2016 SM (Street Mod) Autocross Discussion
May 3, 2016, 01:19 PM
#61
I think the steering forces are indeterminate by math but I have a plan! I know the arm didn't immediately self destruct and lasted 3 runs before failing so I must have been teetering right around the yield strength and probably exceeded it with a force spike since sustained would have kept bending it. This is also with sticker A7s in 295s, top of 2nd sweepers, and 3rd gear heavy transitions. So I feel the forces are indicative of heavy standard loads (not bump or collision). Maybe track guys with aero hitting curbs will see higher but hard to know how much.
I came home and ran some quick FEA numbers and the parts fails around 500lb of force. So the goal is 5000lbs of force. Now I cant make this thing indestructible, and if 5000lbs is exceeded well you have other issues. 5000 should be an easy target but will keep "y'all" updated.
I also checked the bolt pullout forces for M8 screws in aluminum and have calculated 7000lbs pullout force each and I'm using two inside and two outside. There's also leverage to take into account, which is about 2.25:1. I've considered upping these to M10s but I don't think its necessary and it does take up more space.
I came home and ran some quick FEA numbers and the parts fails around 500lb of force. So the goal is 5000lbs of force. Now I cant make this thing indestructible, and if 5000lbs is exceeded well you have other issues. 5000 should be an easy target but will keep "y'all" updated.
I also checked the bolt pullout forces for M8 screws in aluminum and have calculated 7000lbs pullout force each and I'm using two inside and two outside. There's also leverage to take into account, which is about 2.25:1. I've considered upping these to M10s but I don't think its necessary and it does take up more space.
May 3, 2016, 01:31 PM
#62
I think the steering forces are indeterminate by math but I have a plan! I know the arm didn't immediately self destruct and lasted 3 runs before failing so I must have been teetering right around the yield strength and probably exceeded it with a force spike since sustained would have kept bending it. This is also with sticker A7s in 295s, top of 2nd sweepers, and 3rd gear heavy transitions. So I feel the forces are indicative of heavy standard loads (not bump or collision). Maybe track guys with aero hitting curbs will see higher but hard to know how much.
I came home and ran some quick FEA numbers and the parts fails around 500lb of force. So the goal is 5000lbs of force. Now I cant make this thing indestructible, and if 5000lbs is exceeded well you have other issues. 5000 should be an easy target but will keep "y'all" updated.
I also checked the bolt pullout forces for M8 screws in aluminum and have calculated 7000lbs pullout force each and I'm using two inside and two outside. There's also leverage to take into account, which is about 2.25:1. I've considered upping these to M10s but I don't think its necessary and it does take up more space.
I came home and ran some quick FEA numbers and the parts fails around 500lb of force. So the goal is 5000lbs of force. Now I cant make this thing indestructible, and if 5000lbs is exceeded well you have other issues. 5000 should be an easy target but will keep "y'all" updated.
I also checked the bolt pullout forces for M8 screws in aluminum and have calculated 7000lbs pullout force each and I'm using two inside and two outside. There's also leverage to take into account, which is about 2.25:1. I've considered upping these to M10s but I don't think its necessary and it does take up more space.
May 11, 2016, 02:10 PM
#65
Yes, less front bar and more rear. I started full stiff on front stock (cusco bracket) and full stiff rear (Hotchkiss bar). I went to full soft on the front bar and still the rear wouldn't move.
I just swapped in my 26mm whiteline bar which is basically like taking the adjustment range of the Hotchkiss exactly 3 steps further. In other words, softest on the whiteline is like one setting stiffer than stiffest on the Hotchkiss. To start next event, both are set to middle and effectively 2 steps stiffer rear, one step stiffer front. There I can easily go up or down on either end based on what the cars doing.
Now just fingers crossed the rain holds off for Saturday morning testing.
I just swapped in my 26mm whiteline bar which is basically like taking the adjustment range of the Hotchkiss exactly 3 steps further. In other words, softest on the whiteline is like one setting stiffer than stiffest on the Hotchkiss. To start next event, both are set to middle and effectively 2 steps stiffer rear, one step stiffer front. There I can easily go up or down on either end based on what the cars doing.
Now just fingers crossed the rain holds off for Saturday morning testing.
May 11, 2016, 10:05 PM
#68
At the bar rates most evo guys run, especially rear, they aren't just a fine tuning device and are a significant part of roll rate.
Marshal, I think it was a little different result based on my old setup that worked "ok" on asphalt. Less roll moment meant car had too much front bar/ not enough rear bar. But as a result of fighting the hopping had me running too much front bar/not enough rear previously and too much rear rebound. It helped the hop, but caused more low speed push and high speed twichiness. Didnt hop but as we discussed, moved outside the happy window.
The front definitely bit harder, but since I was much more concerned with checking the strength I didn't put nearly enough thought into balance and overall effect. I have no doubt the arms were flexing considering they eventually bent so its hard to really use the 3 runs a serious data point. Hoping this weekend I can get a better feeling of things.
Im just one car with other life things going on. Will be nice to get a set on another high level build for testing. Have a car in mind, but making these things isnt quick. Its several full days of work to make one set and this is just a side project to my real job.
Marshal, I think it was a little different result based on my old setup that worked "ok" on asphalt. Less roll moment meant car had too much front bar/ not enough rear bar. But as a result of fighting the hopping had me running too much front bar/not enough rear previously and too much rear rebound. It helped the hop, but caused more low speed push and high speed twichiness. Didnt hop but as we discussed, moved outside the happy window.
The front definitely bit harder, but since I was much more concerned with checking the strength I didn't put nearly enough thought into balance and overall effect. I have no doubt the arms were flexing considering they eventually bent so its hard to really use the 3 runs a serious data point. Hoping this weekend I can get a better feeling of things.
Im just one car with other life things going on. Will be nice to get a set on another high level build for testing. Have a car in mind, but making these things isnt quick. Its several full days of work to make one set and this is just a side project to my real job.
May 11, 2016, 10:45 PM
#69
Looking forward to seeing your results from your next event. I think I mentioned my plan was to buy the Racefab LCAs and tie rod ends, but I'm wary of a 30mm spacer on the lca ball joint and the tie rod ball joint. Seems like it's just asking for trouble. Your setup seems like a much better solution all around.
Are you running the Evo 10 LCA? I can't remember.
Are you running the Evo 10 LCA? I can't remember.
May 14, 2016, 09:22 PM
#70
Ok, ok, ok, wtf, ok.....
I don't even know where to start, this is different. Like, re-learn to drive different. Even my wife that's not really too interested in understanding the difference consistently drove into cones because the car never turned in like this. There is no wait for the front to settle, its already there. I literally want everyone to feel this before and after.
So what changed? We moved the roll center up back to factory height, dropped front roll back to stock, upped rear roll bar to mid setting on 26mm swaybar.
I just dont know what to say after today. Its a new car. Few things have felt as different this but totally in a great way.
I need to take a pic of the angle of my buddies control arms compared to mine. Its significant!
I don't even know where to start, this is different. Like, re-learn to drive different. Even my wife that's not really too interested in understanding the difference consistently drove into cones because the car never turned in like this. There is no wait for the front to settle, its already there. I literally want everyone to feel this before and after.
So what changed? We moved the roll center up back to factory height, dropped front roll back to stock, upped rear roll bar to mid setting on 26mm swaybar.
I just dont know what to say after today. Its a new car. Few things have felt as different this but totally in a great way.
I need to take a pic of the angle of my buddies control arms compared to mine. Its significant!
May 15, 2016, 09:10 PM
#72
My method of setup still isnt changing, dial in spring rates to a reasonable natural frequency, balance with bars. So my spring rates arent changing at all but I did change front bar significantly.
Previously I ran WL 26 front full soft and 26mm rear full soft. I did really need to up the rear bar a little and reduce rear rebound but didnt get to try it before changing to these hubs. Now Im running stock bar (stock setting on cusco bracket) and 26mm rear bar at med stiff.
The one thing I still need to figure out is rear grip on acceleration. Getting a ton of rotation on throttle. I know I can dial in more rear toe in but need to think about what else will keep the car gripping on sweeper exit on full throttle.
Previously I ran WL 26 front full soft and 26mm rear full soft. I did really need to up the rear bar a little and reduce rear rebound but didnt get to try it before changing to these hubs. Now Im running stock bar (stock setting on cusco bracket) and 26mm rear bar at med stiff.
The one thing I still need to figure out is rear grip on acceleration. Getting a ton of rotation on throttle. I know I can dial in more rear toe in but need to think about what else will keep the car gripping on sweeper exit on full throttle.
May 16, 2016, 06:56 AM
#73
EvoM Guru
iTrader: (1)
Soften compression damping a bit in the rear, let it squat.
May 16, 2016, 08:23 AM
#74
After this weekend talking with the codriver (my wife) we think some double adjustable are in order for that and getting the car more compliant with our local bumpy courses. Damn asphalt seems to get worse and worse every year. I also need to start going thru suspension looking for stiction to make sure I'm not inducing anything.
So what's the hot ticket in doubles these days? I know FA seems to have a good following and their dreadnaughts are ran by lots of time attack and track guys. There's also MCS which is said to be the hottest hotness. And I know a certain cam mustang driver loves his MCS doubles.
So what's the hot ticket in doubles these days? I know FA seems to have a good following and their dreadnaughts are ran by lots of time attack and track guys. There's also MCS which is said to be the hottest hotness. And I know a certain cam mustang driver loves his MCS doubles.
May 16, 2016, 08:25 AM
#75
EvoM Guru
iTrader: (1)
Ah, I was under the impression you already had doubles for some reason.
How much do you think you'll be bale to sell those knuckle for if you were to offer them?
How much do you think you'll be bale to sell those knuckle for if you were to offer them?