Frontal Area / Cd numbers

[JR529]

On board cooling capacity has to be limited because of the lack of space so my plan is to stage the systems for peak power through shutdown, and then use an external system in the chase truck to plug high pressure cooling lines into the car when it arrives to help lower the temps as quickly as possible.

I would seriously re-think this approach.

You can't always control how fast your crew gets to the vehicle after a run and a slow response could burn down your driveline, ending your event. Events are few and far between and a prematurely ended event could spell the end of your year.

So your plan is to have a crew waiting for the car at the end of the track? Where, at the 7 mile? then when you turn out at the 4 because of an issue, then what? you just burn down? How about them staging at the 5 so they split the difference. Then you blow a chute and roll to the 8. What about when (not if) you stop on track and are waiting for a push off? your crew wont be there. Add 5 minutes at least till you start rolling towards the return road and your cooling system. And before you say, "I'm not going to run at an event where I cant get to the car quickly" then your options for events gets real thin. I believe that designing a vehicle without sufficient cooling from the start is a foundational mistake that you would have a hell of a time recovering from.

Also, how big a crew do you plan on having?

Seems like you are over-valuing aero. It's important, but not so much that it harms the ability to reliably operate of the car, run, after run, after run, in the real world.

[Simspeed]

I would seriously re-think this approach.

You can't always control how fast your crew gets to the vehicle after a run and a slow response could burn down your driveline, ending your event. Events are few and far between and a prematurely ended event could spell the end of your year.

So your plan is to have a crew waiting for the car at the end of the track? Where, at the 7 mile? then when you turn out at the 4 because of an issue, then what? you just burn down? How about them staging at the 5 so they split the difference. Then you blow a chute and roll to the 8. What about when (not if) you stop on track and are waiting for a push off? your crew wont be there. Add 5 minutes at least till you start rolling towards the return road and your cooling system. And before you say, "I'm not going to run at an event where I cant get to the car quickly" then your options for events gets real thin. I believe that designing a vehicle without sufficient cooling from the start is a foundational mistake that you would have a hell of a time recovering from.

Also, how big a crew do you plan on having?

Seems like you are over-valuing aero. It's important, but not so much that it harms the ability to reliably operate of the car, run, after run, after run, in the real world.

Well you've made a valuable point JR...as I said I'm a LSR rookie and everything you noted is certainly valid and I obviously didn't think it through logistically.  Since I made that comment I've studied up on refrigerant cooling for the intake charge and I've come to the conclusion that the same can be applied to the IC and motor/gen powerplant cooling.  Now I have to see if the approached I came up with can be fit to the car for both systems.  Thanks for helping me see the hurdles and keeping my thinking straight... Helpful input from you experienced guys is great.  What a sport...

[robfrey]

As far as cooling goes, it is actually very difficult to beat good old ice water. This goes for a intercooler coolant  and ice water heat and exchanger for engine coolant IE radiator in ice water bath.

My other idea was start spraying high pressure ice water misters (from intercooler water) onto the radiator about halfway through the run.

Also be aware that you will need turbo chargers that are 10-15% bigger for a given HP figure for rotary engine.


Rob Freyvogel
#496
AA/BFS

[jacksoni]

Recognizing the preliminary stages of your project I will make a suggestion that is common when someone comes to the forum with ideas. (continue with your research and be aware you may need to make design changes along the way. I think you understand this.) But, make time to come to Bonneville, Speedweek, Cook shootout if there is one, World of Speed, World finals etc. Look at the cars. Talk to the owners, builders, drivers. Generally all will be willing to chat. Look at the packaging and how crowded it gets in there. Continue with your aero studies but consider you may need to give up some frontal area for space and stability. I think your project sounds exciting. A big leap in technology and maybe doesn't come to fruition but that is no reason not to try to come up with a workable design and then build it. Looking forward to follow your progress. Although it may be that it won't fit a SCTA or other class (FIA rules are different) or maybe no class or rules but safety is paramount. Get a SCTA rule book and study it. A Lot! There is a lot of information about construction and safety issues that can be applied to help you even if you don't run the car at an SCTA meet. JMHO

If the chutes fail and the brakes fail you will be in SLC pretty quick and your crew will be waaaayyyyy back there as you disappear over the horizon.    

[jacksoni]

Recognizing the preliminary stages of your project I will make a couple of suggestions that are common when someone comes to the forum with ideas. (continue with your research and be aware you may need to make design changes along the way. I think you understand this.) But, make time to come to Bonneville, Speedweek, Cook shootout if there is one, World of Speed, World finals etc. Look at the cars. Talk to the owners, builders, drivers. Generally all will be willing to chat. Look at the packaging and how crowded it gets in there. Continue with your aero studies but consider you may need to give up some frontal area for space and stability. I think your project sounds exciting. A big leap in technology and maybe doesn't come to fruition but that is no reason not to try to come up with a workable design and then build it. Looking forward to follow your progress. Although it may be that it won't fit a SCTA or other class (FIA rules are different) or maybe no class or rules but safety is paramount. Get a SCTA rule book and study it. A Lot! There is a lot of information about construction and safety issues that can be applied to help you even if you don't run the car at an SCTA meet. JMHO

If the chutes fail and the brakes fail you will be in SLC pretty quick and your crew will be waaaayyyyy back there as you disappear over the horizon.    

[Simspeed]

Rob and Jacksoni....great advise from you both...thanks.  I recognize that ice water works and the majority of records over the years were set using it.  I'd probably use it too if I could because its the least expensive, highly effect solution.  Unfortunately I'm committed design wise to a small cross section/low Cd to take advantage of the Rotary IC/Gen-motors streamline packaging which I believe offers the best aerodynamic opportunity to push the wheel driven record to 600 or above.  If what I'm proposing in my design turns out to be nothing more than a wishful exercise then that's ok....moving the goal post forward takes new ideas and group thinking on how to make those ideas work for some capable team.  Thanks to everyone... 

[7800ebs]

Years ago, Don Vesco converted his motorcycle liner to a car. Offy powered. A wider track than you are thinking, as I recall about 10 to 12 inches. 

The wreckage was over a mile...

I quick FYI .. To go 500 or even 600...in 5 or even 7 miles, you will never get to terminal velocity.

traction will be the limiting factor..

Build a car that you can survive a 400, 500 or 600 mph crash..  you can die slower also..


oh yea.... if you are looking for min CD.. then splitters wont work, as they need frontal high pressure to work, the opposite to what you are designing.


good luck

start cutting tubing..

salt is leaving quickly..


bob dalton

[Peter Jack]

Here's a thought right out of left field and you can treat it as such if you want but it could simplify the whole process.

Why not start by building a relatively simple lakester using your proposed powertrain and maybe even the body shape and dimensions. It could be done using a single closer to stock engine. This would allow you to try out different packaging and cooling theories as well as other challenges that might arise without adding stability issues and the complexity that arises with multiple power sources.

People who have lots of experience on the salt often find a lot of issues when they try highly complex projects. A little experience with a more simple project may be valuable and might get someone else interested in the long term goal with deeper pockets. A little extra financial help never hurts for most of us. 

Good luck with the project. As you have intimated it keeps us all thinking and I believe that is a good thing. 

Pete

[Simspeed]

Hey Bob and Pete...thanks for the input. I may well have to rethink the track width or find a different way of vertically stabilizing the car.  I like your idea Pete starting small and building up is sound advise for all the reasons you gave.  Moving forward may eventually require that approach.

In terms of traction what's the thinking on total tires and placement?  This project is aimed at setting the fastest wheel driven speed so record class rules aren't a limiting factor so long as we're allowed to run for time at event opportunities.  Could we run 3 or 4 rear drive wheels and 1 lead steering wheel for example?  From a packaging standpoint a wheel combination like that would fit my desired envelop with better traction opportunity.  Is there a limit on total wheels for an unlimited liner?

What about retractable outriggers that spring out should the car begin to tip over left or right.  I've seen the bike liners use something similar during launch.  Thanks...

[John Burk]

Simspeed , a guy named Eric Ahlstrom used to post here as Blue . He did aerodynamics professionally . He pointed out to us that the majority of a streamliner's drag is skin friction and frontal area isn't that important as long as the shape is good .

If the tail fin is tall enough a high speed yaw doesn't necessarily mean a roll .

[Simspeed]

Make a cockpit out of pvc tubing.. get a firesuit, hans, and current helmet on, and see if you fit...

My car 'was" (lol) 20.5" inside and if you ever saw me get in, it was tight. Not impossible, but tight.. 24 outside, body was 27" there to allow line clearance, total 30" at valve cover.

bob

That is tight Bob..I may have to let the shape scale up some to find room for everything.  For now though I'll continue with the present cross section since it cost nothing but time to draw something different.  Thanks...

[Simspeed]

Simspeed , a guy named Eric Ahlstrom used to post here as Blue . He did aerodynamics professionally . He pointed out to us that the majority of a streamliner's drag is skin friction and frontal area isn't that important as long as the shape is good .

If the tail fin is tall enough a high speed yaw doesn't necessarily mean a roll .

Well I like the idea of increasing the tail fin area to help out with the stability.  Not much frontal area to a 1" fin.  I've emailed Woody hoping to hear back from him before long.  Thanks.

[robfrey]

I’m liking the idea of a lakester as it is a great place to develop your power package. After you have worked out all the bugs, you will have a much better idea on what you can get away with after you have a season or so running it in the lakester.
You may be able to find one used, do your development work, then sell it for close to what you paid for it.
Do not underestimate the power of actual salt testing your power supply. It will show issues that are not experienced in any other forms of racing.
I know this sounds crazy but designing the body is one of the last things you want to do (in my opinion). It is of course great to have an actual design in mind the whole time but making wise choices about what engine, transmission, third member, turbos, cooling, intercooling, tires and all the other stuff that is not going to be fabbed needs to locked in first.
The body and tanks will then will just need elegantly wrapped around what cannot be changed.
I do like the way you dream big though! Now you just have to figure out which is the wisest way to get there and decide whether or not it is actually worth the time and expense to get there.
Yeah I know, that last one is a doosy!


Rob Freyvogel
#496
AA/BFS

[tortoise]

Well I like the idea of increasing the tail fin area to help out with the stability.  Not much frontal area to a 1" fin. 

a guy named Eric Ahlstrom used to post here as Blue . He did aerodynamics professionally . He pointed out to us that the majority of a streamliner's drag is skin friction and frontal area isn't that important as long as the shape is good .

[Eddieschopshop]

There are very few that have gone really fast,,  you have several here chiming in.  There are those that theorize and those that do, take advantage of those that have!