Hi I am at the point where i need to pickup a electric fan thermostatic controller
i know Derale ,permacool,and flexalite make them anyone have any of tyhese installed to controll their electric fans and do they work thks Bob
67ss396
underconstruction (forever it seems)

I had a Robertshaw adjustable unit on a V8 Vega several years ago. It came with a fan I bought at a speed shop. I don't remember the brand name of the fan, but for some reason I remember the thermostatic controller. It was very nice.

Currently I just run a blue rocker switch. I like being able to turn it on and off manually.

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My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

[This message has been edited by cjlandry (edited 02-05-2002).]

The perma-cool one sucks big time. AT least the one that "zip ties" to either the radiator or the hose does. complete trash.

The ones that actually insert into the radiator hose do quite well. I think they are adjustable also. They do the job, don't know about longevity/presicion though.

The one I run is a (damn forgot the name). I think maybe Be-cool makes it?!?! NO, it's some kinda switch/harness place. Anywho, it screw into your intake (or in my case the water neck has a 3/4" tapped hole) and has special on/off switching. It will come on at 205* and shut off at 185*. My setup has a 180 stat. I did this because the Mark VIII fan I use will cool the motor very quickly, and this with a common sensor makes for a lot of ON/OFF switching of a big fan... not good. http://www.chevelles.com/forum/smile.gif

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71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
BEST 60': 1.85 w/street tires.
BEST 1/4: 12.5 with 1.89 sixty foot (street tires)
BEST MPH: 109mph

Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
Video of me staging (smoke of course) (http://www.auburn.edu/~ledfojw/vids/mike_chevelle_burnout.avi)

Mike,
with your qualifications, you should be designing and building your own fan controller http://www.chevelles.com/forum/wink.gif

BTW, haven't forgot about the circuit-of-the-month, just haven't had time to build the webpages.

Thanks for the feed back on the fan controllers now i have a decision to make. nice ride Mike!
-----------

Bob underconstruction

<BLOCKQUOTE>quote:</font><HR>Originally posted by Coppertop:
Mike,
with your qualifications, you should be designing and building your own fan controller http://www.chevelles.com/forum/wink.gif
<HR></BLOCKQUOTE>

Just wait untill I find a Pulse width modulater that can handle 40 Amps. Then My fan speed will be porportional to Engine temperature. http://www.chevelles.com/forum/cool.gif Some industrial company has to make something already together ina little black box. This-a-way other TC people with ihg speed fans can make use of it.



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71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
BEST 60': 1.85 w/street tires.
BEST 1/4: 12.5 with 1.89 sixty foot (street tires)
BEST MPH: 109mph

Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
Video of me staging (smoke of course) (http://www.auburn.edu/~ledfojw/vids/mike_chevelle_burnout.avi)

I have a couple of spare PWM's at work in red fiberglass boxes, but they might be a bit large to fit in your engine compartment. http://www.chevelles.com/forum/wink.gif

------------------
My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

[This message has been edited by cjlandry (edited 02-05-2002).]

Mike. we need to bounce some ideas back and forth on this. We should try building a PWM controller for the fan. I think I should fire up Orcad and draw up a circuit I've been thinking about and see what you think.

The PWM generator is basically a sawtooth waveform fed into one comparator (op-amp) input with the temp feedback into the other input. Then, hook the ouput up to a big FET on a heatsink. Well, maybe a few FET's in parallel on a heatsink.

I'm sure a stock guage or EFI sender could be used for the temperature sensing. That way, it mounts right into the intake.

I'm not running an electric fan right now but I may try to in the future. Right now, the EFI, disk conversion and 700R4 are keeping me busy.

Peter

Peter. what ever I can do just let me know. One of my projects in college was a motor controller with feedback and PID control usage. It was a smaller motor and used an H-bridge IC for the current sinking. The computer did the PWM signal.

They make PWM ICs that very the duty cycle. (It's a square wave I believe, better for controlling a DC motor takes a while for the current in an inductor to change and the sawtooth will prevent full on power I think). Anywho the duty cycle is controlled by the a voltage 0-5V. Might have to toss a resister-devider between the Elec sending unit (0-12v?) and the IC.

The problem is "post signal creation" the whole: Find an FET that can sink 40Amps and how fast can it do this i.e. how long will the waveform period need to be... Oh yeah, it's ambient temperature will be ~150ish degrees. http://www.chevelles.com/forum/smile.gif Maybe a comparator Ic will have the propper number of FET's in parrallel tha we need?

Does Orcad have the Mark VII fan in it's library of 5 million parts?? http://www.chevelles.com/forum/wink.gif

CJ What company makes that red box you talked about?

------------------
71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
BEST 60': 1.85 w/street tires.
BEST 1/4: 12.5 with 1.89 sixty foot (street tires)
BEST MPH: 109mph

Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
Video of me staging (smoke of course) (http://www.auburn.edu/~ledfojw/vids/mike_chevelle_burnout.avi)

[This message has been edited by BB_Mike (edited 02-06-2002).]

Found some neat stuff.
http://blink.pwrx.com/pwrx/docs/cm1000ha24h.pdf
This guy has a single IGBT that pretty much rocks. Never heard of it, but I guess it's like a MOSFET on crack.

We don't have to worry about the H-bridge thing. Only spinning one way. http://www.chevelles.com/forum/smile.gif
http://www.irf.com/technical-info/papers.html
this has good info on the two and what we might be using them for.

I think Mike's desribing a kit from Painless. It's just on-off, not variable.

Geezads Mike, 1000A IGBT? At any rate, I deal with PowerX and IR at work. We buy SCR's directly from them in bulk. That's why I didn't seem too concerned about the current required. Typically, IGBT's want 15V to turn on and -8V to turn off so they're harder to apply here. I really haven't been involved in the application of IGBT's before so I'm not really positive on their exact operation.

The sawtooth just feeds the comparator. When the sawtooth is &gt; than the other input (temperature signal) the output is on, when &lt; it is off. In other words, if the temperature input is 0 then the ouput is full on. If it is hi then it is off. In between, it is a varying duty squarewave.

It only requires a single transistor since it's not reversing. What about using IR's HEXFET device? I think they're enough. I could possibly even get samples.
http://www.irf.com/product-info/datasheets/data/irl1404.pdf

Peter

Well damn if that didn't make for some good reading abouty midnight. http://www.chevelles.com/forum/smile.gif I like it. Doesn't seem to care all that much about temperature. Reading some of the Tests they did with it made me think of the load this will put on the alternator/battery. Will this little setup need any kind of a charge pump contraption to prevent sudden (and consecutive) surges on alt/bat.?

I gotcha now on the saw tooth setup.

I did some quick searching and found this guy: http://www.fairchildsemi.com/ds/FA/FAN7554.pdf

Don't know why I can't seem to find a simple IC that creates it's own Saw tooth for reference AND has a "voltage control pin" such that a given input voltage results in a predetermined duty cycle. (like what you said, but all on one chip and without extra crap on board)

There are a few other considerations while my brain is ticking.

Delayed startup: warm motor enough to trigger a full-on fan condition will make the car hard to start. Or we could still keep the three position switch setup. UP is box controlled, middle is off, down is relay latched on. The latter making for a good backup if **** stops working. http://www.chevelles.com/forum/wink.gif

Would you buy this for, say $50 a pop? including relay, sending unit and instructions? Maybe coppertop can mass produce them? http://www.chevelles.com/forum/biggrin.gif he likes building this stuff.... I like getting payed. http://www.chevelles.com/forum/smile.gif

------------------
71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
BEST 60': 1.85 w/street tires.
BEST 1/4: 12.5 with 1.89 sixty foot (street tires)
BEST MPH: 109mph

Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
Video of me staging (smoke of course) (http://www.auburn.edu/~ledfojw/vids/mike_chevelle_burnout.avi)

I also already have a 3 pin SOP chip that put's out a coltage porportional to temperature. Works well right in our range. Don't know where to put it. Was thinking of taping it to the radiator and calibrating accordingly. But it'll be hard to make the results the same for each car.

Just an idea to not have to buy a GM sending unit, wich is $$$ I'd imagine.

Should be able to use a factory type guage sending unit (or an EFI one), which can't be much money and would mount in the intake. I've got to find the resistance range for them.

IC of the day - LTC1624. Not exactly it but close.

Go to www.elecdesign.com (http://www.elecdesign.com) and look for the Idea for Design for 1/11/99. Click on the link on the left and go down that page to find it. You'll have to register.

I still think I can do what you want with a schmitt trigger, op-amp, and some resistors and capacitors.

Got to go, it's late.

Peter

Mike, it's from IPS (an Allen Bradley company). It's used for controlling the exciter field on our 1030KW generators.

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My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

<BLOCKQUOTE>quote:</font><HR>Originally posted by cjlandry:
on our 1030KW generators.
<HR></BLOCKQUOTE>

http://www.chevelles.com/forum/rolleyes.gif

Damn that's flux capacitor territory. http://www.chevelles.com/forum/wink.gif

been busy at work, will get back on this soon I hope. ****, I should put a co-op on it.



------------------
71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
BEST 60': 1.85 w/street tires.
BEST 1/4: 12.5 with 1.89 sixty foot (street tires)
BEST MPH: 109mph

Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
Video of me staging (smoke of course) (http://www.auburn.edu/~ledfojw/vids/mike_chevelle_burnout.avi)

Alright electron heads you lost about half of us when you started throwing out the initials of things.
Simply put if you figure it out I'll take one

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Philip Mullaly
72 TPI El Camino
The Z-meano (http://www.chevelles.com/showroom/philsfastride)
The Z-meano mill (http://www.chevelles.com/showroom/tpiengfwd)

NVBOB, I have used the Derale dry innert switch alot. Great simple reliable and moreover easy device. Comes on at 180 shuts off at 170 and my themostat is right at 175, so most of the time, unless you come to a stopping situation, the fan stays off.

Run the signal circuit off the accessory side of the ignition switch to the power relay for the fans. That way you will avoid what one other poster commented on about the fan coming on when you are starting the car, the signal won't appear until the ignition switch is in the on/detent.

If you decide to run a wet sensor of any kind, do not run it on the bottom of the radiator bung or outlet. This temperature varies a great degree depending on conditions etal.

Man-o-man....youse guys with the variable fan controlers. How complicated do you want to make this? Why buy a $50+ part and increase the MTBF of the circuit, for which a simple $15 kit will do. And, sawtooth and squarewave generators pose all kinds of EMI issues with radios in cars. ARe you doing this just to say you can, which I respect (used to design DC apparatus controls for Nukes myself), or is there a real reason. The fans do not control the temperature of your coolant and or engine anyway. Its the themostat that ultimately makes that decision.

And, finally, there is a neato temperature gauge that has a built in processor that you can adjust the output (low for relay control only) and is adjustable. Of course the gauge just takes info off the wet sensor at the intake. I would go for that!

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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies

Our crewboats at work use mechanical gauges to monitor temps. Each gauge has a switch that can be set to trigger an alarm at any temperature you like.

It's a very simple circuit. The gauge needle and an adjustable stop form the switch. The down side is that the needle stops there and won't read any higher. A boat skipper asked me to check out his boat a while back because "the alarm came on at 190 and just kept ringing even though the temp never got any hotter".

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My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

Steve,
80% becasue we can.
20% becasue it would be functional.

When this fan does run it hauls ass and is very loud. I want to be able to slow it down, draw less current and still cool just as well.

I think the cfm of this fan outflows the convection/conduction property of my radiator. http://www.chevelles.com/forum/wink.gif

I'd be happy with a 3 stage speed control and not this speed-proportional devide.

I am also going to implecate a "cool down" timer. after you **** off the car, the fan will run on med (or low) for about 2 minutes.

------------------
71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
BEST 60': 1.85 w/street tires.
BEST 1/4: 12.5 with 1.89 sixty foot (street tires)
BEST MPH: 109mph

Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
Video of me staging (smoke of course) (http://www.auburn.edu/~ledfojw/vids/mike_chevelle_burnout.avi)

pmullaly I thought they were starting to talk dirty!

BB....coooool. I thought so.

YOur fans should be able to completely off at 25 MPH or so. What kind of fans do you have that are so noisy? Skewed bladed fans are generally quieter than straight bladed fans. Fan efficiency depends on not only blade design but shroud design as well.

I used to use the SPAL top of the line fan that was a straight bladed fan that sounded like a piper cub taxiing up! I switched to the slightly less efficient skewed bladed model and it was much better on the ears.

I also use the Derale fans....super quite and moves over 2300 cfm of air.

Sounds like you are having fun with your projects tho....and that's why you do it.

I watch stuff like this because I write cooling articles for several differing media outlets including some web sites. So, when something unusual comes along I like to explore and find out as much as I can.

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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies

Mike;

I've been busy too but I'll try to get something soon. 3-speed vs fully variable will employ mostly the same technology. With a variable unit, it would just slow down until it got cool enough to just shut off so it would time itself.

Peter

I've been drinking so beer with me. http://www.chevelles.com/forum/wink.gif

Hotrod. the MArk VII fan in question pulls about 5000cfm. no ****. draws a good 35Amps. A pair of these could accelerate a sesna.

Peter. It's all good. With the 3 speed selector you wouldn't have any PWM. Rather more logic based. If/then stuff with window comparator(s) to switch each level. I just don't want to build a voltage devider network with 100Watt resistors. http://www.chevelles.com/forum/smile.gif Just cut the batt voltage in half and the speed will drop by 50% also. I'm stating the obvious, yep I'm toast. hell, let's just toss in an accelerometer and have the fan only turn on when the car isn't rolling.

Wow......35 amps is a housefull. I have heard alot about those fans. I will have to look at them a bit further. I have not run into a situation that needs that kind of air.

Have a friend with a 502 in a 55 that has a dual spals and does just fine. What are the dimensions of that fan?

Thanks for the info.

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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies

Hotrod, I just measured mine. The shroud is ~19" by ~21" (it's hard to measure on the car). The blade is 18", 7-blades, sort of spiral style. The motor protrudes from the radiator a total of ~5½". This is after cutting about ½"-¾" off of the shroud to get it closer to the radiator.

Mine pulls 38 amps at 14.3 volts (as measured with a DC Amprobe). I run it with two parallel relays activated with a simple rocker switch. I only turn it on when needed (sitting in traffic, etc).

It's the best $100 and a couple hours labor that I've ever spent.

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My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

Sounds like a real sucker to me and relatively inexpensive to do! Where do you buy these suckers?

Also,I hope your relays will take the load individually and/or on their own and the second one in parallel is for just redundancy. If not, see my comments on a "cooling forum" thread http://www.chevelles.com/forum/Forum27/HTML/000105.html about the misgivings of running two parallel relays in a circuit. If one won't handle the load...get a bigger one that will. The relay(s) that won't handle the load individually will fail due to pull-in and drop-out current spikes eventually.

I have automotive relays that handle up to 70 amps and are less than $10! That information is provided on that thread as well.

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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies

the 70 Amp relay mentioned above is at:
http://www.newark.com/product-details/text/cd119/60873.html

I use a 70 or so Amp relay from Bosch. Has screw terminals for the load line. much better for higher gauge wirer. costs about $25 though. big guy with "pencil eraser" sized latching contacts.

edit: After reading my post I see it might come across a little abrasive. I don't mean for the following to sound derogatory or argumentative in any way. Just stating my personal experiences from a tightly budgeted stand-point. I apologize if I offend Steve, Mike, or anyone else.

Yeah, I'm an electrician and I know all the theories. I've done a couple of automotive circuits like this over the years and have never had a problem with any of them.

I've been running these relays on this fan for well over a year now and the contacts are still in good shape (I just cracked the cases and looked).

While I agree that a single heavy current relay is better, I'd much rather spend $4 on a pair of relays than big money on a single one. I can replace these relays several times before I'll have covered the cost of a single larger relay.

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My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

[This message has been edited by cjlandry (edited 02-14-2002).]

<BLOCKQUOTE>quote:</font><HR>Originally posted by cjlandry:
I apologize if I offend Steve, Mike, or anyone else.<HR></BLOCKQUOTE>

What the hell are you talking about? http://www.chevelles.com/forum/confused.gif Your getting too mooshy in your old age Chad. http://www.chevelles.com/forum/wink.gif

http://www.chevelles.com/forum/smile.gif

Old age!?!?!? http://www.chevelles.com/forum/eek.gif

Mike, I was just trying to prevent any potential flaming from breaking out.

Yeah, I might seem a little "mushy", but I've seen a few too many people take things the wrong way. Steve's new here and I don't want him to get the wrong impression.

I'm talking in the "big leagues" with all these "Double-E's" and I'm nothing but a "learn as you go" electrician (aka "industrial control technician" in my business).

We don't always have access to the parts we need offshore, and I'm known for finding ways to "get out of a bind" until the next shipment comes out. So things like "parallel relays" come with the territory. Saves the company a fortune in hot-shot fees when you can "get by" with something.

But thanks for the reassurance anyway. (Except for the "old age" part). http://www.chevelles.com/forum/smile.gif

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My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

[This message has been edited by cjlandry (edited 02-14-2002).]

Geez guys. If anyone's the old guy around here it's me and I'm still learning. Those university engineering books didn't teach me everything. Think I forgot a lot of things but can't remember what they were. Oh well, I think it's Miller time. Maybe with a bowl of those fish shaped crackers. Anyone know how they get those things to smile?

Chad, (llandry)....didn't take your post offensively or abrasively at all. Everyone has a pool of experiences that they are comfortable with and that's that.

I had a friend of mine buy a 35 pu that had dual relays for one BIG fan, and it took all of 6 months and every 6 months to go thru one relay at a time. I finally talked him into buying a bigger relay. Since we live in Atlanta and the fan cycled all time, the workout on the contacts was problematic, whereas they relay was underated by itself. Some other factors do play in like circuit impedances and such. I can see where the differences in look-out impedances will affect the overall outcome. Some of these big stereo systems will large capacitors can have subliminal affects on the DC bus. Battery type too, whereas I have seen vehicles with several batteries on the DC bus and you can't get any spikes to rise on those buses. So, circuit design is important in affecting all these little anomolies.

Youse guys has opened my eyes to this Mark fan and I am always interested in more choices. This is why I troll here. I also write various media articles as a free-lance tech writer....so I look for material and experiences as well. This is good! Keep the information coming.



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Steve Jack - ConceptOne Pulleys and Brackets / Engineering & Marketing Technologies

Chad Chad Cahd. what am I gonna do with you? Your not getting old bro. Hence the added "wink" after the sentence. Easyyyyy there Trigger. http://www.chevelles.com/forum/smile.gif

Steve, the two most popular electric fan setups around here are the Mark VIII and the Windstar dual fan setup.

I probably would have gone with the Windstar if I hadn't stumbled onto the Mark VIII first. The Windstar setup fits the radiator better and the dual fans are independently controllable. In that case a single relay for each fan is the ticket, whether they're switched independently or not.

I'm always keeping my eyes open at work looking for an excuse to order some high current 12 volt relays. Maybe I can get something for the crewboats...... http://www.chevelles.com/forum/biggrin.gif

Mike, Mike, Mike..... What are you gonna do with me? http://www.chevelles.com/forum/biggrin.gif I knew you were joking. I was joking back at ya'. http://www.chevelles.com/forum/biggrin.gif Typing even with "emoticons" just doesn't convey my dry sense of humor. Wait 'til you meet me at CB'02. You'll get to see first-hand just how dry and abrasive I can be. http://www.chevelles.com/forum/biggrin.gif (At least that's what everyone tells me.)

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My Web Page (http://www.landry-family.com) (updated 1-9-02)

"America will endure!"

Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

Im going to install the windstar fans in a couple of months.
Anyone have a p/n for a thermal sensor that fits in the block which kicks on around 200-205 and off around 190-195?
I havnt been able to locate any

thanks

found something for the first half of it.

https://www.jameco.com/cgi-bin/ncommerce3/ProductDisplay?prmenbr=91&prrfnbr=3137&cgrfnbr=501&ctgys=

still a kit and pretty cheap. Maybe we can just not use the suppliet FET and put in a more robust piece? Solution reach all in a little black box? INclude a fuse and have people mount it right on the fan housing. Possible use the fan's forced air to cool the heat sink?? http://www.chevelles.com/forum/smile.gif

I have been following this thread and I was wondering if you guys have made any progress on the sawtooth variable controler for the fans. I would be interested in purchasing it from you guys if you get one produced. If not I would like a prototype design with part #'s to use if you have something. I have some limited electronics prototyping experience and shouldn't have any problems putting it together.

Also what year of windstar vans are you guys pulling these dual fans off of?

Thanks

I haven't. I'm lucky to find time to wrench on my car any more. I use to think up stuff like this at work, but have been busy doing the stuf they pay me to design. http://www.chevelles.com/forum/smile.gif imagine that.

If you give me a "what I want to do" type post I'll give you some pointers. Or a post would suffice and others can help.

Try a search ont he Windstar fans and/or user name chev-hell to get the scoop on them.

------------------
71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
BEST 60': 1.85 w/street tires.
BEST 1/4: 12.5 with 1.89 sixty foot (street tires)
BEST MPH: 109mph

Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
Video of me staging (smoke of course) (http://www.auburn.edu/~ledfojw/vids/mike_chevelle_burnout.avi)

go to "o'riley's" or a place like that, and look in the Bosch buyers guide, it's got different TFS (thermal fan switchs) and get one to screw into the head, or install into the radiator hose like i did. used a 1.5" pipe and welded a bung to it then screwed it in.. do a search on TFS i've got pics somewhere of it.

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1970 SS396 AKA 454/4spd
My Chev-Hell Page (http://hometown.aol.com/jnkb2cool/home.html)
GOLD Member #783
Metroplex Muscle
Ft.Worth, Tx
(OO=ss=OO)

Go to Heating & Cooling section .Do a search on a member HOTRODSR. There is some good technical data there.