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Author Topic: Simspeed UWD LSR Design Project  (Read 25472 times)

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Offline TD

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Re: Simspeed UWD LSR Design Project
« Reply #225 on: September 27, 2019, 08:34:16 AM »

I've added an intake scoop given the inline arrangement of the intake ports of the stacked rotors.  I'm thinking this should not add significantly to the total FA given that air hitting the scoop opening is being suck into the engine rather than being displaced and forced to move around solid surfaces on the body.  Anyone know otherwise?  Is there a better type of scoop to use here? 
There's an interesting discussion of air scoop design in the Goldenrod book: https://goldenrodbook.com/   Disclaimer: I have no dog in this hunt.

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #226 on: September 27, 2019, 11:59:49 AM »

As a rule, each morning they would pull off all the body panels, all held via dzeus fittings, different sizes/depth at different locations depending on local stress. Reassemble, do a run, have problems, do it again, say 4 times a day at easily 1/2 hour minimum... That's 2 hours minimum gone in a day just for the skin...

You need to simplify yours!!!!

They also use their cockpit after a run to store the parachutes. It takes an awful long time to set them flat on the salt and roll them in the right fashion to be safely inserted in the tubes and this is done in the pits. Make sure your cockpit is big enough for that.

Hi Patrick,
Thanks for sharing the Turbinator info and pictures.  I'd enjoy watching their race week routines to see how the fastest UWD record holder goes about its business specific to their vehicle.  Also thanks for the drawings complement.

A couple of thoughts regarding your comments... The Turbinator body panels you are describing aren't structural I don't believe.  CV plating enveloping the CF tubing chassis on Simspeed are.  The method of attachment is designed for that purpose but does allow the panels to be removed for maintenance as needed.  If you watch the Speed Demon crew at the end of each run they remove body panels via screw guns acting on torx screws.  That seems to work well for them so I consider the same method viable for our CF structural plating.  The exterior body shell will likely also be fastened to the chassis using flush mounted screws.  I used Dzus fasteners on drag cars for all sorts of panel fastening needs but here I think screw fasteners are the better alternative.

Design considerations for the Simspeed cockpit are exclusively top speed related.  How and where to carry the chutes after each run is quite secondary as there are a number of alternative options available that don't compromise the primary mission.  A spent chute bag that can be hung over the tail stabilizer for the return trip to the pits or impound is one easy option that comes to mind.  Thanks... Terry.

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #227 on: September 27, 2019, 12:10:06 PM »
There's an interesting discussion of air scoop design in the Goldenrod book: https://goldenrodbook.com/   Disclaimer: I have no dog in this hunt.

Hi TD,
Thanks for the link.  I've done some research on scoop design and I'll be revising the current design for something a little more aerodynamic.  Thanks... Terry.

Offline 7800ebs

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Re: Simspeed UWD LSR Design Project
« Reply #228 on: September 27, 2019, 12:33:54 PM »
Interesting design... so you get to be the first one to the seen of the crash, great. And assuming 7' circumference around the car body, and 500 mph,  in a pencil roll crash, you should be able to spin at about 6000 rpm... How do you stop that?  You need... Everyone needs to think about that... How do I survive a crash at speed... The salt is not smooth often.. Way too much time is spent on how to go fast, and Not enough on surviving.... Just Saying... bob


ps: think crush zones, bendable members, anti pencil designs, auto chute deployment, yaw / roll /impact switches..

Offline STICK777

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Re: Simspeed UWD LSR Design Project
« Reply #229 on: September 27, 2019, 01:45:36 PM »
Good thought on mentioning the likelihood of a crash.
Though it's maybe better when the car just slides and eventually pinrolls... there were many
accidents that ended with no or only little harm. Of course there were others that didn't  :-(

Now in case of the Carbiliner crash it 'might' be that the threewheeler configuration was not
favourable... in case of a crash. When a part of the car gets 'caught' by the salt it will result
in terrible distruction... Sadly that obviously happended to the Carbiliner. I sincerly hope that
Rob is on a good way to a full recovery.

@Bob: I watched the footage of your crash last year... you are one brave and lucky guy!!

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #230 on: September 27, 2019, 04:35:51 PM »
Interesting design... so you get to be the first one to the seen of the crash, great. And assuming 7' circumference around the car body, and 500 mph,  in a pencil roll crash, you should be able to spin at about 6000 rpm... How do you stop that?  You need... Everyone needs to think about that... How do I survive a crash at speed... The salt is not smooth often.. Way too much time is spent on how to go fast, and Not enough on surviving.... Just Saying... bob


ps: think crush zones, bendable members, anti pencil designs, auto chute deployment, yaw / roll /impact switches..

Hi Bob,
Thanks for your input. I think this is the second time you've mentioned the design being first to the scene of a crash... how have other designs such as the Nebulous Theorem series of cars dealt with that problem?  Seems like any long thin design without a tall wing structure of some sort has the potential to roll in the event yaw takes it sideways.  I might note that tire explosion or deflation appears to be high on the list of crash inducing events.  I've incorporated aluminum wheel/tires here as a preventive measure to eliminate rubber tire issues.  Also, the use of FWD only is designed to eliminate RWD induced yaw concerns in control of the car at speed.  Anything can happen of course but what other steps can you think of to help the design remain stable?

What happened to cause your violent crash at speed.  Also...quite glad as I'm sure others are that you were able to walk away from your crash.  I understand why you are a proponent of design survivability.  I appreciate your concerns.  Thanks... Terry.

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #231 on: September 27, 2019, 07:14:53 PM »
Here is the redesigned intake scoop.  I wonder at what mph aero compression will overpower intake vacuum?
« Last Edit: September 27, 2019, 07:22:03 PM by Simspeed »

Offline thefrenchowl

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Re: Simspeed UWD LSR Design Project
« Reply #232 on: September 28, 2019, 05:11:34 AM »
Hi Terry,

You stated at the start that 7 rotors capacity was 4.5 litres, so I assume 8 rotors is about 5.14 litres?
Since these are Wankel engines, is that their "geometric" capacity or their "burn" capacity which, since 3 burns occur per rev, would be triple that?

Never used nitrous in me life... Since ""more"" is ""better"", where is the max quantity of liquid nitrous you can inject in a manifold before its gas expansion is too much for the rotors to accept and it reverses the flow in the manifold, preventing fresh air coming in? IE you cannot pressurize the inlet track above AP since it communicates freely with AP.

IE, would it be best to partially (if you need more nitrogen than the nitrous can give?) close the inlet manifolds upstream of the nitrous injection point as soon as you press the nitrous switch and regulate engine speed via plus/minus timing of the nitrous injection/methanol solenoid valves to get a supercharger/turbo effect?

IE, do you really need a big air scoop sticking in the wind?

I calculate the air speed through your duct entry (assumed 1 foot x 1/3rd of a foot as shown above) at 50mph at 8000rpm (approx 41m3 of air per mn) for 1 burn per rev and at 150mph for 3 burns per rev (approx 123 m3/mn of air)...

So you will get an aerodynamic disturbance around your duct entry above these speeds, whichever is right...

Patrick
« Last Edit: September 28, 2019, 05:13:26 AM by thefrenchowl »
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Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #233 on: September 28, 2019, 04:47:38 PM »
Hi Terry,

You stated at the start that 7 rotors capacity was 4.5 litres, so I assume 8 rotors is about 5.14 litres?
Since these are Wankel engines, is that their "geometric" capacity or their "burn" capacity which, since 3 burns occur per rev, would be triple that?

Never used nitrous in me life... Since ""more"" is ""better"", where is the max quantity of liquid nitrous you can inject in a manifold before its gas expansion is too much for the rotors to accept and it reverses the flow in the manifold, preventing fresh air coming in? IE you cannot pressurize the inlet track above AP since it communicates freely with AP.

IE, would it be best to partially (if you need more nitrogen than the nitrous can give?) close the inlet manifolds upstream of the nitrous injection point as soon as you press the nitrous switch and regulate engine speed via plus/minus timing of the nitrous injection/methanol solenoid valves to get a supercharger/turbo effect?

IE, do you really need a big air scoop sticking in the wind?

I calculate the air speed through your duct entry (assumed 1 foot x 1/3rd of a foot as shown above) at 50mph at 8000rpm (approx 41m3 of air per mn) for 1 burn per rev and at 150mph for 3 burns per rev (approx 123 m3/mn of air)...

So you will get an aerodynamic disturbance around your duct entry above these speeds, whichever is right...

Patrick
Hi Patrick,

Mazda rates it's two rotor engines at 1.3 liters.  So 1.3/2 = .65 *8 = 5.2 liters.  I may have also misquoted 5.14 previously.    Each rotor does produce 3 power strokes per rotor rev, but, they run on an eccentric output shaft which turns 3 times faster.  That means each rotor produces one complete power stroke per output shaft (crankshaft) rotation. 

A power stroke for a single rotor covers 90 degrees of rotor rotation which covers 270 degrees of crank rotation (90 x 3 = 270), where a single piston power stroke is 90 degrees (180 / 2 crankshaft rotations). So, where a V8 fires 4 times per crank rotation (4 * 90 = 360 total degrees combined power stroke), an 8 rotor engine fires 8 times for each rotor face that completes a full power stroke (8 x 270 = 2160 total degrees), AND, 8 times for each second face that completes 90 degrees of power stroke for each crankshaft rotation (360 - 270 = 90).  Because each of the 3 faces of a single rotor fire sequentially throughout the 360 degree "rotor" rotation cycle, when we convert rotor rotation to crank rotation we see 90 degrees of crank rotation remaining that sees 30 degrees of rotor power stroke from the next sequential face of the rotor (90 / 3 = 30).  So... 8 * 270 = 2160) + ( 8 * 90 = 720) = 2160 + 720 = 2880 total combined degrees; or 2880 / 8 = 360 degrees of crank power stroke per rotor per each crank rotation).

Although displacement per rotor face is 1/3 that of a V8 of equal total displacement (.65 / 3 = .216) vs (5.2 / 8 = .65) those 24 rotor faces (8 x 3 = 24) combined are producing 8 times more total degrees of power stroke per crank rotation than the V8.  I believe I have all that correct but with rotary engines who really knows.  :wink:

Concerning intake calculations:  Each rotor takes in .288 L of displaced air per crank rotation (.216 L @ 90 degrees (single face)) + (.072 L @ 30 degrees ( next sequential face)); totaling 2.304 L (.288 * 8) per crank rotation.  Whereas each piston of the V8 takes in .325 L of displaced air per crank rotation (.65 / 2) or 1/2 of the 4 stroke two crank rotation cycle totaling 2.6 L (.325 * 8) per crank rotation. So, we're looking at 11.5% less displaced air intake per crank rotation than a V8.  Does this make sense on the face of it?  We would have to say volumetric efficiency of a normally aspirated rotary engine is better than a 4 stroke NA piston engine given the numbers above.   

Nitrous as I understand the principle is injected via bottle pressure which instantly expands to AP in an NA environment.  The power benefit comes from the introduction of extra oxygen molecules relative to that available in natural air. Combustion heat releases oxygen from the nitrogen/oxygen compound which in turn combines with the fuel to create additional power by volume.  You may be right that less natural air is needed via the intake scoop using NOs than without, but by total volume of air consumed by any internal combustion engine over the course of a run, I don't think you can carry enough NOs on board to cover the total volume of air needed given current pressurization systems used for this application.  Also, intake scoops offer a degree of aerodynamic compression of air stacking up inside the scoop chamber depending on the speed of air contacting the scoop intake opening, size of the opening, size of the interior chamber, and volumetric efficiency of the engine at a given rpm relative to ground speed. 

I do agree that we will see an aero disturbance around the scoop opening depending on the degree of compression stacking withing the scoop.  Thanks again for your input Patrick.  Terry

Offline 7800ebs

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Re: Simspeed UWD LSR Design Project
« Reply #234 on: September 28, 2019, 11:19:37 PM »
 I've incorporated aluminum wheel/tires here as a preventive measure to eliminate rubber tire issues.  Also, the use of FWD only is designed to eliminate RWD induced yaw concerns in control of the car at speed. 

So what is the cf of aluminum on Salt?      cf / traction is what makes us go... and when all wheels are spinning.. what then?  Have you ever driven on salt with an aluminum wheel? Don Vesco did in early 90's as I recall.. you may need to review that idea.. if the hp can't be hooked up, all other design innovation dies... bob

Offline thefrenchowl

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Re: Simspeed UWD LSR Design Project
« Reply #235 on: September 29, 2019, 03:22:58 AM »
And, Bob, I seem to remember most FrontWD can't accelerate as fast as a RWD due to weight transfer rear bias during acceleration and loss of front traction unless there's a few tons of bricks on top of them, never mind how good the front rubber is...!!!

The Turbinator is 4 wheel drive...

NOVIs, MILLERs and others FrontWD at Indy spring to mind...

Patrick
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Offline 7800ebs

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Re: Simspeed UWD LSR Design Project
« Reply #236 on: September 29, 2019, 12:41:03 PM »
I don't think there is as much weight transfer as you may think on a long wheelbase car at Bonneville. To have any weight transfer, you must have something to provide an acceration force. It is called traction.. bob

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #237 on: September 29, 2019, 01:13:27 PM »
I've incorporated aluminum wheel/tires here as a preventive measure to eliminate rubber tire issues.  Also, the use of FWD only is designed to eliminate RWD induced yaw concerns in control of the car at speed. 

So what is the cf of aluminum on Salt?      cf / traction is what makes us go... and when all wheels are spinning.. what then?  Have you ever driven on salt with an aluminum wheel? Don Vesco did in early 90's as I recall.. you may need to review that idea.. if the hp can't be hooked up, all other design innovation dies... bob
Hi Bob,
I've stated previously that our plan for traction is to apply the SlipNOT (tm) #2 Metal Sputter Coat Traction coating on the contact surface of the aluminum wheels. https://www.slipnot.com/what-is-slipnot/.  Based on what I understand of the process the sputter coating material (aluminum) is molecularly bonded to the wheel as a stippled texture that produces traction against the track surface (salt).  The coating can be applied in various thickness and texture for best results.  I would use the coating on all wheels fore and aft.  Thanks... Terry.   

Offline Simspeed

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Re: Simspeed UWD LSR Design Project
« Reply #238 on: September 29, 2019, 01:25:46 PM »
I don't think there is as much weight transfer as you may think on a long wheelbase car at Bonneville. To have any weight transfer, you must have something to provide an acceration force. It is called traction.. bob
Traction is elusive on the salt as I understand what others have reported.  I don't see the benefit of running a car of this type on anything but the best track conditions.  Bonneville may no longer be the track of choice for unlimited wheel driven vehicles so there will have to be alternative course considerations for record attempts.

SlipNOT coated wheels would have to be tested on the salt to determine their viability for this design effort.  I would propose to supply an existing team with coated wheels for testing before committing funding for this project.  The results of those tests would help to determine whether or not 2 or 4 drive wheels should be incorporated into the Simspeed design.  Thanks... Terry.

Offline 7800ebs

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Re: Simspeed UWD LSR Design Project
« Reply #239 on: September 29, 2019, 02:09:29 PM »
Soooo..  machine some aluminum with radius desired. Get a fish scale, add 100 lbs to said aluminum.  Pull it across the salt .  Read scale.  If it takes 20 lbs to move it across salt.  Cf is .2..  address issues .. set record's... Become hero.. this stuff is easy... Bob