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.

So I went online to search for axles that I can use for this project. I also had to make sure that the axle width will not pass the width limit set by the Power Racing Series, which is 36" wide. On GoPowerSports.com I found a 1" diameter live axle with a length of 36".

http://www.gopowersports.com/axle-36/

This axle comes with a keyway along the entire length of the axle and steps down to a 3/4" diameter at the ends. The ends are 2" long. The price of this axle was about $55.

I found the same axle on Northern Tool at http://www.northerntool.com/shop/tools/product_21285_21285 at a lower price at about $50.

Another axle I found was at BMI Karts and Supplies at http://www.bmikarts.com/1-Steel-Live-Axle_p_517.html. 

                           

This is axle is a much cheaper alternative at less than half the price of the first axle that I mentioned. This axle goes for $24 for a 36" long axle with a diameter of 1". This axle also comes with a 1/4" keyway along the entire length of the axle. This axle doesn't step down at the ends of the axle. So I will need to find wheels that will be able to mount on this type of axle and I will have to figure out how I will keep the wheels in place. I might achieve this by using several lock collars on the axle to hold the different parts that will go onto it. 

For the first axle, I didn't really find wheels with a 3/4" bore and a keyway on websites that sell go kart parts. Instead I found wheel hubs that can be bolted onto the axle and then finally the wheel and tire assembly. I found this to be a little more expensive than just finding a 1" bore wheel with a keyway. An example of a wheel hub I found for the 3/4" ends of the first axle mentioned are found at http://www.bmikarts.com/-Wheel-Hub-with-4-516-Bolts-on-a-2-1316-Circle-34-Bore_p_3057.html This seemed to be cheapest wheel hub I found on BMIKarts.com for about $13.

                                   

This wheel hub would then be paired with a wheel and tire assembly that would match the bolt pattern and bolt sizes. Overall, I believe the cost of this setup would either be the same or more than going with the straight 1" axle with 1" bore wheel and tire assemblies. But a pro to the wheel hub setup would be that you can easily change out different types of wheels and tire assemblies on the axle. But since I am trying to stay within the $500 limit, I will be going with the straight 1" axle for $24.


Wheels and Tires
I found that it was somewhat difficult to find wheels that fit on this axle for a good low price. I did come across some wheel and tire combos for this type of axle and they were somewhat more expensive than I would have imagined. The first wheel and tire assembly I found were on GoPowerSports.com at http://www.gopowersports.com/two-13-500-6-live-axle-assembly-trac-set-of-two/ for $69.

                                      

                                                 

According to the website, they are good for off-road and they generally last a while. The size of the tires are 13/500 - 6. So from what I have looked online, the tires have a diameter of 13 inches with a width of 5 inches if these numbers are in inches and if the 500 really means 5.00. They will then fit onto a 6 inch rim. These wheels are somewhat close to the size of the stock wheels on the Dune Racer, which is about 14.75".

Another set of rear wheels I found were also on GoPowerSports.com. The link to those wheels is http://www.gopowersports.com/live-axle-wheel-assembly-145-70-6-1-bore-set-of-2/ and they go for $79, just $10 more than the previous wheels.

The measurements shown in the description are 145/70-6. From a forum on go karts, http://www.diygokarts.com/vb/showthread.php?t=12187, these numbers translate to tires with a width of about 5.7" and overall diameter of 14". So, these wheel/tire assembly is much closer in size to the existing plastic wheels on the Dune Racer. So this set of wheels will mostly be the way to go for us. These rims also have a 1" bore with a 1/4" keyway which will perfectly onto the 1" live axle.

For a more expensive tire/wheel assembly, they also sell the following wheel http://www.gopowersports.com/rear-wheel-assembly-for-mini-gokart/ for $45 each or $90 for a set.

Back on BMIKarts.com, I found the following setup http://www.bmikarts.com/16-x-8-7-Knobby-Tire-Rim-1-Bore_p_1517.html

The wheel hub has a diameter of 7" and the tire size is 16x8-7. So the tires have a overall diameter of 16", a width of 8", and an inner diameter of 7". According to the description of the tire, they are mishaped because of being bundled when shipped. So it may cause difficulty in mounting the tire onto the rim. They suggest buying an inner tube to make the mounting process easier but that will increase the cost of the setup. The current price for this wheel/tire assembly is about $58, which is cheaper than the wheels and tires from GoPowerSports.com.

BMIKarts.com and GoPowerSports.com also offer an option where you can build your own tire and wheel assembly. On BMIKarts.com, at http://www.bmikarts.com/Build-Your-Own-Tire-Assembly--Small-Tire_p_3700.html?redirect=1&lt_c=1&quickcart=1, it is $33.90 or $67.80 for the same wheel and tire that is shown from the second option from GoPowerSports.com. But this price doesn't include the mounting the tire onto the wheel. But, this could be something fun to do and try out.

Changing the tires to a bigger tire, the Turf Tire with dimensions 15x6.00-6, the cost for a set would be $78.

This setup would provide an overall diameter of 15", which can help to increase the top speed of the Boca Dune Racer. I would just need to learn how to mount the tires onto the wheel hub. I have done a quick search and found many videos on how to mount the tire onto the wheel hub.

Later on during my search for wheels and tires, I found wheel hubs for live axles for about $10 at http://www.bmikarts.com/Lightened-Aluminum-Wheel-Rear-Hub-1-Bore_p_2535.html

These wheel hubs have a keyway that can be used with a live axle and can either use 1/4" or 5/16" bolts on a 2.5" bolt pattern. I also found them in different colors: red, blue, and black. I would like to use them because of their low price but I couldn't really find wheels with a 2.5" bolt pattern. So I decided not to use them. 

Brakes

For brakes, I found many kits from drum brakes to disc brakes to hydraulic brakes. But I will stick to the simple disc brake that I found at http://www.gopowersports.com/go-kart-mechanical-brake-disc-kit-3-pc/ for $59. The cost of the brake kit doesn't go towards the $500 limit.

This brake disc comes with an 1" bore with a 1/4" keyway. This would fit good on any of the axles that I have listed.

Sprockets

I found many sprockets online. The sprocket that comes with the motor is a 8mm 05T sprocket. I couldn't really find much information on it or sprockets that have a 1" bore to be able to mount onto the axle. So I think I'll most likely change out the motor sprocket with a different sprocket that uses a different chain size. It will depend on what sprocket I decide to use on the axle. I will also need to see how the motor's sprocket is attached to it so I can look online for sprockets that bolt onto the motor the same way.

When it comes to sprockets, if I choose a fairly large sprocket for the axle I will gain more torque but will also lose top end speed. Going with a smaller sprocket for the axle will increase my top speed but will lower the torque. Lower torque will give a slower acceleration. So I have to decide how much top speed and torque I want and will have to come to a compromise between the two to obtain a well rounded out modified Power Wheels.

My top speed will depend on what the tracks will look like. There's no point of having a very high top speed if there isn't any straight sections of the track where I can get to that certain top speed. Instead I should focus on torque to have quicker acceleration to be able come out of corners fast. From watching races of the Power Racing Series on YouTube, it seems that the tracks don't have many straightaways. So maybe having a good amount of torque would be ideal but not too much soi I can pick up to a decent speed. So I will need to do some calculations to estimate speeds or I could buy a sprocket and do testing to figure out which sprocket I should go with.

I found this sprocket at http://www.bmikarts.com/-40-Sprocket-45T-with-1-Bore-_p_1412.html

This is a 45 tooth sprocket that uses a #40 chain. The OD of this sprocket is 7-7/16". It has a 1"bore with a keyway and with 2 set screws to be able to clamp onto the axle. This sprocket goes for $28.95.

Another sprocket I found that is similar to the above sprocket is this one at http://www.gopowersports.com/live-axle-sprocket-60t/

This sprocket is 60 tooth sprocket that uses a 41/420/40 chain size with a 1" bore. This sprocket also comes with 2 set screws to lock onto the axle. This sprocket measures out at 9-3/4" for its OD. So this sprocket would give a higher torque than the previous one. This sprocket goes for $25, which is a pretty low price.

I found other sprockets that do not have a 1" bore but instead could be used with a sprocket hub that will attach the sprocket to the axle. The following sprocket comes with a sprocket hub at http://www.bmikarts.com/Heavy-Duty-Sprocket-Hub--41-54T-4-Bolt-Circle_p_4222.html

The good thing about this sprocket is that you can keep the hub and change out the sprocket for either a smaller or larger sprocket. The only thing you would need to make sure is that the other sprocket has the same bolt pattern and size to mount onto the hub. I am assuming this hub has a 1" bore with 1/4" keyway. The bolt patten is on a 4" circle. This hub and sprocket goes for $37.95.

This other sprocket and hub lets you choose between sprockets with different amounts of teeth http://www.gopowersports.com/sprocket-48-60-teeth-41-420-chain/

There are 2 bolt patterns for the sprocket, 2-3/4" and 27/8". You can choose between a 48, 54, and 60 tooth sprocket and the OD range from 8"-10" depending on which sprocket you choose. This setup goes for $31.90.

I found this sprocket at http://www.bmikarts.com/35-Premier-Split-Sprockets-53T-78T-_p_1408.html

At the provided link you can choose how many teeth on the sprocket you would like. They range from 53 to 71 tooth sprockets. So this choice can give you a wide selection and experimentation with different sizes to find the correct gear ratio you desire. I will most likely choose this sprocket because of its flexibility and the prices aren't that bad at all. They range from $14.86 to $15.49, depending which tooth sprocket you decide to get. This sprocket doesn't come with a sprocket hub. So that will need to be purchased separately. The bolt pattern on this sprocket is a 5-1/4" circle which is according to the website is what is considered standard. But the bolt size for the holes isn't listed. 

So the sprocket hub that I will most likely choose for this sprocket is the following sprocket hub http://www.bmikarts.com/Unihub--Sprocket-Hub-_p_1376.html 

This sprocket hub has a 1" bore with a 1/4" keyway. It also has a set screw which will to keep  it locked in place on the axle. This sprocket hub has 5-1/4" bolt circle pattern and the bolt holes are1/4". The price of this sprocket hub is $14.95. So the price of this hub with a sprocket above would come around $30. $30 isn't bad especially with the selection between different sprocket ODs. 

Another sprocket I found that has the same 5-1/4" bolt pattern is the following at http://www.bmikarts.com/WMS-Tuck-Run-35-Split-Full-Tooth-Sprocket-_p_1420.html

This sprocket also uses a #35 chain such as the black sprocket with the 5-1/4" bolt pattern. So this sprocket will work with the same sprocket hub. The price of this sprocket is cheaper than the black one: $13. You can also select different tooth sprockets from 53 to 72 tooth sprockets and the price remains the same for any of the different tooth sprockets. So after reading the prices on this sprocket, I will for sure get this sprocket. I can always change out the sprocket for a larger one if I need more torque or a smaller one to gain a higher top end speed. Another good thing about this sprocket is that is a split design. So I can remove the sprocket without having to remove the axle from the frame.

So that's it for this post. I will select the 1" axle from BMIKarts.com for $24. I will get the mechanical brake disc from GoPowerSports.com. I will get the sprocket hub from BMI Karts as well as the red sprocket. The only thing I am debating right now is what wheels to select. I'm going to look into how to a make a keyway inside of a wheel. If I can learn how to, I may just purchase regular wheels for lawnmowers and cut a keyway myself. Lawnmower wheels are much cheaper than the go kart wheels with the keyway already cut into.

In my next post, I will try to calculate the speed of the Boca Dune Racer and I will cover steering parts for the Boca Dune Racer. For now I am just waiting for the motor kit and batteries to test them. Then I'll order the sprocket, axle, brakes, and then finally the wheels.