Help requested improving side dump mulch applicator

**jedidiahwiebe** · Jan 28, 2021, 12:58 AM

Hey All, I built this thing out of a small manure spreader a few years back. Really all I did was remove the beaters from the manure spreader and then bolt on a treadmill for the side dump conveyor. The unfortunate thing is I built this thing starting with a manure spreader that is ground driven. So this means that I am locked in to a particular speed of the apron chain (a kind of conveyor that pulls the wood chips to the back of the wagon). I would like to convert the drive mechanism of the apron chain to hydraulic drive, but I do not know how to select the right hydraulic motor size or rating. An older farmer stopped by today and said that he figured 20 or 30 hp would do the trick, but I don't know how many foot lbs torque rating to look for when buying a motor. How much do I need to gear it down to get the right speed? (very very slow!) What do I use for a speed controller? Do I even need to gear it down? Do hydraulic motors have all their torque at low rpm?

I had my wife take a video of the tool a few years back. Unfortunately no matter how hard I try I simply cannot seem to get her to keep the camera on the tool and off the scenery. This is the best I have got.

Thank you for any help hyraulic gurus! I wanna start building with hydraulic motor power!

**ibdennyak** · Jan 29, 2021, 07:00 AM

Look up the Surplus Center in Nebraska on the interwebs and download their catalog. In the hydraulics section they have the specs for torque, hp, gpm, and rpm to help des9ign your system. You will probably want a gerotor type motor....low rpm, high torque.

**jedidiahwiebe** · Jan 29, 2021, 05:25 PM

Thanks very much for your reply. The one thing I'm still wondering about is what would be about the right specs for the job? 5000 foot lbs torque? 50 thousand? What about the rpm? I'm thinking one or ten rpm... But if that even feasable? Do hydraulic motors even have enough torque at low rpm? Or is torque independent of rpm?

**ibdennyak** · Jan 30, 2021, 05:53 AM

Unfortunately, I would have to have the machine in front of me to give you numbers, but first we have to put things in perspective. I am going to guess that your spreader loaded weighs maybe 2000 lbs. it is ground drive, so it needs enough traction to drive the beaters and apron. Probably 75% of the power is used by the beaters. If your tractor develops 35 horsepower, the apron uses a small amount of that because it is also powering the beaters, pulling the spreader, and moving itself. If it were mine (ingenious use of an old spreader by the way), I would get about a 5 hp engine and a reduction gear of some kind and power it that way. That would give you a nice range of speed rather than being limited to one,,,,,,just throttle the engine up and down.

That would also help you design a hydraulic drive. A Predator 212 engine develops 6.5 hp at 3600 rpm and about 8 ft lb of torque at 2500 rpm. If you want to run your apron at 25 rpm, it would require 800 ft lb of torque with a 100 to 1 reduction gearbox.

I would suggest you have your lady count the revolutions' of you apron sprocket as you run the machine and start from there.

**jedidiahwiebe** · Feb 10, 2021, 11:39 PM

Ibdennyak Well... to be honest the small engine does sound like a pretty good idea. Probably would be a lot cheaper than installing rear remotes. on my tractor and then the hydraulic motor.

When you say that the small engine idea would give me a nice range of speed rather than being limited to one... is that to say that with hydraulic I would not have a nice range of speed? I do want a range of speed. And I want it easy to adjust from walking behind the tractor.

There are hydraulic motors with way more than 800 foot lbs of torque tho are there not?

**ibdennyak** · Feb 11, 2021, 03:44 AM

Yes, but at what rpm? A hydraulic motor with 800 ft/lb at 2000 rpm would probably be the size of a car engine. A hydraulic motor motor with 8 ft/lb at 2000 geared to 20 rpm will have the same 800 ft/lb but at 20 rpm.....closer to what you need, and you can hold the motor in your hand. Torque and rpm are inversely proportional. in your case the small one is what you want.

There are hydraulic motors with variable speed. They are called hydrostats. One source would be riding lawn mowers. If you can find about a 12 hp or so lawn tractor with an operational hydro, it and the differential would probably be about what you need. You would still need more reduction (sprocket and chain) but maybe only 3 ot 4 to one. The output torques goes up as the rpm goes down. The complication comes in that you need about 3000 rpm to drive it.

There are other ways to vary the rpm such as power dividers, but they become even more complicated to design. Another problem with hydraulics is heat. The motor and oil get pretty toasty under load.

You still need to find the output rpm of your apron you desire before you can design anything.

**jedidiahwiebe** · Feb 12, 2021, 11:37 AM

Okay, perfect. As soon as weather permits. Maybe even next week I shall fetch it from the shed in the back field and drive it around a bit and count the revolutions. And the feet per minute!

**jedidiahwiebe** · Feb 21, 2021, 11:38 PM

Alright I've done it. I have taken the side dumper out for a walk with my lady. I need the driveshaft on the apron chain to run at 2 rpm, but with some room for variability.

Also I totally get it. Here I thought I was reading 800-2900 foot lbs on the torque rating of these princess auto hydraulic motors but I was reading INCH LBS. Ooooooh kay. Gotcha. Lol

Now how do I figure out how much torque I'd need for this apron chain? The box on this spreader is about 3' wide and 10' long. And I can put about 3 yards of wood chips in it at a time. (REALLY high sides!) So that could be a weight of 1200-2400 lbs when full.

Thanks to anyone who can reply! Much appreciated.

**clavius** · Feb 22, 2021, 04:15 PM

For starters, that's a pretty clever setup you made. Nice bit of lateral thinking using a treadmill like that. I like it.

As to your question:

I am no expert on this stuff and have never built farm equipment, but just as a bit of a data point take a look at this spreader accessory for sanding icy roads:

https://www.fisherplows.com/products/poly-caster/

Depending on the model, one of those holds between 1.5 and 2.5 cubic yards of sand, at maybe 2000+ pounds/cubic yard. So maybe a bit more than your wood chips.

The whole thing is driven by two electric motors, one for the spinner that spreads the sand, and one for a bottom mounted conveyor that feeds the spreader. Both of those motors combined are powered via a 100A fuse. Assuming that it uses all of that 100 amps (which it obviously does not) that's consuming 1200 Watts of power, or in very round numbers, 1.6 HP total. Assuming no losses, 746W = 1 HP, and there are always losses. And, that is the total and is divided between the two motors. So less than 1.5 HP total to run the whole mess.

So while none of that directly answers your question, it would imply that if you had a 5 or 6HP small engine on there, you should easily have plenty of oomph to feed wood chips to your side conveyor, I think.

Just some food for thought.

Edited to add:

Rather than adding rear remotes to your tractor, maybe you could drive a separate hydraulic pump for your mulch spreader off the tractors PTO. A bit of added complexity, but requires no major alterations to the tractor. Just another option.

**jedidiahwiebe** · Feb 24, 2021, 12:23 PM

That's a really good data point. Thank you very kindly. I suppose it would be nice to take into account the coefficient of friction on that sand spreader machine vs the friction on my spreader. BUT your point is taken. Amazing! I guess if you lower the rpm of a motor by a factor of 1 or more thousands you must really increase the torque!!!

I am still having trouble deciding hydraulic vs small engine. What I really need to know is do hydraulic motors have the capability to run at lower rpms than a gasser? With a gasser I know I will need to run two 100:1 gear boxes. That's a few dollars. Now with a hydraulic I do not know... do they run at 20 rpm or 2000? Can any one tell me? Whilst the rear remotes on my tractor will cost some, and all the hydraulic lines... So will multiple gearboxes. Even the huge pulleys to reduce gearing cost a pretty penny. Is there anyone reading this that can shed light on hydraulics?
Thanks!