LocostUSA.com

I’m still mulling over the rest of your comment, but thoroughly want to grasp this concept before making a complete fool of myself. Lol.

How would a 2:1 ratio (2” of wheel travel to 1” of suspension travel) mean the rate is 1/4 on the shock? Isn’t that like saying a 200 lbs on one end of a teeter totter would take 800 lbs on the other if placed in the middle to sit level. What am I missing? Doesn’t seem right to me, but I’ve never designed suspension or played with software for it yet so don’t hate on me. Hahaha

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If it’s not custom, I don’t want to hear about it!

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Willy’s Hayabusa Build Log

This is the important part, even if perhaps not the most clearly worded:
Put into more application based terms: If you move the wheel 1 inch in the described 2:1 ratio system, that means you have compressed the spring 1/2 inch. With a 450 lb/in spring, that means the spring is actually exerting 225 pounds of force. But because the wheel also still has a 2:1 leverage advantage, it only takes 112.5 pounds of force at the wheel to equal it.

Don't worry about making a fool out of yourself...I pretty much do that on a daily basis.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Read everything (including the links) before your post.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I did. Please find where I've misunderstood you, and walk me through it like I'm 5.Rocker Output = Spring input Rate / (Rocker Ratio^2)
Rocker Output = 450 / (2^2)
Rocker Output = 112.5


Assuming a 'not that bad' motion ratio of 1.25 from the combined control arm leverage and pushrod angle effects, which I'd actually argue is optimistic from what I've seen in your link and elsewhere, then the final output to the wheel based on your rocker ratio recommendation becomes:
Wheel Rate = Rocker Output / (Motion Ratio^2)
Wheel Rate = 112.5 / (1.25^2)
Wheel Rate = 72

_________________
-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Way back when I designed Midlana, I tried hard to incorporate bike shocks into the car and failed. I remember that the spring and shock combination couldn't be made to come up with a wheel rate (and travel) that I was happy with. Others seem to have had better luck. One enormous variable is what bike shock to pick; how do you choose? As I recall, I went with a fairly heavy touring bike with the thinking that it was closer to the weight range I was working with, but it didn't work out. Maybe I picked the wrong one.

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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/

I’m talking about replacing the appropriate rate spring and damper with something that isn’t by using a rocker. A 450# spring 225# in one inch of travel through a 2:1 rocker because the 450# only compresses a ½ inch, apples to apples. No effective angle, no lca motion ratio, no wheel rate, none of that. Very simple. The link is to help him figure out what the appropriate rate is in the first place before trying to adapt something other than that.

Also pushrods allow for better effective rates and motion ratios because they are so much thinner than a coilover.

Maybe you should try helping people in the first place instead of ignoring them, waiting for someone else to try to help them so you can try to pick it apart based on your personal problems. Let them decide who to believe and who is acting childish but nobody wants to hear the snotty bickering.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I'm running them front and rear on the MG. Fronts are CBR600F4i, Rears R1. I typically run the car at a wheelrate that sees around 2-2.5" of total suspension travel. I designed my bellcranks with slotted pushrod holes to allow for about .7Hz of ride frequency adjustment. For smooth trackdays it works great. For rougher tracks it is adequate and when I street drive the car it's firm but fine. I get another 1" or so of suspension travel when I run the MR to full soft. I am satisfied with their performance and will run them on future builds.

The biggest change you need to make to them is abandon all pre-load. For the shocks I used it was easy to us zipties to compress the springs and weld up the adjusters to give 0 preload. With the pre-load of 1/4-1/2" that these tend to have unless you are replicating the motorcycles progressive link geometry you wind up with a no or very minimal drop suspension. This may possibly be ok on a race only type car but the way the inside tire unloads with a no-droop suspension made my car darty on uneven roads. Once I removed the preload it's still firm like any car with a ~2.3-2.5 Hz suspension would be but it handles uneven roads fine.

For a true street car they may not work. As has been discussed because of the way Motion Ratio works if you are targeting longer more compliant suspension travels you wind up running out of travel. I've found the adjustments to work at least noticeably but have never dyno'd them so it's perception. I realize any suspension works if you don't let it but my car is pretty quick at trackdays and I am pretty confident the shocks are not the weakest link in the car's performance.

Here's the car running around Grattan which isn't the worlds smoothest track and includes a JUMP!
https://www.youtube.com/watch?v=FEwEMu5IaSs&t=34s

Photobucket has all my pictures hostage so I will work on trying to get more but here is one I liberated.

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MG midget bodied Locostish car in progress

Are you solving for the 'Y' force or the 'Z' force?...I have been interpreting your descriptions as all solving for 'Y' as the important output, but since 225 lbf is the correct answer for 'Z', maybe I have misunderstood what you've been trying to communicate.



Once you break down what you're saying to a more fundamental level so that I can better understand it, and get us back onto the same page, perhaps you might also be inclined to remove your unwarranted and unprovoked personal attack on me.

_________________
-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Now I'm confused. Are we confusing spring rates with spring forces?

Note there are now plenty of used quad/ATV shocks available new, used, or aftermarket, many sprung and valved for weights and shock travel in our general range. Some of the long-travel shocks could use rockers to *increase* their stroke. Or pick a shock for a light ATV and run two of them per corner.

@nocones

It says your car is 1800lbs correct? I’m surprised you were able to use bike shocks for that. (Even with the very low travel distance at the wheel) What springs are on them? I was planning to have my rockers cut on a laser with multiple adjustment holes as well.

_________________
If it’s not custom, I don’t want to hear about it!

Youtube Series

Willy’s Hayabusa Build Log

Velix
I've had good success with waterjet cutting as well. It's cheaper here.

Bobber - Where is where?? You do not show a location!

Okay - Motion ratio and bellcrank/rocker ratio are different things.

Bellcrank ratio is shock travel vs pushrod travel and works on the square.

Motion ratio is shock travel vs wheel travel and still works on the square. Motion ratio is what is important!!! The center of the tire contact patch travel is the needed dimension as camber change across the tire contact patch can change the actual measurement.

Example - one inch of shock travel equals 3 inches of wheel travel. The motion ratio would be 3:1 or 1:3 depending how you look at it. The spring would have to be 9 times stiffer (3 squared) than the wheel rate. Say you wanted a wheel rate of 200# per inch of wheel travel then an 1800# spring would be required!!!!

I designed the Wycked7 with a wheel rate equal to the load on each corner without driver/passengers. If I recall correctly, the car weighed 1460#. The front was about 700# so each front corner carried 350# less the weight of the wheel/tire/upright/brake and such. Say 290#, so I designed for a 290# wheel rate. This gives about 1 inch droop. I wanted the car to ride low, so I figured 3 inches of ground clearance at the front. 3 inches of total travel with a shock that gave about 1.75 inches of travel before the bump stop. So I figured 2 inches of shock travel gave 4 inches of wheel travel (1 inch droop plus 3 inches of bump) to keep the car off the pavement in most bad situations. A motion ratio of 1:2 gave a spring rate 4 times (2 squared) the wheel rate for a spring rate of (290# times 4) equaling an 1160# spring. Needless to say the shocks were set on full hard. The ride was quite good!

All cars have a motion ratio greater than 1 and this needs to be figured out to know what spring to use.

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When you're racing, it's life. Anything that happens before or after is just waiting -- Steve McQueen from LeMans

My build log viewtopic.php?f=36&t=10658&start=0 NOW NAMED =The Wycked 7

My other build log viewtopic.php?f=18&t=15162 The Skayt'R6

San Diego
Waterjet West
Stewert Racing & WaterJet Cutting

My car is ~1800lbs with driver. I'm running the stock springs. Fronts are ~800lbs/in and rears are ~600lbs.

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MG midget bodied Locostish car in progress