From Scrap to Not Scrap

[DCProductions]

Here is the build so far. It started out as $20 from the scrap yard. The engine was free along with some of the hardware. There are some pictures missing but this should cover about everything. Hope you enjoy!

Rust was a popular paint color back when we got this.

Free engine, cleaned, painted and ready for some upgrades!

Custom brake rotor. This sprocket was cheaper than any brake disk we could find.

Test fitting the roll cage

Comet SCD-1 with sprocket (black) and brake disk bolted on.

Rear End

Bottom panel.

$5 trailer tires. Good for 7000 miles. Good thing, because we were planning on driving to California and back in the kart.

mock up

Double Pedals

Skid plate

 

[DCProductions]

Caliper and mount

Master Cylinder

Spindle Bracket Chopped

New Manly Spindle Bracket

Suspension! sort of...

Throttle linkage

I realize this is a massive amount of pictures. Is this considered spamming? Anyway, if you have any questions about the kart or about a certain picture ASK AWAY!

 

[Doc Sprocket]

No, you're not spamming. You might want to consider reducing pic sizes to be easier on folks wit dialup, but other than that, s'okay!

I had a giggle to myself looking at the first pic of the diff with two sprockets on it. That's exactly what I did for a brake rotor on my kids' kart- just modded another sprocket to fit.
Good stuff. I'm going to go back and have a closer look at things...

How's the front suspension working out? And what's with the double pedals?

 

[DCProductions]

How's the front suspension working out? And what's with the double pedals?

The front suspension actually loosened up. While he was driving it, I guess it wiggled around enough for the grease to take over and now it flexes fine. Big problem though: Bump Steer. He wobbles all over the road at high speeds.

The double pedals... Well the original pedals were one half that size and could be bent by hand. He had a spare frame with identical pedals so he decided to make stronger ones. They look pretty cool I think. Definitely easier to find with your foot.

Thanks for the kind words. Hopefully the guy who made this will come on some time and explain a little better.

Edit- these are pictures from photobucket. Do they have a function to reduce size?

 

[DCProductions]

Figured I might as well put these here too.
http://www.youtube.com/watch?v=zXsV46_6eNo
http://www.youtube.com/watch?v=8a0gZMJbBOk
I made the pull start handle out of a PVC T and some thin wall PVC pipe formed with a heat gun.

 

[Bluethunder3320]

pretty nice. gets goin real good.

 

[DCProductions]

He's still got a little bit of carb trouble. We don't really know what's going on. It is completely cleaned. It's running a #90 jet which I would think is correct for the air filter. Anyway, he's just happy it's working.
Oh, the video is not full speed; he was taking it easy. Also at full speed, like I said earlier, Bump Steer becomes a big problem.

 

[Doc Sprocket]

We can probably help you cut down on the bump-steer. Put up some (smaller) pictures showing the pitman arm, tie rods, and spindles so we can get a feel for the current geometry.

 

[mrfreyguy]

You might be getting bump steer because your spindles are slanted inward? Or at least thats what I thinks causing it.

 

[DCProductions]

You might be getting bump steer because your spindles are slanted inward? Or at least thats what I thinks causing it.

That is probably true. I never noticed how strongly they were slanted in. Thanks for pointing that out.

The thing that could be causing bump steer (that I know of) is the spindle moving contrary to the tie rod's arc. The slant of the spindle bracket is probably too much as of now; however, there should be some slant because the tie rod still travels on an arc. Minimal slant would be best.

Correct me if that's wrong or if there are more causes. I'm not sure I covered them all.

 

[Doc Sprocket]

I think basically, it's the wrong combination of both of them. If the tie rods were arranged to arc with the spindle movement a bit better, you could probably cut the bump steer down quite a bit. This would involve relocating the pitman arm on the steering column, possibly adjusting its length, too.
The slant, being your KPI angle, is desirable. Best not to eliminate it.

 

[DCProductions]

That sounds like it would work and I like the idea of not having to remount the spindle brackets. One question though: doesn't the fact that the spindles are moving inward force unnecessary toe out? It's like the tie rods are getting longer.

If this doesn't make sense I can draw a picture. I think that would explain it a little better, but I may have done an ok job explaining. Sort of writing a paper right now so don't want to be too distracted...

 

[Babazoo7]

Hi im the guy that built most of this kart. Regarding the spindles, they are terrible. Both are bent an inch or more inward at the point were the tie rod connects killing my turning ability but im not positive that they are cause a significant amount of bump steer on the road. After further road test i realized that one of the rear hubs may bent. while removing them from the axle a few misplace sledge strokes warped the surface were the rim joins causing severe vibrations at higher speeds. the front springs are actually working very well as DC said they loosened up after a run or to and make driving off road a little more comfortable. I am going to redo the spindles to help my steering however any suggestions on making them as strong as possible? DC made some out of angle and they did well until we abused them badly off road.

 

[DCProductions]

Have you tried bending the hub back yet? Also if you're going to redo them consider pointing the spindle arm backward and re mounting the pitman arm on the steering column accordingly. Mine have been pointed forward and have become very familiar with rocks and trees. Any more test drives?

*Toystory could you explain KPI angle a bit more (or point to a thread)? I think I know a bit about what your saying. I'm trying to find all the offsets, angles, and such for an independent front suspension.

 

[Doc Sprocket]

Have you tried bending the hub back yet? Also if you're going to redo them consider pointing the spindle arm backward and re mounting the pitman arm on the steering column accordingly. Mine have been pointed forward and have become very familiar with rocks and trees. Any more test drives?

*Toystory could you explain KPI angle a bit more (or point to a thread)? I think I know a bit about what your saying. I'm trying to find all the offsets, angles, and such for an independent front suspension.

Regarding pointing the arms backward, I much prefer that. It lends itself much better to achieve the correct Ackermann steering geometry.

KPI is typically about 10* inclined from vertical. This is an average, and a good starting point. It is also related to the "scrub radius"> Ideally, youd draw an imaginary line thru the kingpin, and that line would hit the road right smack in the middle of the tire's contact patch.

The bumpsteer thing may be a bit trick with the suspension, but the KPI angle is not the sole reason. You should be able to rework the frontend WITH the suspension, and still have a decent KPI angle. In fact, your KPI could be at dead vertical, and have horrible bumpsteer. It's all in how the tie rods move in relation to the spindles during suspension travel.

 

[DCProductions]

So basically it comes down to testing the tie rods on the top and bottom of the spindle arm, spacers, and moving the pitman arm around? That seems fairly simple. I'm gonna see if I can find some thread to read up on.

 

[Doc Sprocket]

It may help for you to set it up on stands, and take a wheel off. Remove the spring on that side, and disconnect that tie rod from the pitman arm. You can hold the tie rod in various positions in relation to the steering column (either by hand or with a fixture) while cycling the suspension up and down. This should allow you to see the bump steer pretty clearly.

 

[DCProductions]

Ran into a potential problem the other day: the driven unit on this kart is either inboard or outboard. I looked on BMI (where we ordered the driven) and apparently there are both inboard and outboard models. This was not displayed on the site at the time but it makes sense now. I think we have an outboard mounted in an inboard position. I'm comparing the pictures of each with what I can see of the driven in the "Drive-train Test" video.

The fix isn't too hard. BMI sells the inboard spring, and installing it would just require dis-assembly.
Am I right about which driven type it is?

 

[apfcb94]

ha ha mine started out as scrap also. bought it off a friend for $10, it was a carter 2885 2 seater but i have converted it to a 1 seater nd fixing to extend the frame

 

[DCProductions]

Nice! Do you have a roll cage for it?