Designing a 4 trailing arm go kart.

['69 baja]

Ran into a bit of a problem.The sprocket i have is a #53 51 tooth sprocket which fits the front sprocket but the bolt circle is 153mm or 6in.I cant find any hubs with that measurement nor any #53 sprockets with a 5.25 B/C that don't cost ridiculous amounts of money.I was hoping to use the 12ft of #53 chain I got with the bike along with the custom 51 tooth rear sprocket.

So I can either spend about $75 for a #42 setup if I can even find a sprocket that fits the engine or I can try my hand at making some sort of adapter plate.What would you guys recommend?Thanks.

 

[gokart14]

I would try to make a adapter plate. 75 bucks is alot

 

[That One Guy]

If the plate is free, or near free to make, and time isn't of the essence, make the plate first. nothing to lose.

 

[The_Machine]

so the caster goes from -30 (looks like it) to 0 on a bump? this suspension design sucks. It's not BUMP STEER, it's VARIABLE TOE!

I say tear it off and make single a arms if you want simplicity and most importantly, functionality. quit making hasty decisions and do it right the first time. I'm saying this from my own experience.

Actually, no. Finish it. I'm just curious as to how it'll perform. Unprotected tie rods.. Buy 20 sets, though. You'll need them.

 

[Doc Sprocket]

Some food for thought on minimizing the bumpsteer. Try to engineer things so that your tie rods run parallel to your trailing arms going up to a bellcrank close to the trailing arm pivot point. From that, you can have rods going across the frame to your steering mechanism. This way, the tie rods travel in an arc very similar to the suspension arc, minimizing the bumpsteer. If you're an engineering genius, I would imagine that if you could work out a way to make the rod travel through the trailing arm pivot, it could completely eliminate the issue.

 

['69 baja]

Guys I know the front suspension sucks.It is a prototype and will be changed in the near future.I already have a single A arm design figured out that will use the same steering design and tie rods I'm planning for the L arms.It will cost me no more than $10 to redesign the front end(I'm getting this steel for $1.25 a foot).

Here is my secondary design.

 

['69 baja]

i plan on ordering some parts from BMI this weekend.BMI does not have summary pages so I'll just give the part numbers.

1" Live Axle $20.00 (45" #400045)
SKU/Part No: 4000**

Wheel Hub 1" Bore
SKU/Part No: 260050

and either these for the front
Heavy Duty 4 on 4 Wheel Hub
SKU/Part No: 260056

or these
4x4 Wheel Hub- 5/8" Bearings
SKU/Part No: 260055

I'm thinking the hubs and maybe the axle might not be strong enough for a buggy this powerful.Does anyone have any experiences with them?Any recommendations?

At 45" the axle will have 7 inches of over hang(around 4.5 inches with a 40" axle)past the pillow blocks is that acceptable or will it bend too easily.After I get these parts figured out and purchased the buggy will have about $220 in it with only around a $100 to finish it.Which is fitting well with my budget of $400.

 

['69 baja]

Anyone?I need to order these parts tonight or tomorrow.

 

[fowler]

should be fine
my quad bike has like 13 inches of overhang and in is about 4cm (1 2/3in) thick

 

['69 baja]

Thanks I'm putting in the order tonight.$147 shipped plus $20 for 2 eBay pillow blocks.Will hopefully be here Friday.

Will be using a standard 4 on 4 wheel hub to hold the sprocket once I make the adapter plate for it.

 

[T-man]

hey '69 baja that new front end looks good, I did that design on the A-kart.

 

[That One Guy]

Use the hubs with the bearings for the front wheels.

 

['69 baja]

My Redesign

It's been a while and a lot has changed.Got the axle,hubs,and front spindles mounted.Along with an extensive front end redesign.

Here's a small pic of the 3000psi "tee" fittings that I'm using for the spindles.There about 3 times as thick as a standard fitting.

The "H-arms" took 14 ft of 1" 1/4" .090 and another 9 ft of 2"x1" .090 for the frame.The arms are 20" long and have just over 10 inches of suspension travel.The rear has 9 1/2 inches of travel with a swingarm length of 22".And a total frame length of 95" with a width of 58" spindle to spindle.

I just got the tires for the buggy at a shop advertising on Craigslist.The fronts are 21x7xR10 standard quad tires and the rears are 20x7xR10 ITP Holeshots.Got all of them for $40.The holeshots still have the hairs.Thanks any contributions are appreciated .

 

['69 baja]

Oh and the arms are raked +5 degrees for caster and the spindle C-brackets only have a bolt holding them for now because I am unsure about what would be a good caster setting.Any Recommendations?

Also the the C-brackets will be gusseted like this.As for the grade 8 bolts having a gap right now it's because the steering arms will be mounted through the bolt and then welded to the steel fitting.Just to clarify.

 

[fowler]

looking good
are u going to weld the C braket on
i think the suports are very nessercery

 

['69 baja]

Yea the C bracket will be welded on I'm just waiting for some opinions on what would be a good caster setting.

 

[theo]

I use 5 deg. of caster on my buggies. If you plan on lots of wide open stuff then you can use more, but for off road with lots of turning 5 is ok.

 

['69 baja]

Ok thanks.A few more days of working with my dad and the thing will be off the ground and on tires ready for the engine.

The next biggest purchase after the wheels will be the steel for the roll cage.I would like to use 1" .090 or .120 square tubing to keep the weight down(even though the frame only weighs around 65lbs right now)and the main roll bar behind the seat to be 2x1 .090.I'm a little unsure about the strength of the 1" square tubing.Is it viable for a roll cage?

 

[Flexibel_kampfe]

Ok thanks.A few more days of working with my dad and the thing will be off the ground and on tires ready for the engine.

The next biggest purchase after the wheels will be the steel for the roll cage.I would like to use 1" .090 or .120 square tubing to keep the weight down(even though the frame only weighs around 65lbs right now)and the main roll bar behind the seat to be 2x1 .090.I'm a little unsure about the strength of the 1" square tubing.Is it viable for a roll cage?

I agree with keeping the weight down. Last thing you want is a top heavy kart... Since thus increases the likelyhood of a roll..

Can you do do Aluminum with that rig? Out of curiosity, what type of welder is that? It looks like a HF, but I wasnt sure....

The reason I ask, is because Aluminum is lighter, but can be just as strong....

 

['69 baja]

It just a Harbor freight 90 amp flux welder.I must of got lucky when i got it because it's rated at 45% duty cycle instead of 18% like usual.It's been good to me,I've had it for 4 years and it still works beautifully.

I'm not sure if they make aluminum flux wire.Would be nice though.Could make a chassis that weighs 30lbs.