Very cool!!! 40 mph is MOVIN' that close to the ground. Nice work.....

Is it a 1-speed with a centrifugal clutch?

By the way, nice!

I'll bet on a variable ratio similar to snow machines. Nice work.

Bill
--------------------
"Why not the best?"
Jimmy Carter

It uses a comet torque converter clutch similar to a snow mobile. In effect it's like having an automatic transmisssion. The torque converter is rated for up to 18 hp, and I've actually purchased a 20 hp twin cylinder Honda engine to replace the 13 hp engine that's currently on the cart. But I haven't installed the new engine yet because there will be a lot of other things that I'll need to change out in order to get it to work properly.

One of the things that was a concern during the design stage was finding a rear axle that would be able to put up with the abuse that I knew I would subject it to. There was nothing on the market that I could find that would work well enough in my opinion. So I machined my own axle out of prehardened and ground 416R stainless steel. It's the same steel that is used to make high precision rifle barrels. My friend's shop that I did the work in had a die that was the right size for threading the ends of the axle, but he didn't have a die holder that was large enough to handle the die. So I had to build a die holder in order to use it. And he still has that die holder I built hanging up in his shop.

Maui

www.EngineeringMetallurgy.com

here's where my go kart experience started - modified power wheels
http://www.youtube.com/watch?v=ef4mlT4jY3g (skip to 4:10 for the winch!)
http://www.youtube.com/watch?v=qnChMTLP29U

when my modified power wheels jeep finally broke for the last time (I wasn't in the mood to fix it again), I started looking for something that would suit my then-3-year-old son a bit better. By then the power wheels had been bumped up to 18V with bigger motors and batteries and could sustain about 12mph off road for about 1.5-2 mi. I started looking at making an electric go-kart...but my first try at that didn't work very well (too slow) so I tried gas instead. I "flipped" (in the trading sense) 3 different go karts over a summer looking for something that could be modified to let a 3yo drive. They were all kit karts that had been posted for sale on Craigslist, and which I eventually got rid of the same way. here is one of them - not a very good one, but it sure was fun. definitely not suitable for a 3yo. http://www.youtube.com/watch?v=u4QNw5yKpQc

ivymike, do you live in Texas? Those streets could have been in my son's neighborhood.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

yep

Anywhere near Katy?

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

yeah, a bit north of it. Closer to Barker Cypress & 290. The houses all look the same around here.

As Walt Disney said, "it's a Small World"...

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

Hey,
I've been thinking about a project like that. Thanks for the picture.
Nice "power steering".

I'm in no hurry, so I don't need 40 mph, and I have a 5 and 7.5 HP motors sitting around doing nothing...

STF

Maui...cool!

Thanks Ron. I'd have difficulty finding the time to build another one of these today, but it was a fun project.

There were a couple of incidents that served as very good lessons for me during fabrication. The most imporatnt were finding out what not to do. Like the time that I burned myself in an odd place during the MIG welding process. I never would have imagined that holding the torch above your head could lead to that kind of problem. But those little sparks can get anywhere. Now I know better. One of my friends who witnessed it still laughs about it to this day. I'm just glad that it didn't permanently scar me. But it did take quite a while to heal.

There were also some issues with the initial performance, particularly the steering. But after identifying what the issues were I made some design changes that improved the performance significantly. One addition that I made was a\ silver anodized aluminum rack that attaches to the back of the cart. The tubing it's built from is about 2 1/2 inches in diameter. It really adds to the look as well as the functionality if you plan on driving long distances. Unfortunately I don't have a photograph of it with the rack in place. But it does look sweet.

Maui

www.EngineeringMetallurgy.com

Sparweb, thanks. I'd recommend a stock power steering rack instead of the one that I built. Mine was less expensive, but took a lot of work to build. Just buying one off the shelf would save you a lot of time and aggravation.

A 7.5 hp motor will certainly get you moving along with the right design. That makes me think of that cement mixer motor that was used on Mythbusters to test the MacGyver myth of building a two seater open cockpit pusher prop airplane from bamboo. If the guys on Mythbusters actually had a clue about how airplanes are supposed to function, they might have been able to make that one actually work. Done right, it should have flown beautifully.

Maui

www.EngineeringMetallurgy.com

Maui,
You missed the episode of "Junkyard Wars" where a team did just that!

http://www.youtube.com/playlist?list=PL8BE5105D4CC... (the only video link I can find is chopped into short pieces, but a fun view).


Thanks for the tip about the steering mech, too. I would spend days (weeks) fiddling with something like that.

STF

Many years ago an old mechanic showed me a rule of thumb for steering geometry. For steering axles with a tie rod straight across from wheel to wheel: If lines drawn through the center of the king pins and the center of the ball joints meet at the center of the rear axle, the wheels will track well in turns.

Bill
--------------------
"Why not the best?"
Jimmy Carter

Neat job on the cart, love this sort of stuff.

@ Waross, what you are describing is 'ackerman angle' - for more googling pleasure, but Im sure many of you are familiar with that,

Brian,