fredswain

iTrader: (1)

The problem is that you are going off of the balance technique from early in the thread. That was several years ago before we had big bores and the wide variety of spring rates to choose from. I look for a certain geometry now where at max compression, the shock is at a 90° angle to the arm. The arm is "level" as referenced from the inner to the outer hinge pins, not the physical shape of the arm. That's actually why I don't like gull wing arms. It makes it tough to visualize things.

micholix

Ok!
Is that where you start your test, by having the shocks at full compression by 90* angle to the arms?


Edit: sorry guys for highchecking this thred!

fredswain

iTrader: (1)

It's my goal but the important thing to know is that a spring has the most leverage when it is perpendicular to the arm. I want max leverage to be at max compression, where it's needed the most. This isn't always possible. On the 210 I use the outermost upper mount points on the rear tower. On the DEX8, it's impossible to achieve unless you switch to the DEX8-T towers. I generally want each end to have the same leverage at the same point in suspension travel. This is actually impossible with equal length arms and a front end kick but we can get it close enough. From there it's all about finding the spring rates that balance.

WallyRC

Fred, I just got the carbon b44 front shock tower in. I think it will work perfectly once I hit it with the dremel to get it to fit. I am shooting for about 3-4mm rise. Looks like the shocks and arms will be perpendicular st full compression. Will post pics once done. May be a week or so.

Micholix. Don't worry about highjacking the thread. Good information for all of us. Maybe you can start a new thread Fred. About your balancing technique. Would love to hear more on heave. If you start it maybe that gives you the right to block the morons from it.

Thanks

banx

fred thanks for taking the time to type all of that out. I agree with what your saying. I feel like theres a ton of people, myself included that don't fully understand the physics.

making changes to the car because of misconceived notions. I did that a few times myself and ruined a couple of heats because what I thought I was doing was going to give me x result. and it didn't.

that being said, theres a few lines in that post that resonated because I have heard them before from the fast old guys. 1. getting the car to rebound on all four corners at the same time. hugely important...... and 2. was running stiffer springs upfront in a 2wd.

with regards to setup sheets. i hear what your saying, but to a novice like myself, I found them great. on my previous cars I had several printed out based on the track I would be going to.... what changes I made and the perceived outcome. these sheets evolved over the seasons.

your comments on kickup in regards to 4wd vs 2wd are interesting. It seems that there are a few people that think along the same lines as you.

makes me want to order a sheet of 3mm carbon fiber and make a chassis without any kickup hahaha

is there a correlation between kickup and steering akerman?

fredswain

iTrader: (1)

I have no desire to start a thread on the topic. I don't need for it to devolve into name calling and insults by people who can't understand that it's structured advice that they can either try or not try and not some new federal law that they are required to live their lives by. Some people take things way too seriously, especially when their beliefs are challenged.

My gripe with setup sheets isn't aimed at the beginner who hasn't yet learned anything. It's aimed at the people who claim to be hardcore racers who give advice to others without any fundamental understanding as to what that advice is truly saying. I'm generally pretty hard on the pros when it comes to setup sheets. To the point that I'm sure it sounds insulting. The reality is that I'm not actually calling them all dumb. I am saying that they have a natural driving talent that got them where they are but they may or may not be truly knowledgeable on tuning. How can we tell? Did they figure something out through understanding, blind trial and error, or through another team mate? We don't know. With modern tracks being so similar anymore in terms of grip, I question anyone who keeps publishing new setup sheets that are quite different from the previous. If the conditions are hugely different such as loose dirt to carpet, I understand but it's generally a red flag for me. It in know way is calling the pros idiots though.

Ackerman would be affected by a change in front end kick but it isn't tied to front end kick. It's merely a geometry issue and a change in front end kick is a change in front end geometry that just so happened to affect ackerman.

30Tooth

iTrader: (1)

@Fredswain, I have a couple questions about kick up and the results you are after. Can I send a PM?

fredswain

iTrader: (1)

Go for it

banx

hahahaha guess you can't challenge anyones beliefs on politics, religion, AND rc racing.

I'm pretty sure it won't help you sleep better at night, but most of the setup sheets I printed off for 'carpet high traffic' on petitrc.com were very similar to each other. the oil weights were generally off only by 5.... like 25wt vs 30wt, 30 vs 35 etc. and sping selection was always only off by one colour.



the reason I find your thoughts on kick up interesting is because about 12 years ago I had a 1/18 scale track in my back yard. (anecdotal as hell, sorry) But I took a mini-t and made an extended chassis for it and ordered this blue groove buggy body. anyways it had minimal kickup because of how I built it. without actually knowing what kickup was......once i got the bumpsteer figured out it drove way the hell better than the mini-t did. I mean way the hell better and I didn't know why. other than 'increased chassis length increases stability'

have you considered fabricating a minimal kickup chassis for a 2wd? you know, for $hits and giggles

WallyRC

Had some free time and modified it. Turned out great. With full compression shocks still have about 3mm of uptravel. Angle is dead on perpendicular at full compression.

Will post pics but can't figure it out on my phone. Ugh

WallyRC

This was the basic shock tower. 3 mm.
Xtreme racing makes a nice 4mm one that has multiple holes that I think could be used with gullwing or flat w/o having to change shock towers. About 20 bucks. You will need the aluminum shock mounts from and exotek or STRC shook tower. Good luck dremelling. I bolted
my ST shock tower to it to use as a template when dremeling the base.

Edit: just thought of this that you need to drill the wholes a little larger for the shock attachments. So maybe the Xtreme ones wouldn't be good because of lack of material. Just find thicker b44 ones.


http://https://www.amazon.com/photos/share/LoPy6qUWffYgglRX1nv6qF9CBjpAkIC5ver81TzaCye

micholix

Wally, well done and great to hear hat the b44 tower fits!

Alan_r

Can someone explain to me again why the up travel on the V3 is an issue? What is happening on the track where this flaw is showing? What is being gained by this small increase in uptravel that will result in either: Lower lap times, more consistent driving, makes it easier to drive consistent fast laps.

Way back when, on the original RC10's we used to do this.Some of you may remember the tall front towers that became the rage. Then M. Hirosaka won a title with his car set up that way. But this was due to the horrible short shocks we had back then. Surely the modern Durango 12mm's aren't holding us back that much. Or are they? Just curious. I had started to do through my parts bins looking at front towers to possibly modify but I got lost trying to understand why.

WallyRC

I will try and explain to the best of my knowledge. The main reason is when they went from V1 ---> V2&3, they changed from gull wing to flat arm. Good change. But the shock tower dimension remained the same. Bad. They shifted the attachment back a little to get to the inner camberlinks easier. Now you lost up travel. The shock body did change in size I believe from 23 to 21.5. Not enough.
When people are running lower ride heights especially on AstroTurf/ carpet the front outside shock will bottom out on hard cornering or even landing the car at an angle. Once the shock bottoms out the car gets unsettled. Can wash the rear end out, traction roll, etc.
Just push your car all the way down until the chassis hits the ground. Now try and lift the front wheels up. Nothing. You should be able to lift them up a little. Because when cornering the chassis leans. We don't land perfectly level all the time too. If on carpet or turf you can just run the gull wings. But in dirt/clay they really dig in and you loose ground clearance.
Hope this helps.

fredswain

iTrader: (1)

The V1 never had enough up travel either. The gullwing vs straight arm issue didn't change that, even though the shocks changed. They designed this car around the B4 geometry but the Associated shocks compress more than the Durango, causing this problem. If you ran AE shocks on your car, you'd be fine.