Gruber
HobbyMasters
M.L. Toys
KidsWheels
Gruber
HobbyMasters
M.L. Toys
KidsWheels
HobbyMasters M.L. Toys
Gruber
KidsWheels
Anything that doesn't fit somewhere else & general forum updates
#114010
This may not be completely on-topic as it's technically not a modified power wheel, but recently finding this forum inspired me to get it up and running again so it seemed appropriate to share it here. I started building this back in 1995 and it went though many modifications and enhancements through the late 90s until a mishap destroyed the steering assembly, and combined with waning interest from the kids, it was relegated to the corner of the basement to collect dust.

I'll keep the geek part of this rather brief, but I'm happy to go into more details if there is interest. The design is centered around computer control (drive by wire). Everything is an input to the on-board computer, steering wheel, gas pedal, buttons, etc, and the computer controls the drive motors, steering motor, lights, and dash display. This let me overcome things that frustrated me with earlier attempts at building a kids car such as not letting the kids switch into reverse while driving forward, using powerful motors for good performance off-road while limiting the speed when on the pavement, allowing me to take over control from the kids via radio control when necessary for safety, etc...

Here is is about 1996
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So over my Thanksgiving vacation I decided to dust it off and see how much work it would be to get it up and running. Step 1 was to replace the 60 pounds of old dead lead acid batteries with 5 pounds of Lipo batteries and see if the on-board computer and electronics would still work after sitting for 13 years. To my surprise, the computer and all the electronics came to life without any issues. Then I redesigned and rebuilt the motor and mechanical linkages that steer the front wheels. That was always the weak link in the original car so it was well worth the effort to build something new and much more robust. The last step was to adapt the radio control system to a modern 2.4ghz digital radio control system.

Here we are in 2013 with the car back in action and slightly bigger and older kids.
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A picture of the dash and LCD display that shows speed and other info and lets the parent set things like max allowed speed.
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If you click on the picture below you can see a short video of the car being driven by one of my kids.
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Another short video showing radio control
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And finally a quick shot of the geeky guts
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It's been a blast getting it back to a working state and now I have something to entertain the young relatives that come to visit and I hope others enjoy reading about it. And of course the addictive nature of this that folks here know well. Hmm, wonder how hard it would be to add ultrasonic range finders to prevent collisions, or maybe GPS to geo-fence the car to certain area, it goes on and on .......
#114071
:shock: :shock: :shock: :shock: :shock:

I'll keep the geek part of this rather brief


Please don't! That is unreal. Did you design and build the circuit boards? I don't even want to know what that cost you in adjusted 1996 $'s.

What kind of motors are you using? Where did you get the gearing? What voltage is it running? Where did you get that display screen in 1996! Ok, I'll calm down. Post a link to the memoirs of your build when you get a chance... :roll: :lol:
#114083
Oh man! You should not have posted the geeky guts picture. Is that an encoder? Why 7 Lipos? I would love to hear all the details you remember. I assume this is circuitry is all completely custom?

It looks like you definitely created some fond memories for your children, I am pretty sure that what this site is all about.
#114099
dave wrote:That is awesome and you have way more imagination and skill than I could ever imagine. Glad you brought it back to life


Thanks! You have to keep in mind that I never started this with the intention of it ending up this elaborate. If someone had said why don't you build a car that is computer controlled, that your kids could drive around and control the steering and speed until you need to take over with radio control....I would have probably called them crazy.

It pretty much started the same as most project I've read about on here started. I bought a used power wheels and got it working. But they were only 6V back then and really weak. It actually never occurred to me to hop up a power wheel with more voltage. So this started with an attempt to cram bigger motors into the power wheel. But the body really wasn't easy to modify to mount the bigger motors so I ended up building the new body with the motors controlled by a simple on/off foot switch, and manual steering. But, It immediately became obvious that the bigger motors without any speed control, combined with the weight and size of the car were a real safety issue. So....

...hey I've built this Z80 computer board for other projects, let me throw one in here and use it to control the speed

...speed control is really nice, but I really need brakes so this thing will stop when heading downhill

...wow, I found this cool surplus LCD display wouldn't that make a cool dash

...man I'm tired of chasing this little car so the kids don't drive out into traffic, maybe I can add RC to take over control of the speed

...now that I have RC, wouldn't it be cool to be able to steer too

...hmm, been building lights to mountain bike at night, may as well adapt some of that to give the car headlights and brake lights
#114101
toycrusher wrote:
Please don't! That is unreal. Did you design and build the circuit boards? I don't even want to know what that cost you in adjusted 1996 $'s.

What kind of motors are you using? Where did you get the gearing? What voltage is it running? Where did you get that display screen in 1996! Ok, I'll calm down. Post a link to the memoirs of your build when you get a chance... :roll: :lol:


I really wish I had a "play by play" build write-up for the car, but reviving it gave me a chance to think back on how much everything has changed since the mid 90s. And your questions are pretty insightful in the sense that getting the parts to build a projects such as this was so different than using the Internet to find what you need today. Most all the parts, including the LCD display, came from surplus houses and were pretty cutting edge for the day. I would get on the catalog mailing lists for these places and they would mail me a catalog every month or two. When you saw interesting parts, such as motors, you were smart to buy them because they would be gone pretty quickly. So the parts for this car were collected over time probably starting back as early as 1985. And the cost didn't seem so bad either because surplus parts were generally cheap and purchased over a period of time. Interestingly, some of the surplus houses successfully made the transition to the Internet and are a good source of parts today. These two are still in business today and a lot of my parts came from here.

http://www.hosfelt.com/
http://www.allelectronics.com/

The downside of the surplus house game and other source like going to hamfests, which were very popular in this timeframe, was you ended up with a big collection of what the wife classified as junk. Much of which never got used for anything and much of which I still have today.

The motors are Pittman 30v ball bearing motors and are very high quality and efficient. I actually remember that I paid $7.95 each for them from some surplus house. Later on I stumbled across the retail price and was amazed that they were something like $175 each. They are also low RPM (3000 at 30v) and very high torque, which made the gearing a lot easier. I actually run them at 36V and they never even get warm. I'm sure they could be pushed up the 48V without much issue.

The gearing was a big challenge especially with the tools I had available at the time, which consisted of your typical power tools and hand tools. It's a two-stage arrangement with the first stage being a set of bevel gears that I picked up at some hamfest. The second stage was a chain and a couple of sprockets that I bought from Northern Handyman (now Northern Tool) that had recently opened a store in our area. Sorry to diverge, but when Northern Handyman opened it was like Christmas had come early and I spend hours and hours in that store. It probably took me a week just to figure out how to make the intermediate shaft and bearing to support the big gear / small sprocket combo. The small sprocket has a brass bushing pressed into some random plumbing part, that I drilled out so the bushing fit snugly, that happened to have right size outside diameter to fit inside the sprocket. It rides on a stationary shaft that is a smooth bolt welded to the motor support bracket. Two nuts locked together on the end of the bolt keep the assembly in place. The big gear is attached to the plumbing part with tapped holes and screws from the backside of the gear. The big sprocket is attached to the hub of the wheel with equally creative misuse of parts scrounged from a hardware store. It's really amazing what can be cobbled together from ransom stuff in a hardware store given enough time...
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Yes, I designed and built all the electronics with the exception of the switching power supply that powers the electronics. That was another surplus find that was originally for the Texas Instruments 99/4 computer. It took in 18-24 volts and provided nice clean +5, +12, and -12v output voltages.

I had designed a somewhat general-purpose Z80 computer board earlier because I was tired of designing and building the computer part of different projects over and over again. You have to keep in mind that off the shelf computer boards just didn't exist in this time frame. Because I wanted to turn out a half dozen of these boards for use in various projects, I took the time to design and etch printed circuit boards. That in itself is whole other "adventure", but lets just say I really appreciate that there is free software to do PCB design today, then you submit it online, and about a week later UPS delivers perfect boards. Really beats having tanks of ferric chloride in the garage and drilling a few hundred tiny holes by hand.

Then there is a wire wrapped circuit board that is very specific to the car that provide the interface between the Z80 board and car. It's actually important that this was a wire wrapped board, because it wasn't designed all at once. Every time I decided to add something to the car, I would take this board off and could change and add to the electronics to support the new feature. In the picture below you'll notice there is some space still free on this board, and there are a half dozen inputs and output still free on the Z80 board, so there is still room to add more features even now.

The last major sub-system is the Pulse Width Modulation (PWM) main motor controller. RC models hadn't ventured into electric power in this time frame so you didn't have lots of off the shelf ESC. This is pretty much the same thing as a modern ESC. There is actually another similar motor controller in the front section of the car that drives the motor that steers the front wheels.

Here is an annotated picture of the electronics guts.

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The software development process for this car is also something that's dramatically different than today. I won't go into those details unless someone is particularly interested. Let's just say it a tour into the very early days of personal computers and life before open source software tools.
#114105
DiggityDad wrote:Oh man! You should not have posted the geeky guts picture. Is that an encoder? Why 7 Lipos? I would love to hear all the details you remember. I assume this is circuitry is all completely custom?

It looks like you definitely created some fond memories for your children, I am pretty sure that what this site is all about.


Yes, it's an encoder for measuring the speed of the car. The way it works is the gas pedal input to the computer actually represents "desired speed", not the actual motor power. And the range of the pedal is from 0 mph to X mph, where X is a value the parent can set on the display of the car assuming you know how to "unlock" the parental mode. About 10 times a second the computer compares the desired speed by reading the input from the gas pedal and compares that to the actual speed of the car that is calculated from the encoder. If the actual speed is below the desired speed the computer bumps up the motor power, if the actual speed is above the desired speed the computer lowers the motor power. It pretty much works like your typical car cruise control except the input is the pedal. If you hold the pedal at the 3mph position and drive from pavement to grass, the motor power will adjust so the car stays at 3mph.

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The computer also watches for input from the radio control receiver. If the transmitter is off, there is no signal from the receiver. When the transmitter is on, the computer substitutes the desired speed and steering wheel position from the RC data and ignores the gas pedal and steering inputs from the car. When you turn the RC transmitter back off, the computer once again goes back to using the gas pedal and steering inputs from the car and the kids have control again. This actually leads to some fun pranks you can play on your kids. It's pretty funny to take control with the RC but drive approximately where you think they were going. I've even experienced this myself. It's a weird feeling of you sort of mentally feel like you're in control because the car is going kinda where you intend, but at the same time it's not exactly responding like you expect as you slowly realize you're not actually in control. This is typically followed by "Dad......" in a real annoyed tone. And yes, I confess that sometimes I drive the car around myself. After all, It has to be carefully and fully tested to be sure it's safe before turning it over to the kids.

The battery pack arrangement is less than ideal and is something I would do differently today. It was originally 3 - 12V 24ah lead acid batteries in series. There were 12, 24, and 36V taps off the battery pack. Originally the only thing that ran off 12V was some of the relays, the 24v tap feeds the switching power supply to drive the electronic, and the main motors ran off 36v. The main motors accounted for 95% or more of the power consumed, so drawing a little extra power off the 12 and 24v taps didn't cause too much imbalance in the discharge of the batteries. But, then the original electric steering was added and that ran off 24v, then the headlights and taillights were added and they consumed a lot of 12V. So the imbalanced discharge got a lot worse, but it wasn't a huge problem because the batteries lasted forever. I can't remember the kids every running it down within a day and I charged each 12v battery up independently.

When I rebuilt it, I didn't change the basic arrangement, I just used 2 - 5ah lipo's in parallel to replace each of the original 12V batteries (6 lipo packs). But the newly designed steering ran off 12V, so 12v usage was really high now and the first pack in the series would run down much earlier than the other 2 packs. So I added a 3rd 5ah lipo to the first pack in the series to have 50% more capacity for the 12v part of the pack. Hence the 7 lipo packs now. I've since added a 36v to 12v dc-dc converter to run the steering so the imbalance isn't actually that bad anymore, but I left the extra pack so I don't have to worry about running the headlights a lot. If I were doing this again, I would use a straight 36V battery pack and use DC to DC converters to get all the lower voltages. The way it's setup now, I have to charge all the lipo packs separately and the car is done when the first pack runs down. I do have monitoring on all the cells in all the lipo packs to ensure safety. But this still gives me about 3 hours of continuous runtime on pavement.
#114124
Talk about lost art. Building your own circuit boards and computer is awesome. The only place you can really still find people who know how to do that is in a Chinese high school. :x My programming skills never advanced beyond "Q-Basic"...

I love your speed sensor to control ESC output. How is your rear axle arranged? Is it a solid axle or are the two shafts split? If they are split, do you have a second speed sensor on the other side?

In all, it's amazing what you were able to accomplish here. I would love to see your speed control software available for retrofit to the projects many of us have. We could use an inductive sensor mounted to the gearbox with the sensor wheel attached to the output gear. I'm sure your control circuit board could be shrunk since it's only function would now be the PWM control. Wishful thinking :roll:

I nominate you to the hall of SUPER-UBER-GEEK fame. :ugeek: :ugeek: :ugeek:
#114164
toycrusher wrote:I love your speed sensor to control ESC output. How is your rear axle arranged? Is it a solid axle or are the two shafts split? If they are split, do you have a second speed sensor on the other side?


It's a solid axle but the wheels have their own bearings so they spin freely on the axle. So the motors drive each rear wheel independently. I only have a speed sensor on one side. As long as the wheels are both on the ground and not spinning it seems good enough to just calculate speed from one wheel.

toycrusher wrote:In all, it's amazing what you were able to accomplish here. I would love to see your speed control software available for retrofit to the projects many of us have. We could use an inductive sensor mounted to the gearbox with the sensor wheel attached to the output gear. I'm sure your control circuit board could be shrunk since it's only function would now be the PWM control. Wishful thinking :roll:


It really wouldn't be all that hard to replicate the speed control logic in one of the numerous open source computer boards / software development environments. I'm thinking about something like the Arduino project or the Rasberry PI. They are both general purpose CPU boards that cost less than $50 and with free development software and very active communities on the internet to provide help and examples. I haven't actually used either of these personally, so I can't really say which one is better. But they are very popular with folks building robots and other projects similar to things folks here are building.
#114172
Holy moly. This is AWESOME! I love what you did for the gas pedal, making it an input for a desired speed and then letting the "computer figure out" output to the motors to maintain the speed. As a mechanic, I can say that is very close to what a gas pedals on cars today do. They are an input to a computer but instead of desired speed, the drivetrain systems I am familiar with use "torque requested" based on pedal input.

Oh man, I really, really need to sit down and read all this thoroughly to comprehend it.
#114199
We aren't yet done draining you of information ;) :twisted:

I'm sure I am not the only one here who is extremely interested in seeing your front axle setup and your steering motor. It seems linear actuators have been the best solution most have found but they are typically too weak, too slow, or waaay too expensive. I'd love to see the motor and how you managed to control it.

A more basic question, how fast is it? :D
#114257
I love it. And I totally just designed an independent rear suspension design you could easily convert into it and would add less then 5 pounds and without sacrificing strength. I can draw it out if you're interested.
#114394
toycrusher wrote:I'm sure I am not the only one here who is extremely interested in seeing your front axle setup and your steering motor. It seems linear actuators have been the best solution most have found but they are typically too weak, too slow, or waaay too expensive. I'd love to see the motor and how you managed to control it.


The steering setup is using the same 2" 35lb high speed Firgelli linear actuator that others on this site have used. One of the lessons learned from my original steering motor, is that when someone drives the car into a curb, the forward momentum of the car is transferred to the steering mechanism as the front wheel gets yanked to the side by the curb. That's what destroyed my original home made steering actuator. I think this one is stronger, but to prevent damage, I machined a coupler out of aluminum and nylon that slips if the front wheels take a hard hit. That's the white piece where the coupler links to the steering cross bar. There's a nut inside the bracket that you can't see. The force it takes for it to slip depends on how tight you get nut against a stack of spring loaded lock washers. It seems to work really well.

A custom driver mounted in the front of the car drives the actuator. The computer monitors the feedback pot on the actuator and drive the motor controller such that the output of the actuator feedback pot matches the output of the pot on the car's steering wheel. That's unless an RC signal is being received, in which case it matches the RC signal.

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Here's a picture of one of the front wheel steering knuckles.

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And this goes to a short video of the steering if you click on the image below. I was a little worried that 35lb of force wouldn't be enough, but it seems to be plenty. The speed is fine as well.

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toycrusher wrote:A more basic question, how fast is it? :D


It maxes out at about 7 mph. I picked the gearing for a modest speed, if I changed the gearing it could go faster. But with this gearing it's plenty fast enough for kids and it doesn't pull an excessive amount of power. It also has enough torque for adults to ride....even in grass.
#114397
I love the front setup. I see you brazed the front axle instead of welding it. Were you concerned about it bending or breaking where your spindle and knuckle are attached? I built a custom crossover steering setup for a 4x4 Suzuki Samurai I own. I had no welder available at the time so I brazed my custom shock mounts. To my surprise even after sending the Zuki airborne a couple times :roll: they hadn't bent or broken. I though I was just lucky but maybe brazing is pretty strong after all? :)
#114828
brazing was enough to hold the old crosley engines together
but that was a stamped tin 4cyl engine that only weighed 113lbs...... ready to bolt in and run
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