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

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

Apr 13, 2018

Gerardo Ramos


Reposted from June 20, 2016

 

power wheels

 

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.

 

power wheels

 

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.

 

power wheels

 

In the picture above you can see a bent link that is bolted to the lever. This lever is what squeezes the two brake pads together inside the caliper to clamp on the brake disc. The linkage was fabricated from John at Small Engine Rescue. He heated the tubing/link to be able to bend it to its current shape. Below is a picture of the linkage during the process of its fabrication.

 

power wheels

 

In the picture above, it can be seen that the linkage is entering a sleeve. This sleeve was then welded to the frame. This sleeve is to hold the linkage in place. There is also a spring nearby the sleeve to push the linkage towards the back of the frame. This will then release the brake pads from the brake disc when the linkage isn't pushed forward. Below is a closer shot of the spring and sleeve.

 

power wheels

 

I didn't take more pictures of the progress but below is the complete braking system when it was done.

 

power wheels

 

John added more metal/rod to the previous linkage and welded two sleeves to the frame of the power wheels with the use of some flat metal pieces. Towards the front of the linkage, he bent the linkage upwards and attached a handle grip for someone to grab and push on. Below are some pictures of the braking system with the Power Wheels body installed.

 

power wheels

 

power wheels

 

When it came to testing the braking system, the results were not good. Initially, the braking was somewhat ok. It would take a while but it would eventually stop from a slow speed. But then after some more testing, it seemed like it was beginning to lose more grip with more time. It was also less efficient with heavier drivers due to the increase of momentum when the Power Wheels is moving. Momentum is as follows:

 

Momentum = mass x velocity (p = mV)

 

We actually took the Power Wheels around the building in testing and during this testing the key to hold the brake disc in place fell out without us even knowing. I didn't had any lock collars to hold the key in the brake disc in place. This was why the braking got worse during testing.

 

But after some thinking, we came up with the idea of maybe replacing the linkage system with a cable instead, like a bicycle's braking system. I think that the linkage system isn't really allowing the lever to close all the way. So I adjusted the throw of the lever to be minimal so I won't have to require the linkage to be displaced a large distance. But this did not really fix the problem. I believe that the sleeves that the linkage goes through on the side of the frame is restricting the lever to be able to move freely. I think what the problem is that the lever has a circular path that it follows. But the linkage is only allowed to move in a linear manner through the sleeves. So I feel like this prevents the lever to move within its full range of motion. I'll try to depict this below.

 

power wheels

 

So since the lever is pivoting about a point, it causes it to have a rotational movement around that pivot. So in the middle position, you can see that the y position (vertical position) of the hole of the lever is at its highest. When the lever is pushed to either side, the y position of the hole is at a lower location.

 

So in the diagram below, I am trying to depict the linear motion of the linkage close to the handle.

 

power wheels

 

As you can see, the sleeves only allow the linkage to move linearly to the left and right. So in this setup, the y position of the linkage is restricted from going up (positive) or going down (negative). The linkage and the lever are bolted down together to form one rigid body and because of that, the lever does not move in its full curvilinear path. So one thing I was thinking of is maybe swapping out the whole linkage system with a cable system instead. A cable will be able to be guided through the sleeves without restricting the curvilinear movement of the lever.

 

But after speaking with Jason about the braking and the budget, it was then decided to go with a hydraulic braking system instead of a mechanical brake system. The brakes of this project doesn't go towards the $500 limit for the Power Racing Series. So we went ahead and ordered a hydraulic brake kit from BMI Karts. The link to the brake kit is: http://www.bmikarts.com/1-or-1-14-Cast-Aluminum-Hydraulic-Brake-Kit-_p_583.html

 

It came to Boca Bearings during the writing of this blog. Below is a picture of the entire kit. The kit included a brake disc, brake disc hub, caliper with brake pads, master cylinder, hose, and some DOT 5 brake fluid.

 

power wheels

 

Below is a closeup shot of the master cylinder. This master cylinder has two lines to connect to the two different parts of the caliper assembly. The kit also has an aluminum lever where you can either bolt on a foot pedal or some extended lever of some sort. I'm planning on going for a hand brake so I will need an extended hand lever to bolt on to this short lever.

 

power wheels

 

When ordering, you are given the option to select the thickness of the brake disc/rotor. You have the option to go with 1/8" or 3/16" for the thickness of the rotor. We went with the 3/16" and it is fairly thick as you can see below.

 

power wheels

 

Below is a picture of the brake hub bolted together with the brake disc.

 

power wheels

 

So I will be installing this new brake kit sometime soon after writing some blogs and buying some miscellaneous parts like bolts, collars, and screws.

 

One issue I had before was with the connection between the controller and the batteries. Every time I would make the connection, sparks would be produced and it would sometimes burn up the connectors. There were two occasions where a fire broke out at the connection area. So after a while, it was kind of getting scary to even make the connections. So I did research and came across some anti-spark connectors from Hobby King, http://www.hobbyking.com/hobbyking/store/__61690__XT90_S_Anti_Spark_Connector_2pairs_bag_.html. Below are some pictures of the connectors.

 

power wheels

 

In one packet/order, you get enough connectors for two different connections. I ordered two packets and got enough to make 4 connections with each connection being consisted of using two connectors. Below is a picture of the old connector on the controller that got burnt up.

 

power wheels

 

Below are pictures of the controller with its new connector soldered in place.

 

power wheels

 

power wheels

 

Once I soldered the other connector on the end of the batteries, I went ahead and tested the connection. The results were good. No more sparks. Nothing, it was amazing that these low cost connectors solved the spark issue. If anyone is having issues with sparks being produced when making electrical connections between a controller and batteries, these connectors would be the solution. They helped me and I've seen that they have helped with others that are dealing with the same issue on their e-bike setups.

 

Thanks for reading! I'll be demonstrating some video of the motor being tested with the  chain and axle as well as a video of a test run with one of our guys from Boca Bearings.