Carl Beck
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Posts posted by Carl Beck
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What is the PayPal Fee?
thanks,
Carl
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Has anyone been following the Dodge Ram SRT-10? 500HP Viper engine.. 150MPH top end and sub 5.0 second 0-60mph? At any rate some interesting "aero" devices on this truck - developed via CFD Modeling/Visualization plus wind tunnel and on track testing.
See: http://www.dodge.com/srt-10/
Note the size difference between the Ram SRT-10 and the Ram Daytona rear aero devices..
Then an interesting article related to Daimler/Chrysler - Dodge and aero design efforts/processes..
http://www.creativemac.com/articles/viewarticle.jsp?id=25605
FWIW,
Carl B.
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Hi PrOxLaMuS© / 1_tuff-z (everyone):
Hi Guys - thanks for the welcome. I've been a lurker here for a long time - ever since pparaska started harassing me and I like the way jmortensen administers/moderates.... just been too busy with a hundred other things to get involved in any of the very interesting threads. The subject of Z Car aerodynamics however sucked me in this time...
If you don't have a copy of the 74 Car & Driver article, e-mail me and I'll let you read my digital back-up. It will be interesting to see how the HybridZ wind tunnel results match up... or not...
Carl
e-mail: beck@becksystems.com
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I think that's contrary to the popular belief, OTM, but we may find out for sure soon.
Hi John / OTM (everyone):
It is certainly contrary to what Car & Driver found in their tests in 74.
Stock:
140 lbs of Lift on front wheels @ 70mph
20 lbs of Lift on the rear wheels @70 mph
BRE Front Spook canceled 105 lbs of Lift and increased gas mileage by 0.4 mpg
BRE Street Spook (no brake ducts) canceled 115 lbs of Lift
BRE Rear Spoiler added 75 lbs. of down force @ 70 mph and 0.2mpg
C & D custom 7" rear spoiler (at 50 degrees from horizontal)
Added 160 lbs of down-force to the rear but off loaded an additional 20 lbs from the front. It also hurt gas mileage by 0.6 mpg.
FWIW,
Carl B.
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I've decided to cut the floorboards off myself, buy a replacement kit, and have someone do the welding.
Hi Alri:
I would recommend finding someone to weld them in FIRST.
If you show up at the typical body shop with no floorboards at least one of two things will most likely result. 1. The guy at the body shop will not have had the opportunity to decide for himself, where the best place to cut them out would be (so he would have access to weld). He'll also not have a good concept of how they should look when he'd done. 2. Knowing that you are now stuck with no floorboards - and MUST have them done, his price can go up..
If your going to cut them out yourself - work out a deal with the person that's going to weld them back in BEFORE you start cutting.
Here is a good article on doing the job - it will at least give you some idea of how it goes..
http://zhome.com/Classic/240ZFloorboards/ChrisFloorboards.htm
BTW - looking at the picture of your Z - you're just North of me..
FWIW,
Carl B.
Carl Beck
Clearwater, FL USA
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....snipped....
The door has a little round cylinder with two 'bumps' on it, about 90* apart. The lower one (pointing towards the ground) hits first on the body latch, causing the cylinder to rotate and pushing the second 'bump' around/into the latch on the body. Seams to me that the past 30 years of closing the door had worn down the metal so much that the second 'bump' wasn't rolling into it's proper spot, as it was hitting the 'point' where the cutout starts. I simply ground back the little radius with a dremel and WOW! The doors close like a new car! I don't know if this is any help to anyone, but I thought it was worth posting anyway.. I'll try to get a pic to describe what I've done..
Hi datsunlover:
Just an interesting side note:
That first "bump" on the "latch" when new (at least on the 72 240-Z) - had a nylon sleeve on it (kind of a horse shoe shape). Over time, they either wear out or get brittle with age - crack and fall off.
At one point I attempted to find a plastics shop - that could reproduce the nylon sleeve ... but the cost of the molds needed for injection molding were just too high. In the process of attempting to remove that nylon sleeve from the one good latch I had, we managed to break the original sleeve.
After that nylon bumper falls off - then the metal to metal contact between the latch and the catch start to take effect. At any rate, your solution should work fine...
FWIW,
Carl B.
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...snipped.....
BTW, I think I might be wrong about the outside of the vortex travelling fastest. But I think it might be the inside. Anyone confirm? I could just go look it up, but my chair is way too cumfy.
Dave
HI Dave:
Always ask yourself - "where is the energy source or force". Most of the time that will help you answer your question.
Be it a wing tip or hot air - it's at the center, and therefore the highest speed winds...
FWIW,
Carl B.
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Hi Carl. Welcome. I have to take issue with, I don't think that is right.
The turbulence in back of the car is not high pressure turbulence. It's LOW pressure turbulence. The reason the exhaust gets into the cabin is because it is SUCKED in, not PUSHED in. Flow separation, the cause of the turbulence, creates low pressure.
Cracking the windows creates suction inside the cabin via the Bernoulli effect, so now you have suction inside the cabin and vacuum at the rear of the car, and that REALLY sucks the exhaust into the cabin. Any little hole allows air back in, and since that air is turbulating all the exhaust, that's what gets sucked into the cabin.
I do agree that opening the fresh air vents increases the cabin pressure, and that works against the vacuum which is trying to force air into the holes in the rear of the car. That is why positive pressure works.
I am not an expert, I only know what I've read here and elsewhere, but the bottom line for me is that you need some sort of deflector or barrier to create positive pressure, like air hitting the radiator, the windshield, or a spoiler. Just pulling the car through the air creates a negative pressure behind. Why can't you run fast in a swimming pool? Because when you try to move you create a huge turbulent vacuum behind you, and that tries to suck you backwards. Same thing with a car through the air, just a less viscous medium. If you created positive pressure behind, then you'd actually go faster for having it there. We worry about drag, but not about "push".
Hi Jon:
Thanks for the welcome and the response. This is a good discussion to have, before the wind tunnel is cranked up, and indeed I could be conceptualizing all this in the wrong manor.
How I understood it :(which could very well be the wrong way of thinking about it)
"It" being the Kamm back design and its effects:
I believe that Dr. Kamm did indeed worry about both Drag and "push".
Yes, the tumbling/spinning air flow - ie. rotating in a horizontal circle, is moving at a higher speed, than the air flow coming off the car and transiting over the top of that circulation. The speed of the circulating air also gets higher as it approaches the center of circulation - and thus the center of that rotation is the lowest pressure area within that circulation. The center of a Hurricane is its lowest pressure area.
But when Hurricanes come ashore - the circulating bands blow with very high wind speeds.. and thus exert very high pressures on anything they encounter (a mass of air molecules moving at very high speed). The high pressure area at the rear of the car in this case, is not the center of that circulation (low pressure area), but rather is at the point where the higher speed winds of that spinning circulation - strike/collide with (push against) the rear of the car. Just as the air striking the front of the car creates high pressure.
As I understood it (that qualifier again) - Dr. Kamm wanted that center of circulation positioned at a point behind the car, to not only take advantage of its ability to effectively reduce separation turbulence (support a smoother transition of the air flow off the back of the car - much the same as extending the body itself back to a pointed end), but to also take advantage of the energy in that spinning low pressure area - and apply it to the back of the car - yes to gain a little offsetting "push".
Adding the Nissan/BRE rear spoiler - effectively moves the center of circulation rearward away from the back of the car, and thus reduces or eliminates the high speed winds in the circulation from hitting the back of the car.
I think "suction" is a term that describes an effect, I don't see how it can be a cause. Maybe if we're lucky we'll get a physics major upset enough to jump in here, as we mangle the subject.
At any rate - If the pressure sensors are put in the right places on this project - we should be able to see more clearly just what is happening.
FWIW,
Carl B.
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Welcome Carl!! and great info! Would you happen to know what a Supra style wing does to airflow, and does it help fumes? I've noticed that fume issues are not that bad in my car.
Hi Mike kZ
Thanks for the welcome. I know several of the people here and have been a lurker for several years as well.
No I don't know what would happen to the air flow with a Supra Style wing added. I've never seen any tests with that type of device on a Z. On first appearance, I would venture a guess that it would have to move that high pressure area at the rear of the car, farther back and perhaps a little higher.
That one would be a good "test case" for the wind tunnel. It would be especially fun to move it's mounting position up/down the slope of the rear hatch to find the best position. That being where the down-force it applies is high enough to cancel any lift at the rear wheels, without adding unwanted drag to the vehicle. Is it possible to adjust the angle of attack on that type of wing?
I can't recall, without going back to look - but I believe one method of measuring increases or decreases to aerodynamic Drag on a vehicle is a "Cost Down Test". You run the car up to 70 or 80 mph, then let it coast down to about 30 mph. Then you measure the distance it took.
Below 30 mph the effects of aerodynamic drag are minimal compared to the physical drag from the tires and drive line.
There was at one time a wing type "airfoil" made for the 240Z, but I've not seen one actually on a car for at least 25 years, nor seen one tested by anyone.
http://zhome.com/History/Images/72Broc4.jpg 240Z Airfoil
Of course the Wail Tail on the 79 280ZX-R's was most effective on the track, at offsetting Lift without adding too much Drag.
FWIW,
Carl B.
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Hi Guys,
...snipped....
Does air going into side windows need a way out? Through the hatch? Dosen't make a lot of sense, other then the hatch rising slope, decreasing helps reduce lift? Would be a quick and easy test to prop up a couple of inches or inch.
......snipped.....
David
Hi David:
As I understand it - the Kamm back design used on the First Generation Z's has the effect of forming a turbulent high pressure area at the end of the car. That high pressure area is what forces exhaust gases into the passenger cabin, when the rear of the car isn't properly sealed.
When you roll your windows down, that exhaust smell gets worse. (the opposite of what you would expect)
That is because the high speed airflow along the sides of the car create a low pressure area, that is, lower pressure than that in the cabin. So when you roll the windows down - while outside air is forced in and circulates with the passenger cabin - cabin air also actually gets sucked out the side windows. Somewhat the same effect as air flowing over the top of a chimney (heat alone doesn't push smoke up a 20' chimney - ie, Venturi effect).
Roll the windows up, and open the Z's Fresh Air Vents in the front of the car - and the exhaust smell gets better (ever so slightly)... because the forced air induction from the front of the car is now creating a slightly higher cabin pressure, but still not higher than the area behind the car...
Add a rear spoiler and the exhaust smell is greatly reduced. That is because the effect of the Kamm back's turbulent high pressure area is effectively moved farther rearward, and the exhaust gases are no longer held as tightly against the rear of the car. The pressure differential between that high pressure area behind the car and the lower pressure area within the passenger's cabin, is not as great as it was before the rear spoiler was added.
FWIW,
Carl B.
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Cygnus.. thank you for the ideas... The fact is.. that everytime i get a list together someone pops up with even more good ideas.. and the testing schedule gets updated...
It looks like we can cover all the common parts except the G-nose... it is just too valuable and too hard to mount and dismount quickly... that said.. we are still trying to decide if we are going to put a G-nose race car in the tunnel at the end of the day to just get some old school numbers... this would depend on a lot of things lining up with the sun and the moon...
We also have a splitter/underpan/rear diffuser all lined up for testing.. as well as roof mods and hood mods and a pantera deck...
The facility has the equipment to gather data on airflow through ducts, pressure at many points, much more can be interpolated later...
Hi bjhines (everyone):
I applaud your efforts and like the idea of spending a day in the wind tunnel with a 240-Z. Exactly why I like that idea, I really don't know!
The truth is, I don't know exactly what physical measurements can be taken in the wind tunnel. That is to say, I don't understand what test equipment the car would be hooked up to, nor the type of data that test equipment would report.
I'm hoping that you might be able to give me some specifics related to the actual test equipment hooked to the car, that would measure the physical effects of the aerodynamics being applied - as opposed to the intrinsic discussion of the aerodynamics themselves.
I noticed that Cygnus - suggested "measuring" lift/down-force at speed. Is that something that is actually measured in a wind tunnel?
For the tests conducted by Car & Driver in 73 as I recall - they hooked a car up to a device that measured body deflection from standard ground clearance as the car was driven at speed - and then computed the amount of lift or down force being applied to the front or rear of the car. Is a physical device like that used in a wind tunnel?
He also suggested plotting drag, which would imply that it to was being measured, as well as identifying pressure points at key locations vs speed. Is there now some test equipment that actually measures the drag created by an object in a wind tunnel? (I was under the impression that drag was calculated from either frontal area or total surface area) Do they have 3D scanners in the wind tunnels now to provide that data? Or perhaps in a stagging area ahead of the wind tunnel?
In your reply above - you seem to indicate that data related to airflow is really all that is "measured" (for lack of a better term on my part)... and perhaps high or low relative pressure points could be measured...
Any help you can provide in understanding exactly or specifically what is going to be measured or what is not actually measured, but rather computed or estimated in this project would be greatly appreciated by me.
It's not so much a matter of knowing what aerodynamic devices work, as it is a matter of knowing which one's have a positive effect great enough to justify the cost of applying them.
thanks,
Carl
Carl Beck
Clearwater, FL USA
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Hi Grumpyvette
Very nice garage indeed...
A few words about Ben Person Lifts...
In another life, back In 1975 I owned/operated a Muffler Shop - had a new Ben Person Pipe Bender and two 4 Post Lifts. After I actually learned something about the business... I realized that I should have bought a Huth Pipe Bender... and I found that Ben Person was a young company at that point.
One day I was letting a car down, as I watched a fine young girl walk by outside... distracted to say the least... My attention was returned to the car when I heard it sliding sideways and threatening to fall off the lift!! YEA GAD !!!
One of the "stops" had failed to retract on the Left Front Post...so that corner was still at its uppermost position... in the mean time the other three corners were allowed to come down... The car was sliding backward on the ramps, as the Right Side was now about four feet lower than the left front...
As the car slide - the lift made a horrible noise... twisting posts, drive on ramps sliding across the cross braces... I jumped back away from the lift.... as the Customer exclaimed "Watch My CAR!!"...
Everything was at a "ALL STOP"... and I stood there wondering how I was ever going to get this customers car safely back on the ground...
After I calmed down... I called Ben Person in Arkansas. They put a "technician" on-line... I explained what had happened..... cute little ass walking by and all.... and he said; "no problem, just go out and push the UP button and raise the car back up... then make sure all the STOPS are up and let the car down".
I told him I was not intending to get too close to that mess, because I was afraid that it would either fall on me, or go through the side of the building. He said; "then take a broom handle, stand back and push the UP button... I will give you my word that if anything happens, other than the car returning to the full up position - then coming down properly - Ben Person and Company will pay all damages". He added the fact that he was the lead engineer there - and that lift had 4 times the strength required in every aspect of its design build. He also said he was one of the Principle Owners of the company..
So I took a boom handle - stood back - and pushed the UP button. Among much loud creaking, screeching and popping... the car did in fact return to the lift's full up position... and all four posts returned to their former unbent state. I put the STOPS up and let the lift and car down...
The Customer, now some three hours into this venture... exclaimed "I'll be damned!"... "if I hadn't been here to see that - I wouldn't have believed it." Needless to say, there was no charge for the work on his car... Two days later the man from Ben Person was in the shop to inspect the lift... and find out why one stop had failed to retract. He OK'd the condition of the lift ... and three months later a service team from Ben Person was in the shop installing a new mechanism for raising all the STOPS....
At that point I found out that I had two of the first twenty 4 Post Lifts they had designed and built for the Muffler Shop industry...
Bottom line - don't buy a lift from anyone that hasn't been in business for at least 20 years. Don't buy a lift from anyone that builds their lifts outside the USA (to avoid product liability suites)... Don't PAY for anything purchased from ANYONE until it is delivered to you (the exception is when you are dealing directly with the factory, that has been in business for at least 20 years). Way too much FRAUD with retailers and re-sellers or "factory rep.'s".... If they don't have the working capital to order and deliver your lift - prior to payment - RUN...
FWIW,
Carl
Carl Beck
Mad Hatter Muffler (lost a lot of money on that one...)
Clearwater, FL USA
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Aerodynamic Testing Candidates
in Body Kits & Paint
Posted
Hi BJ:
Doesn't the use of a 280Z rule out the testing of the BRE Front Spook? The lower front finishers on the 280Z are lower and rounded to allow more air flow into the larger radiators on the 280Z's.. and the BRE Spooks were made to fit the lower finishers on the 240-Z's... The BRE Spook was the most effective at offsetting front end lift - at least in the C & D Tests...
FWIW,
Carl B.