Itzy Bitzy, my first build.

[planejob]

I look forward to showing this thing to you Poboy, it's been a learning experience. Also, I used to skydive out by you - it's not too far, we could get together.

So here's an update. I spent about 4 hours on Friday just "looking at it" and thinking about how I wanted it to end up. I'm not convinced this is the right seat for this cart, although it holds The Kid quite well.

Because I used a jackshaft, and mounted it solidly - not the best of ideas - I had to come up with a chain tensioner for the secondary. It's not glued on yet. I toyed with hinged arms, spring loaded hinged arms, spring loaded tensioners... I settled on this. It's a 3/16 non-swivel rod end with 6 inches of thread, I put a 3/16 bolt through it and will tension the chain by tightening a nut on the top. I considered putting a heavy spring, like a valve spring on top to provide some cushion for shock loads. What you see is a slot cut through a 1" square tube, I didn't cut all the way through at the bottom, and will brace it at the frame to keep the slot from opening up... We'll see how it goes.

I got new flux core welding wire. WOW. I was using Northern tool wire, and I didn't know any better. I switched to Lincoln wire and WOW. It doesn't look as bad as anymore. In this picture the horizontal weld was Lincoln wire and the vertical weld was Northen Tool wire.

Here's the steering arm setup I came up with. Everything is adjustable, toe is not set yet. Crossing the arms over each other allows for the inside wheel to turn more than the outside wheel. I spaced the pitman arms apart to keep the bolts and rod ends from interfering with each other as it turns.

The little hole you see was used for aligning the arms while welding. I drilled two holes in each arm so i can adjust the travel/effort a small amount.

 

[rocketkart]

looking good man.

 

[Poboy kartman]

I really like the idea of the valve spring as a "cushion" ....not necessary, but hey, neither are AC, cell phones, or fast food restaurants.....

 

[chancer]

I really like the idea of the valve spring as a "cushion" ....not necessary, but hey, neither are AC, cell phones, or fast food restaurants.....

Hey! hey! hey! A-C is mandatory. Cell phones I'll give you that.

Planejob: Lookin good man

 

[crazykart]

Maybe in cali ac is necessary. Right now I would give my left arm for some 80 degree weather lol.

I like that tensioner idea, especially since it's adjustable. If you're going to use a valve spring you may want to find the lightest one possible though(as I'm sure you know) they tend to be extremely, well springy lol.

Looks good though, I'm sure your kid can't wait to ride it lol.

 

[chancer]

Maybe in cali ac is necessary. Right now I would give my left arm for some 80 degree weather lol.

Nah, I was just funning with Poboy, I am an A-C repair guy so of course it is necessary and recommended to everyone all the time. Yeah 80* would be nice it was 90+ here the last 5 days lol

 

[crazykart]

Lol, the warmest we've had here for the last 5 months was 50... I'll trade you anyday.

 

[planejob]

I've made progress.

I got the brake hooked up, installed the chains and tensioner (about 15 times... as I figured out the placement of each part), and was able to run the engine.

Of course, the carb leaked gas. Of course. Luckily it was a drain screw that had a burr on it.

I made myself a little bracket to position the throttle cable in line with the throttle lever. The governor is intact.

A lot happened in this picture. The floor / 'skid plate' got welded on. The pedals were installed, the cable bracket for the brake was removed and a new one was installed about 4 inches further back. Springs were added to the pedals. I used two different length of springs in an attempt to match the effort of the two pedals. Yes, the throttle has two return springs, one on each end.

I'm going to have to break out my toe-plates from the race car to get the alignment set. I bought the tie-rod kit from BMI and they came with Right hand threads on both ends... I guess they were cheap enough, but ****.

The outboard heim joints bind slightly, but noticeably, when turned away to full lock. I found some washers that allow a bit more mis-alignment, and if they werent' 3 bucks each I would have already bought 8.


Any other ideas for correcting the binding on the heims?

 

[Poboy kartman]

Swap your tie rods.

EDIT: BTW....$3 a piece?????? Spacers, or an oversized nut would do the same thing.....but.....$3 a piece????? They're less than 20 cents at the HD here.....?????!

 

[planejob]

Swap your tie rods.

EDIT: BTW....$3 a piece?????? Spacers, or an oversized nut would do the same thing.....but.....$3 a piece????? They're less than 20 cents at the HD here.....?????!

What do you mean swap the tie rods?

I'll drill out a couple of smaller washers and see if I can get the clearance I need.

 

[Poboy kartman]

I mean swap them on the pitman arms....looks like they would be straighter and work better that way.

In other words...but the left one on the front arm and the right on the rear...

 

[planejob]

I mean swap them on the pitman arms....looks like they would be straighter and work better that way.

In other words...but the left one on the front arm and the right on the rear...

I see what you mean, but I used the offset pitman arms and crossed the tie-rods over each other to create the right Ackermann setup. If I made each pitman arm connect to its nearest wheel then I would have funky steering - the inside wheel would turn less than the outside wheel.

For example: Currently, in a left turn the "front" pitman arm goes from 11 o'clock to 9 o'clock, 60 degrees on the circle. But using a horizontal frame of reference it only moves about 1.5 inches. A significant amount of the "travel" is consumed by vertical movement (dropping from 11 to 9). This moves the outside right spindle 1.5 inches at the connection.
The "rear" pitman arm goes from 1 o'clock to 11 o'clock, also 60 degrees, but with a smaller amount of vertical change (1 and 11 are in line with each other and in line with the steering arm). So they actually travel 2.25 inches in the horizontal plane resulting in the inside, left, steering arm being moved 2.25 inches.

 

[planejob]

Time for disassembly, some grinding and smoothing, and pink paint!
https://youtu.be/A51BGNafJgE

 

[Poboy kartman]

No....I mean....well...just no....I don't understand where you are are getting this flawed theory from....but...the pitmans have nothing to do with Ackerman.....and....the length of the tierod arms....nor their position (clockwise) have have any effect either....(unless one pitman arm is longer than the other)....that's the only thing that can affect the ratio...

Think about it this way: If you have a 20' pole and a 2' pole and they are parallel.....you push both arms 6".....the ends of of both both poles are going to move 6" from where they started......

Unless I'm missing something....both pitman arms are equal length.....as are the spindle arms .....

Ackerman is all about the relationship between the rear axle and the spindle lever pivot points in relation to it...

So....in fact...two pitman arms can only hamper the ease and simplicity in which those front wheels can be turned....(unless perfectly synched) ....AND.. unless non-equal in length will have no effect whatever....(except possibly negative) .....

You asked....I answered....

 

[planejob]

No....I mean....well...just no....I don't understand where you are are getting this flawed theory from....but...the pitmans have nothing to do with Ackerman.....and....the length of the tierod arms....nor their position (clockwise) have have any effect either....(unless one pitman arm is longer than the other)....that's the only thing that can affect the ratio...

Think about it this way: If you have a 20' pole and a 2' pole and they are parallel.....you push both arms 6".....the ends of of both both poles are going to move 6" from where they started......

Unless I'm missing something....both pitman arms are equal length.....as are the spindle arms .....

Ackerman is all about the relationship between the rear axle and the spindle lever pivot points in relation to it...

So....in fact...two pitman arms can only hamper the ease and simplicity in which those front wheels can be turned....(unless perfectly synched) ....AND.. unless non-equal in length will have no effect whatever....(except possibly negative) .....

You asked....I answered....

On this one I can claim to be right. I'll draw it out on some graph paper and show you - geometry and physics are both strong suits of mine. BRB.

Edit: Ok, I'm back.

Here's three drawings that show how to get differential travel of your steering arms by varying the geometry of the Pitman arms / pitman arm connection.

We are going to start with a circular pitman arm, and two connections point. A, for the right wheel, and B for the left wheel.

If we rotate the pitman arm/steering wheel 45 degrees clockwise we will move both the A point and the B point.

Both A and B are rotated 45 degrees - they are on the same circle so they travel together.

As you can see, the horizontal distance that A travels is 8 units in this example, and the horizontal distance that B travels is 4 units.

So "Ackermann" is a design principle where the outside wheel turns less than the inside wheel so that the centerlines of both front wheels intersect at the same point on an imaginary line drawn through the centerline of the rear axle. What this means is the inside wheel must turn more than the outside wheel, that is why you must cross the tie-rod over each other. If you connected B to the Right it would only Turn "4" in a right turn, and A to the left would result in a turn of "8", essentially, bass-ackwards of the Ackermann principle.

 

[2SlickNick]

Ugh me feel so lost.
That's why me will just modify existing karts.
Also those be some big city words for us simple folks lol. Cool build none the less.

 

[Poboy kartman]

You know....right at this moment, I still think you are flawed in your thinking...but I'm not in the condition I need to be to completely go into this....

And no matter who winds up right or wrong on this...I want to thank you in advance for the opportunity to explore some "out of the box" thinking..

I'm just as happy being proved wrong as being right...because someone is going to be able to benefit from the knowledge....

I'll get back to you on. this....

HE IS RISEN!

 

[planejob]

Poboy kartman, you were right and I was wrong! About the horses, the Lippizaners. They are from Spain, not Portugal.

The 8 degrees of camber seems to be too much, aesthetically and from a usability standpoint. The Kid can steer it, but she is clearly putting effort into it- the kart likes to go straight. Also, the front is about 3 inches wider than the rear wheel track because of the way the bottoms kick out. They're getting cut off. woohoo.

 

[Poboy kartman]

It takes a big man to admit he was wrong.....unfortunately...I'm barely big or very manly.....JK.....

I am still going to look at the whole "Ackerman tie rod thing" because....while the whole circle geometry thing makes sense...it goes over my head...but my "seat of the pants" gut feeling is that it is flawed....because you are looking at the travel that the pivot takes around a radius....while the tie rod is actually travelling linerally....and ....therefore. not on an actual "set" arc....I just haven't really had time to play with it to see whether it's what you think or not....

You could very well be 100% correct on that.....it's just that something doesn't seem right.....

But....thank you for manning up on the camber....I wasn't trying to be rude....but ....like I said....all things in moderation....and was afraid it would be excessively hard to steer.....especially for a little girl....(or even your daughter) .....(sorry....you're from Texas...so you know there had to be a little rubbbing comin).....

The offer still stands to bring it over and tweak it....but maybe if you PM Kartfab....he might want to help you out....he's about 1/2 way closer.....and a heck of a good guy and fabricator.....but I can't speak for him....
...

 

[chancer]

Wait is "linerally" even a word? sorry