Go Kart #1

[jrbrtsn]

This is the first entry of my build log for go kart #1. Here I am with my wife Kirsten getting some basic dimensions. I'm planning to implement a 1+1 seating configuration, where a removable seat ahead of the driver can be used for a passenger. Steering will be accomplished using levers on the left and right, as was done on the 1984 Mini Baja entry I worked on. I'm pretty sure that I'm going to implement a 4-link suspension for both front and rear.

 

[Poboy kartman]

Uh huh...I think this just a cover up for an embarrassing photo that accidentally got posted on Facebook!

 

[chancer]

Sounds heavy Is that 6.5hp gonna do it?

 

[jrbrtsn]

I'll be using a torque converter + jackshaft for more reduction. According to my calculations, it should climb a 40% grade with 700 lb gross weight. Top speed on flat ground should be 32 mph.

 

[landuse]

I would go ahead and use the 6.5HP engine and see if it works for you. You can always upgrade afterwards if you need to

 

[jrbrtsn]

I would go ahead and use the 6.5HP engine and see if it works for you. You can always upgrade afterwards if you need to

That was my plan. Since this is a fun kart, I'm not very concerned about top speed. I have a Honda CRF450x to ride if I want to go scary-fast off road

 

[jrbrtsn]

Some Quick and Dirty Analysis

Given my choice of engine, torque converter, and rear tire size, it's time to do a little analysis. My main goal is to climb a 40% grade with 700 lb GVW (driver + passenger + kart). Given the Predator 212 torque specs, and the 30 series TAV specs, it will be necessary to use a jack shaft to achieve sufficient reduction. Highlights of the analysis are:

• Thrust required to climb 40% grade = 260 lbf
• Total drive train reduction to climb 40% grade = 24:1
• Velocity at 260 lbf thrust = 5.6 mph
• Velocity at max engine speed (governed) = 25 mph

 

[Kelly Wood]

Jokingly: I'm not sure I've seen that much math just to have fun...in oh... 30 years.

To our viewing audience: This math is about to get more interesting. Sid will show up and I'll just go sit in the corner with some crayons.

 

[jrbrtsn]

Math is fun!

Jokingly: I'm not sure I've seen that much math just to have fun...in oh... 30 years.

To our viewing audience: This math is about to get more interesting. Sid will show up and I'll just go sit in the corner with some crayons.

 

[Kelly Wood]

Or not...

and if, goatherder: (it's good fun ok?)

1. Drag of toe in/toe out
2. Tire pressure/drag
3. Actual HP to the ground vs hp at the shaft.
4. Air pressure/humidity vs actual engine performance (predators aren't all that sweet anyway)
5.. How much does gas weigh? 7 or so lbs per gal
6. What did you eat for lunch?
7. I didn't see how much the entire end product weighed... perhaps I missed it. You look as tall as me. How much do you & the wiffy weigh?

Subtract now? SID?

 

[Poboy kartman]

. How much do the wiffy weigh?

Subtract now? SID?

That's wifey....and Classified Top Secret! BTW: the formula for wife weight calculation is admitted weight + 20%.

 

[jrbrtsn]

Weight

Kelly,

If you look at the worksheets, you'll see I assumed a gross vehicle weight of 700 lb. That's pretty conservative, even with my fat arse in the driver's seat.

Given the amount of drivetrain reduction, top speed is likely limited by the engine's governor, not power output. I doubt it takes 6.5 hp to push a go kart at 25 mph on flat ground, even with some tire scrub, rolling resistance, wind resistance, etc.

Or not...

and if, goatherder: (it's good fun ok?)

1. Drag of toe in/toe out
2. Tire pressure/drag
3. Actual HP to the ground vs hp at the shaft.
4. Air pressure/humidity vs actual engine performance (predators aren't all that sweet anyway)
5.. How much does gas weigh? 7 or so lbs per gal
6. What did you eat for lunch?
7. I didn't see how much the entire end product weighed... perhaps I missed it. You look as tall as me. How much do you & the wiffy weigh?

Subtract now? SID?

---------- Post added at 09:46 AM ---------- Previous post was at 09:35 AM ----------

Gross vehicle weight of 700 lb breaks down into:
230 lb (me)
140 lb (wifey)
330 lb (go kart)

 

[jrbrtsn]

Parts Received, Scaled Drawing

Today I received the bulk of the parts for this project , and Friday I'll get a couple of sticks of tubing so I can get some practice shaping and welding before I commence work on the frame.

Last night I made a scaled drawing, though it only shows the belt-line frame tube. Does anyone have advice on a typical turning radius for a fun kart? I pulled 10' out of thin air.

 

[kiles2001]

Sweet set up...

Looks like a sweet set up, what welder and pipe bender are you using? where did you get your parts? I want to build one just never had the time but I think I can squeeze it in on the weekends. please keep us posted with your build and I know its asking a lot but please post lots of pics, I am contemplating picking up a JD2 Model 32 bender but I am trying to figure out what tubing die size to get. I was thinking a 1" die to start and that should suffice to build a kart for starters. any suggestions and advice would be great. thank you

 

[jrbrtsn]

Welder: I have a 225 amp AC/DC stick welder, and a 190 amp Mig welder, both Hobarts. The Mig welder is great for go karts, but the stick welder is needed for thicker metal like farm equipment.

Bender: I have a JD2 model 32 on order with 1.5" and 1.0" dies. If you need to pick only one die, I'd go with 1.0". Make sure the radius will work with the tubing wall thickness you plan to use.

Parts: I got the engine from Harbor Freight http://www.harborfreight.com/65-hp-212cc-ohv-horizontal-shaft-gas-engine-epa-60363.html, most of the other parts from GoPowerSports (they have a nice live-axle kit) http://www.gopowersports.com/, with a few sourced from BMI Karts http://www.bmikarts.com/

Other advice? Get busy building it! Keep a build log on this forum!

 

[Poboy kartman]

Unfortunately, I can't read your dimensions on your pics.

But here's what I want you to consider at this point...

Race karts (especially track karts) are pretty much almost square....(meaning they are about as wide as they are long).
.. Now...it looks like you have somewhere around 4' for a wheelbase width wise.(from what little I can see from the pics)....

I can't tell what you plan for the wheelbase the other way. So here's my suggestion: I know you need length for a tandem rider set-up...but to be able to turn more easily...keep in mind that the wheels don't necessarily have to be at the ends of the kart...but can be moved closer together for a better turning radius....(especially at the front...the rear starts getting into weight issues with the engine behind the axle) ...

Something to think about...

EDIT: My bad....my phone wouldn't load the thumbnails for some reason....I was able to get it to and saw the dimensions..." Dear mudder fadder disregard this letter! " Sooo....Since that was useless drivel, here's something that's not....Check out the castor, camber, and Ackermann thread in the FAQ to help set up your front end.

Carry on...

 

[jrbrtsn]

Finished the rear engine/drive train frame

I finally got around to cutting some metal on this kart. This is the rear frame which ties the engine, drivetrain, and rear axle together. It will be attached to the rest of the kart via a 4-link suspension. I used Fabroman's (I think) idea about the aluminum spacers floating in the engine mount tubes to keep the engine mounting lightweight.

 

[jrbrtsn]

Sprocket Speed Holes

The final drive sprocket I bought was solid plate steel, and weight a ton - so I cut some speed holes into it

 

[landuse]

Awesome work! The sprocket must be less than half the weight now

 

[bob58o]

Kelly,

If you look at the worksheets, you'll see I assumed a gross vehicle weight of 700 lb. That's pretty conservative, even with my fat arse in the driver's seat.

Given the amount of drivetrain reduction, top speed is likely limited by the engine's governor, not power output. I doubt it takes 6.5 hp to push a go kart at 25 mph on flat ground, even with some tire scrub, rolling resistance, wind resistance, etc.



---------- Post added at 09:46 AM ---------- Previous post was at 09:35 AM ----------

Gross vehicle weight of 700 lb breaks down into:
230 lb (me)
140 lb (wifey)
330 lb (go kart)

My buggy is probably similar weight. With stage 1 modded 6.5 HP engine, 16" wheels, TC, 10T, 60T....
With me alone (160 lbs) engine maxes out around 4000 rpm 35 mph
With me plus my nephew (120 lbs??) engine maxes near 3850 rpm.

Based off $10 hour meter / tach.
You should certainly reach governed limit with your jack shaft reduction

Brand new to this stuff but I saw the math (love it) and thought I'd chime as I just put a 212 on a 300+ lb buggy