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Bulldozer 01-26-2013 06:31:43 24.165.92.6 Report to Moderator	A simple material stress check of all the components of the front end on the N series shows the maximum stress occurs in the center axle part at about 2 1/2" from the vertical centerline. Since the part is sand cast steel, the allowable material strength is reduced compared to cold or hot rolled steel or forged steel. Doing the numbers based on the knee extension in the most narrow position, the front end is good for about only an extra 420# of static load. With a front end loader the extra weight of the steel frame, bucket and payload is bouncing, which creates a dynamic applied load rather than just a static applied load. Replacing the center axle with a 2" X 4" X 1/4" wall structural steel tube would increase the allowable dynamic working load to ~ 1475#. The gap in the center support weldment is 2 5/8". Believe the a 2 1/2" X 4" x 1/4" structual steel tube will fit. Using this size of member, the allowable dynamic working load would increase to ~ #1840. The center king pin has slightly more than 1" sq. in. of cross section. This part is far from the weak link, stress wise , but wear on this part causes undo stress on the radius rod, as witnessed from bent radius rods. A typical front end loader scoup holds ~ 1/2 CU YD volume. Some research indicates the weight of dry gravel is ~ 2835 #/ CU YD and maybe more depending on the water content. So, 1/2 CU YD weighs ~ 1417 # Based on the design of the front end loader, only some fraction of the loader weight and payload weight is taken by the front end axle. If 100% of the extra weight is taken up by the front axle, This would make the original N series tractor totally worthless to load gravel, maybe compost. If reto fitted with a 2" x 4" x 1/4" steel tube, would be marginal to load gravel If reto fitted with a 2-1/2" x 4" x 1/4" steel tube, might be acceptable to load gravel. [Reply]   [No Email]
TheOldHokie 01-26-2013 15:34:01 108.22.203.170 Report to Moderator	Re: why is the axle weak? in reply to Bulldozer, 01-26-2013 06:31:43   Bulldozer said: (quoted from post at 10:31:43 01/26/13) Replacing the center axle with a 2" X 4" X 1/4" wall structural steel tube would increase the allowable dynamic working load to ~ 1475#. The gap in the center support weldment is 2 5/8". Believe the a 2 1/2" X 4" x 1/4" structual steel tube will fit. Using this size of member, the allowable dynamic working load would increase to ~ #1840. If all you want to do is beef up the center axle why not use solid flat bar with approximately the same or even a slightly larger cross section as the cast axle? It can be easily bent to match the cast OEM axle and won't create a whole bunch of geometry problems. Unfortunately I don't think that would help much. In practice most of the loader induced damage does not occur in the axle member itself. The failures we commonly see are cracked oil pans, hogged out, bent, or broken axle supports, badly worn axle pins, bent radius rods, and/or damaged wheel bearings/bent spindles. Fractured center axles are rare. Damage to them is usually a badly hogged out center hole at the pivot point which can often be repaired with a sleeve. Exceeding the design loads on the front end causes excessive wear and damage to all of the components - not just the "axle". TOH This post was edited by TheOldHokie at 16:16:52 01/26/13 5 times. [Reply]  [No Email]
Bulldozer 01-26-2013 18:57:41 24.165.92.6 Report to Moderator	Re: why is the axle weak? in reply to TheOldHokie, 01-26-2013 15:34:01   Do not believe there is much wear to the axle. The wear occurs on the king pin and king pin bushing causing bending of the radius rod. The bushing and king pin should be on the maintenance list, since the load is applied as a single line load, which creates high contact stress on non hardened steel material and accelerates wear. Do not believe the axle is weak for the loads it was originally designed to handle and has ample safety margin. In my opinion the axle is under designed for front loader add on accessory. [Reply]  [No Email]
Dell (WA) 01-26-2013 14:59:33 174.24.216.80 Report to Moderator	Re: why is the axle weak? in reply to Bulldozer, 01-26-2013 06:31:43   Bulldozer........great analysis........Dell [Reply]  [No Email]