Great insight and question, I never would have thunk it.
Curious to hear an answer on this myself ?

I remember watching Indy Car races on tv one day and they showed an explanation video of the amount of suspension travel loss as the cars reach full speed. It was accompanied my an actual video mounted on an indy car to show this in real time. Quite surprising how much it pushes down on the car.


I understand you want to set up the car low, but how low? Too low and a good body would cause the suspension to bottom out going down the straight? :surprised:

Funny thing about Indy + F1 cars, if you need more traction in a corner, go faster. While more speed = more downforce is easily understood, try telling your brain to press on the gas more in that situation!

I'm sure there are formulas Indy + F1 teams use, but they know how much downforce the car makes, spring rates, etc. Doubt anyone knows exactly how much a particular rc body makes. I'm sure someone will pipe in with a useful setup though.

I wonder if you could use something attached to the chassis to see how much the suspension compresses during a run. My first thought is clay, that would wear if it touched pavement, but I'm sure someone could come up with something better.

I setup my chassis so that it levels out evenly under acceleration. I prefer my driveline to be parallel with the ground as well. But this is just how I run. Setup might need adjustment once I use a different body.

Thats actually a good idea.

I was thinking along the line. Something attached to the chassis that would monitor the suspension arms movements. However, the condition of the ground would impair this measurement as the suspension moves on every dip and raise.



I guess my question is how do you tell chassis position under acceleration beside eyeballing it?

You could do the same thing with one of those mini-cams. I probably wasn't thinking about it because I like most guys don't have one. But it could watch the suspension arms while under the body easy enough. If you want to get scientific, place a ruler (or something else with graduations on it for reference) by the arm you're filming to get a more accurate reading of it's position.

I'm old school and I use eyeballs for my setups. Too much calculating takes away from play time. I use trial and error and have fun doing it. I setup for lets say 60mph and see how the car behaves. I change gearing for a higher speed and see how the car behaves. Calculations will only bring you so far. The only calculations I do, is with the use my simple spreadsheet. And back those numbers up with my datalogger. Kinda works like BrianG calculator. You don't have a wind tunnel to play with, so why waste time calculating things you don't have hard numbers for.

70mph in a 1/8 is pretty damn fast and still affordable to me. 100mph is just stupid fast and I can't afford the upkeep of such a monster without my wife killing me.

100mph is just cool! :whistle: Over 100mph is, well its :surprised:

I want to go 112.15mph which is .01 over my LHS guy's GTP.

Closest I've been, must of been in the lower 90's. Too bad I erased the datalog file by accident of that one and only run. I probably could go faster with better batteries and tires. Probably also getting rid of all the dogbones would help as well. OR or or is it maybe the limitation of my RX8 over the MMM esc.

This is as far as I go when it comes to calculations. Snippet of my spreadsheet. I have one of those for every motor that I have. Vehicle weight is off in this spreadsheet.

http://i189.photobucket.com/albums/z...in/gtp/gtp.jpg

I'll have a crack at a few considerations;

- in my experience the servo can be anything because steering weight isn't an issue for straight line running. If however you install a gyro, speed becomes an issue...it needs to keep up with gyro. I have a couple of those 1015's - fast, strong & they work nicely with a gyro the way I've used them

- again in my experience fore and aft downforce/suspension can be measured by feel & eyeball. Too soft in the rear & you loose steering when you're accelerating hard...too soft in the front & you'll loose the back end when braking (the back will try & overtake the front). Kind of basic as a theory but it's worked for me

- ride height depends on the running surface. A 1/10 TC has < 1/4" at speed but hit a bump in the road & it's airborne...I would think somewhere between 1/2-3/4" for 1/8 scale is a reasonable starting point. Here's my Rustler...has about 1/2" in the static position. I limited the shock upstroke with fuel tube (pink) so that it never bottomed out but there's no evidence that the shock ever compressed that far...I had it up over 95mph by my GPS

http://i703.photobucket.com/albums/w...h_P1010037.jpg

- I would use the stiffest springs available & 50-70wt shock oil, depending on the brand (I use 70wt Losi in my 8T) & then fine tune ride height etc on the shock itself

I look at speed runs as an equation. If the equation is balanced then controllable speed will come relatively easily

I know what the Gyro will do in a drift car and of course for Helis, but please explain why you think it'll be a wise consideration for a straight shooter/drag car ?

And, can I get away with using as cheapie from Hobby city or should I be thinking of spending $$ on a qaulity unit (they get expensive quickly !)

Thanks again for the advice, this thread seems to be getting a bit of attention ?
I'm appreciative to get all this advice from you gentlemen,Thank You all.

In a 2wd the gyro can work for both acceleration & braking. With my Rustler I found that under acceleration if I lost rear wheel traction the way I had the gyro set up it made the situation worse & the steering started hunting (over correcting) & fighting itself to the point where the gyro had more control than I did even after I'd returned the TX to neutral...under braking however if I was running straight & the gyro was reduced a little from the point where it would hunt under acceleration, I could brake to a slow stop without any concern that I 'd loose control. Over 80, I find stopping a 2wd hard without some help

In a 4wd, if you use a gyro, I'd suggest adjusting the gain to aid braking. It just lessens the stopping worry & gives a bit more confidence to push harder under acceleration...but they're not as important in 4wd IMO

Sorry for the long winded answer

Stopping is something worth considering also. You want to stop slowly from 80+, I use about 15% drag & 30% brakes. Once you're not accelerating the drag settles the car momentarily before you start braking, I'm only talking half a second or so. I found this suits my style very well...I can't accelerate & then brake from that sort of speed easily, I just spin, so a very brief pause works for me. If you go mechanical brakes they obviously work as well as they're tuned but to replicate the same progressive feel takes more than adjusting the ESC but it's worth spending that setup time because hitting the anchors over 80 really unsettles the car

You say long winded, I say informative.

Gyro; I will try without first, if I'm having any problems I will seriously consider one.

Thanks.

I second that and will do the same on the gyro.

I was planning on working up 30% drag brake and using 30% brakes.

I think I have everything planned out so far, and mostly everything on the way for my build. Just need my special lipos and packages to arrive. The only thing that worries me now is blowovers. We shall see how it comes together...

Bondo: Have you thought of tires? Going to run the GRP's? If so rcboyz on ebay has them.

Also, I was reading through and realized that you were running in 500ft, both acceleration and braking. So you are going to want fast acceleration, great traction, and then smooth braking. Sounds like fun!!

NitroSneezer,
Yup, I'm ready to go to ! You'll have your stuff befor me though, BASTARD!
Gotta wait till Horizon gets mine then ship it out, little luck I'll see it third week this month.

I had planned on starting w/the kit tires what ever they are ? Do a thorough glue job and balance them and they should be just fine for testing at the least. I'm not in a big hurry to worry about tires yet, I have to settle on what I can get from Horizon to keep expenses down via the HobbyShop job.
Thanks for the GRP/RCBoyz heads up, I bought a LOT from them over the years !

I haven't measured the good surface yet, 500' is a educated guess ? Theres plenty of room befor and after it's just cobbley asphault that'll obviously upset the car.

If I'm not to tired I might go out where they're running and catch some video to posts, No one starts showing till 10pm or so.
I have to get up early for a day at the track :yipi::yipi:

Merry Christmas to me:
http://images1e.snapfish.com/2323232...8%3B2335nu0mrj

Sweet Nitro, your on your way to getting started !
More info about your set up, what motor w/the 4s,gearing etc.

Q For you speed demons, Which would I better off with ?

The stock center spool or a open diff and explain why please.

Top secret info...

Roller should be here soon. Body and GRP tires are at the post office.

I'm going with the stock spool (never seen or held one though) because I run 100k in my 8T diff which netts a similar effect. I run fairly light fluids fore & aft because I still need to turn around...I would expect this strategy to work with a fixed spool also

As a footnote though, I've found I eat bearings at frighteningly short intervals using 100k, this will often present as the rear centre drive failing under load...sounds ugly, looks ugly & has potential for mucho damage!

I got the PF8-GT body and GRP soft rally tires in today after a fiasco with USPS. Just waitng on my roller now!

coolbeans man. My GRP's arrived today. The body has been mounted but still needs painting. As the body is a high downforce model allready, I need to figure out what to with the rear spoiler. But it will be probably be 2 months before I even will have a chance at the 100mph run. I don't have too much free time right now.

This is yanking my chain, you guys are gonna get yours together befor me :cry::cry::cry::grrrrrr::slap:

If I'm lucky my roller will ship out next week, fat fingers crossed.

Cool stuff!

Any specific preparation required when mounting these bodies? Just make sure its on the car square and level?

Setting up the car with roughly 1/2-5/8" of ground clearance. The body should have roughly the same as well?

I keep my driveshafts parallel to the ground. The body will sit lower on mine. I have no clue how stiff the body will be at high speeds. But I might have to add body stiffeners behind the front fender well and in front of the rear fender well. The rear wing will be my main issue. I'm just hoping the Hacker can deal with my nonsense.

Post some photos guys

I only have parts for now. Roller shipped today. The seller put 4 new driveshafts on it before shipping. Can't complain there.

I will say, I have the GRP tires in soft. They are some sticky!!!

http://www.doorsofnight.com/IMOBlog/.../04/o_rly1.jpg

Would it be to much to ask for a linkypoo ?

I was checking out Dynamite brand 1/8 scale street tires yesterday at the LHS, they're inexpensive and very soft. The price kinda scares me tho, consdering they might just vaporise with the set up I'm plannning on ?

http://cgi.ebay.com/Kyosho-Inferno-G...#ht_3286wt_912

and direct


http://www.grpgandini.it/provaIVA/in...emid=6&lang=en

I saw them blow up not too long ago.

:lol::lol:

check page 5 for mine.

Those will be too sticky, unless you dragrace or run on a real dragstrip for your speedruns. If I would get those, I would need to invest in the RCM slipperential.

I second that!

I purchase the Soft compound.
http://cgi.ebay.com/Kyosho-Inferno-G...item5192eb913d

Just got home from the weekly meet behind the Lowes, There was some carnnage tonight ! Some Asshole was running WOT to close to the crowd and blasted two guys in the ankles doing roughly 50mph+, took the both out. On dude went to the hospital the other had a serious cut but refused to go ? The guy driving was oblivious the hurt guys and seemed more concerned with his 1/8 scale buggy. I could only imagine if it was a child that got hit, would have done some serious damage to a little body !!!!
A couple noobs got thier TRX rustlers flattened by people driving through, carelessness will cost ya !, One was salvagable the other was a total loss.O-well you stupid tool.
I'm having second thoughts about driving out there ? It's getting bad, no one pays attention to what anyone is doing, wreckless abandon ! NO, I wish I had video ! SORRY.
There was about 50-60 people out there with no organization what so ever, just mayhem. I sat back and sold some Lipos and Motors and watched this all unfold, was truely priceless.
When it did settle down several guys where clicking off high 70's and low 80mph passes. No one had a RC that was truely set up for speed passes I thought. Everyone had big wings on the back, and/or running 4s and geared a mile high so they'd thermal after 2 passes. The guys with 1/10 scale stuff were clocking some fast passes 80+ but were wrecking every other pass, couldn't control it for what ever reason ?

You mean lincypoo? I thought it was the concensus that he was my lincypoo. I guess I'll share, but I'm watching.

It sucks that the group you're with aren't being responsible. I hope the driver that hit the bystanders gets to pay for that guys hospital bill.

When I see that kinda crap I take it upon myself to tell kids and bystanders to stay out of the way. I'm actually a dick about it, but it gets the point across and keeps people from getting hurt.

I also tell wreckless drivers in no uncertain terms that at speed r/c's are more of a weapon than a toy.

Speak up dude! Instead of losing a good spot and a good time step up and organize things. Most people are followers and won't even mind:yes:

That is what I do. It's hard to find a good spot to do speed runs, so step up. Put up boards like I do. Keeps the goofballs in check. And it's true that most are followers and will end up helping you. When I do find time to race, I setup the boards at my LHS parking lot. People just offer to help setup and tear down. The longest part is sweeping/blowing the dirt off and spraying soda down.

I'm hearing what you guys are preaching but I only attend this scene a couple times a month plus the crowd is mixed with a bunch of wanna-be thugs/punk ass kids whom arent gonna want to hear this. I couldn't possibly consider wasting my time with these jackholes. Last night was a lesson learned by the parents whom had younglings in tow, the kids were chucked into PU beds after that incident. A lot of people (whom had a some common sense) were shocked to see how these guys were hurt and I'm sure their driving habits and RC courtisey will hopefully improve ?
The action comes in waves, sometimes there will be a 20 or more idiots going at it doing their own thing all together and five minutes later no one is running. I'll just have to carefully pick and choose when I run and when I test it'll be much earlier when the crowd is thinner. I just need to get my own radar gun so I'm not dependant on the other guys.

yep! your own radar and camera man would be best! then find a nice low-to-no traffic street and shoot for the stars!

thats my plan at least...

You may find GPS easier for solo testing? I also run clear covers so I can read the GPS without unpacking/unclipping everything...

Talking of testing, I've always found quiet testing easier & more productive when trying different setups. With a lot of people or distractions around - everything (except crashes) seems to take much longer to get right. I drive 40mins for all my high speed runs...the road I use is 4 cars wide & long enough that I can't see which direction the dot is facing when I drive to either end, it has a couple of small bumps & a moderately coarse surface...it runs parallel to an airport in an industrial area, nobody around except for a friendly security guy who watches out his window. Parked cars are unusual also. For all the high speed passes with spectators, they've been in the back of a truck parked off the road

I haven't had a crash where the car has become airborne for more than a few feet (maybe I run too much downforce!?) but they slam into the gutter (kerb) with enough force that the scratches & chips in the formed concrete are still easily seen...those impacts would have done major damage to an ankle or leg, especially my 8T + 6S 6500 Hyperion - it's a big pack :lol: