question for TURK and clutching gurus??

mopar1rules

mopar1rules

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hey turk/clutching gurus, in your aaen clutching book, its says at the end of chapter 6, "the pressure spring", that to find the "rate" of a spring, you take the maxx load and subtract the pretension load from it, then divide that # by the total sheave travel (which is 40.66mm on srx/viper/etc). i do that and i don't get the #'s that i should be getting, that are in aaen's spring charts in the back of his book.

for example....the yamaha y/w/y spring

45kg start--2.5 rate--128kg finish

i take 128kg-45kg=83kg then divide 83kg by 40.66 (total sheave travel) which = 2.04 (not the 2.5 that's stated on the chart)

what the heck am i not seeing/doing right? anybody have any input?
 
oh, that would help....LOL. i took where the load measurements are taken on the spring (2.9" installed or 73.66mm and 1.3" full shift or 33mm) and came up w/40.66mm. i guess i should have just measured the sheave travel, instead of assuming that the 40.66mm would be the amount of sheave travel. thanks watchmaker.
 
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yeah, 33mm is exactly the sheave travel. measured it to be certain. now, i have another question that rose about. i'm measuring some clutch springs that i have laying around, and found 2 stock y/w/y viper springs to be much higher on the final load than what the chart says. its suppose to be a 45/128kg or 99/282lbs, and i measured 1 spring to finish @ 299lbs and the other @ 304lbs. this could probably be the cause for the vipers over-reving in stock form? the spring which had 304lbs finish, was out of my viper. the other spring which finished @ 299lbs was from my buddies srx. don't know why stock springs measure so far off from what the chart says? i measured the finish load @ 1.300". anyone else w/input and ideas?
 
mopar1rules said:
yeah, 33mm is exactly the sheave travel. measured it to be certain. now, i have another question that rose about. i'm measuring some clutch springs that i have laying around, and found 2 stock y/w/y viper springs to be much higher on the final load than what the chart says. its suppose to be a 45/128kg or 99/282lbs, and i measured 1 spring to finish @ 299lbs and the other @ 304lbs. this could probably be the cause for the vipers over-reving in stock form? the spring which had 304lbs finish, was out of my viper. the other spring which finished @ 299lbs was from my buddies srx. don't know why stock springs measure so far off from what the chart says? i measured the finish load @ 1.300". anyone else w/input and ideas?
Click to expand...
if 73.55mm is the installed height, then shouldn't you measure final load at 40.55mm ,33mm is the amount of travel not what the spring is compressed to.at 40.55 your numbers might be closer.
 
well, that's kinda what i was thinking too, but doesn't yamaha measure the spring loads @ 73.66mm (installed) and @ 33mm? that's why i was measuring the full shift values @ 33mm (1.3"), instead of the 40.66mm that you and i are now thinking. i'll try the new 40.66mm full shift value and see what i can come up with. also, has anyone measured the actual installed height dimensions to be 73.66mm and the full shift height 40.66mm? thanks.

forgot to add that the y/w/y spring that measured 304lbs on the finish, was out of my viper w/stock clutching and it ran 9000 rpm. i don't know what my buddies '00 srx ran w/the 299lbs measured y/w/y spring.
 
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What are you using to rate the springs? Does the rater repeat well with the same spring? There is a general tolerance with coil springs and I want to suggest it may be as high or higher than 5% of the spring rate. I'm pulling that info out of the cobwebs in my head so I don't know how accurate it still is or was. I do know that you need to check every spring you put in the race car, even when they are new because of manufacturing tolerances/variables.
 
I wonder is full shift should be calculated based on 30mm sheave travel. 30mm is the number used for full shift on the weight charts in the tech section, even though we know the travel is 33. That would effectively lower your results.
 
i'm thinking maybe its the tolerance of the spring i'm fighting? if yamaha has a 5% +or- tolerance on the springs, then that's 14 lbs either way that it could vary from the 282lb nominal. anyone else think its this?
 
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