Some old builds

[Russell ATV]

I thought I would post some builds I have done over the years, along with a "what I learned" summary. I built a fair amount of crap, but with each build, I got better.

In general, these builds were experiments in lightweight vehicles with suspensions. Here we go:

First kart, the Leaf Spring Steel, Tadpool Quad

Got to start somewhere. I laugh thinking about this kart, man did I get a few hundred things wrong. First, without any real supply of steel, I used galvanized tubing. I was careful to weld outside and avoid the gases, but this stuff is week. Next, note the plastic wheels. Lots of good deals on Surplus Center, just the wrong wheel for the job. The rear wheels had thick plastic barrels that I used a dowel pin to connect it to the 3/4" shaft. Nothing more fun that ripping off a rear wheel at 35 MPH with that much power (6.5HP clone)

I made the rear section only wide enough for the motor. Not the best solution for cornering. Also, the front wheel spindles had no kingpin angle or camber. It was a white knuckle ride with no centering effect. The seat was a small child's school chair. It was remarkably comfortable.

The leaf spring material was like 3/8" thick, and did not provide much spring. It was also very brittle and difficult to work with.

Russ

 

[Poboy kartman]

I posted up a pic of an old build somewhere on this forum.....oh..yeah...."Show us your stickers"...

 

[firemanjim]

Dude, that's really a cool idea. It would have worked better with a thinner leaf spring. That one is for at least 300-400 lbs probably, and you had no where near that much up front.....
This really seems like it could work good.....

 

[Russell ATV]

I eventually figured out the spring steel thing, so stay tuned. I think I will post a kart every couple of days or so. Let one or two ideas sink in and then move on to the next one.

Russ

 

[2SlickNick]

Hey Russell, you should fill out your profile (so we don't have to guess where you live) . Is this yours too? same frontend http://youngstown.craigslist.org/snw/4746710784.html

 

[Russell ATV]

Fair enough, my profile is updated. The Kart in the Craigslist is not mine. Honestly, the Craigslist kart does not use spring steel, but a pivoting arm.

Russ

 

[Russell ATV]

OK, one to Kart number two:

OneWheel Drive Ultralight

Total kart weight was 51 pounds and used a Tecumseh 4hp two stroke engine driving one wheel. Also used a couple of those crap wheels from Harbor Freight on the rear. Don't use them, as they wear out quickly. I was smart enough to stay away from the bearings. The front wheels where from Surplus Center. Great place to buy wheels. Seat was steel bars covered in pipe insulation.

At the end of the day, it was light and could be hung on the wall. It handled better than the first kart, but one wheel drive was no good and the sear was firm.

Russ

 

[whapit]

I thought I would post some builds I have done over the years, along with a "what I learned" summary. I built a fair amount of crap, but with each build, I got better.

In general, these builds were experiments in lightweight vehicles with suspensions. Here we go:

First kart, the Leaf Spring Steel, Tadpool Quad

Got to start somewhere. I laugh thinking about this kart, man did I get a few hundred things wrong. First, without any real supply of steel, I used galvanized tubing. I was careful to weld outside and avoid the gases, but this stuff is week. Next, note the plastic wheels. Lots of good deals on Surplus Center, just the wrong wheel for the job. The rear wheels had thick plastic barrels that I used a dowel pin to connect it to the 3/4" shaft. Nothing more fun that ripping off a rear wheel at 35 MPH with that much power (6.5HP clone)

I made the rear section only wide enough for the motor. Not the best solution for cornering. Also, the front wheel spindles had no kingpin angle or camber. It was a white knuckle ride with no centering effect. The seat was a small child's school chair. It was remarkably comfortable.

The leaf spring material was like 3/8" thick, and did not provide much spring. It was also very brittle and difficult to work with.

Russ

that looks fast

 

[Russell ATV]

Two Wheel Drive Ultralight

So, I improved most of the problems from the first Ultra light kart. This one had a live axle driving both rear wheels. All 4 wheels where the 10" units from Surplus center and performed well. I put a different piece of foam for the seat. The big changes were the spring steel and the engine. I tried a thinner and wider spring steel that was not the Leaf spring material. The leaf spring steel is a 5160 Alloy. This is thick stuff that is a bit brittle and cannot tolerate too much deformation. The better stuff is the high carbon steel such as 1095. Almost impossible to drill except with carbide bits, but great stuff. Mcmaster has it is thin bar/sheets. Trial and error is the best way I found to get the right balance of shock absorption and stiffness. I also used two layers of it to capture the front King Pin and keep the wheel level through the suspension travel. Also, I started tilting the front suspension back (king pin angle) which made a huge different in handling. This creates a tendency for the wheels to go straight.

Another test was of a Chinese Pocket Bike Engine. I imported this through Alibaba. It is a 50cc two stroke with a tuned pipe. I achieved a 8:1 ratio on the chain thanks to the tiny sprocket on the motor. However, not much low end power/torque. It did have a small power band "on the pipe" but not really usable. It was light but not good enough. As for quality, there was none. Almost no use and or the two I purchased, the pull rope quickly broke on one, and the head gaskets went on both soon after. Junk. About this time, I imported a few Honda Clones (before they started taking over karting).

Russ

 

[Russell ATV]

The Imported Parts Kart / Best spring Suspension

When reviewing the landscape of cheap Chinese engines, it was hard to beat the quality and power of the Honda Clone. The EPA had killed the two stroke, so finding a lightweight, low cost engine in 2007 lead to only one road, the 6.5HP Chonda. Several Chinese companies were rebranding the Honda Clone, so i procured a couple from several vendors. Result, they were all the same.

While looking around for motors, I found a few promising parts that could be had on the cheap. I choose a small kart as the source for the parts, that also used the Honda Clone. So, I built the next kart with better parts, actual steering wheels, wheels with integrated sprockets, an actual seat, and a decent brake.

This Kart was much easier to build without having to make everything from scratch. The build was also much stronger and reliable. I settled on 1075 spring steel 1/8" thick and 1.5" side to match my weight with the ride quality I wanted. The results were great. The kart would articulate up to 45 degrees front to back, and have a travel as good as half the diameter of the wheel. I was using a 13" wheel, so I had around 7" of ground clearance / travel. The frame was basically a lightweight sled with parallel tubes. The spring steel made up the front suspension arms and the rear links to the live axle.

Russ

 

[Russell ATV]

Imported Parts Kart/Best spring steel Suspension/Twin Engine

There was a time when I hoped to leverage my interest in karting/building into a business. I had found good sources in China, and the 6.5hp Clone was set to sweep the nation. To help test the differences between the engines and to also just create something a bit faster, I put a couple of engines on my spring steel suspension design.

It was not quite as nimble off road do to the increased rear live axle weight, but man was it a lot faster when both engines were fired up. The imported parts Kart above was later upgraded to add a TAV2 CVT transmission, and that did increase its acceleration (but not really the top end). A buddy and I would race the two. The CVT single engine would lead for about the first 20-30 feet, and then the twin engine with just the centrifugal clutches kart would zoom past. The twin would top out around 60-65 MPH in a slightly modified form (gov removal, intake and exhaust work). The sound of the twin along with the feeling when the clutches started to lock up was a blast. I think my gearing ratio was around 4:1.

Russ

 

[whapit]

looking good, looks a bit like what i am trying to put together, check it out if you like, here is a link.
http://www.diygokarts.com/vb/showthread.php?t=27173

 

[Russell ATV]

Yes, looks like you have also tried to keep the design simple and the weight down. If you are using the Clone engines, the design should match the performance. I eventually had to go the coil over spring suspension route as well. My next kart was my last spring steel suspension kart.

Russ

 

[Russell ATV]

The Last Spring Steel Kart

At this time, I moved from the plains of Texas to the Mountains of Washington. Gravel in Texas is about the size of a pee, and off roading is on well compacted clay. In Washington, the Logging roads and Wilderness nearby contain gravel with rocks the size of basketballs. Not to mention, You need more power to go up long duration steep grades. However, I tried to make one last rugged spring steel suspension design.

This one would get the engine off the live rear axle and provide better off road charactoristics, as the suspension would be fully independent. The rear suspension used 2 U-joints, one per side to drive the rear wheels. The spring steel would actually be compliant enough to allow for several inches of travel. The only real problem with this design was the lack of ground clearance. You could only get half of your wheel height for ground clearance, and when you sat in the kart and loaded it up, you would loose an inch or two. Finally, when you have a fully Independence rear suspension (IRS), the drive sprocket has to move to the center of the kart versus next to a drive wheel. So now, your low spot is the drive sprocket and brake.

It was the best Spring Steel Suspension Kart of them all, just not enough for the terrain.

Russ

 

[Russell ATV]

A Simple Rigid Kart / Engine Side Car

Realizing the limitations of the spring steel suspension, I tried a few ideas ranging from the round rubber cylinders of the Go-Ped Trail Ripper to a traditional coil over spring design. So, I build a fun little rigid kart with some left over steel and engine.

The design tried to make a very compact kart. The engine was placed on the side of the kart, close to the wheel and providing lots of space for the driver. Oddly enough, the lack of suspension had a strange effect. Any slight imperfection of the the frame flatness, caused the kart to pull to one side. I eventually had to cut the support to one side of the front frame members and pu the kart on a flat surface to weld it up. This solved the issue, and steering improved. The spring steel suspension actually had masked my frame imperfections. I built this kart in two days and it was good fun.

I did have to add a piece of Poly-carbonate to separate the engine moving parts from the driver. I geared it very low, so on a long straight, I managed to find the limits of a clone engine and blew a rod. That was OK, as I was forced to rebuild the engine with performance parts.

Russ

 

[Russell ATV]

The Son's Karts

My son's first kart was an electric, and it used the really thin 1090 spring steel and he loved it. perfect for a 6 year old. It could be driven in the yard and make it up hills. It had a 450 watt electric bicycle motor and a mess of NiCds. I don't have a lot of Pictures, but I do have one.

His second kart would not have range or duration issues. A 7 year old should not experience "range anxiety". This time, I would use a traditional coil over spring shock and various suspension designs. I had a 4HP two stroke (seen in an earlier build) that I once again put on a live axle. From some experimenting, I came up with a 4 link rear axle that had the shape of a W. It worked extremely well. It provided quite a bit of articulation and allowed for high ground clearance. On the front, I used a double A arm arrangement.

I learned (the hard way) that the spring rate on a kart depended on two things; the lever arm, and the angle. The coil overs I used were from Surplus Center and cost $8. They are 220 lbs per inch. My son on his kart only weigh about 100 pounds, so I would have to angle the shocks (off vertical) to reduce the spring force. A 45 degree angle will reduce the spring force by half. The other thing is the lever arm. You cannot attach a spring to a wheel, so it is located at some distance from the wheel on the suspension arm. If the coil is located at half the total length from the center of the wheel to the pivot, the spring rate is half.

At any rate, it worked perfect. The kart had about 8" of ground clearance and about 8" of suspension travel. It also was relatively light, so my son could move it around if needed and easily control it. I had to rig up a governor to slowly wean him into the kart. The little engine will spin up to 6500 RPM, so it is likely over the rated 4.5HP at 3300 RPM.

Extra credit is given if you noticed the seat being reused for yet the third time.

Russ

 

[Russell ATV]

The Rail, long travel Kart

After studying various options for independant suspensions using a coil over spring, I decided the double A (or wishbone) was the best solution for the front tires. For the rear, the solutions were highly varied. However one design, a 3 link trailing arm, seemed to provide the most room for the engine and drive in the rear of the kart. This is similar to what a RZR 1000 uses. The coil overs link to the center of the kart frame versus the rear. The long trailing arm can accommodate a very long travel.

Another item I wanted was to keep the weight low and the width as narrow as possible. So, I used a single beam as the frame of the kart. Therefore, each front suspension arm shared the same bolts. It ended up having 14" of ground clearance and about that for travel. The rear suspension geometry was not quite perfect (I later learned everything needs to share the same arc path and be parallel), so I had to use telescoping shafts between the U-joints. The U joints were beefy units from Surplus Center I picked up for around $15 a piece. I skinned the frame with thin Stainless steel to provide some protection from tire debris.

I built up a racing motor for the kart. This included a billet flywheel, high compression head, Cam, stiffer springs, slide carb, and exhaust. I mated it to a TAV2 and gave it a resonable final sprocket drive of 7:1 (to 18" tires). The CVT tended to boog down the engine, preventing it from spinning up to the higher RPM the engine was now capable of.

In the end, the single rail frame ended up making the kart too long. Also, the poor placement of the rear shock tower and design of the rear trailing arm make it too fragile. It was a good start, but not tough enough for the terrain I have around the house.

 

[2SlickNick]

Wow Russ!!
I love the progression of your fab and build skills; Keep it coming.....

 

[Russell ATV]

High Power Kart, Part 1

At some point, modified industrial engines (or two) will just no longer cut it. To make a kart tough enough to handle tough terrain, you must make a solid, if somewhat heavy kart frame and wheels. So, I watched Craigslist to find the right mix of tires (cheap) and motor (cheap). I found a couple of ATV front wheels that were about 90% and $50. As for the rears, I used an 8" rim from a mower, and mounted the largest tires I could find (that were cheap). I was looking at lower CC motorcycles, preferably still in the bike, as I could actually confirm it would work.

Craigslist is full of "ran when pulled", "needs almost nothing", and "easy fix". So, I found a listing for a Honda XR200 that was a runner but needed work. I see the bike, and I immediately know I would have no issue pulling the motor, as the bike was toast. He tried to get it started, and it would pop and fart, but not really run. He wanted $350. I convinced him it was worth $200. I took it home, replaced the plug, cleaned the carb, and reset it to factory (he had it supper rich, wetting the plug). Ran like a top. This engine is rated for 20HP, manageable.

So, I build up a suitably strong frame using the double A arms on the front. To simplify the rear end, I would go with a Swing arm rear axle. As with the rigid kart I had build previously, I mounted the engine next to the driver and put the seat at an offset. This kart was designed for mountain trails, so it needed to be 48" or less wide, and short. It was compact. I reused almost everything off the bike; gas tank, brakes, rear shocks, jacked up spark arrestor exhaust, and cables.

The kart had 14" of ground clearance and 13" of travel. It was a mountain goat. As soon as it was functional, I tried it out. Good power, although shifting was a bit of a pain off road. The big problem was the "tuck" that would occur when cornering with a swing arm. Swing arms tend to lift the inside rear tire in a turn. This is a bad thing. Hence, build part 1.

 

[Poboy kartman]

COOL.....