atb

Post #46:


New information:

After looking at this project carefully, the builder think that the "first" batch of these, because they are going to build several units will be in the $3,500 dollar range, including the aluminum flywheel. Once they are only building one or two at a time, the price will be closer to the $4K range, as I was initially told.

Heh...I know it's still not cheap, but every little bit helps make it easier to swallow.

hacker-pschorr

, what the hell, I re-scanned the thread and totally missed that post.

If you price out a complete replacement of a double disc clutch, this is right on the mark.

In other words, it really isn't any more expensive than a stock early clutch.

You also won't be chasing down erratic self-adjusting intermediate discs or release bearings prematurely failing.

mark kibort

so, its now hydralic.... using the existing upper bell housing for something its not really meant to do, be a leverage point for the new T/O bearing. with all that force to engage the clutch, is there an concerns that those ears will bend or break over time?
also, what a god send to not have to worry about the lever arm instalation

clamping force rating vs the stock DD or an enhanced DD clutch??

Mk

Rob Edwards

Mark, where do you come up with this stuff? Here's a picture of the clutch in Anderson' racer, installed in 2005. See any broken bellhousing ears?

Good enough for Anderson, good enough for you.

IcemanG17

Sure $4k sounds like alot....until you figure out that its EVERYTHING....flywheel, hydraulics, center throw out plus the not exactly cheap carbon clutch assembly.... Figure how much a STOCK setup replacing all of that would cost....close to $3k....

Remember reducing weight that spins at ENGINE RPM is huge.....insane really.......if this assembly is say 5 lbs lighter.....that could be 1+ mph faster the end of a given straight..... The example I used in "Chassis Engineering" from Herb Adams uses a 3000lb car with 300ft-lbs (not HP)...... taking 15lbs off the car increases speed by .20mph.....taking 15lbs off axle weight = .6mph taking 15lbs off engine speed rotating weight.... 3mph increase!!!!! thats like a 32hp gain!!!! Over 2 hp per lb gain!!!!

mark kibort

this is not true at all. flywheell HP gain is NOT 2hp per lb. and to tell you the truth, its based on what gear you are in and how fast you are traveling.

In other words, the effect of the 5lb lighter flywheel, will have the effect as if the weight was in the car to a weight of 180lbs in first gear (18hp, 3hp per lb)
2nd gear , 50lbs, or 5HP, or 1hp per lb
3rd gear 25lbs or 2.5HP or .5HP per lb
4th gear 13lbs or 1.3hp or .3HP per lb
5th gear 7lbs or .7HP or .15hp per lb.

so, if you spend time off the last turn of Thunderhill, in the last 3 gears, you can see the only gain for 5lb flywheel lightening, will have the effect of between 1/10th and 2hp for our cars. (average about 1hp, TOTAL) so, 1hp is not going to change your top speed to any measureable level.

as a note, a restrictor was used on a WCGT Vet at sears one year with and without a restrictor, and the 15hp or so loss, resulted in 1mph difference down the main straight. (just as a realltiy check here)

dont believe me. work out the numbers yoruself . cant fool mother nature, or father physics (aka newton)

flywheel diameter of about 9" (so your results may vary.. )

v=w x R/(Gear x final)

M=I x ( gear x final/R)^2


Just to show you i didnt (or dont ) just make this stuff up

Mk

IcemanG17

MK
I didn't make this up either.....an AUTOMOTIVE ENGINEER, extremely well respected one at that published it in his BOOK

Its called "Chassis Engineering" by Herb Adams, Chapter 15 "Rotating Inertia" pages 107-109

Just read it for yourself........his example was a 3000lb car loosing .5% of weight (15lbs) 3 different ways......the most effective was rotating weight that spins at engine rpm.....reducing this by 15lbs gained 2.96mph vs the baseline of just removing any weight...

GregBBRD

Mark:

The guy that makes my carbon/carbon clutches says they will hold 850 ft. lbs.

Since he builds them for all kinds of American muscle cars, I have no reason to question his claims, but also have no way to verify them, since an 850 ft. lb. 928 engine only exists in someone's dreams....

The limit on the "enhanced DD clutch" is in the 400 ft. lb. range.

I can tell you this.....once these clutches are engaged, there is NO slippage what-so-ever. And the resulting power "transmission" is absolutely amazing. Feels like you "added" 75 horsepower to the engine. It really is amazing how much the "enhanced" dual discs really do slip.

Worth noting, I've got a complete single disc carbon/carbon clutch "on the drawing board" to "replace" all of the "stock" street clutches, once Sachs completely runs out of pieces.

One of these will hold over 400 ft. lbs. and should be even "smoother" than this dual disc clutch.

I'm guessing that this is more torque than you are currently making....and will be more than adequate for most "street" vehicles, plus last 2-3 times as long.

jbrob007

Greg, In reference to the single disc carbon/carbon clutch thats on the drawing board - Once it is completed, can it be used as a replacement for the DD and/or Single Disc clutches? I like the dual disc clutch you put together - freakin' AWESOME! But frankly even a Porkenized 86.5 is no where near 400 ft lbs, much less 700 ft lbs, so its kind of overkill for the everyday 928. If it can be used in ALL the non-boost / non-stroker cars then the single disc clutch will be your biggest seller! I'm hoping it will be cheaper too... I can HOPE cant I...??

If so, looks like I've got another item for the wish list... only this is something I actually NEED!

Thanks!

GregBBRD

Yes. The plan is to make a direct replacement for both dual disc and single disc clutches, for the cars that don't make huge power, but still need a high quality clutch.

As the stock pieces "disappear" and replacements become harder and harder to get, a completely new approach is going to be needed. I originally "started" the "dual disc" clutch as a pull clutch using the original arm. Right in the middle of developement, it became clear that Sachs wasn't going to continue building even the simple parts....like T/O bearings. So, I trashed what I had and started over, building a hydraulic push clutch, with readily available replacement pieces, looking towards the future.

While the dual disc unit is "overkill" for a huge majority of the people, a single disc carbon/carbon unit should fill the void.

Because a completely new flywheel will be required, it will never be "cheap"....but it will be significantly cheaper than the dual disc.....and frankly, it is getting pretty "tough" to find a good used flywheel, for any of the variants of these clutches.

mark kibort

Greg, i wasnt questioning the holding torque, or its design, but the TO bearing mounting using the ears of the upper bell housing. its only aluminum, and i was wondering if that is a concern.

by the way, im making 400rwt now, and was up to 420rwt before tuning out torque for some HP up top.

mark kibort

Just because he is an engineer, it doesnt mean he can breat the laws of physics. i gave you the equation and the reality of the situation.
no way can 15lbs change straightline speed by 15mph. if he can, i want to see the numbers, not the test, because , as in the case with most tests, they are not controlled. that 3mph could have been caussed by exit cornering speed, or something else. thats why use physics to show what will happen.

as i mentioned, rotating weight vs weight in the car, like that on the wheel or tire is like 2x if its on the tire for example, as if it was on the car. 15lbs, would be 30lbs in the car, and is like 3hp. 3 hp cannot make a 3mph differnce.. its just cant. this is EASY to disprove. His book was probably making a point about the inertial forces and how they are greater than weight in the car, but his values and assesment was way off. talk to ANY mechanical engineer about this . we can calcualte this pretty easily.

in fact, go to a drag simulator and plug in the HP needed to change a 1/4mile spint by 3mph. its not going to be 3HP

mark kibort

Brian, just read your first post. i dont know the conditions, but if its a drag race and that 15lbs was taken off the flywheel, it could make that much difference, because in 1st and 2nd gears the HP gain could be in the 30hp range. going down in each gear dramatically. my post used the actual saving of 5lbs. and being used on a road course. (3rd through 5th gears) the reality of how it will effect you on the road course is shown by my numbers.