Definition - Primer
I always want people to talk using "standard" terms and definitions. People can write and talk with definitions and use it as a language that everyone understands. When a customer talks to each other or me they will use definitions that control the explanation of a problem. This is just a part of "Controlling" the tuner by the way they move about and correspond regarding clutching. This is how a tuner can talk with other people who are novice tuners or non-tuners. When people talk with terms, standards are created for people to use so there will be accurate descriptions even when there is "barnyard" talk about clutching.
I like to direct people on terms to make them think like me when I talk about clutching, kind of like "clutching language". Everyone who talks clutching gets the same effect or understanding as if you talk in legal terms or engineering terms. When I use the word "language" in clutching language I mean we all talk with terms from knowing a precise meaning of a detail in clutch troubleshooting and tuning. When people talk to each other they know what each other is saying. Osmosis comes to play here also. The reader or listener absorbs the suggestive flow of the chat effortlessly because of the clear concise terms.
The definitions below are of a variety from my "in progress: theory book "Increase your clutching IQ"
Aggressive
Backshift
Bottom End
Equilibrium
Holding Power
Midrange
Overshift
Rated RPMs
Spring "Rate" & "Forces" - Definition
Start force
Straight shift
Torque point
Track Speed
Undershift
Spring "Rate" & "Forces" - Definition
Here is my top pet peeve. When it comes to springs and their forces, I always hear or read the word "rate" when the word "Force" should be used. Here people describe a quantity of a spring and are not referring right to the element of the spring.
Rate is the fixed ratio between two things. In the case of a spring, rate is the quantity lbs measured per inch of change. You compress the spring it takes "x" amount lbs of force (per inch) to change the height of the spring. The starting point is the installed height and the finish point is the full compressed height. The installed height is at rest or the engagement or beginning of the shift. The full compressed height. is at full shift.
Force is the strength or energy exerted or brought to bear to hold something in position. For example a 170-300 primary spring. The spring needs 170 lbs of force to keep it at installed height and must add enough force of up to 300 lbs to change it's position to full compressed height..
***The spring does not have 170 lbs "rate" at the beginning of the shift.
The spring at installation is compressed 1.25" and requires 170 lbs of force to keep it that position.
The spring at full shift is compressed to 2.5" and requires 300 lbs of force to keep it that position.
To figure out the rate of the spring you do a simple calculation.
i]300 lbs - 170 lbs = 130 lbs
ii]2.5" - 1.25" = 1.25" of distance travel between engagement and full shift.
130 lbs / 1.25" distance = 104 lbs/inch of rate.
From installation height of 1.25" then you want to compress it just 1" more, you would have to add another 104 lbs on top of the 170 lbs to make the spring compressed to 2.25". To keep the spring compressed at 2.25" that would mean you did 170 + 104 = 274 lbs to keep it in that position.
Getting back to my pet peeve about "force" and "rate" example:
Q]...Change to a softer spring, one with less finish rate in the primary. Softer primary spring has faster up shift.
A]...For fun to talk of the 170-300 spring, the idea given here is to lose the 300 and go with something lower. For lack of better numbers lets say "260".
Might want to change to a 170-260 from a 170-300.
Now that you know the definition of rate, what do you think when you read this quote where the word "rate" is used? Right idea, however not using the correct term. I'd like to correct the Q] by having the word rate exchanged with "force".
New Q]...Change to a softer spring, one with less finish "force" in the primary. Softer primary spring has faster up shift.
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Start force (primary & secondary spring) the value of the spring in lbs. force when it is installed.
Final force (primary & secondary spring)The amount of lbs. force when the clutch is at full shift
Aggressive
Many times I see confusion regarding the word "Aggressive" when it comes to clutching.
People relate this word when they talk of how the clutches shift.
Regarding the primary - Aggressive: The clutch exerts more forceful energy using less engine rpm.
The clutch uses more of the meat of the torque curve from the engine, shifing harder with lower rpms.
When you quickly cycle the throttle, the engine is not revvy, the sled responds with greater movement from your thumb action.
You alter the feeling of the sled with greater action in the bottom end of the midrange when pressing the throttle.
Backshift
Specifying what you observe, or specifying the capacity of the system while the sled is in motion; usually under full throttle...
You read scenarios like: weak/strong
*weak...come around the corner, pressed the throttle and the engine would hit 500 rpms low and slowly accelerate.
strong...come around the corner, pressed the throttle and the engine is right there, whammo at 8 grand
*weak...accelerates hard to top end but if the snow load increases the engine rpms starts to drop
strong...accelerates hard to top end like my buddies sled except when the snow gets deep, my engine rpms stays at rated
*weak...good acceleration but if i flip the throttle the engine comes back in at low rpms
strong...good acceleration and when i blip the throttle, bam the engine hits the right rpms
*weak...while climbing my rpms are 1000 rpms low
strong...while climbing my rpms stay rock steady
*weak...when I land after a drift the rpms come in low and won't recover till i slow down
strong...when I land after a drift, the rpms come in low but recover while I keep on the throttle
IF There are opinions of backshift using adjectives like "strong" or "weak", example....."strong backshift" or "weak backshift"
THEN could you define - Backshift: is the ability for the engine to accelerate to rated rpms, as the load changes.
Overshift
Quotes Aaen: You only have two reference points when you work with a transmission. You have to compare engine speed (rpm) and vehicle speed (mph) with your gearing to know what ratio you are in.
The advantage of the snowmobile transmission is its ability to hold the engine rpm at the power curve (rated rpm) while the it continually changes ratios.
Quotes BRP pulley development: The goal of clutch calibration is to keep the engine, at full throttle, at it's peak power RPM and at the same time to select the highest possible gear ratio dictated by the load on the drive axle. The speed diagram illustrates what the goal of good clutch calibration is.
Summation; The ideal shift would be for the engine to be at its rated rpms from low ratio to high ratio. If the rpms vary under wide open throttle, then the shift is either over the rated rpm line or under the rated rpm line.
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Overshift is tied to under revving. Under shift is tied over revving.
IF the ratio change "duration" is too small, like the secondary won't upshift,(too low of helix angle/too high of secondary spring forces)
THEN engine speed flares into over rev.
IF the ratio change "duration" is too large, like the secondary upshifts too easily, (too large of helix angle/too low of secondary spring forces)
THEN the engine speed lowers into under rev.(Overshift)
Could all the information be overlapped and connected to say that...
Over shift: While accelerating at wide open throttle;
a. (clutch up shift) shifting the clutches out faster than the motor can handle, revealing low rpms.
b. (engine speed) A variation of low rpm caused by a surge of increased secondary load against the primary load.
c. (time) reveals accumulated time not accelerating at rated rpms.
Because of Aaen's reference point of having a straight rpm from low ratio to high ratio, then it could be thought as over shift is a separate detail from under shift.
a. b. c. is suitable for the definition of Overshift.
Bottom End - Usually related to sled speed; The start of the upshift, beginning mph's.
Midrange - Usually related to sled speed; The middle 2/3 of the mph capacity of the sled.
Top End - Usually related to sled ground speed; The end of the upshift, peak mph's.
Straight shift - (Is) the rpms maintaining a certain rpm from bottom end to top end.
Holding Power - The ability to maintain a track speed as load increases.Rated Rpms = Continuous highest hp rpms. Example; Stock 800R has a continuous highest hp rpm at 8150
Track Speed - Usually referred by owners of mountain~longtrack sleds, but may include short track sleds; The speed in mph that the track is rotating at under full throttle, heavy loads. (climbing or flat deep types of different snow)
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