A Geek's Go Kart

[kevinthenerd]

Ok, so I think I've decided that I want to build a go kart out of the parts from a riding lawn mower (and others that I find in various locations). Now, I'm a total math and science geek, and I want to do this the right way. I'm not just gonna stuff a bunch of stuff together and hope it works; rather, I'd like to actually design this and make something that'll beat road cars in certain attributes.

My neighbor offered to help, and he'll be supplying the parts and welder. I can't wait to get started.

I think I want to use 2" steel tubing for the frame, and the motor will probably require air plane fuel by the time I get the compression sky high. I haven't decided how I'm going to do it yet, but I think I want to have ground effects, including two wings, an underbelly panel, side skirts, and an active fan that draws air from the bottom of the car. I'm aiming for 2+ g's of lateral acceleration.

I haven't made a decision on the nature of the tires yet, but I'm aiming for something light, wide, and bald. They'll be ridiculously spaced... perhaps with a 6 foot track.


AVOIDING FLAMES AND ANYTHING DISCOURAGING (including sobering punches of reality), I need ideas, suggestions, and CONSTRUCTVE cricisms!!

 

[sillymofo]

All I know is that air planefuel (JP-5)is not as combustible as Hollywood made it out to be. I have personally put out a kerosene torch in it.

 

[ApacheXMD]

be sure to add a couple 2 liter soda bottles of compressed air for that forced induction
oh oh oh! and don't forget the rubbing alcohol!

-patchy

 

[DurocShark]

Search for plans. This site was the first to come up in google: http://www.mxk.com/1ykplans/yk15.htm

 

[woowoo]

Chitty, Chitty, Bang, Bang?

 

[radioouman]

How can you achieve 2 g's of lateral acceleration?

Try aluminum tubing for lightweight.

 

[littleprince]

This is a joke right?
Please be a joke...

 

[kevinthenerd]

Originally posted by: cr4zymofo
All I know is that air plane fuel (JP-5) is not as combustible as Hollywood made it out to be.  I have personally put out a kerosene torch in it.

That's jet fuel. You're sadly mistaken. I'm talking about the kind of fuel used in PISTON-driven airplanes. It has a higher octane rating, giving it a higher resistance to knock and therefore a tolerance to higher temperatures without spontaneously combusting (causing a "backfire"). Therefore, I would be able to compress the air/fuel mixture to a higher pressure without having to worry that the mixture will ignite before it's supposed to.

 

[kevinthenerd]

Originally posted by: radioouman
How can you achieve 2 g's of lateral acceleration?

Try aluminum tubing for lightweight.

Formula 1 cars have done over 4 g's. It's all in how you use the oncoming air to push the car downward.

And yeah... aluminum tubing sounds like the way to go. It's harder to weld, but luckily, I just found somebody today who's willing to hook me up with the use of a welder and some serious lessons on how to do it.

Edit: Formula 1 cars can drive upside down at 100mph. Yeah, I guess 2 g's is a bit much to shoot for, but if I don't reach it, I might at least hit 1.5, which is still insanely good.

 

[kevinthenerd]

Originally posted by: littleprince
This is a joke right?
Please be a joke...

Hrmm... where are the fire fighters to put out that FLAME!?

 

[Eli]

lol..

You're talking about a go-kart here, not a Formula 1 racer..

You'll be lucky if you get 0.5g's if you just throw a frame together with some lawnmower parts....

I highly suggest you hang around in some karting forums. You've got some pretty wild ideas about engines and stuff, and quite frankly they aren't very realistic.

But hey, nobody said that's a bad thing. You gotta learn somehow, eh? Just don't go impaling yourself with any connecting rods when your jet-fuel powered mower engine turns into a pile of molten goo.

 

[kevinthenerd]

Originally posted by: DurocShark
Search for plans. This site was the first to come up in google: http://www.mxk.com/1ykplans/yk15.htm

Hrmm... this has many problems.

1. The frame looks very weak. With the kind of power I'm going to be delivering, I'll need the whole frame to be made up of triangles. Plus, I want a roll cage.

2. Those wheels look like they came off of a wheel barrow. I'll need wider tires for some actual traction.

3. That frame is quite skinny. The relative center of gravity would be too high for serious cornering.

4. The square framing looks like it wouldn't be able to handle the slightest twisting force.

5. That has no suspension, again ruining any chance of going around a corner at any speed while avoiding wheel hop.

6. The brake is only on one wheel. That does give me an idea, however. I want to mount the brakes on the SPRUNG side of the suspension, not the UNSPRUNG like it is usually done. This will allow me to shave off the unsprung weight, giving me a smoother ride and better handling. I'll probably use heavy-duty univeral joints in the suspension, though, to give me extra stopping power.


+++++++++++++++

I guess I'll have to stop calling this a go kart. It's too underpowered to call it a race car, but it's too big and complicated to be in the stereotypical category of "go kart." I guess I'll call it a "race kart." I'm keeping the cost rock bottom, but I'm also managing to make very few compromises in the conception and design. I can't wait to get the whole thing planned and priced.

 

[kevinthenerd]

Originally posted by: ApacheXMD
be sure to add a couple 2 liter soda bottles of compressed air for that forced induction

oh oh oh! and don't forget the rubbing alcohol!



-patchy

The purpose of the aforementioned threads was to possibly uncover better ideas. It worked, too.

1. Instead of using that ghetto* forced induction, I plan instead to mill the heads down to increase the static compression ratio of the motor, giving me constant power without requiring a full tank of air.

2. I've decided against the use of rubbing alcohol. I don't care about engine heat as much as I used to. It'll be cooled in the open air without a whole lot of trouble. That's the only advantage I see to alcohol. The major downside is the lack of power. I can get that from airplane fuel (for PISTON aircraft).

3. Instead of using a ghetto-rigged fan on the bottom of an existing car for ACTIVE ground effects, I've decided instead to play around with PASSIVE ground effects through wings and underbelly design.

* I knew from the start that it was a bad idea, but at the time, I couldn't think of any alternatives.

 

[Eli]

You should know better.

There is no compromise between cost and conception/design. It is expensive to build things and build things right.

If you can weld yourself, you've got a huge advantage, because labor is very significant, but still...

In all honesty, If you're very handy and can weld etc, the engine will probably be one of the most expensive things.

Power does not come cheap. You would be much better off finding a motorcycle engine than trying to build a high compression monster out of a lawnmower engine. I am very serious when I say that the stock internals on a lawnmower engine are a joke, and they will absolutely not last for more than 10 minutes with the kind of stresses you're talking about.

Plus, with a motorcycle engine, you get GEARS! Imgine the possibilities......

 

[kevinthenerd]

Originally posted by: Eli
In all honesty, If you're very handy and can weld etc, the engine will probably be one of the most expensive things.

Power does not come cheap. You would be much better off finding a motorcycle engine than trying to build a high compression monster out of a lawnmower engine. I am very serious when I say that the stock internals on a lawnmower engine are a joke, and they will absolutely not last for more than 10 minutes with the kind of stresses you're talking about.

Plus, with a motorcycle engine, you get GEARS! Imgine the possibilities......

Look, it's not just a motor out of a push mower (little 3hp jobbie). I'm talking about a motor that's STARTING with something like 20hp. It's out of a riding lawn mower, and with the weight I'm talking about, it's more than enough power stock.

 

[kevinthenerd]

Originally posted by: EliPlus, with a motorcycle engine, you get GEARS! Imgine the possibilities......

That might be handy. As it is, I have two major problems to still overcome on paper: transmission and suspension. I've got a very good idea of everything else.

 

[Eli]

Originally posted by: kevinthenerd

Originally posted by: Eli
In all honesty, If you're very handy and can weld etc, the engine will probably be one of the most expensive things.

Power does not come cheap. You would be much better off finding a motorcycle engine than trying to build a high compression monster out of a lawnmower engine. I am very serious when I say that the stock internals on a lawnmower engine are a joke, and they will absolutely not last for more than 10 minutes with the kind of stresses you're talking about.

Plus, with a motorcycle engine, you get GEARS! Imgine the possibilities......

Look, it's not just a motor out of a push mower (little 3hp jobbie). I'm talking about a motor that's STARTING with something like 20hp. It's out of a riding lawn mower, and with the weight I'm talking about, it's more than enough power stock.

What I said still stands. Lawnmower engines are not overengineered like an automobile or even motorcycle engine, if anything they're under. What that means is that, sure, it may make 20HP at 3600RPM, but the engine wasn't designed to be run at 3600RPM. If you run it at 3600RPM or faster, its life will be reduced considerably. If you increase the stress on the engine by, say, raising compression, it will eat its connecting rod and pound the mains to death even faster.

You also have to take into account the riding lawnmower parts you're going to use. They aren't meant to go 20MPH, let alone 45 or 60. Honestly, you're making this out to be much more simple than it is, even though you also realize the complexities.

You would be much better off using a motorcycle engine. You would have gears. With a mower engine, you aren't really going to be able to go very fast because of the 3600RPM practical limit, that is without beefing the engine's internals up, which will be very expensive, since there will not be readily available aftermarket parts for a 20HP vertical shaft lawnmower engine.

Not trying to flame. Just injecting some reality into your plans.

 

[Eli]

Originally posted by: kevinthenerd

Originally posted by: EliPlus, with a motorcycle engine, you get GEARS! Imgine the possibilities......

That might be handy. As it is, I have two major problems to still overcome on paper: transmission and suspension. I've got a very good idea of everything else.

I've been wanting to build a motorcycle powered kart for ages....

It would be orders of magnitude better than any single-gear go-kart.

 

[PowerMac4Ever]

Originally posted by: kevinthenerd

Originally posted by: cr4zymofo
All I know is that air plane fuel (JP-5) is not as combustible as Hollywood made it out to be. I have personally put out a kerosene torch in it.

That's jet fuel. You're sadly mistaken. I'm talking about the kind of fuel used in PISTON-driven airplanes. It has a higher octane rating, giving it a higher resistance to knock and therefore a tolerance to higher temperatures without spontaneously combusting (causing a "backfire"). Therefore, I would be able to compress the air/fuel mixture to a higher pressure without having to worry that the mixture will ignite before it's supposed to.

Ok, you obviously have no idea what misfiring and backfiring are...

 

[kevinthenerd]

Originally posted by: Eli

Originally posted by: kevinthenerd

Originally posted by: EliPlus, with a motorcycle engine, you get GEARS! Imgine the possibilities......

That might be handy. As it is, I have two major problems to still overcome on paper: transmission and suspension. I've got a very good idea of everything else.

I've been wanting to build a motorcycle powered kart for ages....

It would be orders of magnitude better than any single-gear go-kart.

Better than gears, however, would be if I could somehow mount a continuously variable transmission. Perhaps I could just slap a torque converter on or something? I don't know.

 

[kevinthenerd]

Originally posted by: Eli
since there will not be readily available aftermarket parts for a 20HP vertical shaft lawnmower engine.

horizontal shaft

 

[kevinthenerd]

Originally posted by: PowerMac4EverOk, you obviously have no idea what misfiring and backfiring are...

Enlighten me.

 

[PowerMac4Ever]

Originally posted by: kevinthenerd

Originally posted by: PowerMac4EverOk, you obviously have no idea what misfiring and backfiring are...

Enlighten me.

Enlighten yourself smartass

 

[kevinthenerd]

Originally posted by: EliI am very serious when I say that the stock internals on a lawnmower engine are a joke, and they will absolutely not last for more than 10 minutes with the kind of stresses you're talking about.

Well, I don't want to last years. If it lasts a month, it will have been worth the experience. I want to build the kart first, and if the motor breaks, I will have learned from enough mistakes from the first one to make the second try even better.

 

[Eli]

Originally posted by: kevinthenerd

Originally posted by: Eli

Originally posted by: kevinthenerd

Originally posted by: EliPlus, with a motorcycle engine, you get GEARS! Imgine the possibilities......

That might be handy. As it is, I have two major problems to still overcome on paper: transmission and suspension. I've got a very good idea of everything else.

I've been wanting to build a motorcycle powered kart for ages....

It would be orders of magnitude better than any single-gear go-kart.

Better than gears, however, would be if I could somehow mount a continuously variable transmission. Perhaps I could just slap a torque converter on or something? I don't know.

Yeah. There are torque converters designed to handle up to 20HP, made by Comet, the centrifugal clutch maker. I am sure there are "industrial" versions available, or somesuch.