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Old 01-31-2006, 12:00 PM   #31
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Originally Posted by Spud_J
I think that there is one critical difference however that separates models cars from full sized cars and that is you are not sitting in it driving! When driving a full sized racecar on the limit you are constantly reacting to what you are feeling through the seat and the wheel. When driving a model car you are reacting to what you SEE which is a much slower process and of course the given condition has then already happened (understeer/oversteer rtc..). Some element of chassis flex makes the car much more forgiving and driveable. Seting it up theoretically as you would a full sized car makes it too unforgiving and responsive for our tired old eyes then brains to keep up...then we crash!
Very good point.
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Old 01-31-2006, 02:14 PM   #32
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I did another experiement with the Losi XXXS. This chassis has a center box tube frame. The box is completed by the cover on the bottom which is nicely keyed to the chassis and secured well with multiple screws. This cover adds 50% (measured) to the chassis stiffness. I tried running the car without the cover. I made good efforts to retune it. I never got a good feel to it. It felt, well, rubbery, and lacked the steering precision and predictability it had before. This was also at Reflex on High Grip indoor asphalt.

Last edited by John Stranahan; 02-01-2006 at 06:17 AM.
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Old 02-01-2006, 07:25 AM   #33
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Originally Posted by ChadCapece
TC4 came up with nothing new. Infact, the Pro4 CAN be stiffened or softened with the center chassis brace. Somehow, that mag failed to mention that part during their review.
Those idiots! Wait ... maybe the point was the FT TC4 was designed to run well out of the box on asphalt and carpet where as the Pro 4 actually needed a new chassis to perform at its best indoors on the fuzzy stuff? Maybe they believed the changes you can make to the Pro 4 were subtle when compared to the more whole-sale changes the FT TC4 allowed in chassis stiffness? Nah, they just failed. Those idiots!
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Old 02-01-2006, 08:11 AM   #34
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over here we are playing around with a tub conversion for the yoke SD made out of carbon fibre
really stiff this chassis , very hard work on carpet with slicks to get hooked up (high grip), suffer`s from grip roll big time
so now we are going to a softer chassis with a bit more flex from side to side
not back to front
just had a host of big indoor carpet meeets (all slicks on carpet)
nearly all won with flexi cars
IE: hot bodies,yoke BD ,415, also noticed no shaft`s

there is a reason why the big car makers make cars with flexi chassis
setup window is bigger, thus nearly all would be buyers (olod or young) can get the car to work straight off
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Old 02-01-2006, 01:33 PM   #35
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it all depends on a number of factors.
remember f1 cars have a lot more grip then what our cars do even on the highest of grip carpet tracks.
manufacturers have to compromise.they dont know what one person wants from a car to the next.
one person may run low grip ashphelt were you want a thin chassis for flex AND lower roll center.
another person with the same car may race on SUPER HIGH GRIP CARPET WITH FOAMS.
whats the easiest way top please both.put in settings that can adjust the car.
i go for a 3 mm chassis on carpet and a 2.5mm for outdoors.
by adding or taking away parts that link the top and bottom deck can cause tweaking.
thats why a lot of car makers do option chassis sets.
iam sure this way is better then going with add on stand offs chassis brases as these can cause compromise and tweaking.
il always go with a softer car outdoors and a stiffer one indoors.
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Old 02-01-2006, 04:17 PM   #36
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I hope that variable stiffness chassis become popular. That way we can keep taking it out of them and making aftermarket carbon fiber bits
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Old 02-02-2006, 01:15 AM   #37
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Just incase your wondering about our tub chassis
click here for a gander http://www.fibre-lyte.co.uk/fl/cars/...r4tcsdtub.html
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Old 02-02-2006, 02:42 PM   #38
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Quote:
Originally Posted by Jon Kerr
The way I see chassis flex is that it greatly depends on the car itself, suspension geometry, and track conditions. A more flexible chassis will create more grip most of the time. Sometimes too much. It can make the car feel like you're driving a Caddy. A stiffer chassis can, in some cases, take away some grip and let the car flow through the corners better and react more quickly..

Let me say that any chassis flex works like a crutch in your cars setup.
Its like compairing a go-kart to a cars suspension.

When you have a chassis that is flexing over time the chassis would
change.

A stiffer chassis and lighter springs is a more practical approach.
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Old 02-02-2006, 02:51 PM   #39
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Quote:
Originally Posted by Mr RCTech
Let me say that any chassis flex works like a crutch in your cars setup.
Its like compairing a go-kart to a cars suspension.

When you have a chassis that is flexing over time the chassis would
change.

A stiffer chassis and lighter springs is a more practical approach.
Many US drivers still insist a stiffer chassis is always better, that's why US drivers did so bad in last TC world championship in Florida.
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Old 02-02-2006, 03:36 PM   #40
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Personally, I'd rather have a chassis that was designed for a specific application. I do not want to have a chassis that is designed for all applications as a chassis that is designed for all applications may be good all the way around, because with all things being equal, it will not as good on carpet as the same car designed for carpet and it will not be as good on asphalt as the same car designed for asphalt...you cannot have everything.

And by the way, I love how people think they can compare RC cars to real cars...there is a slight difference between the 2 and it's just not scale.
It's kinda like putting 0-30 weight automotive car oil in RC bearings because if it works in a 5000 pound car with 500 hp it has to be good for RC car bearings!
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Old 02-02-2006, 04:03 PM   #41
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Koabich-Be kind to us and point out exactly what those differences are other than scale that you mentioned, and the relatively stronger material for its size that results from a small scale. I'll point out a few of the similarities. To make it easier lets discuss rubber tired cars with standard front ball diff or gear diffs as not too many fullsize race cars run a locked front diff or foam tires.

1. The chassis has flex on full size cars; eliminating this would require too much of a weight penalty.

2. The roll stiffness of the front and back of the car tunes exactly like the full size car (Spring and Anti roll bar changes).

3. Roll center changes tune exactly like on a full size car. I have personally changed the roll center spring stiffness and sway bar on my full size 300 Horse Power touring car. The effects are very similar to several of the RC touring cars that I have owned.

4. The Tire loading vs traction curve is identically shaped for both, which affects exactly how items 2 and 3 are used. I have measured this.

5. F1 cars corner at 3.5 g's. A good full size touring car with a few aftermarket parts is over 1 g. An RC touring car on very high grip indoor asphalt is limited to about 2.8 g's. A touring car on carpet will lift both inside wheels at 3.5 g's so maximum cornering potentials are very similar.

6. Note that you can talk about a scale distance, but talking about a scale speed of 400 mph is ridiculous. 400 mph is 400 mph. If the car is not designed very strong pieces will fly off at this speed.

7. Power to weight ratio about 1 horsepower per 9 lbs for an RC touring car, about 1 horsepower per 2 lbs for an F1, about 1 horsepower per 3 pounds for a rally race car or Touring race car.

Last edited by John Stranahan; 02-02-2006 at 04:56 PM.
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Old 02-02-2006, 07:04 PM   #42
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Quote:
Originally Posted by NHRCRACER
Those idiots! Wait ... maybe the point was the FT TC4 was designed to run well out of the box on asphalt and carpet where as the Pro 4 actually needed a new chassis to perform at its best indoors on the fuzzy stuff? Maybe they believed the changes you can make to the Pro 4 were subtle when compared to the more whole-sale changes the FT TC4 allowed in chassis stiffness? Nah, they just failed. Those idiots!

Have you ran both cars? If you have, then you'd already know that the Pro4 is very stiff with the center brace, and the BMI chassis is more of a psychological hopup, than physical part improvement. The guys that write the magazines do so many reviews that it's going to be hard to really "know" a car in and out in a few weeks time. So when they publish something like the Pro4 must have <$100 put into it to run on carpet, I call it out so that the guys reading this won't pass off that car b/c what a magazine told them.

Here's the original quote from the magazine: "On the other hand, to tune the Pro4 for carpet, you need all new top and bottom chassis plates (costing big $$$ and lots of time to move parts over)."
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Old 02-02-2006, 07:24 PM   #43
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Quote:
Originally Posted by John Stranahan
Koabich-Be kind to us and point out exactly what those differences are other than scale that you mentioned, and the relatively stronger material for its size that results from a small scale. I'll point out a few of the similarities. To make it easier lets discuss rubber tired cars with standard front ball diff or gear diffs as not too many fullsize race cars run a locked front diff or foam tires.

1. The chassis has flex on full size cars; eliminating this would require too much of a weight penalty.

2. The roll stiffness of the front and back of the car tunes exactly like the full size car (Spring and Anti roll bar changes).

3. Roll center changes tune exactly like on a full size car. I have personally changed the roll center spring stiffness and sway bar on my full size 300 Horse Power touring car. The effects are very similar to several of the RC touring cars that I have owned.

4. The Tire loading vs traction curve is identically shaped for both, which affects exactly how items 2 and 3 are used. I have measured this.

5. F1 cars corner at 3.5 g's. A good full size touring car with a few aftermarket parts is over 1 g. An RC touring car on very high grip indoor asphalt is limited to about 2.8 g's. A touring car on carpet will lift both inside wheels at 3.5 g's so maximum cornering potentials are very similar.

6. Note that you can talk about a scale distance, but talking about a scale speed of 400 mph is ridiculous. 400 mph is 400 mph. If the car is not designed very strong pieces will fly off at this speed.

7. Power to weight ratio about 1 horsepower per 9 lbs for an RC touring car, about 1 horsepower per 2 lbs for an F1, about 1 horsepower per 3 pounds for a rally race car or Touring race car.

This argument has been made many times before so I will not get into it here, but yes as you stated general rules of physics apply to both...but both are not identical. Both are not going to behave the same under all conditions.

Real cars do not run belts and have batteries and electronic motors. Most do not have 4WD and run on carpet with foam tires then considered with the fact that the scale speed is what...300MPH...I don't think we are comparing apples to apples here. I am not an engineer but I ould bet that the weight difference is not exaclty scale either...I bet an RC car is much lighter than it's real counter-part throwing another wrench into the mix and further effecting how one reacts to changes or adjustments compared to another

The point I was trying to make was not that camber on one effects the other differently or that anti dive does this or that.

The argument made above, which my comments was responding directly too and nothing else, was the fact that someone stated "using chassis' with more flex in RC to gain more traction is stupid because engineers with real race cars don't do the same thing." That is just a stupid argument and an irresponsible comment.

It's really funny that one would expect both real cars and RC cars to react and behave in exactly the same way under all circumstances.
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Old 02-02-2006, 07:39 PM   #44
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I had some flex/stiff test with my 415, driving on asphalt. I have compared 1 topdeck and 2 topdeck (no CA glow between). With same setting everywhere else, 2 topdeck indeed reduce the overall traction and make car slide away from my drive path. However, car also react faster to my command. With 1 topdeck, the setting is easier to get a good driving setup. With 2 topdeck, I need lots more suspension work to get a setup which good for each parts of track.

After I go with TA05, I also experience the same situation when I put the aftermarket topdeck into TA05's flex tub chassis. Car response faster, but lower overall traction. A setup rework is needed for topdeck.

IMO it's not necessary to be which is better, it's all depend on the track condition (layout included), setup, and the way you drive. I now mainly play with a bit flex car because I'm lazy to find the right setup as it's more hobby for me than competition, so anything that reduce work load is good choice to go
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Old 02-03-2006, 06:43 AM   #45
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Quote:
Originally Posted by Mr RCTech
A stiffer chassis and lighter springs is a more practical approach.
That sounds right but in practice it never works.

I keep seeing people saing that you run stiffer springs with a fllexy chassis. This is not at all true. All the fast cars with 2mm chassis are running springs in the 13-17lb range (thats pretty soft).
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