murray explorer project.

[Doc Sprocket]

SPOILER ALERT!!!

It's not as nuts as you think. Imagine a little utility trailer. Picture how that trailer can articulate, independant of the tow vehicle. Got it? Now, attach a couple of coilover shocks between the trailer and vehicle to help control the movement. Now, attach a panhard bar between trailer and tow vehicle- this will allow it to twist and bounce, but keep it aligned with the tow vehicle. Now install an engine and drive system on it, and while you're at it, take away the tow vehicle's rear axle. The suspension holds the whole thing up. It can twist and bounce, but will remain straight. The "trailer hitch" is a large ball or heim joint under the seat. I am working on a similar system using an actual trailer hitch...

 

[redsox985]

Can you make a drawing of it a bit more detailed than the one on the top of page 3? I'm not wrapping my head around this yet. Maybe a description of how it works?

 

[Dougthewelder]

great description toystory you really have your head around it.

i will get better video of it soon because i need to replace the sprocket hub. thanks for the interest even thought this is an old thread =)

 

[Doc Sprocket]

Might be an old thread, but definitely worth revisiting!

As you know, I have been toying with a nearly identical design, but it's on a long-term build. So I've had plenty of time to think it through from one end to the other. I'm very glad you built it- it confirmed to me that the idea was less crazy than I'd originally thought. I had a few concepts, the best of which was a large ball joint- In my case a 1 3/4" trailer ball and coupler. I had also considered building what would have resembled a large universal joint. There were other ideas too, but none this efficient, light, and simple. Kudos to you for making it happen!

Redsox, you might be trying to overthink it. It's simple as pie. Got a trailer? Watch it move. Only imagine that it cannot "turn", only bounce and articulate. The hitch is the large ball joint, the whole swingarm assembly pivots and twist upon it.

 

[redsox985]

So the axle swing arms sits on a ball joint kinda thing? How is it kept from swinging left and right?

 

[Doc Sprocket]

That's where the Panhard Bar comes in. It attaches to the vehicles framerail on one side, and crosses thru the vehicle's centerline, attaching to the axle on the opposite side. It allows the axle to freely move vertically (and articulate), while prohibiting lateral motion. Google "panhard bar" and you should find some decent info.

 

[redsox985]

So that's the crazy arc thing? I may build something like this from small parts to see if I have the general idea right. Does it use a ball hitch? What's the pivoting link? This seems almost too good to be true.

 

[Dougthewelder]

the joint I used is one end of a tractor tie rod I got at tractor supply. remember all the power of your engine will be pushing your kart from that point, so reinforce it accordingly.

you can see the joint in this video

http://www.youtube.com/watch?v=XoDjsIdD5hc

 

[redsox985]

So it's just a huge heim joint? Is your motor also mounted on the moving swing arm? Wait, stupid question, it would have to be for it to be chain drive, correct?

 

[Doc Sprocket]

Here's your sign!

Doug, Panhard bars "ideally" are perfectly parallel to the road at ride height. More specifically, the pivots. It looks like you have 4-6" vertically between the pivots. Never mind theory- In reality, how much lateral movement are you getting as a result of it?

I ask, because it's begging to look like a few of us will be attempting this, and it would be good to know how much of a problem this really is (or isn't).

 

[Dougthewelder]

yup the cross link should be parallel. in reality though the up and down motion of the rear suspension only causes about 1 inch of lateral movement and i have never noticed it in actual use.

and yea the engine is mounted on the swing arm. there is no way to isolate the the engine from the swing arm assembly using a chain. you could do it with a drive shaft of course.

have a look at this funny video Vince and i made with the Go Kart. just making fun of ourselves =P

http://www.youtube.com/watch?v=NVhgwJ9v1F0

 

[redsox985]

How did you do the steering to allow the frame to bounce on those springs?

 

[Dougthewelder]

think solid axle 4 wheel drive pick up truck. its the same as that.

 

[Doc Sprocket]

Beautiful, Doug! I love it- especially the mud romps!!! I too, am a "go kart man". My kids don't have a chance...

 

[redsox985]

So, I went and exhumed my Knex sets from the attic and decided to build a model of what I interpreted this to be. How does it look? Do I have the general idea?

 

[Doc Sprocket]

Nicely done! That's it, really. Your ball joint is okay- I don't know if it was intentional, but it looks like your model will pivot at a joint behind the ball joint. That's not needed, but I suspect you know that.

Playing with little kid toys, eh? Just riding you- great way to visualize things!

 

[r97]

yup the cross link should be parallel. in reality though the up and down motion of the rear suspension only causes about 1 inch of lateral movement and i have never noticed it in actual use.

and yea the engine is mounted on the swing arm. there is no way to isolate the the engine from the swing arm assembly using a chain. you could do it with a drive shaft of course.

have a look at this funny video Vince and i made with the Go Kart. just making fun of ourselves =P

http://www.youtube.com/watch?v=NVhgwJ9v1F0

bahahahahahahahaha!!!!!! thats great!

****, i don't have any sonics in my town......

love the music!!!

 

[redsox985]

Nicely done! That's it, really. Your ball joint is okay- I don't know if it was intentional, but it looks like your model will pivot at a joint behind the ball joint. That's not needed, but I suspect you know that.

Playing with little kid toys, eh? Just riding you- great way to visualize things!

I am quite amazed that it's so DA** simple! I do not think there are any other pivot points behind the ball joint. I'll look again tomorrow. There was some flex in the axle and frame, but steel would never permit that. And yes, I still play with kids toys! I would love to build stuff for Lego for my job, like be a kit designer, but that's a bit far fetched. Imagine going to work every day and just building Legos trying to come up with something new. That would be awesome!

 

[fowler]

that was my dream job

i still use it as a prototype maker
but i have the electronic RC technic as well as lego

 

[redsox985]

I just played with the model. The only movement is the 2 blue hinges, the shock pivots, and the ball joint.