I think I want to build an RC car

April 5, 2007 on 12:07 am | In Needs more info |

I want to build a radio controlled car, or rather a truck, for an interesting robotics experiment. Self contained digital video recorders and wireless video cameras have progressed to the point that individually, their use on RC cars is relatively common as evidenced by a robust collection of bumper-view, hood-view, and zip-tied-to-the-roof view videos of RC cars tooling around in houses, parking lots, race tracks, dirt tracks, and populated streets complete with real vehicle traffic.

The questions this presents:

  • What kind of RC car to use - street, stadium, off-road, etc.
  • How to balance clearance, particularily if the camera will be used off-road, to stability which is enhanced by lower ride.
  • What kind of wireless camera (with which to drive when out of line of sight), night vision or plain
  • How to mount the wireless camera - fixed position bumper (infront of the steering wheels), fixed position farther back (so the wheels and the entire front end of the car can be visualized), or something actuated with the steering so that the camera leads into turns.
  • Under the assumption that current wireless video cameras do not provide a noise free video signal, there will be benefits to using a separate self contained video camera. What kind of video camera to use? Budget helmet cam ziptied or otherwise fastned to the car? There are pictures in google image search showing a CVS single use video camera ziptied into an RC car. The CVS camera has the benefit of being cheap, easy to dismantle (and rehoused in another enclosure), and has fixed memory and full motion frame rates. Helmet cams sometimes have slower frame rates but can be more durable, though there are some designs that will lose contact with the memory card under heavy vibration.
  • Battery life. Do I slave the video cameras to the car’s power (and add the weight of a transformer for mismatched voltage and amperage requirements) or keep everything electrically clean and pile on different collections of different size batteries.

11 Comments »

RSS feed for comments on this post. TrackBack URI

  1. On type of car:

    Most hobbyists asked have suggested either a particular model in the monster truck class or the monster truck class - big chassis with lots of suspension travel and two shock absorber / suspension rod mounts per wheel, dual motors to push a car loaded with cameras, and big wheel bases with suspensions able to handle the uneven terrain of off road areas that might be more interesting to explore with a remote piloted vehicle.

    This resulted in several suggestions.

    The Tamiya TXT-1, which I discounted for being way overkill, too expensive, and by design limited to such a slow speed (5mph) that it would preclude anything other than rock climbing.

    The Traxxas E-Maxx, Traxxas’ electric monster truck offering. This was the first contender until I read about the HPI E-Savage. While the two are relatively similar, the HPI adds two features right from the RTR package - an aluminum component in the chassis infrastructure and battery casings that project downward in a V pattern out under the body instead of the E-Maxx’s horizontal underbody tray. Since I will want endurance, I may want to expand the battery capacity with extra parallel circuit battery packs and that will probably be easier with the E-Savage’s under-chassis battery mount without crowding the motors or the body, provided that I leave clearance for the wheels (or extend the wheel base).

    These two offerings also have more conservative suspensions compared to the extreme offerings like the HPI Wheely King which if loaded down with av hardware would become very top heavy given its exceptionally high ride.

    Comment by suboptimal — April 5, 2007 #

  2. A coworker lent me an Oregon Scientific ATC2K waterproof self contained helmet cam. These differ from other helmet cams that are on the market in that this device does not require an external recording device - it writes .avi files directly to SD Media in the camera.

    While this camera doesn’t have very good reviews, mostly from extreme sports enthusiasts (people who actually do things that need a helmet and might look compelling from that angle) who note that the camera imaging system and the storage bay for the SD Media can’t handle severe vibration like from mountain bike handlebars, experiments with the camera wedged under my car’s headrest show tolerable performance.

    Next step is to see if the camera can image in the dark if in proximity to the infrared illuminators that are on the wireless camera I ordered off eBay.

    Comment by suboptimal — April 6, 2007 #

  3. So the ATC2K camera can see the IR emitter cone but the cone is very narrow. When mounted on the car this will have to be a very tight collimation, especially if I have the cameras rigged for panning. Tilt is out of question.

    Comment by suboptimal — April 8, 2007 #

  4. I think the ATC2K is out for this project. The Neuros MPEG4 recorder is probably less weight than the ATC2K, is certainly a slimmer profile, and can record 30fps. Since the video camera has simultaneous wired ntsc out as well as wireless video, I can use the Neuros to record what the camera sees without the degredation of a wireless encoded video signal. The hard part is it’s 0.5vdc/1.4A, so that will require some power conversion hardware.

    Comment by suboptimal — April 17, 2007 #

  5. Now I’m considering a different approach. A buggy might be the right idea and of less technical complexity than a monster truck, particularily in suspension and shocks.

    I think I want the Tamiya Dark Impact 1/10th scale 4wd electric buggy kit. As a kit and not an rtr package, it lacks several items, namely a transmitter, receiver, electronic speed control, and batteries. It has everything else from the motor out to the tires.

    Comment by suboptimal — April 17, 2007 #

  6. E-Savage Monster Truck RTR first, or Tamiya Dark Impact Kit first?

    Lets see.

    I eventually want a 2.4ghz radio system for both. The Tamiya is cheaper, but doesn’t come with a radio so I would have to buy a radio for it. The E-Savage comes with a radio, but it’s a 27mhz AM radio. E-Savage first then the Tamiya would mean I’d at least already have a 27mhz AM radio in the collection to drive the Tamiya, but I’d have to get a 27mhz receiver for it. Best would be to get either one and a Spektrum DX3.0 at the onset, then another Spektrum receiver for the second car whenever its obtained.

    The E-Savage comes with batteries and a less than ideal charger out of the box. The Tamiya comes with no batteries. It also has a brushed motor. I think I’d like a brushless system for the Tamiya (assuming they can take one without the application of a dremel) so in the interim the stock batteries from the E-Savage could be used, particularily if I upgrade to lipo batteries.

    Should also pick out the batteries and charger I’ll want.

    Comment by suboptimal — April 17, 2007 #

  7. The plan so far:

    - Start with an HPI E-Savage 1/10th scale 4wd electric monster truck RTR package and a Spektrum DX3.0 2.4ghz radio package. This gets me a 3channel controller immediately as well as an extra servo.

    - When Castle Creations releases the Mamba Monster Max, if it fits the E-Savage without wild modifications from a dremel, get one of those sets plus a ubec, a pair of lipo batteries and a decent lipo balancer/charger. This will establish a long endurance run time for the E-Savage as well as surplus out the E-Savage stock battery packs, charger, and ESC. At this point the stock battery packs can be doubled up on the E-Savage as a power supply for the camera, if I have something to transform the voltage.

    Then once I’m settled with the long endurance (and fast!) brushless E-Savage:
    - Get a Tamiya Dark Impact 1/10th scale 4wd buggy kit, possibly along with a Spektrum receiver. The kit has everything from the motors on out to the wheels so it’ll need a radio, receiver, esc, and servo. I’ll have the stock ESC, servo and batteries from the E-Savage to complete it. I can use the E-Savage radio and receiver or the Spektrum DX3.0 if I get the Tamiya a Spektrum receiver.

    Comment by suboptimal — April 18, 2007 #

  8. So, change of plans, slightly.

    The Tamiya DF-03 chassis that is the basis of the Dark Impact has a couple limitations. There have been complaints about the tight fit of the bathtub chassis space for servo, ESC, and receiver, none of which come with the kit, such that you have to be careful what you buy for fear that it might not all fit. Separately, the motor is mounted transverse in a socket in the chassis, without space for a heat sink and possibly in an arrangement that may not be able to accomodate motors that are the same size but have different wiring configurations or that are longer.

    And thus: The Kyosho Lazer ZX-5. The Kyosho Lazer ZX-5 is a newer higher end kit designed for racing. The kit includes three different differential gear designs and threaded aluminum shocks. It also has a larger bathtub chassis design with a logitudinally mounted motor. These features make it a much more flexible design.

    Comment by suboptimal — April 22, 2007 #

  9. Other alternatives have surfaced.

    The Tamiya DF-02 chassis has a larger bathtub chassis and a longitudinal engine mount.

    Also an option, the Team Academy / Model Rectifier Corp. SB Pro Buggy Kit, a very economical 4wd buggy that has some high end racing features.

    Comment by suboptimal — April 29, 2007 #

  10. My collection has started.

    I’ve received a Tamiya DF-02 chassis based Gravel Hound buggy kit. This kit has everything from the ESC and motor on out, so to get operating I need a battery, battery charger, servo, radio, and receiver.

    Now to find out what my local hobby shop carries.

    Comment by suboptimal — December 29, 2007 #

  11. The Tamiya DF-02 Gravel Hound chassis is built. The body is in the process of getting a paint job, but the chassis is all assembled, though it’s using a borrowed battery pack.

    After I had the chassis assembled out to the suspension arms, I finally hit the point where it was time to buy upgrades. Since the DF-02 only comes with bearings for a portion of the chassis, with plastic bushings provided for the drive train components past the front and rear differentials, I went to my local hobby shop and picked up a total of 8 bearings. While I was there I also splurged on a radio - a Spektrum DX6 Park Flyer.

    Since I have no interest in ever trying to fly a model rc vehicle, I don’t need the full range of the more expensive aircraft controllers, but my robotics interests necessitate more than 3 control channels and a stick controller is a good idea.

    The bundled AR6000 receiver is wired into the chassis at the moment but there’s a danger. The AR6000 has a failsafe position only on throttle and all other control interfaces go to a maintain last command signal during signal loss. Since the DX6’s throttle is a position-hold stick, it’s better to use the right hand stick (Elevator) for throttle. Since during signal loss the receiver would maintain last command, that means that on signal loss my car would keep throttle at whatever I was doing at the time that signal dropped.

    So, since then I’ve also gotten two BR6000 bot receivers which have firmware that provides a failsafe position on all channels. That’ll let me put a failsafe signal on what is actually plugged into my ESC on my bots.

    Comment by suboptimal — January 28, 2008 #

Leave a comment

XHTML: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>

Entries and comments feeds. Valid XHTML and CSS. ^Top^
22 queries. 0.354 seconds.
Powered by WordPress with jd-nebula theme design by John Doe.