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Off Road, 4wd (or 6wd) RC Car

by davidbec08, published

Off Road, 4wd (or 6wd) RC Car by davidbec08 Sep 19, 2015
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Summary

This is a strong (high load carrying) off road RC chassis. It is designed to crawl around carrying things and to climb very steep inclines. It has fully independent suspension and 1 motor at each wheel.

You can see the 4wd version here:

https://youtu.be/a39qIS8JGv4

and a little more of its rock crawling abilities here:

https://youtu.be/-LaEoF4j1Rk

and with the FPV Camera from the Tank upgrade:

https://youtu.be/4jV0W-KFchE

I have also included plans and mounts for a 6wd version. (If you build this one, the axles need to be closer together as it is skid steer. Squarish vehicles work better). It makes use of a different mount for the electronics (transversely instead of longitudinally mounted).

It is skid steer, and makes use of an Aluminium tube for the chassis rail. This keeps weight down.

I've included the Rhino files so you can modify it more easily to your application.

INSTRUCTIONS:

CONTROL ARMS/WISHBONES: You'll need some 5-6.5mm aluminium rods (drill the holes out to suit what you have). Smaller is better.

RC: I used the cheapest of everything I could find, and went with 2x motor speed controllers, 1 for each side i.e. the left side motors are connected in parallel to one, the right side motors to the other. I use one stick of the RC controller to control the vehicle in an odd way: top left = fwd, bottom right = back, left bottom = spin left, right bottom = spin right and everything in between is turning left or right while going fwd or back. It doesn't take any getting used to.

You could use an Arduino or similar of course, like I did for our off road SLAM robot. This chassis actually has some advantages over that one, but you'd need to modify the various carriers for the LIDAR.

MOTORS: I used Dagu Wild Thumper motors (6V) and wheels and mounts. There are 34:1 Metal Gearmotor 25Dx52L mm (High Power) Code: MEC-30089. 4.3 kg-cm and 5.5 A stall.

Make sure you tighten the screws attaching the gearbox to the motor (I use loctite to make sure they don't work loose. They come from loose from the factory).

MOUNTS FOR MOTORS: Pololu 25D mm Metal Gearmotor Bracket (comes in pairs). The holes in the motor carrier (printed) align with these mounts

BATTERY: I used a 3300 mAh NiMH 7.2V battery. If you go 6wd you might try a higher capacity LiPo, though you'll get a lot of the NiMH for the 4wd.

SPRINGS: #157000003/22497 1/10 Model Car 85mm Adjustable Aluminum Shock absorber (2pc Blue)

SPEED CONTROLLER: 2x #9261000018/32025 HobbyKing X-Car 45A Brushed Car ESC chosen for the rating (45A) and price. any brand with similar specs would do. Remember it is skid steer so you'll be loading the motors quite frequently

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How much did all the not printable parts cost?

You can get every part except the aluminium tube ( $5) from somewhere like hobbyking. I think it is best to get prices from there.

With 4motors and 2 ESCs it isn't cheap.

HINGES: You'll also need some 5-6.5mm aluminium rods (drill the holes out to suit what you have). Smaller is better.

RC: I used the cheapest of everything I could find, and went with 2x motor speed controllers, 1 for each side i.e. the left side motors are connected to one, the right side motors to the other. I use one stick of the RC controller to control the vehicle in an odd way: top left = fwd, bottom right = back, left = left, right = right and everything in between. It doesn't take any getting used to.

You could use an Arduino or similar of course, like I did for our off road SLAM robot. This chassis actually has some advantages over that one, but you'd need to modify the various carriers for the LIDAR.

MOTORS: I used Dagu Wild Thumper motors (6V) and wheels and mounts. There are 34:1 Metal Gearmotor 25Dx52L mm (High Power) Code: MEC-30089. 4.3 kg-cm and 5.5 A stall.

Make sure you tighten the screws attaching the gearbox to the motor (I use loctite to make sure they don't work loose. They come from loose from the factory).

MOUNTS FOR MOTORS: Pololu 25D mm Metal Gearmotor Bracket (comes in pairs)

BATTERY: I use a 3300 mAh NiMH 7.2V battery. If you go 6wd you might try a higher capacity LiPo, though you'll get a lot of the NiMH for the 4wd.

SPRINGS: #157000003/22497 1/10 Model Car 85mm Adjustable Aluminum Shock absorber (2pc Blue)

SPEED CONTROLLER: 2x #9261000018/32025 HobbyKing X-Car 45A Brushed Car ESC chosen for the rating (45A) and price. any brand with similar specs would do. Remember it is skid steer so you'll be loading the motors quite frequently.

perfect

I checked on PC, Firefox, Phone. No luck. I appreciate the paste.

Maybe try a pc webpage for the instructions? There's quite a bit there.

Depending on what you're trying to achieve, this may be of more interest: https://www.thingiverse.com/thing:1806025

6 Wheel Rover for Lidar

Depending on what you're trying to achieve, this may be of more interest: https://www.thingiverse.com/thing:1806025

6 Wheel Rover for Lidar

Depending on what you're trying to achieve, this may be of more interest: https://www.thingiverse.com/thing:1806025

6 Wheel Rover for Lidar

Yeah I've already printed the 4wd above for my son. I was intending to add on mecanum wheels

http://www.thingiverse.com/thing:2473 for strafing. I have not yet decided on the controller. Probably just RC style for now.

Mecanum Wheel MK2
by Zaggo

Pololu 25D mm Metal Gearmotor Bracket

Pololu 25D mm Metal Gearmotor Bracket

I'm not sure what a BOM is?

The motor and bracket type are in the instructions. If you go to the Polulu website there's dimensions/CAD files for the brackets.

The bolts etc are all M3 20 or 35mm and the aluminium rod is 5.5 to 6mm.

If did include the rhino file. Get the trial version of rhino if you don't have it. You can check any unknown dimensions in there.

Bill of Material :-), basically the list of parts I need outside the printed. Which appear you provided here.

Basically I clicked on the instructions and it's empty or thingiverse is not displaying it.
Thank you.

Comments deleted.

Is there a BOM for this? I need the right size and lengths for the bolts and motors.

Not yet. I'm working on a better 6wd design.

Clearance for this one is affected by having the battery underneath. The new one will be better but a bit more complicated.

Hi,

anyone done 6wd version yet? I'm keen to build one of these for my APM rover, what is the ground clearance for this beast? by the way awesome job man

Hey Mate, I've finally decided to with the straight axle version of your bot. I do like it better.

1) the mount for electronics is such a tight fit I had to hammer it on. It can't move
2) the struts are glued in place - no rotation - using araldite (appropriate epoxy adhesive). They can't rotate on the chassis/ you could drill a hole through the bottom of them into the chassis and add a screw if you don't like glue (planes and cars made of aluminium have a lot of glue!)
3) all the movement of the suspension is via the rotation of the wishbones. having upper and lower ones of equal geometry means that the wheels stay as much as possible flat to the ground

Ok sweet, I am getting the look I want to have. I am going to add these wheels from a different thingiverse file and then I am going to grind up some rubber bands to into rubber band flakes and glue some on the wheel treads so I can have a little traction.

Hey mate, I've worked a little more on the rover, And I got to where I like it a lot.

I've decided that I will stick with the 4 wheel drive version you have built. Anyways Here is a update shot of it.

How did you keep the middle parts from turning or rotating if the rover has free rotation for its articulation?

https://lh3.googleusercontent.com/-lhw-TNRIOCY/VjAwRvJbQxI/AAAAAAAAAok/eADZW7HJHOM/s720-Ic42/Screen5.jpg

Oct 23, 2015 - Modified Oct 23, 2015

It sounds really hard!

But, that is ok! If you also want the sections to rotate around the chassis, you could print 'rings' that fix each chassis in place (stop them from sliding back and forth).

You then have options:

  1. For passive rotation - it just follows the land surface, you could leave it at that

You could use rubber bands to give each axle some resistance to rotation (they could simply go from the front of each chassis assembly to back, connected at each end to the chassis rail. as the struts move against them, they would be resisted by the rubber band) . This would give it huge articulation, but the independent suspension become a little redundant!

  1. What I think you are after: use servos and have active rotation (to achieve the effect something like the cross axle articulation Land Rover Discoveries achieve with their air suspension or is achieved with Kinetic suspension using hydraulics).

if that is what you are after, why not mount them on the chassis rail, or those 'fixing' rings I mentioned above? I think you would need bigger (like 16kgcm) servos, which are around $15. Obviously you'd need some sort of accelerometers/gyros too, but that isn't too hard with Arduino if you're into that? It sounds interesting for something as simple as this vehicle.

Here is a picture with all those options: https://www.dropbox.com/s/p8x0n4h8o88j5l6/Capture.JPG?dl=0

Honestly: it climbs almost anything and will get over almost anything as it is, but I know where you are coming from.

You may also be interested in the suspension arrangement of the design at http://www.thingiverse.com/thing:470486. That has solid axles that articulate around the chassis but uses springs. You could make a solid axle, that rotated around the chassis tube of the RC car design with springs or servos mounted to a tower on the chassis to damp/constrain the rotation too? It would have fewer parts.

SLAM/GPS 4WD Offroad robotic experimental platform

Yes that's what I am going for is passive articulation. And I will consult with you when I get my printer back before I get started if thats ok?

Oct 23, 2015 - Modified Oct 23, 2015

Hey mate, The problem I ran into would be mounting the small servos on your upper wish bone.

And I want to be able to do this when I am ready.

Here is what I want my rover to do, I want each section to be able to rotate on its own with no power for Articulation
https://lh3.googleusercontent.com/-iEJRVaXz1Hs/Vil5McwLCvI/AAAAAAAAAnk/1n9mnjhr7lQ/s720-Ic42/Screen3.jpg

It looks good in silver!

What are the problems? The one I see is the length for a skid steer.

You can use 2x transverse mounts to allow you to mount the axles closer together, and If you use the motor mounting brackets I recommend for the motors, you can offset the motors and wheels 1-2cm or so (maximum). I think that would be ok

What else have you noticed?

Oct 22, 2015 - Modified Oct 22, 2015

Just getting a feel how the rover will look when she is done, I see 2 issues maybe some time you can help if you have some free time?

https://lh3.googleusercontent.com/-lzSgZV1W0PU/Vih5mmND_7I/AAAAAAAAAnM/1Q1GCK6coBk/s720-Ic42/Screen2.jpg

I also forgot to mention: no servos required (especially little ones!).

The benefits of skid steer for a 'crawling' vehicle are that you can turn on the spot, the chassis will be much stronger for the same weight, and you eliminate the servos/need for a reciprocating steering mechanism.

Thanks man, I am going to be using little servo's my rover will be a little different then yours

Again thank you so much for the help.

ok - send us a photo when you are done!

Will do I am also going to rig it cinema 4d so you can see it rendered.

I also forgot to mention: no servos required (especially little ones!).

The benefits of skid steer for a 'crawling' vehicle are that you can turn on the spot, the chassis will be much stronger for the same weight, and you eliminate the servos/need for a reciprocating steering mechanism.

Modifying it to 6 wheel drive should be very easy.

  1. You just need to print the extra parts, and make the chassis rail (aluminium tube) longer. I've added a picture above for a 374mm long version, Make sure you download the upgraded wishbones (to match the strengthened wheel carrier)
  2. As it is skid steer, for 6 wheels you will need to move the axles closer together. This means that you need to lose the electronics platform or print the modified version (see the 6-wheel drive version I have added to the 'Thing files'. It is mounted transversely.
    My suggestion: print 2. One for the battery, one for the electronics
  3. Stick with the geared high torque motors. Choose the ESC carefully
  4. I would also suggest using softer springs if you add an extra axle - cut a loop out of the ones you have if they are like mine, or purchase softer ones. You can use the stiffer ones but axle articulation = traction
  5. I will shortly add the Rhino file showing exactly how I would do this, including the modified platform

In the next few weeks I will be uploading a lighter weight version 2 that will be easier to make and will use less springs.

Hi man, I am going to be making this little rover for my self when I get my printer back.

I was wondering if you can help me just a little when I get started? All I want to do is to make mine a 6 wheel drive rover with micro pro tower sg90 servo's for the drive train. and the rims and tires I have all ready for it.

My question is how would you mount a 3rd section drive train to your rover?

Thanks EonBrony - the printing of this is actually pretty easy. Not too many different parts.

Some tips:

  1. use the strengthened wheel carrier
  2. drill the holes to the exact right size before pushing the rods in
  3. I used 6.3mm aluminium rods but drilled the holes to 6.5. The plastic relaxes back
  4. anywhere that looks like it needs glue, use Araldite (Epoxy)
  5. if things aren't going together, sandpaper and a blade can fix most things. A heat gun can help too.

Any problems, send me an email.

I been looking for something exactly like this for forever. I'll see if I can print it. great modeling! keep up the good work!

May I ask, how do you get the heads up information (speed, horizon, etc.)?

The camera is a Garmin Virb. It records that automatically, is really reliable and not too heavy.

The Virb doesn't do that sir, Its the Elite Virb that does and its $100 us more then the normal Virb. Just an FYI I got stung on the virb so I am letting everyone know the difference.

Thanks!

I didn't know that. I do have the VIRB Elite.

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