hobiercr (FS) said:Have you gotten all the rocks out of your shorts?
a perfect 1000th post in this thread!
But, to your question, that's a negatory ghost rider.
hobiercr (FS) said:Have you gotten all the rocks out of your shorts?
a perfect 1000th post in this thread!
But, to your question, that's a negatory ghost rider.
Robbie, I think we talked about fabrication of uprights? Either for the front or rear? If we did, here's a great video of what I was talking about
Hot digging dog. That is a heck of drag time. Can't say that I am super surprised that it goes straight as you put a ton of thought in this beast.
AngryCorvair (Forum Supporter) said:In reply to Robbie (Forum Supporter) :
Congrats on the reliability!
Did you ever mess with tire pressures?
We did, a bit. One of the pro drivers (Alan/Allen/however it is spelled) took it out for a couple spins on the autocross. On his advice we went from about 10-12psi and dropped rear pressure to 8 and front to 10 for one of his runs and it helped a lot but it was no solution to the bouncing. At certain points I personally saw that it would have maybe one wheel on the track, Robbie thinks it got completely airborne a time or two. It 100% needs a damping system on it.
I don't know that Robbie and Ian played with it during drags, though.
In reply to Mr_Asa :
I'm guessing the airborn action probably happened at the seam between the north & south parts of the lot behind the concession stand?
Pete Gossett (Forum Supporter) said:In reply to Mr_Asa :
I'm guessing the airborn action probably happened at the seam between the north & south parts of the lot behind the concession stand?
Yes, exactly. It would get into oscillations due to pendulum effect. We are heavily sprung, and not dampened. So tires and chassis are doing all the requisite dampening. Which is not enough at current mass. When its a tiny little Formula car, its enough, but when you add all that weight, in the areas we did, it became a comical moving pendulum.
I think I cracked a molar in the back coming back towards the concession stand in corner 4. I also DNF'd almost every run due to skipping across the pavement and missing the gate entirely. Was actually funny. We will have to immediately change some things. But we know what we need to do, and we have the budget space. Robbie and I already have hatched plans for next year!
In reply to RACEC4R :
Please tell me that there is a video that caught the action. I'm really curious to see that. And what are you guys thinking for dampeners? Rubber bushings?
RACEC4R said :
Robbie and I already have hatched plans for next year!
hell yeah! I can't wait to see what you're able to do with a full year of development!
fanfoy said:In reply to RACEC4R :
Please tell me that there is a video that caught the action. I'm really curious to see that. And what are you guys thinking for dampeners? Rubber bushings?
One of the GRM staff (Collin?) hitched a go-pro to the roll bar for Ian's very first run, so somewhere on some SD card there very likely is some incredibly shaky and un-useable video of our car skipping across the pavement.
My brother may have also taken some video, I still need to see what all he's got.
In reply to Mr_Asa :
Dude, thanks for the photos and videos. Will review.
Also, huge thanks for all your help over the weekend. Ian and I were definitely impressed by your attention to detail and knowledge and we were flattered that you were willing to just jump in and help some random folks from the internet.
Friction/Stiction is a form of damping, right? 
I got to see the bounce first hand when I was working corner 5 ( far end of the lot at the first turn around). I got the impression that the inside rear wouldn't let go and was pushing the front causing some of the hop.
In reply to RACEC4R :
I experienced that firsthand in Stampie's Q45 2 years ago & it was probably my single most terrifying moment behind the wheel, because it was completely unexpected. The steering was just "gone" and the wheel went full-lock. Then it landed, got traction & I tried to counter-steer just in time for it to go airborne again & the process to repeat in the opposite direction.
Robbie (Forum Supporter) said:In reply to Mr_Asa :
Dude, thanks for the photos and videos. Will review.
Also, huge thanks for all your help over the weekend. Ian and I were definitely impressed by your attention to detail and knowledge and we were flattered that you were willing to just jump in and help some random folks from the internet.
Thank you guys for letting me be a part of the team, really. It was a great experience.
sleepyhead the buffalo said:Friction/Stiction is a form of damping, right?
Within Fmod this is the answer. Most of the cars use rocker arms and work in some friction to the motion of those, but we are limited by the rulebook.
Being that you have aero on the car, you are out of Fmod and into A or B mod (if the body is off). There is a guy on the Fmod facebook group using some motorcycle shocks to hillclimb his (in "specials" class I think) due to bumpy road concerns.
Depending on how much budget you have to play with, making a ghetto cheap friction damper or soem research and motorcycle (or other stupid cheap coilover of sufficient rate) shocks are likely the answer...
Or even keep the rubbers and just put a shock over it?
I'm trying to remember what your rear suspension is, is the engine on the unsprung side of the pivot? (if so, old and BAD and an area for massive improvement no matter which dampning you are doing).
In reply to Apexcarver :
Rear suspension is the tires and the pucks. Engine is on the sprung side, but thats isnt saying much
What about some type of dampening taken from 1/12th scale rc pan cars
The red tubes are just filled with different lubes to provide dampening side to side.
Or, you could just use 2 circular plates sandwiching some grease that slide around each other. 1 plate fixed to the front chassis, the other fixed to the rear. Add a spring to sandwich the 2 together and allow chassis vertical movement. Google rc12l and that might make sense. In this pic you can see the dampened disc on top of the rear pod...
In reply to wvumtnbkr :
I've got an RC12L4 sitting next to my work desk for inspiration while I should be working 
Ok! Here are some videos from the challenge, courtesy of my brother!
2nd drag run (14.1)
We think this was the fastest autox run. You can't really see the bouncing, but you can see the car going really slow through the bouncy sections in order to minimize the issue.
no-lift shift sounds the business!
In reply to Robbie (Forum Supporter) :
I saw my car! Man it looked slow. Also, that guy on the bleachers is my dad! Great shots.
Would ya just listen to it...
Omg that country music blaring can eat my ass
In reply to Patrick (Forum Supporter) :
Yeah it was... uhh... yeah.
Gainesville. It was Gainesville
Mr_Asa said:In reply to Apexcarver :
Rear suspension is the tires and the pucks. Engine is on the sprung side, but thats isnt saying much
Those cars were notoriously bouncy. I've seen old runoffs video of them pogoing around a road course. The inertia of the unsprung weight relative to the rest of the chassis was the root of the problem I think. Not sure that the RC comparisons will give good or accurate representation of the relative tire sidewall dynamics.
It would be worthwhile to redo the rear suspension entirely and in doing so reduce unsprung weight and work in actual shocks and springs. There are ways of ghetto fabricating a solution costing more time than money.
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