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Clutch Spring alternative?

Started by andyb, April 12, 2010, 09:47:31 PM

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andyb

OEM FJ spring = $60 or something silly
FJR spring = $30

EBC Clutch Spring

Dennis Kirk Part #: 383786
Manufacturer Part #: CSK903
  = $21

Who's gonna be the test dummy and see if it's any good?  Probably available other places, but this is where I saw it (totally by accident no less).


FJmonkey

Might be good as a second spring for slipping clutches......
The glass is not half full, it was engineered with a 2X safety factor.

'86 Ambulance - Bent frame, cracked case, due for an overhaul
'89 Stormy Blue - Suits my Dark Side

andyb

If it's stiffer than stock (which wasn't mentioned in the description that I could see) it could be an alternative to running dual springs entirely.  Otherwise it could be used to back up a stocker, or for $40 you could buy two of them and run them that way.  Just don't know.

Pat Conlon

Is the double spring set really cheaper than a $140 coil spring conversion?
By the time you factor in the added cost of the 14mm clutch m/c needed with the double spring set up, I bet it's closer than we think.
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racerrad8

Quote from: andyb on April 12, 2010, 09:47:31 PM
Who's gonna be the test dummy and see if it's any good? 

I am on it...I have a source for EBC as well. I will get one in hand and check it out. I think I can also check the tension compared to the new O.E. ones I have in stock.

Randy - RPM
Randy - RPM

SlowOldGuy

Quote from: Pat Conlon on April 12, 2010, 11:27:23 PM
Is the double spring set really cheaper than a $140 coil spring conversion?
By the time you factor in the added cost of the 14mm clutch m/c needed with the double spring set up, I bet it's closer than we think.

Wussy!  Be a man and stick with the 5/8 master.

DavidR.

RichBaker

Quote from: Pat Conlon on April 12, 2010, 11:27:23 PM
Is the double spring set really cheaper than a $140 coil spring conversion?
By the time you factor in the added cost of the 14mm clutch m/c needed with the double spring set up, I bet it's closer than we think.

I did the double spring set-up about 8 years ago, still have the original FJ master......  no problems. Why do we "need" a 14mm clutch master?
Rich Baker - NRA Life, AZCDL, Trail Riders of S. AZ. , AMA Life, BRC, HEAT Dirt Riders, SAMA....
Tennessee Squire
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the fan

Quote from: RichBaker on April 13, 2010, 06:12:25 PM
Quote from: Pat Conlon on April 12, 2010, 11:27:23 PM
Is the double spring set really cheaper than a $140 coil spring conversion?
By the time you factor in the added cost of the 14mm clutch m/c needed with the double spring set up, I bet it's closer than we think.

I did the double spring set-up about 8 years ago, still have the original FJ master......  no problems. Why do we "need" a 14mm clutch master?

While video games, texting, and remote controls have done wonders for virtual hand eye coordination, hand strength is quickly fading from the gene pool.

andyb

Because while it's manly, the 5/8 master with double springs is difficult to modulate as well.  My 60' times noticably dropped when I went to coil springs...

The 14mm master simply makes the friction point that much longer, spreading the work over more distance.  Should make it easier yet to dial in the amount of slip you want.


racerrad8

Well,
         I got the aforementioned EBC spring tonight when I got home. I have yet to give a full comparison to the O.E. unit, but by first impressions I probably won't be buying another one. I am not sure if they are distorting the spring to give it the advertised 15% better clamping force, but this thing is bent...

I will do some measuring tomorrow when I get to the shop and include some pictures of the obvious things I see by holding it in my hand.

I am not impressed and it doesn't look to good up to this point; more to follow.

Randy - RPM
Randy - RPM

racerrad8

Testing is complete and I can say that the one EBC I received does not match the performance of a new diaphragm spring, and out performed three used springs by just 1.03%. Each spring was cycled two times prior to taking a reading. Each spring/combination was rated three times and each rating was consistant. I checked each spring and combination from zero to over-center for maximum clamping force.

I tested three new Yamaha springs and the tested; 289, 291, 288 lbs.

I tested three used Yamaha springs and the rated; 250, 251, 250 lbs.

The EBC spring rated; 259 lbs.

Two new Yamaha springs doubled up rated; 581lbs.

New Yamaha and used Yamaha spring; 556lbs

New Yamaha & EBC spring; 553lbs.

Used Yamaha & EBC spring; 513lbs.

See pictures and captions;


Yamaha spring on the left, EBC on the right

Stock Yamaha spring, with center fingers machine ground flat to match spring retainer plate angle.

EBC Spring. Outer red "T" markings on outer edge of spring are the two contact points against that flat glass plate. The two red fingers on either side 90* to the "T" marks are the high point with the center of the kink between the center of the two fingers. The distance of the warpage of the spring is an equal .030 on each as show by the two feeler gauges.

Close up of .030 feeler gauge placed into kink of EBC Spring.

The quality difference of the two springs are as listed;

Yamaha:
Stamped manufacturing process.
Shot peened and heat treated finish.
Angle ground fingers to match angle of retaining plate.
Consistant measurements within factory specification.

EBC:
Plasma cutting manufacturing process (rough edges).
No shot peening of the spring before or after heat treating.
Spring has "kink" which allows a .030 feeler gauge to fit under each side of the spring.
Same .030 difference on the finger side of the spring.


Yamaha maximum spec for spring warpage at the base is .004.The EBC measures .030 on each side.
The minimum finger height spec is .240. The EBC spring measures .280 on the low side and .310 on the high side. The Yamaha spring measure .270 equally on all fingers.

Like someone said in an earlier post it might make a sufficient additional double spring. It might even be easier to compress due the reduced clamping pressure. If someone wants to try it as the secondary spring let me know. If after that it is determined to be an adequate spring for the double application I will consider adding them to my inventory.

If you decide to buy one to try it, make sure you install it under the factory spring so the retaining ring does not wear through from the unfinished & pointed edges of the fingers on the EBC spring.

Ultimately after getting the spring shipped here it comes to an $8.00 difference in the cost of the Yamaha and EBC springs. I cannot do the volume a Dennis Kirk can and get the EBC pricing as well as they are. I sell the Yamaha spring for $36.95 and the EBC would be listed at $28.95

Hope this helps with the decision making process.

Randy - RPM
Randy - RPM

Marsh White

FANTASTIC testing and writeup Randy!!!    :good2:    THANK YOU for taking the time and effort to do this for ALL of us!

Data = good!  I know I will now NEVER buy an EBC clutch spring.  It is also very interesting that it is only 40lbs or so that separates a new yamaha clutch spring from a worn one.

My clutch has been slipping lately and I will be ordering new discs and a new yamaha spring from you shortly.

racerrad8

Quote from: Marsh White on April 21, 2010, 11:10:43 PM
Data = good!  I know I will now NEVER buy an EBC clutch spring.  It is also very interesting that it is only 40lbs or so that separates a new yamaha clutch spring from a worn one.

That was my thought as well and I have been looking at the complete clutch system since I completed my findings. I think the spring looses some tension, the discs wear and the total thickness of the clutch pack diminishes, thus exaggerating the spring weakness. The more the clutch fibers wear, the more the spring slippage becomes apparent. By doubling up the spring, you have just increased the clamping force and the clutch fiber thickness is removed from the equation until the pressure plate bottoms out against the center hub, and it starts slipping again.

That's my theory anyway...

Thanks, Randy - RPM
Randy - RPM

andyb

Good info, shame it's a crappy item!  I was so excited to see another option out there, too!

As far as your idea of having the stack height getting smaller and that making things seem weak, you're likely spot on.  The spring only has a very short working distance, too much pressure and it's just flat (near infinite rate), too little pressure and it doesn't contact (zero rate).  Compared to a coil spring, which uses a smaller % of total travel through each actuation as well as through the lifespan of the clutch pack, it's going to feel weak much sooner.

The easy way to tell would be to get a fairly worn, slipping clutch, and just jam another fiber or steel in it to bring the total stack height back up to preload the spring again.  Hrm...

racerrad8

Quote from: andyb on April 21, 2010, 11:51:16 PM
The easy way to tell would be to get a fairly worn, slipping clutch, and just jam another fiber or steel in it to bring the total stack height back up to preload the spring again.  Hrm...

It won't work...The additional thickness makes the slave cylinder stroke too short and won't allow the clutch to disengage. There have been several people try that with the racecar and next thing they know they can't get it in gear at all...

Randy
Randy - RPM