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UTV's Off Road ( RZR, YXZ, Mini Buggy, Carts,etc.) => UTV Chassis and Suspension => Topic started by: fabr on February 13, 2009, 06:10:15 AM

Title: Unsprung weight
Post by: fabr on February 13, 2009, 06:10:15 AM: Time for a discussion of unsprung weight and the effects of it . Who wants to start?
Title: Re: Unsprung weight
Post by: Boostinjdm on February 13, 2009, 06:20:47 AM: You just did...
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 07:00:10 AM: No,I started the topic ;D but here goes.
First off, let's start with a definition of what unsprung weight is. Unsprung weight is anything that is not supported by the suspension system.In other words the entire weight of the tire/wheel/brake rotor/brake disc/wheel bearings/seals/bearing races/etc.,anything in general that is connected to a suspension member. It is also a generally accepted principle that all suspension links(trailing arms/a arms/shocks etc..) are calculated at 1/2 their weight(1/2 unsprung and 1/2 sprung).
Title: Re: Unsprung weight
Post by: fastcorvairs on February 13, 2009, 07:11:19 AM: Ummmmmmmmmmmmmmmm!!!!!!!!! gg: gg:
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 07:15:15 AM: Ummmm what? Comments?
Title: Re: Unsprung weight
Post by: fastcorvairs on February 13, 2009, 07:17:59 AM: Quote from: Masterfabr on February 13, 2009, 07:15:15 AM
Ummmm what? Comments?

Just ah wait-en to see what shake's outta du trees on this one.
Title: Re: Unsprung weight
Post by: Carlriddle on February 13, 2009, 07:29:30 AM: Less is better? :-X

ff:
Title: Re: Unsprung weight
Post by: Nutz4sand on February 13, 2009, 10:21:56 AM: I have heard that for every 10 pounds of unsprung weight you can shed its like loosing 100 pounds of sprung weight.

(Also heard its even better if its rotating mass)

This was applied to full size racecars but does it apply to Minis as well? I would assume so but you know how that words spelled.
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 10:56:05 AM: It all applies the same.
Title: Re: Unsprung weight
Post by: Carlriddle on February 13, 2009, 11:00:36 AM: What the easiest way to measure? Frame on stands shocks off and see how much each wheel weighs on scale ~~divide in half~~(roughly)??
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 11:05:49 AM: IMO ,it is a goal to achieve as little unsprung weight as possible while maintaining adequate strength. It will make for a better handling car more capable of keeping the tire in contact with the ground. Unsprung weight is not a place to just throw mass into to get needed strength.
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 11:10:28 AM: Quote from: Carlriddle on February 13, 2009, 11:00:36 AM
What the easiest way to measure? Frame on stands shocks off and see how much each wheel weighs on scale divide in half(roughly)??
No, frame on stand,shock off,place scale centered under tire/wheel assembly with suspension at mid travel,weigh.There's your true unsprung weight.Add the weight of the shock shaft and you pretty much have it perfect.
Title: Re: Unsprung weight
Post by: Carlriddle on February 13, 2009, 11:26:15 AM: I forgot the shocks. I know my rear tire are heavy. The less rotational mass the quicker the motor will spin thru the RPM range.
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 11:27:09 AM: Don't divide in half though with this method.
Title: Re: Unsprung weight
Post by: Engineer on February 13, 2009, 11:35:51 AM: Get your scales out and post up some numbers...... I need some design criteria, to meet or exceed, actually this is scored like golf low number = better. ;D

ff:
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 01:54:49 PM: I will soon as I get the rears mounted.I know mine will be heavier than I want till they get on a diet.
Title: Re: Unsprung weight
Post by: plkracer on February 13, 2009, 02:32:34 PM: Ever try driving a solid axle truck (mainly the front axle) through the dunes? I don't care how much suspension you got, it's like a bucking bronco.
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 02:35:59 PM: The weight just jerks you down into the bottoms.
Title: Re: Unsprung weight
Post by: artie on edge on February 13, 2009, 02:44:10 PM: The issue with unsprung weight is simply that once it gets moving (hits a large bump for eg), you have to stop it from moving and get it (the wheel) back into its postition fast (back on the ground so it will steer, drive and brake!).

This isnt easy as it makes us use heaviers shock valving (and sometimes springing) than we would otherwise need and the actual weight and having to control it makes us compromise the tuning of our suspension.

This is true of all vehicles with suspension. Fabrs right, their is no IDEAL weight, just minimise it to the max while ensuring the unit CAN do its job without failing.

IMO ;D
Title: Re: Unsprung weight
Post by: artie on edge on February 13, 2009, 02:45:54 PM: "for every action there is an opposite and equal re-action"

THis is the premise behind unsprung weith...
Title: Re: Unsprung weight
Post by: fabr on February 13, 2009, 03:31:32 PM: weith? Is that some new Oz slang? ;D