Zero turn r/c weedeater
 

Just a theoretical idea here. I was eyeballing my new Gravely zero turn lawnmower and though that it would be cool to make a rc zero turn weed eater.

Started with the idea to stretch a MT chassis, and mount a weedeater power head to the center. That was going to make issues with 4wd and any sort of center drive shafts. So I came up with the zero turn design idea. rear wheels drive, single motor for each wheel.

I will use a stick radio, and a pair of 14xl motors on 3s lipo each going thru a pair of MM's setup as forward to brake to reverse. I need to make some custom gearboxes with double 5:1 reductions to get the speed down to around 8mph max.

Now I had planned to to use the 2 stoke weedeater power head to drive the blades, but then I decided that a large outrunner would be even better. Run the linked motor below on 10s lipo thru a airplane esc that I have lying around. I can set the dx6i to control that esc via the switches so that I can have low and high speeds and set different rates as well.

http://www.hobbycity.com/hobbycity/s...(Eq:_4030_AXi)

Plan to use this instead of the usual line that weed eaters use: http://www.trimnclean.com/http-//tri...ml/prod_2.html


So I plan to make a custom welded steel chassis, mount the gearboxes up higher at the back and use dogbones to drive the rear wheels. That way it will have plenty of clearance. I will make some sort of bearing carrier to hold the 3 blade cutter and take the load. The outrunner will direct drive the blades. The rear wheels will be narrower than the width of the blades as they spin, so that I can drive past objects and cut right up to them. I will use some casters on the front, just like zero turn mowers do. Battery mounting will be at the front, for optimum weight distribution.


My question is do you guys think that outrunner will be enough to power the blades? It is rated for 60 amps, and at 10s that will be 2200 watts. My intended use will be going around oples and trees, not cutting thick grass.+

All of the other equipment that I mentioned save for the outrunner is already in my possession. I have 2 14xl motors, 2 MM, a dx6i and rx, 60amp hv air esc, 2 4500 30c 3s lipos, 2 5000 5s lipo (for 10s) and plenty of building materials. Should I do this? I think it would be cool!

And here is pic of my new mower! http://pikelawnandgarden.com/resources/44z.jpg

It was $6800 new when the original owner bought it in late 06. I picked it up with 42 hours on it, not a scratch on it either, for 2500 bucks... Smoking deal.

42hrs isnt even broke in yet. You get the sweetest deals...

That is what I thought! I do seem to find some good deals... I have a method that involves passing up alot of what appear to be really good deals until I find the super deal!

Now all I need is a damn cheap trailer... 300-500 bucks does not seem too much to ask, but it is being difficult to find.

A lot of people selling trailers must think they have gold hidden in rust... I've seen old nasty rusted trailers in that price range. Can't imagine anyone paying that much though, when a brand new ones start like around 700

Yeah, make me wonder. I picked up a full steel twin axle car hauler for 150 bucks a few years ago... I know that was a smoking deal as people have offered me 2500 for it... Too useful to sell and I have plenty of room to store it. I just want a 5-6' x 10' trailer with a fold down ramp. Nothing special, but I cannot bear to spend 700 bucks on a new one... Maybe I can find one that needs work?

Rethinking the drive system. I still like the 2 5:1 reduction earsets, for a total of 25:1 at the wheel. But I think 4s will suit the MM better and provide more torque when coupled to an outrunner. Plus outrunners have more torque.

Heres what I found at HC:http://www.hobbycity.com/hobbycity/s...less_Outrunner

Around 50 bucks for both motors, I cannot go wrong. So I am looking at 100 bucks or so for the 3 motors, and about 100 bucks for the gears and shafts necessary to make the gear reduction units. Not sure what the bearing supported cutting blade thingy will cost to make, need some sort of good bearings that can handle forces up/down and side/side.

I will try to get something mocked up so that you guys can see what is in my head.

Did some digging to find info about the cutting blades. The product is called the weed terminator (i'll be back) and gives about 10" worth of cutting path. That will not be enough so I now plan to run 2 of them... Hope that outrunner is up to the task. I will have to figure out some sort of belt or chain drive. Any suggestions for that will be greatly appreciated. I do not feel like running 2 blade drive motors as that will require another esc purchase, and maybe 2 if I want them to match...

Sound like a fun and cool project. I would like to see this one James. It might just be in all the Wal-Marts by Fathers day next year if you pull it off. You could end up a millionare. No worries, I'd stick by you and still be your friend if it happens.

Hey Hey, Outrunner Man here. LOL

Stumbling across this thread kinda freaked me out. Looks like we're going to be building somewhat similiar machines. That's cool with me dude.

Let's make it happen. It's gonna be a war on weeds for sure.

Just to pass on some information here. The weed terminator head warns not to spin it faster than 8000 rpms. So base your figures around that to be on the safe side.

"My question is do you guys think that outrunner will be enough to power the blades? It is rated for 60 amps, and at 10s that will be 2200 watts. My intended use will be going around oples and trees, not cutting thick grass.+"

I asked myself this also. Then took a look at an Electric Weedeater I have that runs on 110 house current. The spec plate says 7 amps. Hmmm...........

7 amps X 110 = 770 watts. Just over 1 electric horsepower.(746 watts)

Let's not forget rpm's either. The outrunner you linked is a 400kv version. On 10S, you will be spinning the blades waaaaay to fast. On 4S, you'll be spinning the blades around 6000rpms.

Will it have enough power? Yes. :yes: If you spin the blade at the right rpms, and the motor can handle 1500 watt bursts, I think you might be surprised.

2 cutting heads? Belt or chain drive? Naaah, make them direct drive and use two motors. What shaft size will your mower deck motors have? I'm using Prop adapters for airplanes for the hookup. Direct hookup, no modifications. :yes:

If you do use outrunners for the forward movement, it will require alot less gear reduction. They have more torque and are more efficient. :yes:

This is going to be very interesting Linc.

I have made alot of progress on my build and will be updating my thread with pictures and info soon.

Hey Sike,

I was doing some more thinking on it last night as I was up late with a pain in the leg that would not let me sleep...

I think 2 motors for the 2 terminators is a good idea. Went back thru HC and found some of the red/blue can turnigy motors pretty cheap.

Good to know about the rpm max on the terminators. I figured that a std weedeater motor could do 15k rpm... I think a pair of cheap HC 60 amp escs on 5s lipo with 400kv motors will be the ticket for driving the blades.

I wanted some sort of bearing support for the blade shafts, just to take the load off the outrunner bearings. If this works well I plan to use it frequently and make some vids!

With my 25:1 gear reduction, 600kv motors on 4s lipo will get around 6mph, plenty fast for something like this. My zero turn mover only does 10mph and that seems too fast most of the time!

So this would be the 600kv motor that I would use to drive each rear wheel, so I would need 2 of them: http://www.hobbycity.com/hobbycity/s...ss_Motor_600kv

And this is a bigger motor that should do for the blades, one for each terminator, 400kv at 5s lipo is under 8000rpm: http://www.hobbycity.com/hobbycity/s...ss_Motor_400kv

Or I may just go down to 1 large 4s pack, like a 2-3p pack made out of 5k mah cells and run the whole deal on 4s, that would make it simpler. Not sure if I should run separate batts for the drive wheels and blades, I wonder if there would be any benefit? I am guessing the blades will draw more power than the drive wheels. Having 1 big pack would allow the bades alot of headroom should they need to pull serious current...

So I picked up a pack of 12 of the weed terminator nylon blades. I was going to buy 2 of the complete replacement heads with the blades on it and then realized that I am really cheap, and decided to make my own hub for the blades to bolt to. Given that the outrunners that I am looking at come with prop adapters, I figured that I could use them to attach a circular piece of steel to the outrunner and attach the blades radially around said steel. Something like a large washer will do.

So that cures a few design issues, so I guess it is time to order some equipment. I will need to sell some stuff first, as I am funding new projects with the money made selling stuff I have laying around, and not using any new money...

Sounds like a cool and extremely complicated project with 4 motors, 4 escs and 4 battey packs.

I am slowly making it less complicated as I get a better idea of what i can do with the equipment. Setting up the radio to control everything may be difficult, but I am confident that I can achieve the desired outcome.

I think that 2 or 3 4s 5000mah packs wired in parallel will do fine. Then feed off that to the 4 escs. Having a total of 1600watts available for the drive wheels should be plenty, probably could get away with sidewinder escs, but I have some spare MM escs. The blade escs will be controlled by the switches on the radio, hopefully. I need to read the manual thoroughly and make sure that the dx6 can do what is need it to. I will only be using 3 channels, 2 for the drive wheels and the other for the blades.

The switch-actuated blades may be a problem because IIRC you can't adjust the EPA for switches which means you can only get one throttle amount to the ESCs which could either be too much or too little.

could the motors be damaged if the blades come into contact with something solid? going from full rpm to 0 cant be good on them at least. Perhaps you could work a slippers in somewhere to alleviate the motors from the abrupt stop.