Spoon rotors - progress report
Registered User
Joined: Oct 2000
Posts: 389
Likes: 0
From: Middletown
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by CoralDoc:
Wow Luis! That scale says your car weighs 2500kg
. That's really light!
[/quote]
Actually, thats really HEAVY !!!
about 5500 lbs.
Wow Luis! That scale says your car weighs 2500kg
. That's really light![/quote]
Actually, thats really HEAVY !!!
about 5500 lbs.
Registered User
Joined: Oct 2000
Posts: 1,116
Likes: 0
From: palo alto
after reading all the above,i'll have to side with the elegance/symmetry side....i think we're radiating heat here..with all the turbulance surrounding the inner aspect of the wheel in a dynamic state i really don't think you will be moving any air predictably...also i remember a technical article on porsche 917 wheel mounted turbine fans to cool the brakes...porsche discovered that although they worked well in the calculations,in a dynamic state[on a car at speed]that they didn't move an effective amount of air onto the brakes until the car reached 150 mph!!!!![and trust me,porsche would know for sure]so most of the "turbine" wheel designs we see are pretty much ornamental......as i think directional rotor vanes are.... just an opinion....
Registered User
Joined: Oct 2000
Posts: 416
Likes: 0
From: Ashtabula
Rotors should be different left to right side of car that is why curved cooling fins are used . You can check on AP racing site you will find left and right rotors. You can use temperture paint to check rotor temperature you can buy it from 400 to 1700 degrees in 50 degree increments.
brad
brad
Joined: Oct 2000
Posts: 9,210
Likes: 7
From: WA
Originally posted by Luis:
and where would I buy it?
and where would I buy it?
http://www.rebcoracing.com/recirculator.html
Registered User
Joined: Oct 2000
Posts: 741
Likes: 0
I was told in the "cracked rotors" thread that the board consensus was that the Spoon curved vane rotors were fine. That the fact that there were either two lefts or two rights did not matter. The stock rotors are not handed, the vanes are straight and they flow the same amount of air if spun clockwise or counterclockwise. If you spin a curved vane rotor the wrong way, it will not achieve the same induced airflow as when it is spun the correct way.
I cannot find this "Spoon is fine" consensus above. In fact, it looks like there are many posts stating the other POV. Here's an URL for an AP Racing Brake picture of curved vane rotor orientation. AP is one of the top, top real racing brake compaines in the world. It's easy to see that curved vane rotors are in fact handed.
http://www.apracing.com/car/brakedisc/iden...ntification.htm
When vented rotors spin, they centrifuge the air through the vents. The air goes in the eye or throat at the back of the disc and then exits the disc OD. If you look over the pic in the URL above and imagine the disc spinning you will see that in one direction the air can flow better than the other.
I am very unimpressed with the Sppon rotor and advice others to avoid it unless and until they correct this silly cost saving measure. Still, they are likely to work okay in street type driving conditions. Expect some guffaws if someone in-the-know sees your Spoon rotors with one side installed "backwards". To me, this is a hilarious example of what the euro car gang calls "Rice".
Stan
[This message has been edited by E30M3 (edited November 28, 2000).]
I cannot find this "Spoon is fine" consensus above. In fact, it looks like there are many posts stating the other POV. Here's an URL for an AP Racing Brake picture of curved vane rotor orientation. AP is one of the top, top real racing brake compaines in the world. It's easy to see that curved vane rotors are in fact handed.
http://www.apracing.com/car/brakedisc/iden...ntification.htm
When vented rotors spin, they centrifuge the air through the vents. The air goes in the eye or throat at the back of the disc and then exits the disc OD. If you look over the pic in the URL above and imagine the disc spinning you will see that in one direction the air can flow better than the other.
I am very unimpressed with the Sppon rotor and advice others to avoid it unless and until they correct this silly cost saving measure. Still, they are likely to work okay in street type driving conditions. Expect some guffaws if someone in-the-know sees your Spoon rotors with one side installed "backwards". To me, this is a hilarious example of what the euro car gang calls "Rice".
Stan
[This message has been edited by E30M3 (edited November 28, 2000).]
Registered User
Joined: Oct 2000
Posts: 167
Likes: 0
Luis,
You should put this thing to rest for the benefit of all the members. E30M3 does have some valid points.
Test your rotors with a pyrometer, infrared or brake probe attachments. Test it under extreme conditions, induce fade. I fear that if cooling is uneven under severe conditions you will have uneven braking, that may cause major problems. Or put to in another way more fade on the left as to the right or is that the otherway around.
If there is no difference with temperature or performance. Then we should all buy straight vane rotors because curve vanes don't work and are heavier.
You should put this thing to rest for the benefit of all the members. E30M3 does have some valid points.
Test your rotors with a pyrometer, infrared or brake probe attachments. Test it under extreme conditions, induce fade. I fear that if cooling is uneven under severe conditions you will have uneven braking, that may cause major problems. Or put to in another way more fade on the left as to the right or is that the otherway around.
If there is no difference with temperature or performance. Then we should all buy straight vane rotors because curve vanes don't work and are heavier.
Registered User
Joined: Oct 2000
Posts: 741
Likes: 0
<<It seems to me that the centrifugal action you describe will work just fine regardless of the orientation of the vanes. Since the rotor is positioned in an area protected from the airflow, I have to believe the orientation is irrelevant and that most of this discussion is about esthetics. >>
No, let me try to explain and give an example.
Remember that the rotors act as air punps. How about a real world experiment? I did this one last night.
I decided to check out three vented rotors I had on hand. One straight vane early BMW M5 (e34). One curved vane Indy car disc. And one curved vane Nascar disc which had been adapted to a BMW endurance racer.
One at a time I did the following. I mounted a rotor on my lathe. Then I spun them at about 450 RPM, which would be around 30 MPH on a car. I placed a blow torch with a full tank such that the flame hit one of the disc rubbing surfaces. Then I used my infrared thermometer to read the disc temp. The heat was used only when the disc was turning so that the heat input is spread around the disc side.
I found that the straight vaned disc cooled equally well when turned in either direction. As expected. The subjective hand near the OD test could detect no difference in sound or feel to the airflow when spun either way. A plastic bag deflected the same amount from the air flow regadless of spin direction. No surprises.
I found that both of the curved vane discs "liked" to be turned in a particular direction. Again, as expected.
Typically when run in the preferred direction the temp stabilized at about 105 degrees F in the 65 degeee workshop in my basement. When spun the other way the disc stabilized at about 122-123 F. Temps would stabilize in much less than a minute (didn't time this) and then hold rock steady. Stop the lathe and turn the disc the other way and the temps drop back to 105 again. Reverse the spin and temps climb. Very repeatable and within about a degree each and every time.
The subjective sound and feel of the air exiting the curved vane disc changes depending upon the direction the disc is turned, for the curved vane discs. There might be about twice the airflow, but this is hard to say for sure since the test is subjective and turbulence makes a difference and in any event the main idea is cooling. It's very noticeable in any case. (Turbulence affects cooling, it's not just simple cfm.)
I expect the difference in cooling to increase with increasing heat energy input and disc RPM. A 30 MPH test is a very low speed for a disc brake. Centrifugal pumps tend to increase their flow with a squared relationship to increased speed. Like a centrifugal supercharger or a water pump. So ignoring other factors, at RPM for 60 MPH we would anticipate around 4 times the air flow induced at 30 MPH. But there are other factors too. This means that the differences in pumping (and cooling) would become more pronounced with more heat energy and disc RPM.
Brakes on a given end of a car are intended to be operated at the same temps so that braking action is even and safe.
My conclusion is that curved vane rotors DO need to be turned in the proper direction to cool properly and to their full potential. No matter what you do with the spoons, one side will turn in it's "preferrred" direction and one won't. I did not test the spoon discs, but unless they are secretly preparing for a Nobel Prize in heat transfer and fluid flow they will behave differently when spun in different directions too. I think that the reason why there is only one Spoon disc instead of a left and right version is that they didn't want to pay for the tooling OR if there are left and right versions, that some are being shipped as two rights or two lefts. Every single curved vane disc I have seen on OEM applications is handed. Every single curved vane racing disc I see in my various racing catalogs is handed. But NOT the Spoons apparently.
I do not think this is a subjective esthetic issue. And apparently these are not cheap discs. Caveat Emptor.
<<Certainly an increase in cooling could be accomplished by directing an airflow to the center of the rotor as we discussed in another >>
If you want the Spoons to run at the same temp, which is highly desireable, you would need to duct air to each side of the car differently. This may even vary with speed so you might have to design the cooling effect for your desired speed range.
Or you could just use properly designed brake discs in the first place.
Stan
[This message has been edited by E30M3 (edited November 28, 2000).]
[This message has been edited by E30M3 (edited November 28, 2000).]
No, let me try to explain and give an example.
Remember that the rotors act as air punps. How about a real world experiment? I did this one last night.
I decided to check out three vented rotors I had on hand. One straight vane early BMW M5 (e34). One curved vane Indy car disc. And one curved vane Nascar disc which had been adapted to a BMW endurance racer.
One at a time I did the following. I mounted a rotor on my lathe. Then I spun them at about 450 RPM, which would be around 30 MPH on a car. I placed a blow torch with a full tank such that the flame hit one of the disc rubbing surfaces. Then I used my infrared thermometer to read the disc temp. The heat was used only when the disc was turning so that the heat input is spread around the disc side.
I found that the straight vaned disc cooled equally well when turned in either direction. As expected. The subjective hand near the OD test could detect no difference in sound or feel to the airflow when spun either way. A plastic bag deflected the same amount from the air flow regadless of spin direction. No surprises.
I found that both of the curved vane discs "liked" to be turned in a particular direction. Again, as expected.
Typically when run in the preferred direction the temp stabilized at about 105 degrees F in the 65 degeee workshop in my basement. When spun the other way the disc stabilized at about 122-123 F. Temps would stabilize in much less than a minute (didn't time this) and then hold rock steady. Stop the lathe and turn the disc the other way and the temps drop back to 105 again. Reverse the spin and temps climb. Very repeatable and within about a degree each and every time.
The subjective sound and feel of the air exiting the curved vane disc changes depending upon the direction the disc is turned, for the curved vane discs. There might be about twice the airflow, but this is hard to say for sure since the test is subjective and turbulence makes a difference and in any event the main idea is cooling. It's very noticeable in any case. (Turbulence affects cooling, it's not just simple cfm.)
I expect the difference in cooling to increase with increasing heat energy input and disc RPM. A 30 MPH test is a very low speed for a disc brake. Centrifugal pumps tend to increase their flow with a squared relationship to increased speed. Like a centrifugal supercharger or a water pump. So ignoring other factors, at RPM for 60 MPH we would anticipate around 4 times the air flow induced at 30 MPH. But there are other factors too. This means that the differences in pumping (and cooling) would become more pronounced with more heat energy and disc RPM.
Brakes on a given end of a car are intended to be operated at the same temps so that braking action is even and safe.
My conclusion is that curved vane rotors DO need to be turned in the proper direction to cool properly and to their full potential. No matter what you do with the spoons, one side will turn in it's "preferrred" direction and one won't. I did not test the spoon discs, but unless they are secretly preparing for a Nobel Prize in heat transfer and fluid flow they will behave differently when spun in different directions too. I think that the reason why there is only one Spoon disc instead of a left and right version is that they didn't want to pay for the tooling OR if there are left and right versions, that some are being shipped as two rights or two lefts. Every single curved vane disc I have seen on OEM applications is handed. Every single curved vane racing disc I see in my various racing catalogs is handed. But NOT the Spoons apparently.
I do not think this is a subjective esthetic issue. And apparently these are not cheap discs. Caveat Emptor.
<<Certainly an increase in cooling could be accomplished by directing an airflow to the center of the rotor as we discussed in another >>
If you want the Spoons to run at the same temp, which is highly desireable, you would need to duct air to each side of the car differently. This may even vary with speed so you might have to design the cooling effect for your desired speed range.
Or you could just use properly designed brake discs in the first place.
Stan
[This message has been edited by E30M3 (edited November 28, 2000).]
[This message has been edited by E30M3 (edited November 28, 2000).]
