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Here's a DIY to build a HUGE RC Monster Truck. You'll need to have a welder.


I have enjoyed seeing remote controlled trucks come a long way over the past couple decades. I've even owned several of them along the way. It all started with the AA powered 2WD trucks with simple springs as shocks. Then along came 7.2V with oil filled shocks, then 4wd, then NITRO powered and then 2 speed transmissions capable of 50MPH with reverse. The past several years the industry has had no where to go except bigger. From 1/16th scale to 1/10th scale and even 1/8th scale. Well, I'm going to beat everyone to the punch. I'm going to design and build a 1/4 scale remote controlled truck with my own unique twist.

Step 1: Start With the Frame

I've made several drawings and I couldn't wait to get it out of my head and start welding! I've had this idea of an independent suspension where all swingarms pivot from a common center pin and all shocks are inline and attched to a parallel upper pin. I useda solid steel rod as the pin and welded matching tubing to the swing arms and honed them for a good fit. I'll do the same for the shock mounts. Here' s the start of it all. The 4 swing arms with the lower pin, front steering knuckles and 4 golf cart tires with ball bearing hubs. I made the swing arms out of 3" electrical conduit. The steering knuckle are simply 3/8" thick steel plates with washers, bolts & bearings to make for a proper knuckle. I had to weld a keyed sleeve into the rear hubs to make a proper fit to the 3/4" keyed axle shaft.

Step 2: Suspension Linkage


This is after the upper parallel pin is installed using H-links and the pneumatic cylinders (soon to be converted into hydraulic adjustable shocks) mounted. The engine is just sitting on it's mounts for now. But the differential and pillow blocks are in place. I had to design, weld and machine a sprocket that would fit perfectly over the differential and use the existing bolts. Then I designed, welded and machined a sprocket incorporated with the drum brake and wheel hub that fit the moped engine. Of course I crunched some numbers and calculated for a proper gear ratio. The differential sprocket is a 40 tooth and the drive sprocket is 15 tooth. This should give an end result similar to the moped's original ratio and performance which was speeds up to 48mph. Whooahh Can't Wait!!! I better plan on having an EASILY accessable kill switch on the vehicle and the remote.

Step 3: Make Shocks

Here's a picture of the pneumatic cylinders plumbed for a hydraulic shock application (another one of my hair brained ideas). There's a 10-turn valve inline so I'll be able to adjust the rebound rate. Also, the springs and spot welding are temporary (from ACE) until the proper ones I ordered come in. These shocks worked pretty darn well. I can close off the valves and stand on the truck without it moving or I can open them up and push the suspension to the ground with ease. This design has 18 inches of travel!

Step 4: Mount the Motor

Here's the motor welded into place. You can get sprockets and chain at mcmaster.com.

Step 5: Add Tank and Body

Mount a gas tank up high so gravity will feed it down. I found this body at the dump for free.

Can you see the proper springs under there now? I designed and machined spring guides and stops out of aluminum specifically for this project. Boy were those a pain to install! Also notice the muffler's under the rear wheel well and the gas tank under the dash. You can also see the servos on the drivers side swing arm. I coupled 2 super high torque 1/4 scale airplane servos together. They don't seem to have much power and the pull-pull cable system seems to have a little too much play so we'll just have to see how it all work out. This engine is electric start too! Yeah baby! I used two 6 volt batteries so I can split my RC controlls off of one and use them both in series for starting and getting charged by the engine. Oh, yeah, the engine is a 50cc air cooled two stroke with and automatic variable belt transmission out of a honda moped. I just happend to have rebuilt it about a year ago and had it laying around. You can also see the servo horn (small white round) just above the muffler. It's mounted to the engine and controlls the throttle and brake.

Step 6: Heavy Duty Steering

After the first test run I noticed the steering wasn't stable enough. The wheels kept wanting to turn in on each other. So, I made a 12V linear actuator controller using the electronics of a servo and 4 solid state relays. I bought a 12V actuator and hooked up solid linkage. It works much better now. Check out these videos. Also, the chain tention was an issue (I knew it would be) so I made an idler tensioner which works great I really got a feel for how dangerous this could be if it got out of control. I've taken every safety precaution I could think of. It has a "fail safe" that lets off the throttle and applies the brakes if it loses radio communication or gets a low battery and it has a kill switch on the vehicle which is also remotely activated.

I've been asked for plans on my steering "servo". Where do I start. First of all my truck is 12V but the radio stuff is 6V so I paralled two 6V batteries so they could be used to start the engine and get charged by it too. Then I just pulled off of one battery to power the receiver and servos. With that said. The solid state relay dirver I made for the actuator is controlled by 6VDC pulsed from the servo board but switches 12V source power to the actuator. You MUST use solid state relays and not the coil type because of the fast pulses. Also, you must use 4 of the. Two for left (+ and -) and two for Right (+ and -). All the relays do is take what the servo board sends to the servo motor and controlls the relays with that signal to give a similar signal only 12V and high amperage.

Here's the schematic. (REVISED 01/02/09 ... Thanks to Alan)

Step 7: Steering Servo Circuit Pic

Here's what the circuit looks like put together.

R, C & L are just soldered to the terminals where I removed the pot off the servo board so I could rig a pot on my steering linkage and it would give the proper signal to the servo board. I drove it without the pot in place and just soldered on there and in center position for a while but it doesn't have the "centering" effect. You have to steer left and then steer right to straighten it out.

Yes, messy and crude but it get's the job done and very nice and smoothly too.

Step 8: Complete Servo Actuator

Here is the completed unit. Just attach it to the steering linkage on the truck and I guarantee it will steer just about any size project you make.

Step 9: Videos

Here's a compilation Video and attached are some other videos including slow motion suspension movement.


Step 10: THE END

Prototype Results: There were a few small mechanical type issues that were easily solved in the maiden voyage. The vertical movement of the suspension was wonderful but lateral and centrifugal aspects of handeling were a bit "tight". The power wasn't as high as expected (probably a carb/jetting adjustment). Radio communication was good. There were no glitches or interferences with engine noise or other electrical interference. I used a resistive type spark plug and was conscious of radio type issues durring design in anticipation of those types of problems.

Well, it's been fun. Unfortunatley I don't have room for this beast in my garage so it's getting disassembled soon. All in all it worked out pretty good. I got the idea out of my head and all I wanted was to see a working prototype. So, these parts will sit on my shelf until I come up with something new to make. Any ideas?
<p>These are very cool, and I wish I had the time to build one of my very own. I love your step by step instructions on how to make your own remote control car. I need to make more time for a hobby like this, this seems like a fun thing to do with your son. &lt;a href='http://www.sunrisegolfcarts.com/Remote-Control-Golf-Carts-s/1817.htm' &gt; http://www.sunrisegolfcarts.com/Remote-Control-Golf-Carts-s/1817.htm&lt;/a&gt;</p>
<p>please all i need is the blue print</p>
I WANT ONE
You asked for a suggestion for your next project. I'd like to see a large RC landsailer with a wingsail. You could lose the engine. At a similar scale to this jeep, you could follow SPAD construction methods for a coroplast wing and get very good performance. Google &quot;DDWFTTW&quot; and &quot;Flettner rotor&quot; for more advanced windpower ideas.
Very well done. parts sourced from stuff laying around to keep cost down. Excellent, I see science and engineering background went into the design but Mister, That is the worst conceived chassis I have ever seen. Okay, function over form is alright but that frame looks like a refugee from Menieke.
You could use a wiper motor connected to a servo (with the motor removed, just used for location sensing) and then use an H-bridge motor driver to power it, which is what you already built. <br>http://www.youtube.com/watch?v=_iRI5VxCJxU<br>It is what I wan't to do if I ever get to making one of these. Mine will also be a 16 hp engine so I am trying to pick a good, high-speed gear ratio, I wish I had a CVT laying around.
can somebody say nitro !
Thats a scooter engine not a moped.
now to the 4wd version
how much weight can it carry? could it carry a preson?
this is awesome hi
How fast does it go? Great &quot;ible&quot; 5 stars.
looks good
&nbsp;Where did you get the suspension shocks?<br /> <br />
dude, take out the engine and drive mechanism and put this thing <a rel="nofollow" href="https://www.instructables.com/id/The-Recycled-Jet-Engine/">https://www.instructables.com/id/The-Recycled-Jet-Engine/</a>in the back<br/>
very cool i am building one but i cant find and actuator. I guess ill have to search deeper. What radio systems did you use? thanks.
how fast does it go????
ow and it's really cool
nice pet dog!!! :)
That's Pippi. She's a 7 year old Beagle ... my only child!
awesome project. are the R,C and L on the servo controller substitutes for Right, Common and Left. Just want to know because this is one of the many projects that im considering doing this easter/summer
Yes Madman. Right, Left and Center (or wiper). Those terminals go to the potentiameter that "tells" the servo circuit when it's at center. Please feel free to email me if you have ANY questions.
Anyone says RLC to me, and i start thinking of phase shift. ive been in electics to long. help!!!! i do have a question tho, is the potentiometer part of the kit, or can a better angular sensor be used. cheers evildoctorbluetooth
The pot has to match the one that is in the servo circuit you use for the driver. I can't imagine why you would need to be more accurate than a standard servo. It senses less than half of a degree.
I planned a similar sort of thing for an all-terrain radio control when I was about 14/15yrs but using 5 electric-start moped engines, 2 for forwards & 2 for reverse with tank style steering. The 5th acting as a generator. It was overkill at the time and really didn't know as much as I do now I never really got past the design stage due to lack of money and resources but some of the basic electronics worked and (unluckily or luckily can't decide) ended up in other projects. I might mod this and add a few of my other ideas to the build once I start it again. Some of the instructions in this have solved a couple of probs I had with the designs. Thanks for the 'ibble.
i have the plans to build one myself and i would like to know how you made the rc device controlers and what not. thanks
Great. I would love to see what you come up with. The RC devicese were mostly off the shelf stuff. The radio and receiver is a standard 2 ch surface Futaba set you can get anywhere cheap. I used a big Hitec 1/4 scale servo for throttle and just attached it to the throttle cable. I used the highest torque 1/4 scale servo for the brake and just hooked it up to the brake cable that was part of the moped transmission/drum brake system. The I made the steering actuator as you saw in this instructable. I used two 6 volt batteries in series so I could run all the RC stuff on one battery and hook the motors charging system up to the 12V series batteries and use the 12V seriesed batteries for the electric start feature too. That's about it. Please ask any more questions you want.
Hello, Me and my friends are working on a project, and we were looking for an rc car to strap our device to, but it seems that we are unable to locate it on the net. We were hoping that we could recreate it, but we dont exactly know how to program and make a remote for our recreation. And by the time we work it out, the time to finish up our project will be up. I was hoping you could give us a few pointers, our possibly point us at a few sites that may contain 3-4 ft rc cars. Please email us, me Yasaswi at yasaswi123@gmail.com. Thanks a bunch, Yasaswi and his fellow team members.
How much did your 12V linear actuator cost? I have a project vaguely similar to yours, and built something analogous to one of those, and I was wondering how much the more robust, professional ones cost.
Wow, that is impressive.
this is so kool im gonna go make 1 soon
Nice, btw I love Cake! Nice choice of music.

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