Refurbing an R/C mower

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Sidecar Bob
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Refurbing an R/C mower

#1

Post by Sidecar Bob »

Some years ago my neighbour Lee built this using the wheels & motors from an old electric wheelchair with added framework to suspend a Honda gas mower and electronics for the controls.


Last year he bought a robot mower and gave me the R/C one to play with. From what I can tell it would have worked if I just hooked up batteries and filled the gas tank (I'd want to do an oil change too) but some of the welds have cracked over the years, particularly where he welded the square tubes for attaching the wheelchair/framework part to the mower's sheet metal deck so I want to do some reinforcing.

Lee & I have been discussing what he did and what is needed. He put it together in a hurry to prove it would work and never got around to adding reinforcements and finishing it off. He originally ran it with U1 size batteries because he had them (he was inspired to build the mower when someone gave him a few old wheelchairs to play with) but when they needed replacing he bought bigger marine deep cycle batteries and it had enough charge to cut his grass twice on a charge. I said I'd prefer to make charging it every time a part of the routine so I don't forget how much charge is left (not to mention that if I end up with lead acids, leaving them half charged a lot can shorten their lives).
We figure if the 250W motors draw 10.4A (he says it should be less most of the time but its a good number for estimating) that's approx. 21A total (always rounding up in estimating) so I need a minimum of 32 AH to run it for 1.5 hr (longer than he thinks it should take to cut everything) so I should shop for a minimum 40 Ah battery.

I spent a few days investigating the possibility of using lithium batteries, primarily so that I wouldn't need to maintain them in the winter. But a set with enough capacity for this would have cost about $1000 CAD and I learned that AGMs do best if charged and left alone during the off season anyway. I emailed back & forth about what I need with someone at saskbattery about what I need and he pointed out that the Ah rating you see is the 20 hr rate (40Ah = 2 amps for 20 hrs) but if I'll be drawing over 20A I need to pay attention to the one hr rate which is much lower. He recommended 50AH ones which have a 31AH 1 hr rate. At this point in the season I probably should have waited until spring but I ordered a pair of these
https://www.saskbattery.com/ecommerce_122.htm

And one of these so I will be able to charge both
https://www.amazon.ca/gp/product/B087WXF42Y

I didn't think of taking pics until I had removed the electronics but you can get a pretty good idea of what I started with from this
1 Ready for disassembly.jpg
The batteries have to fit this space. The ones I bought are 196 x 165mm so there is plenty of room
2 Space for batteries.jpg
An hour or so of work later it was ready for me to start planning the mounts for the batteries. You can't see them in the pics but the mower's deck the deck is cracked from the stresses of the running gear everywhere he had welded to; I didn't feel it was wise to weld to the welds so I needed to undo what he did and start over for most of it.
3 Stripped.JPG
Because it steers by varying the speeds of the motors the front wheels need to be casters. Lee used the ones from one of the wheelchairs with part of its frame to mount them, supported at the rear by square tube posts welded to the deck. That may have been OK if he had added gussets to keep them from moving but without them every time it steered those posts were pushed sideways. 8 years later the deck was cracked so badly that there was only about 1/4" of steel left connecting each of them to the rest of the deck and bending them back & forth a few times broke that
4 Holes in deck.JPG
The last few days have been calculating. cutting & fitting. I started welding yesterday I'll try to have more pics soon.
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Re: Refurbing an R/C mower

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Post by 5speed »

:popcornx2
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Re: Refurbing an R/C mower

#3

Post by Whiskerfish »

Looks like a fun project!
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Re: Refurbing an R/C mower

#4

Post by Track T 2411 »

Whiskerfish wrote: Sat Sep 05, 2020 5:03 pm Looks like a fun project!
I agree! Looking at the setup, it might be easiest to just build a square tube frame and 'hang' the existing mower deck from it rather than relying on the deck for structure.
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Re: Refurbing an R/C mower

#5

Post by Sidecar Bob »

If I was starting from scratch I probably would but I've decided that other than the colour of the paint I want to keep the same configuration he had. What I'd really like to do is extend the existing framework rearward and attach it to the "plate" (actually a piece of industrial sliding door track) that the motors bolt to but the existing frame is aluminum and I don't think it is wide enough for 2 batteries to fit between.

I've been busy with other stuff so I haven't accomplished much welding but I am making progress and I am taking pics.

To tide you over in the meantime, here are links to the electronics he gave me with it:
Controller for the wheelchair motors https://www.dimensionengineering.com/da ... th2x25.pdf
Radio control module for it https://www.spektrumrc.com/Products/Def ... =SPMAR6210\
Additional "remote receiver" plugs into that. Apparently the remote receiver somehow acts as a failsafe and makes the receiver return to its base settings (zero speed, straight steering) so if it looses signal it will stop (this can be tested by switching the radio off). https://www.spektrumrc.com/Products/Def ... ID=SPM9645
Radio control https://www.spektrumrc.com/Products/Def ... Id=SPM6630
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Re: Refurbing an R/C mower

#6

Post by sparkyrasmus »

Hey Bob, I was wondering what you were spending your time during covisolation. Crazy project. I have about 2 acres of lawn if you want to drive out to test it.
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Re: Refurbing an R/C mower

#7

Post by Sidecar Bob »

I don't understand how some people are bored during this. I'm busier than ever, but I guess that's part of being retired :roll:

When I finished with the riding mower yesterday I drove it into the shed as usual and when I turned the key off it made a loud CLACK!!! as it stopped and it won't start again and I can't turn it by hand. It appears to be something inside the engine so I guess I'm working on this one just in time.
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Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Re: Refurbing an R/C mower

#8

Post by Sidecar Bob »

Before anyone comments on my welding I'd like to say that I am pretty good at grinding ;-)

Actually, I'm getting better at welding but I don't do it often enough to be as good as I would like. Lee originally only welded the bottom edge of the plate (actually a piece of industrial door track) to the bottom edge of the deck but when the deck started to crack and allow the plate to move he added the brace on top but it wasn't enough and the deck started to crack by it. I removed that brace, welded a piece of steel over the cracks, found a piece of 3/8" steel rod to use as filler (doubled where the deck is lower) and welded it in. I also touched up the welds at the bottom but I didn't take pics of that.
05 Top of plate welded to deck.JPG

I'll show a full pic of the new battery tray shortly. I designed it to also reinforce the deck and repair those holes from the posts. This pic shows one of the plates (3" of 1" flat steel) that I welded over the holes from below. Welding the battery tray's crossmember to these plates through the holes in the deck & welding both to the deck at that point would probably have been strong enough but my sense of "belt & suspenders" kicked in and demanded a 5/16" bolt through the plate and the crossmember as well. I used carriage bolts so that less grass would build up around the heads.
06 Plate & bolt under deck.jpg

Continuing with the belt & suspenders theme, I welded the nuts to the bolts and the frame member so they can't come loose
07 Welded nut.jpg

I briefly contemplated extending the framework for the front wheels to attach to with more of the bed frame angle (frame is aluminum so I can't weld to it but there are places on the side and top to bolt to so that would have been strong enough) and adding posts of angle to the plate for them to meet, similar to what those who have hung mowers from complete frames have done but the angle would have had to face away from the battery tray and be cut out to less than half to clear the motors so I decided posts in the original locations made more sense.

I cut the broken pieces of deck off of the original posts, trimmed them so the holes would be the same height above the deck and cut them down to be just about even with the tops of the front wheel frame. I wanted them to be attached solidly enough that the side forces from steering wouldn't break them off again so I temporarily attached the frame, bolted the posts to it and tied the rear of the frame so that they were firmly against the battery tray's crossmember (the welded nuts are hidden inside the posts). The posts meet the crossmember about 1/4" away from the upright part of the crossmember so I made brackets from some smaller angle to brace the posts to it. I clamped the brackets to the crossmember to align them and then to the posts, then unclamped them from the crossmember, unbolted them from the frame and welded the brackets to the posts on the bench, after which I bolted & clamped the post assemblies back in and welded the posts & brackets on (you can see one of my best welds and one of my worst in this pic).
08 Post well braced.JPG

(I'm breaking this into 2 posts so the next part will be here in a few minutes)
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Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Re: Refurbing an R/C mower

#9

Post by Sidecar Bob »

The full battery tray (this was all done before I plugged the crankcase breather and flipped the mower over to weld the plates under the deck and added the posts but I didn't think of pics until later). I started by clamping everything in place and tacking the side members to the crossmember (near the engine), then moving that assembly to the bench (actually an old Workmate that I use for welding and other rough work) so I could weld all around the joints inside & out. After that I put the assembly back in place to locate the rear support onto the plate and clamp it in place, removed the assembly and welded the support to the plate. Next I put the assembly back, clamped the crossmember down and welded the ends of the side members to the plate, the rear support and the high parts of the rear of the deck (inside & out) and welded the crossmember to the deck. The cross support for the batteries nearest to the engine is bolted in instead of welded so that it can be moved if the next set of batteries are a different size.
09 Battery tray reinforces structure.jpg

I temporarily bolted one of the wheel/motor assemblies back on so I could check the relationship between the ground (& wheels), the frame and the posts. The bottoms of the wheels are more or less level, as is the bottom of the deck and the posts are welded on in this pic.
10 Chassis levelled.jpg
Sometimes strange things go through your mind when you have a garage full of bike parts you need to get rid of while you are working on an unrelated project. I thought of this after I had removed the wheel/motor. The seat would have to be above the batteries and..... No!! Stop that! Don't even think about it!!! ;-) ;-) ;-)
11 ....... NO!.jpg

Yesterday evening I made a lot of noise for a couple of hours cleaning things up enough to figure out which welds need touching up (today's job after I harvest more tomatoes) and I still need to figure out a few details like where I'm going to put the mower's throttle control (Lee had it wedged in the plate but I'm not sure I like that)


BTW: I figured out how to mount the electronics and gave Lee the drawing for the box that the controls will go in a couple of days ago so I should have that soon (I'll use a smaller box that I already have for the receivers).

Lee always intended to add some sort of safety switch but never got around to doing any more than unplugging the batteries when it wasn't in use. I've ordered a battery disconnect switch (if it doesn't arrive in time I'll install it in the spring) and we have figured out how to use a relay controlled by the receiver to kill the motor's ignition from a switch on the radio, which should also kill it when the receiver is not in contact with the radio and when the batteries are switched off (the relays definitely won't get here in time).
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Mr. Honda ('83 GL1100/Dnepr) summer New Engine Thread
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Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Re: Refurbing an R/C mower

#10

Post by Whiskerfish »

Sidecar Bob wrote: Wed Sep 09, 2020 12:51 pm Before anyone comments on my welding I'd like to say that I am pretty good at grinding ;-)SNIP

Aren't you supposed to ask before using someone else's quote ??? lolol lolol lolol lolol lolol lolol
"Agreement is not a requirement for Respect" CDR Michael Smith USN (Ret) 2017
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!

Psst. oh and by the way CHANGE YOUR BELTS!!!!
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Re: Refurbing an R/C mower

#11

Post by Sidecar Bob »

Someone else said that? I was just referencing the old welder's adage that says "you are either a welder or a grinder"....
Mr. Honda ('83 GL1100/Dnepr) summer New Engine Thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Re: Refurbing an R/C mower

#12

Post by Whiskerfish »

Yea I am a hack welder but a pretty decent grinder anim-cheers1 anim-cheers1 anim-cheers1 anim-cheers1
"Agreement is not a requirement for Respect" CDR Michael Smith USN (Ret) 2017
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!

Psst. oh and by the way CHANGE YOUR BELTS!!!!
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Sidecar Bob
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Re: Refurbing an R/C mower

#13

Post by Sidecar Bob »

BTW: The welding (& grinding) is finished and it is in primer now.
Mr. Honda ('83 GL1100/Dnepr) summer New Engine Thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Re: Refurbing an R/C mower

#14

Post by Sidecar Bob »

I don't know what happened. I wiped it down to get it ready for paint and when I came back to the garage after break it was completely rust
12 Primer.jpg
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Mr. Honda ('83 GL1100/Dnepr) summer New Engine Thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Sidecar Bob
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Re: Refurbing an R/C mower

#15

Post by Sidecar Bob »

.... coloured (oxide primer) ;-)

And 2 days later it has turned red
13 Red!!!.jpg
The power switch came so now I'm waiting for Lee to give me the box.
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Mr. Honda ('83 GL1100/Dnepr) summer New Engine Thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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