Chapter 11: Thinking more about pedals.

Posted: November 5, 2009 in Building an Electric Go kart, Vintage Cars
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To this point we’ve made some great progress with our steering assembly, the body, and even the steering wheel itself. With regards to the pedal and crank components, after assembly it didn’t really seem that it would work. The thing is it’s that original idea, of making a simple pedal car, that got me started on this project to begin with. And it’s that thought that really made me revisit the pedal crank just one more time. There is just something really great with the idea that this go kart could sit for twenty years and it could still be a neat toy right out of storage, whereas with an electric motor or even gas it may not stand the test of time would have issues with speed and power, etc.

Our two donated Power Wheels motors with 6v/4amp batteries. With plastic sprockets it's amazing these things last as they do.

Over the past couple of weeks I had two Power Wheels cars donated to the cause and after digging into them and removing the motors I realized that I would have to do a serious amount of retrofitting (drilling, cutting, etc) of our already assembled body to make them work. And even still, the power would in all likelihood not be enough, or at least not make for a very exciting ride, since they were single speed motors with a 6 volt 4 amp. battery source. There are some great resources online (such as ModifiedPowerWheels.com) with tons of docs on hacking these things, but I think going this route would really make this project drag on more than I’d prefer. And I’m not totally convinced it would even work in the end.

I remember catching a commercial on television for the Dyson vacuum cleaner. It was noted that the inventor had gone through a hundred prototypes (maybe it was a million, I don’t remember) before settling on it’s current form.  I’m sure the Wright Brothers didn’t get off the ground on their first attempt either, so with all this in mind I don’t feel too bad for spinning my wheels for a few weeks while trying to figure this all out.

My trusty assistant working diligently as usual.

After raiding the boys’ Halloween candy for some inspiration I thought long and hard about my dilemma. I really have a few issues to address if I want to use the crank; first is the mounting of the sprocket, second is the general alignment of the crank to the rear sprocket and of course the leg room issue for my oldest son. After a couple of bite size Snickers, a Tootsie Roll and some Candy Corn I think I finally came up with a solution for all three problems…not to mention a stomach ache.

First problem to contend with was the sprocket mount. Remember as handy as JB Weld is, it didn’t really cut it when we tried to mount the sprocket with it. The force when it turned the the chain was just a bit too much. To solve this problem I realized I could mount the sprocket onto the crank using a pipe floor flange…the very same thing we used to mount the rear wheels as well as the crank in the frame. This galvanized pipe is really handy stuff, I’ve used it in a variety of places in our project and heck for all I know it may even be a cure for the common cold.

Our sprocket mounted to the pipe flange.

I realized that if I drilled four holes in the sprocket I could mount that to the pipe flange. The flange and sprocket could then slide over the crank where once the ideal position was found I could secure it with nuts on each side plus a cotter pin through the crank to prevent it from spinning when the crank was turned. Genius I tell you! Sheer genius! OK, maybe I’m getting a little carried away, but I did think it was a good idea… then again I also thought JB Weld was a good idea.

To put this plan into action I first bribed my assistant and we drilled the holes. I realized that having four mounting points for the sprocket would also give some flexibility with the alignment issue as well. I could shim one or more of the bolts with washers to get it to lean one way or another.

We spent a bit of time drilling our holes we then mounted it up to the flange. It actually didn’t look half bad. Next I placed it onto the crank… so far so good.

Our sprocket and pipe flange unit mounted to the crank, with a cotter pin drilled through the crank. Second time's a charm right?

Now for our leg room issue. When my older son sat in our kart, and pedaled, he hit his knees on the steering wheel. I realized that as much as raising the height of the wheel helped, I also needed to bring the wheel further away from the dash and closer to the rider. The solution here was simply to add another 2″ spacer into our steering column. It’s not as though this kart will fit them forever, but at least for a bit of time they should all fit right?

If you look at a typical recumbent bicycle the rider is somewhat laid back, with their feet in front, and the steering is either via a crazy “hands at your side” or via a system that is higher than where your knees will be while pedaling. All these measurements and considerations are definitely easier said than done.

I had my son sit down for yet more measurements (at this point I think he’s getting tired of me asking him) and I realized that unlike what I did in Chapter Seven it’s not so much that the steering wheel needs to be higher, but that it should be farther from where his knees will end up. In other words I need to make it closer to the dash, not farther. I also realized that I could make a bit more room for his knees by carving yet another (third one I might add since the I cracked two earlier versions) dash up.

Third pass at a dash with a revised shape to the bottom for more leg room.

I proceeded with this step by removing the steering column and removing our longer 3″ extension and replacing it with 2″, and carving the bottom of our dash with an “S” shape as seen in the shot.

To this point we’ve resolved our leg room issue as well as the sprocket alignment and mounting challenge. Woohoo!

Finally, I can now see a light at the end of the tunnel with some finishing work in the not too distant future. Let’s just hope the light isn’t a train.

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Comments
  1. Ali Bairos says:

    Hi – greatly enjoyed this! Recently came across the Popular Mechanics MGTC pedal car plans that I never built for my kids & now gonna do it for the grand kids. Like your idea of chain drive better than back and forth pedals. BUT on your otherwise great site here I cannot view Chapter 9 – I click on it and Chapter 10 comes up – can you help?

    Thanks and aloha, Ali Bairos, Kealakekua, Hawaii

    • Jas says:

      Thanks for the kind words Ali, and thanks for the tip on the broken link. I’ve fixed it, and if you have any questions let me know. Look forward to hearing about your project.

  2. stewart says:

    pedal cars
    I see where people making pedal cars bend the crank from solid. Now if you get two sets of bicycle cranks and set them up on a single piece of solid rod and grind where the cotter pins go, then the pedal can be set up. Drilling out the threads and sliding threw a suitable rod and weld this in place putting in the pedal tread before welding. when the whole thing is together cut the main axil to make the crankshaft,Just like a car crankshaft but not as heavy. The big ends are where the pedal treads go. There can be three main bearings but I think two would be enough. This should run true to a couple of thou. I will make one and show pictures as time permits. If you have trouble post a comment and I will get back to you.

  3. joe adams says:

    i love building these carts. Wow! They feel great when you are riding them.

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