Author Topic: Simspeed UWD LSR Design Project  (Read 89918 times)

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Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #105 on: August 04, 2019, 12:26:45 AM »
I've been studying the published FIA regulations as they relate to some of the questions that have come up in the discussion of this evolving concept. A few things I've noticed:

Per section D2.4.2, it looks like it's not a hybrid by their definition.

I can't find anything disallowing movable aero for category A (automobiles) although there is a specific entry allowing same for "Special" automobiles, apparently meaning rockets and jets, so maybe that  implies their prohibition for just plain automobiles. This may be irrelevant, however, because of section D4.2.7, which establishes an Absolute World Wheel Driven Record. 

Does anybody know anything for sure about this?

Hi Tortoise,
Thanks for looking these up.  It appears supercharged rotary engines vehicles are category A grouped under V and XV sections excluding electricity and solar power sources, and electrical engines under groups (XVIII, XV, VIII, VII).  So in our example what is the power plant and what is the source of power relative to these classifications?

Is the IC engine the engine type or generator for the source of power?  The wheels are driven by electric motors so should this be considered an electrical engine with an XVII and/or XIV external power source?  By FIA definition its not a hybrid as you say tortoise because it has no self-rechargeable energy... no batteries.  Because the supercharged rotary engines generate electricity which powers the electric wheel motors it appears this vehicle would most likely be considered and electric powered vehicle under the category A; XIV group.

The classification makes no difference to me as the goal is to claim the unlimited wheel driven record for a 4 wheel vehicle.  It might be more reasonable to classify this as a category C vehicle where the IC/Gen/Motor engine is a combination apart from those shown under category A.  Your thoughts?  Thanks... Terry

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #106 on: August 04, 2019, 12:36:07 AM »
I'd like to get a comparison of frontal area between this project's latest design and other contending streamliners regardless of class.  Does anyone have FA info for 4 or more wheel streamliners? Let's include the bikes too. How about Cd numbers for any of the same?  Thanks... Terry

Offline jacksoni

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Re: Simspeed UWD LSR Design Project
« Reply #107 on: August 04, 2019, 07:29:49 AM »
By refining the body geometry and re-configuring the chassis somewhat I was able to lower the frontal area another 10% to 4.774 sq.ft.  Without the active aero wing FA drops just under 4 sq.ft. again.  This body is much cleaner and better reflects what I'm hoping to achieve for this project.  I'm unsure which will be the better combination...more downforce at the expense of FA; or no active downforce and a 10% drop in NA.  I know weight is needed for traction but I'm not happy with adding a lot of ballast to get it.
You have to keep in mind that, more or less, HP required to overcome rolling resistance and mechanical drag goes up with the square of speed while HP to overcome aero drag goes up with cube of speed. Thus, in general, ballast is better than aero downforce.
Jack Iliff
 G/BGS-250.235 1987
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  G/FAlt- 193.934 2021 (196.033 best)
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Offline ggl205

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Re: Simspeed UWD LSR Design Project
« Reply #108 on: August 04, 2019, 09:42:20 AM »
Thus, in general, ballast is better than aero downforce.

Unless you can get that downforce with little to no drag penalty (low ride height, flat bottom).

John

Offline jacksoni

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Re: Simspeed UWD LSR Design Project
« Reply #109 on: August 04, 2019, 10:43:01 AM »
I am going to opine that best aero drag is with no lift or downforce, regardless of how it is obtained. Any change in that is a drag penalty. IO or others may chime in and say I'm wrong and I will be educated thereby.
Jack Iliff
 G/BGS-250.235 1987
 G/GC- 193.550 2021
  G/FAlt- 193.934 2021 (196.033 best)
 G/GMS-182.144 2019

Offline tortoise

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Re: Simspeed UWD LSR Design Project
« Reply #110 on: August 04, 2019, 12:07:02 PM »
. . . in general, ballast is better than aero downforce.

Given a long enough course, more or less true. Even then, a heavily ballasted car can have a heat soak problem.

Offline tortoise

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Re: Simspeed UWD LSR Design Project
« Reply #111 on: August 04, 2019, 01:17:27 PM »
The classification makes no difference to me as the goal is to claim the unlimited wheel driven record for a 4 wheel vehicle.
But can you run active aero? The Carbiliner has it, but they've never claimed an FIA record.
« Last Edit: August 04, 2019, 01:24:26 PM by tortoise »

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #112 on: August 04, 2019, 08:16:09 PM »
The classification makes no difference to me as the goal is to claim the unlimited wheel driven record for a 4 wheel vehicle.
But can you run active aero? The Carbiliner has it, but they've never claimed an FIA record.
Well Tortoise I guess I'll have to ask the FIA about that unless someone already knows post the answer here.

Attach is my idea for a flat plate areo downforce device.  The NASA Foilsim app shows this will add 550 lbs of downforce and 137 lbs of drag at 250 mph which is the max speed for the app.  Much less than the wing but a smaller surface area.  Probably not very effective at slow speed.  It adds 1.47 sq.ft. to frontal area at max up angle but that reduces back to zero if lowered flat at speed.  Actual FA would depend on what angle is used through the end of the run based on traction needs. Also acts as an air brake if fully raised on shut down.

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #113 on: August 04, 2019, 08:30:28 PM »
You have to keep in mind that, more or less, HP required to overcome rolling resistance and mechanical drag goes up with the square of speed while HP to overcome aero drag goes up with cube of speed. Thus, in general, ballast is better than aero downforce.

Hi Jacksoni...yes, I see your point but there's a trade off in increased time to accelerate the added mass.  Ballast has shown to increase total speed so where the optimum for traction, speed and weight lies is anyone's guess.  Aero downforce gives you nothing at the start so traction will be limited to actual weight factored by applied torque and the traction coefficient of the salt.  One advantage this powertrain has is fine control of wheel motor torque that's not tied to the IC engines.  The electric motor controllers can be programmed for traction control that applies torque as needed tuned to track conditions. Thanks... Terry

Offline STICK777

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Re: Simspeed UWD LSR Design Project
« Reply #114 on: August 05, 2019, 02:23:02 AM »
>Do you know what the drive train consist of?  Are there any links to the builder?  What's the name so I can look to see what I can find out about it?  Thanks... Terry

I think this hasn't been answered yet. The green car goes under the appropriate name of 'Salt Shark' , has indeed front wheel drive and is powered by a blown BB Chevrolet IIRC
running in B/GS.
You can find images and probably a bit more on here: https://www.facebook.com/pg/Bonneville-Salt-Shark-226594851348688/photos/?ref=page_internal
« Last Edit: August 05, 2019, 02:28:53 AM by STICK777 »

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #115 on: August 05, 2019, 03:59:37 AM »
>Do you know what the drive train consist of?  Are there any links to the builder?  What's the name so I can look to see what I can find out about it?  Thanks... Terry

I think this hasn't been answered yet. The green car goes under the appropriate name of 'Salt Shark' , has indeed front wheel drive and is powered by a blown BB Chevrolet IIRC
running in B/GS.
You can find images and probably a bit more on here: https://www.facebook.com/pg/Bonneville-Salt-Shark-226594851348688/photos/?ref=page_internal
Hi Stick,
Thanks for posting this.  We did get this link earlier and I spent a good deal of time going over all the build photos.  I really like what the owner has done in executing this novel design.  I hope he has a great event.  Anxious to see what the machine will do.  Thanks... Terry

Offline jacksoni

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Re: Simspeed UWD LSR Design Project
« Reply #116 on: August 05, 2019, 08:02:51 AM »
You have to keep in mind that, more or less, HP required to overcome rolling resistance and mechanical drag goes up with the square of speed while HP to overcome aero drag goes up with cube of speed. Thus, in general, ballast is better than aero downforce.

Hi Jacksoni...yes, I see your point but there's a trade off in increased time to accelerate the added mass.  Ballast has shown to increase total speed so where the optimum for traction, speed and weight lies is anyone's guess.  Aero downforce gives you nothing at the start so traction will be limited to actual weight factored by applied torque and the traction coefficient of the salt.  One advantage this powertrain has is fine control of wheel motor torque that's not tied to the IC engines.  The electric motor controllers can be programmed for traction control that applies torque as needed tuned to track conditions. Thanks... Terry
I think this topic has come up before in your project. I mention it only because your initial premise for the car was the minimal frontal area and lowest possible Cd. Great goals. Most of the fast cars, not just the 'liners, have power in excess of traction and, within the rules struggle to improve aero in any meaningful way. Therefore ballast. Indeed accelerating the added mass is a problem and as you point out, the balance of power vs traction and at higher speeds the aero becomes the major factor. For cars like yours, there are no paved surfaces available, only salt or dirt and traction on those surfaces is variable foot by foot down the track so any attempt at calculating traction coefficients  really tough. Your traction control will go a long way to make things work but I think there is no way to really see what you need until you have an actual car and see what happens. Sure build it strong and it is going to "weigh  a ton" from the start. Maybe you don't need anything added but you have  the possibility of adding active aero  or ballast as needed and see what gives the best result.
Jack Iliff
 G/BGS-250.235 1987
 G/GC- 193.550 2021
  G/FAlt- 193.934 2021 (196.033 best)
 G/GMS-182.144 2019

Offline Lemming Motors

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Re: Simspeed UWD LSR Design Project
« Reply #117 on: August 05, 2019, 10:32:03 AM »
I fall in the 'no lift or downforce' aero camp (active aero is another story and too sophisticated for my skills) but I am only mid build so can't prove anything.

The airbrake discussion made me think of the SLR's when the disc brakes of Dunlop were giving the Jags a shorter stopping distance on the Mulsanne ....
A Bonneville Lakester please barman.
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Just a squeeze.

A Squeeze of Lemming it is sir.

Offline ggl205

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Re: Simspeed UWD LSR Design Project
« Reply #118 on: August 05, 2019, 01:50:39 PM »
I tried something like that once with my first road car but it was my hood that accidentally popped up. It did slow me down but caused a serious vision problem.

BTW, Sim, your car appears to be flat bottom with low ground clearance. That should provide a measurable amount of suction (downforce) with little if any drag.

John

Offline Eddieschopshop

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Re: Simspeed UWD LSR Design Project
« Reply #119 on: August 05, 2019, 09:54:16 PM »
I like the exhaust.  I have never been able to really "prove" the results,  it would take a wind tunnel at full speed and the ability to put full load on the motor to really get accurate results.  On paper it makes sense.