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Old 01-27-2015, 06:26 AM   #1
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Default Need 1:10 Red Cat Help (Oval/Road/Drag)

I am a part of a high school engineering program that is currently working on a 1:10 scale red cat drift/oval car I believe. We are racing in an oval, road course, and drag. We are fairly new to these cars and would like some advice. We've heard that low light and left is good for the oval, and of course lighter is faster and more efficient but still looking for better options. We're currently running carbon fiber chassis, shock towers, and center stiffner with adjustable shocks and plastic everything else because it's usually 50% lighter than the aluminum upgrade kits. We have also locked our rear diff with jb weld and are only running rear wheel drive so the motor and battery don't have to turn two diffs to maximize efficiency. Advice on any parts, set-ups, or anything will help. We greatly appreciate this and are willing to share any knowledge we have that includes locked diffs, weights, etc. thanks!
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Old 01-27-2015, 11:54 AM   #2
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Looks like you succeeded in turning a square peg into a round hole. A 4wd car has essentially been reverse engineered into an overly heavy/ overly complicated 1/12 scale pan car.

Keep it as a 4wd to maintain stability. Focus on your physics fundamentals. Squared power (power output, multiplied by an exponent of 2) equates to double velocity - if and only if weight and drag are maintained.

Easiest way to square your power is to get a 4 cell Lipo battery, as you are likely using a 6 cell Nimh battery.

Reducing weight will not make your car faster, but simply allow it to achieve maximum velocity sooner - which my be practically impossible if you butchered a 4wd drivetrain into a locked rwd system for use on a track.

Good luck on your project. And remember, you aren't trying to re-invent the wheel here. Practically apply those proven physics fundamentals and work towards minimizing human error (practice driving).
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Old 01-27-2015, 12:20 PM   #3
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Sorry for the mathematical error. You would have to go to a 7 cell Lipo in order to theoretically double your speed.
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Old 01-28-2015, 11:29 AM   #4
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I appreciate your help. We locked our front diff as well and converted it back to all wheel drive for stability. We can only use NiMh or NiCd batteries with a maximum voltage of 8.4 volts and a 15 turn motor. We have lightweight motor mounts on the way with carbon fiber shock towers. We also have new wheels and tires. Were looking for carbon fiber axles and driveshafts if they even exist to minimize rotating weight. We also are still searching for "loop holes" within the rules. What are the best tires? Is there anyway to soften the rubber compound? Any tips would be very appreciated. We test everyday for a 3 hours and the locked diffs seem to help since all four tires turn simultaneously with equal power. All other cars we run against are basically stock and we can run circles around them. Were on the right track but would like to further our knowledge of parts, set-ups, etc. thank you all so much.
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Old 01-29-2015, 11:32 AM   #5
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Old 01-29-2015, 03:11 PM   #6
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For drag racing the locked diffs is a good way for launch, but for oval and road racing you will have handling issues. A rear diff and locked spool in the front is the way to go for road course. In oval, I would disconnect the front drive-train to lessen drag. As for tires, we need to know what surface you are running before we can suggest anything, that goes for traction compound as well.
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Old 01-31-2015, 01:16 PM   #7
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If you are using nimh batteries and a 15 turn brushed motor, then you'll be best suited in researching what racers did 15 years ago. Lathe the commutator regularly, charge at 10 amps. Discharge at 30 amps.

Conditioning and maximizing your powerplant will make the car go faster. Carbon gear shafts and lightening the vehicle will only benefit handling, not velocity. Besides, with the weight of a Nimh battery, saving a few grams will be meaningless.

As the previous poster said, we would need more info before giving you detailed setup info. What is your thesis? What is the objective you are trying to accomplish in this assignment?
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Old 02-05-2015, 12:31 PM   #8
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The surfaces can differ. One year we were outside on asphalt and the next we we were racing on a polished concrete surface. We will be outdoors. We ordered HPI Racing D compound x-pattern tires (RC-Planet recommended) and they seem way more soft and grippy than our original tires.

Is the stock differential a locked spool? We currently are running a locked differential in the rear and the stock differential in the front for oval. The rear wheel drive idea has been kicked to the curb because we still spun on launch and spun coming off the corners. We lock both differentials for the drag. And have no traction issues.

We are running a carbon fiber chassis, shock towers, and center stiffener as well as aluminum adjustable shocks. We kept the rest of the car in plastic components due to the aluminum upgrade kit components usually being twice as heavy. We are still looking for parts. Carbon Fiber drive shafts, axles, motor mounts, differential covers, etc.

Now you guys know our racing surface, as well as drag, road course, and oval racing. The drag race is 30 - 100 ft, and the oval we are racing on is 60-100 ft long and 50-65 ft wide. Final dimensions are given in the event guide that isn't out yet. Help is still needed with set-ups, part recommendation, gear ratio's, shock types, motor recommendations, etc. Hope the extra info can assist you guys. Thanks again.
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Old 02-05-2015, 12:37 PM   #9
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If you are using nimh batteries and a 15 turn brushed motor, then you'll be best suited in researching what racers did 15 years ago. Lathe the commutator regularly, charge at 10 amps. Discharge at 30 amps.

Conditioning and maximizing your powerplant will make the car go faster. Carbon gear shafts and lightening the vehicle will only benefit handling, not velocity. Besides, with the weight of a Nimh battery, saving a few grams will be meaningless.

As the previous poster said, we would need more info before giving you detailed setup info. What is your thesis? What is the objective you are trying to accomplish in this assignment?
We are trying to make our rc car the fastest, most consistent car when we race it against many others among a national event. We can have separate cars for separate events. Were new and still learning but have came to many conclusions just from testing. What do you mean by Lathe the commutator regularly? We thought that charging the battery slower maximized battery life. And how do we get our car to discharge at 30 amps? I know the rules have us using out dated technology but it is what it is and were trying to get everything we can to make our car faster and further our knowledge. Thanks agian.
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Old 02-05-2015, 01:50 PM   #10
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A motor lathe will keep your 15 turn brushed motor in optimal condition. Soft brushes (high silver content) will also have your motor running at peak performance. Commutator drops will increase conductivity between the brushes and commutator. Again, if you Google up "how to tune a stock motor", you'll find a lot of this info. Or just visit a rc hobby shop and get the history lesson from the horses mouth.

Same with NimH cells. If you charge and discharge at a high rate, you will condition the battery to hold a higher level of voltage, and be comfortable with allowing a higher rate of discharge. If a 1157 light bulb (25 cents) draws aprox 2 amps, then wiring 15 in series will theoretically draw 30 amps.

At this point, i have to warn you that drawing 30 amps from a battery is not safe. We used to do it all the time "back in the day" with totally exposed cells that we soldered up ourselves. The reality is that 1 amp is enough to kill you. Also, if you are using run of the mill stick packs with a tamiya molex connector, 30 amps willl make that plastic end melt and catch fire. Ask the hobby shop about zero-loss connectors.

My advice would be to seek direct info from a hobby shop. Or take the car to a track and let a racer try it out. After a few laps, they can probably give you some pointers on how to drive it better with what you have available. Rather than try to make a better car, it may be more advantageous to learn how to drive better with what is on hand. On a race track, slow is fast.
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Old 02-06-2015, 12:12 PM   #11
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Thank you for all your advice but we're still unclear on what you mean by lathing the motor. How do we go upon doing that and keep our motor in optimum condition? Our motor is a sealed canister.
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Old 02-07-2015, 01:12 PM   #12
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I'm not sure what kind of motor you have, which is a 15 turn with a sealed endbell. I've heard of Dynamite basher 15 turn motors, but without verification on what you have, this is pure speculation. Here lies the problem with asking for help on the Internet from total strangers. You seek advice and tips, but cannot verify or clarify anything. Any input given to you can simply be disregarded or compromised by throwing a curveball back at us on these forums. We did not initially know you had a Nimh requirement. We did not know you had an old 15 turn sealed endbell brushed motor. We do not know the rule set you have to follow. We are curious as to how you are able to easily afford and procure carbon fibre components for such a shitty vehicle, yet lack the basic knowledge of how an rc car works (hacking/reverse engineering a 4wd into a rwd with locked diff, and then converting it back to "normal"). We don't even know if you are using a peak detection charger capable of 10 amps, or if you are using an old charger that has an analog egg timer on it (yes, many of us in this hobby started with the egg timer charger).

Please find an onroad rc club in your area, or seek the advice of a hobby shop so that you can get hands-on help and verification. At this point, nothing else we can tell you is of any measurable help or validity. You might as well start searching for unicorns. Without tangible information and parameters, we can only do so much to help or guide you over the Internet.
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Old 02-09-2015, 11:51 AM   #13
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I'm not sure what kind of motor you have, which is a 15 turn with a sealed endbell. I've heard of Dynamite basher 15 turn motors, but without verification on what you have, this is pure speculation. Here lies the problem with asking for help on the Internet from total strangers. You seek advice and tips, but cannot verify or clarify anything. Any input given to you can simply be disregarded or compromised by throwing a curveball back at us on these forums. We did not initially know you had a Nimh requirement. We did not know you had an old 15 turn sealed endbell brushed motor. We do not know the rule set you have to follow. We are curious as to how you are able to easily afford and procure carbon fibre components for such a shitty vehicle, yet lack the basic knowledge of how an rc car works (hacking/reverse engineering a 4wd into a rwd with locked diff, and then converting it back to "normal"). We don't even know if you are using a peak detection charger capable of 10 amps, or if you are using an old charger that has an analog egg timer on it (yes, many of us in this hobby started with the egg timer charger).

Please find an onroad rc club in your area, or seek the advice of a hobby shop so that you can get hands-on help and verification. At this point, nothing else we can tell you is of any measurable help or validity. You might as well start searching for unicorns. Without tangible information and parameters, we can only do so much to help or guide you over the Internet.

We are a high school team. Through fundraising and sponsors money is no object but we have rules and regulations to follow. I know it's difficult to explain online but we dont have any hobby shops locally. That's why we are online. If we had a hobby shop I wouldn't have wasted my time talking to you.

Locally we run actual dirt racecars. Not these scaled down p.o.s.'s that you dump $20 into at a time. I have an idea of the physics behind how one runs and how to race, but I dont know much about parts, set ups, or modifications that are available. I am a successful dirt track racer, but I'm taking steps to help my high school class to victory. Once our event is over, Ill never touch an rc car again. I have better things to spend time and money on. I thought I was coming to the experts by posting a forum, but I've soon realized that I would have been better on my own.

It's amusing that you can critic what we've already done and write paragraphs about what we have already figured out. The reality of it is your worthless when it comes to advice. You spend more time critiquing new comers who are seeking help than actually helping them. Dont worry about wasting your time. Part of racing is trial and error testing. A locked 4wd diff is best for our drag, the rwd only is best for oval, and one locked rear with an unlocked front has proved best for launches and road courses. We have re-evented the wheel and it's working flawlessly. Why dont you just stay to your upgrades and not worry about doing something others aren't. I don't know you but from your shitty advice I take it you haven't won much. This is a joke. Why dont you take your profile picture you found off google down and face reality?
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Old 02-09-2015, 11:53 AM   #14
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For drag racing the locked diffs is a good way for launch, but for oval and road racing you will have handling issues. A rear diff and locked spool in the front is the way to go for road course. In oval, I would disconnect the front drive-train to lessen drag. As for tires, we need to know what surface you are running before we can suggest anything, that goes for traction compound as well.
Were running on polished concrete or asphalt. We have a locked rear diff and stock front diff. Does the stock differential have a locked spool? Thanks for you practical advice.

-Matt
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Old 02-09-2015, 12:13 PM   #15
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You're an experienced dirt track racer, another curveball. Thanks

Now we got that out of the way, are you utilizing setup sheets to document what your current times are with each setup?

In an rc drag race, have you considered running a locked front only, with 2' toe out and locked front shocks?

When we calculate the scale speed that these vehicles operate at, the physics of normal vehicles is essentially thrown out the window.

PS: i'll tell KT So that you said hello
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