I am building a rather large bot with 4 motors mounted to a 50" X 30" steel frame in a tractor style movement. I believe I can use the Sabertooth 2x60 with each two motors on each side connected to the Sabertooth in parallel. I will use two 12 volt 24AH batteries in parallel for 24 volts to the Sabertooth.
This will be a slow machine but it will be heavily built and used as a yard robot. It will offer a platform and have interchangeable parts. I will have a cart, dump cart and I’ll probably build a seat. I’m setting my max weight at about 500 pounds.
I may not get enough amperage from the batteries and I may have to consider this and just simply I may consider having a dual voltage system 12volt/24volt thereby providing a 12 volt 48AH system. The motors run at about 2-2.5 mph at 12 volts and for the yard that’s fine.
I’m using a 2.5 inch tubular steel frame and I’ll use corner pins for easy removal of components.
I’ve not built a robot in years and I’m really looking forward to this. Any help would be greatly appreciated.
I would appreciate an opinion on the Sabertooth and thoughts if I’ll have any trouble with the size and weight of the unit.
I finished the build and ended up with 4 motors, mag wheels, 2.5 inch tube steel frame that is about 60 inches by 32 inches, 80 AH of 24 volt battery, key switch, each of the 4-pair of batteries is fused, Sabertooth 60x2 and controlled by a Futaba 2.4 Ghz 4-channel radio with the sabertooth in mixed mode. The end result is a very usable yardbot with a carrying capacity of 450 pounds and a rolling weight of about 150 pounds. I also use it to pull around my 5x10 foot trailer with ease.
I have video but I don’t know how to upload a video and it’s 80MB on my iPhone, let me know.
I uploaded a great diagram of the brakes, works great.
For fuses I put 30 AMP blade fuses in each pair of batteries. I didn’t see much of a need for a fuse/breaker inline with the motors since the Sabertooth has some over amp protection.
I’m sure I didn’t need that many batteries but I wanted the extra weight so I could pull the trailer.
The size of the yardbot is due to the size of the opening in our basement being 36 inches. I have big 5HP pumps for my pool and a lot of equipment that goes in/out of the basement spring and fall. This can go into the house with everything and back out in spring.
Right after I put it together we had bought too large chairs and of course I can’t pull the trailer with the truck across the lawn so I used the yardbot, what a great idea. I was able to bring the chairs right to the porch and it was easy for my wife and I to unload into the house.
I have driven around myself in it and it doesn’t care about the 200 pounds at all, works great. I’m sure it can handle in excess of the 450 pounds but I can’t see us using it for more than that.
I took the design to pride mobility years ago and they balked at the idea.
I don’t have the time but it sure would be fun to build them. The tube steel frame is all milled out for wires or access to mounts. Probably could have done it with angle but I needed a reason to use my milling machine.
This winter I’ll change the wheels to wider pneumatic mags and tires.
The batteries are wired each two of them in series with the 30 amp fuse going from the positive of the first battery to the negative of the second battery. With 4 pair of batteries there are 4 fuses. The fuses will protect everything and the batteries.
The brakes are great because when the yardbot is stopped it locks in place. Without the brakes the yarbot will go down a hill on it’s own. My yardbot would be better with pneumatic wheels and this winter I’ll make adapters to adapt 12-inch tractor tires to the motors.
You need more basics. Their are four wires on these wheelchair motors, two are colored red and black and these are for power to the motor. The second two are white and they are the brake wires in my diagram. The motors have brakes that are on unless a current is provided to the white wires. The brakes are simple magnetic brakes and their is no reason to remove them.
I am using a good RC system with 4 channels and a memory in the receiver that when loss of signal the unit returns to “0”. At “0” no power is going to the brakes and so they would be on. I had considered using a third channel and a relay that would cut power to the brakes and then the brakes would be on. After a lot of testing I’ve concluded I don’t need it. I’ve tried to loose the unit but I’ve not been able to. The RC I’m using also mates too a transmitter so if someone else had the same one they still would not be able to control the unit.
I agree that the RC system has to be thought out carefully because this has a lot of weight and power.
One last thing about the brakes. If you were to set these on a separate channel and with the brakes on you then applied power to the motors you may harm the motors. In the configuration of 4 motors probably not but just don’t test it. The schematic I attached works very well and if I recall I used about 1.5 amp diodes from Radio Shack.
I’m not sure what you mean by “in line”, look at the schematic I attached in a earlier post. All that’s being done here is that when the motor controller is activating the motors either for reverse or forward the brakes are getting 24 volts DC. The wiring for the brakes on mine was done at the motor controller. Very simple to attach the diodes as part of the motor controller wiring and shrink wrap them into the wires. Two things happen with the diodes, they allow DC to get to the brakes in forward/reverse and they don’t allow current back to the motors from the brakes. I had the original wiring from a wheel chair and so I kept the original plugs to the motors and I cut the long wire that went back to the original wheelchair controller a little shorter but it’s a clean install with the wiring done at the motor controller. This allows for easy exchange of motors should I need to. There is no change to the wiring at the motors. I hope this helps.
Wheel chair motors. Sabertooth 2 x 60 amp motor controller. Diodes for brakes. 10 gauge wire fused for batteries and 12 gauge for motors. Battery disconnect switch. Futaba 2.4 GHz remote control with fail safe. Batteries and 24 volt charger.
Not much of reason at all except to possibly increase the payload capacity. My thought was to increase the width of the deck to include the wheels, which would add about 10 inches in width. I also wouldn’t mind adding a add-on bench seat so my wife and I could drive around on it. Add two more wheels/motors and I can add another 200 pounds in load carrying capacity. I plan on adapting the motors to pneumatic 5 inch wide by 12-inch tires this winter. This would give the vehicle just a little give for the terrain. My width cannot exceed about 40 inches since the door into the basement is about 42 inches. After playing with it though I’ve decided it looks too good and works good so why mess with it. It’s important to me that it look nice and adding the extra wheels and width will give it a odd looking size.
I’ve been thinking about upgrading the yardbot this winter and adding a third set of motors to make the unit 6-wheels but after some thought I just can’t see how it would make the bot better. I thought I’d attach the picture in case anyone else was considering it. Looks cool and it would be a bit hard because I’d have to re-mill the frame as it is, welded and that would take some effort. I just hate leaving this the way it is, too much thought went into it and now I can’t come up with a better V-2. It’s not like small robots where you can make and remake frames from simple aluminum. This actually was a bit expensive to build. Maybe I can build frames to spec for others as I sure do enjoy using the milling machine and a milled 2.5 inch square tube chassis sure works nice with these motors.
If anyone has any ideas on how to build it better please let me know.
Hi …new here and new to making a robot. What you are describing in your build is EXACTLY the type of thing I am going to build …with four motors etc. Did you buy the 2x60 Sabertooth …and is it the solution for you? Also …I would love a description of what you have done with fuses etc. Thanks!
You have brakes on this too? Wow. Now on the fuses …they are located where then? They are to protect what? As you can guess I am a little new to some of the electronics aspect. My needs are going to be pretty demanding. This is all very interesting to me …although I have a lot of hobbies and so the robot idea is totally to take care of things I hate to do because of they either dangerous or very very strenuous. We have a farm that has some very steep areas that normally I only take care by hand with a weed eater, hand sprayer etc. The robot is going to mow, weed eat, spray or whatever else I find intrusive to do. Basically a rc controlled 4 wheel drive garden tractor. Thanks for your help on this.
Once again …thank you for the response. I assume the brakes that are usually in these motors have to go and would not suffice for the breaking you have implemented. I read that those original brakes had to be taken out but I forget why. I can envision what you mean if the yardbot is stopped on a hill it could start rolling down hill …those brakes are rc controlled too I assume. What happens if you lose RC control in any way?
yes I know I need to study this more and will. The input I got about the brakes comes from a book I am reading about building an all terrain robot …as well as several Youtube videos that indicate they pull the brakes off to do RC lawnmowers. However I see the application for them in my need. These others seem to be primarily doing mower for a lawn that I would just mow myself …I need the exercise!
