Homemade Full Suspension Off-Road Kart Build Thread

[k-man1081]

Hey guys and gals. I noticed that I wasn't getting anymore responses in my other thread, then I realized why...I was trying to start a build thread in the welcome section, LMAO!!

I'm going to be designing and building a homemade full suspension off-road kart. I've done 3 solid days of research, primarily on welding and a-arm designs. There's still tons of research to do still, obviously.

I have the design, on paper, for the basic shape for the chassis that I'm working with. I'm now working on the designing process of the a-arms. I'm working from the wheel inward because I'm reviewing someone's step-by-step process of designing the a-arms. I already ran into a decision process that I'm stumped on and need help with. I'd like to get some input into wheel size. Someone told me to go with a deep back-spacing (in the rim) so that I can design the a-arms to be extended; to reduce bump steer. I just don't know how much back-spacing they were talking about.

I'm looking at getting:
20" (tire height) x 10" (tire width) x 10" (rim diameter). 4.5" back spacing. 8" rim width.

Here's a link to a wheel that I quickly pulled up and it caught my attention.
http://www.northerntool.com/shop/tools/product_18867_18867

I'd love to get your input and suggestions. Thanks!, and have a good one.

 

[fowler]

Unless u have a good budget then getting flash wheels that suit your design isn't a must. just find the best quad tyres u can and run with them

If u haven't already then read up on steering geometry

This is a must for designing your own suspension

For the purpose of limiting kpi u want a wheel with big offset
This is what u are calling back spacing

So it's how far off centre the hub mounts
Look at a car tyre it's really shallow on the outside
And deep inside

This is done for two reasons
U want your kingpin to pivot the middle of your tyre
So u angle it
But the more angle the heavy the steering gets
So instead of making a bigger angle u move the tyre centre in by giving it a big ofset

Secondly
Each wheel is supported by two bearings on each side

U want to give each bearing an even load
But this is hard when the rim mounts to the outside of the hub

So u give it offset to bring the middle of the tyre to line with the middle of the bearings

The down side of this is even though y have made even load on your steering system u now have a lot of load on your rim

This is all mighty complicated and u won't find all the parts that match up unless u start machineing


If u get some quad rims like the ones on the link

Then some generic quad hubs that suit

Then u design your kpi to suit all this

Then once u have spent hours researching and building a perfectly aligned system u take it out and realise u are driving on slippery as hell ground and geometry off road doesn't matter one bit

The most important things in off road suspension is bump steer
And Camber change thougout travel

But stil design all the geometric principles into it

Really Ackerman is the only one that won't affect your off road driving
But it will affect you on road

 

[k-man1081]

Thank you for your reply!

For now, I'll go with a set of ATV wheels like the ones that I posted the link for.

I'll read up on the steering geometry.

Would you consider a 4.5" off-set to be adequate?

This is my first build, so my budget is low. That being said, I will not compromise quality or safety due to a budget. I always compromise my budget for quality and safety.

There seems to be a lot of variables, however, I believe that after a time of designing it beforehand it's possible.

 

[k-man1081]

This is my basic chassis design. It still needs more work. I'll post up side views, bird's eye view, and front view of what I plan on doing to the chassis once I draw them up.

 

[OzFab]

I noticed that I wasn't getting anymore responses in my other thread

That's strange considering, in the last post, I asked a question that hasn't been answered yet...

 

[k-man1081]

I just saw it and replied. I didn't see any responses last night before I made this thread, so that's why I made that statement. I'm hoping to start a build thread in this section.

 

[OzFab]

Thanks! I just realized that I will most likely be going -5°, so that would be 95°, correct?

No, you don't want negative caster, that means the top of the spindle is ahead of the bottom, leaning forward at the top; you want it the other way around...

Oh, ok. Will mounting a center bearing be safer, on the parts/components, for off-road applications?

In short, yes but, not many of us do it...

 

[k-man1081]

I found a box for a T.V. that I just purchased not long ago. The dimensions seem perfect, so I'm going to use it as a tool to take measurements. I'm a practical kind of person, so this helps a lot more then drawing one up. Although, would you guys suggest that I still draw one up, on a piece of paper, just to be safe?

 

[OzFab]

That's the first step (& a good one at that) however, if you're thinking what I'm thinking, that will only give you measurements for the drivers section

 

[k-man1081]

Lmao, you knew exactly what I was thinking. I'm glad to know that I'm off to a good start, though. I will draw the plan on paper again to try and make it at least look like a 1 seat kart. I have a difficult time trying to draw in perspective.

 

[OzFab]

Me too so, I didn't try; I just drew plans from different angles (side, front, back & above...)

 

[Poboy kartman]

Me too so, I didn't try; I just drew plans from different angles (side, front, back & above...)

That's called drafting. .... Not to be confused with the Texas karting Olympic game....where we see who can consume the most draught beers and still drive a kart.....sideways .....

 

[k-man1081]

Lmao ^^. That was funny!

@ Fabroman - I will just draw them like you say...side, front, back, and above. I'll post pictures when I finish them.