[Kartbuilding] wedling/racing cart

[Stephen Burke]

Hi Jakub,

Thanks for sending on the photos - they have raised a few points.
The sprocket you have (the black one). This is too large for use on the 
engine. Typically you are looking for a gear ratio of 5:1 minimum. 
Therefore you have a 10tooth sprocket on the engine, and a 50 toothed 
sprocket on the rear axle. Centrifugal clutches (which I recommend) come 
with the small 10toothed sprocket attached already.

As you mentioned in your email - YES - the chassis is the most important 
part of the gokart build. Everything else attaches to this chassis. Make 
sure you drill NO holes in the chassis, as this will only weaken it. 
Instead weld on lugs which can accept a bolt.

If you feel that you need to get the chassis professionally welded - fair 
enough. There will still be quite a few bits requiring small welding. The 
king-pings and steering will require small bits of welding.

Yes - the calliper you have seems to be manually operated and doesnt use 
any fluid. You will have to connect up some lever system which can accept 
a brake cable, so when you put your foot on the break, it pulls a cable, 
which operates the lever attached to the calliper.

Yes - the Pillow block bearing will work fine.
Yes - the Rose Rod End will do perfect.
The chain looks ok too, and you should not have any worries about it 
coming off.
The engine you have looks fine, and is pretty typical. It's output shaft 
does seem to protrude a few inches extra, but it should not affect the 
design too much.

As for attaching the rear wheels to the axle - do the wheels have a hub?
I chose to weld my metal hubs to the rear axle on one of my karts. It was 
a simple quick fix. I had an angle-grinder where I could grind off the 
weld to remove the wheels if necessary.
Ideally a hub with a keyway would be used. Something like your brake 
hub/mounting could also be used for the wheels. It would be possible to 
drill and grind out a keyway/slot in the rear axle and the inside hole of 
the hub etc. as can be seen on: 
http://www.kartbuilding.net/racingkart/Free_Racing_Kart_Plans_PDF/Main_Kart_Complete_06_Rear_Axle_Complete.pdf

Grub screws are only meant to stop a hub from moving from right to left, 
and would not be strong enough to transmit rotational power on a rear 
axle.

As your disc hub has no grub screw you have 2 options. You can take the 
quickest option and weld it to the rear axle, or if you are going the 
keyway route (which is much easier when you have to change sprocket or 
take off the wheels or bearings etc.) you can WELD two NUTS to the outside 
of the disc hub. Therefore when you put a bolt through these two nuts, it 
will tighten onto the rear axle and stop it from moving from left to 
right.
The shaft collars with a grub screw in each should do fine to stop the 
rear axle from moving from right to left. You can check for any movement 
when the kart is up and running.

In summary, set screws will not be enough to attach the rear wheels or 
sprocket or disc to the rear axle. Set screws will only stop lateral (side 
to side) movement of the components, e.g. the bearings.
KEYWAYS are the ideal method to keep the wheels, sprocket and brake disc 
from rotating with the rear axle. It is possible, using an angle grinder 
and an electric drill to make the keyway both in the rear axle, and on the 
inside hole of the hub and sprocket and brake disc.
The easiest way (although very crude) is to simply weld the wheels, 
sprocket and brake disc to the rear axle. This is the simplest and most 
effective way. NOTE: if you want to remove the sprocket or change the 
bearings etc. you will have to GRIND off all the welds!!
REMEMBER also - not to weld the bearing housings. Otherwise the ball 
bearings will expand and possibly break the housing, as well as melting 
the grease inside the bearing.

I hope this explains the rear axle a little for you. To do it properly - 
it is quite difficult! I found that a simple weld sufficed for me.

Best of Luck,
-steve


On Wed, 18 Jul 2007, Jakub Rogalewicz wrote:

> Thankyou for your quick reply. Sorry, I forgot to attach some photos. So I 
> attached some of the caliper and a few of some other components I have. I 
> already purchased 1" tubing with a 1/8" wall; thats more or less 3mm. since 
> the chassis is so important in the construction of the go cart, I was 
> thinking of getting it professionally welded together. I suppose I can 
> arcweld the pieces that will not take as much strain. As for the brake, I do 
> think that it is simply cable operated. I have looked over your site and read 
> everything atleast once so I feel I am fairly familiar with everything. In 
> the pictures you will see the pillow block bearing I am using to hold my 
> axle, the sprocket on the hub, the disc and moutning bracket, a rod end for 
> the steering, and the chain (ASA 40   1/2" pitch) so I think it will suffice. 
> Also included is the picture of the engine which is not as tall as yours but 
> is much wider and I need more space between me and the shaft. A few more 
> questions that I remembered are: How do I attach the rear wheels (rims/hubs) 
> to the rear axle? Do I permenatly weld them to the axle? Same goes for the 
> disc hub and the sprocket hub. The sprocket hub has a "set screw", so if I 
> tighten that will it be enough to stop the sprocket from moving left and 
> right? The disc hub does not have a set screw so I am assuming that I need to 
> weld it to the axle. As for the axle, will using shaft collars with set 
> screws be enough to hold the axle between the bearings so it doesnt slide? Or 
> do I need to weld the shaft collars onto the axle to keep it in place. I 
> understand that the front wheels are kept in place because you are able to 
> use a lock nut on the threaded piece of steel (or bolt with cut off head as I 
> have read on your site). But again I am confused about the rear, or could I 
> use those shaft collars and use the set screws on them to keep the rear 
> wheels in place, however somehow I feel that will not be strong enough.
>
> Thanks for your patience and sorry about all the questions, but I dont want 
> to kill myself riding this cart.
> Jakub
>