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Thanks everyone for the replies.
Duuuuuuuude: I'm pretty sure its not chassis slap, it still looks new on the bottom. Was thinking, and forgot that my pistons are 5 hole 1.4f and 1.5r. So bigger and fewer holes should pack late if at all with higher wt oil, right? John Wallace2: It was the late 80s i was a kid in middle school, I ran 12th scale mod carpet oval. My dad was the pit man, I was a punk that would go off playing and chasing girls. My dad would get mad, he'd try and teach me about setup. Then I just showed up when I heard my heat called. Not to boast but, we did TQ and win A main all the time. I had 2 of 3 track records, and picked up a motor sponsor. Couldn't of done it with out my dad, im paying for it now. Just started in the hobby a year and a half ago, wow have things changed. My droop is even side to side, and from the local fast guy to get more steering into corner. I increased rear droop 1mm more than front, I know that's causing the rear to come up more. JsK: I hadn't changed anything from kit setup in the rear, except droop. So the sway bar was still 2.5mm links at the end. I can go down to 2.3mm which I plan to. I also was braking hard, I need to turn down my brake epa. I could put the videos on YouTube iifit would help to see. Thanks again everyone! That's also what I love about rc, the comrodity and willingness to help. |
Originally Posted by fredswain
(Post 12798783)
I was playing around with suspension geometry in CAD today to test a suspicion that I've had for a while in regards to shock orientation, standing them up vs laying them over more. I created a simple reference suspension with a set travel distance and then created 6 instances of it on screen. Then I started with a shock that was 90 degrees to the arm when fully compressed and started laying it over from there. The first 3 models were in this setup. The next 3 moved the shock position outward to the outer hinge pin with these 3 orientations showing a shock laying further and further down. I took angle measurements on the fully extended and fully compressed locations of each setup. Then I subtracted the lower number from the higher to show how many total degrees the shock changed in reference to the arm.
What I found on screen confirmed what I've always suspected but never bothered to verify until now. The most vertical setup gave me a 26 degree total orientation change between the arm and the shock. As I laid the shock over, this range got smaller and smaller. The most extreme example showed a mere 4 degree total change in relation to the arm. It is hard to describe all of this without a picture but basically the more vertical the shock is mounted, the more progressive the spring and dampening rate are with suspension compression. The more laid over the shock is, the less progressive they are. Edit: Yeah I'll throw a picture in here. Keep in mind this is just for illustrative purposes to display a concept. Have you done any testing that would confirm this specifically? Would be interesting to see actual shock dyno graphs at different angles. |
You've really got to question who writes those things. Just look at the data. It says everything.
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Originally Posted by old carpet rcr
(Post 12800777)
Thanks everyone for the replies.
Duuuuuuuude: I'm pretty sure its not chassis slap, it still looks new on the bottom. Was thinking, and forgot that my pistons are 5 hole 1.4f and 1.5r. So bigger and fewer holes should pack late if at all with higher wt oil, right? Honestly I haven't spent a whole lot of time messing with pistons. Our club has 4 tracks that we race at, each one is different, and I don't have the will to retune shocks for each one. I make small changes in roll center to suit the amount of traction there is and leave everything else alone. But...if the wheels are coming off the ground when you hit a bump and the chassis remains somewhat stable, the shock oil is not providing enough resistance to that movement. The opposite is true if you hit a bump and the whole rig flops around. In that instance the shock oil is providing too much resistance. Thicken the oil slightly and see if it improves. If it starts hurting performance in other areas of the track, stop, and back up a step. |
Old Carpet RCR Check both the front and rear sway bars to make sure they travel up and down freely without binding. I suppose if the rear sway bar is extremely tight (i.e., almost no free up or down motion that could cause the wheel to lift in the turn). I don't have a Losi but my TEKNO has two set screws on either side of the sway bar mount. I don't think I could get my sway bars too tight without stripping out the set screws. Yea I saw a lot of kids playing video games etc. at the Snowbirds and other big races while dad was playing with the car. I made my son do all the work on his cars - no work no drive! I helped with the setups, but now that he's a mechanical engineer, he tells me what to do.
PS make sure all the suspension parts move freely, not just the swaybars |
Duuuuuuuude: my apologies, I forgot to mention that the car is definitely unsettled. In the slo mo video, I can see the body, chassis and wing just rocking all over. I appreciate your advice.
John Wallace2: all the suspension is free, I have the sway bars set right. They are just free enough the ends fall by gravity. without being in the links of course. I think most of it has to do with me making the front softer for more steering, and leaving the back stiff. Doesn't help that my car is already unsettled going into the corner from my shocks having too stiff of dampening. Also, my brake adjustment is too high. I need to turn down my epa. Are you running your Tekno on the light side? My kids are interested in rc too. When they get old enough to have there own for the track, I'm on your page. No work no drive. Im really regretting not sticking with my dad in the pits. |
Originally Posted by fredswain
(Post 12800932)
You've really got to question who writes those things. Just look at the data. It says everything.
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It certainly has far less leverage down there and would absolutely require a stronger spring as a result. The point wasn't to set up a car like that but rather to look at the attitude change of the shock in relation to the arms. I think having a shock that is perpendicular is fine but it is meaningless without a reference. What is it in reference to, the ground? If so, how does that have any bearing on things without knowing what attitude the arms are at in relation to the ground? The one thing that is quite obvious is that a shock that is mounted more perpendicular to the arm travel is going to be more progressive than one that is leaned over farther. When evidence calls a belief into question, I don't automatically doubt the evidence but rather the rationale behind the belief. I need to know why. It certainly warrants further study but I will not proclaim it an error on the sole belief that a setup guide says otherwise. They get so many other things wrong!
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Originally Posted by fredswain
(Post 12802141)
It certainly has far less leverage down there and would absolutely require a stronger spring as a result. The point wasn't to set up a car like that but rather to look at the attitude change of the shock in relation to the arms. I think having a shock that is perpendicular is fine but it is meaningless without a reference. What is it in reference to, the ground? If so, how does that have any bearing on things without knowing what attitude the arms are at in relation to the ground? The one thing that is quite obvious is that a shock that is mounted more perpendicular to the arm travel is going to be more progressive than one that is leaned over farther. When evidence calls a belief into question, I don't automatically doubt the evidence but rather the rationale behind the belief. I need to know why. It certainly warrants further study but I will not proclaim it an error on the sole belief that a setup guide says otherwise. They get so many other things wrong!
I'm not arguing the point, I don't know enough about it to do that, but is it possible you are looking at the wrong angle to determine progressiveness? In particular, could it be the angle that is defined by the difference in possition of the shock that determines progressiveness? I'm at work & don't have access to drawing tools, so description is the best I can do currently. The expanded shock makes the hypotenuse (C), the compressed shock makes 1 side (B), the distance the shock end moves makes the other side (A). The angle I an refering to is opposite the shock end side (a). This angle increases as the shock is laid down. |
By looking at the angle from that side it would seem to hold true that it is more progressive as the shock is layed over but I'm not sure that's the correct way to look at it. I will admit that my assumption could be wrong which is why I mentioned that it deserves more study. I need to go play with an actual suspension a bit more to look at it a little closer.
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Originally Posted by fredswain
(Post 12802312)
By looking at the angle from that side it would seem to hold true that it is more progressive as the shock is layed over but I'm not sure that's the correct way to look at it. I will admit that my assumption could be wrong which is why I mentioned that it deserves more study. I need to go play with an actual suspension a bit more to look at it a little closer.
This looks like it is going to need some testing. Maybe build a rig that holds the arm/shock assembly upside down. Hang a weight off the end & measure how far the arm drops with the shock mounted in the up (down in this case :sneaky:) position. Then measure how far it moves with shock mounted in the layed down (up;)) position. I've got a personal theory theory that tapered pistons either don't change pack regardless of which way they are mounted (but provide nominally less pack in either direction than standard pistons) or they provide more pack mounted like this ^ by a VERY small margin. I convinced my son to test this for his science fair project. We're going to do the testing as soon as I finish this. I'll report back with our findings. |
Originally Posted by kwiksi
(Post 12794244)
Anybody have a quick explanation on what happens if you raise or lower both camberlinks on outside and inside at same time? Like say 2/2 washers vs 1/1 or 3/2 vs 2/1? More or less grip?
Anyone? |
OMG!! Just discovered this thread, I am only on page 12. I might have to print it out and have it for bedtime reading.
Nice job guys and it is nice to see that Fred is still around. Impressive, quite impressive. |
Originally Posted by old carpet rcr
(Post 12802047)
Duuuuuuuude: my apologies, I forgot to mention that the car is definitely unsettled. In the slo mo video, I can see the body, chassis and wing just rocking all over. I appreciate your advice.
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Originally Posted by duuuuuuuude
(Post 12803675)
It may also be that your springs are too stiff. Have you performed FS's spring tuning procedure?
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