offical AE spring thread
03-09-2012, 04:57 PM
#1
offical AE spring thread
this is for the discussion of springs and there related items:
discuss away!
discuss away!
03-09-2012, 06:28 PM
#2
I figured you would like that pic... clear and concise. 
I was trying to relate it to something simple looking. It seems most are confused by all the coils on a shock spring... so i figured relating to a simple swaybar would help.
I mean... i could have thrown a curve ball and mentioned that a sway bar is actually dynamic... since it ties in BOTH sides of the suspension... lol
1. YES
2. FAIL Lets look at one side of a swaybar... a simple spring. When you shorten the leverage points the rate doesnt change... you increase its efficiency. Lengthening the leverage points decreases its efficiency. The wire STILL BENDS (notice i didnt say torsional twist) AT THE SAME RATE.
This is relatable to a BB spring and why it feels 'plush' or more 'consistent' than a regular AE spring. The BB spring is less efficient at doing its job than the smaller AE spring (and also one reason why the AE spring tries to move off axis... which also addresses efficiency... but i digress). This is also why a shorter lever on a swaybar increases response... its using the same rate and doing its job more efficiently.
3. FAIL "As the number of coils decreases, the spring rate increases."
Really? So... youre telling me you have changed your mind with your previously posted...
"... when the wire diameter increases, spring rate increases."
Im not even going to get into your active/inactive coil theory... ill just leave that for you to think about.
----------
As far as the amount of coils in a spring... you will notice as a general rule that the thicker the wire the less coils there are in a linear spring. Also as a general rule... the more suspension travel, the greater the number of coils that will be present in any given linear spring.
You will see mix matched versions of this in various applications. Trust me though... if wire diameter does not change... neither does the spring rate... regardless of the amount of coils present... or how they are linearly implemented.
I know you (and i say that collectively... not pointing any fingers) have been told over the years that 'this' means 'that' but this is an opportunity to get the facts straight... and get some real insight on why something works as it does.
I was trying to relate it to something simple looking. It seems most are confused by all the coils on a shock spring... so i figured relating to a simple swaybar would help.
I mean... i could have thrown a curve ball and mentioned that a sway bar is actually dynamic... since it ties in BOTH sides of the suspension... lol
1. YES
2. FAIL Lets look at one side of a swaybar... a simple spring. When you shorten the leverage points the rate doesnt change... you increase its efficiency. Lengthening the leverage points decreases its efficiency. The wire STILL BENDS (notice i didnt say torsional twist) AT THE SAME RATE.
This is relatable to a BB spring and why it feels 'plush' or more 'consistent' than a regular AE spring. The BB spring is less efficient at doing its job than the smaller AE spring (and also one reason why the AE spring tries to move off axis... which also addresses efficiency... but i digress). This is also why a shorter lever on a swaybar increases response... its using the same rate and doing its job more efficiently.
3. FAIL "As the number of coils decreases, the spring rate increases."
Really? So... youre telling me you have changed your mind with your previously posted...
"... when the wire diameter increases, spring rate increases."
Im not even going to get into your active/inactive coil theory... ill just leave that for you to think about.
----------
As far as the amount of coils in a spring... you will notice as a general rule that the thicker the wire the less coils there are in a linear spring. Also as a general rule... the more suspension travel, the greater the number of coils that will be present in any given linear spring.
You will see mix matched versions of this in various applications. Trust me though... if wire diameter does not change... neither does the spring rate... regardless of the amount of coils present... or how they are linearly implemented.
I know you (and i say that collectively... not pointing any fingers) have been told over the years that 'this' means 'that' but this is an opportunity to get the facts straight... and get some real insight on why something works as it does.
The truth is that a compression spring's spring rate will vary by 4 parameters!
1. Wire Diameter (As wire diameter goes up, spring rate goes up!
2. Mean Coil Diameter (As diameter goes up, spring rate goes down)
3. Number of active Coils (As Number of Active coils goes up, spring rate goes down)
4. The Material Modulus of Rigidity (Modulous goes up, spring rate goes up)
Here is a great online spring calculator to demonstrate how each parameter influences the spring rate: http://www.efunda.com/DesignStandard...igner.cfm#calc
or this calculator:
http://www.planetspring.com/pages/co...calculator.php
The equation for calculating spring rate is:
Spring Constant = k = ((d^4)*G)/ (8*(D^3)*N)
d= Wire Diameter
G= Modulous of Rigidity
D= Mean Coil Diameter
N= Number of Coils
[This information can be found in "Mechanical Engineering Design, 5th Edition" By Richard G Budynas and Keith Nisbett] **Attached is a scanned copy of the page**
The anti-roll bar analogy actually helps further prove this. The length of the lever arm of anti-roll bar just allows you to apply more torque to the bar given the same force.
However, if you will notice when parameters that effect the total length of wire are increased...the spring rate goes down. This is because you have more material to absorb that same energy and this is anologous to having a longer (wider) anti-roll bar. Where given the same torque on the end of a longer rod will result in a greater angle of twist of the rod. If you shorten the rod for the same torque applied to the end you decrease the angle of twist. Similar to a compression spring if you increase the diameter of a anti-roll bar you will increase the resistance/ spring rate.
In regards to progressive and dual rate springs, I can get into that on another post. But here is a link that talks about springs and even uses the SAME image that people were debating over in the B4.1 thread.
http://motorcycleinfo.calsci.com/Suspension.html
I hope this is sufficient material demonstrating the parameters that give you your spring rate!!
Last edited by OptimumRC; 03-09-2012 at 06:48 PM.
03-09-2012, 06:53 PM
#4
03-09-2012, 07:05 PM
#5
Thats a whole lotta math for some China wire. 
Each one is gonna be different.
Each one is gonna be different.
03-09-2012, 07:20 PM
#6
03-09-2012, 07:30 PM
#8
Misinformation... or simplified fact? Its already been stated that the analogies were simplified for clarification, but since were getting in depth here...
In regards to 'active coils' and spring rate change... how does this relate to testing and comparison between both wire size and wire material?
In regards to 'active coils' and spring rate change... how does this relate to testing and comparison between both wire size and wire material?
03-09-2012, 08:09 PM
#9
Misinformation... or simplified fact? Its already been stated that the analogies were simplified for clarification, but since were getting in depth here...
In regards to 'active coils' and spring rate change... how does this relate to testing and comparison between both wire size and wire material?
In regards to 'active coils' and spring rate change... how does this relate to testing and comparison between both wire size and wire material?
In regards to active coils and spring rate change, as the number of active coils on a compression spring goes up, the spring rate will go down because the total wire length used in the spring has increased. When comparing wire diameter to number of coils, the wire diameter of a spring is a much more sensative parameter to change. For example, after a quick calc, a 10% change in number of coils results in a ~11% change in spring rate, while a 10% change in wire diameter will result in a ~33% change in spring rate!
Wire material is typically ASTM A228, but the relationship is directly proportional to spring rate. If you used a material with twice the modulous of rigidity, you get double the spring rate.
I think the biggest concern when visual inspecting and matching springs you have (since most don't have a way of measureing) is to count the number of coils and measure the ID of the spring (since the ID tolerance has a significant influence on spring rate). If these two parameters are close then it is likely that the two springs will be close in spring rate. The free length is not as critical of a perameter since it does not influence spring rate, BUT since it is longer...for the same spring rate compared to a shorter free length spring it will produce a higher total force when fully compresed (but will progress at the same rate). Since our shocks have preload adjustment this can be accounted for (i.e. a slightly longer spring would be set higher up on the shock body than a short spring, so that it achieces the same preload).
I hope that answers your question, if not feel free to re-word and I'll try again.
03-09-2012, 08:34 PM
#10
Suspended
The new Avid springs are going to put all of the miss matched, incorrectly labeled springs to rest. One of the local AE drivers is already running them, and he says they are way better than the TLR BB springs he was running (which he said were way better than the AE standard bore springs). This guy is a personal friend, not just somebody plugging a new product, so I really believe what he says. He also happened to get 3rd at the Reedy race in 4wd, so he is no slouch behind the wheel. I wouldn't be surprized if AE uses the Avid springs on their new BB shocks as standard. Kurt Wenger is the man behind Avids new 1/10th scale products, and as most of you know he was working for AE before his move to Avid.
03-09-2012, 09:18 PM
#11
'Wire material is typically ASTM A228, but the relationship is directly proportional to spring rate. If you used a material with twice the modulous of rigidity, you get double the spring rate.'
This is common sense. Material choice and inherent flex behavior would yield differing results in similar wire sizes.
'... misinformation stating that only wire diameter will change the spring rate of a compression spring.'
To be sure we are on the same page, by spring rate, you are referring to the actual numerical value of the spring... right? To me it sounds like you are defining a compounding effect of compression.
That in turn sounds like you are telling me that ALL linear compression springs are progressive in nature? How is this so when the entire spring, regardless of how many coils are present, bears the same load (not to mention weaken as they are compressed... all flexible materials do, thats why materials like Delrin break, and steel bends)? All coils are 'active' once under load. They remain active as a unit (a singular unit) unless compressed as one (basically becoming a bumpstop).
This in turn goes back to my simplified definition of spring/sway bar efficiency... the ability of the spring to do its work without moving off axis, or the bar without bending beyond its elastic point.
03-09-2012, 09:41 PM
#12
Maybe i should state it THIS way.
The thinner the wire size, the larger the ID of a linear compression spring should be, for it to be able to do its job effectively and stay on axis. It still isnt a progressive rate spring though... the value of the spring stays constant.
Im sure this is difficult when you are trying to mass produce a product for the market, and sourcing good but reasonably priced materials to get the job done.
Theres a reason AE springs have been on the 'chopping block' for years. You could pull 5 of the same color and would be lucky if any of them were close in a simple hand compression test... much less a metered compression test. Are you telling me this is a fault of the wire material consistency, the wire coil, or AE's math... ? If it is as complicated as you make it out to be, then AE's springs should be on the money and EVERYONE should be scooping them up.
Dont get me wrong... ive been die hard AE since the first day i first dropped an RC car on the track. BUT when i got into TC and started having to compare variations in products for consistent repeatable handling... AE springs went in the trash.
The thinner the wire size, the larger the ID of a linear compression spring should be, for it to be able to do its job effectively and stay on axis. It still isnt a progressive rate spring though... the value of the spring stays constant.
Im sure this is difficult when you are trying to mass produce a product for the market, and sourcing good but reasonably priced materials to get the job done.
Theres a reason AE springs have been on the 'chopping block' for years. You could pull 5 of the same color and would be lucky if any of them were close in a simple hand compression test... much less a metered compression test. Are you telling me this is a fault of the wire material consistency, the wire coil, or AE's math... ? If it is as complicated as you make it out to be, then AE's springs should be on the money and EVERYONE should be scooping them up.
Dont get me wrong... ive been die hard AE since the first day i first dropped an RC car on the track. BUT when i got into TC and started having to compare variations in products for consistent repeatable handling... AE springs went in the trash.
03-09-2012, 09:50 PM
#13
Oh i understand perfectly. No need.
'... misinformation stating that only wire diameter will change the spring rate of a compression spring.'
To be sure we are on the same page, by spring rate, you are referring to the actual numerical value of the spring... right? To me it sounds like you are defining a compounding effect of compression.
That in turn sounds like you are telling me that ALL linear compression springs are progressive in nature? How is this so when the entire spring, regardless of how many coils are present, bears the same load (not to mention weaken as they are compressed... all flexible materials do, thats why materials like Delrin break, and steel bends)? All coils are 'active' once under load. They remain active as a unit (a singular unit) unless compressed as one (basically becoming a bumpstop).
'... misinformation stating that only wire diameter will change the spring rate of a compression spring.'
To be sure we are on the same page, by spring rate, you are referring to the actual numerical value of the spring... right? To me it sounds like you are defining a compounding effect of compression.
That in turn sounds like you are telling me that ALL linear compression springs are progressive in nature? How is this so when the entire spring, regardless of how many coils are present, bears the same load (not to mention weaken as they are compressed... all flexible materials do, thats why materials like Delrin break, and steel bends)? All coils are 'active' once under load. They remain active as a unit (a singular unit) unless compressed as one (basically becoming a bumpstop).
To take a stab at your last paragraph, the material shouldn't 'weaken' when compressed as long as the load does not cause the stress in the spring to go above the linear elastice region of the material, in which once it goes outside this region the material has plastically deformed and will no longer return to its original shape ( like when you stretch a spring too far and it doesn't go back to its originally shape). Additionally, if you stretch the material (spring) much further after this and the stress of the spring reachs the ultimate tensile strength of the material, then the spring will break. We don't usually see this in compression springs but rather may eventually fatigue a spring causing it to break, which is a result of imperections in the material or operating outside the range of the materials fatigue strength. Our springs we use in RC are also ground and squared end springs which results in the loss of 2 active coils (so they are not all active).
