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jwatte , there is no other suspension, even with the Mule's weight of 320lb and the 280lb of sandbags addedQuote:
Does the axle nub that sticks out about 1.5" beyond the sprocket go into the bearing?
when plowing snow the bearing have held up for fours years.
all the failures happened at a turned down shoulder, the new design has no shoulders(1" keyed shaft the full length)
Attachment 6316
Mmmm, steel!
(Nice Bridgeport conversion, too!)
Are you using lead acid batteries for cost, or do they work better than lithium in cold weather?
(I imagine the batteries would warm themselves while running, though?)
jwatte, Using Lead acid Batteries for cost and weight, I have two commercial grade batteriesQuote:
Are you using lead acid batteries for cost
19"x 8"x 8" that give me about 100lb each, then five 60Ah deep cycle batteries that give me
about 60lb each. all but one of the batteries are configured for 24v for the drives, one deep cycle
battery is used for controls, cameras, and lights.
when this design is done(i'm very slow) it will have four commercial batteries and eight 60Ah batteries.
which should give it close to 1200lb of weigh on the four wheels. that should be enough to push my 50"
plow through 12" of snow.
Attachment 7140
going to have this type of setup(someday)
Attachment 7141
when I made the motor brackets, I made all four of them
Attachment 7142
Was there any particular reason for using the motor mounting plates as the central structural element of the new design? It would be much stronger and more reliable to replace the two short bars attaching the casters (and other two bars on the battery/plow side) to the motor mounts with longer, continuous bars extending the entire length of the bot and then mount everything to those bars. The battery holder and plow attachment section of the frame uses additional reinforcement to bolt to both ends of the motor mounting plates which helps a bit in distributing forces, but the casters just hang off the end of the motor mount plates with only one bolt per side. Making the casters cantilevered like that with the only bolt so close to the edge of the motor mounting plate will put a lot of stress on that area and risk the bolts being torn out of the motor mounting plate.
tician, the mule has multiple jobs to do, mowing grass,hauling stuff,plowing snow and collecting dead leaves. most of it's tasks can onlyQuote:
Was there any particular reason for using the motor mounting plates as the central structural element of the new design?
be done with two wheel drive(four wheel drive would tare up the lawn), the connecting bolts for the attachments are 1/2"-13 bolts.
Attachment 7143
the snow plow with the two front wheels is an attachment.
Attachment 7144
tician, the motor brackets are .625" hardened steel, and the bolts are 1/2"-13 grade 8.Quote:
risk the bolts being torn out of the motor mounting plate.
made blue chips when cutting the 1/2" holes at 300rpm in the brackets(very hard steel).
posted without refreshing:
What I was getting at is: three short bars bolted together at one or two points within a few thicknesses of their overlapping edges is much weaker than a single continuous bar. Even butt welding them together would be far superior to bolting like that. Extending the short bars under the entire length of the motor mounts so that bolts can be used at both ends will greatly reduce the stress experienced by the mounting plates, bars, and bolts. With just the one bolt connecting the caster bars at the end, the bolt is subjected to significant shear stress any time the bars are subjected to bending (batteries not properly balanced over pneumatic wheels, plow being forced upwards by ground/snow, extra weight added between casters and pneumatic wheels, etc.). With longer bars secured at both ends of the mounting plates, the bolts experience very little shear stress which makes them much less likely to fail or to tear out of the mounting plates or caster bars.
Imagine attaching two halves of a truck together with a short thick plate (<3" long) and just a couple bolts in the bottom flat of the frame rails located only an inch or so away from the joint - it will have essentially no resistance to bending and will very quickly tear the bolts out of the frame rail.
Using a much longer plate with regularly spaced bolts attaching up to a foot or so from the joint will greatly reduce the chance of the bolts shearing or tearing out, but does not help much in overall strength because of the small area moment of inertia of flat plate versus angle/channel/tube. Adding additional plate and bolts to the top flat of the frame rails significantly increases its strength and stiffness because the top and bottom are spaced by the height of the web to greatly increase the area moment of inertia.
tician, I wish I could apply the forces needed to cause the 1/2"-13 bolts to fail.Quote:
the bolts experience very little shear stress which makes them much less likely to fail or to tear out of the mounting plates or caster bars.