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Old 06-08-2009, 11:50 AM   #1
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Default Why the non-independent rear suspension on 2-WD RC Cars

1. Besides tradition or force of habit is their sound scientific/physics reason why 2wd racer chassis go with the mono shock/pod style rear non independent suspension?
Full size 2WD race cars do not(at least most do not). Is it something to do with the efficiency of the direct drive motor mount ?

2. A Related question Formula 1 is by far the fastest road course chassis style and its close cousin the Indy car chassis the oval, yet the F1 open wheel style 2WD chassis seems slower when talking about 1/10 scale.

Theoretically would the fastest 1/10 scale setup be a slightly smaller version of the 1/8 nitro cars, namely 4 WD with wedge shaped body?

3. Is there some other factor which ROAR rules outlaw but if used on 1/10 scale would make them much faster some kind of braking system not dependent on the motor. Some kind of electronic traction control device or gyro. Wider track relative to wheel base? Over size tires? Extreme weight reduction?

In otherwords what would a no limits no holds bared 1/10 scale on road racer look like?
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Old 06-08-2009, 12:43 PM   #2
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Based on past experience in the late 80's and early 90's when converted RC-10's were popular for asphalt and carpet, I think it boils down to CG and pure acceleration.

The direct drive is more efficient and spools up faster, while given the same weight it likely would not handle as well, the reduced CG and mass allow it to corner better and launch back out faster.

For example, the recent ROAR Carpet Onroad Nationals, touring Superstock 7.4 volt touring with the pull and handling of 4wd had A main lap times around 10.2-10.3 The World GT super stock 4.8 volt (same motor less voltage) ran 10.1-10.3. Give the World GT the extra voltage and the would be ballistic.
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Old 06-08-2009, 01:19 PM   #3
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What i remember is that the lemans cars were faster then f1 but they got fazed out cause of formula 1 bosses called the shots back then. That is what i remember anyway... i could be wrong :-)

edit: this has nothing to do with rc but wanted to mention it anyway :-)
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Old 06-08-2009, 02:42 PM   #4
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Here's what I came up with. With 6 cells it's difficult to drive. It works a lot better with 4 cells and a 27T stock. Don
Attached Thumbnails
Why the non-independent rear suspension on 2-WD RC Cars-p1010002.jpg   Why the non-independent rear suspension on 2-WD RC Cars-p1010003.jpg   Why the non-independent rear suspension on 2-WD RC Cars-p1010004.jpg   Why the non-independent rear suspension on 2-WD RC Cars-p1010001.jpg  
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Old 06-08-2009, 03:10 PM   #5
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With the motor offset so far to the driver's side you want to focus on balancing the car. Being so heavy to one side had to have an adverse effect on handling.

Plus, are your body posts mounted to the rear hub?

I'm not trying to slam your car, it looks great and well constructed! Just trying to brainstorm some ideas to help your handling with 6-cells.

Any chance of getting a better pic of the motor mount/ball diff mount?
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Old 06-08-2009, 03:10 PM   #6
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Quote:
Originally Posted by DLS II View Post
Here's what I came up with. With 6 cells it's difficult to drive. It works a lot better with 4 cells and a 27T stock. Don
Back in the late 80s there was a small company that made a direct drive setup for the RC10, replacing the transmission with just one gear. However, it was just a replacement for the transmission, and the rest of the RC10 remained in place. The only bad aspect of the design was the height of the outdrives, which put the dogbones at quite steep angles. Nobody understood that stuff back then though.

Your design is intersting though.
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Old 06-08-2009, 03:22 PM   #7
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I'll try to work on some other pics. The "rear end" is 2 RC12 motor plates. The spur is mounted in a Traxxas TCP diff. You are right about the offset weight of the motor-it's a consequence of direct drive. Yes, the rear body mounts are attached to the rear uprights. I had to try it. I think I'm going to go to standard rear mounts. The ones attached to the rear uprights have a tendency to "lay over". It would probably help tp have some fresh sticky tires also. The ones I used are quite old. Don
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Old 06-08-2009, 03:53 PM   #8
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back in the late 80's when a lot of On-Road was going to 1/10th scale PAN CAR...we had a group of guys that took the RC10L or similar style front ends and put them on a chassis with the DOMINATOR (Dirt Oval Car) Chain Drive rear end with independant Suspension

These were run on both On-Road and Oval Tracks...and worked REALLY WELL at that time -- We ran NORRCA rules at the time, and NORRCA past a rule that outlawed these cars. (Because they weren't SOLID AXLE cars - they couldn't run in the Pan Car Class - and because they didn't have a TRUE gear box - they couldn't run in the "Gear Box" class.
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Old 06-08-2009, 03:58 PM   #9
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Here's some pics of the rear end. I must be missing something-the rear end steps out without much provocation. It doesn't fit any class. I'm tempted to turn it into an illegail TA.
Attached Thumbnails
Why the non-independent rear suspension on 2-WD RC Cars-p1010001.jpg   Why the non-independent rear suspension on 2-WD RC Cars-p1010002.jpg   Why the non-independent rear suspension on 2-WD RC Cars-p1010003.jpg   Why the non-independent rear suspension on 2-WD RC Cars-p1010004.jpg  
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Old 06-08-2009, 04:29 PM   #10
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If you look back to the beginning of rc, 1/8 racing, most of the people involved were ex slot racers. Basically, the cars looked like giant slot cars with nitro motors. Anyway, all the slots were straight axle cars. When 1/12 became popular, they were originally .049 nitro cars, based on the big cars. Full suspension 1/8 cars did not become popular until the 1980s.

There were was one car, which I can't remember the name of, which had full suspension, very trick. It didn't seem to go over, not sure if it was the price or how it worked or both.
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Old 06-08-2009, 06:21 PM   #11
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I like your idea on the rear setup. If you want the facts on how to make it work as it should contact Marty at www.mlpmotorsports.net he built some prototype cars like what you mentioned. They were super fast and very hooked up. They were a little pricey and he went to d-drive models this year which are fast and less complicated. I do know some people out there are begging him to produce the car again because it is so realistic. He's very knowledgable about these things since he designs and test's his own cars.
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Old 06-08-2009, 07:18 PM   #12
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Quote:
Originally Posted by SWTour View Post
back in the late 80's when a lot of On-Road was going to 1/10th scale PAN CAR...we had a group of guys that took the RC10L or similar style front ends and put them on a chassis with the DOMINATOR (Dirt Oval Car) Chain Drive rear end with independant Suspension

These were run on both On-Road and Oval Tracks...and worked REALLY WELL at that time -- We ran NORRCA rules at the time, and NORRCA past a rule that outlawed these cars. (Because they weren't SOLID AXLE cars - they couldn't run in the Pan Car Class - and because they didn't have a TRUE gear box - they couldn't run in the "Gear Box" class.
To this day I still covet my back-halved Dominator! It's cool to learn they were a national phenomenon, as I thought they were just an east coast thing.

Custom Works offered one-way hubs for the chain driven Dominator, and while intended for the front hubs, a certain super-wheel named Kenny Hammond had a back-halved Dominator with the oneway hubs out back. He didn't have any brakes, but the car was insanely fast through the corners. Unreal to watch him destroy the field. Took him two laps to wiggle the car to a halt after the race ended.
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Old 06-09-2009, 07:57 PM   #13
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Dynamic 1/8 car that i couldn't remember yesterday...this was an early 70's car...







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Old 06-09-2009, 10:27 PM   #14
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Quote:
Originally Posted by imjonah View Post
1. Besides tradition or force of habit is their sound scientific/physics reason why 2wd racer chassis go with the mono shock/pod style rear non independent suspension?
Full size 2WD race cars do not(at least most do not). Is it something to do with the efficiency of the direct drive motor mount ?
The largest reason pan cars today are still not independent rear suspension is probably the rules.

Quote:
Originally Posted by imjonah View Post
2. A Related question Formula 1 is by far the fastest road course chassis style and its close cousin the Indy car chassis the oval, yet the F1 open wheel style 2WD chassis seems slower when talking about 1/10 scale.

Theoretically would the fastest 1/10 scale setup be a slightly smaller version of the 1/8 nitro cars, namely 4 WD with wedge shaped body?
F1 in RC is typically slower because often they run a spec class where the motor is limited. Moving up from there into faster motors then you run into a down force issue. In full sized racing the wings on a F1 provide quite a lot of down force but in RC you have full sized air going over 1/10th scale wings so they are not as efficient as their full sized counterparts.

Theoretically a wedge body on a 4wd car would be quicker in the corners but the car suffers in the added weight and drag in the drive train which in some circumstances can nullify the advantage of 4wd.

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3. Is there some other factor which ROAR rules outlaw but if used on 1/10 scale would make them much faster some kind of braking system not dependent on the motor. Some kind of electronic traction control device or gyro. Wider track relative to wheel base? Over size tires? Extreme weight reduction?
ROAR rules do limit the amount of electronic aid that can be used. Many radios have an ABS system that simulates an ABS by pulsing the brakes, however there is no sensor on the car to detect wheel slip or lockup. As soon as you add sensors like that to the system it becomes illegal. Likewise gyros are illegal as well. ROAR rules also specify max/min sizes for wheelbase, wheel track, tire size, and weight.

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In otherwords what would a no limits no holds bared 1/10 scale on road racer look like?
In any form of racing RC or full sized there are rules and limits placed on what you can do. Using today's rules as a guild line a no limits no holds bared 1/10th scale on road racer would look much like they do now.
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Old 06-09-2009, 10:42 PM   #15
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Quote:
Originally Posted by imjonah View Post
2. A Related question Formula 1 is by far the fastest road course chassis style and its close cousin the Indy car chassis the oval, yet the F1 open wheel style 2WD chassis seems slower when talking about 1/10 scale.
Back in the early 90's the IMSA GTP (Nissan, Jaguar, Toyota) cars were lapping near as fast as Indy cars on some road courses. The turbocharged V8's (Cosworth, Ilmor Chevy/Mercedes and later Honda) were making substantially more power, but Open wheeled cars produce tons of drag. Put a closed cockpit and fenders on a F1 Car (let Brawn do it), and it will annihlate anything with open wheels.
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