{"id":1344,"date":"2019-11-16T22:05:32","date_gmt":"2019-11-17T04:05:32","guid":{"rendered":"https:\/\/www.protowrxs.com\/?page_id=1344"},"modified":"2019-11-16T22:22:39","modified_gmt":"2019-11-17T04:22:39","slug":"protomow","status":"publish","type":"page","link":"https:\/\/www.protowrxs.com\/index.php\/robotics\/protomow\/","title":{"rendered":"ProtoMow"},"content":{"rendered":"\n

August 2013<\/p>\n\n\n\n

First off this is definitely NOT a robot based on my \ncriteria but it was a fun project and may well lead to more autonomous builds \nand features in the future so here it is.\n\n<\/p>\n\n\n\n

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Looking for an easy way to reduce some back pain issues and having always wanted to sit on the patio and mow the lawn, those two desires met to complete this basic small RC lawn mower. There are many other similar solutions out across the net and this one is a very simple deployment… but it works.<\/p>\n\n\n\n

The Power Chair…<\/p>\n\n\n\n

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In order to move a RC mower you need some pretty good power and like most of the other RC mowers out there a used power chair was the easiest solution. Lucky for me I located a very nice chair that was dead according to the owner. I figured for $50 I was getting a steal as long as the motors worked so I picked it up and began debugging the system. The previous owner said it used to work but just quit one day after being left on the patio and maybe had gotten wet and never would power up again. <\/p>\n\n\n\n

I pulled the joystick controller apart and all \nlooked fine, disconnected the motors from the speed controller and put some 12v \npower to the motors and they both work so back to the controller. After dropping \na couple new batteries in I measured the voltages at the joystick controller and \nnothing. So I started tracing the wiring between the joystick controller on the \narm and speed controller in the base and bingo – the power wire had been caught \nup in some moving parts and cut in two. In fact the cut wire was in an extension \nwire that was in place so I just removed the extension and I had a working power \nchair!\n\n<\/p>\n\n\n\n

Of course I had to sit on the now nearly bare frame and drive around for a while with the controller. That is when I learned how powerful the speed controller and motors really were allowing me to plow through the yard without ever getting stopped. Might get some wheel spin but never bogging down or overheating. <\/p>\n\n\n\n

The Mower…<\/p>\n\n\n\n

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The mower is a hand me down \nfrom my mother when she purchased a newer model years ago. It needed a few \nlittle things like rebuilding the carb, cleaning up the starter, etc but overall \nwas a good self propelled electric start mower that I used for a few years after \nfixing it. What I did like about it was the electric start as I knew I would \nhave two 12v batteries in the Power Chair and could easily add push button start \nabilities to the RC version. I know I could even add remote start if desired and \nI installed more than a two channel radio but push button works well.<\/p>\n\n\n\n

The other concern initially was I wanted to insure I kept the ability to adjust the cutting height and even could revert the mower back to manual if I couldn\u2019t get everything to work as desired remote control wise. Otherwise I simply cleaned up the deck and painted it with some black bedliner quality paint that matched the chair base, cleaned up and repainted the engine cover, pulled the wheels and went from there. <\/p>\n\n\n\n

The Frame…<\/p>\n\n\n\n

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After sketching out a \nfew design ideas and looking over other builds online I started piecing together \nmy plans for the mower. Although it would have been desirable to have a shorter \nversion, that would have required pulling the chair base completely apart, \ndesigning and welding a new cage, re-mounting everything and a lot more work. I \nfigured I could live with some extra length if it made things easier so I \ndecided to pull the front casters and push the mower as close to the front of \nthe frame as possible. The front casters where a suspension type design allowed \nto move up and down and would not work for my mower needs anyhow. From there I \nbegan to build a frame to meld the two together.\n\n<\/p>\n\n\n\n

The frame actually \nworked out much similar that I figured it would be. A simple box frame with a \ncouple extensions on the back to tie in the rest of the chair base. Some 1 \u00bc \ninch square tubing from the local hardware store worked well for such a simple \nframe and after measuring out the square and chopping up a few pieces the core \nframe was tack welded together.<\/p>\n\n\n\n

In order to keep the adjustability \nand wanting to avoid having to build my own level adjustments, I just used the \nexisting wheel axles as my mounting points for the mower base. That has been \ndone on other projects I found as well and it looked simple enough. I had seen \nother mowers using the same tubing for the \u201cdrops\u201d that connect the top frame \ndown to the wheel axles but I had a couple ?\u201d plate mild steel sheets sitting \naround that fit the bill perfectly. I did have to bolt them the frame so they \ncould be removed to get the mower out of the frame but I actually like that \nbetter anyhow.\n\n<\/p>\n\n\n\n

The key on the drops was making sure I gave myself \nenough room to get to the height adjusters and still hang the mower stable \nenough for use. I located the axle positions in the plates, drilled the axle \nholes and then slide the drop plates over the axles allowing me to line up the \ntop wherever I wanted and whatever worked best. In order to clear the rear \nheight adjusters I slanted the top of the rear mounts slightly forward. The \nfront drops are straight down and work well in that position.<\/p>\n\n\n\n

For \nthe front casters I figured I may need some adjustability, which in the end I am \nglad I considered. To allow future adjustable front casters I bought some \nsmaller tubing, setup the 90 degree mount needed for the casters off the chair, \nand then slipped that tubing inside the extended frame front tubing. I then \ndrilled some bolt holes in the top of the frame and welded some nuts to the top \nover the holes. I can now slip the front casters into the frame and tighten down \nthe lock bolts allowing me to have some adjustments to extend the casters \nforward as needed.<\/p>\n\n\n\n

I\u2019m glad I allowed the adjustment as it has allowed me to keep the casters as tight to the mower as possible without having worry about getting too close or bending something that I would have to cut off and re-weld. Seems to be working so far and allows future adjustments as needed.<\/p>\n\n\n\n

The Radio Control \/ Speed Control…<\/p>\n\n\n\n

Note: This was the old original 2013 version. I have since replaced the chair controller and servos with a direct Sabertooth controller which is better with direct control and response.<\/p>\n\n\n\n

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The radio system is a simple \n2.4ghz RC car setup driving a couple servos. Instead of trying to hack into the \ncontroller, figure out how it works and how to control in internally, I simply \nadded a couple servos to move the joystick just like… ok, kind of like, a \nhuman would. One pushes\/pulls forwards and backwards, one pushes\/pulls left and \nright. Using a car type controller works well here as it\u2019s a simple throttle \ngoes forward \/ backward and steering turns left right. One could use a double \nstick radio but it\u2019s not really needed here. I\u2019m much more comfortable with a \ncar type controller anyhow from having driven and raced RC trucks in the past.<\/p>\n\n\n\n

By doing this I avoided spending another $100+ on a motor controller, \nleft the existing controller mounted where it was and can keep the 110v DC \ncharger built into the chair. Very very simple on the control side.<\/p>\n\n\n\n

\nSo in the vane of keeping it simple, I JB Welded the two servos to the \ncontroller and used some RC truck steering links and ball ends screwed into the \njoystick to drive it all. This allows the servos to keep the joystick centered \nwhen off throttle \/ steering and move it around in two dimensions as needed.<\/p>\n\n\n\n

There are some steering issues. As you can see in the pictures, I used \ndiffering lengths of steering rods to drive the joystick… not a good idea. In \nreality the LONGER the steering rod the better so the forward \/ backwards one \nworks well but the left\/right is really too short. Even after dropping another \nservo farther away from the joystick there is still some steering error as the \nstick moves forward and backwards and the short steering rod pushing the \njoystick slightly sideways. Easily corrected using the steering wheel when \ndriving but not ideal.<\/p>\n\n\n\n

The best solution might have been to mount the controller on a plate and then use as long of steering rods as possible to keep the unequal lengths from messing with each other. Doubtful I\u2019ll change it but just a tip if you\u2019re doing the same. <\/p>\n\n\n\n

Power Switches \/ Starter…<\/p>\n\n\n\n

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The wiring was minimal as well with all that was required is an on\/off for \nthe radio, kill switch for the mower engine, and a push button to drive the \nstarter. I left the power toggle on the chair joystick controller, which also \nhas a speed adjustment that can be used to slow things down if desired.<\/p>\n\n\n\n

Getting things started does require a few extra switches but it\u2019s really just 1) Turn on radio, 2) turn on receiver, 3) turn on chair controller, 4) Turn off kill switch, 5) prime mower with built in primer bulb, and 6) push the starter button to fire it up. When done I just turn them off in reverse and plug it back into the wall until the next time. <\/p>\n\n\n\n

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