Power Wheels Racer Post-Race Update

So I did not really keep up with posting about all that has happened with the car lately but now that we are back and unpacked from Maker Faire I am going to update everyone on what we did. As far as the race goes in Orlando we had a great time up there and all the cars everyone brought were awesome. Here is a short video of the race so that you guys can see all the cars!

Although our car had some speed we actually were not able to finish the race due to burning our speed controller. Basically what happened was the connector that was between the forward and reverse and the speed controller melted from the motor running as long as it had to during the race. As that plug melted the two copper lead got closer and closer together until the shorted the wires running out on the speed controller this short then caused the speed controller to burn up. Here are some pictures of the damage. 

So after we really didn't think we had any chances of racing again. We had no replacement speed controller and after calling a few places in the Orlando, the internet was really the only place that we were going to find a 36V 1000W motor controller, but we didn't have time to wait for shipping. Then after talking to some of the other racers the guys over at Familab told us they may have a spare speed controller at their makerspace and they would let us borrow it if we came by to check out the lab. We took them up on the offer. They have a really cool setup over there with a lounge and hangout area plus some really awesome machines in the back. They had a manual mill and lathe, a CNC mill, one really big 3D printer, and lots more. I would highly recommend giving their lab a look if you are in the Orlando area.  And they let us snag a Kelly Controller 24V 400A speed controller to try to rig up on Sunday morning. We found a wiring diagram from Kelly controllers website and tried to follow it as best we could. We actually had to drive back to their space to grab a few extra parts. There was a main contactor, a few diodes, and a precharge resistor. After we had all we needed we still weren't quite able to get it back up and running that weekend.

Since Maker Faire, we ordered a new speed controller and decided to add a voltmeter and ammeter to the car so the diver might have some idea of what is going on back there. While I was driving I really had no idea that something was wrong until the motor locked up from the leads touching. Here is a link to the one we got below.

https://www.amazon.com/MICTUNING-6-5-100V-Digital-Voltmeter-Multimeter/dp/B01JOUZELG/ref=pd_lpo_469_tr_t_2?ie=UTF8&psc=1&refRID=V1PWGVGCC9264MT29MXX

That shunt that comes with it is basically just a really tight tolerance, low resistance resistor so that the meter can measure the voltage drop across it to get the current. If you want to know more about that resistor look up manganin resistors, they were actually used in determining the standard for the ohm back in the early 1900's. Also, Bryan made an Arduino circuit with a few temperature sensors so we can display the heat at a few different places in the circuit on the dash too. With the temperature, voltage, and current readings we are going to hopefully be able to diagnose any problems the vehicle has in the future faster and catch them before a controller looks like it got left in the oven too long (see picture above).

Power Wheels Racer: Car Updates Before Maker Faire

So as I talked about in the last post there are a few things that needed to be done to the car before it is ready to race up in Orlando. We read over the power wheels racing rules and found some things that we needed to comply with. First thing was the bumpers. We needed bumpers that covered 75% of the vehicles front and rear and covered a 1" space between 4-6" off the ground. So we ordered some aluminium tubing from Mcmaster Carr that already had holes in it and they even gave us the option to buy hardware to join them. After the tubing came in I took the stuff over to FAU and cut it to size on a circular saw and assembled it.

Front Bumper

Rear Bumper

Then we wanted to make sure that it wasn't going to tear up other people's cars while it was on the race track to we opted to just buy some pool noodles and tie then on the bumpers. In order to keep the colors right though we ended up painting them at maker faire. We also added some stickers to the car to make it fit our theme of hitchhikers guide to the galaxy, with the number 42, since it is the answer to everything.

The next update was the steering. We had a pvc steering wheel on there but there were a couple of things about it that weren't as good as they could be. For one the pvc is not real strong and could break. Also the hole through the steering column is not the same as any size screw you can buy at 0.3340" so no matter what bolt went through it there was some play in it. And finally, the steering wheel design made it tough to sit in the car because it took up a lot of space. Really the only way to get your feet inside of that thing is to pull your knees to your chest and if the steering wheel is there there would be no room for your knees. We decided on just making a joystick for the steering. We bought some aluminum rod, a smaller stainless steel rod, and a 10-24 Wingnut then I took the stock to the lathe. Here is what we were left with.

So the small stainless part was machined so that it would barely fit through the hole with about 20 thousands of an inch clearance. Then I 3D printed some couplings that would fit tightly around the shaft of the car and would house the aluminium rod and the wingnut. After we printed those the joystick was assembled and we wrapped it with some bike tape for grip. But when we put the throttle on there the aluminum rod was a little too big and tore up the hall effect sensor in the throttle so we had to order a spare and print a coupling from the shaft to the throttle. This kinda worked out for the better because the longer the joystick the easier it should be to turn. 

In the picture above you can see the forward neutral and reverse switch that Bryan added. He found one that used to be on a golf cart for pretty cheap and we wired it up so that the motor leads from the speed controller ran into it and then to the motor. It basically works as a mechanical switch so that the voltage applied to the motor is either forward or reverse or the leads aren't touching.

The last two things that we added were the kill switch and the fog machine. We 3D printed a coupling to go from the kill switch we bought so that it would be secure on the back of the car. The way it works is when the red key is in there is connection and the vehicle will operate. When the key is removed the speed controller will not allow any voltage to the motor. The fog machine is a dry ice container under the 42 on the front of the car and has a cap where you can add hot water to get the smoke going. Then the pipes run out to the back where the smoke would come out. I do not have any video of the fog machine yet but I will get some to post soon.

Power Wheels Racer

So we are nearing race time for the power wheels racer and trying to get it race ready so that we can get a driver some practice time around the shop before we race it next week. It got a new paint job today and a motor cover but there are some more fixes to be done before it is ready to go.

Updates to be done to be race ready

• Front and rear bumbers
• Kill Switch
• Paint Steering Wheel
• Cut and mount extra PVC piece on steering wheel
• Reverse
• Obtain 1 1/2" wrench to tighten back wheels
• Driver foot rest
• Chain Guard

Power Wheels Racer Part 12: Updates and fixes

Part 12:

After the old brake handle broke off and the weld attaching the steering column came undone, we had to makes some updates to the car. First we decided to design and print a new brake handle. The two main properties we wanted the new one to have was an ergonomic grip and durability. The grip has four slots to fit the drivers fingers for a comfortable grip. To achieve the durability desired the grip was printed out of ABS instead of PLA and was given a 50% infill on the print. Once I put the handle I pulled back on it as hard as I possibly could and it didn't budge. I was even able to lift the front of the car off the ground by pulling back on the handle. Here is a couple images of the handle on the hydraulic break.
                            
However as I designed it the first time the handle did have a couple of flaws. The front end needed to be have a chamfer to clear the hydraulic break when it was resting. Also a small slot needed to be cut out of the inside also. The spacer that goes on the inside of the handle also needed to be shaved down a bit because I forgot to add tolerances to the width of it. I was able to do these with a dremel and angle grinder but since have went back and edited the solidworks file so that the next print will have all the features.

                           

The other thing that is different about this handle is the method in which it fastens to the break. I used 1/4 - 20 low profile screws and heat inserted nuts. The heat inserted nuts can be found on Mcmaster Carr and are inserted into pre-made holes by using a soldering iron. the plastic melts and hardens around the insert so it will stay in place. This is really nice for 3D printed parts because the nut is permanently fixed inside the part. The soldering iron wasn't quite long enough to insert the first heat insert through the hole and I melted a little bit of plastic around the outside. Next time I will have to use a longer skinnier iron. The inserts are pictured below.

                                       
Another change that was made was the throttle set up. Instead of twisting your hand around the handle now the throttle is activated by the driver's thumb. This allows the driver steer a little more comfortably while engaging the throttle. Bryan is also going to use two more 90 degree PVC joints and another shaft to make the steering wheel a rectangle rather than a U shape soon.

In order to fix the weld that broke on the steering column. We are going to fabricate a small 90 degree aluminium bracket to hold in place I also had to angle grind the frame so that it sits flat.

Racing Power Wheels Part 11: Fixing the Caster for Stable Steering

So the next thing to work on was fixing the instability of the steering at high speeds. After doing some online research on steering geometry, I found that the caster plays a very important role in the stability of a vehicle. The current caster of the Power Wheels had negative caster. Negative caster is when the kingpin is leaning forward at the top. Below is a picture of the negative caster on the Power Wheels.

Below is a diagram of positive and negative caster that I found online.

Negative caster causes a vehicle to become unstable at higher speeds while positive caster causes a vehicle to be more stable at higher speeds. But having too much positive caster can cause the Power Wheels car difficult to steer at higher speeds. The current caster on the Power Wheels has a caster of -7 degrees. I measured it by using a level as my vertical axis and measuring the angle of the spindle bracket from the level. From doing some online searching, I found that a good amount of caster is +10 to +15 degrees. These numbers were for gas powered go karts. I found most of this information from diygokarts.com. There I found caster can be generally set to 10 to 15 degrees of positive caster.

Racing Power Wheels Part 10: New Hydraulic Brake System

So the first braking system on the Power Wheels Dune Racer wasn't working really well in stopping the car. So we ordered a new hydraulic braking system that was shown in the last blog post. I got around to installing it on the Power Wheels with some parts of the previous braking system and with the help of Bryan from here. Below is a picture of the original braking system with the metal linkage.

Racing Power Wheels Part 9: Demonstration, Test Run, and Steering Problems

You can see some of the testing that we did in the videos above. In the first video above, we were simply testing the motor with the chain, sprockets, and axle. In the second video, Mihai from Boca Bearings was testing the Power Wheels Boca Dune Racer around the building.

In the first video, you can see that the Power Wheels seem to pick up lots of speed by looking at how fast the wheels were spinning. I can't really remember if we went full throttle but I think we did. After doing some more testing of the motor with the chain and axle, the set screws on the motor sprocket would fling out. So I went to Lowe's to get some Loctite Blue Thread Locker to keep the screws from coming out. Below are some pictures of the Loctite and on the set screws.

Racing Power Wheels Part 8: The Brakes, Problems Encountered, and Sparks Resolved

In this post I will be covering the braking system and the components of the braking system. The braking system can be seen in the picture above. To start things off, I will be talking about the mechanical brake kit that was ordered for this project. A mechanical brake kit was ordered from Go Power Sports and the link to the kit is http://www.gopowersports.com/go-kart-mechanical-brake-disc-kit-9511-9598-th1000/. Below is a stock picture of the kit from the website.

It includes a brake disc that would go onto the axle and lock onto the axle with the use of set screws and a key. It also includes a caliper along with a bracket for the caliper. All three components can be seen installed onto the Power Wheels frame in the first picture above. To activate the brake lever, I decided to use some sort of linkage system based on what I have seen others do on go karts. In the picture above, you can see a L-like bracket where the caliper bracket is bolted to. This L-like bracket is then bolted to the extended frame. With the use of the L bracket, no welding was required to install the brake caliper. Initially, I was planning on getting the caliper bracket welded to the frame but John came up with this design/idea which is much better since now the braking system can be removed easily for any reason.

Below is another shot of the caliper installed on the frame.

Racing Power Wheels Part 7: Setting up the Steering

With the drive axle pretty much done the next thing to work on would be the steering system of the Power Wheels Dune Racer. The above pictures were just some shots during the process of fabricating the steering system. So to start things off, I'll talk about the individual parts of the steering system.

The first part I'll bring up is the spindles along with their brackets. They came together as a complete kit. Below is an image of the kit that I got from BMI Karts.

Racing Power Wheels Part 6: Motor Testing, Controller, and Sparks

So it's been a while since progress has been made on the Power Wheels Dune racer. I've been busy with school and it set me back on this project. Below is a video of some of the progress that was made last time.

      

It's not a really good video. It was mostly composed of videos that I recorded here and there and there were some parts that I didn't get to record.

But below is a picture of where I was at last time with all the electrical parts mounted on some diamond plating that was cut out to fit the back portion of the frame.

In the picture above you can see the 3 12V batteries being held down with some rubber straps. On the back side of the battery pack I have two eye bolts that are supporting the back side of the battery pack. On the front side of the battery pack, which can't be seen in the picture above, I have two L brackets supporting the front side of the battery pack.

You can see where I have mounted the motor controller. I may need to create some kind of barrier of some sort to prevent the wires from going towards the sprocket. Heading towards the front of the Power Wheels, the motor was placed in front of the controller. It took me some trial and error to decide where to place the motor to be able to install the chain.

In the end, I found that maybe I should have move the motor just a little closer to the axle sprocket. The reason for this is because when we installed the chain it was quite difficult. So I had the motor and the axle sprocket not fully bolted down to install the chain. Once installed, I bolted the axle sprocket to the sprocket hub and bolted the motor down. Once this was done, the chain was on pretty tight without any kind of slack. I believe it's too tight. So I may enlarge the mounting holes for the motor to have some play for adjustment and then bolt it down.

Here's another picture of the setup in the back without the plastic Power Wheels body. It is a much clearer picture and you better see the parts on the back.

Racing Power Wheels Part 5: The Rear Axle and Parts

So lately I've been working on the axle and drive system and I have received the motor controller that was ordered from TNC Scooters and now the motor works now. I'm in the processing of trying to return the two motor controllers I got from Monster Scooter Parts so they can test them and see if they are faulty or not.

So I have received the axle, sprocket for the axle, brake disk kit, some collars, keys, a sprocket hub, and the wheels and tires. Below is an image of the axle with its components without the wheels. 

In the picture above, from left to right, you can see a collar, the brake disk, the sprocket hub with the sprocket bolted onto it, and then finally another collar. I'll go into a little more detail on each part that I have received so far for the axle. 

Racing Power Wheels Part 4: Project Update on the Motor Kit and Batteries

           

So more progress has been made with the Boca Dune Racer project. Parts were ordered before and most of the parts have arrived. The first thing to arrive was the motor kit that was ordered from MonsterScooterParts.com. The motor kit was the 36V 1000W MY1020 motor with an universal controller and a hand throttle.

http://www.monsterscooterparts.com/trsc/rec-categories/motor/36-volt-1000-watt-motor-controller-throttle-kit-standard.html

Batteries were also ordered from Monster Scooter Parts, 12V 18Ah sealed lead-acid batteries.

So below is a picture of the controller from Monster Scooter Parts.

Racing Power Wheels Part 3: Selecting Sprocket Size and Calculating Speed

So in the previous post I decided to go with the WMS Tuck and Run #35 Sprokcet from BMIKarts.com. 

BMI Karts lets you have the choice of selecting the sprocket ranging from a 53 to a 75 tooth sprocket. The product description didn't provide the outside diameters for each different tooth sprocket. So I went online to look for a chart that displays the outside diameter for a #35 chain size sprocket for different numbers of teeth. I found this chart online from Azusa Engineering regarding sprocket diameters of #35 chain size sprockets at http://www.azusaeng.com/Sprockets/AzSDno35.pdf.

I also found another website that provided the same information at http://ablproducts.com/35-chain-sprocket.html. So a 53 tooth sprocket would be about 6.5" in diameter and the 75 tooth sprocket would give about a 9.17" diameter. So I can pick a sprocket in between these measurements. So If I decide to go with a 65 tooth sprocket, I'll have a sprocket with a diameter of about 8" (7.978"). I can use this number to help me in determining the speed of the Boca Dune Racer.

The 36V 1000W motor has rated speed of 3000rpm. The sprocket on the shaft of the motor is a 11 tooth 8mm 05T sprocket. I am not sure what the 05T means but I found the diameter of this sprocket at this website https://electricscooterparts.com/sprockets8mmchain.html. They list the OD of this sprocket as 1-1/4".

Racing Power Wheels Part 2: Axle, Rear Wheels, Brakes, and Sprockets

We're currently waiting for the motor and batteries to still arrive here at Boca Bearings.The motor I had first ordered, the 24 Volt 650 Watt motor kit, is currently out of stock at the time until March. So we quickly decided to select another motor kit. We decided to go with the 36V 1000W motor kit. http://www.monsterscooterparts.com/36-volt-1000-watt-motor-controller-throttle-kit-standard.html

This motor kit draws about the same amount of current as the 24V 650W motor kit. From the equation P = I*V, the 36V motor draws about 27.8 amps while the 24V motor was going to draw about 27.1 amps. So I expect similar run times except that the 36V motor will require 3 12V batteries to run it. So this changes the amount of what we have spent into the $500 limit. This kit runs for $179.99 and the batteries we have chosen was the 12V 18Ah batteries http://www.monsterscooterparts.com/gr12vo18amph.html. We had ordered 24V battery packs that was intended for the 24V motor kit. The 24V battery packs go for $109.99. So one and a half of those packs would go for about $165. Only half of the cost of the batteries goes towards the $500 limit. So right now we are currently at $262.50. So that gives us a less amount of money to go towards the rest of the build, $237.50. At the time of ordering, I forget to consider the increase of cost of the batteries. But I'll try to work with what I got.

In the meantime, research on axles was being done. For go karts, there are primarily 2 types of axles: a dead (fixed) axle and a live axle. For this project I will be going with a live axle. A dead axle is an axle where only one rear wheel will be driven by the motor. A live axle is an axle that will go from one rear wheel to the other. A dead axle might be cheaper to make instead of the live axle. For now, I will try to do this project with a live axle and see if I can maintain to be within the $500 budget. 

Axles
So there are many options out there to be able to make a live axle for a go kart or for this modified Power Wheels project. I am planning on just getting rid of the whole rear end of the power wheels and just keep the metal frame. I will keep the plastics that rest on top of the existing motors and figure out how to mount them on again later on. I will need to check underneath the plastics to see if there is any sort of metal connection between the two running square tubing going from the front to the back. If not, then I will need to either weld/bolt on an additional square tubing between the two square tubing running from the front to the back.

Racing Power Wheels Part 1: The Dune Racer and Motor Kit Selection

The next project for Boca Bearings will be to make a regular Power Wheels into a Racing Power Wheels to participate in the Power Racing Series. The Power Racing Series is a series of races where teams race each other with power wheels that they have modified to go much faster than their stock speed. The series also includes an endurance race of 75 minutes. It's a series where people can learn new things and skills and to simply have fun.

For this project, we've searched Craigslist until we've found a Power Wheels that we thought was best for the project. A used Power Wheels was desired since we are going to mostly just keep the plastic covering of the Power Wheels and not use the stock motor or throttle. The Power Wheels we ended up going with is the Power Wheels Dune Racer.