Why chassis flex? (Sorry noob ?)
08-21-2014, 03:28 PM
#31
Aerodynamicists in both the aviation and automotive industry constantly yearn for ever-larger wind tunnels so that they can more accurately predict what will happen on the actual vehicle.
Small models are actually less aerodynamically efficient than one might guess, because they operate at lower Reynolds numbers. Small model airplanes don't generate lift as readily as real airplanes, and small model cars don't generate downforce as readily (though it can still be substantial). Imagine how good these things would stick to the track if the air were 10 times thicker!
08-21-2014, 11:45 PM
#33
In RC cars , more flex means more grip ( better cornering ability, feeling more planted, higher cornering speed @ tight turns ).
08-22-2014, 12:56 AM
#34
08-22-2014, 02:51 AM
#35
I see it this way:
1:1 scale cars mostly made of metal, bolted/welded together so when it flexes it doesn't snap back like plastic tub or carbon fiber chassis. I've seen a chassis/body alignment rig, basically it checks for tweaks then twists the whole car while being hoisted (without engine, tyres, etc) back to its specs. Maybe that's why race cars are reinforced not to tweak or flex because once it does, it stays thay way.
In my experience, a soft chassis is easier to drive but will be slow when pushed hard or driven aggressively, example is a TA05R, that kit feels like a rubber.
On the other hand, a stiff RC chassis is nervous to drive without downforce from let's say protoform body. But will be faster if driven aggressively and is sensitive to set up changes and surface conditions.
1:1 scale cars mostly made of metal, bolted/welded together so when it flexes it doesn't snap back like plastic tub or carbon fiber chassis. I've seen a chassis/body alignment rig, basically it checks for tweaks then twists the whole car while being hoisted (without engine, tyres, etc) back to its specs. Maybe that's why race cars are reinforced not to tweak or flex because once it does, it stays thay way.
In my experience, a soft chassis is easier to drive but will be slow when pushed hard or driven aggressively, example is a TA05R, that kit feels like a rubber.
On the other hand, a stiff RC chassis is nervous to drive without downforce from let's say protoform body. But will be faster if driven aggressively and is sensitive to set up changes and surface conditions.
08-22-2014, 05:30 AM
#36
I see it this way:
1:1 scale cars mostly made of metal, bolted/welded together so when it flexes it doesn't snap back like plastic tub or carbon fiber chassis. I've seen a chassis/body alignment rig, basically it checks for tweaks then twists the whole car while being hoisted (without engine, tyres, etc) back to its specs. Maybe that's why race cars are reinforced not to tweak or flex because once it does, it stays thay way.
In my experience, a soft chassis is easier to drive but will be slow when pushed hard or driven aggressively, example is a TA05R, that kit feels like a rubber.
On the other hand, a stiff RC chassis is nervous to drive without downforce from let's say protoform body. But will be faster if driven aggressively and is sensitive to set up changes and surface conditions.
1:1 scale cars mostly made of metal, bolted/welded together so when it flexes it doesn't snap back like plastic tub or carbon fiber chassis. I've seen a chassis/body alignment rig, basically it checks for tweaks then twists the whole car while being hoisted (without engine, tyres, etc) back to its specs. Maybe that's why race cars are reinforced not to tweak or flex because once it does, it stays thay way.
In my experience, a soft chassis is easier to drive but will be slow when pushed hard or driven aggressively, example is a TA05R, that kit feels like a rubber.
On the other hand, a stiff RC chassis is nervous to drive without downforce from let's say protoform body. But will be faster if driven aggressively and is sensitive to set up changes and surface conditions.
08-22-2014, 11:52 AM
#37
second that. the carbon reinforced parts are the same material as the arms so they are pretty stiff. The stock one is pretty soft though. But I remember the original TA05 was easy to drive and it's probably due to that soft chassis.
08-22-2014, 06:25 PM
#38
Flex in the 1:1 world depends on the construction of the car but adding stiffness to the car is always recommended as it makes the suspension work like it's supposed to. That being said some flex is still wanted as a completely solid car will be very hard on mounting and stress points. Too much flex though will make the car unpredictable as there's no way to control it
08-22-2014, 10:44 PM
#39
Few points some of which have probably already been covered.
Shocks used in RC do not damp high frequency vibrations well. Flex in the chassi helps keep the car stable and damp out these vibrations. (With foam tyres the tyre damped out the vibrations and the chassis were designed to be very stiff)
Different roll centers front and rear, torsional flex helps to allow both ends of the car to roll different amounts slightly to optimise performance at both ends of the car.
Wider setup window which allows more margin for error.
Couple of other points, real cars flex too, standard production cars flex a lot more than a RC car.
In one class of race car the chassis are setup so that they have 10 times more redgidity of the suspension. Ie if the suspension compresses 20mm under load the chassi with flex 2mm.
Shocks used in RC do not damp high frequency vibrations well. Flex in the chassi helps keep the car stable and damp out these vibrations. (With foam tyres the tyre damped out the vibrations and the chassis were designed to be very stiff)
Different roll centers front and rear, torsional flex helps to allow both ends of the car to roll different amounts slightly to optimise performance at both ends of the car.
Wider setup window which allows more margin for error.
Couple of other points, real cars flex too, standard production cars flex a lot more than a RC car.
In one class of race car the chassis are setup so that they have 10 times more redgidity of the suspension. Ie if the suspension compresses 20mm under load the chassi with flex 2mm.
08-22-2014, 10:51 PM
#40
I would stick with the basics (only one of which has to do with this thread):
1) Increase the torsional rigidity of the chassis.
2) Lower the CG by laying the dampers down, or using rotary (or other) dampers.
3) Make the bump spring rates, roll spring rates, and damping infinitely adjustable.
4) Make the bump springing and roll springing mechanisms independent from each other.
(Items 2 and 3 are already being done in the Awesomatix design.)
Then I would consider other, more esoteric items. For instance:
Active differential, so coupling can be varied in real-time depending on torque, velocity, or some other selectable parameters.
I'll stop here, since these items are best discussed (and have been discussed) in a different thread.
1) Increase the torsional rigidity of the chassis.
2) Lower the CG by laying the dampers down, or using rotary (or other) dampers.
3) Make the bump spring rates, roll spring rates, and damping infinitely adjustable.
4) Make the bump springing and roll springing mechanisms independent from each other.
(Items 2 and 3 are already being done in the Awesomatix design.)
Then I would consider other, more esoteric items. For instance:
Active differential, so coupling can be varied in real-time depending on torque, velocity, or some other selectable parameters.
I'll stop here, since these items are best discussed (and have been discussed) in a different thread.
08-23-2014, 11:34 PM
#43
Well I'm glad I asked! Been a lot of interesting points brought up. I'm wanting to pick up a used roller for 17.5 class and have been debating between the tc4 and the tc5. That's what spawned the question in case anyone was wondering. Thanks folks!
08-24-2014, 06:17 AM
#44
Tech Apprentice
08-25-2014, 12:17 PM
#45
Thank you Christian
(...for making me want a Yokomo)
http://www.eviltwinmotorsports.com/?page_id=204&page=3
(...for making me want a Yokomo)
http://www.eviltwinmotorsports.com/?page_id=204&page=3
Thanks for posting this. A great article!
Chassis flex will be around until every driver has a team of engineers and full data acquisition equipment on their car. RC Cars are unique machines that require unique design solutions.