experimental project

[krekeltronics]

Hi guys,

I'm coming back to R/C after more than 20 years. My last car was a Losi JRX Pro truck conversion. Lots has changed but a lot is the same! It's cool to see mid/rear motors and other neat advancements. My childhood R/C hobby led to a career as an electrical engineer and product developer. Now my career and a desire to introduce my kids to the hobby has brought me back! I can see I have a LOT to learn.

I'm going to be undertaking an R&D project to develop custom hardware and software for a vehicle that will aim to eventually be self-driving to a given location via GPS. Primary control would be via iPhone/Android. I know since I was a hobbyist, electronic hardware has broken into the mainstream, so I'm sure this could be done with Arduino and a bunch of off the shelf modules, but it's important for me to develop everything custom.

All the code will be published for free as open source via GitHub so others can contribute or use it for their own projects. If along the way we stumble upon something innovative, we will crowd fund a little production run so the hardware can be available for purchase.

So I have a bunch of questions before I can begin:
* because we need some space for hardware, especially prototypes that may span multiple boards hacked together, I probably need a truck body. Is the 22sct a good fit? The 22 buggy looks awesome but I'm betting there's no extra space under that body. SCT class didn't exist when I was last into this so I want to understand how it differs from stadium trucks like the old jrx-t. The SCT seems great since it goes out over the wheels (vs. 22T), so a lot of extra stuff could be crammed in. I think I want to stick with 2wd for simplicity. Any suggestions?

* we'd initially be testing this in yards, parking lots, and around our cul de sac. What tires would be best?

* is there a dead-simple list of specific things we'd need beyond the truck kit itself to build out a working example? Before we begin I want to have an off the shelf setup as a backup system and simply to try everything out. So for someone who doesn't care about competition and simply needs a good reliable system, what motor, servo, radio, ESC, batteries, and everything would be suitable? Budget isn't a huge issue but I need components that will last.

* do you guys think anyone would be into this if we did end up with a product/kit?

Cheers all! I'm excited to get started and I thank you for your time. I'm starting from scratch since so much has changed, I'l looking forward to your guidance (and any related ideas).

Patrick Krekelberg
Krekeltronics

[Coelacanth]

Sounds like a cool project, but just focusing on one of your questions brings up many more questions.

* we'd initially be testing this in yards, parking lots, and around our cul de sac. What tires would be best?

How off-road will this car be going? By "yards", do you mean grass and bumps & dirt? Obviously different tires are best suited to these conditions than pavement tires. How fast will this car be expected to go? Will it be slow and methodical and handle various terrain, or be faster and primarily limited to asphalt? That'll be a major determinant in what tires & wheels you'll want to consider. That would matter a lot more than what body you chose.

Pro-line Calibers are a good all-around choice for 2.2" tires, but for mostly pavement driving, one suggestion would be Pro-line Road Rage tires in 2.2" or 2.8" (depends on your wheel size).

As for the reliability of the electronics, I'll defer to the racers here, they'd be the best source of advice when it comes to durability under stressful conditions.

[Brocklee]

Hi guys,

I'm coming back to R/C after more than 20 years. My last car was a Losi JRX Pro truck conversion. Lots has changed but a lot is the same! It's cool to see mid/rear motors and other neat advancements. My childhood R/C hobby led to a career as an electrical engineer and product developer. Now my career and a desire to introduce my kids to the hobby has brought me back! I can see I have a LOT to learn.

I'm going to be undertaking an R&D project to develop custom hardware and software for a vehicle that will aim to eventually be self-driving to a given location via GPS. Primary control would be via iPhone/Android. I know since I was a hobbyist, electronic hardware has broken into the mainstream, so I'm sure this could be done with Arduino and a bunch of off the shelf modules, but it's important for me to develop everything custom.

All the code will be published for free as open source via GitHub so others can contribute or use it for their own projects. If along the way we stumble upon something innovative, we will crowd fund a little production run so the hardware can be available for purchase.

So I have a bunch of questions before I can begin:
* because we need some space for hardware, especially prototypes that may span multiple boards hacked together, I probably need a truck body. Is the 22sct a good fit? The 22 buggy looks awesome but I'm betting there's no extra space under that body. SCT class didn't exist when I was last into this so I want to understand how it differs from stadium trucks like the old jrx-t. The SCT seems great since it goes out over the wheels (vs. 22T), so a lot of extra stuff could be crammed in. I think I want to stick with 2wd for simplicity. Any suggestions?

* we'd initially be testing this in yards, parking lots, and around our cul de sac. What tires would be best?

* is there a dead-simple list of specific things we'd need beyond the truck kit itself to build out a working example? Before we begin I want to have an off the shelf setup as a backup system and simply to try everything out. So for someone who doesn't care about competition and simply needs a good reliable system, what motor, servo, radio, ESC, batteries, and everything would be suitable? Budget isn't a huge issue but I need components that will last.

* do you guys think anyone would be into this if we did end up with a product/kit?

Cheers all! I'm excited to get started and I thank you for your time. I'm starting from scratch since so much has changed, I'l looking forward to your guidance (and any related ideas).

Patrick Krekelberg
Krekeltronics

Let me start by saying that I don't have a short course truck, but I will say that if your project needs a lot of real estate on the chassis the 22sct might not be the best choice, the 22sct has a very narrow chassis. If you need something with more real estate look into the kyosho sc or scr, or possibly associated's sc10, but the current sc10 is based on the t4 chassis and associated just released the b5 so probably within the next year or so there will be an update to the sc10 I would guess. Also as for the battery be careful with the modern lipo technology as they are very different from the old nicd/nimh batteries. Lipo's do require a lipo specific charger/balancer and shouldn't drop below 3.1v per cell. If it does drop below 3.0v the pack is ruined and if the pack is charged above 4.2v (I think) the pack will likely catch fire. Anyways sounds like a ton of fun keep us updated!

[krekeltronics]

How off-road will this car be going? By "yards", do you mean grass and bumps & dirt? Obviously different tires are best suited to these conditions than pavement tires. How fast will this car be expected to go? Will it be slow and methodical and handle various terrain, or be faster and primarily limited to asphalt? That'll be a major determinant in what tires & wheels you'll want to consider. That would matter a lot more than what body you chose.

Pro-line Calibers are a good all-around choice for 2.2" tires, but for mostly pavement driving, one suggestion would be Pro-line Road Rage tires in 2.2" or 2.8" (depends on your wheel size).

That makes sense. Because we're just beginning I need to make some good guesses, and naturally a few of those guesses will need to be rethought later on. My guess initially is that the primary surfaces initially will be pavement and grass.

So maybe I could start out with the Calibers you recommend and go from there.

As for speed, I am aiming for fast-ish and primarily asphalt. And since you mention terrain and things we might want to build up a few of them - one for primarily asphalt/mild terrain and one for rougher locations (like a 22T if I can find one?). But not so fast on the trigger that it's impossible to test.

As for the reliability of the electronics, I'll defer to the racers here, they'd be the best source of advice when it comes to durability under stressful conditions.

Indeed!

Thanks for your thoughtful reply. I knew looking through this forum that there would be someone willing to weigh in

Patrick

[jwscab]

Hate say it but something like a Traxxas Slash might be just the ticket for you. plenty available, pretty tough, and most importantly, it has a huge slab-like chassis plate made of plastic just perfect for sticking electronic boards on for development.

http://traxxas.com/gallery/electric/5807slashvxl/Slash-VXL-5807-Chassis-Top-View

the military use such chassis' for bomb triggering RC vehicles from what I understand.

[krekeltronics]

Let me start by saying that I don't have a short course truck, but I will say that if your project needs a lot of real estate on the chassis the 22sct might not be the best choice, the 22sct has a very narrow chassis. If you need something with more real estate look into the kyosho sc or scr, or possibly associated's sc10, but the current sc10 is based on the t4 chassis and associated just released the b5 so probably within the next year or so there will be an update to the sc10 I would guess.

OK. I guess I don't necessarily need space on the chassis, but I do need space under the body to potentially stack things up. But now that you mention it, having things as low as possible would be nice; I will check out the SC10.

Also as for the battery be careful with the modern lipo technology as they are very different from the old nicd/nimh batteries. Lipo's do require a lipo specific charger/balancer and shouldn't drop below 3.1v per cell. If it does drop below 3.0v the pack is ruined and if the pack is charged above 4.2v (I think) the pack will likely catch fire.

Yeah that stuff is intense! Are they plenty reliable/long-lasting or is the attraction only performance for racers? What would you recommend for a solid everyday LiPo battery and charger with NiMH and LiPo capability? If for instance you have a number of them, do you have a charger that can keep a bunch of them going at once?

thanks,
Patrick

[krekeltronics]

Hate say it but something like a Traxxas Slash might be just the ticket for you. plenty available, pretty tough, and most importantly, it has a huge slab-like chassis plate made of plastic just perfect for sticking electronic boards on for development.

http://traxxas.com/gallery/electric/5807slashvxl/Slash-VXL-5807-Chassis-Top-View

the military use such chassis' for bomb triggering RC vehicles from what I understand.

Yup I read about that, that does look like a good platform. Whichever it is, it's probably going to end up with stuff strapped on and stacked up.

SC10 or Slash with this body seems like a nice way to go: http://prolineracing.com/bodies/desert-raid-clear-body/

I was surprised to see all the plastic frame/bracing parts all over on every car these days. I just remember Losi being primarily graphite and Associated being aluminum.

Do any of these manufacturers make the stuff in the USA any longer?

[Brocklee]

Also as for the battery be careful with the modern lipo technology as they are very different from the old nicd/nimh batteries. Lipo's do require a lipo specific charger/balancer and shouldn't drop below 3.1v per cell. If it does drop below 3.0v the pack is ruined and if the pack is charged above 4.2v (I think) the pack will likely catch fire.

Yeah that stuff is intense! Are they plenty reliable/long-lasting or is the attraction only performance for racers? What would you recommend for a solid everyday LiPo battery and charger with NiMH and LiPo capability? If for instance you have a number of them, do you have a charger that can keep a bunch of them going at once?

thanks,
Patrick[/quote]

It's mainly for performance/racing reasons, the lipo batteries weigh a lot less and the pack feels like a nicd/nimh fresh off of the charger throughout the entire pack until you hit the voltage cutoff. Generally what I do is run my nicd/nimh batteries with my cars that have a brushed motor setup and with my brushless I run lipo. As for the lipo's I like hobbyking lipo batteries, I've had the expensive $120 orion batteries and the hobbyking batteries perform just as good for a third of the cost, and for the charger i don't really have a preference, I currently have a thunder ac680 which will charge nicd's nimh's lipo's life's and a couple others that I'm sure I'm forgetting.

[rccars4sal]

I would go with a traxxas slash, and inexpensive (tacon)or (turnigy) brushless motor and esc system. Im not sure if arduino supports smartphone applications, but the better FPV outfits are either arduino mega, or dji naza. Both of those will support gps.

I second the recomendation for slash, because its BIG, and sturdy,, and plenty fast. It has enough suspension to handle just about anything, and its designed for bashers, so mis calculated way points would present less of a problem.

[krekeltronics]

I would go with a traxxas slash, and inexpensive (tacon)or (turnigy) brushless motor and esc system. Im not sure if arduino supports smartphone applications, but the better FPV outfits are either arduino mega, or dji naza. Both of those will support gps.

I have a little different priorities than a pure hobbyist might who wants to get it going as quickly as possible. The idea is to have to go through the process of configuring and integrating everything manually, so where I might otherwise use Arduino and all that stuff I'll be starting with a Freescale FRDM boards (KL25Z/KL46Z with the Kinetis ARM-based MCU's). It's still Arduino-compatible in terms of I/O, but the resulting designs will be much more amenable to commercial applications. For GPS I hope to use UBlox NEO-7. But since I don't see any shields or simple modules with that yet, I may default to the very similar NEO-6.

For talking to the phone I'm not sure what I'll use for the long-range radio but it will definitely have Bluetooth Low Energy. Ideally a Nordic part or something that can do both. The app will be custom (and like the firmware, released via GitHub if we get that far).

Servos (and the ESC unless I'm missing some advancement with the way ESC and receivers talk to each other) won't be too difficult I don't think since they're just +/- on the first two wires then pulses on the last one. Or do the 2.4GHz receivers and corresponding servos, brushless ESC's, etc. do something unique?

I second the recomendation for slash, because its BIG, and sturdy,, and plenty fast. It has enough suspension to handle just about anything, and its designed for bashers, so mis calculated way points would present less of a problem.

thanks, I'll have to check it out. Ages ago I did have a Traxxas truck and it did hold up nicely although in those days they were mostly nylon parts and bushings. Another priority I'm balancing is to do this with my (almost) 6-year-old little guy, so whichever we choose I'll want a kit as opposed to RTR. Maybe we need two - a Losi/Associated kit to build and play around with and a Traxxas basher type for the early R&D where we'll need durability over all.

I do also have an ancient Bolink flat-graphite-frame on road car I'm trying to resurrect to use with the project as well.

Keep the ideas coming guys - this is really helping me sort these things out!

Patrick

[krekeltronics]

you guys think this would be good to get started? In stock at my LHS:
http://www.hobbytown.com/Shop/Traxxas-58034-Slash-RTR-with-2-4TQ-Radio/

[rccars4sal]

Yeah, thats the big one. They actually make a big one and a small one. The small one probably no good for you. As for the 2.4 ghz radio gear,, I think its just the radio link,, and does not really affect the wired communications between servo and receiver. It probably affects it some,, but I use old servos and ESCs on 2.4 ghz radio gear all the time. Also, vice versa,, newer brushless motor equipment with older 27mhz radio gear works fine. Im into fpv and multi rotors,, but experience limited to hobby radio operated equipment. A smartphone interface would be pretty darn cool!

[krekeltronics]

OK here's what I'm looking at so far. We'll have a Traxxas Slash for the first run of development with that nice wide chassis, then as something sturdy for my young kids to get acquainted with R/C as I work on this project. I'm also ordering a TLR 22SCT kit since it seems inexpensive right now for what it is, and that way the kids can see it come together from parts. Once the hardware we develop is advanced enough I can definitely find a way to fit it on that narrow 22 chassis.

So for the Slash, as an RTR we have the electronics covered. How about SPC LiPo 5000mAh 40C 2S for batteries (http://spcracingbatteries.com/index.php?route=product/product&product_id=57)? If those look OK will they be fine for the 22SCT as well?

Charger I ordered is Traxxas 2933 EZ-Peak Plus 6 Amp which I think should get us by.

For the 22SCT, I have no idea, so here are some guesses:
* Novak NOV3337 EDGE 2S combo with 17.5 motor. This is $175, would there be a better way to go for this? I'm guessing today's ESC's have all sorts of fancy programmability I'm not going to need since I'll ultimately have our own hardware sending the ESC its signals. But if this is a good buy for the money it's fine with me.

* Futaba 3PRKA with R203GF receiver for $70 at amain. It seemed like the simplest possible decent radio. I know other brands are popular these days, but they all looked too fancy to me with big LCD displays and things. Is there a better bare-bones radio that you would recommend?

* Savox SC-1258TG servo. $70 seems pretty steep to me for a servo but I need something that will hold up. Any others to recommend for this application?

thanks guys,
Patrick

[rccars4sal]

For batteries, as long as its a hard case 2s lipo, then it should fit both slash and losi 22. For the motor, it all depends on how much you want to spend. My brushless motor esc combos regularly run about 60-70 dollars, and can be as fast as a 175 dollar set up. Just depends on motor specs(winds).

Ive been wanting to do a ground based fpv vehicle. Im thinking slash might be too fast for what I want to do though. I was going the other direction,, possibly a 1/16 scale tank chassis that moves about 7 mph, but can overcome difficult obstacles.

[scr8p]

probably gonna move this to the r/c tech forum sometime soon.