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. 


The axle is itself is from BMI Karts and was the cheapest axle I can find. The axle is 36" long with a keyway running along the shaft. Half of the keyway runs through the axle up to the midpoint of the axle. Then the other half of the keyway is located on the opposite side from the first keyway. The link to the axle is http://www.bmikarts.com/1-Steel-Live-Axle_p_517.html and it was only $22. The ends were also threaded.



Below is an image of the sprocket that I will be using for the axle. It's a Tuck & Run 65 tooth, #35 sprocket. The sprocket is from BMI Karts and the link to the sprocket is http://www.bmikarts.com/WMS-Tuck-Run-35-Split-Full-Tooth-Sprocket-_p_1420.html. The price isn't bad at all, just $13.

The sprocket will be held in place by a sprocket hub that I also got from BMI Karts. Below is a picture of the sprocket hub and they go for about $15. The link to the sprocket hub is http://www.bmikarts.com/Unihub--Sprocket-Hub-_p_1376.html.


The holes on the sprocket line up perfectly to the holes on the sprocket hub. And they are both secured together by bolts that I got from Harbor Freight.




The sprocket hub has a 1" bore with a 1/4" keyway and two set screws.

Another part I got that goes on the axle is the brake kit. The brake kit includes a disk, caliper, and a mount for the caliper. The three parts can be seen below.



The brake disk has a 1" bore with a 1/4" keyway and two set screws. The kit was from Go Power Sports and the link to the kit is http://www.gopowersports.com/go-kart-mechanical-brake-disc-kit/. This kit goes for $59.

I also got wheels from BMI Karts. To stay within the budget as much as I can, I choose the most cheapest wheel and tire kit. The tire in these kits were pretty flat from shipping and packing so it was advised on the product page that there may be some difficulties in mounting the tires onto the wheels. Before purchasing these wheels, I spoke to Small Engine Rescue, they're a local company who works on small engines and have experience with go karts, to see if they can mount these deformed tires onto the wheels. They said yes and I went ahead and ordered the wheel and tire combo. The link to the kit is http://www.bmikarts.com/16-x-8-7-Knobby-Tire-Rim-1-Bore_p_1517.html and it was about $29 per kit. Below are images of the tire and wheels when they came in.




As you can see, the tire was pretty deformed. The people of Small Engine Rescue were surprised by how smushed the tires were. But they got the job done. They said it took quite a while to get the tires on. They tried keeping the tires in the sun to help them soften but that didn't really work. So they used a inner tube to get the tires to fit onto the rims. Then they left it like that in the sun to make the tires regain their shape. After some time, they then removed the inner tubes and remounted the tire onto the wheel. Their final work is shown below and the wheels are compared in sized to the original Power Wheels wheels.




I also order bearing flangettes and hangers from BMI Karts as well. Below are images of the flangettes and hangers.


I got the bearings from here at Boca Bearings. They're 1" bore bearings with two set screws. They fit perfect in the flangettes. 






After assembling the bearings into the flangettes and the hanger, the final assembly is seen below.


I also got a couple other miscellaneous items like nuts, bolts, keys, and collars.



The next step was then to strip down the rear end of the Dune Racer and remove the original motor and drive system. I actually did this first before ordering some of the parts such as the wheels. I first removed the plastic coverings in the back to expose the two small motors.


I then went ahead and began to remove the plastic wheels from the Power Wheels. I did this by removing the axle end cap. Underneath that cap was another cap held in with a screw that went through the axle. Once this was removed, the wheels were easily removed. Pictures of this process is shown below.




I then started to remove the small motors, the plastic pieces, and the drive/throttle system of the Power Wheels.






The final result after removing everything is shown below.



So now I went ahead and assembled the axle with all the components (bearings, sprocket, brake disk, etc) and started to visualize how I'm going to attach the axle to the existing frame. I also attached the wheels to where the outside of the tires are flush with the ends of the shaft since the width limit is 36 inches and the axle is 36 inches long.


I used cardboard that I found laying around to create a mock up plate to better see how much space I have to place the motor and the batteries.




It was then that I realized that I may not have enough room to place all the batteries and the motor on the back. So I decided that I needed to extend the rear end somehow. I found an old piece of metal in my backyard that was part of some bed frame set and decided to use it. It had dimensions  of 1.25" x 1.25", so it was slightly bigger than the existing frame square tubing which was 1" x 1". The ends had indentation where they were cut off  by John at Small Engine Rescue to just have the smooth part of the metal tubing. Some rust was present but it was in fairly good shape for metal just laying around in the backyard.


For this next part of the project, I had some help from Small Engine Rescue to do the cutting and the welding that would be required to create the extension for the frame. The existing frame had 8" of metal at the back end. 15" of the 1.25" x 1.25" tubing was cut for each side to extend the frame by 7" to provide more room for the batteries, motor, and some kind of mounting for the caliper. The new square tubing fit easily over the existing frame tubing.






I had the extra tubing pressed towards the outside of the frame. Once I had both sides secured, I went ahead and measured the distance between the square tubes so John from Small Engine Rescue can cut the pieces to fit between the square tubing. Once that was done, John took care of the necessary welding and cutting to fabricate the extension for the Power Wheels. The final result of his cutting and welding is shown below.




He did an awesome job on the welding and painting and gave the new extension a nice clean look. You can check out their website at 

http://www.smallenginerescue.com/

I just have to clean up the axle to make it look more clean. I was originally going to have the bearing hangers welded to the frame like these guys did in this video at 15:00
But John suggested we bolt it on to be able to remove the hangers for any repairs or to move it around on the frame if necessary. So the hangers had two extra holes drilled into it and were then bolted on the inside of the frame to provide more clearance between the tires and the sprocket and brake disk. He also and went ahead and cut a nice piece of diamond plating to be used as the plate for the motor and batteries.



Now the next step for me to do is now to locate where I will drill holes into the plate to bolt down the motor and maybe some angle iron to create a firm seat for the batteries to be placed into. John suggested to use some eyelet bolts/screws to hold the batteries in place and use a strap to hold down the batteries and tie it down with the eyelets. So I'm currently deciding which way to go with. In the meantime, I decided that I needed to resolve the motor sprocket issue.

The MY1020 motor originally had a 8mm 05T sprocket with a double D bore with an OD of about 1.25". So I searched everywhere online to find a #35 motor sprocket with a double D bore that would fit the motor shaft.



But I found no #35 sprocket with a double D bore. I've read on some forums people have welded a #35 sprocket onto the motor shaft. But I would want to be able to remove the sprocket easily if I wanted to change out sprocket ratios or for maintenance or for any other reason. So I decided that maybe I should get a regular type B #35 sprocket and bore it to fit over the motor shaft until the sprocket's shaft is over the flats of the motor and drill two set screws that will lock onto the flats of the motor's shaft.

I went to my school to speak with Fred, a machinist at Florida Atlantic University in the department of Ocean and Mechanical Engineering, about what I should do. One of his suggestions was to bore out a type A sprocket to a inner diameter that will be large enough to place an insert inside of it that will have a double D bore inside of it. The insert would be created from a water jet at school. I was concerned that the insert may rotate within the bored out sprocket. So I thought maybe a square insert might resolve the possibility of this happening but it could be complicated in cutting a perfect square hole into sprocket. Also there's the possibility that the insert may not fit tight enough to hold it together with the sprocket during operation. Below is a picture I found online showing the different types of sprockets.


So in the end I decided to bore out a type B sprocket and drill two set screws into it. I found some sprockets from McMaster-Carr that had bores that were smaller than the motor's shaft. I bought two sprockets and with different numbers of teeth. I bought two just in case one gets messed up and to have a spare. The links to the sprockets that I ordered are below.



Below is an image of the 9 tooth sprocket. This sprocket was chosen because of its similar OD to the original sprocket on the motor.


Once the sprockets came here at Boca Bearings, I then took the sprockets to the machine shop at FAU to get them bored out and have set screws drilled into them. Fred from the machine shop helped me a lot in getting these sprockets done and he made it look easy. We first got the sprockets placed onto the lathe to bore out the hole a little more to fit over the motor's shaft.


I didn't get to take much pictures during the process since I was focusing more on the process. The sprockets were bored out to about 0.464". I can't really remember the size of the drill that is seen in the picture above but it gave the sprockets a nice bore size that fits quite easily over the motor's shaft. After the sprockets were bored out, we then put the sprockets on the mill to first drill holes into them for the set screws.  Once the proper holes sizes were drilled, we then tapped threads into the newly drilled holes. In the end we got what is shown below.


The set screws were placed on opposite sides of each other because of where the flats are located on the motor's shaft. The only concerned I have was that the 9 tooth sprocket may not hold up long enough because that sprocket wasn't designed to be bored out any larger than its stock bore size. But we're going to test it and see how it holds up.

Fred gave me a couple of set screws to use with these sprockets. Below I have a picture of them slightly threaded into the holes.


The set screws are to lock onto the flats of the motor shaft seen below.


These flats are different from the flats where the original sprocket mounted on. These flats are larger and were meant for a wrench to hold the shaft while the nut is being tightened onto the threads. Below are images of how the sprocket looks like mounted on the motor's shaft.



I'm not sure how these sprockets will hold up during the actual race but I hope they do hold up. My only concern is what if the sprockets slide on the shaft because the only thing really holding the sprocket in place are the set screws. I worry that the screws may slide around the flats. But I hope not. I also installed the nut but couldn't really get it super tight since the motor shaft eventually spins when tightening the nut. I could only really use one of the sprockets, the 9 tooth one, since the other sprocket had its set screws placed further away from the teeth. This caused the nut to not be able to be threaded on since there wasn't much threads coming out from the bore of the sprocket. But I will just have to wait and see how they perform. One thing I could do is not bore them out completely and leave some of the original bore size to act as a seat but that could be difficult to accomplish since the sprocket is mounted onto the lathe where the begins from the toothed side.

So now the next step is to place the motor, batteries, and the controller on the diamond plating and bolt them down. I was planning on including all that in this post but it's been a while since I have posted any updates. After bolting the parts, I will then work on the steering. I have already ordered parts for the steering system. I will cover that in the next post and hope to have a video of the progress so far. Thanks for reading!

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