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Old 02-23-2012, 08:16 PM   #1651
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Originally Posted by 6376vette View Post
When you say get the arms parallel are you referring to the relation between the upper link and the lower arm?
Yes.

AArivers, Man you got ALOT going on with your ride!! The long links in the rear are a bad idea, in essence it raises roll center way out of whack more than it already is! go back to the short link and raise the Roll center by lowering the inside link as much as you can without hitting the drive shafts, I had to do a little grind work on the actual ball cups due to the extreme angle.
Running the front of your car that wide and the rear narrow compounds the boat effect, that sway bar looks really thick! With your rear links like that you get absolutely no camber gain in fact i think you may actually get positive gain! I believe that is the reason 3racing built the rear arms like that. I wonder what would happen if you just ran like -3* of rear camber? that may help out,sounds extreme but the lower arm is already at an extreme angle. Without me actually seeing your car on a video i am just speculating, it just seems that there are a lot of counter acting forces in there!
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Old 02-23-2012, 09:15 PM   #1652
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Originally Posted by MantisWorx View Post
Yes.

AArivers, Man you got ALOT going on with your ride!! The long links in the rear are a bad idea, in essence it raises roll center way out of whack more than it already is! go back to the short link and raise the Roll center by lowering the inside link as much as you can without hitting the drive shafts, I had to do a little grind work on the actual ball cups due to the extreme angle.
Running the front of your car that wide and the rear narrow compounds the boat effect, that sway bar looks really thick! With your rear links like that you get absolutely no camber gain in fact i think you may actually get positive gain! I believe that is the reason 3racing built the rear arms like that. I wonder what would happen if you just ran like -3* of rear camber? that may help out,sounds extreme but the lower arm is already at an extreme angle. Without me actually seeing your car on a video i am just speculating, it just seems that there are a lot of counter acting forces in there!

Hey Marcus how are ya champ??
Hey need some advice.
Im testing a hobby wing sensorless esc and 13t motor in my fgx but everytime I come out of a corner and go to throttle up, the car just spins.
Is this cause the motor is to punchy for it or car setup?
Esc settings are timing 0 and throttle profile 1(lowest)
I cant hit 100% throttle down the straight onto our long right handed sweeper. but when i go 1/2 throttle the tyres chirp like there is tons of grip.
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Old 02-23-2012, 09:21 PM   #1653
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Originally Posted by shano83 View Post
Hey Marcus how are ya champ??
Hey need some advice.
Im testing a hobby wing sensorless esc and 13t motor in my fgx but everytime I come out of a corner and go to throttle up, the car just spins.
Is this cause the motor is to punchy for it or car setup?
Esc settings are timing 0 and throttle profile 1(lowest)
I cant hit 100% throttle down the straight onto our long right handed sweeper. but when i go 1/2 throttle the tyres chirp like there is tons of grip.
when you use a sensorless ESC in an onroad car it is not easy to drive smooth, sensored is the way to go but since it is what you have turn the Start power all the way down. it is used to keep cogging to a minimum but if you have the setting too high it will surge on exit and make the car spin. I had the same problem with my hobbywing sensored ESC and have switched to a Tekin RS and it is much smoother. I need to know what your current setup is to see what needs to be changed, post it up!
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Old 02-23-2012, 09:35 PM   #1654
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Originally Posted by MantisWorx View Post
Yes.

AArivers, Man you got ALOT going on with your ride!! The long links in the rear are a bad idea, in essence it raises roll center way out of whack more than it already is! go back to the short link and raise the Roll center by lowering the inside link as much as you can without hitting the drive shafts, I had to do a little grind work on the actual ball cups due to the extreme angle.
Running the front of your car that wide and the rear narrow compounds the boat effect, that sway bar looks really thick! With your rear links like that you get absolutely no camber gain in fact i think you may actually get positive gain! I believe that is the reason 3racing built the rear arms like that. I wonder what would happen if you just ran like -3* of rear camber? that may help out,sounds extreme but the lower arm is already at an extreme angle. Without me actually seeing your car on a video i am just speculating, it just seems that there are a lot of counter acting forces in there!
Yeah this was TryHard's car and he had modded it to get a better roll center, I would like to lower the inner ball studs though to get the links a little better upward angle. I'll add some camber to them and see what happens, they are actually sitting at 0* right now so I well start at 2* and go from there. I also put the car on my 4 scales and corner weighted it tonight and got it pretty even left to right, so that will help with it turning the same either direction. I'm not sure what surface it was raced on before also. I'll borrow a friend of mines go pro and strap it to my head for a few runs the next time I go out.
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Old 02-23-2012, 09:55 PM   #1655
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Originally Posted by aarivers View Post
Yeah this was TryHard's car and he had modded it to get a better roll center, I would like to lower the inner ball studs though to get the links a little better upward angle. I'll add some camber to them and see what happens, they are actually sitting at 0* right now so I well start at 2* and go from there. I also put the car on my 4 scales and corner weighted it tonight and got it pretty even left to right, so that will help with it turning the same either direction. I'm not sure what surface it was raced on before also. I'll borrow a friend of mines go pro and strap it to my head for a few runs the next time I go out.
Did you balance the left to right on pins or from a string first? Spring pressures can distort a balance reading. You can get equal spring pressure measurements on scales and still have a very unbalanced car.
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Old 02-23-2012, 10:21 PM   #1656
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Originally Posted by MantisWorx View Post
when you use a sensorless ESC in an onroad car it is not easy to drive smooth, sensored is the way to go but since it is what you have turn the Start power all the way down. it is used to keep cogging to a minimum but if you have the setting too high it will surge on exit and make the car spin. I had the same problem with my hobbywing sensored ESC and have switched to a Tekin RS and it is much smoother. I need to know what your current setup is to see what needs to be changed, post it up!

Hey mate cheers for the quick reply!!
I have throttle profile 1 (start power)
and setup as follows

Front:
1* camber plate - 35g
Soft silver spring -
modifed top arms with turn buckles.
1.5* in camber
0* toe
0* caste
4.5mm ride height
tyres-Slick shimizu medium

Rear:
Single hole pistion in the dampers
500 shock oil
heaviest spring (3 racing fgx pack)
sway bar kit - 5 stripe
2* rear toe plate
1mm droop
ride height 5mm
gear diff - 700wt
tyres-grooved shimizu soft

esc settings
standard gearing 26t
throttle profile(start power) - 1
esc timing - 0
drag brake - 10%

Track is outdoor bitumen low grip ( for tc racers)

Last edited by shano83; 02-24-2012 at 02:43 AM.
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Old 02-24-2012, 04:51 AM   #1657
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Originally Posted by shano83 View Post
Hey mate cheers for the quick reply!!
I have throttle profile 1 (start power)
and setup as follows

Front:
1* camber plate - 35g
Soft silver spring -
modifed top arms with turn buckles.
1.5* in camber
0* toe
0* caste
4.5mm ride height
tyres-Slick shimizu medium

Rear:
Single hole pistion in the dampers
500 shock oil
heaviest spring (3 racing fgx pack)
sway bar kit - 5 stripe
2* rear toe plate
1mm droop
ride height 5mm
gear diff - 700wt
tyres-grooved shimizu soft

esc settings
standard gearing 26t
throttle profile(start power) - 1
esc timing - 0
drag brake - 10%

Track is outdoor bitumen low grip ( for tc racers)
Even on our medium grip indoor track, 100% power is a no-no. I recommend trying some expo on your throttle to soften the bottom and a bit , plus wind your e.p.a back to 60% , then sneak it up from there if you can.
The HW is brutal in its power delivery, so only good for open , fast flowing , grippy tracks.
I recently bolted a 2000kv motor in mine and went half a second a lap faster, more consistently too.
I'm looking to go to a sensored 21.5 soon, though a 17.5 might be good on a larger track. This is zero boost I am referring to .....
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Old 02-24-2012, 05:50 AM   #1658
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Originally Posted by RedBullRacing View Post
Even on our medium grip indoor track, 100% power is a no-no. I recommend trying some expo on your throttle to soften the bottom and a bit , plus wind your e.p.a back to 60% , then sneak it up from there if you can.
The HW is brutal in its power delivery, so only good for open , fast flowing , grippy tracks.
I recently bolted a 2000kv motor in mine and went half a second a lap faster, more consistently too.
I'm looking to go to a sensored 21.5 soon, though a 17.5 might be good on a larger track. This is zero boost I am referring to .....
Cheers Red!!
might have to do that and also play with throttle curve
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Old 02-24-2012, 08:34 AM   #1659
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Originally Posted by shano83 View Post
Hey mate cheers for the quick reply!!
I have throttle profile 1 (start power)
and setup as follows

Front:
1* camber plate - 35g
Soft silver spring -
modifed top arms with turn buckles.
1.5* in camber
0* toe
0* caste
4.5mm ride height
tyres-Slick shimizu medium

Rear:
Single hole pistion in the dampers
500 shock oil
heaviest spring (3 racing fgx pack)
sway bar kit - 5 stripe
2* rear toe plate
1mm droop
ride height 5mm
gear diff - 700wt
tyres-grooved shimizu soft

esc settings
standard gearing 26t
throttle profile(start power) - 1
esc timing - 0
drag brake - 10%

Track is outdoor bitumen low grip ( for tc racers)

Go 2 hole 80wt in the shocks
80wt shock oil in the dif
softest springs
3*toe plate
#4 sway bar


this should help alot!
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Old 02-24-2012, 09:16 AM   #1660
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Originally Posted by RedBullRacing View Post
Even on our medium grip indoor track, 100% power is a no-no. I recommend trying some expo on your throttle to soften the bottom and a bit , plus wind your e.p.a back to 60% , then sneak it up from there if you can.
The HW is brutal in its power delivery, so only good for open , fast flowing , grippy tracks.
I recently bolted a 2000kv motor in mine and went half a second a lap faster, more consistently too.
I'm looking to go to a sensored 21.5 soon, though a 17.5 might be good on a larger track. This is zero boost I am referring to .....
Very true on the HW thing, i had to go to an RS, the driveability even on our high speed track was not very good.
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Old 02-24-2012, 11:07 AM   #1661
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Originally Posted by MantisWorx View Post
Ok so i just sketched the rear geometry out on a piece of paper and there is no real roll center??? because of the angle of the lower arm the upper arm will never cross its path!
Yeah there is. I've played with suspension geometries in CAD quite a bit. There is always a crossing point. I'm assuming you didn't find a point because the exact place your suspension was set at the time resulted in a straight line drawn between the inner and outer king pins on the lower arm and the upper link was completely parallel. Basically level ride height with level arms and level upper links? If this is the case then your roll center at this point is set directly at ground level regardless of camber link length.

Remember that your roll center moves around as the suspension does. The higher the roll centers are set, the less they move around in space but the more camber gain you get. The lower the roll centers are set the more the roll centers move around in space but the less camber gain you get.

Here's a quick CAD mockup that I just did. You may have to rotate is 90 degrees. I removed all of the intersecting lines that arrived at the roll center location (circle) since they wouldn't fit on the page anyways.
Attached Files
File Type: pdf roll center.pdf (6.6 KB, 169 views)
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Old 02-24-2012, 11:16 AM   #1662
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Originally Posted by fredswain View Post
Yeah there is. I've played with suspension geometries in CAD quite a bit. There is always a crossing point. I'm assuming you didn't find a point because the exact place your suspension was set at the time resulted in a straight line drawn between the inner and outer king pins on the lower arm and the upper link was completely parallel. Basically level ride height with level arms and level upper links? If this is the case then your roll center at this point is set directly at ground level regardless of camber link length.

Remember that your roll center moves around as the suspension does. The higher the roll centers are set, the less they move around in space but the more camber gain you get. The lower the roll centers are set the more the roll centers move around in space but the less camber gain you get.

Here's a quick CAD mockup that I just did. You may have to rotate is 90 degrees. I removed all of the intersecting lines that arrived at the roll center location (circle) since they wouldn't fit on the page anyways.
The lower arms are nowhere near level at ride height, not even close! The upper is level, they will only cross outside the car.
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Old 02-24-2012, 11:29 AM   #1663
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Yup. That doesn't matter. At the intersection point, in this case way outside, draw a line from that point to the center of the nearest tire. Now continue that line past the tire to the vertical centerline of the car. Do the same for the other side. Where they intersect is the roll center.

Sometimes the lines intersect inside the wheelbase and other times outside but they always intersect somewhere and reference the same tire.
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Old 02-24-2012, 11:32 AM   #1664
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Here you go.
Attached Files
File Type: pdf roll center 2.pdf (6.1 KB, 108 views)
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Old 02-24-2012, 11:44 AM   #1665
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Originally Posted by MantisWorx View Post
The lower arms are nowhere near level at ride height, not even close! The upper is level, they will only cross outside the car.
Quote:
Originally Posted by fredswain View Post
Yup. That doesn't matter. At the intersection point, in this case way outside, draw a line from that point to the center of the nearest tire. Now continue that line past the tire to the vertical centerline of the car. Do the same for the other side. Where they intersect is the roll center.

Sometimes the lines intersect inside the wheelbase and other times outside but they always intersect somewhere and reference the same tire.
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Originally Posted by fredswain View Post
Here you go.
Fred is correct. Problem with the second drawing is even though the RC is low, the angle of the lower arms will induce positive camber in bump/roll and reduce traction. This is why the FGX tends to run similar tires F/R or softer rear tires compared to the straight axle cars which tend towards harder rear tires on high traction surfaces.

Instant centers will always intersect unless the upper and lower links are parallel. With unequal length links and an inclined upper link they typically tend to intersect on the opposite side of the chassis, on the 'outside'. With the inclined lower link like you have on the FGX, they will intersect on the same side of the chassis on the 'outside'. As Fred stated you have to plot the third line from the center of the tire to locate the true RC of the chassis at any given position of the suspension travel.

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