Cheap RC car upgrade - Page 1
Forum section: electronics / beginners

author: TCPMeta
author_rank: Newbie
timestamp: November 13, 2014, 06:55:33 pm
content: My son has a cheap RC car that weighs about 3lbs and uses four AA batteries. The part that shocks me is the motor.I have seen this same type of motor in other devices its just utter crap. Also the car uses the same type of motor in the front end for the steering. It has two 22ohm resistors. The rear motor had two choke coils to lower the voltage from six volts to four volts. I removed the resistors and choke coils and the car was much better. Before it moved at the speed of snail and had a turn radius of a school bus. However there is a new problem but with the battery life. With fresh batteries it lasts about ten minutes since it needs to run the rear motor at WOT to move. As a project for my son and myself we are rebuilding the whole car but with minimum parts or with what I already have in my inventory. The only part that has stopped me at the moment is figuring out how to add more juice with out burning up the RC receiver. I was lucky enough to find the data sheet for it and it is rated to withstand 12volts but that is just the receiver chip. Is there a way I can use a voltage regulator to power the receiver and use a higher voltage for the steering and rear wheels with say a MOSFET? Or should I just completely reverse engineer the board? It has three c8050 five c8550 and one c8115 transistors. From what I can see most of the board can already withstand the voltage increase but the C8115 transistor can only withstand 5volts on the emitter.

author: cybertronicify
author_rank: Regular Contributor
timestamp: November 13, 2014, 07:09:22 pm
content: You can get some cheap brushless motors and ESC's on ebay. Since the ESC is controlled by PWM you can hook the receiver to the ESC directly. But check the voltages and make sure they aren't borderline MAX, since those ESC's prob uses fake parts. And the ESC can be powered separately with another battery such as a LiPo pack.

author: katzohki
author_rank: Frequent Contributor
timestamp: November 13, 2014, 07:09:56 pm
content: More mAh is what you need, not more voltage. Try a rechargeable RC battery pack that has about the same voltage as the AAs, but with more capacity. That way you can run longer. Or roll your own battery setup.

author: cybertronicify
author_rank: Regular Contributor
timestamp: November 13, 2014, 07:19:31 pm
content: Oh oops the picture didnt load. You might want to try out a LiPo and a buck converter. That will get you a lot of juice and i cant imagine that RC car drawing more than 5 amps.$0.88 USDhttp://www.ebay.com/itm/New-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Supply-1-23V-30V-CP282-/251698048368?pt=LH_DefaultDomain_2&hash=item3a9a5f6d70

author: RedOctobyr
author_rank: Contributor
timestamp: November 14, 2014, 02:15:10 am
content: I'm not an electronics person, just an RC hobbyist. I was going to suggest a simple BEC (Battery Eliminator Circuit; typically a switching, not linear, voltage regulator) for powering the receiver. It would take the input voltage down to 5V, 6V, etc. Something like this:eBay auction: #http://www.ebay.com/itm/HOBBYWING-RC-UBEC-5V-6V-3A-Max-5A-Lowest-RF-Noise-BEC-/221588340456?pt=Radio_Control_Parts_Accessories&hash=item3397b1bee8But that adjustable one you posted is even cooler! And it's great to know about, for an unrelated little project I have in mind, thank you! Cheap, wide input range, and adjustable output voltage, perfectIf it's draining an AA battery in about 10 minutes, the current draw could be somewhat high? An NiMH AA is often around 2000mAh. If we assumed you really drained the whole battery in 10 minutes, that would be 60min/10min = 6C draw. 6C * 2Ah capacity = 12 amp average draw (I've never tried to pull a lot from an AA, I'm skeptical they'd be able to put out 12A)? But even if it's only half that, that's still 6A.If using some sort of converter to power the motor, you might need to consider the amperage rating of the converter. Or check the draw of the car.And if you really want to make a difference, going to brushless and maybe a 2S LiPo would do it!

author: Riotpack
author_rank: Regular Contributor
timestamp: November 14, 2014, 03:12:54 am
content: You can get some good motors in that size, like the Tamiya Japan Cup 2014 series Hyper- Dash LoLhttp://www.tamiyausa.com/items/radio-control-kits-30/racing-motors-43050/jr-hyper-dash-3-motor-95025Or the 25000RPM Plasma Dashhttp://www.tamiyausa.com/items/radio-control-kits-30/racing-motors-43050/jr-plasma-dash-motor-15186These should work with 1 LIPO but will be overdrivenThere must be brushless versions of this size of motor too?

author: TCPMeta
author_rank: Newbie
timestamp: November 14, 2014, 06:27:59 am
content: As I said im rebuilding the whole car with what I already have. After all im giving this to a 8 year old that will probably break it in a week. I'm just building it for kicks.I got everything planned out except the receiver. I'm going to use two systema high torc brushless motors I pulled out of a couple of AEG style airsoft rifles for the rear and the steering I was going to reuse the stock so called wannabe servo that came with the car but build a custom steering rack for it. For the power I was planning to use a 11v 1800mAh nicad.I can easily build a BEC. It's just a 7805 regulator and a couple of 1uF caps. Or even better a LM2940 since it only needs 5.5volt to operate VS the 7805 that needs around 7volts to operate.I got a idea and i'll report back on it. It's a simple circuit I use a lot with airsoft rifles. Uses a IRL1404z MOSFET, one 20K ohm and one 100 ohm resistors. Put the 20K on the Gate and Source pins, Gate goes to a 100ohm Then to the receiver, I will also have a diode to protect it. Drain goes to the negative side of the motor and Source to the negative side of the battery Meanwhile i'll have a regulator to run the receiver and "servo".

author: ijchan223
author_rank: Contributor
timestamp: November 14, 2014, 10:23:24 am
content: Personally i would go with a Lipo battery, and some regulators since it will be trashed in a few weeks anyways.

author: Monittosan
author_rank: Regular Contributor
timestamp: November 14, 2014, 01:17:29 pm
content: I can't Tell if this is cheap RC or Just crap RC???Was the car from an actual RC company like tamiya or HPI ? or is it simply a toy you want to modify for kicks?That Plasma dash motor looks the goods with a decent battery and correct gearing!

author: TCPMeta
author_rank: Newbie
timestamp: November 15, 2014, 03:27:50 pm
content: A junky Jada Toys RC 1:16 Charger police car.Kinda wish I didn't start on this so called project. It has taken away time to work on other meaningful projects I got going but it gives time to spend with my son. I just hope he doesn't bring home more crap for me to fix.

author: Monittosan
author_rank: Regular Contributor
timestamp: November 16, 2014, 03:11:26 am
content: Nothing wrong with that, but an RC car kit mite be time better spent.Either way a hot motor and decent rechargeable battery will really make that Police car move.

author: BradC
author_rank: Super Contributor
timestamp: November 16, 2014, 04:32:22 am
content: Quote from: Monittosan on November 16, 2014, 03:11:26 amFor about 4 seconds until the new motor (which is about 100x more powereful than the old motor) strips all the gears in the drive train....Ask anyone who works behind the desk in a hobby store what happens when they sell a new brushless and ESC to someone who wants to upgrade their old Tamiya from the 80's.. Goes something like this :" And I picked up this great new motor and ESC from E-bay. Thought it'd be a great upgrade.""Blew the diff?""Blew the diff. Brazed the diff closed.""Stripped the axle splines?""Stripped the axle splines."

author: Monittosan
author_rank: Regular Contributor
timestamp: November 16, 2014, 08:16:01 am
content: yesss......but i doubt a brushed motor in that frame size is capable lol

author: Riotpack
author_rank: Regular Contributor
timestamp: November 16, 2014, 10:51:21 pm
content: Quote from: BradC on November 16, 2014, 04:32:22 amYip seen it many times too - You will find fragile plastic gears in the cheap RC cars. If you lube it well and use a higher RPM motor with not too much of a torque increase you will get a bit of play time from it. I have remade drive shafts out of brass when the plastic ones broke on a cheap RC car.

author: TCPMeta
author_rank: Newbie
timestamp: November 17, 2014, 08:21:23 am
content: I was cleaning up a box of junk and came across a 8volt nicad battery. I charged it and tried it out on the RC car and it works fine. So I don't need to worry anymore on adding in some circuits or at most a voltage regulator for the steering. I'll finish the car tomorrow and call it done.

author: BradC
author_rank: Super Contributor
timestamp: November 17, 2014, 10:31:05 am
content: Quote from: Riotpack on November 16, 2014, 10:51:21 pmThese were brass gears and steel driveshafts. The torque difference between a new BDLC motor and the old RS380 or 540 is over an order of magnitude.

author: EvilGeniusSkis
author_rank: Regular Contributor
timestamp: November 22, 2014, 07:49:58 pm
content: I'd also remove some mass from the car.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 22, 2014, 09:09:28 pm
content: Quote from: TCPMeta on November 15, 2014, 03:27:50 pmditto! now you know the precise answer. you have no idea how many that crap motors i've collected each time i bought rc car for my kids and got damaged. i can upgrade all the fancy stuffs if i want to, but... ditto! next move.... i've bought FlySky FS-TH9X et al... now thats worth an hack! so they said...