Designing a 4 trailing arm go kart.

['69 baja]

Well I'm finally building a go kart after 2 years of being a member here.My friend and I are going to build go karts over the summer for a bit of an engineering challenge and as a summer project to occupy our time.The build is going to be slow but I'll try to get some pics in of both builds.

I just got the metal today $45 for 25 feet of 2x1 .090 tubing.I've got a basic frame design but with A different suspension system than what i have usually seen on most karts.I'm going to use 2 trailing arms mounted on the front and then use the normal C bracket with a 1/2" stainless steel "tee" fitting for the spindle mounted on the end of the trailing arm.Then a 2 link solid axle design with a 1" live axle for the rear.About what you'll find on a '60's VW Baja.

Here's my design

The chassis so far is not welded because i intend to use angle iron as a L bracket on every 90 degree joint and bolt it together on top of welding it because i don't trust my welds yet.

I didn't have enough money for all of the steel so there will be more bracing and I still need to add the shock towers and mount the trailing arms.I plan to use a a 1/4" thick c bracket to hold the trailing arms in place.For the arms themselves i will drill a hole near the end of the arms and then weld in a bushing so the arms will swivel on 1/2" bolts in the c brackets.Any other ways that might work?

What's your guy's opinion on the design?Thanks

 

[T-man]

hey 69
that looks like a cool idea, I have seen someone on here do the same type of thing but the arms went four word (sp) it was a while ago so maby one of these other guys might remember who it was.

 

[newrider3]

You need to rethink your rear end design, either pick a swingarm with a solid axle or go all the way with independent trailing arms. Having independent arms but a solid axle as in your drawing won't work properly.

 

[Doc Sprocket]

I believe that is a swingarm with a solid axle, unless I'm lookin' at it wrong. Might have to be beefed up, tho'.
The only fault I find with a trailing arm frontend, is horrible bump steer. The arms are travelling in a longitudinal arc, while the tie rods arc laterally. That said, the effect is magnified with long travel suspension, and I would imagine you're only going for a few inches. You can help counter the effect with tie rods that pivot as close to frame center as possible, ie direct steer or bellcrank. Using a steering rack with only make it worse. You can also minimize the problem by engineering the suspension such that the trailing arms are as close to level with the road as you can get, at static ride height.

 

[solomon]

yea its a rear swing arm with a solid axel

 

[motor_head]

the bump steer won't be bad at all my fourtrax has the exact same suspension set up on it, it's going on 24 years and not a problem with it

 

['69 baja]

The rear swingarms will be connected with 1 to 2 crossbars and if necessary i can make a 3rd swing arm in the center.I'm going for around 3 to 4 inches of travel in the front.I've hit a snag with the front end though with the current design i think the front tires will hit the trailing arms and limit the steering quite a bit.Any ideas?

I got it all welded up today,welds look better than I thought they would but I'm still glad i bolted it together as well because they aren't pretty.I'm pretty sure they got good penetration as there is rainbowing and I blew a few holes in it.Sorry for the pics it's a cell phone.

 

[rgvkid]

The front setup is probably only good for going straight. The front arms are going to buckle as soon as you put torque on it in a turn and it will tweak the tie rod. Especially because it is rectangular tubing and the torque will be on the tubing the easy way rather then then the hard way. Shorten the width of the frame in the front and triangulate the arms which will help with the torque on a single tubing. Not sure how the steering will handle with that setup but i would seriously rethink the front arms before you wast any more tim on it. Better to use square or round tubing on the arms. If you are using square then rotate it 45deg. which will be a bit stronger. I'll try and do a sketch of what im talking about.

 

[rgvkid]

Hope this makes sense. Also are you arc welding or is that a mig? Too much spatter, wondering what your settings are.

The yellow would be the frame and the red the triangulated trailing arms.

 

[The_Machine]

why even bother with trailing arm or 4 link?

 

['69 baja]

It's a 100 amp flux core welder set at 70 amps with wire speed at 4 out of 10.

I like your triangulated front arm design but im not sure if my welding skills are good enough as you can see in the pictures.To help stop the front end from buckling i could use some 2 inch or 1 1/2 inch 0.120 square tubing for the trailing arms.Think that would hold up better?

 

[T-man]

Hey baja I did a few simple videos on kart build. the rest of the videos are on my channel if you want to watch them. But this one showes a simple welding demo. I hope this is usefull to ya.

http://www.youtube.com/watch?v=x9AaYoHDlkw

 

[Doc Sprocket]

the bump steer won't be bad at all my fourtrax has the exact same suspension set up on it, it's going on 24 years and not a problem with it

Sure. But '69 Baja didn't design your fourtax. It's not as wide as a kart, the arms probably aren't as long, and it won't get worse with age. I'm pointing out some engineering stumbling blocks, which are irrefutable.

RGV makes a good point with regards to lateral loading.

 

[modelengineer]

but the arms went four word (sp)

forward...?

 

[T-man]

ha ha , ok , (forward)

 

[psycho_builder]

the idea of trailing arms up front is kind of weird to me but i have seen it done, heres a pic of a friends

 

[Kaptain Krunch]

VW bugs used front trailing arms.

Not worth using, and designing on your own IMO. Pretty complicated.

 

['69 baja]

Hmm what type of design would you guy's recommend that I could use on the current chassis design.

I have an idea for a single a arm design using the trailing arms i already made and put them in an H design.

I'm going to go ahead with the front trailing arm design up front not permanently.The design I had required no welding for any of the trailing arms.So if they don't pass my test(hammer) I can go to my plan B and install the single a arms up front.

 

['69 baja]

I just thought of a new design for the front after looking up suspension designs.It's a hybrid trailing H arm/J arm design.It looks pretty strong and will require minimal welding if at all.What do you guys think.

 

[Doc Sprocket]

Should be stronger, but still subject to the design pitfalls I mentioned above.