F1/Indy Inspired Kart

[Doc Sprocket]

Looks like a neat project! As you've discovered your wheelbase to be half that of a real car, are you considering building it to be a 1:2 scale model, or are you basically just doing what you want, as far as the other dimensions? Any body plans?

As far as my own opinions on Rack-and-pinion vs direct steering- For anything offroad, a rack is better. Way less sensitive to driver input, makes it much easier to finesse your way thru hairy, low traction situations. Much less direct feedback from the road, too. A rack won't try to jerk the wheel out of your hands every time you hit a bump, and for some of us (offroad), its several bumps a second. Direct steering is ideal for smooth, flat surfaces- Ultimate road feel, lightning response.
Either way, it's your kart, build it for you! And, nice rack! (If I had a nickel for every time I said that... )Seriously- Where'd you source that?
What're the HP and RPM specs for that engine?
Also- I'm interested in your jackshaft setup- You shouldn't need it for reduction, unless you're aiming for a very small axle sprocket. Are you using it to allow you to put the engine/axle in a better location? I ask because one thing that's driving me nuts about my bike-powered project is the fact that I'm trying to keep the powertrain short, but the size and shape of my gearcase will not let me put the engine much higher than the axle, nor can I put the axle forward of the engine without some very serious reengineering. I think i can pull off what I want with a jackshaft (I don't need the reduction) but I was hoping to avoid the extra weight and moving parts. Your thoughts?

EDIT- I just re-read things, and noticed you're NOT using the jackshaft (duh), but feel free to share thoughts...

 

[The_Machine]

I got the rack from desertkarts.com 2 years ago. used it on a 2 seater buggy that I built from the plans I got from theo, although I only used the plans for the front end.

here she is. i stripped her down of parts and hauled her to the scrap yard. good fun was had on it but it was too heavy and wasn't much for performance. kinda like a RZR or a rhino. I did however jump the **** out of it many many times. I even rolled it over at high speed for 2 rolls. other than dirt in my eye everything was perfect.

No more utilitarian. It's all about performance and self imposed over engineering - for the fun of it.

If you shorten the steering arms on the spindle you can decrease the amount of leverage the rack has on your wheels, and hit full steering lock earlier. I plan to have the steering wheel work from lock to lock in 240 degrees - 120 degrees each way. Just like a real race car. By drilling several holes into the steering arms on the spindle you can make your steering ratio adjustable. You only lose steering feel when you have great leverage on your wheels. The steering feel will be very precise.

As for chain geometry and jackshafts. Have you considered a chain tensioner with an idler sprocket? by using a chain tensioner you can increase the amount of sprocket teeth the chain makes contact with and at the same time force the chain away from the case. You can simply use a bolt through an idler sprocket. Or you can do like I did and take a grinder to the case

Of course use an idler sprocket instead of whatever is used here.

Just show me a picture of your dilemma.

The engine is from a Honda Rebel. (CMX250) that's it on my old buggy there. The rebel specs says 18hp and it revs to 8250 rpm. Of course the pipes will be cut down with a high flow air filter and be rejetted, so maybe a few more horses. It hauled that buggy down the road quite fast with 1 person on it. 2 was a little more sluggish. This kart will weigh VERY much less than the buggy, and so will be much much quicker. i believe that buggy weighed somewhere near 600 pounds without any parts on it

 

[newrider3]

Nice, I remember the first build from the old forum.