castle nut vs nylon lock nut
 

My 3202 and 3203 both have shaft/key/nylon nut. The 3206 has splined shaft/castle nut. Seems like the concept is the same for both axles, so why the castle nut on the 3206? Seems like I would have a tighter fit if I put a nylon nut on the 3206. What am I missing ? Why did the designers use a castle nut ?

1. A nylon lock nut should not be reused where the cotter pin of a castle nut should be reused.
2. A nylon lock nut can be used on any bolt where the castle nut will require a hole drilled closely to where the the nut will sit.

So no structural/functional reason I can't use a nylon nut, since in theory I don't need to remove it since the wheel can be taken off with lug nuts. I'd have a tighter fit, won't wear the splines down by a loose wheel, and like the 3202/3 take the hub off/on if I need to and reuse the nylon nut (even thought I'm not supposed to).

as far as re-use goes, once it gets to the point that you can hand thread it past the end of the bolt/nylock area, trash it. castle/cotters give guaranteed locking in position, which is why they are used on steering links and wheels by auto manufacturers. Don't ask me about the time i forgot to put the cotter back in the pitman on my firebird--right before a 300 mile trip. both of those uses also allow the nut to be tightened to spec then backed off to the nearest pin alignment without adverse affects.

ahhh, so maybe it is not good to have the hub tight on the splines? I can't image why that is a problem (back to my key comparison on the 3203). I just don't like the idea of not getting the hub tight on the axle and having some "slop". Seems like that will wear over time and fail. I remember seeing metalmans HD axle stripped out while reading through the posts a while back, which got me thinking about this.

Most axle uses of the castle nut were on tapered bearings/traditional spindle setups that need to have some play--and ball joints that you over tighten then can back off to align the cotter pin hole and still not have any play. modern strut suspensions mostly have gone to one-use crush nuts with a knock in ring that gets staked into a groove in the axle shaft and doesn't require adjusting the nut after tightening it.

With sealed wheel bearings like most of these karts use, you want the nut tightened right to the point of contact and no more or less. Engineering-wise, I don't think a whole lot of research goes into these things by the factories. Add in cost control by the accountants and one can see where little things get changed or used that aren't ideal for the application.

For your use, get nylock or crush nuts.

Thanks x-bird, seemed like it should not be problem, nice to have someone confirm. I've been known to miss the obvious.