1/2 Scale Cycle Kar(t)

irk miller

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We started converting the racing kart spindles over to a motorcycle dimension. Kart axles are pretty short. This was done with a KZ650 axle cut in half. The KZ axle is 9.25” long and 17mm thick. We need two 16mm axles at 4.5” long. The threads have a 16mm OD on the KZ axles. A simple trim on the lathe and pressed in.
The wheel bearings were also swapped for a 16mm ID.
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irk miller

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Of course, I had to say that first wheel was easy. Turns out, the other wheel is a Suzuki with an outside bearing that has a smaller OD. Had to take the wheel apart and machine the hub to make the bearings match. Good excuse to lighten the hub up a few grams and to teach my guys how to build a wheel.

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Brent

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Sorry I'm behind on the thread Irk. What are the round parts and the lump attached to the sprocket on your axle? What was it originally from?
 

irk miller

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Sorry I'm behind on the thread Irk. What are the round parts and the lump attached to the sprocket on your axle? What was it originally from?
It's a Peerless differential. They're made for mowers and golf carts. I got it off of a BGW Tri Rod I bought at Mid Ohio two summers ago. Here is what the BGW looks like:



The round disc objects on the axle are brakes. Karts often ran a strap drum brake setup. Works okay for something not meant to go very fast. Here:



I'll be running a sprocket and disc brake, both mounted directly to the differential housing. Here is an example of how that will look:

 
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Hurco550

Keep er' Between the ditches
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We are using that same differential on a hit n miss horseless carriage project that dad and i started years ago. It has held up surprisingly well for a piece of "budget" riding mower hardware.

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irk miller

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We got the sprocket and brake rotor installed. The brake rotor is just a sprocket with the teeth machined off. While we had it apart, we re-greased the innards.

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irk miller

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Sometimes the best ideas come from mistakes. I smashed, bent and cracked the center of one of my SR185 hubs trying to remove the bearings. Since we had yet to find a solution for converting the hubs over for drive wheels with the kart parts I bought, I decided to try something out. I machined out the center of the hub, machined an inset then tapped holes to mount the kart hub. Seems to be the ticket, and it gives us options for offset.
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No idea why it’s flipping them
 
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irk miller

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Another day with the crew.

Luckily, one of them is a competition mountain biker and a pretty competent wheelwright.



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Our engine and rear axle is fully mounted. We’re running 4 pillow blocks on the axles.

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We also got our front pedals located. I’ll spend this evening figuring our front axle. Tomorrow, we’re taking a field trip to JRPW Racing, which is a local kart race shop. Hopefully, we’ll walk out of their with a handful of parts and the knowledge to get close to 15 horses.

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whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Absolutely cool.

Wow, a lot accomplished......good going.
 

SONICJK

Reminds me of...me No, I'm sure of it. I hate him
Looks awesome.

My one concern is the pillow blocks. Admittedly not familiar with these carts if that's a normal setup then ignore me, but I've had way more than my fair share of those castings break. From the 9.99 amazon ones to the 150 dollar ones from mcmaster with vibration the castings can crack.
I'm concerned about the direction of the force with them mounted that orientation , all the force is going into the shoulder of the casting which is where I've had them crack.

i assume it will likely be fine, but it looks like no suspension, (and vibration is what breaks them) combine that with a sudden impact like a pothole...
 

irk miller

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Looks awesome.

My one concern is the pillow blocks. Admittedly not familiar with these carts if that's a normal setup then ignore me, but I've had way more than my fair share of those castings break. From the 9.99 amazon ones to the 150 dollar ones from mcmaster with vibration the castings can crack.
I'm concerned about the direction of the force with them mounted that orientation , all the force is going into the shoulder of the casting which is where I've had them crack.

i assume it will likely be fine, but it looks like no suspension, (and vibration is what breaks them) combine that with a sudden impact like a pothole...
Pillow blocks are a common application for Formula SAE axles. Running 4 pillow blocks actually came recommended by the lead engineer of an IMSA race team, who happens to be the father of one of my crew guys. Granted, they CNC milled their own blocks. He ran two pillow blocks on their Virginia Tech SAE cars because of the suspension. These pillow blocks are self-aligning, so we have a little give locating them. If we do break one, then we go through the frame with the more common kart axle bearings.

These are the more common live axle bearings used in karts. Internally, the bearings are identical to the pillow blocks, so just the casting makes them different.



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