Novice 6x6 ATV conversion

Tell us about the project you do with the open inverter
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TheSilverBuick
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Novice 6x6 ATV conversion

Post by TheSilverBuick »

My introduction, my name is Randal and I'm starting my adventure into electric power conversion. Some background on me, I'm not an electrical engineer, nor even work in an electric field, I am a mining/exploration geologist. So I'm prone to using wrong terms and mis-understanding concepts but I'm willing to fail and learn.

I've got a decent automotive hobby background and have converted a couple of pre-1980 cars to fuel injection using through hole solder together boards (Megasquirt). I've got well over 100,000 miles on one of them alone. When I started that venture documentary was iffy, but the EFI hardware was figured out, and many parameters were set by modifying INI files. Using plenty of junkyard parts from newer engines and adapting them to older engines was something I had fun doing. Now I want to convert my 1967 Thunderbird to electric, but before I go all in with a car I thought I'd start with an ATV I have collecting dust due to a high maintenance transmission.

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When I started planning this project I was originally looking at a pair of golf cart motors, one for each side. But that would also require a duplication of all the control parts as well. Looking at used/wrecked golf carts, IF I could find two local, they were going to be $600 each. Just getting used motors were $200 each. Then I read about the Toyota MGR unit having an open differential that I could bias power left and right with a simple set of disc brakes. So started pricing them, and seemed to be in the $300-$500 range, but would only require a single controller. And that's how I ended up here.

Pricing out components, I found the local pick-a-part yard charges $50 for inverters! Checking their car stock online they had two Prius's. A 2006 with a Gen2 inverter and a 2015 Prius C, which I thought would be a Gen3 inverter but may actually be a Yaris type. For $130 I brought both them and a small coolant pump home.
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As I've been reading through this forum and wiki I kept my eye out for a MGR unit and on Facebook Marketplace a salvage yard 100 miles away had a couple for $100. So off I went. Originally I was expecting to get a 2012 Lexus RX400H unit, but when they brought it out it was missing the axle shafts (they were in the picture), so they handed me an older 2006 unit in a wet bag :? but the copper contacts and plugs were corrosion free so I took it. It has a 1 year warranty so need to run some tests on it within that time! Now that I had the inverter and MGR in hand I decided to pull out the ATV's gas tank, transmission and engine.
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I think if I cut the ATV's transmission mounting brackets I can slide the MGR forward some and either set the inverter nicely behind it, or more than likely build a battery box behind the MGR and set the inverter on top of it.
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The gas tank was located in the front, I think I can build a battery box for up front, and if decided put the inverter upfront as well.
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So being its my first EV project, I'm trying to keep costs down and learn as much as I can so I'm going to start with a Damien through hole board controller and will pivot to either Johannes' board or to the Yaris(?) inverter if needed. So not counting spare parts, I'm $50 on the inverter, $100 on the MGR, and $25 on purchasing two Damien boards from jnsaff's classified ad.

Until I have the control board assembled and ready for testing, I'll be looking at what disc brakes I can use (motorcycle?), get the MGR bolted in, and start working out the sprocket size that makes sense and how to support it with the brakes.

Anyways, I'll be asking lots of questions! Thanks for the help!
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

Some second hand Damien boards are on their way. Coming from overseas so not sure when they will arrive. In the meantime I've started gathering more hardware for the conversion.

A little background. The 6x6 operates as a skidsteer, it had a transmission with two differential carriers, left and right, which then used two control sticks to apply and unapply bands on the drums to control the speed left and right. Unless it was modified, it was not setup to run one side in reverse with the other forward. Which brings me to the mechanical modifications I'm making. The stock transmission is high maintenance and difficult to get to the adjusters, so I wondered if a conventional open differential could be used with left-right isolated brakes to adjust the left-right wheel speed. Like sand rail/dune buggies often do. Enter the Toyota MGR, with the open differential, so I just need to add a set of brakes to the axle shafts.

Here is a crude drawing of what I am looking at doing. The control sticks will have a large spring pulling them back (like stock), which will apply the brake master cylinders. Mounted low so the stroke is appropriate for the cylinder. Then pushing the control sticks forward will release the brakes. Pushing the sticks forward will engage the throttle on the electric motor. The plan is to use a cable and pulley system so either stick pushed forward will apply throttle. The trick is, it should cut throttle if one stick is pulled back to turn, because as brakes are applied to one side of the differential 2x the power goes to the side without the brakes, so having the throttle reduce at the same time will reduce a sudden acceleration of the other side. If I get it right, each stick will apply 50% throttle input at maximum push.

Roughly sketched in, I didn't have the MGR centered when I took the picture.
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I will need at least an 8" shaft from a centered MGR unit to get to the outer frame rails, ordering an 18" shaft was most economical and ~9" will work fine. I will weld in support brackets on the outer rail with a flange bearing to support the end of the shaft. I am picking the smallest gear available with 10 teeth and if my math is right it'll make peak power around 17-19mph, 30mph at 75% max rpm and 40mph at 100% max rpm. More than plenty scary enough for this type of vehicle. But if I find i want more top end or run the motor at lower rpm (voltage?) there are a lot more gear options with more teeth. I ordered some 1/4" steel circle plate to make flanges to bolt to the MGR and make brake rotor mounts. I'll probably try and make one on my own and pending how that goes I may end up taking it to a fabrication shop to make the precisionly located holes.

The bearings, sprockets and shaft(s).
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My goal of $500, minus battery system is close. I don't know for sure yet what the Damien board fully cost me, and what an outside fabricator for the flanges will run me. But overall not to bad.
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Now waiting for some parts to arrive....
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

While I'm still waiting on the inverter control board (and sorting through if I am capable of getting it to work) some of the hard mechanical parts have been showing up.

I got four 5" circle plates of 1/4" steel, two became flanges for the MGR and 2 became brake rotor mounts. The next couple steps will be cutting out some of the old transmission mounting brackets, moving the MGR unit forward, weld in mounting brackets for the MGR, then make supports for the end bearings. Once that is done I'll make sure the shaft alignment is running true between the bearing and MGR, then weld the circle plates to the shafts.

The sketch I made followed by the hard parts mocked up. At the moment the rotors can be slid left and right. I didn't have the correct metric nuts to properly bolt the rotors to the flanges, so only one side is sort of bolted in and the other just sitting on the bolts.
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The black 10-tooth sprocket will be chained up directly to the center axle where there is currently a chain on a jack shaft (middle chain).
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I have a pair of master cylinders that will each work a brake caliper. I think I have a linkage design sorted out so that the levers can be pushed forward without pulling on the cylinders, but will apply brakes when pulled back. Then using a pulley and cable system on the throttle keep the throttle smoothly applied when one side is mechanically braked.
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Still plenty of time to sort out the electronics!
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Re: Novice 6x6 ATV conversion

Post by Bratitude »

awesome project. love the skid steer, with your proposed "mechanical sudo ABS/LSD" system. should rip with the mgr!
https://bratindustries.net/ leaf motor couplers, adapter plates, custom drive train components
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

A little more mock up. I removed the jackshaft and it seems it's #60 chain and not #50 so I need to get new sprockets. The calipers clear the chain by barely, but enough not to worry about. I will probably mount the MGR where it sits here. Any more forward and it gets into the seat area. I'm not sure why my phone fish-eyes all the pictures. Makes it look like the rotors are waaaay off center, lol.

I will likely make a cross bracket that utilizes the existing side bolt holes on the frame to the vertical mounting holes on the MGR. The brake caliper hoses bolt right to the master cylinders I bought,but come up short connecting them directly to the control sticks.
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So moving the master cylinders back, I'll modify the shafts originally connected to the control sticks to reach the master cylinders now tucked under the seat area.
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The calipers clearing the brakes. Even with vertical chain "slap" it should not hit the calipers. Now just a matter of building the caliper brackets.
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An overview of the setup.
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

While waiting for electrical parts to arrive I've been sorting out the braking and bolting in the MGR.

This will let the levers move forward for throttle and rearwards for braking. I only made one rod to test how it'll work. I may need to move the master cylinders further rearwards and would need longer rods for that. I need to get some brake fluid resistant hose and will have a single brake fluid reservoir.
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Video of how the braking part should work. I needed to get the MGR bolted in place before mounting the master cylinders because I have limited reach with the brake lines. The final version will have a properly mounted return spring that will likely be strong enough to apply some brake pressure when the levers are not held.


Got the MGR mostly bolted in. I need to double check that it is square with the frame then I'll drill holes in the rear bracket through the frame and bolt it down. From here I need to make the shaft end bearing supports and caliper brackets.
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And now the exciting part! Got the blue pill board and BOM in so I can start putting this board together! Arber333 is sending me a resolver exciter board to assemble and I'll need to put together the conditioning circuits for the current sensors. I've got a stack of GM alternators in a shed, so I disassembled one and will try and use it as a simple test AC motor when I have the blue pill board assembled.
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

Assembled the board tonight! I didn't solder the blue pill to the board, I'm going to pick up a socket for it incase I brick or short the blue pill loading in firmware or in event of mis-wiring (or goofing up the current sensor signal...) I'll be able to quickly swap in another chip. I've got a digi-key cart full of parts for arber333's resolver board and the signal filter circuits, but I'm going out of town until the end of the month so the order will have to wait until then.

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Re: Novice 6x6 ATV conversion

Post by RetroZero »

Love the project and posts. Great progress 👌
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

I'm back from vacation now and getting back into making progress on this thing. While I was away I received the resolver exciter board from Arber333 and got most the digikey parts in to assemble it and the components necessary to make the voltage divider(?) for the current sensors. I say most the parts because I ordered the wrong connectors for the exciter board so I've assembled the board with the exception of those connectors. I'm going to bread board the voltage divider(?) first then stick it on a small prototype board.

Also picked up a sizable project box to put the boards into. I have stands for them, but need to go by the hardware store and pick up the necessary screws. It's technically a sealed box, but I'll drill a hole or two with a grommet to pass the wires out and if needed I'll put some goop in with the wires to seal it back up.

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The local salvage yard just got two 2nd gen Prius's in last week. I'm tempted to go grab their batteries for a $180/each without core, but I do not have a way to charge them up and keep them charged up. So I'm reading through arber333's Toyota Gen3 inverter charger thread (viewtopic.php?f=14&t=257&start=60) to see if I can use my Yaris/Prius C inverter as a charger for the batteries from single phase 240v. Or being that they are NiMH batteries also looking to see if there are alternative cost effective chargers/BMS's for them that I could use. Bonus points if I could use my Bolt's J1772 charger... So this is what I'm currently researching, but I think it means I really need to bring myself up to speed on pre-charging and contactors. I think the Prius battery boxes have contactors in them, but need to double check.
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

I'm getting close to getting back to the electronic part of this conversion. With all the interest in the MGR posted up in the last couple weeks I figure I would let the "dust" settle on the confusion programming the STM and tuning then pick up from there. With the recent video's released by Damien and Joannes I'm feeling ready to works on electronics again.

In the meantime I started working on the mechanical side of the conversion again.

I finished up mounting the brake master cylinders and linkage to the control sticks. I need to get some brake fluid resistant hose so I can make a single reservoir for the master cylinders.
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I've welded the flanges to the shaft on one side, and will build the end bearing support that will also support the brake caliper. I still need to get new size 50 chain sprockets, as I found the drive chain from the transmission to axles was a larger size than the chains between the axles.
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

Got stalled a bit as my work load piled up from COVID delays and dealing with some department of motor vehicle issues with two of my old cars, but hoping to get this back on track. Mechanically I still need to fabricate the shaft end bearing support and caliper brackets. Then sort out the throttle cables.

I powered up the blue pill board and I believe I have flashed the Sine firmware onto it following Damien's video instructions. I believe I need the FOC software for the MGR, but I'm going to try and spin a modified alternator as a test first.
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I also popped off the back of the gen3 Prius contactor and pre-charge board to sort out the pins. Testing, the contactors on draw just under a half amp. Would that require an economizer? I didn't run it long or watch the temperature (yet?). Some quick searching imply that 1 amp or more is where concern starts to rise.
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Where I'm currently hung up on the control side is programing the OLMEX wifi board. I believe I need to switch the jumpers from "Flash mode" to "UART mode", but not 100% sure on that. Then I'm struggling with the Arduino IDE software interface. So this is what I'm going to be spending my time reading up on.
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Then as a side note, I purchased a Yaris board from Damien (which has a programmed wifi chip... :twisted: ) So I may finish the assembly on that and stick it in the inverter as time allows, but my primary goal for the ATV is to run it on the Gen2 inverter. But think this is a solid plan B.
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I've been excitedly watching all the MGR interest and work!! BMS and battery charging are going to be my next hurdles after I sort the wifi and some bracket issues.
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Re: Novice 6x6 ATV conversion

Post by bexander »

TheSilverBuick wrote: Tue Nov 17, 2020 7:58 pm Where I'm currently hung up on the control side is programing the OLMEX wifi board. I believe I need to switch the jumpers from "Flash mode" to "UART mode", but not 100% sure on that. Then I'm struggling with the Arduino IDE software interface. So this is what I'm going to be spending my time reading up on.
You should change to Flash-mode once the Olimex is programmed, i.e. set GPIO0 to 1.
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

Yup, got is swapped over yesterday, and confirmed with a ohm meter that the right pads are bridged, but still struggling with flashing the firmware. The green light blinks rapidly when I click the upload or sketch buttons in Adruino IDE, then gives me some python line command errors. I suspect my laptop did something goofy on the software install due to some folder permission issues. I'm going to try and clean that up today and give it another go.

I couldn't get the python code to run or get pyserial to extract/install, but the Adruino IDE steps seem to be working until they don't. I'll post up later tonight. I've screen shot'ed all the setup parameters and errors.
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Re: Novice 6x6 ATV conversion

Post by bexander »

I might have misunderstood so to be clear.
Set jumper to "UART" (GPIO0 to 0) when programming and then jumper to "Flash" (GPIO0 to 1) when trying to connect via WiFi.
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

bexander wrote: Wed Nov 18, 2020 6:45 pm I might have misunderstood so to be clear.
Set jumper to "Flash" (GPIO0 to 1) when programming and then jumper to "UART" (GPIO0 to 0) when trying to connect via WiFi.
This seems backwards from the directions I've read.

I have a the jumpers set to UART mode, connecting with a FTDI USB to serial adapter and the RX/TX wires swapped. The green light on the Olimex blinks when the Adriuno IDE says "Connecting", but turns off otherwise.

viewtopic.php?f=5&t=8&hilit=olimex
arber333 wrote: Mon Nov 04, 2019 1:58 pm I have tried to upload to Olimex ESP8266 your code from https://github.com/jsphuebner/esp8266-web-interface
1. I soldered GPIO0 to 0
2. I opened arduinoi and setup the code.
3. i flashed the code and it went through 100%
4. I resoldered GPIO0 to 1
dima wrote: Sun Dec 23, 2018 2:22 am When you get a brand new ESP8266 you will need to solder GPIO0 to 0 (placing it into UART mode)

ESP8266 has two flash types. Sketch (firmware) and SPIFFS (filesystem)

Sketch starts @ 0x000000
SPIFFS starts @ 0x100000

There are two methods:

Method 1: Hardwired to UART (TX/RX)

!!! Warning !!! 3.3v only, some USB-TTL have 5v.

Solder GPIO0 to 0
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Re: Novice 6x6 ATV conversion

Post by bexander »

TheSilverBuick wrote: Wed Nov 18, 2020 7:13 pm
bexander wrote: Wed Nov 18, 2020 6:45 pm I might have misunderstood so to be clear.
Set jumper to "Flash" (GPIO0 to 1) when programming and then jumper to "UART" (GPIO0 to 0) when trying to connect via WiFi.
This seems backwards from the directions I've read.

I have a the jumpers set to UART mode, connecting with a FTDI USB to serial adapter and the RX/TX wires swapped. The green light on the Olimex blinks when the Adriuno IDE says "Connecting", but turns off otherwise.

viewtopic.php?f=5&t=8&hilit=olimex
arber333 wrote: Mon Nov 04, 2019 1:58 pm I have tried to upload to Olimex ESP8266 your code from https://github.com/jsphuebner/esp8266-web-interface
1. I soldered GPIO0 to 0
2. I opened arduinoi and setup the code.
3. i flashed the code and it went through 100%
4. I resoldered GPIO0 to 1
dima wrote: Sun Dec 23, 2018 2:22 am When you get a brand new ESP8266 you will need to solder GPIO0 to 0 (placing it into UART mode)

ESP8266 has two flash types. Sketch (firmware) and SPIFFS (filesystem)

Sketch starts @ 0x000000
SPIFFS starts @ 0x100000

There are two methods:

Method 1: Hardwired to UART (TX/RX)

!!! Warning !!! 3.3v only, some USB-TTL have 5v.

Solder GPIO0 to 0
Yes, you are correct, I got it mixed up. I'm sorry for that.
I have edited my previous posts to be correct.
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Re: Novice 6x6 ATV conversion

Post by TheSilverBuick »

Dusting this off. A month or so I moved the 6x6 over to the car project side of the yard with the thoughts I'd make more progress on it over there. Where I left off is I need to finish up an axle support, two caliper supports, brake lines then the electrical. Yes it was trying to snow last weekend, and you can see "TheSilverBuick" on the other side of the fence :D
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I've pivoted over to the Yaris inverter from the GenII Prius because the option to use the inverter as a charger. I've got additional motivation to put together the Yaris inverter because I recently got a small Honda Hybrid pack to test with (and possibly move the 6x6 around the yard some!) and will need to charge it. I finally assembled the Yaris replacement board. If it works well, it may end up in my GS450H project I'm starting down the path on, where the Yaris inverter could act as the charger and 12v DC output. I still need to do the board corrections on the voltage dividers.

I'm probably going to get this inverter going charging the battery and attempting to spin the MGR before completing the mechanical completion.
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