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R/C EV 'groundskeeper' project

Posted: Nov 28 2018 5:08pm
by afewskroosloose
Hi there. I am brand new here, this is my first post. If I chose the wrong section of the forums, please feel free to kindly kick me to where I should be. I have a project Im working on (and off). It is a 350-400lb 4wd zero turn all electric all terrain r/c platform built to do yard work, hauling, snow removal, etc...and obviously just for fun and to say I did it. Basically Im hoping it will be a greener, cooler replacement for my riding mower (I did ride the unit during testing and may add a seat?) mixed with an atv and big kids r/c car. The top speed is about 8mph, as I am more focused on pushing power and hill climbing than speed for this application. Telemetry and automatic obstacle detection and some interesting semi-autonomous stuff can be explored down the road (I bought the right controller, I think, if I wanna mess with it), but for now its just a glorified r/c tank that can actually run me over. I look forward to the strange looks from my rural neighbors when they see me rollin.

The idea is to build the base platform, then work out the add on attachments as I have time/the 'build fire' in me/and the funds. I have the base unit first cut built, and did a little on the ground testing with a 48v 18ah SLA pack, though Ill eventually go to lithium chemistry of some sort - 48v 50ah maybe for the traction drive base unit. Each side of the drive is powered by a 650w rated 900w peak bldc trike motor from Golden Motor - heavy and low rpm for easier final reduction and added weight. I picked a pricey Roboteq dual brushless 60v controller, mostly because there arent many dual reversing brushless escs that I know of on the market, and also because of the monitoring, pc connectivity and customization the controller allows, and as mentioned the ability for more advanced features to be incorporated down the road.

The unit has (4) 18inch diameter x 9inch wide rear mower wheels and 1" axles all around. I took a few pics with a yardstick to give an idea of the size - about 44" wide x 38" or so long. The frame is 8" high and the wheels are comparatively large so sans attachments, the unit is invertible just because thats cool. It also gives me decent ground clearance. I wont know if the motors are adequate until I can do some more ground testing, but the Roboteq should be able to handle up to 2kw motor per side if I want to upgrade. There are some 120ish dollar 48v sensored mid drive motors running around ebay in the 1.5kw to 2k range I could try down the road, though at 5k+ rpm vs the 1.1k of the trike motors, Id need another reduction stage and some redesign.

My initial ground test was very promising (its gonna be a brutish fun little toy, I think), but it became apparent pretty quick I had a drive train issue. I underbuilt the final #50 drive chain tensioners on either side and they werent up to the intertial forces of quick reversing and turning, etc. Shouldnt be too hard to fix so thats my next step.

In the meantime, I am working through and researching what options I have for tackling the higher powered attachments. They will have a separate battery from the drivetrain battery - I want the base unit self contained and able to be made somewhat water resistant with the drive battery enclosed inside the main chassis and well protected. As the attachment drives will require significantly more power than the traction drive, I can experiment separately with higher voltage (60, 72, 84, 96) motors, controllers, and battery packs to get to the desired kw outputs with lower amps - bringing the system into the range of lifepo4s and lithium ion safe/pack healthy discharge rates, rather than going to the more volatile and lower cycle life associated with Li-Poly.

(**disclaimer - I am an enthusiast, not an expert, and I welcome any and all input from those with more knowledge than I have - if I am mistaken, please fill me in - I wouldnt be a bit surprised if there were some glaring holes in my plan with the build. ES seems like it is a great place for folks of all stripes and levels to box around cool ideas**)

So I am in the 'design in my mind' stage of brushless motor/controller setups that may be suited for the 1.5kw continuous, 3kw often, and 7-10kw peak power ranges that I am thinking I should shoot for regarding the hungriest attachments like the snow blower and mowing deck (both in the neighborhood of 42"-50"). I may be shooting for unrealistic goals, but Im trying to get to 60-90 minute runtimes. I have hilly 6 acre property to mow, and 100yd+ long driveway to clear out the snow from. 45-60 minutes run time would most likely be adequate in most cases - I can always recharge and take two swipes at it.

**Now we come to the part where Id like to hear some thoughts on recommended setups for the high power systems.**

ESCs - Flier Model/APS HV esc, or two? Anyone know how these would hold up to use at roughly 1/3 of their claimed continuous/peak ratings? Kelly or Golden Motor bldc controllers meant for golf carts and motorcycles, maybe? Would it be hard to interface one of these larger ev controllers so that I had radio control of the throttle?

Motors - APS 80mm outrunner family, single or twin setups? Anyone know if an 80100 could handle 30-60 amps continuous for an hr at 72v with peaks of 100 amps thrown in? I really like the look of the Leopard 8072s and at 130 a pop, thats not too bad. They claim 4kw and high durability, so maybe a twin setup with these? Ive heard mixed reviews about the Revolt motors - but this seems like an application right in their 'wheelhouse'. How about Motoenergy/Golden Motor 3-5-10kw larger motors for traction vehicles? Im thinking this category may be best for duration of runtimes, heat dissipation capability, and overall durability? What about an SSS 56/114 "13kw" inrunner lower kv at high voltage, with entire can clamped in a machined aluminum mount block/heat sink? Obviously Id be introducing the need of a beefy gear reduction before Id be able to belt drive to my primary 'weapons'. Probably the complexity of using an inrunner would outweigh any cooling/efficiency benefits obtained, but I am not sure.

I can handle the mechanics and fabrication, I am just not sure about the power system I should be considering for reliable use at the 45-90 minute duty cycle I would like to get, and the electronics portions arent my strongest suit. Cost is an issue, of course, but I also dont want to cost cut myself into having to 'do it right the 2nd time' if it can be avoided. I will likely be piece mealing the big ticket items.

I cant make any promises on how often I will be updating the build progress - its been a pretty slow go so far, and well life happens. I also do metal art on the side and that takes up some time. Not to mention its tough to justify $500 plus drops on 'toys', sometimes. But...I am getting the 'fire' again and the gears wont stop turning. If I can swing it, I hope to start picking up the components for the first attachment build in the not TOO distant future, and would appreciate any advice, feedback, or discussion on any aspect, and especially help with power system selection.

Sorry for the long rambling opening treatise/salvo, but thats my project and Im stickin to it :D


Re: R/C EV 'groundskeeper' project

Posted: Jan 21 2019 2:31am
by tentman
Hello - Interesting project, very similar to one that has been "in my head" for a long time. I'm stalled on finding suitable reduction units (something around 25 or 40:1) that can be had "off the shelf" with a reasonable chance of obtaining spare parts in the future.

What did you havd in mind for your reductions?

Re: R/C EV 'groundskeeper' project

Posted: Feb 08 2019 5:58am
by afewskroosloose
Hi thanks for the reply. I am using brushless trike motors with custom 2 stage roller chain reduction giving about 10:1 ratio. The brushless motors are low rpm high torque.

Brushless dual drive is a little more complicated than brush drive. For 'off the shelf' all-in-one drive brush motors I would look into higher end/power wheel chair motors.

I am suspect of the durability of integrated gearboxes that come with geared motors - most arent necessarily designed for quickish reversing and shock loads regularly. This may or may not be an actual problem in some cases, but by customizing and over-rating my chain reduction, I maintain control over the beefiness of my drive train and can rest easier than it will hold up, and that sprockets and chain are readily available and easily replaced (unlike the valid concern you expressed that it may be difficult to get replacement gears for integrated gearmotors should they fail - you may have to purchase an entire new unit).

By customizing your drive train, you can also leave yourself some room to try different motors and reduction ratios if designed correctly. If you design around gearmotors that are specific, then find out they arent ideal or up to the task, you may have boxed yourself in and left no room to try another route without significant re-design - just food for thought from someone who has given it MUCH thought lol.

Try here for battle-tested gearmotors: ... _main.html

There are also sweet deals running around ebay now for chinese planetary reduced scooter/trike motors - they may or may not be up to the reversing shock loads I mentioned but they also wont break the bank and might be worth a shot ($80 each and free shipping!?): ... Sw3JdcV~N9

Happy building!

Re: R/C EV 'groundskeeper' project

Posted: Feb 09 2019 8:23pm
by Choppa66
Hi, great project!! Sort of reminds me of a fat tyred hot rod bomb disposal robot!! I'm liking it!! Happy building!! :D :thumb:

Re: R/C EV 'groundskeeper' project

Posted: Feb 10 2019 7:41am
by afewskroosloose
Choppa66 wrote:
Feb 09 2019 8:23pm
Hi, great project!! Sort of reminds me of a fat tyred hot rod bomb disposal robot!! I'm liking it!! Happy building!! :D :thumb:
It should be fun. The wheels are easily removed so that I can swap a track drive in if I decide to build one for more traction...or just cuz tracks are awesome. 8)

Re: R/C EV 'groundskeeper' project

Posted: Feb 10 2019 7:43am
by afewskroosloose
Still looking for some help on motor/controller choices to power the mower deck and snowblower attachments as described in my initial post...maybe Ill ask in the motors area instead if I dont get any responses here. :P