Motion Ratio vs. Spring Rate

[swong46]

Hey, I have a question that seemed evident but would like to ask on here

Lets say you have a motion ratio of 1:1 and rises to 1.5:1 and you decide to use a 100 lb spring.

Now you take a 1.5:1 ratio which rises to 2:1 with a 75 lb

Is this essentially the same when considering other factors such as frequency or other dynamic factors?

[Sormaz]

What do we actually care about? Wheel Rate or Spring Rate?

You're on the right track, but recall that
Wheel Rate = (Spring Rate)*IR^2

The installation ratio must be squared, as it will scale both the force, and distance

[JT A.]

Don't forget about your damper travel range. Most shocks that I know of made for our application have around 2" total travel (cane creek/ohlins and the penske shocks). Your wheels have to have 1 inch of travel in each direction. If your motion ratio is 1.5 your shocks will need 3" of travel or else they will hit the bumpstops & maybe completely bottom out.

On the other hand, if you have a motion ratio of .25 and run a 500 pound spring you will be using very little of your damper travel and your damping characteristics won't be smooth and consistent.

[JDS]

rget about your damper travel range. Most shocks that I know of made for our application have around 2" total travel (cane creek/ohlins and the penske shocks). Your wheels have to have 1 inch of travel in each direction. If your motion ratio is 1.5 your shocks will need 3" of travel or else they will hit the bumpstops & maybe completely bottom out.

On the other hand, if you have a motion ratio of .25 and run a 500 pound spring you will be using very little of your damper travel and your damping characteristics won't be smooth and consistent.

It is important to keep in mind, that while the spring force might be the same at the end of travel with various combinations of spring rates and motion ratios, how the spring force increases will be different. In other words, if you are doing a steady state analysis, you might see identical results with different combo's of rates and ratios, but the the transients will probably be very different.