Need recommendations for a slow-moving, electric, off-road 4x4.

[wosser]

I don't know much about the modern RC scene, so please bear with me. I'm looking for an electric 4x4 style car or truck that has the following attributes:

• Rotary encoders on all 4 wheels.
• Low speed - 10 mph is easily fast enough.
• Simple DC motor - not necessarily brushless (BLDC).
• Proper 4 wheel drive using appropriate differential gearing.
• Simple but functional suspension.
• Heavy chassis would be beneficial, maybe something I can add weights to?
• Budget: sub $200 or thereabouts.

I want to be able to drive on terrain like smooth concrete, dry grass, dry sand and gravel. Slopes up to 30 degrees max. Doesn't need to be waterproof.

Radio system isn't actually needed, I'll provide my own controller system and electronics.

Does such a thing exist? The main thing is that I need to be able to use some form of encoder to check each wheel's speed.

 

[Chubaka]

Welcome to the site. Not sure about encoders but I'm sure something is around in today's gadget world.

The truck your looking for is 1/10 or 1/8 crawler. Axial scx10 and Traxxas trx 4 lines are popular. There are others also. Drawing blanks atm. Crawlers come with locked centers and front and rear axles so the all move as one.

 

[wosser]

Thank you for the welcome and your reply. That Traxxas link is mouth-watering stuff! But total and utter overkill for me though.

So rotary encoders are not a "thing" in the RC world, or do I misunderstand?

I'd need non-locking diffs for my project.

 

[bill_delong]

I have never heard of a "Rotary Encoder" so I had to look it up to see what you're talking about and I have no idea what this has to do with RC?
https://en.wikipedia.org/wiki/Rotary_encoder

Based on what you're describing for everything else, it sounds like you want something between a "Rock Racer" or "Crawler"

For your budget a crawler will be more in line but these have locked diffs to get better performance in crawling over large obstacles:
https://www.nitrorcx.com/51c927-madvolt-10-jeep-blue.html


Not sure if anyone makes a brushed rock racer, but this what to look for if you want more speed with fluid diffs instead of locked diffs from a crawler:
https://www.horizonhobby.com/produc...rushless-rtr-with-smart-and-avc/LOS03028.html

 

[wosser]

A rotary encoder just gives an electrical signal when a shaft turns through a certain angle. It's a way to measure how fast an axle is turning in real-time

 

[tudordewolf]

So rotary encoders are not a "thing" in the RC world, or do I misunderstand?

They're very uncommon for recreational R/C, compared to their ubiquity within the robotics community. Part of the issue is that they're usually already part of a motor / gearbox setup, rarely are they standalone units that you could slap onto an axle.

Robots with 4 motors driving 4 wheels are usually how that kind of feedback is accomplished, while RC's use a driveline to distribute power from 1 motor.

A cheap 1/10th crawler meets 90% of your criteria:

• Low speed
• Simple DC motor
• Simple but functional suspension.
• Heavy chassis
• Budget: sub $200

Can be accomplished with just about any budget 1/10th crawler - Redcat's Everest-10 comes to mind.

But these next 2 bullet points:

• Proper 4 wheel drive using appropriate differential gearing.
• Rotary encoders on all 4 wheels.

Are harder to incorporate, at least into a crawler.. Many/most hobby-grade RC trucks have 4-wheel drive with working differentials, but won't have as heavy a chassis / weight capacity without going a bit larger which will be more expensive. Encoders on all 4 wheels would require a pretty custom setup, you might be able to glue magnets to the the inside of the wheel rims and put hall sensors on the hubs? Just an idea.

Would it at all be acceptable to have the rotary encoder on the motor, and derive the wheel's position from that? With locked diffs, you'd know all 4 wheels' position to be the same all the time...

Edits: for clarity and accuracy.

 

[biggman100]

I don't know much about the modern RC scene, so please bear with me. I'm looking for an electric 4x4 style car or truck that has the following attributes:

• Rotary encoders on all 4 wheels.
• Low speed - 10 mph is easily fast enough.
• Simple DC motor - not necessarily brushless (BLDC).
• Proper 4 wheel drive using appropriate differential gearing.
• Simple but functional suspension.
• Heavy chassis would be beneficial, maybe something I can add weights to?
• Budget: sub $200 or thereabouts.

I want to be able to drive on terrain like smooth concrete, dry grass, dry sand and gravel. Slopes up to 30 degrees max. Doesn't need to be waterproof.

Radio system isn't actually needed, I'll provide my own controller system and electronics.

Does such a thing exist? The main thing is that I need to be able to use some form of encoder to check each wheel's speed.

At that price, and with those specs, you would probably be better off looking at motorized robots. Nobody in the RC world does a rotary encoder at each wheel, and, at the price you are looking at you are very limited, however, one thing you didnt mention was size, or, in the RC world, scale. RC cars come in everything from 1/24TH scale, all the way up to 1/5TH scale. 1/10TH scale is about in the middle of that (1/24TH, 1/28TH, 1/18TH, 1/16TH, 1/14TH, 1/12TH, 1/10TH, 1/8TH, 1/7TH, 1/6TH, 1/5TH are the popular sizes). The bigger the second number, the smaller the car. Some companies to look into are WLToys, Axial, EazyRC, and FMS for smaller scale, Redcat Racing and Exceed RC for 1/10TH scale in your price range, and, anything 1/8TH scale and bigger will be way more than $200. For something with true 4WD, you are going to need a crawler, or rock racer, but, they have locked diffs. Another option for a 4WD, with open diffs, is to look for some of the faster stuff (short course trucks, buggy, truggy, monster truck), and try and run a crawler motor and see if it works. The reason i say any of the faster stuff is that, that is the only way you will get open diffs. You could get a crawler, and build a bracket to run a rotary encoder that turns as the tire turns, but, that will be a bit of work, but, it is doable. The hardest part would be knowing if the encoder is accurately reading tire revolutions. If it isnt set right, it could read them improperly, which in turn would show them going either faster or slower than they really are. Something like this, although almost double your budget, would better suit what you are looking for: https://www.robotshop.com/products/...9SJfE3ltki5WR8QX8CPRdyMWc9p4izUhoCmaYQAvD_BwE

 

[Sixtysixdeuce]

Might help if you would be less cryptic about your project. I work in a world of servo motors with high resolution encoders and resolvers facilitating extremely precise rotary movements, but can't for the life of me figure out why you'd want that at the wheels of an RC ground vehicle. I couldn't care less what the rotational speed or total revolutions of each individual wheel are, just that goes how it's supposed to. As stated by others, it's just not something that's done, because why would you?

 

[wosser]

As stated by others, it's just not something that's done, because why would you?

I see. I'll do some more research. Thanks.

...Some companies to look into are WLToys, Axial, EazyRC, and FMS for smaller scale, Redcat Racing and Exceed RC for 1/10TH scale in your price range...

That's great, thank you for these suggestions, I'll check them out. I think you're right that I'm not likely to find an off-the-shelf vehicle that will be easily moddable to add encoders. Makes sense about the faster vehicles having open diffs. If I'm going to have to build something custom (which I'm happy to do), a monster truck chassis would make sense because the larger sizes would give me more space to add new parts. I'll have to revise my budget too!

My project is related to traction control (as seen in the automotive industry) and specifically in this case traction monitoring. Measuring the wheel slip in real-time gives me some useful data about the surface I'm driving over.

Thanks for your advice, much appreciated.

 

[Chubaka]

The original scx10 were open diff. These are them. They should be open, if not they have a locker instead of the diff gears which can be purchased.

https://www.ebay.com/itm/224929881506

 

[biggman100]

I see. I'll do some more research. Thanks.


That's great, thank you for these suggestions, I'll check them out. I think you're right that I'm not likely to find an off-the-shelf vehicle that will be easily moddable to add encoders. Makes sense about the faster vehicles having open diffs. If I'm going to have to build something custom (which I'm happy to do), a monster truck chassis would make sense because the larger sizes would give me more space to add new parts. I'll have to revise my budget too!

My project is related to traction control (as seen in the automotive industry) and specifically in this case traction monitoring. Measuring the wheel slip in real-time gives me some useful data about the surface I'm driving over.

Thanks for your advice, much appreciated.

Actually, a 1/10TH short course truck may be a better route, since almost all of them ( Arrma, Losi, Team Associated, Tekno, Traxxas) are more 1/8TH scale sized than 1/10TH scale. If you look, you can sometimes get used short course trucks (my recommendation for that would be the Arrma Senton 550/mega, or the Traxxas Slash 4X4) for less than $200. Being that they use a longer chassis, and most are wider than a monster truck as well, or, at the very least, the same width, it might give you more room for the encoder motors, and needed electronics to run the motors. Another option, although possibly not ideal, instead of running the encoders from the wheels directly, is to possibly find a way to run them off the driveshafts. The upside to that idea, there would be more possibilities as for how to mount the enconders to the upper arms, or, in some cases, the upper links. That is why i recommended the two trucks i did, because, if you get the brushed, basic version of either of those trucks, they have wide upper fixed plastic links, that you may be able to mount the encoders to, if you can find a way to run them off the driveshafts, instead of the wheels, and, even if you have to run them directly off the wheels, the fixed plastic links may make it easier to mount them so they run inside, instead of outside the wheels. And, if you need the extra ground clearance of a monster truck, you can easily put monster trucks wheels and tires on almost any short course truck. Another idea, that i have seen done, is to make a ring that will attach to the wheels, that the encoder runs off of. This video shows how he set up encoders on a robot, but, you might be able to use his idea in a similar way on an RC car:

 

[Panther6834]

Hate to have to put it this way (I try to be as 'positive' as possible)...but, in all honesty, I don't believe there is ANY vehicle that will meet all of your requirements...especially the "under $200" requirement. Everything I can think of meeting all of (or, as close as possible to all of) the other requirements will easily cost you at least double your 'maximum' amount. Either way, good luck in finding what you need.

 

[Sixtysixdeuce]

I see. I'll do some more research. Thanks.


That's great, thank you for these suggestions, I'll check them out. I think you're right that I'm not likely to find an off-the-shelf vehicle that will be easily moddable to add encoders. Makes sense about the faster vehicles having open diffs. If I'm going to have to build something custom (which I'm happy to do), a monster truck chassis would make sense because the larger sizes would give me more space to add new parts. I'll have to revise my budget too!

My project is related to traction control (as seen in the automotive industry) and specifically in this case traction monitoring. Measuring the wheel slip in real-time gives me some useful data about the surface I'm driving over.

Thanks for your advice, much appreciated.

If you're trying to develop components, such as a tire or suspension part, you'll want to use a chassis that they're meant for. A 4 wheel independent suspension monster truck chassis is going to behave very differently from a solid axle crawler. Likewise, a buggy or truggy has different suspension geometry and often a center differetial, and we use different weight fluids inside the diffs to make them behave like a posi unit by inhibiting spider gear movement through the very viscous medium. The 1/8 critters I run around here on our property have 1,000,000 CST in the center diff, 60k in the rear and 30k up front

 

[wosser]

I'm going to go down the robotics route instead of RC. Looks like a cheaper hobby too

Thanks to all.

 

[airslither1982]

I don't know much about the modern RC scene, so please bear with me. I'm looking for an electric 4x4 style car or truck that has the following attributes:

• Rotary encoders on all 4 wheels.
• Low speed - 10 mph is easily fast enough.
• Simple DC motor - not necessarily brushless (BLDC).
• Proper 4 wheel drive using appropriate differential gearing.
• Simple but functional suspension.
• Heavy chassis would be beneficial, maybe something I can add weights to?
• Budget: sub $200 or thereabouts.

I want to be able to drive on terrain like smooth concrete, dry grass, dry sand and gravel. Slopes up to 30 degrees max. Doesn't need to be waterproof.

Radio system isn't actually needed, I'll provide my own controller system and electronics.

Does such a thing exist? The main thing is that I need to be able to use some form of encoder to check each wheel's speed.

I hate to be the one to tell you this. but in today's RC market your not going be able to get much of anything worth it's weight in spam for $200 or less. The only thing I can think of in that price range is a "Danchee ridgerock crawler" there available RTR for about $150 they are very slow about 4-5 mph 4x4 4ws. However there made almost entirely of plastic. And I'm not sure how available parts are for them. I'm afraid if you want something of any real quality your looking at price range of at least $450-$650

 

[biggman100]

I hate to be the one to tell you this. but in today's RC market your not going be able to get much of anything worth it's weight in spam for $200 or less. The only thing I can think of in that price range is a "Danchee ridgerock crawler" there available RTR for about $150 they are very slow about 4-5 mph 4x4 4ws. However there made almost entirely of plastic. And I'm not sure how available parts are for them. I'm afraid if you want something of any real quality your looking at price range of at least $450-$650

He already decided to look into something more in the line of robotics. As for the RidgeRock, since it is available under a couple different names, parts are available from ExceedRC (MadStone, MadWatt, and Mad Gear use the same parts as the RidgeRock), Redcat Racing (RidgeRock, Everest 10), and Hobby Park, and, even though it is mostly plastic, it is fairly durable. The only real differences between the RidgeRock and Everest 10 are the arms (Ridgerock has plastic arms, Everest 10 has aluminum), the 4 wheel steering (stock on RidgeRock, option on Everest 10), body, wheels and tires.