Stators

One of the most critical areas of a automatic race car

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jmarkaudio
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Stators

#1 Post by jmarkaudio » Tue Oct 07, 2008 11:30 pm

I am curious, when (if ever) would a flat blade stator be beneficial? Isn't the idea of the stator to turn the fluid around, with a curved blade, to increase torque multiplication? I know things have to be adjusted a little to increase stall, but I would think a flat blade would be limited to a specific speed difference between the pump and turbine. Wouldn't this leave it short somewhere? And is the blade angle determined by the projected stall, or stall determined by the angle, or??? I have a flat 17 blade 30˚ that stalls 7100, a curved 40˚ that stalls 6500. Peak torque 639 at 6300, peak HP 830 at 7500 in a 1875lb dragster. Best ET 4.98@137 1/8 mile in decent weather, 5.08/8.00@135/165 in hot with the 6500 converter, 5.03@135 with the 7100 in decent weather. I feel like I'm still missing some ET with both. 6500 is a spragless, 7100 has a sprag but never got to run it in the 1/4.
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Re: Stators

#2 Post by Marty Chance » Wed Oct 08, 2008 5:50 pm

wow great question (i could lecture on this all day) you are correct curved blades do turn the fluid direction with less turbulence and will usually increase the torque multiplication , but you have to be careful as they can lock up too fast and put too much load on the motor which may result in slowing down the acceleration rate of the motor. An "air foil" type blade also has benefits (flat on one side curved on the other so longer distance to travel on one side of the blade-same as airplane wing) So what is the best blade design ????? all of the above !?! remember the most important thing about making the car accelerate as fast as it can , is to make the motor happy , by that i mean to create a rate of efficiency that allows the motor to accelerate at it's fastest rate . Curved blade stators are great for torque multiplication , but if you cant get enough "flash" stall out of the converter , you may have to go to a flat blade and lay the blade angle down more (ex 30deg instead of 40deg) now this will decrease the amount of torque multiplication BUT it may increase the DURATION of the torque multiplication (ex curve blade multiply @2.2 for 7 tenths of a second or straight blade multiply 1.6 for 1.2 seconds ) now we have been working on some "air foil" blade designs on our 5 axis cnc to help increase the velocity or speed through the stator , this will be kinda the best of both worlds flash stall of the straight blade stator but lock up of a curved blade stator . HOPE this answers your questions , but this is a very short answer to an extremely complex question because stall speeds , efficiency ratios and torque multiplication is RELATIVE not ABSOLUTE. Marty Chance
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Re: Stators

#3 Post by jmarkaudio » Wed Oct 08, 2008 9:57 pm

So does that mean the straight blade would work better without a sprag, staying on the converter longer, and the curved better with? This would make sense that you would not want a spragless to reach the point it would want to unlock and not be able to.

In my case, can you lock it up too fast? While it is a small block, it is a 447 ci with reworked cup SB2 heads. I am putting together parts for an Aluminum block 460, 4.25 stroke with purpose built SB2's flowing well over 400, but still trying to keep it in the same power band as the current engine for valvetrain as well as overall reliability for bracket racing. Obviously with a SLIGHT increase in power... :shock:

As far as sprag vs spragless.... My feelings are you could take the best spragless and put a sprag in it and only stand to gain in the top end. But for reliability and consistency I think the spragless is better. One less thing to break or slip.
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Re: Stators

#4 Post by sunsation540 » Wed Oct 08, 2008 10:07 pm

good thing i read this early, that was an understandable answer to a complex occurance now what's a stator?? LOL nice job explaning this.. i have 2 converters one that will remain nameless,it's spragless and is faster in the 60 dosen't hit the tires so hard, but gets loose on the hose ,and one of yours nice stall works well but locks up hard, like blows the tires off hard. but when u turn the power down it will hold 6% slip @3570 and 1100 hp is there something in the middle?
make a plan and stick to it !!

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Re: Stators

#5 Post by Marty Chance » Thu Oct 09, 2008 7:12 am

SUNSATION - your neal chance converter needs to slip a little longer so as not to put the power to the ground so agressively (stator change) and your brand x converter may need to be "tightened up so it can hold more power with out having excessive slippage . Call me when you have time to spend about 20 minutes on the phone and we will go over all of the specifics .

JMARK- nothing works "better" with a spragless , if you have a spragless that works great for you and you put a sprag in it with no other changes the converter will work as good or better , and the sprag converter will really shine on the back half of the quarter mile .
A spragless will always reach the point it wants to unlock but not be able to regardless of stator design. I recommend the mechanical diode instead of conventional spring and roller or dog bone sprags and they are a positive engagement and have no possibility to slip , they are also available to ALL converter companies , so you can request your converter man to install the mechanical diode but note most converter companies speak negatively about the diode because of the cost of the diode and they dont want to loose there profit margines .
With any power plant you can lock it up too fast , the first time i worked on a brad 6 with a c rotor screw blower (3600 HP) i made the mistake of locking it up too fast! but i do like the idea of the long stroke small block for bracket racing because the broader the torque band the less it is effected by weather changes and we have the luxury of locking it up faster to hit softer (more consistant) with out killing the performance.
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Re: Stators

#6 Post by jmarkaudio » Thu Oct 09, 2008 10:17 am

I do agree with the spragless HP loss. I have already spent a bunch on converters and have a couple others as well, and with the investment in the new engine I may be stuck for a bit with what I have. I've been the MD route, and after taking one apart I am not sure I want one back in unless they have made major improvements in the design. I do like the fact that they don't break and destroy everything though, just slip (usually at the worst time).
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Re: Stators

#7 Post by jmarkaudio » Thu Oct 09, 2008 10:33 am

The Mechanical Diode® Company

Technology Introduction
Brief Overview Of Conventional Technology

Currently, two types of overrunning clutches predominate - the prag clutch and roller ramp clutch. These devices Rely on a wedging action to lock-up, which means sprags and races must endure extremely high radial stresses to transmit even a moderate amount of tangential force, or useful torque. As a result, these clutches must be made from expensive, high quality bearing steel which has been hardened to withstand the forces generated by the wedging action.
In additional, conventional one-way clutches offer limited functionality and greatly reduced load capacity in applications with very-high overrun speeds, high engagement speeds, and vibration - all of which are present to some degree in most automotive environments.
All of these factors combine to make conventional one-way clutches the weakest link in automatic transmissions.


Brief Overview of Mechanical Diode Operation

The Mechanical Diode is a high-resolution planar ratchet which uses low-mass rectangular struts instead of ratchet pawls. The struts are positioned between a plate with pockets for the retracted struts and a second plate with notches for strut engagement. The struts have a very high ratio of contact area to mass, yet are slim enough to achieve full engagement with only 15 degrees of pivot. The struts' low mass, rectangular construction, and lengthwise pivoting axis give them a very low moment of rotational inertia. This - together with the small actuation angle - allows a relatively small spring to almost instantaneously move the strut into locking position. The position of the strut asses (radially, in a planar fashion) renders strut actuation insensitive to centrifugal force. During even moderate overrun speeds, the struts "fly" on a layer of oil.

Planar Delivery Of Force for Strong, Reliable Operation


The Mechanical Diode's planar strut arrangement and 15 degree strut engagement angle allow it to transfer force in a more direct fashion - thereby avoiding the trap of using "extreme radial forces to transfer even moderate amounts of torque" which afflicts conventional one-way clutches.
In fact, the MD utilizes more than 93% of the strut's compressive strength to transfer torque. Parasitic (axial) forces are relatively small - especially when compared with friction-actuated one-way clutches, where the contact angle is typically 83 degrees and 99% of the compressive load is directed radially. In wedging-action clutches, both sprag loading and hoop stress are very high, and these parts must be manufactured from expensive, high-quality steel.
By contrast, the MD generates lower parasitic forces, so it's typically smaller and lighter than wedging-action one-way clutches.


Single-Strut Positive Engagement vs. Load Sharing

Instead of sharing enormous radial loads among many sprags or rollers, the Mechanical Diode works by engaging a single strut at lock-up, a design made possible by its planar transfer of force and the large load bearing surface offered by each strut.

Since only one strut engages at a time, precise - and expensive - machining isn't needed to ensure the simultaneous engagement of many parts. In sprag-type clutches, a failure to engage all load-bearing surfaces simultaneously can quickly lead to catastrophic failure of the device.
For positive engagement, the MD's struts use angled load bearing surfaces, so the force of engagement automatically forces the strut into a fully engaged position.
And due to the positive locking nature of its components, the MD suffers no torsional windup.
The absence of torsional windup and the low actuation angle of the Mechanical Diode - typically 15 degrees - results in excellent engagement resolution, which minimizes engagement impact and prolongs component life.
Long Overrun Life

With the MD, the load-bearing surfaces of the components never come into contact during overrun - any incidental contact is between surfaces which don't mate during engagement.
And, even at moderate overrunning speeds, the struts remain in their pockets and "fly" on a layer of oil - never coming into contact with the notch plate at all. The higher the overrun speed, the more pronounced this effect becomes. This allows the MD to overrun at very high speeds, and affords a long overrun life.
Manufacturing Advantages

Typically, the Mechanical Diode can be manufactured more economically than conventional clutches - a result of two main factors.
First, the MD generates few radial stresses, so the struts and "races" can be made from less expensive materials. This allows manufacturing techniques such as powdered metal molding and fine blanking to be used.
Secondly, the MD engages only one strut at a time, so precise machining - mandatory when the load is to be shared among many elements - isn't required. This further reduces costs.
In fact, due to the smaller size and form factor of the MD, drop-in replacements for existing friction-locking one-way clutches can be easily designed and afford ably manufactured.
Versatile, Reliable, Affordable - Even Under Adverse Conditions.

Mechanical Diode offers extreme reliability in all types of automotive environments, especially those where high torque, vibration, or high overrunning speeds decrease the effectiveness of wedging-type one-way clutches.
In addition, its smaller form factor and typically lower cost of manufacture make it an excellent tool for automotive manufacturers who are striving to improve product reliability while holding the line on costs.
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Marty Chance
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Re: Stators

#8 Post by Marty Chance » Mon Oct 13, 2008 7:11 am

JMARK thanks for the great questions and comments and for posting the pics of a regular mechanical diode. Have you ever broke a mechanical diode ? do you prefer spragless or sprag ? What improvements to the mechanical diode were you refering to ? And you said you like the fact that they dont break and destroy everything but they "slip" . Slip ?? can you demonstrate this or show us how you came to the conclusion that they slip ?
Note : my intention is not to argue nor do i expect all to agree with me , respectfully Marty Chance
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Re: Stators

#9 Post by jmarkaudio » Mon Oct 13, 2008 10:16 am

Well, the one posted came out of my Transmission Specialties converter. The first time it failed, it acted just like a broken or sprag that had spun in the stator. Took it to JW, John called and said it was the Diode and that he could rebuild it. Back in the car worked fine for a while. At the Div.2 divisional race here in Orlando back around 2002, it did the same in eliminations against Scotty Richardson, I was not a happy camper. I took it back to John, he suggested converting it to a spragless. It immediately lost a tenth and 2-3 MPH, but it was also deadly consistent, much improved over before. And I ran it until May 07 when I got my new car without any breakage or consistency issues. As you can see, no apparent issues with the diode other than normal wear marks, the only thing I can figure is that the springs weaken from heat or the pockets the blades lock in fill up with debris from clutch and bushing wear, reaches a point where it slips. Another possibility is chatter when on the two step unlocking it as well as the stress of coming on and off the t-stop. If it had spun or broke where it fits in the stator, I think John would have said so.

As far as improvements, only locking on one blade at a time is a concern, a lot of power on one blade. And for preference, it would be great to have reliability, performance and consitency. I like the idea of your CNC profiled stator, I was not keen on the flat blade I have, It will be going back for adjustments.
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Re: Stators

#10 Post by Marty Chance » Mon Oct 13, 2008 6:00 pm

JMARK thanks for the clear answer , I would say that the trouble you have had is not typical of the mechanical diode and if you are winning races with your spragless then "dont fix what isnt broke" . I still have to wonder what caused the problem for you , the last time you had the md in your car as it looks to be in good shape and i would point out that John Winters is a trust worthy person in the racing industry and i have confidence in his word .
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Re: Stators

#11 Post by Marty Chance » Mon Oct 13, 2008 6:03 pm

JMARK i forgot to tell you we designed our own md and it has 10 struts instead of 5 and ingages 2 at a time not 1 .
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Re: Stators

#12 Post by jmarkaudio » Mon Oct 13, 2008 9:34 pm

Glad to hear, might be worth trying out. Have you had any failures, and if so what damage do they cause? Also what issues have you seen with the MD I was running?
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Re: Stators

#13 Post by Marty Chance » Thu Oct 16, 2008 5:55 pm

FAILURES ON NCRC DIODE - we have seen a cracked outer housing on a turbo charged big block that makes way over 2000 HP ,but he laid on the trans brake until it melted down everything !!blew the fluid out of the trans and caught on fire , that would be the extreme . Otherwise no failures and remember those diodes go in cars making 1500 to 3500 HP . These are built with very close tolerences (tenths)

STANDARD MD - issues we have seen are bent or broken struts or cracked outer housing but this is not common , we see the diode being very reliable , more expensive than other "sprags" but very reliable .
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Re: Stators

#14 Post by jmarkaudio » Fri Oct 17, 2008 2:35 pm

Well a bit of an update. In preparing my 7100 stall converter for return, I noticed the tag on the box with the converter data and found out it's spragless. Does the new NCRC diode require a change in stator or does it slip right in? And how much should I expect in cost difference?
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Re: Stators

#15 Post by Marty Chance » Wed Oct 22, 2008 8:05 am

JMARK sorry it has taken so long for me to reply . Most spragless units are built for the same stator bore as the mechanical diode so it should be a "drop in" part. The cost for our 10 strut is very expensive ($550) and is normally used only in extreme power adder vehicles making more than 2000 HP , so it is an investment for the person who needs a sprag and is willing to pay the high cost for the lates technology . Do you have a bolt together converter where you can change back and forth from sprag to spragless to compare the difference in your car? If so , I would recommend you try the diode you already have , as there may have been a misunderstanding between you and JW because the pics of your diode show there is NO damage to it. I would be happy to sell you one of our new monster diodes , I just did not want you to spend a bunch of money when it appears to be no damage to the diode you already have . Marty Chance
Neal Chance Racing Converters
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