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Getting a plastic chasis to behave like a carbon fiber one on a budget.

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Getting a plastic chasis to behave like a carbon fiber one on a budget.

Old 01-28-2020, 12:57 PM
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Default Getting a plastic chasis to behave like a carbon fiber one on a budget.

Hey! I'm looking to race touring cars on a budget. Everyone I've talked to swears by their carbon fiber chasis for TC. Carbon fiber and plastic have similar densities, so it seems like chasis flex may be the x-factor due to the better torsional properties of carbon fiber. My current plastic TC chasis is single-decker for the most part, so I'm wondering what my best options would be to stiffen up the chasis without shelling out crazy amounts of cash. I'm wondering if creating some sort of front-rear sway bar or lining the outside of my chasis with some less flexible material like wood might help. It seems like the most flex is in the front part of the chasis where it's thinnest.
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Old 01-28-2020, 01:13 PM
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What car are you running first..that would be the most help.
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Old 01-28-2020, 01:16 PM
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The densities are similar, but their compression, and tensile strengths are not. Neither are their sheer strengths. Injected molded polycarbonate or nylon is going to have better sheer strength than your typical carbon or even fiberglass.

If you're interested in your specific case, we need to know what chassis it is.

It's worth noting, that a flexible tub, generates MORE traction than a stiff tub. If you dig through the setup sheets for the TC4 (and likely TC3) you'll find that trimming down the tub to make it more flexible was a common modification.

Twinning, or siamesing material is generally not a good use of material for making things stiffer. You want to create a sandwich to do that. Say you have a tub, you can reduce longitudinal bending by adding a top deck. Depening on how you attach that top deck, it could have little, or no effect on torsional stiffness. Or it could turn the chassis into an I-beam.

Your use of the word "wood" has me a bit concerned, as wood is more varied than plastics, and makes "normal" composites look simple to deal with.

http://www.lightaircraftassociation....nformation.pdf

Some places, stiffness, matters. I've found on tamiya models, carbon shock towers are VERY beneficial after getting oil filled shocks on the car. As the plastic towers act as un-dampened springs.

You can also make material, and interface decisions based on wanting to absorb energy. For instance, Magnesium makes a bad bell (and a good wheel and car material) because vibrations put into it are damped 15 times faster than in aluminum.

https://pdfs.semanticscholar.org/b58...94b4b86a52.pdf

Composites, in general are good at damping becuase of their many material density changes and the interaction of binder versus fiber.

so..... what is your actual project?

Or if you'd like to see someone whos taken a tub from zero to hero... Check out WTCC's build: wtcc's TT-02 KR
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Old 01-28-2020, 01:39 PM
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You (threadstarter) didn‘t mention your budget.
My TT-02 KRv2 conversion is definitely close to the actual middlemotor chassis timewise and moneywise much cheaper than a fulltuned TT-02 or actual carbonchassis car, if you don’t go for all blue bling bling, like I did. Chassisflex sure is important, but my experience with the KR conversions are, that even a standard plastic tub can run with the aluchassis on ETS carpet. That said it is more important to find the sweet setup spot and a balance that allows you to do what you like with the car while being on the limit. And there a full adjustable suspension is important, that doesn’t bend under load.

As far as I know there is no competitive tub chassis on the market right now that runs with the A800s and T4‘20s (and costs 160€).
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Old 01-28-2020, 01:46 PM
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Originally Posted by Nerobro View Post
The densities are similar, but their compression, and tensile strengths are not. Neither are their sheer strengths. Injected molded polycarbonate or nylon is going to have better sheer strength than your typical carbon or even fiberglass.

If you're interested in your specific case, we need to know what chassis it is.

It's worth noting, that a flexible tub, generates MORE traction than a stiff tub. If you dig through the setup sheets for the TC4 (and likely TC3) you'll find that trimming down the tub to make it more flexible was a common modification.

Twinning, or siamesing material is generally not a good use of material for making things stiffer. You want to create a sandwich to do that. Say you have a tub, you can reduce longitudinal bending by adding a top deck. Depening on how you attach that top deck, it could have little, or no effect on torsional stiffness. Or it could turn the chassis into an I-beam.

Your use of the word "wood" has me a bit concerned, as wood is more varied than plastics, and makes "normal" composites look simple to deal with.

Some places, stiffness, matters. I've found on tamiya models, carbon shock towers are VERY beneficial after getting oil filled shocks on the car. As the plastic towers act as un-dampened springs.

You can also make material, and interface decisions based on wanting to absorb energy. For instance, Magnesium makes a bad bell (and a good wheel and car material) because vibrations put into it are damped 15 times faster than in aluminum.



Composites, in general are good at damping becuase of their many material density changes and the interaction of binder versus fiber.

so..... what is your actual project?

Or if you'd like to see someone whos taken a tub from zero to hero... Check out WTCC's build:
Thanks for the TT02 reference!

Currently, I have a TT-02 and a Yokomo YD2S I would be interested in making more competitive in TC and Drift respectively. So the goal would be to increase the polar moment of area of the chasis cross-section by adding another deck if I want to increase chasis performance? Is decreasing bending in the plane perpendicular to the chasis generally desirable/is decreasing chasis twist desirable for TC/drift? Also wondering if there's any way to "virtually" increase the Young's Modulus of the chasis to reduce bending.

I guess the question would be more what properties of a carbon fiber chasis are most important for racing and how one might emulate some part of them for relatively cheap.
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Old 01-28-2020, 02:11 PM
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I've seen this tried with a plastic tub:
https://www.thercracer.com/2019/06/t...-top-deck.html

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Old 01-28-2020, 02:50 PM
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Thanks for the TT02 reference!

Currently, I have a TT-02 and a Yokomo YD2S I would be interested in making more competitive in TC and Drift respectively. So the goal would be to increase the polar moment of area of the chasis cross-section by adding another deck if I want to increase chasis performance? Is decreasing bending in the plane perpendicular to the chasis generally desirable/is decreasing chasis twist desirable for TC/drift? Also wondering if there's any way to "virtually" increase the Young's Modulus of the chasis to reduce bending.

I guess the question would be more what properties of a carbon fiber chasis are most important for racing and how one might emulate some part of them for relatively cheap?

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Old 01-28-2020, 05:52 PM
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The only two chassis i ever ran that were plastic / composite chassis and were competitive with other TC's of the day were the Xray T1R and the TA04R mind you these were different times, Brushed Motors, not so dialed Rubber tires and rim sizes. Since then unless your running the Tamiya Cup, I would say it would be moot point! What Kevin has done with his KR car is awesome and as such it benefits of his engineering to include adding Carbon Fiber. If you want to see how far people take a Plastic Chassis these days, look at the TA07 thread and those still runing the trestle setup on the plastic tub.
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Old 01-28-2020, 06:47 PM
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well, carbon... is cheap? I mean, not the $7 that the hard TT02 tubs are, but it's $30 for a sheet big enough to make two chassis. If you want to augment the stiffness of your chassis... I'd start with carbon tow, and some slow CA and kicker.

https://store.acpsales.com/products/...BoCpHEQAvD_BwE

This is how I reinforce airplanes and sailboats.

"increase performance" is... not something that's easily measured. If you put some carbon tow along the bottom of your TT02, around the rim, and then did a couple crosswize plies, I bet you could double the stiffness of that tub. Would it help you though? No clue. At $7 a tub, it's worth trying.

Now when you stiffen one part of the chassis, that motion goes elsewhere. You'll find that Tamiya chassis that are floppy, come with really stiff springs. This is because they're depending on the chassis to be the spring too. This is a universal truth. Modern cars can both have supple suspensions, and good wheel control because they have stiffer chassis.

This means you'll need to re-tune the chassis if you do a good job. If you don't... well.. you didn't do much. :-)

Not to be silly, at least on the TT02, if you want to "feel" what you've done, you need to have decent shocks, and a few shock oils And a set of springs. (Yeah racing has some great shock sets that come with 5 rates of springs) It's generally said that stiffer is better, as that lets you intentionally control wheel motion.
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Old 01-29-2020, 05:53 AM
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What is your budget?? If you want a good handling car you are better off just getting a different car. A friend of mine and me were in a similar situation. We both had HPI plastic cars. (Sprint2 and Sport3). We had each spent over $100 in upgrades and they still both handled like crap. We ended up buying used xrays. It was night and day difference and we spend less on the used XRAYs than we did on the plastic kits. If you don't want to go the used route, you could get one of the clones like a Sakura or a Spec-R.
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Old 01-29-2020, 06:31 AM
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Try as you may, and spend as much money as you like, but there is nothing that can be done to improve a Tamiya TT-02 chassis so that it can compete with a top line sedan today. If you wat to go fast on a budget, then buy the Xpress Execute XQ1S sport sedan and have fun. Other possible econo cars would be something from 3Racing, Spec-R, or as already mentioned a used top-line chassis like a TC6.2, Xray T4, Yokomo BD9 or similar.

As for the drif car, why bother making it stiff when all you do is slide sideways slowly around a track or in a parking lot. 5 minutes of doing that is enough to bore me to tears.
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Old 01-29-2020, 06:57 AM
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There's a lot to be said about making changes to a chassis that you'll be able to really see the difference on. Also, being cheap enough that you can ~do the things~ to it.

On pavement one of the fast guys in chicago? He leaves the awesomatix at home, brings out the TC4.
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Old 01-29-2020, 07:23 AM
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The tub chassis is really not the performance problem of the TT-02
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Old 01-29-2020, 07:44 AM
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Originally Posted by wtcc View Post
The tub chassis is really not the performance problem of the TT-02
It might be fun to see what happens to your lap time, black tub versus blue tub.
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Old 01-29-2020, 12:36 PM
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Originally Posted by ChaoticNeutral View Post
Thanks for the TT02 reference!

Currently, I have a TT-02 and a Yokomo YD2S I would be interested in making more competitive in TC and Drift respectively. So the goal would be to increase the polar moment of area of the chasis cross-section by adding another deck if I want to increase chasis performance? Is decreasing bending in the plane perpendicular to the chasis generally desirable/is decreasing chasis twist desirable for TC/drift? Also wondering if there's any way to "virtually" increase the Young's Modulus of the chasis to reduce bending.

I guess the question would be more what properties of a carbon fiber chasis are most important for racing and how one might emulate some part of them for relatively cheap?
A TT-02 chassis has less flex than most racing carbon chassis, so flex properties are not the issue here. As alluded to my others, the limitation on a TT-01 is not the chassis material, it is other aspects of the design such as weight, weight distribution, suspension geometry etc etc etc

When you look at a budget car that copies the geometry of full race cars (such as the Xpress XQ1S), you tend to find that it is not the chassis flex that is the issue, but the softer or less durable materials used in other parts of the car.
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