The circle theory, suspension and engine chain mashed together?

[ibrahim123]

Okay hey guys you are probably saying " what the hell is this title " right now. Well ill tell you what its about. First let me show you my kart up to now.

The engine will be sitting right next to the driver on the right.

The rear suspension will look something like this.

When i ride it in the fields i will probably go across many bumps which is why i have the rear suspension, to make it a smoother ride (HOORAY). Now we have 1 problem. When i go across a bump the shocks will shorten from the force and therefor that circular motion will be created and that will cause the axle to get closer to the engine which means that the chain will not be tensed. This will probably cause the chain to fall off or not function well.

Now here is where the circle comes in. We know that the distance from the center of the circle to the any point of the circumference is always the same. What if applied that to the kart. Here is a drawing of my thought.

As you can see the engine sprocket is acting like the center of the circle and the axle sprocket is acting like a point on the circumference of the circle. This way, whenever the shocks work in bumps, the distance between the 2 sprockets will still be the same and that means that the chain will remain tense all the time.

Now this is my thought and it makes a lot of sense although u can never know for sure if something works before you test it right? Anyone got any opinions related to this?

And lastly the second problem is that say i drive on a rock on one wheel (lets say the right wheel). That wheel will move up a bit and the left one will stay on the floor.

This is how it would kinda look like if you guys didn't understand.

Now that means that the chain will move more to the left or right. We dont really care about up and down but sideways. I'm guessing that it might damage the chain or again fall off. Can this problem be resolved or is this not even something that i should worry about? Any advice is respected. THANKS FOR READING ALL!!!

 

[Doc Sprocket]

How is it that if you ride over a bump on one side that one rear wheel will move- Is the entire rear suspension not moving in unison?

As far as your theory goes, it is a commonly used practise. Either You need to align the engine sprocket perfectly with the suspension pivots, or use a jackshaft to accomplish the same thing.

 

[redsox985]

You could put a jackshaft aligned with the pivots of the swing arm that way nothing actually gets thrown out of alignment, things just pivot. Or you could use a panhard bar style suspension so that you get independent L/R tilt of the axle even though you have a solid axle. Also, with this, you don't have to worry about chain tension as the motor is mounted on the swing arm.

 

[Doc Sprocket]

You can even use a jackshaft as the pivots.

 

[getitdone]

I vote mount the engine on the swing arm. Like so:

one problem would be the engine mount would have to be level only when the shock is fully uncompressed. You could combat this with a auto correct engine platform.. I'll be thinking of idea's for it.


Alex





EDIT;
Key for second photo
springs, blue
engine mount stop, red
frame, green
axle, yellow
shock, purple
engine, mount, swivel, black.

 

[gokart14]

i have to strongly agree with gititdone even though the dirt devil kart says to put the engine on the side... i know from experince that if it isnt just right the chain will constantly fall off. To make it easier i would just mount the engine on the swingarm... works for me chain hasnt fallen off yet... also the whole rock thing makes no sense the axle wont move differntly it is solidy attached to the back A arm which is solidly attached to the kart so the sprocket eont ever be twisted. i think u might be a little confused.

 

[getitdone]

Personally, I'd do long travel A arm suspension. It would require CV / universal joints, and more welding and chopping, But I think it's worth it.
Depending on the length of your A arms you can have SO MUCH travel, and with just a standard 12" shock.

The formula is Resistance × distance from resistance to fulcrum = effort × distance from effort to fulcrum.

so lets assume a go kart has 2' A arms in the rear, the shocks are mounted .5 feet away, and the wheels are each 2 feet away. If the shocks are 650 lb compression load (it takes 650 lbs to compress them fully) and the kart weights 650 lbs with driver and passenger, and the weight is distributed evenly.

650 lbs x .5 feet = 162.5 lbs x 2 feet
= 325 lbs
I'm GUESSING that a 3" max comp shock with that setup would have 12" max travel.
OFC double A arm suspension is often (but not always necessary) better once you get to that much travel..



Alex