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PostPosted: Sat Dec 19, 2020 6:11 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
So how do I figure all this out for a base line? This one was tuff for me as I had to learn a lot and go from what I thought to what worked and then how to put on paper. What a head scratcher and a lot of test time to figure out not being an engineer but a Back Yard Hacker. They would however have a good laugh at my expense (HI Lee). I read a lot of books and played with the numbers until it made since and fell into a line I could follow. Again thanks to the wife, She said you’re making that a lot harder than it has to and don’t touch mine until I tell you to “URRRRRR”. I took all this information and figured out how to apply it to my machine. Right or wrong I have no idea however it does tell me which way to go with things without a lot of trial and error. In the spirit of sharing that is what I am doing here.

Everything I read keeps leading me to ride frequency or suspension frequency etc never finding what I was looking for or even someone to talk with me about it. Some kind of black art bull crap. That just drove me harder again no pun intended. This is not a Car,Truck,Quad,UTV etc, so why. What I did find is there is a relationship to this and the under over steer question in theory. The balance of this front to rear can determine it tenacity to over/under steer. So how do I adapt this to a Back Yard Hacked up FL 400 Pilot. Testing and adjusting till I got a base line for my machine. I found I needed to learn even more and adjust my way of thinking, hard for an old man to do. I need info and a lot of it. I needed weights front and rear and % of it, sprung, un sprung, shock angles motion ratios, spring rate angular force etc to even start to put something on paper that would work as a guide. Needed to learn what and how to calculate a ride frequency let alone what it is. Those engineer use a lot of fancy terms and my son in law is one, so he got to laugh at me. I will save you the lesson.

I use a 50/50 set up as neutral as I can with base line suspension setting and use the number 1 as the neutral line and then either go over or under with a change. So 50% sag, base set up on caster,cambe, toe,scrub, rake, rates,balance,track width, wheel load, and so on for given results and see where each falls on this line. See why it took me so long and blew my mind. The Ratio between the front and rear which will provide a number below or above which tells me which way and how much to go for how much either way from neutral. If I go out and it pushes on entry (under steer) I can look at my chart and make a change. Let’s look at an example now for fun.
I will first set one up with my listed 50/50 (Neutral) and then note the spring’s rate for this example. Let’s use Dual Rate in front and Dual in rear, Front 350 /240 and Rear 95/300. The combined rate in front will be 142 and rear 72. SO I enter this into the chart. At ride height the number comes out as .968. So the tendency is to under steer. Now let’s look at what happens when it crosses over to the final rates or take set. The number is now 1.520; it switches over to an over steer with the tendency to come around on me. So how to change IF I test I find this to be true. I find that the 1.520 is too much. First let’s change the rear main spring and compare the numbers. Change the rear main spring to a 200 from the 300 and leave the rest alone. The (142/72) .968/ (95/300)1.520 is now (142/64).915 / (95/200) 1.241, OH My What Have I Done. How do I fix this and dial it in if I find this to be an issue. I can simply enter rates and change the ratio aspect. Look at what all is involved to get this number to start with as each discussed prior can change these numbers for given rates. This is nothing more than a way to put on paper.


Attachments:
Resize of Example F 350 240  R 95 300.jpg
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Resize of Example F 350 240  R 95 200.jpg
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example 142 64.jpg
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example 240 200.jpg
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PostPosted: Sat Dec 19, 2020 6:24 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
Now we know why engineers use computers now.
Hi Lee. I don't think he will ever see this because he doesn't show up here anymore --- unfortunately.
As for me, I drive what I got because I'm no suspension expert and the math involved in the above adnoh charts/threads is the proof enough for me. But it is interesting.
Because I ride in the mountains and the roads are rough I don't think I would even notice over/understeer LOL. The buggies are all over the road trying to miss pot holes, rocks, trees, steep drop offs. But I do notice that you have to drive them using the rear brakes to "steer" because of the lock diff. AVGAS won't help this issue.
CO


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PostPosted: Sun Dec 20, 2020 3:13 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
CO love the AV GAS comment.

We all use the rear brake to steer no doubt about it. When I tested stuff this summer I laid out a track to follow so each could be seat of pant evaluation for each set up. I can tell you this info does effect the rear brake steer effect at speed. Now for big rocks try going around them. I fond in one corner it was an off camber right hander greater than 90 degrees. I over shot it almost every time. As I try to dial it in I started with turn in and had to use the CO method before entry so I could accelerate into and thru that corner. It took me a few attempts to get the brake to over steer so I could get into the corner. Basically just to dam slow. So I found and issue in the DCP set up I had a terrible time to correct with out this steering input. I mean I tried everything, set up outside, tap front to unload rear, trail brake on entry or just slow the F down etc. Nothing worked except the CO method. Yes pitch it in square it off and accelerate. Doing this off camber is taking a chance of roll over though and felt a little squirley. SO I tried changing the adjusters and cross over's to take set sooner and reduce body role which it did the trade off was it upset it every where else to much. So I had to learn a few things to resolve and this is what I came up with. If you go back and look at some of my ride stuff during clutch setup. I played with spring, GC, suspension static setting etc as well. It seamed like I was all over the place on what to set things at. I was trying to teach my self cause and effect.
For those not sure what an off camber is. Think about it this way. The corner was to the right and the slope was to the left. Turn right and lean hard left. Your machine body role when it takes set is at a fixed angle to the) degree flat ground. Now take set and move that angle 20 degress more down hill. WOO HOOO, The angle will unload the machine. Now you have to wait for this weight to re-establish before you even think about getting on the gas. I have mine to take set on the rear cross over (stiffer rate) so if you take weight off it from set to the dual rate and continues to role then if to fast it goes over or crash. A least you will just push though the corner and over shoot it.

Now you see how pitching it in squaring it off works Pitch it in to take set on flatter ground and as it unloads you already change the angle of the machine relative to the angle of the corner machine and back on the gas. or just slow way down and turn. Now what if you did not know that was there, SURPRISE your could be fixing your machine. SO always pre run your trails before having fun.

I will show a picture of this is way of calculation using base line setting. You will see the dual rate set up and the combined rates and main rates. Each has a tendency which is auto populated based on the number 1 Under/Over. As described you can look at the two numbers arrowed up which represents the amount of change as it is loaded and in this example unloaded. The decrease shows it will push or have greater under-steer even if it was set before entry.
One thing this does not represent is damper valving and i I described above I changed the static valving to work however upset the ride. Time to find a happy medium or just slow down.


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Comparison example base line.jpg
Comparison example base line.jpg [ 63.72 KiB | Viewed 2403 times ]
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PostPosted: Sun Dec 20, 2020 3:22 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Hopefully you get the idea. Now lets look at what I did beside the pretty spring picture of the front triple rate zero pre load and the change in the rear to a zero pre load with a stiffer main. First of all it changed the height it set up off the ground and change the tire scub effect on track width an attitude adjustment effecting static suspension settings.
What did this do to the set up.

SEE PIC.

You can see the effect on the under steer as it loads and unloads. The seat of the pants says drive it in and gas the H out it. Yes add a click on the low speed compression and take one out of rebound. This should be painting a picture by now.


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Comparison example 1.jpg
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PostPosted: Sun Dec 20, 2020 3:24 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Now If I want to change lessen the effect or if it has issues else where what do I do. I can take out some low speed compression and quicken the rebound or ???.


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Comparison example 2.jpg
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PostPosted: Sun Dec 20, 2020 3:33 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
What a diff between the first and second adjustment. Now what if the first allows it to have to much over steer when I get back on the gas and the second not enough. You should be noticing change in springs and rates. This should provide a good all around balance based on the GC and damper (shock) valving.


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Comparison example 5.jpg
Comparison example 5.jpg [ 50.43 KiB | Viewed 2402 times ]
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PostPosted: Sun Dec 20, 2020 3:35 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Hope you can see how the number kinda jive with the babble. It took me a while to get to this point however I fell it was worth it. Be sure to compare the set up numbers to the right.


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PostPosted: Sun Dec 20, 2020 11:17 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
Are you making any allowances for chassis twist ??
If so how much ??

I know for a fact that the FL350 pulls the inside front wheel off the road when you go around a corner at speed.
CO


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PostPosted: Mon Dec 21, 2020 1:01 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
NO, as my back yard hacker skills are limited. I can however do a roll stiffness and roll couple calculation using the data I have. You must have noticed I had track width listed and the rest of the pictured calculation does not use it. Good spot. Just a driver uh.
Since were kinda going there the calculation (roll) can use a sway bar since the pilot does not have one I omit it. However it can be calculated now to get one. I doubt stock or mine would require one. That being said with the Dave-co set up and very light valving and rates I could see where one might apply there.

I should show in more detail the equations and numbers used so some one can build there own sheet to play with. I babel enough as it is.


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Machine info 1.jpg
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Machine info 2.jpg
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Machine info 3.jpg
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PostPosted: Mon Dec 21, 2020 1:04 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
With that any one can do it. As far as the wheel coming off the ground I set mine up not to do that. Never really liked that much roll. Maybe a drivers preference. Would like to hear yours and other thought on the matter of roll. All feel free to throw it out there for discussion.

Another item to point out or roll stiffness and tire lift. The roll calculation uses bump stop and with our long travels it has to roll a lot to hit the Bottom OUT Bumper or bump stop If you look at my shock pictures and notice the shaft in relation to this bumper and the take set at cross over. You will see how getting my front in the air in a turn is not likely unless I'm going over.

Roll stiffness;
For this we need:
Track width
Bump rate
Wheel rate
Motion Ratio
Sway Bar (omitted)

The for couple we use
Front roll stiffness
Total roll stiffness


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PostPosted: Mon Dec 21, 2020 3:42 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
adnoh wrote:
As far as the wheel coming off the ground I set mine up not to do that. Never really liked that much roll. Maybe a drivers preference. Would like to hear yours and other thought on the matter of roll. All feel free to throw it out there for discussion.


At the end of the day I drive what I got. I love working on these machines and building them but I get diarrhea of the pants when I have to spend money.
When I was still racing cars, one of the things we did on our formula car was to remove the sway bars before any race where it seemed like it might rain. It was amazing how much the grip level went up on the slicks but the body roll was the trade off. The reason this was done was because if even so much as one rain drop fell on the track when you're on slicks you're in trouble if you got a tight set up. I was actually able to keep the car on the track in the rain with slicks. I never bought rain tires for the formula car because I would just park it and call it a day. I wasn't racing for the championship with this car so it wasn't worth it to me.
A twisty chassis seems to have grip.
CO


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PostPosted: Tue Dec 22, 2020 12:48 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
CO, interesting thanks.


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PostPosted: Tue Dec 22, 2020 2:56 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
This must of been what happened to my race car:

Anti-roll (sway) bars

Which brings us to anti-roll/sway bars. A sway bar is a torsional spring (a fancy way of saying, “a spring that works by twisting”) which connects the suspension on one side of the car to the other. When the car goes over a bump and both sides compress, the bar simply rotates in its mounts and doesn’t add anything to the mix. However, when going around a corner, the outside suspension (which is compressing), now exerts a compression force on the inside spring (which is trying to extend) because the sway bar connects both sides, and this force resists body roll. So we have managed to reduce body roll without affecting bump compliance!

But of course, a problem arises. The stiffer the bar, the more weight is transferred across that axle, and the less grip that pair of tires makes.

This is a critical point to understand! When we use a stiffer sway bar, we increase the proportion of roll resistance on that end of the car, which (we established as a general rule) increases the weight transfer on that axle. We do not change the total amount of weight transfer across the entire vehicle, but we take some additional weight off that inside tire and distribute it to the other 3. This means we reduce grip for the pair of tires when we use a larger sway bar.

So, while there are good reasons for using larger sway bars, we must recognize that it always comes with a loss of grip on that axle.


In my case on the race car, removing the sway bar link increased my grip.
So is chassis twist really that bad on an oddy ??
It's (suspension) a very complex subject.
And how do we take into account that we run balloon tires ??
Taken from this site: https://www.beyondseattime.com/weight-t ... ll-part-2/
CO


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