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Thread: 1000 : 1 speed reducer ?
11-03-2009, 05:38 PM #1
1000 : 1 speed reducer ?
yikes, I am laying out an overhead paint conveyor and the numbers work out to .223 RPM for the 48 inch drive wheel. So if I run a belt or chain from a 6 inch drive wheel, that works out to a 1000:1 speed reduction from a 1750 rpm motor. We are building two of these, so the reducer costs is going to add up. Does anyone have any ideas?
11-03-2009, 05:55 PM #2
What HP are we talking here? How bout a triple reduction gearbox? Or maybe a planetary gearbox? I suspect there are no cheap answers to your problem though. How bout AC motors at less than 1785? Maybe go DC instead of AC on the motor?
11-03-2009, 05:57 PM #3
Could use more info ......
but, could a large sprocket be put on the pulley shaft?
If so, then a small drive sprocket would give a large reduction
Could be chain or cogged belt.
Besides that, a 1100 rpm motor would help a lot on the input.
Provided the torque was met, a VFD on the motor with a single reducer should get close. Maybe up-size the motor to meet torque demands.
Just some quick thoughts
11-03-2009, 06:16 PM #4
Compound reduction, pair of high reduction worm gear boxes?
11-03-2009, 06:30 PM #5
From a junk yard engineering point of view:
Start with a surplus gear reduction motor, small pulley.
Belt to 24 inch pulley from junk air handler fan or back of commercial front loading washer on counter shaft.
Belt or chain from small pulley on other end of counter shaft to 48" bull wheel.
Sizes to be determined by amount of gear reduction.
1750 / 25 : 1 gear motor = 70 rpm.
6" pulley to 24" pulley = 17.5 rpm.
6" pulley to 48" pulley = 2.1875 rpm.
Ten times too fast, rockinghorsepoop!
Higher gear reduction on motor, 4" pulleys instead of 6", 3 phase motor & VFD. VFD would be nice, slow ramp up and down, and variable speed.
That is a "fun" one, good luck on the solution.
It would be nice to see a paint line drive system. I photographed one years ago for a client. Saw another in a Westinghouse plant near here. Slaughter houses and auto assembly lines use the same type of system.
11-03-2009, 07:18 PM #6
Very high reductions can be had with a differential drive. Two reduction drives at Very nearly the same ratio, driving a differnetial. The difference in the ratios is added in the differential.
Then there are epicyclical (sp?) drives..
There are a whole bunch of ideas for very high reduscion in that set of books...
"Ingenious Devices for Inventors and Engineers" But that book set was very seriously derided here once before already.
I think there a few ideas in the Charainis (sp?) book too.
11-03-2009, 07:53 PM #7
I think I have a gearbox that is about 1000:1. 56C motor size.
11-03-2009, 08:18 PM #8
A 1000:1 reduction is really three 10:1 reductions. I think you need to start with a 10:1 gear reducer with motor. This stage is where you would have the highest speed and wear issues. The geared reducer will solve a lot of issues like wear, noise, maintainance etc. Getting the rest of the drive train under 200 rpm will do wonders for longevity. The next 10:1 reduction would be nice if it were a belt and pulley arrangement. Good for speed and adds a little slippage to the system. The last 10:1 would be best as a chain setup because depending on size and load the chain would likely be the most effective and economical. The jack shaft could be as simple as two pillow blocks, and a shaft with a pulley on one side and sprocket on the other. Knowing the load would be very helpful.
Don't forget the proper guards, lock out devices, warning tags, disclaimers, flashing lights and baby blue paint.
Last edited by rjibosh; 11-04-2009 at 12:23 AM.
11-03-2009, 09:14 PM #9
The best I know of is 500:1.
It's only 1/4hp, but I dunno what you need. Here's a 500:1 for $80. You can either reduce the input or output 2:1, I'd reduce the input so it has a 2:1 belt arrangement.
11-03-2009, 10:30 PM #10
Why not get a large stepper motor and run it at whatever speed you want?, so long as it has a reasonable number of steps per revolution it shouldn't jerk too much, if it does jerk then use pulleys for a 10:1 reduction. A big surplus stepper should have all the power you need.
11-03-2009, 10:39 PM #11
You can also get a higher pole count motor so you start with a lot slower input to begin with.
11-04-2009, 12:11 AM #12
From experience of very slow moving conveyors;-
Some sort of overload clutch or shear pin device built in to the drive is all but essential, even a 1HP motor develops a lot of torque at high reductions and WILL do a lot of damage should a jam up etc occur.
EG 2HP bent & mangled 2 x 1 x 1/8" box section feeder bars like candy twist
11-04-2009, 05:35 AM #13
all good input, thanks. Yes this is a fun problem. I like the compound gear box train. HP? I have to figure that out. I don't thing alot is needed maybe 2 hp, this is a cable system with the paint hooks hanging off the cable and the cable is strung between shivs on posts, like a miniture ski lift. My thinking is that the sag of the cables act to keep the tension and thus friction on the drive wheel constant. The Total weight of the cable, hooks and product is only about 1000 lbs, so we are mostly dealing with friction and over coming the bending resistance of the cable. It looks like a 3/8 cable is plenty and will be pretty flexible.
Safety issues are important, we will need somesort of panic buttons, and maybe gates. Hopefully a pair of v belts running on the flat face of the 48 inch drive wheel will both have enough drag to drive and enough slip to act as a "gone to hell" over load.
11-04-2009, 06:21 AM #14
One way to do this type of drive is a combination of chain and hydraulic.
Wrap a small pitch roller chain, 1/4" or 3/8" is enough, around the head wheel to make it into a large 'gear'. Drive this with a small sprocket around 1-1/2" pitch diameter; this takes the necessary reduction down to 250 : 1. Because the speed is so slow the head wheel can just be a fabrication, it does not need to run particularly true, the sprocket can be mounted on a little swing arm and held into mesh by a spring. The sprocket is chain driven from a hydraulic motor; if a mutiple reduction chain drive is built it is fairly simple to get an overall ratio of 25 : 1 or more, in a compact package using 1/4" chain. This leaves a remaining reduction ratio of 10 : 1. The hydraulic pump is deliberately over-sized not because much torque is needed but because remaining reduction ratio is available by powering this motor with a very small pump. A pressure relief valve in the hydraulic system provides the overload safety and a flow control valve provides a fine tuning speed control.
11-04-2009, 06:30 AM #15
from 1750 rpm to .223 rpm is a ratio of 7847.5 roughly.
One 60:1 worm reducer will take 1750 to 29.16 rpm
A second 60:1 worm reducer off the first's output shaft will take 29.16 to .486 rpm.
A 2:1 sprocket reduction of the second reducer's output shaft will take .486 to .24 rpm (dern close to .223)
Reducers reduce speed but multiply torque by the same ratio less losses (efficiency)
If you start out with a 1750 rpm 1/2 HP motor, you will multiply its torque by 7847.5 (if reducer efficiency is 100% which it wont be - see below) giving theoretical output HP of roughly 3924 HP at .24 rpm. Now, as an estimate, each worm reducer may be 75% efficient as a guess-but check maker's specs re efficiency. So, to make an estimate:
first stage 60:1 from 1750 : .5 HP x 60 =30 HP at 100% eff
at 75% eff this leaves 22.5 HP output.
second stage input 22.5 HP x 60 =1350 HP at 100% eff
at 75% eff this leaves 1012.5 HP output
third stage 2:1 sprockets (say 50% efficient for old dirty rusted sprockets and chain)
1012.5 HP input x 2=2025 HP
at 50% efficiency this leaves 1012.5 HP on final shaft at .24 rpm.
(and lots of heat coming off the reducers)
Have a good day.
11-04-2009, 06:35 AM #16
11-04-2009, 01:49 PM #17
If you can find one, you might check the ratio on the gearbox off an old coal furnace stoker, the one that drives the feed auger. Don't know the ratio, but they were mighty slow.
11-04-2009, 03:28 PM #18
11-04-2009, 03:47 PM #19
Actually just two 90:1 gear boxes in series, and you will have .216 rpm from a 1750 rpm motor. using a VFD you can drive it at 62 hz if you really need to get the speed exact.
11-04-2009, 04:03 PM #20
If I did the math right, 1/2 hp at 1750 rpm is about 1.5 ft-lbf of torque. Multiply that by the reduction ratio and you get 11770 ft-lbf. That's a lot of torque. Its unlikely that you will find a 2nd stage gearbox that is rated 1/2 hp at .22 rpm. Of course, under normal conditions you won't be putting much load on the output shaft, but Limy Sami's advice should be heeded.