suspension 101

[betty.k]

well i can’t let trash hog the limelight so now it’s my turn to fill your little heads with ideas!
as you may know i’ve been a big fan of off roadifying my bcg’s and the biggest part of my success is due to suspension. first, it’s important to know that the function of suspension is to ensure contact between the wheel and driving surface. as you can imagine, a wheel can’t turn, accelerate or brake when it’s in the air. so let’s cover the basic terms and principals.

spring: the springy bit (well, duh!). this can be made from metal, air, rubber, etc, or in my case plastic.

compression: when a wheel encounters a bump, it moves up, squashing, or compressing, the spring. this is compression.

rebound: when the wheel moves over and past the bump the spring extends back to it’s original length. this is rebound

travel: the distance a spring ‘shortens’ when compressed.

damping: if you’ve used a pogo stick you’ll know that compressing a spring stores energy that wants to release rather quickly. so if you don’t want your car bouncing around like a super ball, you need to slow down the compression and rebound speed. this is damping. good suspension will have independant control over these features. so if your driving surface consists of frequent small bumps or during high speeds, you want the suspension to react quickly; low damping. and slow speeds, large bumps = high damping. quite often no damping is worse than no suspension.

preload: this means how hard the spring is. good suspension will offer different springs of varying softness and will allow fine tuning. the higher the preload, the more weight is needed to compress the spring.

spring rate: some materials will offer resistance quicker when compressed such as steel springs. grab a spring and squeeze it. you’ll notice that the more you squeeze it, the more pressure needs to be applied in order to compress it further. this has a high spring rate. some shocks use air as the spring. grab a bike pump. put your thumb on the end and pump you’ll notice that the same thing happens only it will offer little resistance until the end when it just stops, unlike the steel spring which offered resistance in a more linear fashion.

different materials have different qualities, like air and steel in the example above. steel springs are more sensitive to small high frequency bumps and air is great for large bumps where long travel is needed, it just takes a bigger hit to get it moving. obviously i’m limited with a bcg as to how many of these functions i can adjust, but by using different types of plastic i can have varying degrees of damping and vary preload with plastics of different thicknesses or removing some material.
hopefully we’ll see a few more bouncy bits around!:8ball:

Edited by – betty.k on 22 December 2003 23:45:51

[leonli17]

Nice one betty.k.
It seems that trash got a new challenger.:smiley2:

[z-beam]

http://groups.msn.com/bitchargoz/paintingmods.msnw?action=ShowPhoto&PhotoID=68

the Bb “camo rally”
there is spring (afx) suspension in the front full size wheels. and the trailer with netting has a single spring mounted against the axle(adjusted so it doesen’t press against it to hard)

http://groups.msn.com/bitchargoz/general1.msnw?action=ShowPhoto&PhotoID=83

[z-beam]

here’s a close up of the trailers springs.

http://groups.msn.com/bitchargoz/othermods.msnw?action=ShowPhoto&PhotoID=101

and the Bb’s springs:

http://groups.msn.com/bitchargoz/othermods.msnw?action=ShowPhoto&PhotoID=102

[betty.k]

yeah, nice!:smiley2: i’ve just started playing around with steel springs on bcg’s. so far so good, just gotta handle with care, when you drop them they fall into a time portal or something cos they’re gone for good!:8ball:

[z-beam]

let your thumbnail grow. its the best tool in the world for holding small fidly things.

if you need any extra springs send me a pm.

[betty.k]

a couple of things i should mention about suspension in use.

1/4 of your suspension travel should be taken up as ‘sag’ sag is the amount a shock compresses when the vehicles full weight is applied. eg; when you get on your mountain bike with suspension, 1/4 of available travel should be used up.

‘bottoming out’ is when your spring is compressed as much as it can be. this should happen regularly but not often. if your suspension never bottoms out, then back off the preload.:8ball:

[z-beam]

i found with afx springs you can wind multiple springs together even at different lenghths to increase performance.

i’ll give my secret supply for all the community to enjoy… the locksmith! they all have a stash of small springs in different strengths they pull out of locks, as each one useally containes at least 4 of the same type. and if they are nice will sell em to you for cheeeeep!!!

[betty.k]

hey, nice tip! i’ll be doing a little lock destroying now!:8ball:

[z-beam]

nooooo betty!!!!

the locksmith allready destroys many saws hacking up locks for you…

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