cost is also a factor but overall width is too which comes into play for an IRL cockpit which is an unknown to me.  Thanks... Terry.
« Last Edit: July 28, 2019, 09:01:38 PM by Simspeed »

Offline thefrenchowl

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Re: Simspeed UWD LSR Design Project
« Reply #32 on: July 29, 2019, 11:29:58 AM »
Thanks Terry...

Four years back, I was planning a partially streamlined bike, me lying down like you but not enclosed:



And my engine, supercharged methanol fed 900 side valve Vee Twin lying where your front wheels are.

Since I'm in Great Britain, I needed the bike able to part in two for ease of transport...

After some back and fro with the SCTA tech boys, we agreed a partition design with back to back full bulkheads, each steel and 1/2" thick. about 10 bolts and 6 pin locators...

When the quotes arrived to cut and machine all that, I decided to stick with std motorcycles until I win the lottery!!!!!!!!!!!!!!

All that to say your 5 holding bolts look a touch lightweight to me with so much cantilever up front

Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline Peter Jack

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Re: Simspeed UWD LSR Design Project
« Reply #33 on: July 29, 2019, 12:55:19 PM »
Just a comment, and I have no proof of the theory, but I've always felt that when a driver is placed that far forward he/she has less feel for the yaw position of the car and this could prove disastrous. Lights and/or alarms may in theory help with this but under the pressure of making a run it's very possible that the driver wouldn't react to such in time.

Pete

Online Stainless1

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Re: Simspeed UWD LSR Design Project
« Reply #34 on: July 29, 2019, 01:54:07 PM »
I agree w/PJ... I think sitting in front of the steerable wheels  is asking for issues.  You will loose the "butt feel" of the car.
Stainless
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MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #35 on: July 29, 2019, 04:45:32 PM »
Just a comment, and I have no proof of the theory, but I've always felt that when a driver is placed that far forward he/she has less feel for the yaw position of the car and this could prove disastrous. Lights and/or alarms may in theory help with this but under the pressure of making a run it's very possible that the driver wouldn't react to such in time.

Pete
Quote
I agree w/PJ... I think sitting in front of the steerable wheels  is asking for issues.  You will loose the "butt feel" of the car.

Thanks for your comments guys.  I've received several comments like these concerned about the lack of back feed of a vehicle's yaw attitude from a DIF position.  A little research confirms the condition and how it's been addressed in aeronautics since the Wright brothers with yaw or slip indicators.  Gliders are especially susceptible to the detrimental effects of increased drag when yaw or slip conditions are encountered in flight. The widespread use across all types of airplanes (gliders to fighter jets) of a simple mechanical device called a "Yaw String" (it was invented by Wilbur Wright) allows air pilots to see yaw movement in real time and react quickly to counteract the effect by dialing in more opposite rudder as a control.

Naturally LSR vehicles will experience more disastrous outcomes when late reactions to yaw conditions result in lost of control and crashes.  A Yaw String should in practice work equally well for a DIF streamliner as it does for large percentages of air pilots that rely on them today.

So, what is a Yaw String?  Its nothing more than a piece of string or yarn taped to the exterior of the canopy or fastened forward of the canopy in the pilots line of sight.  As the tail of the craft moves left or right from zero yaw, the string will instantly follow suit indicating the change in direction of air flow over the nose of the craft.  Because the string is in the pilot's line of sight s/he will see it move without taking his/her eyes off the path ahead.  Instinctively, as with DIM or rear cockpit positions, minute steering corrections will be made to counter yaw movements to keep the vehicle tracking as straight and true as humanly possible.
https://www.youtube.com/watch?v=A1dU63d7HHw

If this should be the case, which I have no reason to believe otherwise considering it's long history of use in aeronautics,  I consider the aerodynamic and visual advantages of DIF chassis geometry outweigh the risks where a yaw string is put to use on the vehicle.  Does anyone know of a DIF streamliner that's used a yaw string successfully?  How about unsuccessfully?  I'd be interested to read about their experiences.  Thanks... Terry
« Last Edit: July 29, 2019, 05:10:02 PM by Simspeed »

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #36 on: July 29, 2019, 04:58:53 PM »
Thanks Terry...

your 5 holding bolts look a touch lightweight to me with so much cantilever up front

Patrick

Hi Patrick,
Thanks for sharing that experience.  You could be right about a need for more connection points to secure the cantilevered front chassis section.  Should we get to the point in the project where a structural review of the chassis design is warranted, we'll rely on an engineer's recommendations to finalize drawings before construction begins.  Thanks... Terry

Offline tortoise

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Re: Simspeed UWD LSR Design Project
« Reply #37 on: July 29, 2019, 05:35:33 PM »
It's not clear to me that a breakaway cockpit is safer in the LSR context.  I can see arguments for both sides of the question. 

Offline Peter Jack

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Re: Simspeed UWD LSR Design Project
« Reply #38 on: July 29, 2019, 06:30:06 PM »
Terry:

I think in this case we're dealing with the real world as opposed to theory. While a yaw string may work with an aircraft, even a high speed one, there is a lot more space and time between the aircraft and the ground than there is between a lsr vehicle and the ground. When something does go sideways and the adrenaline does start to flow even heavier is the driver going to concentrate on a piece of string or where he's going? The Wright brothers were travelling at a little less than 400 mph.  :-D :-D :-D

The driver of a vehicle is very slow to react to instrumentation as compared to what he can see around him and will probably look right through a close up piece of string to the ground he is about to cover at very high speeds, whether in a straight line or tumbling.

Pete

Offline Interested Observer

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Re: Simspeed UWD LSR Design Project
« Reply #39 on: July 29, 2019, 07:21:43 PM »
Further to Peter's comments..
Yaw in an aircraft is of little consequence--not so in LSR.
When landing in a cross wind does the pilot pay attention to the ?yaw string? or the world around him?

Offline manta22

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Re: Simspeed UWD LSR Design Project
« Reply #40 on: July 29, 2019, 07:53:54 PM »
Re: "Yaw String"

Terry, I became familiar with a yaw string when I was taking glider lessons in Babenhausen, Germany back in '62. The Babenhausen Aero Klub flight instructor was a WW II Messerschmidt fighter pilot. The club trainer was a 2-place glider with him sitting in the rear and me sitting ahead of him. The first few flights were fun even though the English/German language was a real problem. On one flight he wanted to demonstrate how to settle the glider for a landing even from a too- high approach to the field, a large open area adjacent to the woods.We flew for a short time and he brought the plane in on a very high approach over the woods when he suddenly kicked it into a very large yaw angle. The yaw string looked almost sideways and we dropped like a rock until the altitude was a normal approach and he straightened out and landed. That unannounced maneuver scared the crap out of me.  I sure never forgot that yaw string!

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline jl222

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Re: Simspeed UWD LSR Design Project
« Reply #41 on: July 29, 2019, 08:34:41 PM »
If anyone has a link to an accurate aerodynamic hp to speed calculator I'd appreciate a share.  I've looked at all I could find through Google and the results vary widely.  Do any of the calculators you've use correlate well to actual speeds of your car or bikes? I'm using the following inputs to base line this design:
Cg = .09
FA = 5.261
Weight = 4000
Speed = 600 mph

Thanks... Terry

  I have a program called Bonneville Pro by Racing Secrets a drag race results program modified for Bville. Pretty accurate except for acceleration rates '' to quick'' chart to put in cd, frontal area, weight,
tire width, gear ratio, tire roll out, and hp.  Gives a result chart with time, rpm distance and mph. Also wheelspin if to much hp for wheel width. Needs a downforce in put. Maybe newer versions have it.
 
 I  put all that data from Summer Brother's streamliner and it came out on the money.
 425 mph with 2400 hp.

  So unless your streamliner is way more aero you're going to need a lot more hp than 2400 to go 600 mph.

                    JL222

             

Offline desotoman

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Re: Simspeed UWD LSR Design Project
« Reply #42 on: July 29, 2019, 09:52:05 PM »
Terry,

Please listen to Pete, Stainless and Interested Observer about the Yaw String.

Remember the air is fluid, the ground is not.

If you really would like a nice long type of Yaw String with lots of seat feel,
place the drivers compartment in the rear of the vehicle. Then the length of
the car is your Yaw String. Just a suggestion.

Tom G.
Asking questions is one's only way of getting answers. As a young boy I was always taught that there is no such thing as a stupid question. It suggests that the quest for knowledge includes failure, and that just because one person may know less than others they should not be afraid to ask rather than pretend they already know. In many cases multiple people may not know but are too afraid to ask the "stupid question"; the one who asks the question may in fact be doing a service to those around them.

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #43 on: July 29, 2019, 10:50:08 PM »
I've revised the steering assembly from an upper to lower spindle position per recommendations from Tom B.  Got rid of the right angle gear boxes and added double shear mounts to most of the linkage connections.  I also changed the camber back to zero degrees to accommodate flat plane mounting of the steering.  Not sure if that's suitable but I've read where others are using zero camber with zero scrub radius which this design has.

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #44 on: July 29, 2019, 10:57:05 PM »
It's not clear to me that a breakaway cockpit is safer in the LSR context.  I can see arguments for both sides of the question.

Hi Tortoise,
The only reason I'd think the break away cockpit is any safer is deployment of a dedicated chute acting on a lighter total mass once the main chassis and drive components are separated.  Secondly I guess is the reduced risk of fire as fuels and oils are also separated.  Either way its a risky proposition with a crash of any type.  Thanks... Terry