I'm making a post hole auger for my mini. I'm in the process of sizing the hydraulic motor. My aux hydraulic circuit has a max flow of 35 liters/min with a max pressure of 150 bar. The motor I'm looking at has a max flow input of 65 liters per minute and will turn at 160 max rpm. I figure that I'll at max flow, it will turn at 80-90rpm. The max continuous torque for this motor is 470 ft/lbs. I think this should work for boring 30cm holes in hard gravel/clay conditions. Does anybody see a problem with the low flow rate on my machine vs the higher max input on the hydraulic motor?
What is the displacement of the motor?
RPM is a function of hydraulic flow, torque is a funciton of hydraulic pressure. higher displacement = higher torque, slower rpm lower displacement = lower torque, higher rpm
Hyd motor RPM = (Flow/Displacement) * efficiency for example, if the motor displacement was 55cc: 35 liters/minute divided by 0.055 liters * .90 efficiency = 572.7 rotations per minute. Are you sure the numbers are correct? Could you confirm the ft./lbs? Torque? it should be lbf ft. anyway. But I think it may have been in lbf in. or oz. ft. Unless this is like a 400cc motor or I am totally wrong. For example, solving for displacement on you r motor, I see: 160r/min = 65Liters/min * 1/Xdisplacement (liters) * effciency.(lets say 0.8) X= 65liters minute/160 minute * 0.8 x= 0.325 liters diplacement or 325 cc
Haha! You're right on the money. It's a 400cc motor. Torque was listed as 34.8 daNm continuous.
Dang! that's a big motor!
if it is 400cc, then you have 98.5% volumetric efficiency rating. With that in mind, at 35 l/min you will get 86 RPM.
34.8 daNm is only 256.67 foot pounds of torque... where did you get he 470 ftlbs figure?
I can't find the link right now, but I found an online torque conversion table that had daNm listed equal to about 13.5 ft/lbs. 400cc's is the biggest motor that I could find. The torque is listed as MAX continuous torque so I read your volumetric efficiency rating as MAX efficiency. The actual efficiency is probably somewhat less. Now I've got to find an old output shaft or wheel hub assembly that I can cut down and use to support an 80 lb auger. I'm open to suggestions if anyone has recommendations for possible support bearing/output shaft donors.
Post hole auger flow rate: Here's a good one. http://www.duncanrogers.com/tools/conversion.asp#Torque Input 34.8 to the daNm box. You should get 256.672 from the ft.lbf box. Useful Tools page... http://www.duncanrogers.com/tools.asp Home Page... http://www.duncanrogers.com/ Good luck on your project... :thumbsup OCR
Great link OCR! Thanks!
Hey Joispoi, just want to remind you again that torque is in ft. lbs not ft/lbs ... the slash is a division sign and reads "ft per pound" which isn't a unit of torque. Sorry to nag you about it! "The actual efficiency is probably somewhat less." Perhaps... I don't know.
Nag! Nag! NAG!!! haha Thanks Huntoon. I'll be one slash mark less ignorant on my next post where I mention ft. lbs.
I finished the auger this weekend. I forgot to take pictures during the build, but here are a couple of pictures of the finished product: I adapted the hydraulic motor to the input shaft assembly of an old silage chopper. The auger is completely supported by the 2 bearings that were already in place - I had to cut back the seat for one of the races a couple of mm in order to clearance the hydraulic motor input and I had to resurface the plate to make a flat surface to fasten the motor to.
The welds are a little ugly because the arc welder that I have is old and as the thing vibrates, the amp adjustment knob turns and walks the power setting down. Once I figured out what was happening, I put a clamp on it to keep it from moving. The welds are also ugly because I'm the one who made them.
Cool!! Do you have any 'action' shots?
Coming soon. :usa
The welds look good from here:drinkup, Great build you got going there. I bet it will be more handy to use than on a skid steer. Its hard to tell from the pics, but will the auger swing right to left by a single pin?
The motor assembly doesn't swing, it connects directly to the quick hitch. To attach the auger to the motor, I made an adaptor using the u-joint off an old pto shaft. One end was already made to clamp directly to the splined output shaft. It hangs vertically even when the machine is on a sideslope. The mini has plenty of power to turn the auger. But, with the length of the auger, the boom needs to be all the way up and the dipper fully extended in order to keep the auger from dragging on the ground when tracking.
You could always cut the auger and make it shorter
I'm worried that I would have adequacy issues if I did that.
When I said "coming soon", I didn't think that it would be over a year later. Here are a few pics from a fence job. Going down Coming up Lifting the concrete panels into place with the PC50 and the panel clamp that I made.. The EC15 can lift them into place, but it's so much faster and easier this way. Here's a finished section. When the job is finished, over 27 tons of concrete fencing will be in place.