I finally put my new keyed axle and new bearings onto the buggy. I used the same axle ckau used, 42" keyed, drop down to 3/4". I planned on adding a second set of hangers but decided to just use the existing hangers for now.
I also picked up some Z400 rims for the rear although I am not happy with the current hub solution. Granted, it is all over-the-shelf, no fabricating. (It has an adapter). I'll post up some parts and pics later on. I have a lot I need to get onto this thread..
My problem - The axle is unbelievably bendy. If I apply pressure to both sides of the chain between the sprockets (causing the chain to pull more on the sprockets) I can watch the wheels move from the bowing/flex of the axle. I can set my chain tension to the point where there effectively is no slack and am still popping the chain off when conditions are right (under load, coming out of a hard right hand turn). I know ckau built "boxes", I honestly am debating trashing the entire thing and going with a 1.25" axle. I will find something to do with the other one eventually.
Still, I'm not sure 1.25" would be rigid enough.
Any other thoughts? I debated trying to add a bearing near the center of the axle but that would make it near impossible to get the engine out the swingarm. I'm curious how wide my "boxes" would have to be, if I could just add a hanger to the inside of the swingarm on both sides and that may be enough? I'm sick about this entire thing, I had the same chain-popping problem before the axle swap as well.
[edit]
I decided to try and add a center bearing since I already have the square tube across the bottom rear of the swingarm. I was working on getting it in place and realized that the axle was already warped. I pulled the axle out and stuck it on jack stands and a couple swings later have it nearly perfect. There's well under 1mm of movement at the sprocket so I'm going to use the current axle to place my center hanger and test function.
Axle straightening
Here is what I was about to weld in -
I honestly doubt this will be rigid enough, It may keep the axle flex down enough to keep the chain on but I'll likely end up with stress cracks at the welds over time (uneducated guess). I could always replace or beef up the square tubing pictured above.
More bearings and hangers are on order. The stock bearing ID is 1mm too small to use in the meantime.
[edit] I contacted Azusa, I asked what the difference was between their standard axle and the flex-proof. I also sent them this post and asked if they had any suggestions. Their reply -
Quote:
To address your questions: A 1" OD Flex-Pruf Axle or Standard Axle using 1" ID Insert Bearings, properly enclosed in flangettes (allowing the bearings to rotate under radial and axial loads) should perform well.
Both the tensile strengths and yield strengths on all Azusa axles are more than sufficient for the application. Flex-Pruf axles are higher strength than the standard steel, but the term "Flex" has nothing to do with its specifications.
It is simply an in-house marketing term used to differentiate between the two axle classes, and created because it did not infringe on any steel producers' brand or trademarked names.
The principal reason chains are thrown off is because of misalignment between the engine (clutch) sprocket and the axle sprocket. Both sprockets must be perpendicular to their shafts and lie in the same plane.
(A straight edge placed on the face of each sprocket would lie in a plane parallel to the center-line of the kart.)
All Azusa steel axles have comparable rigidity values. Although metals in general have a wide range of rigidity, the Modulus of Rigidity for all steels varies less than 8% - ranging from cast steel to high carbon heat-treated steels. Though Flex-Pruf axles are about 60% higher in both tensile strength (TS) and yield strength (YS), neither value is as important as mechanical design and weight distribution. Mounted on a standard kart frame the axles work fine. Your application may be pushing a 1" diameter axle to it's limits with the wide tires extending the length of unsupported axle beyond the frame bearing hangers.
Supporting the extended axle is one option (or) using a tubular 1-1/4" OD axle would be an alternative but would require a re-design.
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My sprockets are aligned at rest..