spring rate |
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harshnarayanin
Bolt Sorter Joined: Sep/16/2010 Status: Offline Points: 4 |
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Posted: Sep/16/2010 at 11:26am |
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What should be the appropriate spring rate for the front suspension?
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RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
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If you drop a check in my mailbox, I can help do the engineering of your car too :)
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-Ron George
Systems Engineer (Cummins Turbo) |
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Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
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x2... your going to school to be an engineer.... Build something, test it, and if it doesn't work change it.... Technicians do what your asking, get out of that mind set, it won't get you far. |
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SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
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RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
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I have to stop and do the Robert DeNiro face now. "Are you talkin to me?" |
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-Ron George
Systems Engineer (Cummins Turbo) |
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Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
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No, the OP |
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SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
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harshnarayanin
Bolt Sorter Joined: Sep/16/2010 Status: Offline Points: 4 |
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I know i'm here to learn but if u could give me slight hint whether i'm on the right path or not it would be great. I calculated spring rate by considering the g force that the suspension would experience after jumping from a 6 feet height and also took into consideration the motion ratio , the weight distribution on the fornt wheels and the amount of spring travel that i want on my suspension. Please understand as my college is doing this for the 1st time i just wanted to be sure.
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EAD Motorsports
Welding Master Joined: May/26/2009 Status: Offline Points: 109 |
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Why did you make two threads for one topic? Doing so clutters up the forum and makes it harder for future users to find usable information.
With respect to your question, you're leaving damping out of your formulas. Your calculated spring rate will likely be far too stiff when you don't account for damping.
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Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
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Do you have any idea what kind of shocks you plan on running? Coil-over, air-shock, by-pass... Any particular manufacturer you are planning on running? Unless you plan on going to Works, or plan on making your own shocks, and have spring made for you/buying them off the shelf, your relatively constrained to what spring rates you can run. There aren't many manufacturers out there that will make a shock specifically for our application, you can get close, but to get really close you have to be willing to dedicate some serious time to R&D and testing. For example, if you go with a Fox, like 50% of the teams out there, you adjust the knob on the outside of the body, and thats about all you can you do (depending on which model you get). If you go the air-shock route, you can tune it to be much closer to your needs, but you have to invest a substantial amount of time into testing, and a ridiculous learning curve. Coil-overs are slightly simpler, and *if* you can determine what your optimal spring rate is, and have your drivers buy in on it, then you can get a shock that will meet that rate. The issue with this is you have to go to Works, or someone like works to get your shocks custom made; or if your bad ass like OSU you can make your own shocks. Edited by Red_Beard - Sep/16/2010 at 4:31pm |
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SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
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Rob71zilla
Welding Master Joined: Feb/09/2009 Location: Utica, NY Status: Offline Points: 324 |
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Being a first year team, I would suggest using some sort of air shocks unless you have someone that is highly educated in the topic (which it sounds like you don't) Air shocks will give you any spring rate you want (within reason) and are easy to design around. Fox Floats have a 0-150psi range, they are only compression adjustable but for a first year team I think that is a great starting point. Being a first year team, you probably don't have a large budget so they will help with that too.
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Robbie
Former Team Captain SUNY Institute of Technology Current Engineer for Remington Arms A Redline a day keeps the carbon away. |
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Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
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I am going to strongly disagree with you on this one. Call up works and send them all your design parameters, and let them build a shock for your application. We did that for 5+ years, and the cars that we still have around the shop with works shocks are awesome cars, mostly due to the shock set-ups they have. |
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SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
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collinskl1
Baja Godfather Joined: Jan/21/2009 Location: Saginaw, MI Status: Offline Points: 1056 |
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This may not be what a lot of more established teams do, but I know my team got the Polaris discount special Fox Podium X shocks with a few different spring combinations and called it good. We did some analysis and testing to ballpark the rates we liked, and mainly focused on engineering a robust car before we spent a lot of time on tuning suspension...
I think there is much more to a first year car than designing the perfect shock package... one of our cars rode somewhat like a dumptruck, but it was very stout.
All this is to say yes, suspension dynamics are important, but a strong car that will last the whole event so you can utilize the suspension is more important for a new team.
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Kyle Collins
Lipscomb University Alumni 2x Project Manager Nexteer Automotive Product Engineer, Electronic Power Steering ... and the 8th simple machine: a bigger hammer. |
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Rob71zilla
Welding Master Joined: Feb/09/2009 Location: Utica, NY Status: Offline Points: 324 |
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Ok, fair enough. I don't know anything about Works but I don't think you can argue that using air shocks to save some design time and money is a bad idea for a new team.
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Robbie
Former Team Captain SUNY Institute of Technology Current Engineer for Remington Arms A Redline a day keeps the carbon away. |
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Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
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I can argue that exact point because I was the teams "shock guy" for 4 years, and that whole time we ran air-shocks.... Not externally adjustable ones, but true air shocks where you had to take them apart to tune them. |
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SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
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dillon_b12
Baja Godfather Joined: Nov/15/2008 Status: Offline Points: 781 |
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Be prepared for a 3+ hour conversation if you call Works and speak with a guy named "Sandy".
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Unproductive
Milling Master Joined: Jul/11/2009 Location: Rochester NY Status: Offline Points: 66 |
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Oddly enough, the guy to talk to at Ryde Fx is also named sandy.
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-Bob
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RonGeorge
Welding Master Joined: Apr/17/2010 Location: Indiana Status: Offline Points: 286 |
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Just did a quick search for Works Shocks. Well what do you know. People are pissed off with their products. http://www.horizonsunlimited.com/hubb/equipment-reviews/works-shocks-dont-work-23959 I dont know about others but with Fox Shocks, you get to choose your own "spring size" but by size, I'm assuming they mean rate, free length and so on. Edited by RonGeorge - Sep/18/2010 at 3:53pm |
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-Ron George
Systems Engineer (Cummins Turbo) |
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Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
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What I know is they have worked us in the past. We ran their shocks for something like 5 years with no issues. Always good service, and a quality product, but I can't speak for their current service since we don't use them anymore. |
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SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
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ErikHardy
Baja Godfather Joined: Apr/12/2010 Location: Hood, Flint, MI Status: Offline Points: 939 |
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Which shocks from Works were you running? We have some old coil-overs (roughly 5.5" travel to the bump stop) I found in the closet that I am considering using for the front suspension.
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Red_Beard
Organizer Joined: May/14/2009 Location: Bellingham, WA Status: Offline Points: 269 |
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We have two styles, but I couldn't tell ya what length they are, but that sounds about right 5"-5.5". I'm sure the guys still at school are reading this and will chime in what lengths we have. |
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SDSM&T 09-10 Team Lead
2nd & 9th Baja West Project Engineer Matrix Service - Bellingham, WA |
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