Are people thinking about rc performance all wrong today?

[Charlie don't surf]

Why do both ends have to have the same rate of bound and rebound in relation to each other?
How do springs and oil not effect cornering?
What do you do about the jumps?

I'm still curious to find out about these-

[RETRO R/C]

W O W

Entertaining to say the least!!

And I have only bothered to read the last couple of pages!!

Cheers

Darryn

[adam lancia]

When I get back from physio and practice, I'm throwing a bag of popcorn in the microwave and re-reading the last 5 pages. Yes, there will be German beer also involved

[minichamps11]

Someone mentioned using A&L style trailing arms in rear to save weight.... these are bad if you want your car to handle well. Trailing arms don't have the same range of tuning or offer the same camber control during wheel travel versus double wishbone. MacPherson strut design has the same issue despite being light and simple. A chassis needs a multi-link system to get full toe/camber control, but then you have a weight / packaging penalty, not to mention the slop from the tolerances & wear on multiple joints.

Something else I've just thought of: A lightweight mid engined car won't get any benefit from the motor's inertia when the car is a) at constant throttle or b) off throttle, i.e. when entering a corner. In these circumstances you'd get no benefit from the 4 gear transmission and the mid engined car's rear axle is going to have a significant grip disadvantage versus a rear engined car (especially during braking with the weight transfer forwards). It's for this reason that most popular UK X6 setup runs Losi black (4.5lb) front springs and Losi pink rear (2.3lb) with lots of rear droop. (EDIT: Stiffer front springs also needed on X6 because a greater proportion of the car's weight sits over the front axle compared to rear engined car)

Comment about short shocks on an off road car - best avoided. A good guideline is to ensure there is enough suspension travel upwards for the wheel to have some additional movement, even when the chassis is flat on the ground (about 5 -10mm ). This sounds unnecessary until you a) consider what happens when a buggy lands skewed to one side from a big jump, or b) look at a decent close-up photo of a 1/10th buggy cornering at speed on a high grip track (like this http://www.oople.com/rc/photos/2011national-stotfold/2WD/gallery/DSC_0857.html. Secondly 1/10th off-road cars need loads of droop and you won't get this with a short shock unless you mount it a long way inboard on the suspension arm and screw up the wheel rates/piston velocities.

One way round this is to use a TTech / F1 style inboard suspension system, as Fredswain already mentioned. Somewhere in this thread the Topcat is mentioned as being a bad example of this. The Topcat inboard front suspension system was a flop was because it was a flawed design; in rebound the spring and front wheel become disconnected as there is no permanent joint between the two (the rocker simply pushes up against the rod fixed to the lower wishbone) so you loose all rebound control TTech system was very well designed but too revolutionary for off road 1/10th and few people understood how to correctly tune it.

[fredswain]

There was a thread on rctech called "tuning with camber links". That's the place to go to see what the long more in depth tuning discussion was. Ultimately the information was never completed due to a combination of the doubters who refused to try the method saying things like "it's all theory" and "I copy the pros" who would then do all they could to argue against it. It also got off topic at and some point my old attitude pretty much topped it off. I can't help it!!!

It would be a good thread to restart here somewhere. There were many people who starting tuning like that who had very positive results.

I will ask a quick quick question for those here to ponder. It was asked why do you want the same rates front and rear? Effective rates are the key so the key is to have balance between front and rear. You want it proportionate. Going back to the question, why do we want it equal front and rear? I'm going to answer that with a question. Why do you want balance between the left and right sides of the car? Keep in mind we aren't talking about oval racing. When you question it from side to side it sounds a bit silly. Why doesn't it when you question it front to rear?

[Charlie don't surf]

Because equal spring rates between front and rear does not transfer weight properly during cornering, acceleration, deceleration with uneven weight distribution.

Now, since you brought oval into the mix- and that is where all my state and national A main wins, TQ's and qualifiers are. I always used equal rates on the left and right springs. Just to make sure you know where my pedigree on the subject stands.

Let me ask you this,
1) what does caster do on a passenger car?
2) what does caster do on a race car?

[cautrell05]

Over all this is a pretty interesting discussion. I agree with fred about going with a mid motor as the weight drops. At some point you need to move motor forward to keep from getting too much rearweight. Personally I think the biggest advantage to the mid motor is the weight is more centrally located instead of running full length like most of the "normal" buggys are. Im not totally sold on the motor rotation thing though. Its one of those things that sounds good reading it. However I think they are trying to relate to the same force that makes your V8 powered car rock when you hit the gas. My short course truck has a 17.5 in it. With the tires off If I snap the throttle wide open there is no rocking force at all. Thats with it balanced on two fingers so any motion will be noticed. My frankenbuggy has a boosted 10.5 in it. Same test, tires off balanced on two fingers the nose will just barley lift up when I hit full throttle. Maybe 1/4 inch. However thats with the motor going from full stop to full rpm in probably 1/2 second or less. On the front stretch it takes 1-2 seconds. Run the motor up at the same speed as it accelerates on the track and there is no noticable force at all. Holding it in my hand and I dont feel anything. Gut feeling? The 4 gear thing is a sales pitch with a good theory to go with it.

Weight distribution is critical. Not just corner weights but how far out or close things are mounted. I know its comparing aples and oranges but my mid motor short course truck right now is balanced at 59.7 rear. My buggy is at 63 with the motor hanging off the back. The truck is predictable and is kinda hard to spin out on entry but once it starts to go its easy to catch. The buggy on the other hand, when it starts to spin theres no catching it. once it starts to spin it just keeps going. Like I said its not apples to apples but there is a very big difference.

Just random thoughts.

Nick

[fredswain]

I''m not talking about even spring rates between front and rear based on what static spring rate the springs are advertised at on paper. You'll typically see a higher spring rate number on front springs than rear springs but they also mount more inwards which makes them less effective. That means their effective rates are different based on mounting points. It is effective rates that matter, not static rates. When you balance effective rates, weight transfer should also balance. The caveat to that of course is under braking and has to do with grip. On a rear wheel drive car our only brakes are the rear wheels. We need weight to transfer more heavily onto the front end to develop grip. The easiest way to do that is to add front end rake to promote front end weight transfer. Sadly not all cars have adjustable rake but it would be a fantastic fine tuning tool. Some have had it in the past and the 22 currently does. 4wd cars don't have the extreme front end rake because they don't need as much weight transfer forward. They already have a greater percentage of weight on the front end and all 4 wheels contribute to braking.

[Charlie don't surf]

So you are saying a 10lb front spring, mounted on a 30 degree kickup and a 30 degree shock angle from the arm to the tower has what rate in.the end?

[fredswain]

First off that's not enough information but second the effective rate is going to be less than 10 lb. Don't believe me? If you lay that shock over 90 degrees and don't provide a means for that shock motion to be transferred sideways with a linkage, can the shock hold the car up? Of course not. It's got an effective rate of 0. If you mount the bottom of the shock to the inner hinge pin with the top mounted on a tower, what is the effective rate? It's zero. It has no leverage on the suspension arm at all due to where it is mounted.

[Charlie don't surf]

Ok then, top over the inner hinge pin, bottom in the middle of the arm

[scr8p]

8 pages and no car built yet.

it's like one of my build threads.

[Charlie don't surf]

8 pages and no car built yet.

it's like one of my build threads.

Not quite like yours-

[adam lancia]

You two are gonna make me throw another bag of popcorn in the microwave if you keep this up

[Charlie don't surf]

Nope, I'm done- his topic is legitimate and is worth discussing, and a lot of people have thrown some great info and ideas into the ring and creatively tried to adress the question posed. However the topic starter will not accept anything that is outside his own "knowledge" ( although for a proclaimed ME he doesn't adhere to the creative process well ) and only answers questions asked in long round about responses or with rhetorical questions, or does not answer the question at all.

Funny thing is, this member modus opperandi has been seen here before, twice in fact with two different screen names and just seemed to stir the pot for the sake of it. But maybe I'm wrong-

Either way, back to the ignore list for this guy-