Landracing Forum
Bonneville Salt Flats Discussion => SCTA Rule Questions => Topic started by: awelker on October 29, 2007, 04:34:42 PM
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The rulebook simply states on shock per sprung wheel. I would like to keep the shocks on my lakester inside the body and simply mounted to the solid front axle. The shocks will lose some effectiveness by being further from the wheel but I can compensate with the type of shock I use and the mounted angle. Does anyone see a problem with this setup?
Thanks, Andy
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The rulebook simply states on shock per sprung wheel. I would like to keep the shocks on my lakester inside the body and simply mounted to the solid front axle. The shocks will lose some effectiveness by being further from the wheel but I can compensate with the type of shock I use and the mounted angle. Does anyone see a problem with this setup?
Thanks, Andy
If mounted inboard with very little travel you might want to come up with some type of lever system so that they have more travel if you think they won't be effective due to a small amount of travel.
Good luck,
Sum
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our shocks are in the body, made for about 4 inches of travel, mounted to the axle, about a foot inboard of the tire. Seem to work OK, and I'm sure better than no suspension.
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The rulebook simply states on shock per sprung wheel. I would like to keep the shocks on my lakester inside the body and simply mounted to the solid front axle. The shocks will lose some effectiveness by being further from the wheel but I can compensate with the type of shock I use and the mounted angle. Does anyone see a problem with this setup?
Thanks, Andy
If mounted inboard with very little travel you might want to come up with some type of lever system so that they have more travel if you think they won't be effective due to a small amount of travel.
Good luck,
Sum
I'm not sure I follow all this exactly, but mountain bike rear suspensions typically use rocker arms to change the ratio. a small lightweight 1 to 2" travel shock can give anywhere from 4 to 6" of rear travel (and a 6" rear travel bike is considered long travel)
There is a limit to the ratio you can use, as at some point you're overly abusing the shock.
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I run a roadster with a drop tube axel in front. Both shocks are mounted verticle behind the Duece grille shell. Yes you can compensate for the inboard mounting with the shock you choose. My roadster runs 202 MPH and the only reason it doesent go faster is the HP I have. It drives beautifly at 200. I would say yes mount them inside the bodywork. Good luck Vince
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What type of spring are you using? How much travel are you going to have. Very little is better than a lot of travel. Remember a shock is really a spring oscillation damper. If you are using air bags then the shocks are there just to meet the rule. Doug Odom in big ditch
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My shocks are mounted inside the frame and that resulted in narrow suspension platform in the front. 6" between the upper mounting points compared to a 40" tread width. I am using an anti roll bar in the front to avoid the car noseing over and unloading a rear tire in the event that I have to drive the car in some path other than straight! I will also mount an anti roll bar in the rear. Does anyone disagree with this approach??
BHarmon
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My shocks are mounted inside the frame and that resulted in narrow suspension platform in the front. 6" between the upper mounting points compared to a 40" tread width. I am using an anti roll bar in the front to avoid the car nosing over and unloading a rear tire in the event that I have to drive the car in some path other than straight! I will also mount an anti roll bar in the rear. Does anyone disagree with this approach??
BHarmon
If I'm reading this right you are saying that the wheels are 40 inches apart and the shocks are 6 inches apart??? If so and lets say you have 1 inch of travel at the wheel/tire how much is the shock going to move?? Enough to really do any damping?
If this is the case you've meet the requirements of the rule by having a shock, but I really doubt they will actually do anything, which is probably fine if you are running a good course. If the course isn't good you might have a problem, but you at least won't be alone.
I've gone overboard to try and be able to run on marginal courses and it will hurt on good courses as suspension results in more frontal area, but I guess we make our choices and live with them.
c ya,
Sum
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Sum,
The bottom of the coil over shocks mount 14" apart and 4.0" below the center of the axle, any wider would be outside the frame. This gives you an idea of the shock angle, approx. 30 deg. To answer your question the one inch of travel at the wheel will be approx. .700 at the shock. I have not had the car setting on the ground yet but I will be able tell how effective this suspension is when I do and will change spring rates as necessary. I attached an early construction photo before the anti roll bar was installed.
Thank you for your input,
BHarmon
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Sum,
The bottom of the coil over shocks mount 14" apart and 4.0" below the center of the axle, any wider would be outside the frame. This gives you an idea of the shock angle, approx. 30 deg. To answer your question the one inch of travel at the wheel will be approx. .700 at the shock. I have not had the car setting on the ground yet but I will be able tell how effective this suspension is when I do and will change spring rates as necessary. I attached an early construction photo before the anti roll bar was installed.
Thank you for your input,
BHarmon
Is there a reason you want your coilovers at an angle. That 30 deg. angle is probably cutting the .7 movement at the coilover down to about .5 inch. and will make your spring rate about 75% of the spring rate vs. it being more vertical.
http://www.proshocks.com/calcs/anglefirst.htm
The car isn't probably going to be that heavy in the front, but I would personally build brackets that would locate the ends of the coilovers in double shear. I know there are a lot of street rods out there mounted in single shear, but I'm not a fan of that.
Looks like you are getting lots done, good for you,
Sum
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This is the front of my roadster as built by Al Holoway some years ago. Torsion bars along the frame, rocker arms behind the axle. Clean, out of the way, and effective.
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Andy if you mount a Ford lever shock to your axle with the arm vertical and traveling side to side and a link to the frame it would dampen body roll and the wheels over bumps . You would have to fill the shock off the car .
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Re: linked calculator
Where did they get those values?
Cosine of 45° angle is .707 of vertical, they have .50; 30° angle is .866, they have .75; 10° angle is .985, they have .96 etc. Results should be 1 ÷ cosine for rate increase, or 1.414, 1.155, 1.015, etc.
???
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There's more reasons to use linkage:
1. it's adjustable without taking the shock off/apart.
2. doesn't have to be linear - you can have soft ride for the first 2" and excellent bottom-out control for the remainder (rising rate).
3. if travel is limited, the shock valving won't do anything - fluid displacement requires some small amount of motion before anything happens, so doubling the distance has considerably more than 2 × the effect.
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'Member this, the closer to the WHEEL the shock mount is the more effective it wll be. Be it linkage or direct.
Huh, Rex?
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There's more reasons to use linkage:
1. it's adjustable without taking the shock off/apart.
2. doesn't have to be linear - you can have soft ride for the first 2" and excellent bottom-out control for the remainder (rising rate).
3. if travel is limited, the shock valving won't do anything - fluid displacement requires some small amount of motion before anything happens, so doubling the distance has considerably more than 2 × the effect.
That is why I've gone to a lot work to get more shock travel and have it easily adjustable:
(http://purplesagetradingpost.com/sumner/bvillecar-2/fr-shk-mt-7.jpg)
http://purplesagetradingpost.com/sumner/bvillecar-2/construction%20page-71.html
I'm having problems though setting the dampening rate on these shocks though. I think I'll send them back to Kent and ask for a refund,
Sum
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Sum,
How much did Kent charge you for those wood shocks?? :-D
harv
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I hear he got them for free from Kent -- but in exchange he's got to put AirTech stickers on his refrigerator door, right next to the kids kindergarten drawings.
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There's more reasons to use linkage:
1. it's adjustable without taking the shock off/apart.
2. doesn't have to be linear - you can have soft ride for the first 2" and excellent bottom-out control for the remainder (rising rate).
3. if travel is limited, the shock valving won't do anything - fluid displacement requires some small amount of motion before anything happens, so doubling the distance has considerably more than 2 × the effect.
Add to number 3 that stiction (the force required "unstick" the shock from any static point) is less of a factor with longer travel shocks.
I have no idea about this effect in LSR, but in both superbikes and sports cars on road courses progressiveness had real limits. As we went faster, the "soft" travel would "load up" and we would end up riding on just the harder half. It has to do with the rebound damping getting ahead of the preload and the whole system pumping itself down. We ended up running almost linear ratios.
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Main thing they are concered about ---is if you have them mounted securely---If mine pass you should not have any trouble-- mine are mouned in the center of the frame and angled out board and mounted to the axle---inboard---my lakester is 24" wide
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refund..?...what the heck is that..LOL
kent
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Very old thread, so I assume Andy came up with a workable shock absorber scheme.
Reading his original question, I couldn't help but have a mental picture of Houdailles (turn the clock back sixty years or so here!) mounted out of the breeze, but with arms shortened in proportion to their relocation toward the car's center- thus retaining damping forces (at the wheels) in the desired ballpark range. Forgive me for thinking-out-loud about old-school-appearing solutions... :-)