RC Crawlers

[DomOfTheDead]

One thing I’m unsure of is aftermarket component compatibility. If you buy a truck from one company do you have to stay in their sandbox? Or are the parts pretty universal? There also seems to be a lot of 1:10 support and I haven’t found a website with 1:16 parts.

Lack of upgrade and replacement parts support is the only issue I have seen for the off-brand 1/16 trucks. Market focus seems to be 1/10 and 1/24 sizes. Certain items are brand specific (axle and drive train parts) otherwise bodies, tires and electronics are fairly swap friendly.
Also depends on your build abilities. I have swapped a bunch of stuff around from various brands but things like wheelbase and track width have had to be adjusted.

 

[Cruisertrash]

This thing gets around my torn up garden bed surprisingly well!

The turning radius sucks, but other than that it’s doing great in mud, sand, at steep side angles, etc.

So excited right now.

 

[Cruisertrash]

 

[Cruisertrash]

So I went whole hog …. Yesterday I installed new suspension and steering links and today painted the cab. I found out thread locker dissolves plastic, so I learned something! I had to retrofit brass standoffs in place of crumbling plastic screw receivers. I also broke the ends of the knuckle steering arms off and had to drill new holes. It all works though.

Struggling with LED wiring. I’m trying to add two fog lights in parallel with the two headlights. When I connect the fog lights they come on but the headlights go out. I know electronics pretty well but can’t figure this out.

 

[Oneops]

https://youtube.com/channel/UCM2p-yUnKhEWCcujgNDamzw

When I was searching for what rig to buy I found this channel. It’s cool to see them run against each other and the challenge is a cool fun looking game vs running through gates. I wanna do that!
I was close on deciding and seeing the rigs I wanted running together helped for sure on which one I bought. But makes want to buy a whole lot more now! Lol

 

[Cruisertrash]

Still at it with my little WPL Chinese crawler. I finally upgraded the motor and all the electronics, but tonight I smoked the motor.

Upgrades/modifications:
370 motor
Hobbywing 1060 ESC
Flysky GT3 Tx/Rx
2S L-ion battery
(Same type of 7.4V L-ion battery as the truck came with, but higher mAh … I think)

It ran great on my test drive after putting it together, but … when the motor stalled against a steep climb it let out a little magic smoke.

I took the body off and ran it on the same obstacle and this time when the motor stalled and I gave it a little throttle it let out the rest of the magic smoke … motor is dead.

I’m still a little fuzzy on electronics in these things. So where did I go wrong?

 

[Cruisertrash]

One of the original batteries:

 

[Corbet]

In my experience the motors hate to stall out. It smokes them fast. Holmes rebuilt my last one for free. I didn’t stall that one but my Holmes controller will use the motor to hold the car on a steep climb. That was enough.

anyway low gearing is your friend. I dropped my transmission gearing and at the diffs then run a faster turn motor. Have had less issues since. I just won’t “park” T on a steep climb again.

 

[Cruisertrash]

In my experience the motors hate to stall out. It smokes them fast. Holmes rebuilt my last one for free. I didn’t stall that one but my Holmes controller will use the motor to hold the car on a steep climb. That was enough.

anyway low gearing is your friend. I dropped my transmission gearing and at the diffs then run a faster turn motor. Have had less issues since. I just won’t “park” T on a steep climb again.

I’m working with cheap no-name brand stuff here so the aftermarket is pretty much limited to whatever junk you can find on AlieExpress. There’s a few folks stateside 3D printing accessories like bumpers, but that’s it. I’ll check around for different diff gears but I’m not super hopeful. I know there’s a few transmissions out there, but most of the motors don’t even advertise their rpm, so it’s impossible to calculate gear ratios. Fortunately for stuff like 370 motors the cost is cheap - $8-10. Diffs & axles with pot metal gears are about $4. Etc etc.

Is there anything that can protect against motor stalls? Some way to kill throttle input when that happens? I imagine the motor was asking for an infinite amount of current in that situation. That could probably kill my ESC too.

 

[Corbet]

Is there anything that can protect against motor stalls? Some way to kill throttle input when that happens? I imagine the motor was asking for an infinite amount of current in that situation. That could probably kill my ESC too.

The answers to those questions are well beyond my RC pay grade.

 

[Notyourmomslx450]

Now that CM is over I need to get my Honcho going.

 

[DaveInDenver]

Is there anything that can protect against motor stalls? Some way to kill throttle input when that happens? I imagine the motor was asking for an infinite amount of current in that situation. That could probably kill my ESC too.

Is your motor brushed or brushless? Does your speed controller match the motor type you selected?

Stall current is the max a motor can draw. It's not infinite but a function of max torque spec'd at some voltage.

Are you sure your motor is capable of a fully charged 7.4V battery (around 8.4V)? You might be going overvoltage at 100% duty cycle. A motor should only ask for it's max current but if you put a higher voltage on it than it's rated for you will have problems, like a motor that's actually a 6V nominal, which is fine here with ~7.4V as long as you never go to 11.

There's various details that can change things in a dynamic sense with reverse EMF and PWM but normally you can just assume battery terminal voltage to be the max voltage the motor has to tolerate.

The hitch is some motors can't run from an open battery source hooked to its terminals, they have to be run with a controller to stay phased (e.g. sensed brushless). These more often will take out controllers rather than motors in a stalled state but they can get into weirdness when stalled in any case. I think people will put in clutches when going to these sorts of sophisticated drives so you don't test their overloads at stalls.

There's a fair amount of wiggle room playing with specs but if your motor/controller/battery are matched you should be able to ask it for 100% duty cycle over a couple of second transients without any issue. The worry would be that you hold a locked rotor indefinitely. Even if you have everything playing nice together if you sit there just holding the trigger full on stalled most of your work is going to heat and it'll eventually just burn up due to temperature and not enough air flow to cool.

 

[Cruisertrash]

@DaveInDenver I tore the truck down and found that one of the power leads to the motor was fried. It acted like a fuse! This is a plain-jane brushed DC motor and when I hooked it up to 7.4V it ran fine.

Regarding the upgrades, I'm working with this 1:16 no-name thing and the aftermarket world has very little documentation, especially for the electronics. I'm running a 370 size motor from AlieExpress that has ??? turns and ??? kV. I bought a Hobbywing 1060 ESC which has some amount of docs with it - for example, it can supply 60A which is way more than I'll ever need given the motor size I'm running. A lot of headroom in otherwords - but it would enable a stalled motor to fail sooner than it would die from getting too much juice.

I'm running a Flysky GT3 Rx/Tx, which is also just one step above zero-doc AlieExpress stuff. I can finally adjust end limits on my steering and stop killing servos. But I don't understand the other controls - like exponential factor or double rate. In fact, I don't understand any of the Rx's parameters for controlling the motor. I have been down the Google & YouTube paths and can't seem to find a "...for Dummies" or crash-course level tutorial. Learning as I go ... by frying motor leads apparently haha.

 

[DaveInDenver]

@DaveInDenver I tore the truck down and found that one of the power leads to the motor was fried. It acted like a fuse! This is a plain-jane brushed DC motor and when I hooked it up to 7.4V it ran fine.

That's interesting. The difference then must be due to the PWM, so I'm guessing there is in fact some weirdness with feeding AC to the motor. A PWM at full duty cycle is actually not DC but a veeerrrryyyy long high pulse interrupted by a very short off time at the switching frequency. In fact all PWM isn't DC unless it's run through a low pass filter.

Did you notice that it made a lot of whine when it was operating by chance? Technically speaking I think using a PWM to drive a plain brushed motor means you likely burned up the commutator and it could be you tripped across a unique oddity due to switching frequency being either too low or high. You might also have to provide some filtering that the controller might lack, e.g. a capacitor and snubber diode in parallel with motor.

Is the controller actually intended to drive DC motors or is it more general purpose? Some loads, like resistors, don't care and will essentially integrate the PWM into quasi-DC just fine. Other loads (like motors) might not like PWM (which can have very high voltage spikes, for example, or oscillation at your switch frequency) or any residual ripple on the DC even.

Regarding the upgrades, I'm working with this 1:16 no-name thing and the aftermarket world has very little documentation, especially for the electronics. I'm running a 370 size motor from AlieExpress that has ??? turns and ??? kV. I bought a Hobbywing 1060 ESC which has some amount of docs with it - for example, it can supply 60A which is way more than I'll ever need given the motor size I'm running. A lot of headroom in otherwords - but it would enable a stalled motor to fail sooner than it would die from getting too much juice.

The ESC can switch 60 amps (that's perhaps continuous but could be perhaps instantaneous, that's a datasheet question). It's not supplying that much. The current limit is the short circuit capacity of the battery, which is probably similar to it's charge limit of 1.5 amps but could be somewhat higher. But that's not the main issue I'm 99.8934175% sure. You could hook up that motor to a 60 amp 7.4V supply and it would run all day.

Betcha didn't think a cheap RC car would introduce you to the world of design analysis on active switching circuits, did ya?

 

[Cruisertrash]

Didn’t know the ESC sent a PWM signal instead of straight DC. I guess since it’s likely a digital device that makes sense. And as always I don’t have near your level of electronics knowledge so my grasp here is VERY rudimentary.

I soldered some larger gauge leads to the motor and it’s been running fine all day. I’ve been wary of stalls, since that’s the condition under which the previous tiny leads failed.

And for the record the ESC has an electrolytic that’s across the output leads to the motor. I soldered a ceramic across the leads at the motor too.

 

[DaveInDenver]

Yeah, it's definitely not a linear circuit like you're trying to imagine. You can think of it like ramping up and down a DC voltage and ideally that's fine but the realization isn't quite so simple. If it was a linear circuit that size device would only be able to switch a tiny fraction of that 60 amps. But the downside of switching circuits is Ohm's Law alone doesn't fit. You have impedance and EMF and all the interesting filter stuff. Enjoy!

 

[Cruisertrash]

Back on my bulls**t. I’ve done some more upgrades that have taken my little WPL as far as it can go. It’s a lot of fun but I’m looking for a more realistic, scale build I can do. I found this today:

RC4WD FJ55

Thoughts on the RC4WD TrailFinder 2 platform? Seems like most “serious” builds are Axial or Traxxis, but those seem much more expensive. I think I could probably get a basic build on this 55 running for $500 and upgrade from there. I was in the Crawl Space last year and those guys were telling me I couldn’t really do an Axial or Traxxis build for under $1000 - that’s way out of my desired budget for this kind of thing. This is 1:10 so it would be bigger than my WPL truck and it seems like it would be fun to have two different sizes for different terrains.

So … RC4WD: worth it?

 

[nakman]

I don't know if it's the same model, but I have the Marlin Crawler replica truck from RC4WD and it's the worst wheelin' rig that I have. It's super cool though- has real leaf springs, a lot of metal parts, looks like a miniature truck underneath. but the front driveshaft stripped almost immediately, and the leaf springs don't really flex, so the truck wheels like it has IFS.. maybe even worse. Also the speed controller is jacked- kinda doesn't really have reverse unless you slide the trim all the way to one side, and then it doesn't really go forward either. I took it in once to Dom's dude at the Crawl Space and he kinda just scratched his head at it... I am sure I could throw more time and money at it but I just haven't, I have so little time and so many other vehicles to maintain that the RC rigs tend to just get put away. But maybe there are other models of RC4WD that are better than the one I got.

 

[DomOfTheDead]

I agree with Tim, the TF2 are cool looking but perform terribly. I bought one and it is a total shelf queen. Most of my trucks are Axial as they have the best aftermarket but I disagree that they need that much money to preform well. Most of the RTR trucks are pretty solid out of the box, it's aftermarket upgrades that get expensive quick. I suggest looking at some of the Redcat trucks as the bang for the buck is a little better.

 

[MonPetiteShoe]

I picked up a Redcat Gen 8 V2 and I've been pretty happy with it. It's waterproof, durable, and the aftermarket is pretty big. The price is better than the current Crawler go-to's.
I swapped a few parts and that list added up pretty quick. I think I'm still in it less than a RTR Traxxas/Axial rig out of the box.
The mods that made the most difference:

• Swapping stock 17T motor to 35T motor. (Holmes Hobbies for $16) I've got a 20T and gearing for speed, but it requires a whole motor swap.
• Beefier Spur (32P) and Pinion (14T? 9T?) gears ($40 all told.)
• Stickier tires with heavier wheels and wheel weights. (Brass wheel weights got pricey. I paid a premium for some replica Steelies. Did not disappoint. $90 to $150?)
• Locked out the slipper clutch. (Included with the truck, just a small mod.)

Cons:
They only offer the body in two disgusting colors, Neon Green or purple. I would have enjoyed some factory colors from the Scout II.
It's easy to swap bodies, and the whole system is really modular.
It looks like they released the Redcat Gen9 which has a few quality of life improvements: Two speed tranny, better color options, better body options, and dash lights(?).
Basically the same truck with some wizz-bang upgrades. The two speed tranny is pretty cool. Sometimes you just wanna whip sh*ties in the snow, AND crawl around a bit without having to change a motor/pinion gear. It's the simple things.

It's lame there's only one or two options for 1/10, Toyota specific bodies. Mini truck, or 70 series. Variety is the spice of life.