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Suspension gurus! Help!!!

I'm going to order springs and dampers for the car soon, but I need someone to tell me whether my thinking is correct for the damper travel requirements.

As far as I can tell, here is how things should be:

- I know that the dampers can only compress a certain amount before the chassis hits the ground (ride height 4", so say 3-3.5" MAX compression)

- It seems to me that the initial compression of the spring (ie. as you lower the car from a jack) is a product of two things. 1) The pre-tension of the spring and 2) the ratio of spring rate to car weight on that spring (as represented by the natural frequency).

- The natural frequency determines the MAX rebound, since this is the initial compression under conditions of no pre-tension. In my case, a natural frequency of ~1.6 (front) gives an initial drop of around 3.5".

- There is no point in having a damper which has a much greater travel than the maximum rebound and compression figures. 6.5" in my case.


Does this sounds correct? If I get a damper with more than 6.5" of travel, the only difference is that I will need to add a bump-stop to make sure that the chassis doesn't hit the road?

(is this why some race cars have those mini-springs in the dampers? To always keep some pre-tension?)

Thanks everyone for your help!!!!

BTW, I'm planning on Bilstein ASNs with Hypercoil springs. Had great experiences with Bilstein in the past - does anyone have recommendations of who to get them from?

Thanks again,

Glenn

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Those mini springs can have several uses. Some use them just to keep the springs tight at full droop while others use them as part of the total spring rates.

I've used them on cars as a way to get a variable rate. The first inch of travel on the lighter spring which makes it track better on rough surfaces after which it brings into play a higher rate of spring than I could comfortably run on the street otherwise.

The transition between the 2 springs isn't abrupt, except upon major events like hitting a pothole, as you might think since there is some action on the main spring prior to the little spring binding.

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

Quick update!

Not much progress over the last two months (on the car, that is, although I know an awful lot more about hydrology now) but htere have been a couple little projects on a free Saturday morning or two.

The rad mounts are basically done, and I'm pretty happy with how it is located, with enough room for ducting, a proper diffuser and a good amount of trunk space.



Apart from that, another sheet metal panel is in near the firewall, and I've bought some carbon fibre and resin to start making the actual brackets for the radiator and other pieces. The turbo adaptor is also all nicely ported now, and welded.



Maybe I'll order some springs in time for the Christmas break, and get it fully rolling then. Or I'll get the megasquirt three hooked up and fire it up!!!

Ambitious, but you never know, updates in a couple more months.

Glenn

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A hydrology expert now, are ya? Cool.... Did they teach you about that great underground river that people are always telling me about when we're drilling? I been in and around the drilling business since 1977 and ain't found that damned river yet. Still lookin'...

I'd vote for setting up the MegaSquirt and getting the engine to fire off a few times. Nothing gets the momentum going like hearing that engine running!

Keep after it, Bro... And keep the updates coming.

JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

Hi Glenn,

Signing up to follow this thread as I am keen to see where you go with the C27A as I have one in the back of Lancia Stratos replica I am currently rebuilding. I was musing replacing it but may keep it in place for a while if a few more horses can be coaxed from it.

Not sure how much help it is but the Ginetta G27 used the Passat rad and I think they were all pretty similar right through the range I run a 4.0L V8 through mine at 240BHP and no cooling issues but its pretty cool in the UK.

Nice build

Sounds like you've got an awesome garage there, Darkspeed! Good to know about the radiator, although I think I've changed my mind and will likely mount it at the front... although it was going to be pretty cool (har har) having it at the rear, it just makes more sense to keep it at the front, especially now that I see how much space I have to work with.

Well, there has been a little bit of progress at least, despite all the reasons not to! I’ve managed to get the chassis rolling (woohoo!). I splurged for the prestigious 2x2 dampers, as I figure the lowly Bilsteins can wait until it is almost road worthy, but it is awesome to be able to push it around and steer.





In other news, I’ve picked up a throttle pedal and modified it as necessary today. It took a while to figure out how to get it to fit properly, but it should be pretty easy to mount it on the firewall next weekend. And in case anyone is wondering, yes, I made a note of the motion ratio changes as I modified the pedal! It should be around two inches of travel, and I’m hoping to rig it so that it has a softer initial opening.



Handbrake work has been difficult, but a solution has likely been found. The Supra one is massive and strong (as is everything from that car) but should work with some slight modification. The biggest issue is having some clearance around the transmission, but if I just run a bare cable it will have room to spare.

Wiring work is also going ahead, with half the engine figured out! I think this will be the next task after the throttle and handbrake – I’m keen to get the engine running!



Finally, some thoughts on the roll hoops. I have access to some bending equipment and oxy-acetylene, but have no experience with it. I figure I’ll give it a shot and see what happens, but I may need to seek advice on how/ where to get it done. It is really tempting to bolt them in, especially as clearance for the fuel tank might be difficult, but if I can weld it I will. I especially need to re-check all of the requirements for SCCA etc. to make sure that I don’t have to re-do it later on. I am still undecided; might end up with a full roll-cage, but would like to have an open-top car.

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Agree with reviewing the SCCA requirements. The little hoop is more of a stylistic device than one to protect your head. The SCCA GCR has great guidance on fabricating a proper (full width) roll bar, or cage if you so choose. I went with the latter and designed the car around it rather than adding it on as an afterthought. See sig for ideas.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

After seeing a guy flip a stock Nissan Sentra on its' A-pillar at a Bluefield Airport runway autocross, using wheels shod with sticky Hoosier A6's, this made me think long and hard about a roll hoop. The roll hoop doesn't necessarily need to be a safety feature only. I went with 1.75" OD tubing with 0.135" wall for the main roll hoop, and is loaded as a stressed member supporting the rear engine cradle, floor structure, and inputting control arm members, and loads from shock tabs.

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There is no such thing as mechanical failure, only a lack of attention to detail.

Well, good-news bad-news!

Actually, it’s all good news for the locost. I’ve found wheels! 18x10” with (old) 285/35s. They cost more than when they were new! Front offset might be a bit much, so I’m not sure if I will keep them for sure.




Luckily, more was included in the purchase price - they came with a 370 hp autocross-ready Talon. This should reduce some of the pressure to quickly get the Locost finished so that I can go racing again. This car has been around the community for a while, is well-known and very fast. I’ve wanted to buy this car for about six years, and now was finally the chance.



Time to stick some tires on it and have fun over the summer! Needs a couple small things... the boost controller is a bit flaky, so it will occasionally boost over 35 lbs rather than (just) 25. This is remarkably terrifying – the world approaches very quickly. I also noticed that the front rotors are cracked around each of the drilled holes, so those will get replaced with solid ones! Other than those minor points, it’s a beaut.



Air-water intercooler, meth-H2O injection, cams, 16G turbo, Shep transmission, this is going to be such a blast. It's been many years since I first drove this thanks to the kindness of the previous owner, I can't really believe that it's mine now!

The locost will get finished, but I’m glad I won’t have to wait years to be out on track in a competitive car.

Glenn

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370hp Talon

Geez that'll be a blast to drive.

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Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

Nice addition to the family! I used to have a 1G DSM GSX turbo. I know what you mean, boost is intoxicating, and it's REALLY easy to get greedy with the boost. Toss in some E85, and it's rather easy to up the boost and advance spark timing.

I believe the 4G63T in the DSM is the same as in vintage Evos.

I know what you mean in wanting to scratch that itch for driving a fast car right now, as cutting/grinding/welding metal is not as much fun as holding a 4WD powersliding drift on corner exit at an autocross.

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There is no such thing as mechanical failure, only a lack of attention to detail.

I'm another builder using a Honda engine (F22C from S2000) and Supra Suspension. Good luck with the build.

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2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558

Hi Glenn,

I'm sorry that I'm just coming across your build thread now. I am the one who built the Locost that you took that fantastic picture of! It was a nice surprise to come across it in your thread. I never made a build log thread for the car, but I did make a photo gallery of the build. Here is a link to it:

https://plus.google.com/photos/10397358 ... banner=pwa

I live on the mainland (Surrey) and started building the car in 2004 and finished it in 2007. I had a lot of fun with it over the years but eventually got the itch to build something different, so I sold the car last May to Chris in Sydney, who has been racing it. A highlight for me was last year when I came over to the island and rode shotgun in it while the new owner raced it around the track. Good times!

My in-laws live in Saanich, so I end up heading there a few times a year. It would be great to stop by sometime and check out your build. I like the unconventional route that you are taking with it.

I'm about 1 year into my new scratch built car project, which will take a few years to complete, given that it is quite a bit involved than the Locost. Here is a link to the build thread.

viewtopic.php?f=36&t=17167

Mark

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Photo gallery of my completed Locost:
https://plus.google.com/photos/10397358 ... banner=pwa

Mark, I look forward to following your build! Looks like another fun project.



Awesome. I had a friend who was considering selling his S2000 drivetrain, but it never worked out. That should be an absolute blast!

No Locost progress to report yet, but it was the first autocross with the new car today. Manual boost controller is working well (only ~19 lbs rather than 25, figure about 300 at the crank). Rear shocks are unfortunately blown, but otherwise it is great. Bit more understeer than I would like, but that could just be me getting used to such a nose-heavy car.

http://youtu.be/z1XoUtLL0ko

Glenn

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It's for sale! About time too - my priorities have simply shifted over the years, and it's time to let someone else finish this up. Not asking for much, just enough to stop it from being parted and scrapped.

Let me know if there are any questions! Would love to find a good home after all of the hours I put into this!

Glenn

https://www.locostusa.com/forums/viewtopic.php?f=40&t=19548

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