All-Wheel-Drive Go-Kart!

[Smurph]

Got a $20 deal at a local shop for a differential. Not sure what its from. I'm going to go pick it up tomorrow. Its a small name 'cycle and marine' shop. This place might become my new home away from home. haha.

Either way, I'm in line to have two differentials for about $50 if all goes well. That's not too bad.

I'm considering the necessity of the middle differential right now. Taking it out and replacing it with a straight shaft will change the drivetrain's character to give half the power to the front differential to share between the front two wheels, and the same with the back at all times rather than distributing the power between the front and back as necessary. It might save me as much as 10lbs and about $25.

The main concern I have with removing it is: the middle differential is key to the traction management. Replacing it with a bar would mean the avg speed of the front two wheels are always equal to the avg speed of the back two wheels (avg = the front left wheel's speed vs the front right will avg out to the speed of the differential).

In a nutshell, the front wheels will only work together with each other. The back two wheels will also only work with each other. Rather than each wheel working with the other three.

$25 isn't a lot of money, and 10lbs isn't a whole lot of weight. I might just wait to get that diff last, and hook it up with the bar at first, and put that one in there later.

I'm close to obtaining a welder and tearing things up. I'll get pics when that starts.

 

[modelengineer]

On tarmac with kart tyres I don't think you will have a traction problem with kart tyres so the diffs should work perfectly. I still don't know how you're going to do the steering. You'll need CV joints at the front.

 

[Smurph]

On tarmac with kart tyres I don't think you will have a traction problem with kart tyres so the diffs should work perfectly. I still don't know how you're going to do the steering. You'll need CV joints at the front.

What are you missing about how it's going to turn? I've got the steering in that drawing, all but the steering wheel and shaft which will hook to the tie rod in the pic (which will, in practice, be two that function as they should). AWD has been done on a few platforms. All I have to do is look at an awd atv (There's one in my garage). I'm planning on CV joints, but in the drawings I've created, I used u-joints. Mostly because of how much simpler they are to make in Inventor. They do basically the same thing, except the CV joint is a major improvement on the U-joint.

The main practical reason for having the middle differential is that if I try to get on the gas really hard, instead of spinning the wheels, it will transfer the power to the front until the wheels stop spinning (which will all happen very fast).

 

[Kaptain Krunch]

i don't see the point of AWD with a middle diff, it really defeats the purpose. If you get stuck, it will just transfer all the power to the front or the back (whichever has less resistance) and then your back to 2wd.

 

[Smurph]

i don't see the point of AWD with a middle diff, it really defeats the purpose. If you get stuck, it will just transfer all the power to the front or the back (whichever has less resistance) and then your back to 2wd.

Yeah, I've been thinking about it. There doesn't need to be a slip between front and back. I would like to always have 50% power up front to help me out. I think I'll just go to live axle between the drive sprockets.

That ought to create a center axle with 3 sprockets on it. I'll probably mount a brake to that, too. How do you think that will work?

 

[Kaptain Krunch]

sounds good to me, make sure you use a good hydraulic disc brake tho, dont want to skimp on that. What is your power plant going to be? I would definitely do a live axle for your driveshaft, but if you wanted to get fancy you could do a locking diff, which would be complicated but really cool.

 

[Kenny_McCormic]

You'll need CV joints at the front.

Go look at a Jeep front end and count the CV joints for me. With a solid axle all you need is two universal joints.

 

[porsche930dude]

yup you dont want a diff in the middle. as soon as you start going up a hill your front tires will loose traction and youll go nowhere lol

 

[modelengineer]

I just thought you'd use CV joints here instead of uni's, since CV's are much generally much stronger. I suppose on a lightweight, low powered kart it's not much of an issue. (I mean low powered and light weight compared to a car)

 

[Smurph]

I just thought you'd use CV joints here instead of uni's, since CV's are much generally much stronger. I suppose on a lightweight, low powered kart it's not much of an issue. (I mean low powered and light weight compared to a car)

Yeah, I'm going to try to find some CV joints. I'd like to round up a couple ATV cv joints, they're much smaller/lighter... I want used because I don't want to put $300 into a front axle. I can't even afford that for my car. haha.

It's just much easier to draw it up in inventor with u-joints and it still turn. That thing actually fully functions. If you turn the main differential (I'm about to take that out and just put a shaft in, tho), it makes the other differentials turn, which turns the shafts that are hooked in. You can turn the wheels while this happens by dragging the tie rod. That's why I love this program.

 

[Smurph]

I've done some talking with a few other people, one of which was involved in building the twin-engine kart. They said they originally planned on using CV joints, but couldn't in such a small application.

That coupled with the fact stated above that Jeep uses u-joints means I'm going to give this u-joint thing a shot. I'm already estimating that I'm about 40lbs extra with differentials alone.

 

[Kaptain Krunch]

what design program are you using? your makin me wanna check it out haha.

 

[Smurph]

what design program are you using? your makin me wanna check it out haha.

Autodesk Inventor. I'm using the 2008 version. It is an Engineering design program. You might be able to find a student version if you know someone who goes to college. I got it through my college for free.

It's pretty expensive otherwise. Really powerful, though. I've used it a few times to design things to be cut from a CNC machine. This program coupled with an autocad program will write all of your GCode for ya.

 

[Kenny_McCormic]

Inventor takes some serious computer to run, like 2 minute start up time on a dual core computer.

 

[Smurph]

Inventor takes some serious computer to run, like 2 minute start up time on a dual core computer.

I run it on an a7n8x-e Motherboard with an athlon xp 2800+ @2.08ghz, 1gb ram... Old School. Still runs pretty good. It depends a bit on your video card. I have a pretty old radeon 9800 pro

 

[Raywelder]

Inventor takes some serious computer to run, like 2 minute start up time on a dual core computer.

Maybe your computer just sucks

 

[Smurph]

Maybe your computer just sucks

Mine does. haha. I built it when I was like 17 or something.

 

[Smurph]

Inventor 2008

 

[Kenny_McCormic]

Maybe your computer just sucks

Could be, it's a school computer.

 

[freakboy]

when my computer dont work i kick it till it works.