If you drove the Alaska Highway from mile zero, you would have passed through my home town at 86 miles before the start of the Alaska Highway. Did you go through Edmonton or did you go up the Rockies via Icefields Parkway and Jasper?
barryadam wrote:Continuing with the hijack of the op's topic....
If you drove the Alaska Highway from mile zero, you would have passed through my home town at 86 miles before the start of the Alaska Highway. Did you go through Edmonton or did you go up the Rockies via Icefields Parkway and Jasper?
Barry
Yes. That is, we went up by way of the Icefields Pkwy, took a left after Jasper on to 40 to Grande Prairie, and hung a left to Dawson Creek. Coming back, we went from Grande Prairie to Edmonton, then down through Saskatoon, and lunch with Ray Korpan and his merry band of misfits, then sauntered home.
And btw, hi-jacks are standard fare here. Eventually we meander back towards the original topic.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.
Rick Pope wrote:
And btw, hi-jacks are standard fare here. Eventually we meander back towards the original topic.
One of which was the orientation of the progressive spring...
Now, if I think about what is "unsprung weight" - I try to picture also what would be "sprung weight". That, is all the weight of the bike "above" the spring - which means: I cannot accept your theory, that the orientation of the spring changes the "unsprung weight"...
The top of the spring is connected to the bike, so it is sprung weight; the bottom of the spring is connected to the wheel (through the lower fork), so it is unsprung weight. A regular spring could therefore be described by a linear function from sprung to unsprung along its length. A progressive spring could be described by a curve function from sprung to unsprung along its length. If the heavy part of the progressive spring is down, it would contribute more to unsprung weight; if the heavy part were up, it would contribute more to sprung weight. In any event, the numbers would be small compared to the other components.
Whether I be right or wrong, this would make interesting conversation around a campfire with a nice selection of full bodied beverages, and perhaps a nice cigar. But in the grand scheme of things, I would never be able to tell the difference in handling. A few hundred miles of tread wear on that tire would likely make more difference.
Now back to our regular program.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.
The top of the spring is connected to the bike, so it is sprung weight; the bottom of the spring is connected to the wheel (through the lower fork), so it is unsprung weight. .
Technically, the top of the spring is not connected to the rest of the bike. The stanchion, or fork tube, rests on top of the spring. Whether the spring itself is part of sprung or unsprung weight, is - as Rick says - a subject of philosophical discussion
And the fork tube is bolted to the bike. Trust me: the result is the top of the spring is connected to the bike (and the preload keeps it that way); it is not free to move independently. Since the spring is the part that's creating the whole concept of sprung and unsprung weight, and since it has mass and therefore weight, part of it is sprung weight; part is unsprung weight. If the spring were massless, it would be neither.
It depends on how you define "connected"....
Per definition of "sprung", that part of the bike ends on top of the spring. If you simplify the design of a "sprung" mass, take a wooden board and put it loosely on four springs, one under each corner. Now you have a "sprung" mass: the wooden board. Nobody would argue that the springs are part of it.
Same with a bike. The "sprung mass" is the mass that is supported by the suspension.
Sprung weight includes parts and components that induce a load on the suspension, either static or dynamic. Anything attached or linked above the springs are considered to be sprung mass. These components can be physically located lower in the center of gravity from the springs but if their primary link to the tires and ground travels through the springs/coilovers it fits this class.
But you're missing the point that the springs aren't massless, so at each point on the spring, the part above that point is sprung and the part below is unsprung. The boundary conditions at top-of-spring and bottom-of-spring are "fully sprung" and "fully unsprung" respectively.
If I had to take a guess, since I wouldn't be able to solve the differential equations even if I could come up with them, I'd use the following on a progressive spring:
Find the centre of mass.
To allocate the unsprung mass, multiply the spring's mass by the length between the sprung end and the CoM and divide by total spring length.
To allocate the sprung mass, multiply the spring's mass by the length between the unsprung end and the CoM and divide by total spring length, or just subtract the unsprung mass from total mass.
...so I sheephishly asked the various motorcycle "mechanics" that are neighbors to my woodshop which way I should install Progressive springs. Without hesitation one of them said .... "tight coils to the top, of course". He said it with such conviction that I anticipated rock-solid reasoning behind his answer and queried as to why he thought this.
His reply was....... "tighter coils displace more oil than loose coils and therefore should be at the top".
When pressed about the pros and cons of a larger volume of oil -vs- a smaller volume of oil in the bottom of the forks, the conversation took a turn down hypothetical lane with no real value. I can't dispute his statement regarding ''oil displacement'' as that seems to be a fact, but whether or not it makes any difference is unknown.
Now which way do I put these springs in again? Oh yea, right side up, of course.
PC
Don't take life too seriously, you will never get out of it alive.
Since they aren't too hard to remove and install, you could try it both ways and let us know if you notice a difference. Either way, you're not going to damage anything.
